COOLING WATER TEMPERATURE CONTROL APPARATUS FOR AN INTERNAL COMBUSTION ENGINE
The present invention is intended to provide a technique which makes effective use of a phase transition temperature zone of cooling water by controlling a control valve for changing the temperature of the cooling water in an appropriate manner. The present invention resides in a cooling water temperature control apparatus for an internal combustion engine in which cooling water is caused to circulate, said cooling water having variable specific heat, said apparatus comprising: a received heat amount calculation unit configured to calculate an amount of received heat which is received by said cooling water, a control valve that is controlled to open and close according to a command so as to change a circulation route or an amount of circulation of said cooling water and to change the temperature of said cooling water, and a control unit configured to control said control valve based on the amount of received heat which is calculated by said received heat amount calculation unit.
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The present invention relates to a cooling water temperature control apparatus for an internal combustion engine.
BACKGROUND ARTThere has been known a technique which controls the temperature of cooling water in an internal combustion engine by using a valve opening adjustment unit which is able to adjust electronically the degree of opening of a valve in an electronic manner, wherein an optimum value of the temperature of the cooling water is estimated based on an operating condition up to the present of the internal combustion engine, so that the degree of valve opening of the valve opening adjustment unit is adjusted based on an estimated value of a future temperature of the cooling water at an inlet port of the internal combustion engine, and said estimated optimum value (for example, refer to a first patent document). According to the technique of this first patent document, the temperature of the cooling water in the internal combustion engine can be controlled to a more suitable temperature.
On the other hand, there has been disclosed a technique which uses, as cooling water for cooling an internal combustion engine, a kind of cooling water of which the specific heat is variable due to inclusion of particles therein which change in phase from one of a solid phase state and a liquid phase state to the other thereby to change a specific heat of a medium (for example, refer to a second patent document).
CITATION LIST Patent Literature
- PTL 1: Japanese patent application laid-open No. 2007-100638
- PTL 2: Japanese patent application laid-open No. 2009-044896
- PTL 3: Japanese patent application laid-open No. 2005-325790
In cases where the cooling water with a variable specific heat disclosed in the second patent document is used, when control is intended to be carried out on the basis of the temperature of the cooling water using the technique disclosed in the first patent document, the control can not be performed adequately because a temperature range of the cooling water, which corresponds to a state of the cooling water in which the specific heat of the cooling water is variable (phase transition temperature zone), is narrow. Specifically, even if the temperature of the cooling water exists in the phase transition temperature zone by setting a target temperature of the cooling water to be in the phase transition temperature zone, there will be a possibility that if an amount of received heat is high or large though it is within an allowable range of the transition temperature zone, the specific heat of the cooling water may immediately become low upon receiving a further amount of heat, so that the temperature of the cooling water may rapidly go up, thus resulting in an overheat. On the other hand, if the target temperature of the cooling water is set, in order to avoid this situation, to be lower than the phase transition temperature zone, there will be a possibility that the oil in the internal combustion engine may get cold and the friction of the internal combustion engine may increase.
The present invention has been made in view of the above-mentioned circumstances, and has for its object to provide a technique in which in cases where cooling water with a variable specific heat is used, a control valve for changing the temperature of the cooling water is controlled adequately, so that effective use of a phase transition temperature zone of the cooling water can be made.
Solutions to ProblemIn the present invention, the following construction is adopted. That is, the present invention resides in a cooling water temperature control apparatus for an internal combustion engine in which cooling water is caused to circulate, said cooling water having variable specific heat, said apparatus comprising:
a received heat amount calculation unit configured to calculate an amount of received heat which is received by said cooling water;
a control valve that is controlled to open and close according to a command so as to change a circulation route or an amount of circulation of said cooling water and to change the temperature of said cooling water; and
a control unit configured to control said control valve based on the amount of received heat which is calculated by said received heat amount calculation unit.
In the case of the cooling water with a variable specific heat, the temperature of the cooling water does not change in a phase transition temperature zone of the cooling water even if the amount of heat received by the cooling water changes to some extent. The phase transition temperature zone of the cooling water is a temperature zone corresponding to a state of the cooling water in which the specific heat of the cooling water changes due to a phase transition of particles in the cooling water, or the like. In this phase transition temperature zone, even if a change occurs in the amount of heat given to the cooling water (i.e., the amount of received heat), a phase transition of the particles will occur, so that the specific heat thereof will change, thus changing of the temperature of the cooling water is suppressed. In other words, in the phase transition temperature zone, an allowable range of the amount of received heat is wide in which the cooling water remains unchanged in its temperature. For this reason, when it is intended to control the control valve on the basis of the temperature of the cooling water, the control of the control valve may sometimes become excessive and can not be carried out adequately because the temperature range of the phase transition temperature zone is narrow. This is because the amount of heat received by the cooling water can not be determined on the basis of the target temperature within the phase transition temperature zone. Even if the cooling water is of the target temperature, there will be a case where the amount of received heat thereof within the phase transition temperature zone may be high or low. Accordingly, even if the cooling water is of the target temperature, there will be a possibility that the state of the cooling water may immediately become out of the phase transition temperature zone when the amount of received heat thereof changes. However, if the control valve is controlled on the basis of the amount of received heat of the cooling water, the range of the amount of received heat corresponding to the phase transition temperature zone of the cooling water is wide, and hence, by setting a target amount of received heat, the control of the control valve can be finely carried out in an appropriate manner within the phase transition temperature zone.
According to this, for example, when the target amount of received heat of the cooling water is set to be a value of the receiving heat amount on a lower side of the phase transition temperature zone, even if a further amount of heat is received, the temperature of the cooling water will be maintained within the phase transition temperature zone, and hence, it is possible to avoid such a situation that the specific heat of the cooling water may immediately become low thereby to cause the temperature of the cooling water to go up rapidly, thus resulting in an overheat. In addition, it is not necessary to set the target amount of received heat of the cooling water to be an excessively low value, so it is possible to avoid such a situation that the temperature of the cooling water becomes too low, then the oil in the internal combustion engine gets cold, resulting in increasing the friction of the internal combustion engine.
According to the present invention, in cases where the cooling water with its specific heat being variable is used, it is possible to make effective use of the phase transition temperature zone of the cooling water by controlling the control valve for changing the temperature of the cooling water adequately.
Said received heat amount calculation unit preferably calculates an inlet received heat amount which is received by said cooling water at an inlet port from which said cooling water flows into the internal combustion engine, and
said control unit preferably controls said control valve in such a manner that said inlet received heat amount calculated by said received heat amount calculation unit comes near to a lower side starting value of received heat amount of the phase transition temperature zone in which said cooling water is in a state in which the specific heat thereof changes due to a phase transition of particles.
According to this, it is possible to set a target inlet received heat amount of the cooling water as a value of the receiving heat amount near to the lower side starting value of the phase transition temperature zone, and hence, even if an additional amount of heat is further received by the cooling water in the internal combustion engine, the temperature of the cooling water is maintained within the phase transition temperature zone, thus making it possible to avoid such a situation that the specific heat of the cooling water may immediately become low thereby to cause the temperature of the cooling water to go up rapidly, resulting in an overheat.
Said received heat amount calculation unit preferably calculates an outlet received heat amount which is received by said cooling water at an outlet port from which said cooling water flows out of the internal combustion engine, and
in cases where said outlet received heat amount calculated by said received heat amount calculation unit becomes a high amount of received heat in excess of an amount of received heat of said phase transition temperature zone, said control unit preferably controls said control valve so that said outlet received heat amount is included in the range of the amount of received heat of said phase transition temperature zone.
According to this, it is possible to set a target outlet received heat amount of the cooling water as a value included in the range of the amount of received heat of the phase transition temperature zone, as a result the temperature of the cooling water flowing out of the internal combustion engine is maintained within the range of the temperature of the phase transition temperature zone, thus making it possible to avoid such a situation that the specific heat of the cooling water may immediately become low thereby to cause the temperature of the cooling water to go up rapidly, resulting in an overheat.
In cases where said received heat amount calculation unit can not calculate the amount of received heat, it is preferable to control said control valve in such a manner as to lower the temperature of said cooling water.
According to this, in cases where the amount of received heat can not be calculated, it is possible to lower the temperature of the cooling water, thus making it possible to avoid the temperature of the cooling water from going up to cause an overheat.
Advantageous Effects of InventionAccording to the present invention, in cases where cooling water with its specific heat being variable is used, by controlling the control valve for changing the temperature of the cooling water adequately, it is possible to make effective use of the phase transition temperature zone of the cooling water.
In the following, a specific embodiment of the present invention will be described.
First EmbodimentThe radiator 3 serves to cool the cooling water by carrying out heat exchange between the cooling water and outside air. The oil cooler 4 is a water cooled oil cooler, and carries out heat exchange between oil supplied to the internal combustion engine 1 and the cooling water thereby to cool the oil. The throttle valve 5a is a valve which serves to control an amount of intake air of the internal combustion engine 1, and it is cooled by the cooling water. The EGR valve 5b is a valve which serves to control an amount of EGR gas which is a part of an exhaust gas which is caused to flow back or return to the internal combustion engine 1, and it is cooled by the cooling water. The reservoir tank 6 temporarily stores the cooling water. The heater core 7 serves to warm the cooling water. The EGR cooler 8 is a water cooling type EGR cooler, and carries out heat exchange between the EGR gas returned to the internal combustion engine 1 and the cooling water thereby to cool the EGR gas.
The passage 2b, through which the cooling water coming from a cylinder block flows through the oil cooler 4, is connected to the passage 2a, through which the cooling water flows through the radiator 3. In addition, the passage 2a, through which the cooling water flows through the radiator 3, branches into the passage 2c, through which the cooling water flows through the throttle valve 5a and the EGR valve 5b, and the passage 2d, through which the cooling water flows through the reservoir tank 6. The passage 2f, through which the cooling water coming from the cylinder block flows through the EGR cooler 8, is connected to the passage 2e, through which the cooling water flows through the heater core 7.
An electronic thermostat 9 is arranged at a location at which the passage 2a, through which the cooling water flows through the radiator 3, and the bypass passage 2g are connected to each other. The electronic thermostat 9 is a control valve which is controlled to open and close in accordance with a command, and when opened, it can change the flow path and the flow amount of the cooling water so that the cooling water flows through the radiator 3, thereby making it possible to lower the temperature of the cooling water. At this time, the amount of flow of the cooling water in the bypass passage 2g is throttled or reduced. On the contrary, by closing the electronic thermostat 9, the circulation route (flow path) and the flow amount of the cooling water can be changed, so that it becomes difficult for the cooling water to flow through the radiator 3, thereby making it difficult for the temperature of the cooling water to fall. At this time, the amount of flow of the cooling water in the bypass passage 2g is increased. The cooling water is sent into a water pump 10 at the downstream side of the electronic thermostat 9. The water pump 10 pumps up the cooling water, and supplies it into the cylinder block of the internal combustion engine 1. In addition, a water temperature sensor 11 is arranged at a location at which the cooling water passage 2 is connected to an outlet port of the internal combustion engine 1, so that the temperature of the cooling water flowing out of the internal combustion engine 1 is detected by means of the water temperature sensor 11.
Here, the cooling water flowing through the cooling water passage 2 is cooling water of which the specific heat is variable. That is, the cooling water is kind of cooling water of which the specific heat is variable due to containing particles that make a phase transition from one of a solid phase state and a liquid phase state to the other thereby change the specific heat of a medium. Here, note that as such particles, there can also be used those which make a phase transition from one of a liquid phase state and a gas phase state to the other, in addition to the particles which make a phase transition from one of the solid phase state and the liquid phase state to the other. The cooling water is one in which particles formed by wrapping some substances in capsules are mixed into a solvent of the cooling water, so that the internal substances of the particles make a phase transition from a solid state to a liquid state when the temperature thereof becomes equal to or higher than a fixed level, as shown in
An ECU (electronic control unit) 12 is provided in combination with this internal combustion engine 1. A variety of kinds of sensors such as the water temperature sensor 11 and so on are connected to the ECU 12 through electrical wiring, so that output signals of these various sensors are inputted to the ECU 12. On the other hand, the throttle valve 5a, the EGR valve 5b, the heater core 7, the electronic thermostat 9, the water pump 10, and so on are connected to the ECU 12 through electrical wiring, so that these component parts are controlled by means of the ECU 12.
(Cooling Water Temperature Control)
In the past, an electronic thermostat has been controlled on the basis of the temperature of cooling water has been carried out. For example, a future optimal temperature of the cooling water is estimated, and the electronic thermostat is controlled in such a manner that the temperature of the cooling water is adjusted to become the optimal temperature thus estimated. However, in cases where a cooling water with its specific heat being variable as in this embodiment is used as cooling water, there has been a problem that the advantage of such a cooling water could not be exploited effectively.
That is, in the case of the cooling water with a variable specific heat, the temperature of the cooling water does not change in the phase transition temperature zone of the cooling water even if the amount of heat received by the cooling water changes to some extent. In other words, in the phase transition temperature zone of the cooling water, the allowable range of the amount of received heat is wide in which the cooling water remains unchanged in its temperature. For this reason, when it is intended to control the electronic thermostat on the basis of the temperature of the cooling water as in the past, the control of the electronic thermostat may sometimes become excessive and can not be carried out in an appropriate manner because the temperature range of the phase transition temperature zone of the cooling water is narrow. This is because with a target temperature in the phase transition temperature zone of the cooling water, the amount of heat received by the cooling water can not be determined, so there will be a case where even if the cooling water is at the target temperature, the amount of received heat thereof lying within the phase transition temperature zone may be high (at point A in
In order to avoid such an overheat, it is considered that the target temperature of the cooling water may be set lower than the phase transition temperature zone. A point B shown in
As described above, in the case of using the cooling water of which the specific heat is variable, when the electronic thermostat was controlled based on the temperature of the cooling water, the advantage of the cooling water of which the specific heat is variable could not be utilized efficiently, so that the electronic thermostat was not able to be controlled in an appropriate manner. For this reason, it is possible to make effective use of the phase transition temperature zone of the cooling water.
Accordingly in this embodiment, the amount of heat received by the cooling water is calculated, and the electronic thermostat 9 is controlled based on the amount of received heat thus calculated. In this case, the range of the amount of received heat of the phase transition temperature zone of the cooling water is wide, and hence, by setting a target amount of received heat, the control of the control valve can be finely carried out in an appropriate manner in a range including the phase transition temperature zone.
As specific control in this embodiment, an inlet received heat amount, which is received by the cooling water at the inlet port from which said cooling water flows into the internal combustion engine, is calculated. Then, the electronic thermostat 9 is controlled in such a manner that the inlet received heat amount thus calculated comes near to a lower side starting value of the received heat amount of the phase transition temperature zone in which the cooling water is in a state in which the particles make a phase transition thereby the specific heat of the cooling water changes.
The calculation method of the inlet received heat amount of the internal combustion engine 1 is explained hereinafter. First, an outlet received heat amount is calculated which is received by the cooling water at the outlet port from which the cooling water flows out of the internal combustion engine 1. As shown in
Next, the flow rates in the various kinds of equipment will be calculated.
Then, the amounts of transfer heat in the various kinds of equipment will be calculated.
Thereafter, an inlet received heat amount is calculated which is received by the cooling water at the inlet port from which the cooling water flows into the internal combustion engine 1. An inlet received heat amount Qengin is obtained by dividing a total sum of products of the amounts of received heat of the various kinds of equipment and the respective flow rates in the various kinds of equipment by the amounts of received heat of the various kinds of equipment. That is, the inlet received heat amount Qengin is equal to (Qrad×Grad+Qres×Gres+Qby×Gby+Qheat×Gheat+Qoil×Goil+Qthr×Gthr+Qegr×Gegr)/(Qrad+Qres+Qby+Qheat+Qoil+Qthr+Qegr).
According to this, it is possible to set the target received heat amount of the cooling water to the lower side starting value of received heat amount of the phase transition temperature zone, and hence, even if an additional amount of heat is further received by the cooling water, the temperature of the cooling water is maintained within the phase transition temperature zone, thus making it possible to avoid such a situation that the specific heat of the cooling water may immediately become low thereby to cause the temperature of the cooling water to go up rapidly, resulting in an overheat. In addition, it is not necessary to set the target amount of received heat of the cooling water to be an excessively low value, so it is possible to avoid such a situation that the temperature of the cooling water becomes too low, then the oil in the internal combustion engine from gets cold, resulting in increasing the friction of the internal combustion engine.
According to this embodiment, in cases where the cooling water with its specific heat being variable is used, it is possible to make effective use of the phase transition temperature zone of the cooling water by controlling the control valve for changing the temperature of the cooling water in an appropriate manner.
Accordingly, in cases where the outlet received heat amount becomes a high or large amount of received heat in excess of an amount of received heat of the phase transition temperature zone, the electronic thermostat 9 is controlled in such a manner that the outlet received heat amount is brought near to a higher amount of received heat within the phase transition temperature zone. Here, note that the electronic thermostat 9 may be controlled in such a manner that the outlet received heat amount is included in a range of amount of received heat corresponding to the phase transition temperature zone.
As specific control in this embodiment, when the electronic thermostat 9 is controlled in such a manner that the inlet received heat amount comes near to the lower side starting value of received heat amount of the phase transition temperature zone, the outlet received heat amount may become a high amount of received heat in excess of an amount of received heat of the phase transition temperature zone, as shown in
According to this, it is possible to set the target outlet received heat amount of the cooling water to a higher or larger amount of received heat within the phase transition temperature zone, as a result of which the temperature of the cooling water flowing out of the internal combustion engine is maintained within the phase transition temperature zone, thus making it possible to avoid such a situation that the specific heat of the cooling water may immediately become low thereby to cause the temperature of the cooling water to go up rapidly, resulting in an overheat.
As mentioned above, when the electronic thermostat 9 is controlled based on the inlet received heat amount or the outlet received heat amount, there may be a case where it becomes impossible to calculate the inlet received heat amount or the outlet received heat amount due to some cause such as sensor abnormality, engine abnormality, and abnormality of the various kinds of equipment, etc. In this case, it becomes impossible to control the electronic thermostat 9 based on the inlet received heat amount or the outlet received heat amount.
Accordingly, in cases where the inlet received heat amount or the outlet received heat amount can not be calculated, the electronic thermostat 9 is controlled in such a manner as to lower the temperature of said cooling water.
According to this, in cases where the amount of received heat can not be calculated, the temperature of the cooling water is made to fall, thus making it possible to avoid the temperature of the cooling water from going up to cause an overheat.
(Cooling Water Temperature Control Routine)
Reference will be made to a cooling water temperature control routine in the ECU 12 based on a flow chart shown in
When the routine shown in
With this routine as described above, by controlling the control valve for changing the temperature of the cooling water in an appropriate manner, it is possible to make effective use of the phase transition temperature zone of the cooling water as much as possible.
<Others>
The cooling water temperature control apparatus for an internal combustion engine according to the present invention is not limited to the embodiment as mentioned above, but can be subjected to various changes and modifications within the scope not departing from the gist of the present invention.
REFERENCE SIGNS LIST
- 1 internal combustion engine
- 2 cooling water passage
- 3 radiator
- 4 oil cooler
- 5a throttle valve
- 5b EGR valve
- 6 reservoir tank
- 7 heater core
- 8 EGR cooler
- 9 electronic thermostat
- 10 water pump
- 11 water temperature sensor
- 12 ECU
Claims
1.-4. (canceled)
5. A cooling water temperature control apparatus for an internal combustion engine in which cooling water is caused to circulate, said cooling water having variable specific heat, said apparatus comprising:
- a received heat amount calculation unit configured to calculate an inlet received heat amount which is received by said cooling water at an inlet port from which said cooling water flows into the internal combustion engine;
- a control valve that is controlled to open and close according to a command so as to change a circulation route or an amount of circulation of said cooling water and to change the temperature of said cooling water; and
- a control unit configured to control said control valve in such a manner that said inlet received heat amount calculated by said received heat amount calculation unit comes near to a lower side starting value of received heat amount of a phase transition temperature zone in which said cooling water is in a state in which the specific heat thereof changes due to a phase transition of particles.
6. The cooling water temperature control apparatus for an internal combustion engine as set forth in claim 5, wherein
- said received heat amount calculation unit calculates an outlet received heat amount which is received by said cooling water at an outlet port from which said cooling water flows out of the internal combustion engine; and
- in cases where said outlet received heat amount calculated by said received heat amount calculation unit becomes a high amount of received heat in excess of an amount of received heat of said phase transition temperature zone, said control unit controls said control valve so that said outlet received heat amount is included in the range of the amount of received heat of said phase transition temperature zone.
7. The cooling water temperature control apparatus for an internal combustion engine as set forth in claim 5, wherein
- in cases where said received heat amount calculation unit can not calculate the amount of received heat, said control valve is controlled in such a manner as to lower the temperature of said cooling water.
8. The cooling water temperature control apparatus for an internal combustion engine as set forth in claim 6, wherein
- in cases where said received heat amount calculation unit can not calculate the amount of received heat, said control valve is controlled in such a manner as to lower the temperature of said cooling water.
Type: Application
Filed: Apr 28, 2011
Publication Date: May 15, 2014
Applicant: TOYOTA JIDOSHA KABUSHIKI KAISHA (Toyota-shi, Aichi)
Inventors: Takashi Koyama (Mishima-shi), Koichiro Nakatani (Mishima-shi), Akira Yamashita (Sunto-gun)
Application Number: 14/114,355
International Classification: F01P 7/16 (20060101);