Internal combustion engine cooling system

Abstract

To provide a cooling system for an internal combustion engine capable of reducing a temperature difference between a cooling water and lubrication oil even when the internal combustion engine is automatically stopped.SOLUTION: A cooling system for an internal combustion engine includes: the internal combustion engine that enables automatic stop and automatic restart; an electric pump that is operated during an operation of the internal combustion engine to circulate cooling water in the internal combustion engine and stops its operation in accordance with automatic stop of the internal combustion engine; water temperature acquisition means for acquiring a temperature of the cooling water; oil temperature acquisition means for acquiring a temperature of lubrication oil circulating in the internal combustion engine; and a control device that controls the operation of the electric pump. When a temperature difference between the cooling water and the lubricating oil becomes a predetermined first temperature of higher during automatic stop of the internal combustion engine, the control device starts the operation of the electric pump.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to cooling systems for internal combustion engines. [Background technology]

[0002] Patent Document 1 discloses a cooling system for an internal combustion engine that includes an electric pump that is installed in a circulation path of cooling water that cools a turbocharger of the internal combustion engine and that pressurizes and pumps the cooling water, a detection unit that detects whether the internal combustion engine is stopped due to an idling stop or not, and a control unit that controls the workload of the electric pump when the internal combustion engine is stopped in accordance with the detection result of the detection unit. This internal combustion engine cooling system reduces the workload when the internal combustion engine is stopped due to an idling step compared to the workload when the internal combustion engine is stopped without an idling stop. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-31871 Summary of the Invention [Problem to be solved by the invention]

[0004] When an internal combustion engine is stopped, the temperature of the lubricating oil drops more slowly than the temperature of the coolant. Therefore, when the internal combustion engine is stopped, the temperature difference between the coolant and the lubricating oil increases. This temperature difference between the coolant and the lubricating oil affects various controls. For example, when calculating the friction torque of an internal combustion engine based on the coolant temperature, there is a large discrepancy between the calculated friction torque and the actual friction torque when the internal combustion engine is restarted.

[0005] In view of the above circumstances, at least one embodiment of the present invention aims to provide a cooling system for an internal combustion engine that can reduce the temperature difference between the cooling water and the lubricating oil even when the internal combustion engine is automatically stopped. [Means for solving the problem]

[0006] (1) A cooling system for an internal combustion engine according to at least one embodiment of the present invention comprises an internal combustion engine capable of automatic stopping and automatic restarting, an electric pump that operates while the internal combustion engine is operating to circulate cooling water through the internal combustion engine and stops operating in response to automatic stopping of the internal combustion engine, a water temperature acquisition means that acquires the temperature of the cooling water, an oil temperature acquisition means that acquires the temperature of lubricating oil circulating through the internal combustion engine, and a control device that controls the operation of the electric pump, wherein the control device starts the operation of the electric pump when the temperature difference between the cooling water and the lubricating oil becomes equal to or greater than a predetermined first temperature during automatic stopping of the internal combustion engine.

[0007] According to the configuration (1) above, when the temperature difference between the coolant and the lubricating oil becomes equal to or greater than a predetermined first temperature during automatic stop of the internal combustion engine, the electric pump starts operating, so that heat exchange occurs between the coolant and the lubricating oil, making it possible to make the temperature difference between the coolant and the lubricating oil less than the first temperature. This makes it possible to reduce the temperature difference between the coolant and the lubricating oil even when the internal combustion engine is automatically stopped.

[0008] (2) In some embodiments, in the configuration of (1) above, the control device starts operation of the electric pump when, during automatic stop of the internal combustion engine, the temperature difference between the cooling water and the lubricating oil is equal to or greater than the first temperature and the temperature of the cooling water is less than a predetermined second temperature.

[0009] According to the configuration (2) above, when the internal combustion engine is automatically stopped, if the temperature difference between the cooling water and the lubricating oil is equal to or greater than a first temperature and the temperature of the cooling water is less than a predetermined second temperature, the electric pump starts operating, thereby promoting heat exchange between the cooling water and the lubricating oil and maintaining the temperature of the cooling water at or above the second temperature.

[0010] (3) In some embodiments, the configuration of (1) or (2) above includes a prediction unit that predicts the restart of the internal combustion engine, and the control device starts operation of the electric pump when the temperature difference between the cooling water and the lubricating oil is equal to or greater than the first temperature and the restart of the internal combustion engine is predicted.

[0011] According to the configuration (3) above, when the temperature difference between the cooling water and the lubricating oil is equal to or greater than the first temperature and when the restart of the internal combustion engine is predicted, the electric pump starts operating. Therefore, heat exchange is performed between the cooling water and the lubricating oil before the restart of the internal combustion engine, and the temperature difference between the cooling water and the lubricating oil can be reduced.

[0012] (4) In some embodiments, in the configuration of (1) or (2) above, the control device increases the output of the electric pump if the temperature difference between the cooling water and the lubricating oil does not decrease after the electric pump starts operating.

[0013] According to the configuration (4) above, if the temperature difference between the cooling water and the lubricating oil does not decrease after the electric pump starts operating, the output of the electric pump is increased, thereby promoting heat exchange between the cooling water and the lubricating oil and decreasing the temperature difference between the cooling water and the lubricating oil.

[0014] (5) In some embodiments, in the configuration of (1) or (2) above, a radiator is interposed in the circulation path of the cooling water, and a heat dissipation suppression means is provided to suppress heat dissipation of the cooling water by the radiator, and the control device controls the heat dissipation suppression means to suppress heat dissipation of the cooling water by the radiator during automatic stop of the internal combustion engine.

[0015] According to the configuration of (5) above, the heat radiation suppression means suppresses heat radiation by the radiator while the internal combustion engine is automatically stopped, so that the cooling water is less likely to cool, and the temperature difference between the cooling water and the lubricating oil can be reduced. [Effects of the Invention]

[0016] According to at least one embodiment of the present invention, the temperature difference between the cooling water and the lubricating oil can be reduced even when the internal combustion engine is automatically stopped. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic diagram showing a vehicle equipped with an internal combustion engine according to a first embodiment. [Figure 2] 2 is a block diagram showing the mechanical configuration of a cooling system for cooling the internal combustion engine shown in FIG. 1. FIG. [Figure 3] FIG. 3 is a block diagram showing a control configuration of the cooling system shown in FIG. 2. [Figure 4] 4 is a time chart showing the control content of the control device shown in FIG. 3. [Figure 5] FIG. 10 is a block diagram showing a control configuration of a cooling system for an internal combustion engine according to a second embodiment. [Figure 6] 6 is a time chart showing the control content of the control device shown in FIG. 5. [Figure 7] FIG. 10 is a block diagram showing the mechanical configuration of a cooling system for an internal combustion engine according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative positions, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention.

[0019] [Embodiment 1] Fig. 1 is a schematic diagram showing a vehicle equipped with an internal combustion engine according to embodiment 1. Fig. 2 is a block diagram showing the mechanical configuration of a cooling system for cooling the internal combustion engine shown in Fig. 1, and Fig. 3 is a block diagram showing the control configuration of the cooling system shown in Fig. 2. Fig. 4 is a time chart showing the control content of the control device shown in Fig. 3.

[0020] As shown in Fig. 1, a vehicle 1 equipped with an internal combustion engine 10 according to this embodiment is a hybrid vehicle (HV) powered by the internal combustion engine 10 and traction motors 12, 14. However, the present invention is not limited to this and may be an engine vehicle equipped with an idling stop function that automatically stops the internal combustion engine when the vehicle is temporarily stopped, such as at a traffic light. The vehicle 1 includes a generator 16 driven by the internal combustion engine 10 and a traction battery 18 that charges with electricity generated by the generator 16. The vehicle 1 can operate in one of three modes: an EV driving mode in which the traction motors 12, 14 drive drive wheels 20, 22 using electricity supplied from the traction battery 18; a series driving mode in which the traction motors 12, 14 drive drive wheels 20, 22 using electricity supplied from the generator 16; or a parallel driving mode in which the internal combustion engine 10 drives drive wheels 20 and the traction motors 12, 14 assist in driving the drive wheels 20, 22. The vehicle 1 shown in FIG. 1 is a four-wheel drive hybrid vehicle, but is not limited to this and may also be a two-wheel drive hybrid vehicle.

[0021] 2, the internal combustion engine 10 according to the embodiment includes a cooling system 24 for cooling the internal combustion engine 10. The cooling system 24 includes a cooling circuit 26 for cooling the internal combustion engine 10, an electric pump (EWP) 28 for circulating coolant through the cooling circuit 26, and a control device (HVECU) 30 for controlling the output of the electric pump 28.

[0022] The cooling circuit 26 includes at least a water jacket (flow path) 36 provided in a cylinder block 32 and a cylinder head 34 that constitute the internal combustion engine 10, and a radiator 38, but may also include an oil cooler 40 and an EGR cooler 42. A radiator fan 44 is disposed opposite the radiator 38, and the output of the radiator fan 44 is controlled by the control device 30. The electric pump 28 is a pump driven by electricity supplied from an auxiliary battery (not shown), and can operate independently of the operation of the internal combustion engine 10. The electric pump 28 is normally driven when the internal combustion engine 10 is operating, and is controlled to stop when the internal combustion engine 10 stops.

[0023] The control device 30 is composed of a processor (not shown) consisting of an arithmetic unit, registers for storing instructions and information, and peripheral circuits, memories (not shown) such as ROM (Read Only Memory) and RAM (Random Access Memory), and an input interface (not shown).

[0024] 3, the control device 30 is provided with a drive stop determination means 48 for determining whether the internal combustion engine 10 is running or has automatically stopped, a water temperature acquisition means 50 for acquiring the temperature of the coolant, and an oil temperature acquisition means 52 for acquiring the temperature of the lubricating oil circulating through the internal combustion engine 10. The drive stop determination means 48 is configured, for example, by an engine control device (engine ECU) 56 connected to the control device 30, and is determined, for example, based on the rotation speed of the internal combustion engine 10, a fuel injection command to the injector of the internal combustion engine 10 and an ignition command to the spark plug from the engine control device 56. The water temperature acquisition means 50 and the oil temperature acquisition means 52 are configured, for example, by temperature sensors 58, 60 connected to the control device 30, respectively.

[0025] As shown in FIG. 4, in the cooling system 24A of the internal combustion engine 10 according to the first embodiment, the control device 30A is configured to start the operation of the electric pump 28 when the temperature difference T between the cooling water and the lubricating oil becomes equal to or greater than a predetermined first temperature T1 during an automatic stop of the internal combustion engine 10.

[0026] In the vehicle 1, the internal combustion engine 10 is automatically stopped when the vehicle switches from series driving mode or parallel driving mode (hereinafter referred to as "engine driving mode") to EV driving mode, or when a coast stop or idle stop is activated while in engine driving mode. When the internal combustion engine 10 is automatically stopped, the operation of the electric pump 28 is stopped. When the internal combustion engine 10 is stopped, the temperature of the coolant drops, and the temperature difference T between the coolant and the lubricating oil gradually increases. Then, when the temperature reaches or exceeds a first temperature T1, the electric pump 28 is started to operate.

[0027] According to the cooling system 24A for the internal combustion engine 10, when the temperature difference T between the coolant and the lubricating oil becomes equal to or greater than a predetermined first temperature T1 during automatic stop of the internal combustion engine 10, the electric pump 28 starts operating, thereby performing heat exchange between the coolant and the lubricating oil. This makes it possible to reduce the temperature difference T between the coolant and the lubricating oil when the automatic stop of the internal combustion engine 10 ends (when operation is resumed).

[0028] Also, as shown in FIG. 4, when the internal combustion engine 10 is automatically stopped, the electric pump 28 may be started to operate when the temperature difference T between the coolant and the lubricating oil is equal to or greater than a predetermined first temperature T1 and the coolant temperature WT is less than a predetermined second temperature T2.

[0029] The second temperature T2 is, for example, a temperature at which the friction torque of the internal combustion engine 10 needs to be calculated, and is, for example, a temperature at which the internal combustion engine 10 needs to be warmed up.

[0030] Referring to FIG. 4, the cooling system 24A for the internal combustion engine 10 when switching from engine driving mode to EV driving mode will be described. The electric pump 28 is driven during engine driving mode (before time t0). At time t0, the mode is switched to EV driving mode, and the internal combustion engine 10 automatically stops, thereby stopping the electric pump 28. When the internal combustion engine 10 stops, the temperatures of the coolant and lubricating oil decrease. However, because the lubricating oil temperature decreases more slowly than the coolant temperature, the temperature difference T between the coolant and lubricating oil gradually increases. At time t1, the temperature difference T between the coolant and lubricating oil is equal to or greater than the first temperature T1. However, because the coolant temperature WT is equal to or greater than the second temperature T2, the electric pump 28 remains stopped. Then, when the coolant temperature WT drops below the second temperature T2 at time t2, the electric pump 28 starts operating. After the electric pump 28 starts operating, the internal combustion engine 10 restarts at time t3, and at this time, the temperature difference T between the coolant and the lubricating oil becomes smaller than at time t2 due to heat exchange between the coolant and the lubricating oil. Note that the output of the electric pump 28 from time t2 to t3 may be smaller than that after time t3, which is intended to cool the internal combustion engine 10, as long as it allows heat exchange between the coolant and the lubricating oil.

[0031] According to the cooling system 24A for the internal combustion engine 10, the internal combustion engine 10 automatically stops and the operation of the electric pump 28 stops, so that even if the temperature difference T between the coolant and the lubricating oil becomes equal to or greater than the first temperature T1, the operation of the electric pump 28 is not started if the coolant temperature WT is equal to or greater than the second temperature T2. As a result, even if the temperature difference T between the coolant and the lubricating oil is large, the operation of the electric pump 28 is not started if the coolant temperature WT is large, so that the power consumed by the electric pump 28 can be reduced. On the other hand, because the operation of the electric pump 28 is started if the temperature difference T between the coolant and the lubricating oil is large and the coolant temperature WT is small, the temperature difference T between the coolant and the lubricating oil can be reduced, and the friction torque of the internal combustion engine 10 can be calculated accurately based on the temperature of the coolant.

[0032] In the above embodiment, the electric pump 28 is started when the temperature difference T between the coolant and the lubricating oil is equal to or greater than the first temperature T1 and the coolant temperature WT is less than a predetermined second temperature T2 during an automatic stop of the internal combustion engine 10. However, the first temperature T1 may be set to increase as the coolant temperature WT increases, and the electric pump 28 may be started when the temperature difference T between the coolant and the lubricating oil is equal to or greater than the first temperature T1 during an automatic stop of the internal combustion engine 10. In this way, it is possible to make it difficult for the electric pump 28 to start operating when the coolant temperature WT is low and to make it easy for the electric pump 28 to start operating when the coolant temperature WT is high, thereby achieving the same effect as in the above embodiment.

[0033] Furthermore, the control device 30A is configured to increase the output of the electric pump 28 if the temperature difference between the cooling water and the lubricating oil does not decrease after the electric pump 28 starts operating.

[0034] The "output of the electric pump 28" is, for example, the rotation speed of the electric pump 28, and the output of the electric pump increases as the rotation speed of the electric pump 28 increases. The electric pump 28 is controlled by, for example, pulse width modulation (PWM) control, but is not limited to this.

[0035] In other words, if the temperature difference T between the cooling water and the lubricating oil does not decrease after the electric pump 28 starts operating, the output of the electric pump 28 can be increased to promote heat exchange between the cooling water and the lubricating oil and reduce the temperature difference T between the cooling water and the lubricating oil.

[0036] [Embodiment 2] Fig. 5 is a block diagram showing a control configuration of a cooling system for an internal combustion engine according to embodiment 2. Fig. 6 is a time chart showing the control content of the control device shown in Fig. 5.

[0037] As shown in Fig. 5, in the cooling system 24B for the internal combustion engine 10 according to the second embodiment, the control device 30B has a prediction unit 62 that predicts the restart of the internal combustion engine 10, and is configured to start the operation of the electric pump 28 when the temperature difference T between the coolant and the lubricating oil is equal to or greater than the first temperature T1 and the restart of the internal combustion engine 10 is predicted, as shown in Fig. 6. Except for this point, the cooling system 24B is the same as the cooling system 24A for the internal combustion engine 10 according to the first embodiment.

[0038] For example, in the vehicle 1, the prediction unit 62 determines whether the state of charge (SOC) of the driving battery 18 is equal to or lower than a predetermined SOC, and when the SOC of the driving battery 18 falls to or lower than the predetermined SOC during EV driving, the prediction unit 62 restarts the internal combustion engine 10. Also, in a vehicle equipped with a coast stop or idling stop function, for example, the prediction unit 62 determines whether the brake oil pressure is equal to or lower than a predetermined oil pressure, and when the brake oil pressure falls to or lower than the predetermined oil pressure during a coast stop or idling stop, the prediction unit 62 restarts the internal combustion engine 10.

[0039] Referring to FIG. 6, the cooling system 24B of the internal combustion engine 10 when switching from the engine driving mode to the EV driving mode will be described. In this embodiment, the process up to time t1 is the same as that shown in FIG. 4, and therefore description thereof will be omitted. In this embodiment, the electric pump 28 is driven even if the coolant temperature WT does not fall below a predetermined second temperature T2. At time t1, the temperature difference T between the coolant and the lubricant oil becomes equal to or greater than the first temperature T1, but the prediction unit 62 does not predict a restart of the internal combustion engine 10, so the electric pump 28 remains stopped. Then, when a restart of the internal combustion engine 10 is predicted at time t4, the electric pump 28 starts operating. That is, if the temperature difference T between the coolant and the lubricant oil is equal to or greater than the first temperature T1, the electric pump 28 starts operating before the internal combustion engine 10 is restarted at time t3.

[0040] According to the cooling system 24B for the internal combustion engine 10 of the second embodiment, when the temperature difference T between the coolant and the lubricating oil is equal to or greater than the first temperature T1 and a restart of the internal combustion engine 10 is predicted, the operation of the electric pump 28 is started, so that if a restart of the internal combustion engine 10 is not predicted even when the temperature difference T between the coolant and the lubricating oil becomes large, the operation of the electric pump 28 is not started, thereby reducing the power consumed by the electric pump 28. On the other hand, when the temperature difference T between the coolant and the lubricating oil is large and a restart of the internal combustion engine 10 is predicted, the operation of the electric pump 28 is started, so that the temperature difference T between the coolant and the lubricating oil can be reduced before the internal combustion engine 10 is restarted.

[0041] [Embodiment 3] FIG. 7 is a block diagram showing the mechanical configuration of a cooling system for an internal combustion engine according to the third embodiment.

[0042] The cooling system 24C for the internal combustion engine 10 according to the third embodiment has a heat radiation suppression means 64 that suppresses heat radiation from the coolant by the radiator 38. The control device 30C is configured to suppress heat radiation from the coolant by the radiator 38 by controlling the heat radiation suppression means 64 while the internal combustion engine 10 is automatically stopped. Except for this point, the cooling system 24C is the same as either one of the cooling system 24A for the internal combustion engine 10 according to the first embodiment or the cooling system 24B for the internal combustion engine 10 according to the second embodiment. The heat radiation suppression means 64 is configured, for example, by a shutter 66 provided in front of the radiator 38 on the vehicle. When the shutter 66 is closed, heat radiation from the coolant by the radiator 38 is suppressed, and when the shutter 66 is opened, heat radiation from the coolant by the radiator 38 is promoted.

[0043] The heat radiation suppression means 64 is configured, for example, with a bypass path 68 that bypasses the radiator 38, and a control valve 72 that controls the flow rate of the coolant flowing to the radiator 38 and the flow rate of the coolant flowing to the bypass path 68. Closing the control valve 72 or reducing the opening of the control valve 72 suppresses heat radiation from the coolant by the radiator 38, and opening the control valve 72 or increasing the opening of the control valve 72 promotes heat radiation from the coolant by the radiator 38.

[0044] In the cooling system 24C of the internal combustion engine 10 according to the third embodiment, the control device 30C is configured to control the control valves 72, 74 so that the cooling water bypasses the radiator 38 and the oil cooler 40 while the internal combustion engine 10 is stopped.

[0045] For example, the control device 30C controls the control valves 72 and 74 so that the cooling water bypasses the radiator 38 and the oil cooler 40 while the internal combustion engine 10 is automatically stopped and the electric pump 28 is operating.

[0046] According to the cooling system 24C of the internal combustion engine 10 of embodiment 3, the heat dissipation suppression means 64 is controlled during automatic stop of the internal combustion engine 10 to suppress heat dissipation of the coolant by the radiator 38, making it difficult for the coolant to cool and preventing the temperature difference T between the coolant and the lubricating oil from becoming large. [Explanation of symbols]

[0047] 1 vehicle 10 Internal combustion engine 12,14 Traction motor 16. Generator 18. Running battery 20,22 Drive wheels 24, 24A, 24B, 24C Cooling system (internal combustion engine cooling system) 26 Cooling circuit 28 Electric Pump (EWP) 30, 30A, 30B, 30C Control unit (HVECU) 32 Cylinder block 34 Cylinder head 36 Water Jacket 38 Radiator 40 Oil cooler 42 EGR cooler 44 Radiator fan 46 Means for determining whether a vehicle is running or stopped 48 Automatic stop judgment means 50 Water temperature acquisition means 52 Oil temperature acquisition means 54 Wheel speed sensor 56 Engine control unit (engine ECU) 58,60 Temperature sensor 62 Prediction Department 64 Heat radiation suppression means 66 Shutter 68,70 Bypass route 72,74 Control valve

Claims

1. an internal combustion engine capable of automatic stopping and automatic restart; an electric pump that is driven while the internal combustion engine is running to circulate cooling water through the internal combustion engine and that stops driving in response to an automatic stop of the internal combustion engine; a water temperature acquisition means for acquiring the temperature of the cooling water; an oil temperature acquisition means for acquiring the temperature of the lubricating oil circulating in the internal combustion engine; a control device for controlling the operation of the electric pump; Equipped with the control device starts operation of the electric pump when a temperature difference between the cooling water and the lubricating oil becomes equal to or greater than a predetermined first temperature during automatic stop of the internal combustion engine. Cooling system of an internal combustion engine.

2. the control device starts operation of the electric pump when a temperature difference between the cooling water and the lubricating oil is equal to or higher than the first temperature and the temperature of the cooling water is lower than a predetermined second temperature during automatic stop of the internal combustion engine.

2. The cooling system for an internal combustion engine according to claim 1.

3. a prediction unit that predicts a restart of the internal combustion engine, the control device starts operation of the electric pump when a temperature difference between the cooling water and the lubricating oil is equal to or higher than the first temperature and when a restart of the internal combustion engine is predicted.

3. The cooling system for an internal combustion engine according to claim 1 or 2.

4. the control device increases the output of the electric pump when a temperature difference between the cooling water and the lubricating oil does not decrease after the electric pump starts operating.

3. The cooling system for an internal combustion engine according to claim 1 or 2.

5. a radiator interposed in the cooling water circulation path; a heat radiation suppression means for suppressing heat radiation from the cooling water by the radiator, the control device controls the heat radiation suppression means to suppress heat radiation of the coolant by the radiator during automatic stop of the internal combustion engine.

3. The cooling system for an internal combustion engine according to claim 1 or 2.

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