COOLING SYSTEM FOR INTERNAL COMBUSTION ENGINE AND THERMOSTAT DEVICE

Abstract

A cooling system for an internal combustion engine includes a thermostat device including: a first inflow port connected with a second outflow passage; a second inflow port connected with a third outlet passenger; a valve controlling a flow rate of the coolant from the radiator, a thermostatic element that opens and closes the valve according to a temperature of the coolant; an outflow portion through which the coolant flows to the internal combustion engine; a guide portion that guides the coolant flowing through the second inflow port toward the thermostatic element; a slit flowing out the coolant to the outflow portion from between the guide portion and the thermostatic element; and an electric water pump configured to circulate a coolant.

Description

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2016-250944 filed on Dec. 26, 2016 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The disclosure relates to a cooling system for an internal combustion engine and a thermostat device.

2. Description of Related Art

A cooling system of an engine (internal combustion engine) described in Japanese Patent Application Publication No. 2009-52506 (JP 2009-52506 A), for example, includes a coolant circulation circuit having a water pump, radiator, thermostat device, and so forth. At the time of cold start of the engine, a valve of the thermostat device (i.e., a valve that opens and closes a return passage from the radiator) is closed, so as to stop flow of the coolant through the radiator. Namely, the coolant is circulated while bypassing the radiator, so as to achieve warm-up of the engine. After completion of warm-up of the engine, the valve of the thermostat device is opened, and the coolant flowing out from a water jacket of the engine is caused to flow through the radiator, so that the coolant releases heat collected from the engine, to the atmosphere, and suppresses overheating of the engine.

SUMMARY

While it is desired to warm up the engine early after cold start of the engine, in order to improve the fuel consumption rate, it is necessary to suppress overheating after completion of warm-up.

This disclosure provide a cooling system for an internal combustion engine and a thermostat device, which is able to suppress overheating, while assuring early warm-up of the engine.

An example aspect of the present disclosure is a cooling system for an internal combustion engine. The cooling system includes: a radiator connected with the internal combustion engine via a first outflow passage; a thermostat device connected with the radiator via a second outflow passage, connected with the internal combustion engine, the thermostat device being connected with the first outflow passage via a third outflow passage; an electric water pump configured to circulate a coolant. The thermostat device includes a first inflow port connected with the second outflow passage, a second inflow port connected with the third outflow passage, a valve controlling a flow rate of the coolant from the radiator, a thermostatic element that opens and closes the valve according to a temperature of the coolant, an outflow portion through which the coolant flows to the internal combustion engine, a guide portion that guides the coolant flowing through the second inflow port toward the thermostatic element, a slit flowing out the coolant from between the guide portion and the thermostatic element to the outflow portion. An example aspect of the present disclosure is a thermostat device for being provided in a cooling system that cools an internal combustion engine. The cooling system includes a radiator connected with the internal combustion engine via a first outflow passage, a thermostat device connected with the radiator via a second outflow passage, connected with the internal combustion engine, the thermostat device being connected with the first outflow passage via a third outflow passage, and an electric water pump configured to circulate a coolant. The thermostat device includes: a first inflow port connected with the second outflow passage; a second inflow port connected with the third outflow passage; a valve controlling a flow rate of the coolant from the radiator; a thermostatic element that opens and closes the valve according to a temperature of the coolant; an outflow portion through which the coolant flows to the internal combustion engine; a guide portion that guides the coolant flowing through the second inflow port toward the thermostatic element; a coil spring biasing the valve to close; and a frame supporting a lower end portion of the coil spring, having a slit that flows out the coolant from between the guide portion and the thermostatic element to the outflow portion.

With the above arrangement, during warm-up of the engine, the flow rate of the coolant discharged from the electric water pump is reduced, and the momentum of the coolant current is reduced, so that the coolant flowing through the second inflow port can flow out through the slit, before reaching the thermostatic element. Thus, during warm-up, the warmed coolant is less likely or unlikely to hit or contact with the thermostatic element and open the valve; therefore, early warm-up can be achieved.

After completion of warm-up, the flow rate of the coolant discharged from the electric water pump is increased, and the momentum of the coolant current is increased, so that the guide portion enables the coolant flowing through the second inflow port to reach the thermostatic element, and the warmed coolant can be brought into contact with the thermostatic element. As a result, the valve can be opened with good response, after completion of warm-up, and overheating can be suppressed.

The electric water pump may be provided such that the coolant from the outflow portion of the thermostat device flows into the electric water pump. Also, the thermostat device may be mounted on upper portion of the electric water pump.

With the above arrangement, outflow of the coolant from the slit is promoted due to a negative pressure of the electric water pump, so that the coolant warmed during warm-up can be made less likely or unlikely to hit or contact with the thermostatic element.

The thermostat device may include a coil spring that biases the valve to close, and a frame supports a lower end portion of the coil spring, and the slit may be provided on the frame.

With the cooling system for the internal combustion engine according to the disclosure, it is possible to suppress overheating while assuring early warm-up.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a view schematically showing the configuration of a cooling system according to one embodiment;

FIG. 2 is a cross-sectional view showing the internal structure of a thermostat device;

FIG. 3 is a bottom view of the thermostat device; and

FIG. 4 is a view useful for explaining flow of coolant that flows into the thermostat device through a warm-up inflow port when the flow rate is high and when the flow rate is low.

DETAILED DESCRIPTION OF EMBODIMENTS

One embodiment of the disclosure will be described based on the drawings. In this embodiment, the disclosure is applied to a cooling system for an engine for an automobile.

FIG. 1 schematically shows the configuration of a cooling system 1 according to the embodiment. As shown in FIG. 1, the cooling system 1 includes a coolant circulation circuit 10. The coolant circulation circuit 10 includes an electric water pump 2 for circulating coolant or cooling water, a radiator 3 that cools the circulating coolant, and a thermostat device 4 directly mounted on upper portion of the electric water pump 2. The electric water pump 2 operates to circulate the coolant in the coolant circulation circuit 10, so that an engine (internal combustion engine) 5 is cooled by the coolant.

The engine 5 is a gasoline engine or a diesel engine, for example, and includes a cylinder head 51 and a cylinder block 52. A head-side water jacket 51a is formed inside the cylinder head 51, and a block-side water jacket 52a is formed inside the cylinder block 52. In the engine 5 of this embodiment, the head-side water jacket 51a and the block-side water jacket 52a communicate with each other.

The cooling system 1 includes a pump discharge passage 11, engine outflow passage 12 (first outflow passage), radiator return passage 13 (second outflow passage), and a warm-up return passage 14 (third outflow passage), as coolant passages that connect respective devices included in the coolant circulation circuit 10.

The pump discharge passage 11 connects a discharge port 21 of the electric water pump 2 with the block-side water jacket 52a of the engine 5. The engine outflow passage 12 connects the head-side water jacket 51a of the engine 5 with an upper tank 31 of the radiator 3. The radiator return passage 13 connects a lower tank 32 of the radiator 3 with a radiator-side inflow port 41 of the thermostat device 4. The warm-up return passage 14 connects the engine outflow passage 12 with a warm-up inflow port 42 of the thermostat device 4. The radiator-side inflow port 41 corresponds to the above-mentioned first inflow port (first inflow port into which the coolant flows from the radiator). Also, the warm-up inflow port 42 corresponds to the above-mentioned second inflow port (second inflow port into which the coolant that bypasses the radiator flows).

The electric water pump 2 generates water flow or water current for circulating the coolant in the coolant circulation circuit 10. The electric water pump 2 has a motor (not shown) that operates with electric power from a battery (not shown), and the discharge flow rate (discharge quantity of flow per unit time) of the coolant can be varied by controlling the rotational speed of the motor. Namely, the rotational speed of the electric water pump 2 is controlled according to a pump rotational speed command signal from an ECU 100, so that the discharge flow rate is controlled. The ECU 100 controls the rotational speed of the electric water pump 2, by generating the pump rotational speed command signal according to the temperature of the coolant circulating in the coolant circulation circuit 10. The control of the rotational speed of the electric water pump 2 will be described later.

The radiator 3 is of a down-flow type, for example, and includes a radiator core 33 disposed between the upper tank 31 and the lower tank 32. When the coolant collected by the upper tank 31 flows down within the radiator core 33, toward the lower tank 32, the radiator 3 performs heat exchange between the coolant and the outside air, so as to release heat of the coolant to the atmosphere.

As shown in FIG. 2 (cross-sectional view showing the internal structure of the thermostat device 4), the thermostat device 4 has a housing 43 formed of synthetic resin, and a thermostatic element unit 44 mounted in the center of the interior of the housing 43.

The radiator-side inflow port 41 is formed in a side face (back side face in FIG. 2) in the vicinity of an upper end portion of the housing 43, and a radiator return pipe 13A that forms the radiator return passage 13 is connected to the radiator-side inflow port 41.

As shown in FIG. 3 (a bottom view of the thermostat device 4), an outflow portion 45 is provided in a lower end portion of the housing 43. The outflow portion 45 permits the coolant that has flowed through the interior of the thermostat device 4 to flow out toward the electric water pump 2. An opening 45a through which the coolant flows out is formed in the middle of the outflow portion 45. Flanges 45b, 45b connected to an upper end portion of the electric water pump 2 are formed on the radially outer side of the opening 45a. The flanges 45b, 45b are provided with bolt insertion holes 45c, 45c. Namely, the upper end portion of the electric water pump 2 is superimposed on the lower sides of the flanges 45b, 45b, and these members 2, 45b are integrally assembled by bolt fastening. In this manner, the opening 45a of the outflow portion 45 of the thermostat device 4 is communicated with an admission port of the electric water pump 2, and the coolant that has flowed through the thermostat device 4 is adapted to flow into the electric water pump 2 via the opening 45a.

Therefore, when the coolant passes through the radiator return passage 13 and flows from the radiator-side inflow port 41 into the thermostat device 4, the coolant flows from the upper side toward the lower side within the thermostat device 4, and flows out from the opening 45a of the outflow portion 45, toward the electric water pump 2.

The warm-up inflow port 42 is formed in a side face (a left side face in FIG. 2) in the vicinity of a lower end portion of the housing 43, and a warm-up return pipe 14A that forms the warm-up return passage 14 is connected to the warm-up inflow port 42.

Therefore, the coolant that has passed through the warm-up return passage 14 and entered the thermostat device 4 from the warm-up inflow port 42 flows in a lower portion of the interior of the thermostat device 4, and flows out from the opening 45a of the outflow portion 45, into the electric water pump 2.

The thermostatic element unit 44 includes a thermostatic element 44a that incorporates a thermal expansion body (thermo-wax) that expands and contracts in response to the temperature of the coolant, and a piston 44b that is advanced (or moves upward relative to the thermostatic element 44a) due to expansion of the thermal expansion body. An upper end portion of the piston 44b is fixed to a piston support portion 43a formed by projecting an inner wall of an upper part of the housing 43. Therefore, as the piston 44b is advanced, the thermostatic element 44a moves downward.

A disc-like valve 44c is attached to the thermostatic element 44a. The valve 44c is placed in a closed state when it comes into contact with a valve seat 43b formed by reducing the diameter of the inner wall of the housing 43. The valve 44c is provided for controlling the flow rate of the coolant from the radiator 3.

The thermostatic element unit 44 also includes a coil spring 44d that biases the valve 44c in a valve-closing direction. An upper end portion of the coil spring 44d is in abutting contact with a lower surface of the valve 44c. Also, a lower end portion of the coil spring 44d is supported by a spring receiving frame 6 provided in the outflow portion 45. The coil spring 44d is mounted in place such that it is compressed between the valve 44c and the spring receiving frame 6, so as to apply bias force to the valve 44c in the valve-closing direction (upward direction).

As shown in FIG. 3, the spring receiving frame 6 has engaging pieces 61, 61 formed in its outer peripheral portion, at two positions having a phase difference of 180° in the circumferential direction. The engaging pieces 61, 61 are shaped to protrude radially outward, and are supported by support protrusions 43c, 43c formed on the inner circumferential surface of the housing 43 such that the engaging pieces 61, 61 are inhibited from rotating. One of the engaging pieces 61 is located on the side (left-hand side in FIG. 3) where the warm-up return pipe 14A is mounted, and the other engaging piece 61 is located on the side (right-hand side in FIG. 3) opposite to the side where the warm-up return pipe 14A is mounted.

A lower end portion of the thermostatic element 44a is inserted into an opening 63 formed in the center of the spring receiving frame 6. Therefore, the thermostatic element unit 44 is incorporated in the housing 43, such that the upper end portion of the piston 44b is fixed to the piston support portion 43a, and lower end portions of the coil spring 44d and the thermostatic element 44a are supported by the spring receiving frame 6.

In the spring receiving frame 6, the outside diameter of its portions other than those where the engaging pieces 61, 61 are formed is set to be smaller than the inside diameter of the opening 45a. Therefore, spaces S, S that extend in the circumferential direction are formed between the inner edge of the opening 45a and the outer edge of the spring receiving frame 6. Also, slits 62, 62 that extend through the spring receiving frame 6 in its thickness direction are formed in the engaging pieces 61, 61 of the spring receiving frame 6. The slits 62, 62 are formed in the shape of long holes to extend in the circumferential direction. Therefore, in the outflow portion 45, the spaces S, S and the slits 62, 62 are formed as coolant flow passages that communicate the interior of the thermostat device 4 with the electric water pump 2.

With the thermostat device 4 constructed as described above, when the temperature of the coolant flowing into the thermostat device 4 is low, the thermal expansion body incorporated in the thermostatic element 44a is contracted, and the piston 44b is retracted (i.e., moves downward relative to the thermostatic element 44a). As a result, the valve 44c attached to the thermostatic element 44a moves relatively upward, and abuts against the valve seat 43b, so as to be closed under the bias force of the coil spring 44d. With the valve 44c thus placed in the closed state, inflow of the coolant from the radiator return passage 13 is shut off. On the other hand, if the temperature of the coolant flowing into the thermostat device 4 rises, the thermal expansion body incorporated in the thermostatic element 44a expands, and the piston 44b is advanced (i.e., moves upward relative to the thermostatic element 44a). As a result, the valve 44c attached to the thermostatic element 44a moves relatively downward, against the bias force of the coil spring 44d, to be spaced apart from the valve seat 43b, so that the valve 44c is opened. With the valve 44c thus placed in the open state, inflow of the coolant from the radiator return passage 13 is permitted.

As described above, the ECU 100 outputs the pump rotational speed command signal according to the temperature of the coolant, and controls the rotational speed of the electric water pump 2.

A water temperature sensor 101 that detects the temperature of the coolant and a pump rotational speed sensor 102 that detects the rotational speed of the electric water pump 2, for example, are connected to the ECU 100, and the ECU 100 receives output signals from the respective sensors 101, 102. The water temperature sensor 101 is mounted on the outlet side of the thermostat device 4, for example. However, the mounting position of the water temperature sensor 101 is not limited to this position. The pump rotational speed sensor 102 is mounted in the electric water pump 2.

As one example of rotational speed control of the electric water pump 2, the rotational speed of the electric water pump 2 is set low, and the discharge flow rate is reduced, during warm-up operation of the engine 5. On the other hand, after completion of warm-up of the engine 5, the rotational speed of the electric water pump 2 is set high, and the discharge flow rate is increased. Namely, during warm-up, the discharge flow rate of the electric water pump 2 is made lower than that after completion of warm-up. After completion of warm-up, the discharge flow rate of the electric water pump 2 is made higher than that during warm-up.

Some characteristic arrangements of this embodiment will be described.

As shown in FIG. 2, the warm-up inflow port 42 is in the form of an opening that is open in the horizontal direction (to the left in FIG. 2). The warm-up return pipe 14A extends along the vertical direction at one side of the thermostat device 4, and its lower-end position is set to the vicinity of a lower-end position of a side face of the thermostat device 4. Then, the warm-up inflow port 42 is formed in a portion of the housing 43 with which a side face of the warm-up return pipe 14A contacts. Therefore, the direction of the flow line of the coolant that flows through the warm-up return passage 14 within the warm-up return pipe 14A changes from the downward direction in FIG. 2 to the rightward direction (toward the interior of the thermostat device 4), in a downstream end portion of the warm-up return passage 14.

The warm-up return pipe 14A has a guide function of guiding the coolant that has flowed through the warm-up return passage 14, toward the thermostatic element 44a.

More specifically, a portion of an inner wall surface of a lower end portion of the warm-up return pipe 14A, which is located remote from the thermostat device 4 (or located on the left-hand side in FIG. 2), is formed as an inclined surface 14a that is inclined downward toward the thermostat device 4. With this arrangement, it is possible to change the direction of the flow line of the coolant as described above from the downward direction to a direction toward the interior of the thermostat device 4, while curbing reduction of the flow speed.

Also, a bottom 14c of the warm-up return pipe 14A has a horizontal surface 14b that extends in the horizontal direction from a lower edge of the inclined surface 14a, and includes a guide portion 14d as another guide function that extends toward the interior of the thermostat device 4. The horizontal dimension of the guide portion 14d (i.e., a dimension by which the guide portion 14d protrudes toward the interior of the thermostat device 4) is set by experiment or simulation, so that, when the discharge flow rate of the electric water pump 2 is set high, the coolant that has flowed through the warm-up return passage 14 can reach the thermostatic element 44a.

Since one of the engaging pieces 61 is located on the side where the warm-up return pipe 14A is mounted, the corresponding slit 62 formed in this engaging piece 61 is also located on the side where the warm-up return pipe 14A is mounted. Namely, the slit 62 is located between the guide portion 14d and the thermostatic element 44a, and is located below the warm-up inflow port 42. Namely, the dimensions and location of the slit 62 are set by experiment or simulation, so that, when the discharge flow rate of the electric water pump 2 is set low, the coolant that has flowed through the warm-up return passage 14 can be discharged from the slit 62, before reaching the thermostatic element 44a.

Next, the coolant circulating operation in the coolant circulation circuit 10 will be described.

Initially, the temperature of the coolant is low at the time of cold start of the engine 5; therefore, the thermal expansion body of the thermostatic element 44a contracts, and the valve 44c of the thermostat device 4 is closed.

Then, the electric water pump 2 is operated, so that the coolant is circulated successively through the electric water pump 2, pump discharge passage 11, block-side water jacket 52a, head-side water jacket 51a, engine outflow passage 12, warm-up return passage 14, thermostat device 4, and the electric water pump 2, in the order of description.

Thus, since the circulating coolant bypasses the radiator 3, the coolant is not cooled by the radiator 3, and the engine 5 is warmed up.

At this time, as control of the electric water pump 2, the rotational speed of the electric water pump 2 is set low, so that the discharge flow rate is reduced, as described above. When the flow rate is low, the momentum of the coolant current is reduced, so that the coolant that flows in through the warm-up inflow port 42 of the thermostat device 4 flows out through the slit 62 before reaching the thermostatic element 44a, as indicated by outlined arrow LF in FIG. 4. Namely, when the flow rate is low, the coolant from the warm-up inflow port 42 flows down or drops from a distal end of the guide portion 14d, and is directed toward the slit 62. Further, since the outflow portion 45 of the thermostat device 4 is connected with the admission port of the electric water pump 2, the outflow of the coolant from the slit 62 is promoted, due to a negative pressure of the electric water pump 2. Accordingly, the coolant warmed by the engine 5 is less likely or unlikely to hit or contact with the thermostatic element 44a, and the valve 44c can be made less likely or unlikely to be unnecessarily opened.

Then, if the coolant temperature detected based on the output signal of the water temperature sensor 101 is increased, and reaches a warm-up completion temperature, the rotational speed of the electric water pump 2 is set high, and the discharge flow rate is increased, as described above, as control of the electric water pump 2 after completion of warm-up. When the flow rate is high, the momentum of the coolant current is increased, so that the coolant flowing from the warm-up inflow port 42 of the thermostat device 4 is guided by the guide portion 14d, and reaches the thermostatic element 44a, as indicated by outlined arrow HF of FIG. 4. Namely, the coolant warmed by the engine 5 can be brought into contact with the thermostatic element 44a, so that the valve 44c can be opened with good response.

In this case, circulation of the coolant indicated by arrows of one-dot chain lines in FIG. 1 is performed, in addition to circulation of the coolant indicated by arrows of solid lines in FIG. 1. Namely, the coolant is also circulated successively through the electric water pump 2, pump discharge passage 11, block-side water jacket 52a, head-side water jacket 51a, engine outflow passage 12, radiator 3, radiator return passage 13, thermostat device 4, and the electric water pump 2, in the order of description. Therefore, the coolant that has flowed through the warm-up return passage 14 and the coolant that has flowed through the radiator return passage 13 both flow into the thermostat device 4. Then, a part of the coolant flows through the radiator 3, and heat of the coolant is released to the atmosphere.

In this embodiment, the cooling system includes the guide portion 14d that guides the coolant flowing from the warm-up inflow port 42 toward the thermostatic element 44a, and the slit 62 provided in the outflow portion 45 and located between the guide portion 14d and the thermostatic element 44a, as described above. With this arrangement, during warm-up, it is possible to permit the coolant to flow out through the slit 62, before the coolant flowing from the warm-up inflow port 42 reaches the thermostatic element 44a, by reducing the discharge flow rate of the electric water pump 2, and reducing the momentum of the coolant current. Thus, during warm-up, the coolant that has been warmed is less likely or unlikely to hit or contact with the thermostatic element 44a and open the valve 44c, so that early warm-up can be achieved. Accordingly, the fuel consumption rate can be improved. After completion of warm-up, the discharge flow rate of the electric water pump 2 is increased, and the momentum of the coolant current is increased, so that the coolant flowing from the warm-up inflow port 42 can reach the thermostatic element 44a via the guide portion 14d. Thus, the warmed coolant can be brought into contact with the thermostatic element 44a. As a result, the valve 44c can be opened with good response, after completion of warn-up, so that overheating can be suppressed. Consequently, it is possible to suppress overheating, while assuring early warm-up.

Also, in this embodiment, the coolant flows into the electric water pump 2 from the outflow portion 45 of the thermostat device 4; therefore, outflow of the coolant through the slit 62 is promoted due to a negative pressure of the electric water pump 22, and the coolant warmed during warm-up can be made less likely or unlikely to hit or contact with the thermostatic element 44a.

It is to be understood that the embodiment disclosed herein is exemplary in all aspects, and does not provide a basis for limited interpretation. Accordingly, the technical scope of this disclosure should not be interpreted solely based on the above-described embodiment, but is defined based on the statement of the appended claims. The technical scope of the disclosure also includes all changes within the meaning and range of the claims and equivalents thereof.

While the disclosure is applied to the cooling system for the engine for the automobile in the illustrated embodiment, the disclosure may be applied to cooling systems other than those of engines for automobiles.

In the illustrated embodiment, a heater core, and other devices, may be provided in the coolant circulation circuit 10.

This disclosure may be used in a cooling system for an internal combustion engine including a thermostat device that switches flow of coolant of the engine which is circulated by an electric water pump.

Claims

1. A cooling system for an internal combustion engine comprising:

a radiator connected with the internal combustion engine via a first outflow passage;

a thermostat device connected with the radiator via a second outflow passage, connected with the internal combustion engine, the thermostat device being connected with the first outflow passage via a third outflow passage,

the thermostat device including a first inflow port connected with the second outflow passage, a second inflow port connected with the third outflow passage, a valve controlling a flow rate of a coolant from the radiator, a thermostatic element that opens and closes the valve according to a temperature of the coolant, an outflow portion through which the coolant flows to the internal combustion engine, a guide portion that guides the coolant flowing through the second inflow port toward the thermostatic element, and a slit flowing out the coolant from between the guide portion and the thermostatic element to the outflow portion; and

an electric water pump configured to circulate the coolant.

2. The cooling system according to claim 1, wherein the electric water pump is provided such that the coolant from the outflow portion of the thermostat device flows into the electric water pump.

3. The cooling system according to claim 1, wherein

the thermostat device includes a coil spring that biases the valve to close, and a frame supports a lower end portion of the coil spring, and

the slit is provided on the frame.

4. The cooling system according to claim 2, wherein the thermostat device is mounted on upper portion of the electric water pump.

5. A thermostat device for being provided in a cooling system that cools an internal combustion engine,

the cooling system including a radiator connected with the internal combustion engine via a first outflow passage, a thermostat device connected with the radiator via a second outflow passage, connected with the internal combustion engine, the thermostat device being connected with the first outflow passage via a third outflow passage, and an electric water pump configured to circulate a coolant,

the thermostat device comprising: a first inflow port connected with the second outflow passage; a second inflow port connected with the third outflow passage; a valve controlling a flow rate of the coolant from the radiator; a thermostatic element that opens and closes the valve according to a temperature of the coolant; an outflow portion through which the coolant flows to the internal combustion engine; a guide portion that guides the coolant flowing through the second inflow port toward the thermostatic element; a coil spring biasing the valve to close; and a frame supporting a lower end portion of the coil spring, having a slit that flows out the coolant from between the guide portion and the thermostatic element to the outflow portion.