JP2013124546A - Cooling device of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooling device of a vehicle capable of appropriately and separately carrying out the warmup and cooling of a cylinder block and a cylinder head in accordance with a driving state without requiring complicated control.SOLUTION: A first thermostat 11 selects, according to a coolant temperature, an operation of circulating a coolant only to a second passage 22 or an operation of circulating the coolant to both of a first passage 21 and the second passage 22. A second thermostat 12 selects, according to the coolant temperature, an operation of circulating the coolant circulated from the second passage 22 to the downstream side of the second passage 22 or an operation of circulating the coolant flowing from a first connection passage 25 to the downstream side of the second passage 22. A third thermostat 13 circulates the coolant to a second connection passage 26 if the coolant temperature is lower than a third prescribed temperature that is lower than a first prescribed temperature, and circulates the coolant to the downstream side second passage 22 if the coolant temperature is equal to or higher than the third prescribed temperature. The first prescribed temperature is set to be lower than a second prescribed temperature and higher than the third prescribed temperature.

Description

  The present invention relates to a cooling technique for an internal combustion engine.

  Conventionally, the engine cooling system is divided into two systems, a cylinder block and a cylinder head, and the cooling water temperature of the cylinder block side cooling circuit of the engine is set to be high so that the oil film temperature of the sliding portion is increased. A technology is known to improve fuel efficiency and output by improving friction efficiency and knocking resistance by reducing friction and improving fuel efficiency, and setting the cooling water temperature of the cooling circuit on the cylinder head side lower. . For example, Patent Document 1 discloses a technology that has two engine cooling systems in a hybrid vehicle and separately cools a cylinder block and a cylinder head. Patent Document 2 discloses a cooling system that supplies cooling water cooled by a radiator to a cylinder head and supplies cooling water that does not pass through the radiator to a cylinder block. Further, Patent Document 3 discloses a technique for supplying cooling water to a cylinder block and a cylinder head without passing a radiator according to the temperature of the cooling water.

JP 2000-073763 A JP 2011-185267 A JP 2009-097352 A

  As described above, in order to reduce friction, it is necessary to warm up the cylinder block early. On the other hand, the cylinder head needs to be kept at a relatively low temperature in order to suppress knocking and the like, and the cylinder block needs to be cooled from the viewpoint of suppressing overheating when the engine is heavily loaded. Therefore, it is preferable that the engine cooling system performs these warm-up and cooling at an appropriate timing, and that these controls are not complicated.

  The present invention has been made to solve the above-described problems, and appropriately warms up and cools the cylinder block and the cylinder head according to the operation state without requiring complicated control. It is a main object to provide a vehicle cooling device capable of achieving the above.

  In one aspect of the present invention, an engine having a cylinder head and a cylinder block, a cooling water passage for cooling the engine, a radiator provided, and a first passage communicating with the cylinder head, A cooling water passage that communicates with the cylinder block and branches to a second passage that bypasses the radiator, and a branch point between the first passage and the second passage. When the temperature is lower than one predetermined temperature, the cooling water is circulated only through the second passage. When the temperature of the cooling water is equal to or higher than the first predetermined temperature, both the first passage and the second passage are provided. A first thermostat for circulating cooling water, a first connection passage connecting the first passage and the second passage downstream of the radiator, and a connection point between the first connection passage and the second passage. Establishment If the detected temperature of the cooling water is lower than the second predetermined temperature that is higher than the first predetermined temperature, the cooling water that has flowed from the second passage is circulated downstream of the second passage, and the cooling water When the temperature is equal to or higher than the second predetermined temperature, the flow of the cooling water from the second passage is interrupted, and the cooling water flowing from the first connection passage is circulated downstream of the second passage. A second thermostat to be made, the first passage downstream from the connection point between the first connection passage and the first passage, and the second passage downstream from the connection point between the first connection passage and the second passage. When the detected coolant temperature is lower than the first predetermined temperature and lower than the third predetermined temperature, provided at the connection point between the second connection passage and the second connection passage and the second passage. Includes the second passage from the second thermostat. When the cooling water that has flowed in is circulated only to the cylinder head through the second connection passage and the first passage, and the temperature of the cooling water is equal to or higher than the third predetermined temperature, the second thermostat And a third thermostat that circulates the cooling water that has flowed in through the second passage to the cylinder block through the second passage downstream.

  The vehicle cooling device includes an engine having a cylinder head and a cylinder block, a cooling water passage that branches into a first passage and a second passage, first to third thermostats, and first to second connection passages. . The first passage is provided with a radiator and communicates with the cylinder head, and the second passage communicates with the cylinder block and bypasses the radiator. The first thermostat is provided at a branch point between the first passage and the second passage. When the detected temperature of the cooling water is lower than the first predetermined temperature, the cooling water is circulated only in the second passage and cooled. When the water temperature is equal to or higher than the first predetermined temperature, the cooling water is circulated through both the first passage and the second passage. The second thermostat is provided at a connection point between the first connection passage and the second passage, and when the detected temperature of the cooling water is lower than the second predetermined temperature that is higher than the first predetermined temperature, the second thermostat is circulated from the second passage. When the cooling water is circulated downstream of the second passage and the temperature of the cooling water is equal to or higher than the second predetermined temperature, the circulation of the cooling water from the second passage is interrupted and the cooling water flowing from the first connection passage is It distribute | circulates downstream of a 2nd channel | path. The third thermostat is provided at a connection point between the second connection passage and the second passage, and when the detected coolant temperature is lower than the third predetermined temperature lower than the first predetermined temperature, the second thermostat is connected to the second connection passage. Cooling water is circulated, and when the temperature of the cooling water is equal to or higher than the third predetermined temperature, the cooling water is circulated to the downstream second passage. The first predetermined temperature is set to a value lower than the second predetermined temperature and set to a value higher than the third predetermined temperature.

  In this configuration, when the temperature of the cooling water detected by each thermostat is lower than the first to third predetermined temperatures that are the respective valve opening temperatures, the cooling water is not supplied to the cylinder block. It is warmed up rapidly. On the other hand, since the cooling water that has not been cooled by the radiator is supplied to the cylinder head, the temperature of the cylinder head rises gradually. In addition, when the third thermostat exceeds the third predetermined temperature from this state, the cooling water that does not pass through the radiator is supplied to the cylinder block, and the entire engine is gradually warmed up while suppressing overheating of the cylinder block. Is done. Next, when the first thermostat reaches the first predetermined temperature or higher, the cooling water cooled by the radiator is supplied to the cylinder head, so that the cylinder head is cooled and knocking is suppressed. In addition, since uncooled cooling water is supplied to the cylinder block, the temperature of the cylinder block gradually rises and friction is reduced. Further, when the second thermostat reaches the second predetermined temperature or higher, the cooling water cooled by the radiator is supplied to both the cylinder head and the cylinder block, and the entire engine is cooled to the maximum.

  Thus, by appropriately setting the first to third predetermined temperatures for the first to third thermostats respectively, the vehicle cooling apparatus can warm up the cylinder block and cool the cylinder head when cold. The cooling of the entire engine at the time of high load can be appropriately executed according to the operating state of the engine.

  In one aspect of the vehicle cooling apparatus, the first predetermined temperature is set to a temperature reached by the cooling water when the warm-up of the engine is completed, and the second predetermined temperature cools the entire engine. The third predetermined temperature is set to a temperature reached by the cooling water before the engine is completely warmed up. In this aspect, the first predetermined temperature is determined in advance based on, for example, experiments or the like, at a temperature reached by the cooling water when the warm-up of the engine is completed. The second predetermined temperature is determined in advance based on, for example, experiments or the like, at a temperature reached by the cooling water when it is necessary to cool the entire engine. The third predetermined temperature is set in advance to a temperature reached by the cooling water before the engine warm-up is completed, for example, based on experiments. By doing so, the vehicle cooling device can warm up the cylinder block during cold, cool the cylinder head, and cool the entire engine under high load at an appropriate timing according to the operating state of the engine. Can be executed.

The schematic block diagram of the cooling system of this embodiment is shown. The flow of the cooling water in the cooling system at the early stage of warm-up is shown. The flow of the cooling water in the cooling system during the warm-up process is shown. The flow of the cooling water in the cooling system when the warm-up is completed and not under a high load is shown. The flow of cooling water in the cooling system after completion of warming up and at high load is shown. It is a graph which shows the time change of the inlet temperature of a cylinder head and a cylinder block.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

[Configuration of cooling system]
FIG. 1 is a diagram showing a schematic configuration of a cooling system 100 to which a vehicle cooling device according to the present invention is applied. In FIG. 1, the solid arrow indicates the direction in which the cooling water flows.

  The cooling system 100 cools the engine 1 using the cooling water, and collects exhaust heat by exchanging heat between the cooling water and the exhaust gas, thereby warming up the engine 1 and a heat source for the heater. It is a system used for. In this case, the cooling water cools and warms up the engine 1 by passing through the cooling water passage 2. On the cooling water passage 2, a radiator 4, a first thermostat 11, a second thermostat 12, and a third thermostat 13 are provided.

  The engine (internal combustion engine) 1 is a device that generates power by burning a mixture of supplied fuel and air. For example, the engine 1 is a gasoline engine or a diesel engine. The engine 1 includes a cylinder head 5 and a cylinder block 6. The cylinder head 5 is provided with a first cooling water introduction port 31 into which cooling water is introduced from a first cooling water passage 21 (described later) of the cooling water passage 2, and the cylinder block 6 includes a cooling water passage 2 described later. A second cooling water introduction port 32 through which cooling water is introduced from the second cooling water passage 22 is provided. The cooling water introduced into the cylinder head 5 from the first cooling water inlet 31 is supplied again to the cooling water passage 2 by the water pump 3 after passing through the cylinder head 5. Further, the coolant introduced into the cylinder block 6 from the second coolant introduction port 32 passes through the cylinder block 6, is then supplied to the cylinder head 5, and is supplied again to the coolant passage 2 by the water pump 3.

  The water pump 3 includes an impeller and circulates cooling water in the cooling system 100. The water pump 3 is provided in the vicinity of the cooling water outlet of the cylinder head 5 and in the vicinity of the inlet of the cooling water passage 2. The radiator 4 cools the cooling water passing through the inside thereof with outside air. In this case, cooling of the cooling water in the radiator 4 is promoted by the wind introduced by the rotation of the electric fan (not shown).

  The cooling water supplied from the water pump 3 passes through the pre-branch cooling water passage 20 and is supplied to the first thermostat 11. The pre-branch cooling water passage 20 branches into a first cooling water passage 21 and a second cooling water passage 22 at the installation point of the first thermostat 11. The first coolant passage 21 is provided with the radiator 4 and communicates with the first coolant introduction port 31. The second cooling water passage 22 is provided with a second thermostat 12 and a third thermostat 13, and communicates with the second cooling water inlet 32 while bypassing the radiator 4. The first cooling water passage 21 is an example of the “first passage” in the present invention, and the second cooling water passage 22 is an example of the “second passage” in the present invention.

  The first cooling water passage 21 and the second cooling water passage 22 are connected by a first connection passage 25 and a second connection passage 26. Specifically, the first connection passage 25 connects the first cooling water passage 21 and the second cooling water passage 22 downstream of the radiator 4. Further, the second connection passage 26 includes a first cooling water passage 21 downstream from a connection point between the first connection passage 25 and the first cooling water passage 21, and the first connection passage 25 and the second cooling water passage 22. The second cooling water passage 22 downstream from the connection point is connected. The second thermostat 12 is provided at a connection point between the first connection passage 25 and the second cooling water passage 22, and a third connection point between the second connection passage 26 and the second cooling water passage 22 is provided at the third connection point. A thermostat 13 is provided.

  The first thermostat 11, the second thermostat 12, and the third thermostat 13 (collectively referred to as “thermostat”) each have a valve that opens and closes according to the detected temperature of the cooling water. The first thermostat 11 blocks the flow of cooling water from the pre-branch cooling water passage 20 to the first cooling water passage 21 in the valve-closed state. In this case, the cooling water supplied from the pre-branch cooling water passage 20 is supplied only to the second cooling water passage 22 and is not supplied to the first cooling water passage 21. On the other hand, the first thermostat 11 is opened when the temperature of the cooling water reaches a predetermined temperature (also referred to as “first predetermined temperature T1”). In the opened state, the first thermostat 11 enters the first cooling water passage 21. The inlet is opened, and the cooling water supplied from the pre-branch cooling water passage 20 is supplied to both the first cooling water passage 21 and the second cooling water passage 22.

  In the closed state, the second thermostat 12 blocks the flow of the cooling water in the first connection passage 25 and distributes the cooling water from the upstream side to the downstream side of the second cooling water passage 22. In this case, the cooling water supplied from the first thermostat 11 is supplied to the third thermostat 13 through the second cooling water passage 22. On the other hand, the second thermostat 12 is opened when the detected temperature of the cooling water reaches a predetermined temperature (also referred to as “second predetermined temperature T2”). In the opened state, the second cooling water passage 22 is opened. And the first connection passage 25 and the downstream of the second cooling water passage 22 are made conductive. In this case, the cooling water does not flow from the first thermostat 11 to the second thermostat 12, and the cooling water flows from the first connection passage 25 to the downstream of the second cooling water passage 22.

  In the closed state, the third thermostat 13 blocks the flow of the cooling water downstream of the second cooling water passage 22 and causes the cooling water to flow through the second connection passage 26. In this case, the cooling water flowing into the third thermostat 13 from the second thermostat 12 flows downstream of the first cooling water passage 21 through the second connection passage 26. On the other hand, the third thermostat 13 is opened when the temperature of the cooling water reaches a predetermined temperature (also referred to as “third predetermined temperature T3”). In the opened state, the third thermostat 13 is upstream of the second cooling water passage 22. The coolant is circulated from the downstream to the downstream, and the flow of the coolant in the second connection passage 26 is blocked. In this case, the cooling water flowing into the third thermostat 13 from the second thermostat 12 is supplied to the second cooling water inlet 32 through the second cooling water passage 22.

Here, the first predetermined temperature T1 is set higher than the third predetermined temperature T3, and the second predetermined temperature T2 is set higher than the first predetermined temperature T1. That is, the relationship represented by the formula (1) is established between the first predetermined temperature T1, the second predetermined temperature T2, and the third predetermined temperature T3.
T3 <T1 <T2 Formula (1)
The specific set temperatures of the first predetermined temperature T1, the second predetermined temperature T2, and the third predetermined temperature T3 (these are collectively referred to as “valve opening temperature”) are described in the section [Cooling function] described later. In consideration of the cooling function and warm-up function for the engine 1 in each state of the cooling system 100 shown in FIG. As will be described later, the third predetermined temperature T3 is set to a temperature reached by the cooling water before the warm-up of the engine 1 is completed, for example. Further, the first predetermined temperature T1 is set to a temperature reached by the cooling water when the warm-up of the engine 1 is completed, for example. The second predetermined temperature T2 is set to a temperature reached by the cooling water when, for example, the entire engine 1 needs to be cooled. In addition, each thermostat is set so that, for example, when the detected temperature of the cooling water reaches the valve opening temperature, the opening degree is increased continuously or stepwise according to the temperature increase of the cooling water. Also good.

[Cooling function]
Next, the cooling function realized by the cooling system 100 will be specifically described. In the cooling system 100, the valve is opened in the order of the third thermostat 13, the first thermostat 11, and the second thermostat 12 with the time transition from the cold start of the engine 1 to the high load. Thereby, the cooling system 100 performs warming-up and cooling to each of the cylinder head 5 and the cylinder block 6 at appropriate timings, and improves fuel consumption.

  Hereinafter, the state transition of the cooling system 100 accompanying the time transition from the start of the engine 1 will be specifically described with reference to FIGS. 2 to 5. 2 to 5, solid arrows indicate that cooling water flows in the passage indicated by the arrow, and broken arrows indicate that cooling water does not flow in the passage indicated by the arrow. Indicates.

(1) Warm-up Initial State FIG. 2 shows the state of the cooling system 100 at the initial stage during the warm-up period, that is, during the warm-up period of the engine 1. In this case, the temperature of the cooling water detected by each thermostat is lower than each valve opening temperature. Therefore, in this case, all thermostats are in a closed state.

  In this state, the cooling water passes through the second thermostat 12 and the third thermostat 13 on the second cooling water passage 22 without passing through the radiator 4 from the pre-branching cooling water passage 20 and passes through the second connection passage 26. Then, it is supplied to the first cooling water inlet 31. Thus, in the initial stage of warm-up, the cooling system 100 disables cooling of the cooling water by the radiator 4, supplies cooling water only to the cylinder head 5, and stops cooling the cylinder block 6. As a result, the cooling system 100 quickly warms up the cylinder block 6 and improves fuel consumption.

(2) Warm-up process FIG. 3 shows the state of the cooling system 100 after the initial stage in the warm-up process, that is, the warm-up period of the engine 1. In this case, the temperature of the cooling water detected by the third thermostat 13 is equal to or higher than the third predetermined temperature T3. That is, the third predetermined temperature T3 is the temperature of the cooling water detected by the third thermostat 13 at the time of transition from the initial warm-up for rapidly warming up the cylinder block 6 to the warm-up process for gently warming up the cylinder block 6. Is set. Accordingly, in this case, the third thermostat 13 is opened, whereby all the cooling water supplied from the second thermostat 12 to the third thermostat 13 is supplied to the second cooling water inlet 32.

  Thus, in the warm-up process, the cooling system 100 can appropriately cool the entire engine 1 and disable the overheating of the cylinder block 6 while facilitating warm-up by disabling the radiator 4.

(3) After Warm-up and not at High Load FIG. 4 shows the state of the cooling system 100 after the engine 1 is warmed up and not at a high load. In this case, the temperature of the cooling water detected by the first thermostat 11 is equal to or higher than the first predetermined temperature T1. That is, the first predetermined temperature T1 is set to the temperature of the cooling water detected by the first thermostat 11 when the warm-up of the engine 1 is completed. Accordingly, in this case, the first thermostat 11 is opened, and the cooling water supplied from the pre-branch cooling water passage 20 to the first thermostat 11 flows into the second cooling water passage 22 upstream of the second thermostat 12 and the radiator 4 upstream. And the first cooling water passage 21. The first connection passage 25 is blocked by the second thermostat 12, and the second connection passage 26 is blocked by the third thermostat 13. Therefore, the cooling water that has passed through the radiator 4 passes through the first cooling water passage 21 and is supplied to the first cooling water introduction port 31, and the cooling water supplied from the first thermostat 11 to the second cooling water passage 22 The cooling water passage 22 is supplied to the second cooling water inlet 32.

  Thus, after warming up, the cylinder block 6 is supplied with uncooled cooling water. Thereby, the cooling system 100 can raise the internal temperature of the cylinder block 6 moderately, can reduce friction, and can improve a fuel consumption. In addition, after warming up, the cooling water cooled by the radiator 4 is supplied to the cylinder head 5. Thereby, the cooling system 100 can reduce the temperature of the cylinder head 5, suppress knocking, increase the thermal efficiency, and improve fuel efficiency.

(4) At High Load FIG. 5 shows a state of the cooling system 100 when the engine 1 is at a high load. In this case, the temperature of the cooling water detected by the second thermostat 12 is equal to or higher than the second predetermined temperature T2. That is, the second predetermined temperature T2 is set to a temperature detected by the second thermostat 12 when the engine 1 is at a high load, that is, when the entire engine 1 needs to be cooled. In this case, the second thermostat 12 blocks the second cooling water passage 22 upstream of the second thermostat 12 and opens the first connection passage 25. As a result, all the cooling water that has passed through the pre-branch cooling water passage 20 passes through the radiator 4 provided on the first cooling water passage 21. Thereafter, a part of the cooling water flows from the first connection passage 25 into the second cooling water passage 22 downstream of the second thermostat 12 and is supplied from the second cooling water inlet 32 to the cylinder block 6, and the other cooling water. Is supplied from the first coolant passage 21 to the cylinder head 5 via the first coolant introduction port 31.

  Thus, when the engine 1 is under a high load, the cooling water cooled by the radiator 4 is supplied to both the cylinder head 5 and the cylinder block 6. By doing in this way, the cooling system 100 can cool the whole engine 1 to the maximum extent.

[Concrete example]
Next, referring to FIG. 6, the state change of the cooling system 100 described in the “Cooling function” section will be specifically described.

  FIG. 6 shows the time change of the temperature (also referred to as “block inlet temperature”) in the vicinity of the second cooling water inlet 32 of the cylinder block 6 after the start of the engine 1 and the first cooling water inlet 31 of the cylinder head 5. It is a graph which shows the time change of temperature in the vicinity (it is also called "head inlet temperature"). Specifically, the graph “B1” shows the time change of the block inlet temperature based on this embodiment, and the graph “B2” shows the time change of the head inlet temperature based on this embodiment. In addition, the graph “C1” is a cooling system structure example in which the first to third thermostats 11 to 13 are not provided and the first to second connection passages 25 and 26 are not provided (also referred to as “comparative example”). The graph “C2” shows the time change of the head inlet temperature based on the comparative example. In other words, the graphs C1 and C2 continue to be in the state of FIG. 4, that is, the state in which the cooling water cooled by the radiator 4 is supplied to the cylinder head 5 and the cooling water that does not pass through the radiator 4 is supplied to the cylinder block 6. The change with time of the block inlet temperature and the head inlet temperature is shown.

  First, the time “t0” to the time “t1” when the engine 1 is started corresponds to the early warm-up of the engine 1, and during this period, the temperature of the cooling water detected by each thermostat is the valve opening temperature of each thermostat. Lower than. Accordingly, in this case, the first to third thermostats 11 to 13 are all closed, and the cooling water system 100 is in the state shown in FIG. As a result, cooling water that has not been cooled by the radiator 4 is supplied to the cylinder head 5, and the temperature of the cylinder head 5 rises gently (see graph B2). Further, during this period, since the cooling water is not supplied to the cylinder block 6, the cylinder block 6 is rapidly warmed up (see graph B1).

  On the other hand, in the comparative example, during the period from time t0 to time t1, cooling water that does not pass through the radiator 4 is supplied to the cylinder block 6, and cooling water cooled by the radiator 4 is supplied to the cylinder head 5. . Therefore, in the comparative example, the temperature rise of the cylinder block 6 is moderate (see graph C1) and the fuel consumption is poor as compared with the present embodiment.

  Next, the time period from time t1 to time “t2” corresponds to a warm-up process, and during this period, the temperature of the cooling water detected by the third thermostat 13 is equal to or higher than the third predetermined temperature T3. In this case, the third thermostat 13 is opened, and the cooling system 100 is in the state shown in FIG. As a result, cooling water is also supplied to the cylinder block 6, and overheating of the cylinder block 6 is suppressed (see graph B1), while the temperatures of the cylinder head 5 and the cylinder block 6 gradually increase (see graphs B1 and B2). .

  A time zone from time t2 to time “t3” corresponds to a time zone in which the engine 1 has been warmed up and the engine 1 is not under a high load, and the first thermostat 11 detects during this period. The temperature of the cooling water is equal to or higher than the first predetermined temperature T1. In this case, the 1st thermostat 11 opens and the cooling system 100 will be in the state shown in FIG. In this state, the cooling system 100 supplies the cooling water cooled by the radiator 4 to the cylinder head 5, thereby cooling the cylinder head 5 and suppressing knocking (see graph B2). Moreover, the cooling system 100 supplies the cooling water which is not cooled to the cylinder block 6, and raises the cylinder block 6 gently and reduces friction (refer graph B1).

  A time zone after time t3 corresponds to a time zone in which the engine 1 is heavily loaded. During this period, the temperature of the cooling water passing through the second thermostat 12 is equal to or higher than the second predetermined temperature T2. In this case, the second thermostat 12 is opened, and the cooling system 100 is in the state shown in FIG. In this state, the cooling system 100 supplies the cooling water cooled by the radiator 4 to both the cylinder head 5 and the cylinder block 6, thereby cooling the entire engine 1 as much as possible. Thereby, even when the engine 1 is at a high load, the temperature rise of the cylinder head 5 and the cylinder block 6 is prevented and overheating is suppressed (see graphs B1 and B2).

1 engine (internal combustion engine)
2 Cooling water passage 3 Water pump 4 Radiator 5 Cylinder head 6 Cylinder block 11 1st thermostat 12 2nd thermostat 13 3rd thermostat

Claims (2)

An engine having a cylinder head and a cylinder block;
A cooling water passage for cooling the engine, which is provided with a radiator and branches into a first passage communicating with the cylinder head and a second passage communicating with the cylinder block and bypassing the radiator. A cooling water passage,
The cooling water is provided at a branch point between the first passage and the second passage, and when the detected temperature of the cooling water is lower than a first predetermined temperature, the cooling water is circulated only in the second passage, and the cooling water A first thermostat that circulates cooling water through both the first passage and the second passage when the temperature is equal to or higher than the first predetermined temperature;
A first connection passage connecting the first passage and the second passage downstream of the radiator;
When the detected coolant temperature is lower than a second predetermined temperature that is higher than the first predetermined temperature and provided at a connection point between the first connection passage and the second passage, the cooling that has flowed in from the second passage When water is circulated downstream of the second passage, and the temperature of the cooling water is equal to or higher than the second predetermined temperature, the flow of the cooling water from the second passage is interrupted, and the first A second thermostat for circulating cooling water flowing in from the connection passage downstream of the second passage;
A second connecting the first passage downstream from the connection point between the first connection passage and the first passage and the second passage downstream from the connection point between the first connection passage and the second passage. A connecting passage,
Provided at a connection point between the second connection passage and the second passage, and when the detected temperature of the cooling water is lower than a third predetermined temperature lower than the first predetermined temperature, the second thermostat When the coolant flowing in through the two passages is circulated only to the cylinder head through the second connection passage and the first passage, and the temperature of the coolant is equal to or higher than the third predetermined temperature, A third thermostat for circulating cooling water flowing from the second thermostat through the second passage to the cylinder block via the second passage downstream;
A vehicle cooling device comprising: The first predetermined temperature is set to a temperature reached by the cooling water when warming up of the engine is completed,
The second predetermined temperature is set to a temperature reached by the cooling water when it is necessary to cool the entire engine.
2. The vehicle cooling device according to claim 1, wherein the third predetermined temperature is set to a temperature reached by the cooling water before warming up of the engine is completed.

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