WATER-COOLING APPARATUS FOR ENGINE

Abstract

A water-cooling apparatus for cooling an engine includes a radiator for cooling coolant, a first flow passage connected with the engine, a second flow passage branched from the first flow passage and connected with the radiator, a third flow passage whose one end is connected with the radiator and whose another end is connected with the first flow passage at a downstream from the branched point of the second flow passage, a regulating valve on the first flow passage for regulating a flow volume of the coolant in the radiator, and a pump on the first flow passage for circulating the coolant through the engine and/or the radiator. The regulating valve is configured to flows the coolant from the radiator to the first flow passage when it is opened. The apparatus has a simple circulation flow path, and thereby appropriate cooling can be done by regulating the flow volume.

Description

TECHNICAL FIELD

The present invention relates to a water-cooling apparatus for an engine, especially to a water-cooling apparatus for an engine that controls cooling water by a pump and a regulating valve.

BACKGROUND ART

Well-known is a water-cooling apparatus for an engine that drives an engine-driven pump according to revolving speed of an internal combustion engine (hereinafter, referred merely as the engine) to circulate cooling water through a cylinder head and a cylinder block.

Since a flow volume of the cooling water is proportionate to the revolving speed of the engine in such a water-cooling apparatus, the flow volume of the cooling water may become excessively larger when the revolving speed becomes high under a cold condition or at high-speed running. Thus, warming-up may delay due to excessive heat radiation of the cooling water and a power loss may be subject to be brought. In addition, since the flow volume of the cooling water is proportionate to the revolving speed of the engine, knockings due to the cooling delay may occur when an engine load increases rapidly due to abrupt acceleration or the like.

In order to cool an engine according to an engine load, proposed is a water-cooling apparatus in which a bypass flow passage bypassing a radiator and a special pump for cooling combustion cylinders are provided (see Patent Document 1).

PRIOR ART DOCUMENT

Patent Documents

• Patent Document 1: Japanese Patent Application Laid-Open No. 2006-161606

SUMMARY OF INVENTION

However, in such a water-cooling apparatus, the number of parts may increase and flow passages for cooling water may become complicated. Therefore, an object of the present invention is to provide a water-cooling apparatus for an engine that has a simple circulation flow path of cooling water and can carry out appropriate cooling by regulating a flow volume of the cooling water flowing through the circulation flow path.

An aspect of the present invention provides a water-cooling apparatus for an engine that cools an internal combustion engine by cooling water, the apparatus comprising: a radiator that cools the cooling water by heat-exchanging between the cooling water and air; a first flow passage that flows the cooling water to the engine; a second flow passage that is branched from the first flow passage and flows the cooling water to the radiator; a third flow passage that flows the cooling water flowing from the radiator to the first flow passage at a downstream from a branched point of the second flow passage from the first flow passage; a regulating valve that is disposed on the first flow passage and regulates a flow volume of the cooling water flowing through the radiator; and a pump that is disposed on the first flow passage and circulates the cooling water through the engine and/or the radiator, wherein the regulating valve is configured to flows the cooling water flowing from the radiator to the first flow passage when opened.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 It is a schematic configuration diagram of a water-cooling apparatus for an engine according to a first embodiment.

FIG. 2 It is a schematic side view showing a layout of the engine.

FIG. 3 (a) is a graph showing relationship between cooling water temperature and combustion efficiency at a high load condition of the engine, and (b) is a graph showing relationship between cooling water temperature and combustion efficiency at a low load condition of the engine.

FIG. 4 It is a flowchart of a worm-up control of the water-cooling apparatus.

FIG. 5 It is a schematic diagram showing a flow of the cooling water in the warm-up control.

FIG. 6 (a) is a schematic perspective view showing natural convection of the cooling water in the water-cooled engine, and (b) is a schematic side view thereof.

FIG. 7 It is a flowchart of a normal control of the water-cooling apparatus.

FIG. 8 It is a schematic diagram showing flows of the cooling water in the normal control (under a low load condition).

FIG. 9 It is a schematic diagram (2) showing flows of the cooling water in the normal control (under a high load condition).

FIG. 10 It is a schematic configuration diagram of a water-cooling apparatus for an engine according to a modified example of the first embodiment.

FIG. 11 It is a schematic diagram showing a flow of cooling water in a warm-up control in the water-cooling apparatus.

FIG. 12 It is a schematic diagram showing flows of the cooling water in a normal control (under a low load condition) in the water-cooling apparatus.

FIG. 13 It is a schematic diagram showing flows of the cooling water in a normal control (under a high load condition) in the water-cooling apparatus.

FIG. 14 It is a schematic configuration diagram of a water-cooling apparatus for an engine according to a second embodiment.

FIG. 15 It is a flowchart of a worm-up control of the water-cooling apparatus.

FIG. 16 It is a schematic diagram showing a flow of cooling water in the warm-up control.

FIG. 17 It is a flowchart of a normal control of the water-cooling apparatus.

FIG. 18 It is a schematic diagram showing flows of the cooling water in the normal control (under a low load condition) in the water-cooling apparatus.

FIG. 19 It is a schematic configuration diagram of a water-cooling apparatus for an engine according to a modified example of the second embodiment.

FIG. 20 It is a schematic diagram showing a flow of cooling water in a warm-up control in the water-cooling apparatus.

FIG. 21 It is a schematic diagram showing flows of the cooling water in a normal control (under a low load condition) in the water-cooling apparatus.

FIG. 22 It is a schematic configuration diagram of a water-cooling apparatus for an engine according to a third embodiment.

FIG. 23 It is a flowchart of a worm-up control of the water-cooling apparatus.

FIG. 24 It is a schematic diagram showing flows of cooling water in the warm-up control.

FIG. 25 It is a flowchart of a normal control of the water-cooling apparatus.

FIG. 26 It is a schematic diagram showing flows of the cooling water in the normal control (under a low load condition).

FIG. 27 It is a schematic configuration diagram of a water-cooling apparatus for an engine according to a modified example of the third embodiment.

FIG. 28 It is a schematic diagram showing flows of cooling water in a warm-up control in the water-cooling apparatus.

FIG. 29 It is a schematic diagram showing flows of the cooling water in a normal control (under a low load condition) in the water-cooling apparatus.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments will be explained with reference to the drawings. In the drawings, identical or equivalent components to each other are labeled with identical reference numbers, respectively. Note that the drawings are shown schematically, and dimensions and proportions of the components in the drawings are not shown precisely but actual dimensions and proportions of the components should be understood in consideration of following explanations. In addition, dimensions and proportions of the components may be shown differently among the drawings.

First Embodiment

As shown in FIG. 1, a water-cooling apparatus 1a according to a first embodiment cools a water-cooled internal combustion engine (hereinafter, referred merely as the engine) 2 by using cooling water (coolant). The water-cooling apparatus 1a includes a radiator 3, a first flow passage 31, a second flow passage 30, a third flow passage 32, a regulating valve 11, and a pump 10. In the radiator 3, heats are exchanged between the cooling water of the engine 2 and air, and thereby the cooling water is cooled. The first flow passage 31 is disposed on a circulation flow path of the cooling water and on an upstream side from the engine 2 to flow the cooling water into the engine 2. The second flow passage 30 is disposed on the circulation flow path and on an upstream side from the radiator 3 to flow the cooling water into the radiator 3. The third flow passage 32 is disposed on the circulation flow path and on a downstream side from the radiator 3 to flow the cooling water from the radiator 3 to the first flow passage 31.

The regulating valve 11 is disposed on the first flow passage 31 to regulate a flow volume of the cooling water flowing through the engine 2 and/or the radiator 3. The pump 10 is disposed also on the first flow passage 31 (on a downstream side from the regulating valve 11) to circulate the cooling water along the circulation flow path. An upstream end of the second flow passage 30 is connected with the first flow passage 31 (the regulating valve 11), and a downstream end thereof is connected with the radiator 3. An upstream end of the third flow passage 32 is connected with the radiator 3, and a downstream end thereof is connected with the first flow passage 31. When the regulating valve 11 is opened, the cooling water flows into the first flow passage 31 through the second flow passage 30, radiator 3 and the third flow passage 32.

As shown in FIG. 2, the engine 2 is inclined with its exhaust side faced downward. Since the exhaust side of the engine 2 is faced downward, the cooling water flows toward its intake side (upward) due to natural convection when the pump 10 is stopped. Therefore, even when the pump 10 is stopped, due to natural convection, temperature of the cooling water near a cylinder head can be homogenized and the cooling water can be circulated thorough the radiator 3. It is preferable that the inclination α(°) of the engine 2 is set to almost 20° in view of natural convention of the cooling water. Note that, when an inclination of center axes of combustion cylinders of the engine 2 with respect to the horizontal direction is denoted as β(°), α=90°−β.

The engine 2 is cooled by the cooling water from the first flow passage 31, and then the cooling water flows out to a fourth flow passage 20. A temperature sensor (not shown) is disposed on the fourth flow passage 20. The temperature sensor detects temperature of the cooling water flowing out from the engine 2 (i.e. in the engine 2). Detected data by the temperature sensor are output to a controller (not shown).

Combustion efficiency that depends on the temperature of the cooling water of the engine 2 will be explained with reference to graphs shown in FIG. 3 (a) and (b). When a load applied to the engine 2 (here, the load is indicated by Indicated Mean Effective Pressure: IMEP) is low (low load: 300 kPa), the combustion efficiency (here, the combustion efficiency is indicated by indicated thermal efficiency) is better with high temperature of the cooling water, e.g. 100° C. (second temperature), as shown in FIG. 3 (a). On the other hand, when a load applied to the engine 2 is high (high load: 900 kPa), the combustion efficiency is better with low temperature of the cooling water, e.g. 80° C. (first temperature), as shown in FIG. 3 (b).

The radiator 3 is a device for radiating heats of the engine 2 by intermediary of the cooling water, and has a structure in which many tubes each of which has fins and is made of aluminum alloy or the like are aligned. A flow-in side of the radiator 3 is connected with the downstream end of the second flow passage 30, and a flow-out side thereof is connected with the upstream end of the third flow passage 32.

A heater core 4 is disposed on a downstream side from the fourth flow passage 20 on the circulation flow path of the cooling water, and its flow-out side is connected with the pump 10 by a fifth flow passage 22. An electromagnetic valve 25 for regulating a flow volume of the cooling water is disposed on the fourth flow passage 20 on an upstream side from the heater core 4. A flow volume of the cooling water flowing through the heater core 4 is regulated by adjusting a valve opening position of the electromagnetic valve 25 to adjust a heat radiation amount at the heater core 4. As a result, the temperature of the cooling water is also adjusted. The heater core 4 heats air by heat-exchanging between the cooling water heated by the engine 2 and the air. The heated air is utilized for air-conditioning and so on.

Further, a sixth flow passage 24 bypassing the heater core 4 is also provided. An upstream end of the sixth flow passage 24 is connected with the fourth flow passage 20 on an upstream side from the heater core 4, and a downstream end thereof is connected with the fifth flow passage 22. When the electromagnetic valve 25 is closed, the cooling water flows thorough the sixth flow passage 24 to bypass the heater core 4.

The pump 10 in the present embodiment is an electrical pump P₁ operable independently from operations of the engine 2. The pump 10 (electrical pump P₁) controls a flow volume of the cooling water based on a signal from the controller (not shown).

The regulating valve 11 is disposed on the first flow passage and on a downstream side from the pump 10. The second flow passage 30 is branched from the regulating valve 11. The regulating valve 11 is a three-way valve for flowing the cooling water from the pump 10 to the engine 2 and/or the second flow passage 30. The regulating valve 11 is an electrically-controlled thermostat, and controls, with respect to the cooling water from the pump 10, a flow volume of the cooling water flown to the engine 2 and/or the radiator 3 based on a signal from the controller (not shown). The regulating valve 11 in the present embodiment controls a flow volume of the cooling water to be flown to the radiator 3 at an upstream from the radiator 3.

Hereinafter, a warm-up control of the engine 2 by the water-cooling apparatus 1a will be explained with reference to a flowchart shown in FIG. 4.

First, it is judged whether or not temperature of the cooling water detected by the temperature sensor is equal-to or lower-than the first temperature (80° C.) as a reference index for completion of warming-up (step S10). If the temperature of the cooling water is higher than the first temperature (80° C.) (NO in step S10), it transitions to a normal control to be carried out after the worm-up control (step S30), and the worm-up control is ended. The normal control will be explained later in detail. On the other hand, if the temperature of the cooling water is equal-to or higher-than the first temperature (80° C.) (YES in step S10), it is judged whether or not a heater switch of an air-conditioner is turned on (step S11).

If the heater switch is not turned on (NO in step S11), the controller sends control signals for making the temperature of the cooling water higher than the first temperature (80° C.) quickly to the pump 10, the regulating valve 11 and the electromagnetic valve 25. Here, since the heater switch is turned off, it is not needed to flow the cooling water to the heater core 4. Therefore, the electromagnetic valve 25 on the upstream side from the heater core 4 is closed based on the control signal from the controller (step S12). Further, the second flow passage 30 is also closed by the regulating valve as shown in FIG. 5 (after-explained step S14), and thereby the cooling water is not flown to the radiator 3. Thus, heats are not radiated at the radiator 3 and the heater core 4, and thereby temperature of the cooling water is made higher than the first temperature (80° C.) quickly.

Subsequent to the step S12, the pump 10 (the electrical pump P₁) is stopped based on the control signal from the controller to stop supplying the cooling water to the engine 2 (step S13). Since the engine 2 is inclined as shown in FIG. 6(a) and (b), the cooling water flows due to natural convection even when the pump 10 is stopped. Therefore, without forcibly circulating the cooling water by the pump 10, the cooling water circulates in the water-cooling apparatus 1a due to natural convection. But, according to this, temperature of the cooling water in the engine 2 is raised quickly to suitable temperature for heat efficiency due to absorption of heats of the engine 2.

Subsequent to the step S13, the regulating valve 11 closes the second flow passage 30 (at its upstream end) based on the control signal from the controller (step S14). Heats are not radiated at the radiator 3 due to the closure of the second flow passage 30, and thereby the temperature of the cooling water can be prevented from reducing during the warm-up control. After the step S14, the process flow is returned to the step S10, and then it transitions to the normal control (step S30) when the temperature of the cooling water becomes higher than the first temperature (80° C.) (NO in step S10).

On the other hand, if the heater switch is turned on in the step S11 (YES in step S11), the electromagnetic valve 25 on the upstream side from the heater core 4 is controlled to flow the cooling water to the heater core 4 for air-heating. Specifically, a valve opening position of the electromagnetic valve 25 is set so as to flow the cooling water to the heater core 4 by 10 L/min based on the control signal from the controller (step S20).

Subsequent to the step S20, also a discharge volume of the pump 10 is also controlled so as to flow the cooling water to the heater core 4 by 10 L/min based on the control signal from the controller (step S21). Here, since natural convection also occurs due to the inclination of the engine 2 shown in FIG. 6(a) and (b), energy required for driving the pump 10 can be reduced. Namely, the flow volume 10 L/min of the cooling water is achieved by the valve opening position of the electromagnetic valve 25 and the discharge volume of the pump 10.

Subsequent to the step S21, the regulating valve 11 closes the second flow passage 30 based on the control signal from the controller (step S22). Heats are not radiated at the radiator 3 due to the closure of the second flow passage 30, and thereby the temperature of the cooling water can be prevented from reducing during the warm-up control. Although heats are radiated at the heater core 4 for air-heating, heats are not radiated at the radiator 3 and thereby the temperature of the cooling water will become higher than the first temperature (80° C.) quickly. After the step S22, the process flow is returned to the step S10, and then it transitions to the normal control (step S30) when the temperature of the cooling water becomes higher than the first temperature (80° C.) (NO in step S10).

Next, a normal control of the engine 2 (after the warm-up control) by the water-cooling apparatus 1a will be explained with reference to a flowchart shown in FIG. 7.

First, it is judged whether or not the engine 2 is idled (step S110). If it is not idled (NO in step S110), it is judged whether or not a change of a throttle position is small in order to estimate an operation state of the engine 2 (step S111). The throttle position is a valve opening position of a throttle valve that is disposed on an intake air passage of the engine 2 to regulate an intake air volume (note that, in a case of an engine having an intake air volume control mechanism without a throttle valve, the change of a throttle position may mean a change of an intake air volume parameter). A case where the change of a throttle position is small is a steady state such as constant-speed running or the like, i.e. a case where the engine 2 is operated with a low load. On the other hand, a case where the change of a throttle position is large is a transient state such as accelerating running, hill-climbing running or the like, i.e. a case where the engine 2 is operated with a high load.

If the change of a throttle position is small (smaller than a predetermined change of an opening position), i.e. the engine 2 is in a low-load state (YES in step S111), the controller sends control signals for regulating the temperature of the cooling water to be the second temperature (100° C.) to the pump 10, the regulating valve 11 and the electromagnetic valve 25. Since, in a low-load state of the engine 2, fuel efficiency is better when the temperature of the cooling water is the second temperature (100° C.) higher than the first temperature (80° C.) as shown in FIG. 3(a), the temperature of the cooling water is regulated to be the second temperature (100° C.).

Specifically, since the worming-up is completed, the electromagnetic valve 25 is opened based on the control signal from the controller to circulate the cooling water through the heater core 4 (step S112). According to this, an air-conditioner can use heats of the heater core 4 at any time. Note that, since it is in a low-load state with no change of a throttle position when idled in the step S110 (YES in step S110), the process flow proceeds to the step S112 without the judgment of the step S111.

Subsequent to the step S112, the pump 10 (the electrical pump P₁) circulates the cooling water based on the control signal from the controller, but its flow volume is controlled to be small (step S113). Heat radiation at the heater core 4 and the radiator 3 is restricted by making the flow volume small, and thereby the temperature of the cooling water rises and becomes the second temperature (100° C.) (a flow of the cooling water to the radiator 3 will be explained in a next step S114).

Subsequent to the step S113, a valve opening position of the regulating valve 11 is adjusted based on the control signal from the controller to adjust a flow volume of the cooling water flowing through the radiator 3 at the upstream end of the second flow passage 30 (step S114). In order to regulate the temperature of the cooling water to be the second temperature (100° C.) by restricting heat radiation at the radiator 3, a flow volume to the second flow passage 30, the radiator 3 and the third flow passage 32 is made relatively small (see FIG. 8). Note that the regulating valve 11 also flows the cooling water from the pump 10 to the engine 2.

On the other hand, if the change of a throttle position is large (larger than the predetermined change of an opening position), i.e. the engine 2 is in a high-load state (NO in step S111), the controller sends control signals for regulating the temperature of the cooling water to be the first temperature (80° C.) to the pump 10, the regulating valve 11 and the electromagnetic valve 25. Since, in a high-load state of the engine 2, fuel efficiency is better when the temperature of the cooling water is the first temperature (80° C.) lower than the second temperature (100° C.) as shown in FIG. 3(b), the temperature of the cooling water is regulated to be the first temperature (80° C.).

Specifically, similarly to the above-explained step S112, since the worming-up is completed, the electromagnetic valve 25 is opened based on the control signal from the controller to circulate the cooling water through the heater core 4 (step S120). Subsequent to the step S120, the pump 10 (the electrical pump P₁) circulates the cooling water based on the control signal from the controller, but its flow volume is controlled to be large (step S121). Heat radiation at the radiator 3 is promoted by making the flow volume large, and thereby the temperature of the cooling water is restricted from rising and kept at the first temperature (80° C.) (a flow of the cooling water to the radiator 3 will be explained in a next step S122).

Subsequent to the step S121, a valve opening position of the regulating valve 11 is adjusted based on the control signal from the controller to close a flow path to the first flow passage 31 connected with the engine 2 and to fully-open a valve opening position of the upstream end of the second flow passage 30 (step S122), and thereby the cooling water is flown only to the second flow passage 30, the radiator 3 and the third flow passage 32 (see FIG. 9). In order to regulate the temperature of the cooling water to be the first temperature (80° C.) by promoting heat radiation at the radiator 3, a flow volume to the second flow passage 30, the radiator 3 and the third flow passage 32 is made large. The cooling water flows through the second flow passage 30, the radiator 3 and the third flow passage 32, and then flows into the engine 2. Thus, the heat radiation at the radiator 3 is promoted, and thereby the temperature of the cooling water is reduced to become the first temperature (80° C.).

According to the water-cooling apparatus 1a in the present embodiment, since the third flow passage 32 for flowing the cooling water out from the radiator 3 to the engine 2, the temperature control and the flow volume control of the cooling water can be easily done without increasing the number of parts and without complicating the flow passages of the cooling water.

Further, the third flow passage 32 in a low-load state (see FIG. 8) is filled with the cooling water at about 60° C. that is cooled at the radiator 3. Here, when the cooling water is crammed into the radiator 3 thorough the second flow passage 30 by the regulating valve 11, the cooling water in the third flow passage 32 flows into the engine 2 after becoming confluent with the cooling water in the first flow passage 31 because water is incompressible fluid. Therefore, when a flow volume to the second flow passage 30 is increased by the regulating valve 11 at transition from a low-load state to a high-load state such as abrupt acceleration (FIG. 8 to FIG. 9), the cooling water at about 60° C. in the third flow passage 32 is made confluent with the cooling water in the first flow passage 31 and then the cooling water flows into the engine 2. As a result, it becomes possible to change the temperature of the cooling water instantaneously from the second temperature (100° C.) for a low-load state to the first temperature (80° C.) for a high-load state. In a low-load state, fuel consumption can be improved by about 3% by regulating the cooling water to be the second temperature (100° C.) that brings good combustion efficiency. Furthermore, it becomes possible to prevent knockings in a high-load state (accelerating running) by quickly reducing the temperature of the cooling water to the first temperature (80° C.).

Modified Example of First Embodiment

As shown in FIG. 10, a position of a regulating valve 11 in a water-cooling apparatus 1a′ for an engine according to a modified example of the first embodiment is different from that in the water-cooling apparatus 1a according to the first embodiment (see FIG. 1). Since other configurations of the water-cooling apparatus 1a′ in the present modified example are identical to those of the water-cooling apparatus 1a according to the first embodiment, their redundant explanations will be omitted.

The regulating valve 11 in the present modified example is also a three-way disposed on the first flow passage and on a downstream side from the pump 10. But, whereas the regulating valve 11 in the first embodiment is disposed at a branch point of the second flow passage 30 on the first flow passage 31, the regulating valve 11 in the present modified example is disposed at a confluent point of the third flow passage 32 on the first flow passage 31. The regulating valve 11 is an electrically-controlled thermostat, and controls a flow volume of the cooling water to be flown to the to the engine 2 and/or the radiator 3 based on the signals from the controller (not shown) by controlling a mixture rate of the cooling water from the pump 10 and the cooling water from the third flow passage 32. The regulating valve 11 in the present modified example controls a flow volume of the cooling water to be flown to the radiator 3 at a downstream from the radiator 3.

A warm-up control of the engine 2 by the water-cooling apparatus 1a′ is different from the warm-up control in the first embodiment in the processes of the steps S14 and S22 (see FIG. 4) that relate to the regulating valve 11. Since a whole of the warm-up control is carried out in line with the flowchart shown in FIG. 4 also in the present modified example, only the different steps S14 and S22 will be explained hereinafter.

In the step S14, the temperature of the cooling water is equal-to or lower-than the first temperature (80° C.) (YES in step S10) and the heater switch is turned off (NO in step S11). Therefore, heats are not radiated at the radiator 3 and the heater core 4, and thereby the cooling water is made higher than the first temperature (80° C.) quickly. Namely, as shown in FIG. 11, the electromagnetic valve 25 is closed (step S12) and the pump 10 is stopped (step S13). Further, the regulating valve 11 closes the third flow passage 32 (at its downstream end) based on the control signal from the controller (step S14).

On the other hand, in the step S22, the temperature of the cooling water is equal-to or lower-than the first temperature (80° C.) (YES in step S10) and the heater switch is turned on (YES in step S11). Therefore, heats are not radiated at the radiator 3, and thereby the cooling water is made higher than the first temperature (80° C.) quickly. Namely, the electromagnetic valve 25 is opened (step S20: to radiates heats at the heater core 4 because the heater switch is turned on) and the pump 10 is driven (step S21). Further, the regulating valve 11 closes the third flow passage 32 (at its downstream end) based on the control signal from the controller (step S22).

A normal control (after the warm-up control) by the water-cooling apparatus 1a′ is different from the normal control in the first embodiment in the processes of the steps S114 and S122 (see FIG. 7) that relate to the regulating valve 11. Since a whole of the normal control is carried out in line with the flowchart shown in FIG. 7 also in the present modified example, only the different steps S114 and S122 will be explained hereinafter.

In the step S114, since the engine 2 is idled (YES in step S110) or the change of a throttle position is small (YES in step S111), the engine 2 is in a low-load state. Therefore, the pump 10 is controlled so that a flow volume of the cooling water becomes small (step S113) to restrict heat radiation at the heater core 4 and the radiator 3, and thereby the temperature of the cooling water is raised to the second temperature (100°). In addition, a valve opening position of the regulating valve 11 is adjusted based on the control signal from the controller, and thereby a flow volume of the cooling water flowing through the radiator 3 is adjusted at the downstream end of the third flow passage 32 (step S114). In order to regulate the temperature of the cooling water to be the second temperature (100° C.) by restricting heat radiation at the radiator 3, a flow volume to the second flow passage 30, the radiator 3 and the third flow passage 32 is made relatively small (see FIG. 12). Note that the regulating valve 11 also flows the cooling water from the pump 10 to the engine 2.

On the other hand, in the step S122, since the change of a throttle position is large (NO in step S111), the engine 2 is in a high-load state. Therefore, the pump 10 is controlled so that a flow volume of the cooling water becomes large (step S121) to promote heat radiation at the heater core 4 and the radiator 3, and thereby the temperature of the cooling water is regulated to be the first temperature (80°). Namely, a valve opening position of the regulating valve 11 is adjusted based on the control signal from the controller to close a flow path from the first flow passage 31 and to fully-open a valve opening position of the downstream end of the third flow passage 32 (step S122), and thereby the cooling water is flown only to the second flow passage 30, the radiator 3 and the third flow passage 32 (see FIG. 13).

Advantages equivalent to those brought by the water-cooling apparatus 1a in the first embodiment can be also brought by the water-cooling apparatus 1a′ in the present modified example that is configures as explained above.

Second Embodiment

As shown in FIG. 14, a water-cooling apparatus 1b for an engine according to a second embodiment has a configuration in which the pump 10 (the electrical water pump P₁) of the water-cooling apparatus 1a in the first embodiment (see FIG. 1) is replaced with a pump 12 (an engine-driven pump P₂) driven by the engine 2. Therefore, according to the pump 12 in the present embodiment, a flow volume of the cooling water varies along with an engine revolving speed. Since other configurations of the water-cooling apparatus 1b in the present embodiment are identical to those of the water-cooling apparatus 1a in the first embodiment, their redundant explanations will be omitted.

Hereinafter, a warm-up control of the engine 2 by the water-cooling apparatus 1b will be explained with reference to a flowchart shown in FIG. 15.

First, it is judged whether or not temperature of the cooling water detected by the temperature sensor is equal-to or lower-than the first temperature (80° C.) as a reference index for completion of warming-up (step S10). If the temperature of the cooling water is higher than the first temperature (80° C.) (NO in step S10), it transitions to a normal control to be carried out after the worm-up control (step S30), and the worm-up control is ended. The normal control will be explained later in detail. On the other hand, if the temperature of the cooling water is equal-to or lower-than the first temperature (80° C.) (YES in step S10), it is judged whether or not a heater switch of an air-conditioner is turned on (step S11).

If the heater switch is not turned on (NO in step S11), the controller sends control signals for making the temperature of the cooling water higher than the first temperature (80° C.) quickly to the regulating valve 11 and the electromagnetic valve 25. Here, since the heater switch is turned off, it is not needed to flow the cooling water to the heater core 4. Therefore, the electromagnetic valve 25 on the upstream side from the heater core 4 is closed based on the control signal from the controller (step S12). Further, the second flow passage 30 is also closed by the regulating valve 11 as shown in FIG. 16 (after-explained step S14), and thereby the cooling water is not flown to the radiator 3. Thus, heats are not radiated at the radiator 3 and the heater core 4, and thereby temperature of the cooling water is made higher than the first temperature (80° C.) quickly.

Subsequent to the step S12, the regulating valve 11 closes the second flow passage 30 (at its upstream end) based on the control signal from the controller (step S14). Heats are not radiated at the radiator 3 due to the closure of the second flow passage 30, and thereby the temperature of the cooling water can be prevented from reducing during the warm-up control. After the step S14, the process flow is returned to the step S10, and then it transitions to the normal control (step S30) when the temperature of the cooling water becomes higher than the first temperature (80° C.) (NO in step S10).

On the other hand, if the heater switch is turned on in the step S11 (YES in step S11), the electromagnetic valve 25 on the upstream side from the heater core 4 is controlled to flow the cooling water to the heater core 4 for air-heating. Specifically, a valve opening position of the electromagnetic valve 25 is set so as to flow the cooling water to the heater core 4 by 10 L/min based on the control signal from the controller (step S20).

Subsequent to the step S20, the regulating valve 11 closes the second flow passage 30 based on the control signal from the controller (step S22). Heats are not radiated at the radiator 3 due to the closure of the second flow passage 30, and thereby the temperature of the cooling water can be prevented from reducing during the warm-up control. Although heats are radiated at the heater core 4 for air-heating, heats are not radiated at the radiator 3 and thereby the temperature of the cooling water will become higher than the first temperature (80° C.) quickly. After the step S22, the process flow is returned to the step S10, and then it transitions to the normal control (step S30) when the temperature of the cooling water becomes higher than the first temperature (80° C.) (NO in step S10).

Next, a normal control of the engine 2 (after the warm-up control) by the water-cooling apparatus 1b will be explained with reference to a flowchart shown in FIG. 17.

First, it is judged whether or not the engine 2 is idled (step S110). If it is not idled (NO in step S110), it is judged whether or not a change of a throttle position is small in order to estimate an operation state of the engine 2 (step S111).

If the change of a throttle position is small, i.e. the engine 2 is in a low-load state (YES in step S111), the controller sends control signals for regulating the temperature of the cooling water to be the second temperature (100° C.) to the regulating valve 11 and the electromagnetic valve 25. Since, in a low-load state of the engine 2, fuel efficiency is better when the temperature of the cooling water is the second temperature (100° C.) higher than the first temperature (80° C.) as shown in FIG. 3 (a), the temperature of the cooling water is regulated to be the second temperature (100° C.).

Specifically, since the worming-up is completed, the electromagnetic valve 25 is opened based on the control signal from the controller to circulate the cooling water through the heater core 4 (step S112). According to this, an air-conditioner can use heats of the heater core 4 at any time. Note that, since it is in a low-load state with no change of a throttle position when idled in the step S110 (YES in step S110), the process flow proceeds to the step S112 without the judgment of the step S111.

Subsequent to the step S112, a valve opening position of the regulating valve 11 is adjusted based on the control signal from the controller to adjust a flow volume of the cooling water flowing through the radiator 3 at the upstream end of the second flow passage 30 (step S114). In order to regulate the temperature of the cooling water to be the second temperature (100° C.) by restricting heat radiation at the radiator 3, a flow volume to the second flow passage 30, the radiator 3 and the third flow passage 32 is made relatively small (see FIG. 18). Note that the regulating valve 11 also flows the cooling water from the pump 12 to the engine 2.

On the other hand, if the change of a throttle position is large, i.e. the engine 2 is in a high-load state (NO in step S111), the controller sends control signals for regulating the temperature of the cooling water to be the first temperature (80° C.) to the regulating valve 11 and the electromagnetic valve 25. Since, in a high-load state of the engine 2, fuel efficiency is better when the temperature of the cooling water is the first temperature (80° C.) lower than the second temperature (100° C.) as shown in FIG. 3(b), the temperature of the cooling water is regulated to be the first temperature (80° C.).

Specifically, similarly to the above-explained step S112, since the worming-up is completed, the electromagnetic valve 25 is opened based on the control signal from the controller to circulate the cooling water through the heater core 4 (step S120). Subsequent to the step S120, a valve opening position of the regulating valve 11 is adjusted based on the control signal from the controller to close a flow path to the first flow passage 31 connected with the engine 2 and to fully-open a valve opening position of the upstream end of the second flow passage 30 (step S122), and thereby the cooling water is flown only to the second flow passage 30, the radiator 3 and the third flow passage 32 (similar to FIG. 9: however, not the pump 10 but the pump 12). In order to regulate the temperature of the cooling water to be the second temperature (100° C.) by restricting heat radiation at the radiator 3, a flow volume to the second flow passage 30, the radiator 3 and the third flow passage 32 is made large. The cooling water flows through the second flow passage 30, the radiator 3 and the third flow passage 32, and then flows into the engine 2. Thus, the heat radiation at the radiator 3 is promoted, and thereby the temperature of the cooling water is reduced to become the first temperature (80° C.).

Advantages equivalent to those brought by the water-cooling apparatus 1a in the first embodiment can be also brought by the water-cooling apparatus 1b in the present embodiment that is configures as explained above.

Modified Example of Second Embodiment

As shown in FIG. 19, a position of a regulating valve 11 in a water-cooling apparatus 1b′ for an engine according to a modified example of the second embodiment is different from that in the water-cooling apparatus 1b according to the second embodiment (see FIG. 14). Since other configurations of the water-cooling apparatus 1b′ in the present modified example are identical to those of the water-cooling apparatus 1b according to the second embodiment, their redundant explanations will be omitted.

The regulating valve 11 in the present modified example is also a three-way disposed on the first flow passage and on a downstream side from the pump 12. But, whereas the regulating valve 11 in the second embodiment is disposed at a branch point of the second flow passage 30 on the first flow passage 31, the regulating valve 11 in the present modified example is disposed at a confluent point of the third flow passage 32 on the first flow passage 31. The regulating valve 11 is an electrically-controlled thermostat, and controls a flow volume of the cooling water to be flown to the to the engine 2 and/or the radiator 3 based on the signals from the controller (not shown) by controlling a mixture rate of the cooling water from the pump 12 and the cooling water from the third flow passage 32. The regulating valve 11 in the present modified example controls a flow volume of the cooling water to be flown to the radiator 3 at a downstream from the radiator 3.

A warm-up control of the engine 2 by the water-cooling apparatus 1b′ is different from the warm-up control in the second embodiment in the processes of the steps S14 and S22 (see FIG. 15) that relate to the regulating valve 11. Since a whole of the warm-up control is carried out in line with the flowchart shown in FIG. 15 also in the present modified example, only the different steps S14 and S22 will be explained hereinafter.

In the step S14, the temperature of the cooling water is equal-to or lower-than the first temperature (80° C.) (YES in step S10) and the heater switch is turned off (NO in step S11). Therefore, heats are not radiated at the radiator 3 and the heater core 4, and thereby the cooling water is made higher than the first temperature (80° C.) quickly. Namely, as shown in FIG. 20, the electromagnetic valve 25 is closed (step S12) and the regulating valve 11 closes the third flow passage 32 (at its downstream end) based on the control signal from the controller (step S14).

On the other hand, in the step S22, the temperature of the cooling water is equal-to or lower-than the first temperature (80° C.) (YES in step S10) and the heater switch is turned on (YES in step S11). Therefore, heats are not radiated at the radiator 3, and thereby the cooling water is made higher than the first temperature (80° C.) quickly. Namely, the electromagnetic valve 25 is opened (step S20: to radiates heats at the heater core 4 because the heater switch is turned on) and the regulating valve 11 closes the third flow passage 32 (at its downstream end) based on the control signal from the controller (step S22).

A normal control (after the warm-up control) by the water-cooling apparatus 1b′ is different from the normal control in the second embodiment in the processes of the steps S114 and S122 (see FIG. 17) that relate to the regulating valve 11. Since a whole of the normal control is carried out in line with the flowchart shown in FIG. 17 also in the present modified example, only the different steps S114 and S122 will be explained hereinafter.

In the step S114, since the engine 2 is idled (YES in step S110) or the change of a throttle position is small (YES in step S111), the engine 2 is in a low-load state. Therefore, the regulating valve 11 is controlled so that a flow volume of the cooling water to the radiator 3 becomes small to restrict heat radiation at the radiator 3, and thereby the temperature of the cooling water is raised to the second temperature (100°). Namely, a valve opening position of the regulating valve 11 is adjusted based on the control signal from the controller, and thereby a flow volume of the cooling water flowing through the radiator 3 is adjusted at the downstream end of the third flow passage 32 (step S114). In order to regulate the temperature of the cooling water to be the second temperature (100° C.) by restricting heat radiation at the radiator 3, a flow volume to the second flow passage 30, the radiator 3 and the third flow passage 32 is made relatively small (see FIG. 21). Note that the regulating valve 11 also flows the cooling water from the pump 12 to the engine 2.

On the other hand, in the step S122, since the change of a throttle position is large (NO in step S111), the engine 2 is in a high-load state. Therefore, the regulating valve 11 is controlled so that a flow volume of the cooling water becomes large to promote heat radiation at the radiator 3, and thereby the temperature of the cooling water is regulated to be the first temperature (80°). Namely, a valve opening position of the regulating valve 11 is adjusted based on the control signal from the controller to close a flow path from the first flow passage 31 and to fully-open a valve opening position of the downstream end of the third flow passage 32 (step S122), and thereby the cooling water is flown only to the second flow passage 30, the radiator 3 and the third flow passage 32 (similar to FIG. 13: however, not the pump 10 but the pump 12).

Advantages equivalent to those brought by the water-cooling apparatus 1b in the second embodiment, i.e. advantages equivalent to those brought by the water-cooling apparatus 1a in the first embodiment can be also brought by the water-cooling apparatus 1b′ in the present modified example that is configures as explained above.

Third Embodiment

As shown in FIG. 22, a water-cooling apparatus 1c for an engine according to a third embodiment has a configuration in which an on-off valve 13 is added to the water-cooling apparatus 1b in the second embodiment (see FIG. 14). One side (flow-out side) of the on-off valve 13 is connected with the fifth flow passage 22 (an upstream side from the pump 12), and another side (flow-in) thereof is connected with the first flow passage 31 (a downstream side from the pump 12, and an upstream side from the regulating valve 11). The on-off valve 13 regulates a flow volume of the cooling water to the regulating valve 11 (i.e. the engine 2). Since other configurations of the water-cooling apparatus ic in the present embodiment are identical to those of the water-cooling apparatus 1b in the second embodiment, their redundant explanations will be omitted.

Hereinafter, a warm-up control of the engine 2 by the water-cooling apparatus 1c will be explained with reference to a flowchart shown in FIG. 23.

First, it is judged whether or not temperature of the cooling water detected by the temperature sensor is equal-to or lower-than the first temperature (80° C.) as a reference index for completion of warming-up (step S10). If the temperature of the cooling water is higher than the first temperature (80° C.) (NO in step S10), it transitions to a normal control to be carried out after the worm-up control (step S30), and the worm-up control is ended. The normal control will be explained later in detail. On the other hand, if the temperature of the cooling water is equal-to or lower-than the first temperature (80° C.) (YES in step S10), it is judged whether or not a heater switch of an air-conditioner is turned on (step S11).

If the heater switch is not turned on (NO in step S11), the controller sends control signals for making the temperature of the cooling water higher than the first temperature (80° C.) quickly to the regulating valve 11, the electromagnetic valve 25 and the on-off valve 13. Here, since the heater switch is turned off, it is not needed to flow the cooling water to the heater core 4. Therefore, the electromagnetic valve 25 on the upstream side from the heater core 4 is closed based on the control signal from the controller (step S12). Further, the second flow passage 30 is also closed by the regulating valve 11 as shown in FIG. 24 (after-explained step S14), and thereby the cooling water is not flown to the radiator 3. Thus, heats are not radiated at the radiator 3 and the heater core 4, and thereby temperature of the cooling water is made higher than the first temperature (80° C.) quickly.

Subsequent to the step S12, the on-off valve 13 is opened based on the control signal from the controller (step S15). When the on-off valve 13 is opened, the cooling water is recirculated from a downstream side (high-pressure side) of the pump 12 to an upstream side (low-pressure side) thereof as shown in FIG. 24, and thereby a flow volume to the regulating valve 11 (i.e. the engine 2) is reduced. By reducing the flow volume to the engine 2, temperature of the cooling water in the engine 2 is raised quickly to suitable temperature for heat efficiency due to absorption of heats of the engine 2.

Subsequent to the step S15, the regulating valve 11 closes the second flow passage 30 (at its upstream end) based on the control signal from the controller (step S16). Heats are not radiated at the radiator 3 due to the closure of the second flow passage 30, and thereby the temperature of the cooling water can be prevented from reducing during the warm-up control. After the step S16, the process flow is returned to the step S10, and then it transitions to the normal control (step S30) when the temperature of the cooling water becomes higher than the first temperature (80° C.) (NO in step S10).

On the other hand, if the heater switch is turned on in the step S11 (YES in step S11), the electromagnetic valve 25 on the upstream side from the heater core 4 is controlled to flow the cooling water to the heater core 4 for air-heating. Specifically, a valve opening position of the electromagnetic valve 25 is set so as to flow the cooling water to the heater core 4 by 10 L/min based on the control signal from the controller (step S20).

Subsequent to the step S20, the on-off valve 13 is closed based on the control signal from the controller (step S23). When the on-off valve 13 is closed, the cooling water is not recirculated and a flow volume to the regulating valve 11 (i.e. the engine 2) is not reduced.

Subsequent to the step S23, the regulating valve 11 closes the second flow passage 30 based on the control signal from the controller (step S24). Heats are not radiated at the radiator 3 due to the closure of the second flow passage 30, and thereby the temperature of the cooling water can be prevented from reducing during the warm-up control. Although heats are radiated at the heater core 4 for air-heating, heats are not radiated at the radiator 3 and thereby the temperature of the cooling water will become higher than the first temperature (80° C.) quickly. After the step S24, the process flow is returned to the step S10, and then it transitions to the normal control (step S30) when the temperature of the cooling water becomes higher than the first temperature (80° C.) (NO in step S10).

Next, a normal control of the engine 2 (after the warm-up control) by the water-cooling apparatus 1c will be explained with reference to a flowchart shown in FIG. 25.

First, it is judged whether or not the engine 2 is idled (step S110). If it is not idled (NO in step S110), it is judged whether or not a change of a throttle position is small in order to estimate an operation state of the engine 2 (step S111).

If the change of a throttle position is small, i.e. the engine 2 is in a low-load state (YES in step S111), the controller sends control signals for regulating the temperature of the cooling water to be the second temperature (100° C.) to the regulating valve 11, the electromagnetic valve 25 and the on-off valve 13. Since, in a low-load state of the engine 2, fuel efficiency is better when the temperature of the cooling water is the second temperature (100° C.) higher than the first temperature (80° C.) as shown in FIG. 3(a), the temperature of the cooling water is regulated to be the second temperature (100° C.).

Specifically, since the worming-up is completed, the electromagnetic valve 25 is opened based on the control signal from the controller to circulate the cooling water through the heater core 4 (step S112). According to this, an air-conditioner can use heats of the heater core 4 at any time. Note that, since it is in a low-load state with no change of a throttle position when idled in the step S110 (YES in step S110), the process flow proceeds to the step S112 without the judgment of the step S111.

Subsequent to the step S112, the on-off valve 13 is closed based on the control signal from the controller (step S115). When the on-off valve 13 is closed, the cooling water is not recirculated and a flow volume to the regulating valve 11 (i.e. the engine 2) is not reduced.

Subsequent to the step S115, a valve opening position of the regulating valve 11 is adjusted based on the control signal from the controller to adjust a flow volume of the cooling water flowing through the radiator 3 at the upstream end of the second flow passage 30 (step S116). In order to regulate the temperature of the cooling water to be the second temperature (100° C.) by restricting heat radiation at the radiator 3, a flow volume to the second flow passage 30, the radiator 3 and the third flow passage 32 is made relatively small (see FIG. 26). Note that the regulating valve 11 also flows the cooling water from the pump 12 to the engine 2.

On the other hand, if the change of a throttle position is large, i.e. the engine 2 is in a high-load state (NO in step S111), the controller sends control signals for regulating the temperature of the cooling water to be the first temperature (80° C.) to the regulating valve 11, the electromagnetic valve 25 and the on-off valve 13. Since, in a high-load state of the engine 2, fuel efficiency is better when the temperature of the cooling water is the first temperature (80° C.) lower than the second temperature (100° C.) as shown in FIG. 3(b), the temperature of the cooling water is regulated to be the first temperature (80° C.).

Specifically, similarly to the above-explained step S112, since the worming-up is completed, the electromagnetic valve 25 is opened based on the control signal from the controller to circulate the cooling water through the heater core 4 (step S120). Subsequent to the step S120, the on-off valve 13 is closed based on the control signal from the controller (step S123). When the on-off valve 13 is closed, the cooling water is not recirculated and a flow volume to the regulating valve 11 (i.e. the engine 2) is not reduced. Since a flow volume to the regulating valve 11 (i.e. the engine 2) is not reduced, a flow volume of the cooling water circulating in the cooling apparatus 1c is controlled to be large. Heat radiation at the radiator 3 is promoted by making the flow volume large, and thereby the temperature of the cooling water is restricted from rising and kept at the first temperature (80° C.) (a flow of the cooling water to the radiator 3 will be explained in a next step S124).

Subsequent to the step S123, a valve opening position of the regulating valve 11 is adjusted based on the control signal from the controller to close a flow path to the first flow passage 31 connected with the engine 2 and to fully-open a valve opening position of the upstream end of the second flow passage 30 (step S124), and thereby the cooling water is flown only to the second flow passage 30, the radiator 3 and the third flow passage 32. In order to regulate the temperature of the cooling water to be the first temperature (80° C.) by promoting heat radiation at the radiator 3, a flow volume to the second flow passage 30, the radiator 3 and the third flow passage 32 is made large. The cooling water flows through the second flow passage 30, the radiator 3 and the third flow passage 32, and then flows into the engine 2. Thus, the heat radiation at the radiator 3 is promoted, and thereby the temperature of the cooling water is reduced to become the first temperature (80° C.).

Advantages equivalent to those brought by the water-cooling apparatus 1b in the second embodiment, i.e. advantages equivalent to those brought by the water-cooling apparatus 1a in the first embodiment can be also brought by the water-cooling apparatus Ic in the present embodiment that is configures as explained above.

Modified Example of Third Embodiment

As shown in FIG. 27, a position of a regulating valve 11 in a water-cooling apparatus 1c′ for an engine according to a modified example of the third embodiment is different from that in the water-cooling apparatus 1c according to the third embodiment (see FIG. 22). Since other configurations of the water-cooling apparatus 1c′ in the present modified example are identical to those of the water-cooling apparatus 1c according to the third embodiment, their redundant explanations will be omitted.

The regulating valve 11 in the present modified example is also a three-way disposed on the first flow passage and on a downstream side from the pump 12. But, whereas the regulating valve 11 in the third embodiment is disposed at a branch point of the second flow passage 30 on the first flow passage 31, the regulating valve 11 in the present modified example is disposed at a confluent point of the third flow passage 32 on the first flow passage 31. The regulating valve 11 is an electrically-controlled thermostat, and controls a flow volume of the cooling water to be flown to the to the engine 2 and/or the radiator 3 based on the signals from the controller (not shown) by controlling a mixture rate of the cooling water from the pump 12 and the cooling water from the third flow passage 32. The regulating valve 11 in the present modified example controls a flow volume of the cooling water to be flown to the radiator 3 at a downstream from the radiator 3.

A warm-up control of the engine 2 by the water-cooling apparatus 1c′ is different from the warm-up control in the third embodiment in the processes of the steps S16 and S24 (see FIG. 23) that relate to the regulating valve 11. Since a whole of the warm-up control is carried out in line with the flowchart shown in FIG. 23 also in the present modified example, only the different steps S16 and S24 will be explained hereinafter.

In the step S16, the temperature of the cooling water is equal-to or lower-than the first temperature (80° C.) (YES in step S10) and the heater switch is turned off (NO in step S11). Therefore, heats are not radiated at the radiator 3 and the heater core 4, and thereby the cooling water is made higher than the first temperature (80° C.) quickly. Namely, as shown in FIG. 28, the electromagnetic valve 25 is closed (step S12) and the on-off valve 13 is opened (step S15). Further, the regulating valve 11 closes the third flow passage 32 (at its downstream end) based on the control signal from the controller (step S16).

On the other hand, in the step S26, the temperature of the cooling water is equal-to or lower-than the first temperature (80° C.) (YES in step S10) and the heater switch is turned on (YES in step S11). Therefore, heats are not radiated at the radiator 3, and thereby the cooling water is made higher than the first temperature (80° C.) quickly. Namely, the electromagnetic valve 25 is opened (step S20: to radiates heats at the heater core 4 because the heater switch is turned on) and the on-off valve 13 is closed (step S23). Further, the regulating valve 11 closes the third flow passage 32 (at its downstream end) based on the control signal from the controller (step S26).

A normal control (after the warm-up control) by the water-cooling apparatus 1c′ is different from the normal control in the third embodiment in the processes of the steps S116 and S124 (see FIG. 25) that relate to the regulating valve 11. Since a whole of the normal control is carried out in line with the flowchart shown in FIG. 25 also in the present modified example, only the different steps S116 and S124 will be explained hereinafter.

In the step S116, since the engine 2 is idled (YES in step S110) or the change of a throttle position is small (YES in step S111), the engine 2 is in a low-load state. Therefore, the regulating valve 11 is controlled so that a flow volume of the cooling water to the radiator 3 becomes small to restrict heat radiation at the radiator 3, and thereby the temperature of the cooling water is raised to the second temperature (100°). Namely, a valve opening position of the regulating valve 11 is adjusted based on the control signal from the controller, and thereby a flow volume of the cooling water flowing through the radiator 3 is adjusted at the downstream end of the third flow passage 32 (step S116). In order to regulate the temperature of the cooling water to be the second temperature (100° C.) by restricting heat radiation at the radiator 3, a flow volume to the second flow passage 30, the radiator 3 and the third flow passage 32 is made relatively small (see FIG. 29). Note that the regulating valve 11 also flows the cooling water from the pump 12 to the engine 2.

On the other hand, in the step S124, since the change of a throttle position is large (NO in step S111), the engine 2 is in a high-load state. Therefore, the regulating valve 11 is controlled so that a flow volume of the cooling water becomes large to promote heat radiation at the radiator 3, and thereby the temperature of the cooling water is regulated to be the first temperature (80°). Namely, a valve opening position of the regulating valve 11 is adjusted based on the control signal from the controller to close a flow path from the first flow passage 31 and to fully-open a valve opening position of the downstream end of the third flow passage 32 (step S124), and thereby the cooling water is flown only to the second flow passage 30, the radiator 3 and the third flow passage 32.

Advantages equivalent to those brought by the water-cooling apparatus 1c in the third embodiment, i.e. advantages equivalent to those brought by the water-cooling apparatus 1a in the first embodiment or the water-cooling apparatus 1b in the second embodiment can be also brought by the water-cooling apparatus 1c′ in the present modified example that is configures as explained above.

The present invention is not limited to the above embodiments. For example, an operation state (a low-load state or a high-load state) of the engine 2 is judged based on a change of a throttle position in the above embodiments. However, an operation state of the engine 2 may be judged based on a vehicle speed, an acceleration of a throttle position, or a combination of these. Specifically, the control will be done based on judgment of a high-load state when an acceleration of a throttle position is large, or based on judgment of a low-load state when an acceleration of a throttle position is small.

In addition, the first temperature is 80° C. and the second temperature is 100° C. in the above embodiments, but the first temperature may be 70° C. or the like and, similarly, the second temperature may be 90° C. or the like. The first temperature is lower than the second temperature and brings most appropriate combustion efficiency in a high-load state of the engine 2. The second temperature is higher than the first temperature and brings most appropriate combustion efficiency in a low-load state of the engine 2.

It should be understood that the present invention includes various modifications, and the present invention is limited only by subject matters specifying the invention in Claims that are reasonably understood brom the above disclosures.

Claims

1. A water-cooling apparatus for an engine that cools an internal combustion engine by cooling water, the apparatus comprising:

a radiator that cools the cooling water by heat-exchanging between the cooling water and air;

a first flow passage that flows the cooling water to the engine;

a second flow passage that is branched from the first flow passage and flows the cooling water to the radiator;

a third flow passage that flows the cooling water flowing from the radiator to the first flow passage at a downstream from a branched point of the second flow passage from the first flow passage;

a regulating valve that is disposed on the first flow passage and regulates a flow volume of the cooling water flowing through the radiator; and

a pump that is disposed on the first flow passage and circulates the cooling water through the engine and/or the radiator, wherein

the regulating valve is configured to flows the cooling water flowing from the radiator to the first flow passage when opened.

2. The water-cooling apparatus for an engine according to claim 1, wherein,

in a case where temperature of the cooling water that brings most appropriate combustion efficiency in a high-load state of the engine is defined as a first temperature,

when temperature of the cooling water in the engine is equal-to or higher-than the first temperature, the regulating valve closes a flow path through the second flow passage, the radiator and the third flow passage.

3. The water-cooling apparatus for an engine according to claim 1, wherein

the pump is an electrical pump operable independently from operations of the engine.

4. The water-cooling apparatus for an engine according to claim 1, wherein,

in a case where temperature of the cooling water that brings most appropriate combustion efficiency in a high-load state of the engine is defined as a first temperature, and temperature of the cooling water that brings most appropriate combustion efficiency in a low-load state of the engine is defined as a second temperature higher than the first temperature,

when temperature of the cooling water in the engine is equal-to or higher-than the first temperature and a change of a throttle position for adjusting an intake air volume to the engine is small, the regulating valve regulates a flow volume of the cooling water to a flow path through the second flow passage the radiator and the third flow passage so that the temperature of the cooling water is regulated to be the second temperature.

5. The water-cooling apparatus for an engine according to claim 1, wherein

in a case where temperature of the cooling water that brings most appropriate combustion efficiency in a high-load state of the engine is defined as a first temperature,

when temperature of the cooling water in the engine is equal-to or higher-than the first temperature and a change of a throttle position for adjusting an intake air volume to the engine is large, the regulating valve increases a flow volume of the cooling water to a flow path through the second flow passage the radiator and the third flow passage.

6. The water-cooling apparatus for an engine according to claim 1, wherein

the engine is inclined with an exhaust side thereof faced downward.