JP2009097352A - Engine cooling system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine cooling system achieving reduction of fuel consumption in cold starting and also suppressing response delay of valve opening operation of a thermostat valve when shifting to a high load operation immediately after cold starting. <P>SOLUTION: This engine cooling system 1 includes: a first thermostat valve 25 arranged upstream of a water pump 15 in a main cooling water circuit 85, circulating cooling water to the side of a main cooling water passage when the valve is opened, and circulating the cooling water to the side of a first bypass passage 17 when the valve is closed; and a second thermostat valve 27 arranged downstream of the water pump 15, circulating the cooling water to the side of the main cooling water passage when the valve is opened, and circulating the cooling water to the side of a second bypass passage 23 when the valve is closed. The valve opening start temperature of the first thermostat valve 25 and the fully opening temperature thereof are set respectively higher than those of the second thermostat valve 27. When the temperature of the cooling water is below a first predetermined temperature T1, a rate of change in a cooling water flow rate when the second thermostat valve 27 is opened is set lower than that when the temperature of the cooling water is higher than the first predetermined temperature T1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an engine cooling apparatus.

  Conventionally, a water jacket is formed on each of the cylinder block and the cylinder head, and when the temperature of the cooling water is low, the cooling water is circulated only through the water jacket of the cylinder head, bypassing the water jacket of the cylinder block, and further, An engine cooling device that circulates cooling water through a radiator when the temperature of the engine becomes high is known (for example, Patent Documents 1 and 2). According to this engine cooling device, the heat exchange between the cylinder head and the cooling water is actively performed at the time of cold start, so that the temperature of the cooling water can be raised quickly, and the water jacket of the cylinder block has the cooling water. Therefore, the cylinder liner temperature of the cylinder block can be quickly raised. Therefore, the warm-up operation at the time of cold start can be completed quickly, and the fuel consumption in the cylinder block can be reduced.

  This type of engine cooling device switches the flow of cooling water to the cylinder block or the water jacket of the cylinder head according to the temperature of the cooling water, etc. separately from the main thermostat valve that controls the flow of cooling water to the radiator. A sub thermostat valve is provided, and the sub thermostat valve is opened when the temperature of the cooling water or the like exceeds a predetermined temperature, and the cooling water is circulated to the water jacket of the cylinder block. Thereby, since it is suppressed that the heated cylinder block becomes high temperature too much, the increase in the oil consumption in a cylinder block, the burning of a cylinder liner, etc. can be suppressed.

As such a sub-thermostat valve, for example, an electromagnetic type is used in Patent Document 1, but using an electromagnetic thermostat valve increases the cost of the cooling device and makes circuit layout difficult. A wax / pellet type thermostat valve (hereinafter simply referred to as a thermostat valve) containing a wax (thermal expansion body) is often used. The basic configuration of the thermostat valve is as follows. In other words, a valve seat having a flow hole for circulating cooling water, and a valve body in which wax is incorporated and a spring is attached, the valve body is separated from the valve seat by the expansion force of the wax. While opening the valve passage between the valve seat and the valve seat, the valve body is brought into contact with the valve seat by the biasing force of the spring to close the flow hole, thereby opening and closing the valve.
Japanese Patent Laid-Open No. 10-110654 JP-A-6-193443

  By the way, since the wax built in the thermostat valve has a predetermined heat capacity, it does not expand immediately even if it is immersed in high-temperature cooling water, and has the property of starting to expand after it has sufficiently warmed itself. is doing. For this reason, in the engine cooling device, even when high-temperature cooling water flows into the sub thermostat valve, the sub thermostat valve does not open immediately, so that the response to the cylinder block cooling request may be delayed.

  Such a characteristic of the wax is that, for example, in the case of low load operation until the warm-up operation is completed after starting the engine, the wax gradually warms in the process of gradually raising the temperature of the cooling water, and the cooling water rises. There is no problem because the coolant flow rate at the time of valve opening changes with temperature. However, for example, when a vehicle is parked in a service area on a highway and then merged into the main lane, when the engine is started and the engine is shifted to a high-load high-speed operation before the warm-up operation is completed, The following problems occur due to the characteristics.

  When shifting to a high-load high-rotation operation during a cold start, a very high load is applied to the cylinder block, and the cylinder liner temperature is quickly raised. At this time, since the temperature of the cylinder head also rises, the cooling water immediately becomes high temperature, but it takes time for the wax incorporated in the sub thermostat valve to expand, and despite the fact that the cylinder liner temperature is high, The cooling water does not flow through the water jacket of the cylinder block. If the sub thermostat valve is not opened when the cylinder block needs to be cooled in this way, oil consumption in the cylinder block deteriorates, and in the worst case, the cylinder liner may be seized.

  Therefore, in order to suppress the response delay of the opening operation of the sub thermostat valve, it is possible to set the opening temperature of the sub thermostat valve to be low and to distribute the cooling water to the water jacket of the cylinder block at the initial stage of cold start. Conceivable. However, if cooling water is circulated through the water jacket when the temperature of the cylinder block is not high, the temperature rise of the cylinder block is not promoted, so the oil shear resistance does not decrease, and the cylinder liner and piston Since the resistance is not reduced, fuel consumption is deteriorated.

  The present invention has been made in view of such points, and an object of the present invention is to reduce fuel consumption at the time of cold start in an engine cooling device and shift to high load operation immediately after cold start. It is an object of the present invention to provide a technique for suppressing a response delay in the opening operation of a thermostat valve.

  The first invention is provided in the main cooling water circuit in which the water jacket of the cylinder block, the water jacket of the cylinder head, the radiator, and the water pump are interposed in this order in the circulating direction of the cooling water, and the main cooling water circuit, A first bypass passage that bypasses the radiator, and a second bypass passage that branches from the downstream side of the water pump of the main coolant circuit and communicates with the water jacket of the cylinder head, bypassing the water jacket of the cylinder block An engine cooling device for circulating cooling water to the first and second bypass passages during cold start, provided on the upstream side of the water pump in the main cooling water circuit, and opened and closed according to the temperature of the cooling water When the valve is opened, the cooling water is circulated to the main cooling water circuit side, and when the valve is closed, the cooling water is supplied to the first cooling water circuit. A first thermostat valve that circulates to the bypass path side, and provided on the downstream side of the water pump of the main cooling water circuit, opens and closes according to the temperature of the cooling water, and when the valve is opened, the cooling water is moved to the main cooling water circuit side. A second thermostat valve that circulates cooling water to the second bypass passage side when the valve is closed, and the valve opening start temperature of the first thermostat valve is higher than the valve opening start temperature of the second thermostat valve. Is set to be higher, and the fully open temperature of the first thermostat valve is set to be higher than the fully open temperature of the second thermostat valve, and the cooling water when the second thermostat valve is opened in accordance with the temperature change of the cooling water. When the flow rate change rate is lower than the first predetermined temperature, which is lower than the opening temperature of the first thermostat valve, the temperature is higher than the first predetermined temperature. And it is characterized in that it is set to be small.

  In the first invention, the second thermostat valve opens when the temperature of the cooling water is low, and when the temperature of the cooling water is lower than the first predetermined temperature, the temperature of the cooling water is equal to or higher than the first predetermined temperature. The rate of change in the coolant flow rate at the time of valve opening is set smaller than in the case of. Thus, by opening the second thermostat valve when the temperature of the cooling water is low, it is possible to provide a standby temperature region in which the thermal expansion body starts to expand immediately when the temperature of the cooling water rises. Thereby, since the responsiveness of the 2nd thermostat valve with respect to the temperature change of a cooling water increases, even if the temperature of a cooling water rises rapidly, a cooling water can be distribute | circulated immediately to the water jacket of a cylinder block. Therefore, it is possible to suppress a decrease in reliability due to a delay in temperature response of the cylinder liner during a high load operation immediately after the engine is started.

  Further, when the temperature is lower than the first predetermined temperature, the flow rate of the cooling water to the water jacket of the cylinder block is reduced, so that the cylinder block can be kept at a high temperature during cold start, and the cylinder head and the cooling water Since heat exchange is actively performed, the temperature of the cooling water can be raised quickly. Therefore, the warm-up operation at the time of cold start can be completed quickly, and the fuel consumption at the time of cold start can be reduced.

  According to a second invention, in the first invention, the second thermostat valve has a valve seat in which a flow hole for flowing cooling water to the main cooling water circuit side is formed, and a valve body. A valve passage is formed between the valve seat and the valve body for circulating cooling water through the flow hole, and the valve body is separated from the valve seat when the second thermostat valve is opened. When the second thermostat valve is closed, the coolant is circulated by closing the second thermostat valve by closing the second thermostat valve by opening the valve passage by moving away from the valve and closing the flow hole. The cooling water is circulated to the second bypass passage side, and the area change rate of the valve passage when the second thermostat valve is opened due to the temperature change of the cooling water is the temperature of the cooling water is the first predetermined temperature. Is less than the first predetermined temperature, Kiyori also characterized in that it is smaller.

  According to the second invention, when the temperature of the cooling water is lower than the first predetermined temperature, the flow rate of the cooling water to the water jacket of the cylinder block is reduced by reducing the area change rate of the valve passage of the second thermostat valve. The amount can be reduced. Therefore, it is possible to reduce fuel consumption during cold start without complicating the structure of the cooling device.

  According to a third invention, in the second invention, the valve seat has an annular valve seat plate in which the flow hole is formed, and the valve body is formed when the second thermostat valve is closed. An annular bottom wall portion that abuts the valve seat plate, and extends in the valve body displacement direction from the inner peripheral edge portion of the bottom wall portion, and inclines radially inward as the distance from the inner peripheral edge portion increases. A substantially cylindrical standing wall portion that can be inserted and removed in the body displacement direction, and the valve passage is formed between the valve seat plate and the standing wall portion, and the standing wall portion is the second wall portion. When the thermostat valve is opened, it is displaced away from the valve seat plate to open the valve passage. When the length of the vertical wall portion in the valve body displacement direction is the first predetermined temperature, the vertical wall portion is the flow hole. It is characterized by being set to such a length that it can be removed from.

  According to the third invention, when the cooling water temperature is lower than the first predetermined temperature, the valve body of the second thermostat valve simply has a substantially cylindrical valve body wall portion inclined inward. Only the rate of change in the valve passage area can be reduced while displacing the valve body with the temperature change of the cooling water.

  According to a fourth invention, in the first invention, the flow rate of the cooling water when the second thermostat valve is opened is set to be constant when the temperature of the cooling water is lower than the first predetermined temperature. It is characterized by that.

  Thereby, when the temperature is lower than the first predetermined temperature, the flow rate of the cooling water to the water jacket of the cylinder block becomes smaller, so that the cylinder block can be kept at a higher temperature. Therefore, it is possible to further reduce fuel consumption during cold start.

  In a fifth aspect based on the fourth aspect, the second thermostat valve has a valve seat having a flow hole for allowing the cooling water to flow to the main cooling water circuit side, and a valve body. A valve passage is formed between the valve seat and the valve body for circulating cooling water through the flow hole, and the valve body is separated from the valve seat when the second thermostat valve is opened. When the second thermostat valve is closed, the coolant is circulated by closing the second thermostat valve by closing the second thermostat valve by opening the valve passage by moving away from the valve and closing the flow hole. The cooling water is circulated to the second bypass passage side by the above, and the area of the valve passage when the second thermostat valve is opened is constant when the temperature of the cooling water is lower than the first predetermined temperature. It is characterized by being set to.

  According to the fifth invention, when the temperature of the cooling water is lower than the first predetermined temperature, the flow of the cooling water to the water jacket of the cylinder block is made constant by making the area of the valve passage of the second thermostat valve constant. The amount can be reduced. Therefore, it is possible to further reduce fuel consumption during cold start without complicating the structure of the cooling device.

  In a sixth aspect based on the fifth aspect, the valve seat has an annular valve seat plate in which the flow hole is formed, and the valve body is formed when the second thermostat valve is closed. An annular bottom wall that abuts the valve seat plate, and the valve passage is formed between the valve seat plate and the bottom wall portion, and the valve passage includes the valve passage In order to restrict the change in the area of the cylinder, a cylindrical restriction wall portion extending in the valve body displacement direction is formed so as to surround the bottom wall portion, and the length of the restriction wall portion in the valve body displacement direction is the first predetermined value. The temperature is set such that the bottom wall portion can be removed from the limiting wall portion at the time of temperature.

  Thus, when the temperature of the cooling water is less than the first predetermined temperature, the valve body is accompanied by a change in the temperature of the cooling water when the temperature of the cooling water is less than the first predetermined temperature. Only a change in the area of the valve passage can be regulated while displacing the valve.

  According to the present invention, the responsiveness of the second thermostat valve to the temperature change of the cooling water can be improved by opening the second thermostat valve from the state where the temperature of the cooling water is low. It is possible to suppress a decrease in reliability due to a delay in the temperature response of the cylinder liner during load operation, and when the temperature is lower than the first predetermined temperature, the amount of cooling water flowing to the water jacket of the cylinder block is reduced. The warm-up operation can be completed quickly, and the fuel consumption can be reduced during cold start.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
-Overall configuration of cooling device-
FIG. 1 schematically shows a configuration of an engine cooling device 1 according to the present embodiment. The cooling device 1 includes water jackets 9 and 11 serving as cooling water passages formed in a cylinder block 5 and a cylinder head 7 constituting a main body 3 of the engine, and a front portion of a vehicle for cooling the cooling water by outside air. A water pump 15 that circulates cooling water, and first and second thermostat valves 25 and 27 that open when the temperature of the cooling water rises to switch the circulation system of the cooling water. I have. The main cooling water circuit 85 referred to in the present invention includes a water jacket 9 of the cylinder block 5, a water jacket 11 of the cylinder head 7, a radiator 13 and a water pump 15 in this order in the circulating direction of the cooling water. is there.

  The water jacket 9 of the cylinder block 5 is formed over substantially the entire cylinder row direction of the cylinder block 5 so as to surround the outer periphery of the four cylinders s1 to s4.

  The water jacket 9 of the cylinder block 5 is connected to the cylinder head 7 via a communication hole 5 a formed in the top deck of the cylinder block 5 and a communication hole 7 a formed in the bottom deck of the cylinder head 7. The water jacket 11 is communicated. For this reason, the cooling water flowing through the water jacket 9 of the cylinder block 5 sequentially flows to the water jacket 11 of the cylinder head 7.

  The water jacket 11 of the cylinder head 7 is formed over substantially the entire cylinder row direction of the cylinder head 7 so as to wrap around the intake and exhaust ports and plug holes (not shown) of the cylinders s1 to s4. Yes.

  The outlet 11a of the water jacket 11 of the cylinder head 7 and the suction port 15a of the water pump 15 are connected via the first thermostat valve 25 by two routes. The first route is a first cooling water passage 19 connecting the outlet 11a of the water jacket 11 of the cylinder head 7 and the radiator 13, and a second cooling water passage 21 connecting the radiator 13 and the first thermostat valve 25. And the third cooling water passage 17 connecting the first thermostat valve 25 and the suction port 15a of the water pump 15 in this order.

  Further, the second route is formed in the first thermostat valve 25 when the first thermostat valve 25 is closed, and a first bypass passage (valve passage) 71 (see FIG. 5) that bypasses the radiator 13 and the third route. It passes through the cooling water passage 17. In addition, in the third cooling water passage 17, a heater core 29 as a heating heat exchanger that introduces cooling water and exchanges heat with the conditioned air to form heating air, and cooling water and a transmission (not shown). And an oil warmer 31 that exchanges heat with the lubricating oil.

  The discharge port 15 b of the water pump 15 is connected to the inlet 9 a of the water jacket 9 of the cylinder block 5 through the second thermostat valve 27. Further, the discharge port 15 b of the water pump 15 is also connected to the inlet 11 b of the water jacket 11 of the cylinder head 7 by the second bypass passage 23. The second bypass passage 23 branches via a second thermostat valve 27 on the downstream side of the water pump 15, bypasses the water jacket 9 of the cylinder block 5, and communicates with the water jacket 11 of the cylinder head 7.

  The overall flow of the cooling water in the engine cooling device 1 configured as described above is provided on the downstream side of the first thermostat valve 25 and the water pump 15 provided on the upstream side of the water pump 15 of the main cooling water circuit 85. It changes as schematically shown in FIGS. 2 to 4 according to the opening and closing of the second thermostat valve 27.

  FIG. 2 shows the flow of cooling water when both the first thermostat valve (main thermostat valve) 25 and the second thermostat valve (sub thermostat valve) 27 are open. The cooling water discharged from the water pump 15 passes through the second thermostat valve 27 and is sent to the water jacket 9 of the cylinder block 5. Then, the cooling water flows in the water jacket 9 of the cylinder block 5 and also flows in the water jacket 11 of the cylinder head 7 and reaches the radiator 13 through the first cooling water passage 19. The cooling water cooled by the radiator 13 returns to the water pump 15 through the second cooling water passage 21, the first thermostat valve 25, and the third cooling water passage 17 in order. That is, when both the first and second thermostat valves 25 and 27 are open, the cooling water circulates through the main cooling water circuit 85.

  FIG. 3 shows the flow of cooling water when both the first and second thermostat valves 25 and 27 are closed. The cooling water discharged from the water pump 15 passes through the second thermostat valve 27 and the second bypass passage 23 in order, and is sent to the water jacket 11 of the cylinder head 7. Then, the cooling water flowing out from the water jacket 11 of the cylinder head 7 returns to the water pump 15 through the first bypass passage 71 and the third cooling water passage 17 in order.

  FIG. 4 shows the flow of cooling water when the first thermostat valve 25 is closed and the second thermostat valve 27 is open. The cooling water discharged from the water pump 15 passes through the second thermostat valve 27 and is sent to the water jacket 9 of the cylinder block 5. The cooling water flows in the water jacket 9 of the cylinder block 5 and also flows in the water jacket 11 of the cylinder head 7. The cooling water flowing out from the water jacket 11 of the cylinder head 7 returns to the water pump 15 through the first bypass passage 71 and the third cooling water passage 17 in order.

-Configuration of thermostat valve-
Hereinafter, the configuration of the first and second thermostat valves 25 and 27 will be described in detail.

<First thermostat valve>
The first thermostat valve 25 is a wax / pellet type thermostat valve that opens and closes according to the temperature of the cooling water. FIG. 5 shows a state when the valve is closed, and FIG. 6 shows a state when the valve is opened. Yes. The first thermostat valve 25 is attached in a pipe-shaped housing 33 that constitutes a part of the second cooling water passage 21, and the cooling water is supplied via the valve passage 65 when the first thermostat valve 25 is opened. When the first thermostat valve 25 is closed, the cooling water is circulated to the third cooling water passage 17 via the first bypass passage 71 when the first cooling thermostat valve 25 is closed. A thermostat base part 39 for fixing the first thermostat valve 25 to the housing 33, and a thermostat main body part relative to the thermostat base part 39 in a valve body displacement direction to be described later. 41.

  The thermostat base portion 39 is attached to the housing 33 and forms a part of the main valve portion 35, and a spring provided on the cylinder head 7 side (one side in the valve body displacement direction) from the valve seat 43. A support portion 45 and a shaft support portion 47 provided on the opposite side of the valve seat 43 from the spring support portion 45 (the other side in the valve body displacement direction) are provided.

  The valve seat 43 includes an annular support plate 43a, an annular valve seat plate 43c, and a substantially cylindrical standing wall portion 43b.

  The support plate 43 a is fixed to the housing 33 by embedding the outer peripheral edge of the support plate 43 a in the housing 33. The valve seat plate 43c has an outer diameter smaller than the inner diameter of the support plate 43a, and is arranged in parallel to the support plate 43a and on one side of the valve body displacement direction with respect to the support plate 43a. The inner peripheral edge of the valve seat plate 43c defines a flow hole 49 for flowing the cooling water to the main cooling water circuit 85 side. The standing wall 43b connects the inner periphery of the support plate 43a and the outer periphery of the valve seat plate 43c over the entire periphery. In other words, the valve seat 43 has a flange (support plate 43a) extending outward at the other end portion in the valve body displacement direction and a flange (valve seat) extending inward at the one end portion in the valve body displacement direction. It has a substantially conical cylinder shape with a plate 43c).

  The spring support portion 45 and the shaft support portion 47 are attached to the housing 33 via a support plate 43a. These support portions 45 and 47 are both frame structures and have a structure that does not block the flow of cooling water.

  On the other hand, the thermostat main body 41 includes a piston rod 51 and a temperature sensitive case 53.

  The piston rod 51 extends in the valve body displacement direction, and the other end portion in the valve body displacement direction is fixed to the shaft support portion 47 and passes through the flow hole 49 perpendicular to the valve seat plate 43c. Are arranged as follows. A bottomed cylindrical seal member 57 is attached to one end of the piston rod 51 in the valve body displacement direction.

  The temperature-sensitive case 53 has a cylindrical body portion 59 having a bottom and a lid, and a through-hole 59a is formed in the bottom portion (end portion on the other side of the valve body displacement direction) and a lid portion (one side in the valve body displacement direction). On the side), a rod portion 59b extending in the cylindrical axis direction is projected. The piston rod 51 covered with the seal member 57 is inserted into the through hole 59a, so that the temperature sensitive case 53 can move along the piston rod 51 in the rod axis direction (valve element displacement direction). ing. Between the seal member 57 and the temperature sensitive case 53, a wax 55 which is a thermal expansion body is filled.

  Furthermore, the temperature-sensitive case 53 includes a substantially annular plate-shaped main valve body 61 in the body portion 59 and a bypass valve body 63 in the rod portion 59b.

  The main valve body 61 has an inner peripheral edge portion fixed to the body portion 59 and an outer diameter substantially the same as that of the valve seat plate 43c. The main valve element 61 constitutes the main valve portion 35 together with the valve seat 43 and is displaced in the valve opening / closing direction (valve element displacement direction) as the temperature sensing case 53 moves. A main spring 67 supported by the spring support portion 45 is attached to one side surface of the main valve body 61 in the valve body displacement direction. Thereby, the temperature sensitive case 53 is always urged by the main spring 67 to the other side in the valve body displacement direction.

  The bypass valve body 63 is movably attached to the rod portion 59b and has an outer diameter larger than the inner diameter of the pipe-shaped housing 69 on the cylinder head 7 side, and the step portion of the housing 69 on the cylinder head 7 side. The bypass valve part 37 is comprised with 69a. The bypass valve body 63 is connected to the lid portion of the body portion 59 by a bypass spring 73. The bypass spring 73 is constantly urged to one side in the valve body displacement direction by the bypass spring 73, and is a stopper ring fixed to the rod portion 59b. 75 prevents the rod portion 59b from coming off.

  The wax 55 expands when the temperature of the cooling water transmitted through the temperature-sensitive case 53 increases, and contracts when the temperature of the cooling water decreases. The filling amount of the wax 55 is such that when the temperature of the cooling water is equal to or higher than the second predetermined temperature T2, the main valve body 61 separates from the valve seat plate 43c against the biasing force of the main spring 67 by the expansion force of the wax 55. A value is set such that the main valve body 61 comes into contact with the valve seat plate 43c by the urging force of the main spring 67 when the valve body is displaced in one direction of the valve body and the temperature of the cooling water is lower than the second predetermined temperature T2. Has been.

  When the temperature of the cooling water is lower than the second predetermined temperature T2, the first thermostat valve 25 configured as described above closes the main valve portion 35 by the urging force of the main spring 67 as shown in FIG. At the same time, the bypass valve portion 37 is opened to allow the coolant to flow through the first bypass passage 71. More specifically, it is as follows.

  When the temperature of the cooling water is lower than the second predetermined temperature T2, the temperature-sensitive case 53 does not move because the wax does not expand. For this reason, the main valve body 61 contacts the valve seat plate 43 c by the urging force of the main spring 67 and closes the flow hole 49, whereby the main valve portion 35 is closed. At this time, the bypass valve body 63 is displaced to the other side in the valve body displacement direction so as to be separated from the stepped portion 69a of the housing 69, and the valve passage 71 between the housing 69 and the stepped portion 69a is opened, whereby the bypass valve The part 37 opens. As a result, the first thermostat valve 25 is closed, and the coolant flows through the first bypass passage 71 to the third coolant passage 17 side.

  On the other hand, when the temperature of the cooling water is equal to or higher than the second predetermined temperature T2, the first thermostat valve 25 opens the main valve portion 35 by the expansion force of the wax 55 and bypass valve portion 37 as shown in FIG. Is closed to allow the cooling water to flow to the first cooling water passage 19 side. More specifically, it is as follows.

  Since the wax expands when the temperature of the cooling water is equal to or higher than the second predetermined temperature T2, the temperature sensing case 53 moves to one side in the valve body displacement direction against the urging force of the main spring 67. For this reason, the main valve body 61 is displaced to one side in the valve body displacement direction so as to be separated from the valve seat plate 43 c by the expansion force of the wax 55, thereby opening the valve passage 65 between the valve seat plate 43 c and cooling to the flow hole 49. Water enters a state in which water flows and the main valve portion 35 opens. At this time, when the bypass valve body 63 contacts the stepped portion 69 a of the housing 69, the bypass valve portion 37 is closed. As a result, the first thermostat valve 25 is opened, and the cooling water flows through the first cooling water passage 19 and the second cooling water passage 21 to the third cooling water passage 17 (main cooling water circuit side 85).

  Here, the valve passage 65 of the main valve portion 35 has a valve seat plate 43c as a result of the main valve body 61 moving to one side in the valve body displacement direction in order to allow cooling water to flow through the flow hole 49 of the valve seat plate 43c. Between the valve seat plate 43c and the main valve body 61 in the valve body displacement direction (valve opening / closing direction), that is, the valve seat plate 43c. Increases in proportion to the amount of displacement of the main valve body 61 with respect to.

<Second thermostat valve>
The second thermostat valve 27 is different from the first thermostat valve 25 in the shape of the main valve body 79. Hereinafter, differences from the first thermostat valve 25 will be described.

  The second thermostat valve 27 is a wax / pellet type thermostat valve that opens and closes according to the temperature of the cooling water. FIG. 7 shows a state when the valve is closed, and FIG. 8 shows a state when the valve is opened. Yes. The second thermostat valve 27 is mounted in a pipe-shaped housing 77 that constitutes a connection portion between the water pump 15 and the water jacket 9 of the cylinder block 5, and the cooling water is supplied when the second thermostat valve 27 is opened. When the second thermostat valve 27 is closed, the main valve portion 35 that circulates to the water jacket 9 side (main cooling water circuit side) of the cylinder block 5 through the passage 81 and the second bypass through the valve passage 87. And a bypass valve portion 37 that circulates to the passage 23 side. The wax 55 of the second thermostat valve 27 is set so as to expand when the temperature of the cooling water is equal to or higher than the third predetermined temperature T3 that is extremely lower than the second predetermined temperature T2.

  The second thermostat valve 27 includes a main valve body 79 having a substantially conical cylindrical shape in the body portion 59 of the temperature sensitive case 53. The main valve body 79 constitutes the main valve portion 35 together with the valve seat 43, and has a substantially annular top wall portion 79a, an annular bottom wall portion 79c, and a substantially cylindrical standing wall portion 79b. Yes.

  The top wall portion 79a has an outer shape whose inner peripheral edge portion is fixed to the body portion 59 and smaller than the inner diameter of the valve seat plate 43c. The bottom wall 79c has the same shape and size as the valve seat plate 43c, and is disposed in parallel to the top wall 79a and on the other side of the valve body displacement direction (opposite to the cylinder block 5 side) than the top wall. ing. The standing wall 79b connects the outer periphery of the top wall 79a and the inner periphery of the bottom wall 79c over the entire periphery.

  The standing wall portion 79b is inclined inwardly in the cylinder radial direction from the bottom wall portion 79c side in the valve body displacement direction toward the top wall portion 79a side, that is, as the distance from the inner peripheral edge portion of the bottom wall portion 79c increases. 49 can be inserted and removed in the valve body displacement direction (valve opening / closing direction). The length of the standing wall portion 79b in the valve body displacement direction is such that when the temperature of the cooling water reaches the first predetermined temperature T1 lower than the second predetermined temperature T2 and higher than the third predetermined temperature T3, the standing wall portion 79b has a flow hole. It is set to a length that can be removed from 49. Further, the inclination angle of the standing wall portion 79b is a gentle inclination angle of 45 degrees or less with respect to the valve body displacement direction.

  A main spring 67 supported by the spring support 45 is attached to the other side surface of the top wall 79a in the valve body displacement direction, so that the temperature sensing case 53 is always on one side in the valve body displacement direction (on the cylinder block 5 side). ).

  When the temperature of the cooling water is lower than the third predetermined temperature T3, the second thermostat valve 27 configured as described above closes the main valve portion 35 by the urging force of the main spring 67 as shown in FIG. At the same time, the bypass valve portion 37 is opened to allow the coolant to flow to the second bypass passage 23 side. More specifically, it is as follows.

  When the temperature of the cooling water is lower than the third predetermined temperature T3, the wax does not expand and the temperature sensitive case 53 does not move. For this reason, the bottom wall portion 79c comes into contact with the valve seat plate 43c by the urging force of the main spring 67, and the standing wall portion 79b is inserted into the flow hole 49 to close the flow hole 49, whereby the main valve portion 35 is closed. . At this time, the bypass valve body 63 is displaced to one side in the valve body displacement direction so as to be separated from the stepped portion 23a of the second bypass passage 23. By opening the valve passage 87 to the stepped portion 23a, the bypass valve body 63 is bypassed. The valve part 37 opens. As a result, the second thermostat valve 27 is closed, and the cooling water flows to the second bypass passage 23 side.

  On the other hand, when the temperature of the cooling water is equal to or higher than the third predetermined temperature T3, the main valve portion 35 is opened by the expansion force of the wax 55 and the bypass valve portion 37 is closed, so that the cooling water is supplied to the water in the cylinder block 5. Distribute to jacket 9. More specifically, it is as follows.

  Since the wax expands when the temperature of the cooling water is equal to or higher than the third predetermined temperature T3, the temperature sensing case 53 moves to the other side in the valve body displacement direction against the urging force of the main spring 67. For this reason, when the temperature of the cooling water is equal to or lower than the first predetermined temperature T1, the upright wall portion 79b is displaced to the other side in the valve body displacement direction so as to come off (separate) from the valve seat plate 43c by the expansion force of the wax 55. The valve passage 81 between the plate 43c is opened and cooling water is circulated through the flow hole 49, and the main valve portion 35 is opened. At this time, the bypass valve body 63 is displaced toward the stepped portion 69a of the second bypass passage 23, so that the bypass valve portion 37 is slightly closed and opened. As a result, the second thermostat valve 27 is opened, and the cooling water flows to the water jacket 9 side of the cylinder block 5.

  Here, the valve passage 81 of the main valve portion 35 has a valve seat plate 43c as a result of the main valve body 79 moving to the other side in the valve body displacement direction in order to allow cooling water to flow through the flow hole 49 of the valve seat plate 43c. The passage area is not proportional to the amount of displacement of the main valve element 79 with respect to the valve seat plate 43c, but in the radial direction of the valve seat plate 43c. The valve seat plate 43c increases in proportion to the distance between the standing wall portion 79b. Further, since the inclination angle of the standing wall portion 79b is 45 degrees or less with respect to the displacement direction of the main valve body 79, the distance between the valve seat plate 43c and the standing wall portion 79b in the radial direction of the valve seat plate 43c is the valve body. The displacement is smaller than the displacement of the main valve element 79 relative to the valve seat plate 43c in the displacement direction. Then, when the temperature of the cooling water reaches the first predetermined temperature T1, the standing wall portion 79b comes out of the flow hole 49, so that the valve passage area of the main valve portion 35 is the same as that of the first thermostat valve 25, the valve seat plate 43c. Increases in proportion to the amount of displacement of the main valve element 79 with respect to. That is, the area change rate of the valve passage 81 when the second thermostat valve 27 is opened due to the temperature change of the cooling water is such that the temperature of the cooling water is the first when the temperature of the cooling water is lower than the first predetermined temperature T1. It is set smaller than when the temperature is equal to or higher than the predetermined temperature T1. Therefore, the cooling water flow rate change rate when the second thermostat valve 27 is opened is smaller when the temperature of the cooling water is lower than the first predetermined temperature T1 than when the temperature of the cooling water is equal to or higher than the first predetermined temperature T1. Become.

-Characteristics of thermostat valve-
Hereinafter, the characteristics of the first and second thermostat valves 25 and 27 will be described in detail.

  FIG. 9 is a diagram showing changes in the valve passage areas of the first and second thermostat valves 25 and 27 with respect to the temperature of the cooling water. The solid line in the figure shows the characteristics of the first thermostat valve 25, and the dotted line in the figure shows The characteristics of the second thermostat valve 27 are shown.

  As shown in FIG. 9, the valve opening start temperature (second predetermined temperature T2) of the first thermostat valve 25 is set higher than the valve opening start temperature (third predetermined temperature T3) of the second thermostat valve 27. The fully open (maximum open valve) temperature (fourth predetermined temperature T4) of the first thermostat valve 25 is set higher than the full open temperature (fifth predetermined temperature T5) of the second thermostat valve 27.

  Setting the valve opening start temperature of the first thermostat valve 25 higher than the valve opening start temperature of the second thermostat valve 27 prevents the cooling water from flowing into the water jacket 9 of the cylinder block 5 during low load operation. Because. If the first thermostat valve 25 is opened before the second thermostat valve 27, the cooling water cooled by the radiator 13 flows into the second thermostat valve 27, so that the second thermostat valve 27 cannot be opened, and the cylinder The cylinder block 5 becomes so hot that the oil consumption in the block 5 increases and the cylinder liner (not shown) seizes. Therefore, in the present embodiment, the second thermostat valve 27 is opened before the first thermostat valve 25 to prevent the cylinder block 5 from becoming hot.

  On the other hand, the reason why the fully open temperature of the first thermostat valve 25 is set to be higher than the fully open temperature of the second thermostat valve 27 is that the second thermostat valve 27 is fully opened before the first thermostat valve 25, and at the time of high load operation. This is to ensure a sufficient flow rate of the cooling water flowing through the water jacket 9 of the cylinder block 5. That is, at the time of high load operation in which the fuel consumption effect in the cylinder block 5 does not become a problem, the cooling water cooled by the radiator 13 is distributed to the water jackets 9 and 11 of the cylinder block 5 and the cylinder head 7 so that the entire main body 3 of the engine. Priority is given to the cooling effect.

  Here, it is desirable that the fourth predetermined temperature T4 is set to be 4 ° C. higher than the fifth predetermined temperature T5. The reason is as follows.

  The wax 55 incorporated in the thermostat valves 25 and 27 can adjust the valve opening start temperature or the full opening temperature by containing impurities, but an error of about plus or minus 2 ° C. inevitably occurs with respect to the set temperature. There is a case. Therefore, for example, when the difference between the fourth predetermined temperature T4 and the fifth predetermined temperature T5 is set to 3 ° C., the first thermostat valve 25 has an error of −2 ° C., and the second thermostat valve 27 is positive. If there is an error of 2 ° C., the full opening temperature of the second thermostat valve 27 becomes higher than the full opening temperature of the first thermostat valve 25, and the maximum opening amount of the second thermostat valve 27 during the high load operation is secured. It may not be possible. Therefore, by setting the difference between the fourth predetermined temperature T4 and the fifth predetermined temperature T5 to 4 ° C. or more, the first thermostat valve 25 has an error of −2 ° C., and the second thermostat valve 27 has an error of + 2 ° C. Even when the second thermostat valve 27 is provided, the maximum valve opening amount of the second thermostat valve 27 can be secured.

  The rate of change in the coolant flow rate when the second thermostat valve 27 is opened is smaller when the coolant temperature is lower than the first predetermined temperature T1 than when the coolant temperature is equal to or higher than the first predetermined temperature T1. Is set. The reason is as follows.

  In the cooling device 1 of the present embodiment, the opening of the second thermostat valve 27 is started when the temperature of the cooling water is a third predetermined temperature T3 that is lower than the first predetermined temperature T1. In this way, by opening the second thermostat valve 27 early, it is possible to provide a standby temperature region (X in FIG. 9) in which the wax 55 can expand immediately in response to the temperature rise of the cooling water. Therefore, it is possible to compensate for the disadvantage of the conventional wax / pellet type thermostat valve in which the valve opening is not started until the wax 55 itself is warmed. That is, when the cylinder block 5 becomes high temperature, the second thermostat valve 27 is opened from the low temperature stage so that the required amount of cooling water can flow through the water jacket 9 immediately.

  However, if the coolant is circulated through the water jacket 9 of the cylinder block 5 in a state where the cylinder block 5 is not at a high temperature, the temperature rise of the cylinder block 5 is not promoted. Therefore, when the temperature of the cooling water is lower than the first predetermined temperature T1, the rate of change in the cooling water flow rate when the second thermostat valve 27 is opened is reduced, so that the water jacket 9 of the cylinder block 5 to the water jacket 9 during cold start is reduced. The circulation of cooling water was reduced.

  Since the second thermostat valve 27 is a valve that controls the flow of the cooling water to the water jacket 9 of the cylinder block 5, it detects the cylinder liner temperature of the cylinder block 5 directly like the electromagnetic thermostat valve, and responds accordingly. In the present invention, the opening and closing of the second thermostat valve 27 is controlled by the temperature of the cooling water. The reason is as follows.

  When the second thermostat valve 27 is closed or when the amount of cooling water flowing through the water jacket 9 of the cylinder block 5 is small, the temperature of the cooling water substantially depends on the temperature of the cylinder head 7. Further, there is a correlation between the temperature of the cylinder head 7 and the cylinder liner temperature. Therefore, since the temperature of the cooling water and the cylinder liner temperature are also correlated, the cylinder liner temperature can be managed even if the opening and closing of the second thermostat valve 27 is controlled by the temperature of the cooling water.

-Action of cooling device-
The operation of the engine cooling apparatus 1 configured as described above will be described below.

  When the engine having a low cooling water temperature is cold-started, the first and second thermostat valves 25 and 27 are closed by the biasing force of the main spring 67 as shown in FIGS. As shown in FIG. 3, the cooling water discharged from the water pump 15 bypasses the water jacket 9 of the cylinder block 5, passes through the second thermostat valve 27 and the second bypass passage 23 in order, and reaches the cylinder head 7. It is sent to the water jacket 11. The cooling water flowing out from the water jacket 11 of the cylinder head 7 returns to the water pump 15 through the first bypass passage 71 and the third cooling water passage 17 in order.

  When the temperature of the cooling water rises to the third predetermined temperature T3 due to heat exchange with the cylinder head 7, the second thermostat valve 27 starts to open. When the main valve body 79 is displaced away from the valve seat 43 by the expansion force of the wax 55 built in the second thermostat valve 27, the valve passage 81 between the standing wall portion 79b and the valve seat plate 43c is gradually opened. The passage area increases. At this time, as shown in FIG. 10, most of the cooling water discharged from the water pump 15 is sent to the water jacket 11 of the cylinder head 7 through the second bypass passage 23 (thick arrow in FIG. 10). A small amount of cooling water is also sent to the water jacket 9 of the cylinder block 5 (thin arrow in FIG. 10).

  When the temperature of the cooling water further rises and reaches the first predetermined temperature T1, the main valve body 79 is displaced away from the valve seat 43 by the expansion force of the wax 55 of the second thermostat valve 27, and the standing wall portion 79b becomes the valve. The valve passage area is suddenly increased by slipping out of the seat plate 43c. At this time, the cooling water discharged from the water pump 15 is sent to the water jacket 9 of the cylinder block 5 as shown in FIG. 4, and is sent to the water jacket 11 of the cylinder head 7 through the communication holes 5a and 7a. It is done. Then, the cooling water that has flowed through the water jacket 11 of the cylinder head 7 bypasses the radiator 13, flows through the first bypass passage 71 and the first cooling water passage 17, and returns to the water pump 15.

  When the temperature of the cooling water further rises to the second predetermined temperature T2, the first thermostat valve 25 is opened by the expansion force of the wax 55 as shown in FIG. At this time, the cooling water discharged from the water pump 15 and flowing through the water jacket 9 of the cylinder block 5 and the water jacket 11 of the cylinder head 7 passes through the first cooling water passage 19 as shown in FIG. To.

-Effect-
In the present embodiment, the second thermostat valve 27 is opened when the temperature of the cooling water is low, and when the temperature of the cooling water is lower than the first predetermined temperature T1, the temperature of the cooling water is the first predetermined temperature. The cooling water flow rate change rate at the time of opening the valve is set to be smaller than when T1 or more. Thus, by opening the second thermostat valve 27 from when the temperature of the cooling water is low, it is possible to provide a standby temperature region X in which the wax 55 starts to expand immediately when the temperature of the cooling water rises. Thereby, since the responsiveness of the 2nd thermostat valve 27 with respect to the temperature change of a cooling water increases, even if the temperature of a cooling water rises rapidly, a cooling water can be immediately distribute | circulated to the water jacket 9 of the cylinder block 5. FIG. . Therefore, it is possible to suppress a decrease in reliability due to a delay in temperature response of the cylinder liner during a high load operation immediately after the engine is started.

  Further, when the temperature is lower than the first predetermined temperature T1, the circulation amount of the cooling water to the water jacket 9 of the cylinder block 5 is reduced, so that the cylinder block 5 can be kept at a high temperature during the cold start and the cylinder head 7 Since heat exchange with the cooling water is actively performed, the temperature of the cooling water can be raised quickly. Therefore, it is possible to reduce fuel consumption during cold start without complicating the structure of the cooling device 1.

  Furthermore, when the temperature of the cooling water is lower than the first predetermined temperature T1, the area change rate of the valve passage 81 of the main valve portion 35 of the second thermostat valve 27 is reduced, so that the water jacket 9 of the cylinder block 5 is supplied to the water jacket 9. Cooling water circulation can be reduced. Therefore, it is possible to reduce fuel consumption during cold start without complicating the structure of the cooling device 1.

  Moreover, when the temperature of the cooling water is lower than the first predetermined temperature, the main valve body 79 of the second thermostat valve 27 has a simple structure that simply includes a substantially cylindrical valve body wall 79b that is inclined inward. Only the rate of change in the valve passage area can be reduced while displacing the main valve element 79 with the temperature change of the water.

(Embodiment 2)
In the present embodiment, the structure of the valve seat 43 of the second thermostat valve 27 is different from that of the first embodiment. Hereinafter, differences from the first embodiment will be described.

-Configuration of thermostat valve-
As shown in FIG. 11, a restriction wall portion 83 is formed on the valve seat plate 43 c of the second thermostat valve 27. The restricting wall 83 is a cylindrical body that extends from the outer peripheral edge of the valve seat plate 43c to the other side in the valve body displacement direction, and is a valve passage 81 formed between the bottom wall 79c and the valve seat plate 43c. In order to regulate the area change, the bottom wall 79c is surrounded. The length of the restricting wall portion 83 in the valve body displacement direction is such that the bottom wall portion 79c that is in contact with the valve seat plate 43c at the start of valve opening is displaced to the other side in the valve body displacement direction by the expansion force of the wax 55. The length is set such that the water can be removed from the limiting wall 83 when the temperature of the water reaches the first predetermined temperature T1.

  The second thermostat valve 27 configured as described above causes the cooling water to flow to the water jacket 9 side of the cylinder block 5 when the temperature of the cooling water is equal to or higher than the third predetermined temperature T3. Until the first predetermined temperature T1 is reached, the restriction wall 83 restricts the change in the area of the valve passage 81. Therefore, the area of the valve passage 81 when the second thermostat valve 27 is opened is determined by the temperature of the cooling water. When the temperature is lower than the first predetermined temperature T1, it is set to be constant.

-Characteristics of thermostat valve-
Hereinafter, regarding the characteristics of the second thermostat valve 27, differences from the first embodiment will be described.

  FIG. 12 is a diagram showing changes in the valve passage areas of the first and second thermostat valves 25 and 27 with respect to the temperature of the cooling water. The solid line in the figure shows the characteristics of the first thermostat valve 25, and the dotted line in the figure shows The characteristics of the second thermostat valve 27 are shown.

  In the second thermostat valve 27, the area of the valve passage 81 when the valve is opened is constant when the temperature of the cooling water is lower than the first predetermined temperature T1, that is, the cooling when the second thermostat valve 27 is opened. The water flow rate is set to be constant when the temperature of the cooling water is lower than the first predetermined temperature T1.

  As described above, when the temperature of the cooling water is lower than the first predetermined temperature T1, the flow rate of the cooling water when the second thermostat valve 27 is opened is fixed to the water jacket 9 of the cylinder block 5 at the cold start. This is to further reduce the circulation amount of the cooling water.

-Effect-
According to this embodiment, when the temperature is lower than the first predetermined temperature T1, the circulation amount of the cooling water to the water jacket 9 of the cylinder block 5 becomes smaller, so that the cylinder block 5 can be kept at a higher temperature. Therefore, it is possible to further reduce fuel consumption during cold start.

  Further, when the temperature of the cooling water is lower than the first predetermined temperature T1, the area of the valve passage 81 of the main valve portion 35 of the second thermostat valve 27 is made constant so that the water jacket 9 of the cylinder block 5 is connected to the water jacket 9. The circulation amount of cooling water can be reduced. Therefore, it is possible to further reduce the fuel consumption during the cold start without complicating the structure of the cooling device 1.

  Furthermore, when the temperature of the cooling water is less than the first predetermined temperature T1 with a simple structure in which the valve seat 43 of the second thermostat valve 27 is simply provided with the cylindrical limiting wall 83, the temperature of the cooling water is accompanied by a change in temperature. Thus, only the area change of the valve passage 81 can be restricted while the main valve body 79 is displaced.

  The present invention is not limited to the embodiments, and can be implemented in various other forms without departing from the spirit or main features thereof.

  As described above, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  As described above, the present invention is useful for an engine cooling device provided with a thermostat valve.

It is a figure which shows typically the structure of the cooling device of the engine which concerns on Embodiment 1. FIG. It is a figure which shows the flow of the cooling water when the 1st and 2nd thermostat valve is open. It is a figure which shows the flow of the cooling water when the 1st and 2nd thermostat valve is closing. It is a figure which shows the flow of the cooling water when the 1st thermostat valve is closed and the 2nd thermostat valve is open. It is a figure which shows the 1st thermostat valve at the time of valve closing. It is a figure which shows the 1st thermostat valve at the time of valve opening. It is a figure which shows the 2nd thermostat valve at the time of valve closing. It is a figure which shows the 2nd thermostat valve at the time of valve opening. It is a figure which shows the change of the valve passage area of the 1st and 2nd thermostat valve with respect to the temperature of a cooling water. It is a figure which shows the flow of a cooling water when the temperature of a cooling water is less than 1st predetermined temperature. It is a figure which shows the structure of the main valve part of a 2nd thermostat valve. It is a figure which shows the change of the valve passage area of the 1st and 2nd thermostat valve with respect to the temperature of a cooling water.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine cooling device 5 Cylinder block 7 Cylinder head 9 Cylinder block water jacket 11 Cylinder head water jacket 13 Radiator 15 Water pump 23 Second bypass passage 25 First thermostat valve 27 Second thermostat valve 43 Valve seat 43c Valve seat plate 49 Flowing hole 71 Valve passage (first bypass passage)
79 Main valve (valve)
79b Standing wall portion 79c Bottom wall portion 81 Valve passage 83 Restriction wall portion 85 Main cooling water circuit T1 First predetermined temperature T2 Second predetermined temperature (opening start temperature of the first thermostat valve)
T3 third predetermined temperature (opening start temperature of the second thermostat valve)
T4 4th predetermined temperature (full open temperature of the 1st thermostat valve)
T5 5th predetermined temperature (full open temperature of the 1st thermostat valve)

Claims (6)

A water jacket for the cylinder block, a water jacket for the cylinder head, a radiator, and a water pump are provided in this order in the circulation direction of the cooling water, and the first cooling water circuit bypasses the radiator. A bypass passage and a second bypass passage which branches from the water pump downstream side of the main cooling water circuit, bypasses the water jacket of the cylinder block and communicates with the water jacket of the cylinder head, and cools during cold start An engine cooling apparatus for circulating water through the first and second bypass passages,
Provided on the upstream side of the water pump of the main cooling water circuit, and opens and closes according to the temperature of the cooling water. When the valve is opened, the cooling water is circulated to the main cooling water circuit side. A first thermostat valve that circulates to the bypass passage side;
Provided on the downstream side of the water pump of the main cooling water circuit, and opens and closes according to the temperature of the cooling water. When the valve is opened, the cooling water flows to the main cooling water circuit side. 2 further comprising a second thermostat valve that circulates to the bypass passage side,
The valve opening start temperature of the first thermostat valve is set higher than the valve opening start temperature of the second thermostat valve, and the fully open temperature of the first thermostat valve is higher than the fully open temperature of the second thermostat valve. Set,
When the cooling water flow rate change rate at the time of opening of the second thermostat valve due to the temperature change of the cooling water is lower than the first predetermined temperature lower than the valve opening start temperature of the first thermostat valve The engine cooling apparatus is set smaller than the first predetermined temperature or more. The engine cooling device according to claim 1,
The second thermostat valve has a valve seat in which a flow hole for flowing cooling water to the main cooling water circuit side is formed, and a valve body,
Between the valve seat and the valve body, a valve passage for circulating cooling water through the flow hole is formed,
When the second thermostat valve is opened, the valve body displaces away from the valve seat and opens the valve passage to circulate cooling water to the main cooling water circuit side, while the second thermostat When the valve is closed, the cooling water is made to flow to the second bypass passage side by closing the flow hole by contacting the valve seat,
When the rate of change of the area of the valve passage when the second thermostat valve is opened due to the temperature change of the cooling water is less than the first predetermined temperature, the temperature of the cooling water is the first predetermined temperature. A cooling device for an engine characterized by being set smaller than when the temperature is higher than the temperature. The engine cooling device according to claim 2,
The valve seat has an annular valve seat plate in which the flow hole is formed,
The valve body includes an annular bottom wall portion that comes into contact with the valve seat plate when the second thermostat valve is closed, and extends from the inner peripheral edge portion of the bottom wall portion in the valve body displacement direction. Inclined radially inward as it leaves, and has a substantially cylindrical standing wall that can be inserted and removed in the valve body displacement direction with respect to the flow hole,
The valve passage is formed between the valve seat plate and the standing wall portion,
The upright wall portion is displaced away from the valve seat plate when the second thermostat valve is opened to open the valve passage,
The engine cooling device according to claim 1, wherein a length of the upright wall portion in the valve body displacement direction is set to such a length that the upright wall portion can be removed from the flow hole at the first predetermined temperature. The engine cooling device according to claim 1,
An engine cooling apparatus, wherein the flow rate of the cooling water when the second thermostat valve is opened is set to be constant when the temperature of the cooling water is lower than the first predetermined temperature. The engine cooling device according to claim 4.
The second thermostat valve has a valve seat in which a flow hole for flowing cooling water to the main cooling water circuit side is formed, and a valve body,
Between the valve seat and the valve body, a valve passage for circulating cooling water through the flow hole is formed,
When the second thermostat valve is opened, the valve body displaces away from the valve seat and opens the valve passage to circulate cooling water to the main cooling water circuit side, while the second thermostat When the valve is closed, the coolant flows through the second bypass passage by contacting the valve seat and closing the flow hole,
The engine cooling device characterized in that the area of the valve passage when the second thermostat valve is opened is set to be constant when the temperature of the cooling water is lower than the first predetermined temperature. . The engine cooling device according to claim 5,
The valve seat has an annular valve seat plate in which the flow hole is formed,
The valve body includes an annular bottom wall portion that comes into contact with the valve seat plate when the second thermostat valve is closed,
The valve passage is formed between the valve seat plate and the bottom wall portion,
The valve seat plate is formed with a cylindrical limiting wall portion extending in the valve body displacement direction so as to surround the bottom wall portion in order to regulate a change in the area of the valve passage.
The engine cooling device characterized in that the valve body displacement direction length of the limiting wall portion is set to such a length that the bottom wall portion comes out of the limiting wall portion at the first predetermined temperature. .

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