Engine cooling system

Abstract

To provide an engine cooling system for improving control accuracy of a cooling water flow rate.SOLUTION: A control device configured to calculate a target rotational speed of the engine water pump based on a target flow rate of cooling water flowing through the engine water pump, an opening degree of the thermostat, and a rotational speed of the heater water pump, and to control the rotational speed of the engine water pump to the target rotational speed, wherein the control device calculates the target rotational speed to be higher as the target flow rate is larger, calculates the target rotational speed to be higher as the opening degree of the thermostat is smaller, and lowers the target rotational speed by a predetermined lowering rotational speed in accordance with the rotational speed of the heater water pump and the opening degree of the thermostat, the electronic control unit is configured to calculate the reduced rotational speed to be larger as a rotational speed of the heater water pump is higher, and calculate the reduced rotational speed to be larger as an opening degree of the thermostat is smaller.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an engine cooling system. [Background technology]

[0002] BACKGROUND ART There is an engine cooling system that includes a cooling circuit that circulates cooling water between an engine, a heater core for heating, and a radiator using a water pump (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] WO2016 / 059791 Summary of the Invention [Problem to be solved by the invention]

[0004] Some vehicles are equipped with an engine water pump and a heater core water pump, which circulate coolant through the engine and heater core, respectively. A thermostat may also be installed between the engine and the radiator. In such cases, it is possible to control the flow rate of coolant through the engine water pump to a target flow rate by controlling the rotation speed of the engine water pump to a target rotation speed. However, the rotation speed of the heater water pump and the opening of the thermostat may affect the accuracy of controlling the flow rate of coolant through the engine water pump.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an engine cooling system that improves the accuracy of control of the flow rate of cooling water passing through an engine water pump. [Means for solving the problem]

[0006] The object of the present invention is to provide a cooling circuit including an engine water pump that circulates cooling water through an engine, and a heater water pump that circulates cooling water through a heater core for heating, in which cooling water circulates between the engine and the heater core when a thermostat is fully closed, and in which a portion of the cooling water that has passed through the engine flows into the heater core and then flows back into the engine when the thermostat is fully open, and a portion of the cooling water that has passed through the engine flows into a radiator and then flows back into the engine, and a cooling circuit that controls a target flow rate of cooling water that flows through the engine water pump, an opening of the thermostat, and a rotational speed of the heater water pump. This can be achieved by an engine cooling system that includes a control device that calculates a target rotation speed of the engine water pump and controls the rotation speed of the engine water pump to the target rotation speed, wherein the control device calculates the target rotation speed to be higher the greater the target flow rate, calculates the target rotation speed to be higher the smaller the opening of the thermostat, and reduces the target rotation speed by a predetermined reduced rotation speed depending on the rotation speed of the heater water pump and the opening of the thermostat, calculates the reduced rotation speed to be higher the higher the rotation speed of the heater water pump, and calculates the reduced rotation speed to be higher the smaller the opening of the thermostat.

[0007] The control device may calculate the reduced rotation speed as zero regardless of the rotation speed of the heater water pump when the thermostat is in a fully open state.

[0008] The cooling circuit may include an opening / closing valve that adjusts the opening rate of the path through which the cooling water that has passed through the engine passes through the engine again without passing through the radiator, and the control device may calculate the target rotation speed to be higher as the opening rate is smaller. [Effects of the Invention]

[0009] An engine cooling system can be provided that improves the accuracy of control of the flow rate of cooling water passing through the engine water pump. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is an explanatory diagram of an engine cooling system. [Figure 2] 2A to 2F are explanatory diagrams showing the communication state of the four-way valve. [Figure 3] FIG. 3A is an explanatory diagram of the cooling water flow path when the thermostat is in a fully closed state, and FIG. 3B is an explanatory diagram of the cooling water flow path when the thermostat is in a fully open state. [Figure 4] FIG. 4 is a flowchart illustrating the flow rate control of the EWP executed by the ECU. [Figure 5] 5A to 5C are diagrams illustrating examples of maps that define target rotation speeds of the EWP corresponding to target flow rates of cooling water passing through the EWP. [Figure 6] FIG. 6 is a diagram showing an example of a map that defines a target rotation speed of the EWP corresponding to a target flow rate of the cooling water passing through the EWP. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Engine cooling system] 1 is an explanatory diagram of an engine cooling system 1. The engine cooling system 1 is mounted on, for example, a vehicle. The engine cooling system 1 has an engine cooling circuit 2 and an ECU (Electronic Control Unit) 100. The engine cooling circuit 2 includes an engine 10, an engine water pump (hereinafter referred to as EWP) 12, a radiator 14, a reserve tank 16, a temperature sensor 18, a heater core 20, a heater water pump (hereinafter referred to as HWP) 22, a heater 24, a thermostat 30, a four-way valve 40, and a heat exchanger 50.

[0012] The engine 10 is a power source for driving the vehicle. The EWP 12 is an electric water pump that circulates coolant through the engine 10 by pumping the coolant toward the engine 10 in the direction of the arrows in FIG. 1 . The radiator 14 cools the coolant by exchanging heat between the coolant and the air outside the vehicle. The reserve tank 16 stores excess coolant. The heater core 20 heats the vehicle interior using the heat of the coolant. The HWP 22 is an electric water pump that circulates coolant through the heater core 20 by drawing coolant from the heater core 20 in the direction of the arrows in FIG. 1 . The heater 24 heats the coolant when the coolant temperature is insufficient to heat the vehicle interior using the heater core 20.

[0013] The thermostat 30 is in a fully closed state when the temperature of the coolant flowing into the thermostat 30 is below a first temperature, and is in a fully open state when the temperature of the coolant flowing into the thermostat 30 is at or above a second temperature that is higher than the first temperature. Furthermore, the thermostat 30 opens more when the temperature of the coolant flowing into the thermostat 30 is at or above the first temperature and below the second temperature, and the higher the temperature of the coolant is. For example, before the engine 10 has warmed up completely, the temperature of the coolant flowing into the thermostat 30 is below the first temperature, and after the warm-up has completed, the temperature of the coolant flowing into the thermostat 30 is at or above the second temperature. The flow paths of the coolant when the thermostat 30 is in the fully closed state and the fully open state will be described in detail below.

[0014] The four-way valve 40 switches the communication state of the four paths, thereby allowing the cooling water to flow through predetermined paths, which will be described in detail later. The four-way valve 40 includes a rotor rotatably housed in a housing and an actuator that drives the rotor. The communication state of the four paths is switched depending on the rotational position of the rotor, which is controlled by the actuator.

[0015] The heat exchanger 50 exchanges heat between the coolant flowing through the engine cooling circuit 2 and the coolant flowing through a battery cooling circuit for cooling a battery (not shown).

[0016] The ECU 100 is an electronic control unit including a processing circuit for performing various arithmetic operations related to vehicle driving control and a memory for storing control programs and data. The ECU 100 acquires the temperature of the coolant based on a temperature sensor 18. The ECU 100 controls the rotation speeds of the EWP 12 and the HWP 22, the amount of electricity supplied to the heater 24, and the communication state of the four-way valve 40 in accordance with the operating state of the engine 10, a heating request, and a cooling request for the battery. As will be described in detail later, the ECU 100 calculates a target rotation speed of the EWP 12 based on a target flow rate of the coolant flowing through the EWP 12, and controls the rotation speed of the EWP 12 to the target rotation speed.

[0017] The thermostat 30 is disposed at the upstream end of the path 61, and the downstream end is connected to the four-way valve 40, with the EWP 12 and the engine 10 disposed along the way. The upstream end of the path 62 is connected to the four-way valve 40, and the downstream end is connected to the thermostat 30, with the heater core 20, the HWP 22, and the heater 24 disposed along the way. The upstream end of the path 63 is connected to the path 62 between the heater 24 and the thermostat 30, and the downstream end is connected to the four-way valve 40. The upstream end of the path 64 is connected to the path 61 between the engine 10 and the four-way valve 40, and the downstream end is connected to the path 62 between the heater 24 and the thermostat 30. The temperature sensor 18 is provided at the location where the paths 61 and 64 are connected. The upstream end of the path 65 is connected to the four-way valve 40, and the downstream end is connected to the path 62 between the heater core 20 and the HWP 22, with the heat exchanger 50 located midway. The upstream end of the path 66 is connected to the path 61 between the engine 10 and the temperature sensor 18, and the downstream end is connected to the thermostat 30, with the radiator 14 and the reserve tank 16 located midway.

[0018] [4-way valve] Next, the four-way valve 40 will be described. FIGS. 2A to 2F are explanatory diagrams of the communication states of the four-way valve 40. As the rotor of the four-way valve 40 rotates in one direction, the communication state is switched in the order of FIGS. 2A to 2F. In FIG. 2A, path 63 and path 62 are connected, and paths 61 and 65 are blocked. In this state, the EWP 12 is stopped and the HWP 22 is operating. The coolant circulates through the heater core 20 and the heater 24 via a portion of path 62 and path 63. The aperture ratio of the opening in the four-way valve 40 that connects path 63 and path 62 is at its maximum. In FIG. 2A, the rotor of the four-way valve 40 is in its initial position. As the rotor rotates in one direction from the initial position, the aperture ratio of the opening that connects path 63 and path 62 decreases, and the aperture ratio of the opening that connects path 63 and path 65 increases, as shown in FIG. 2B.

[0019] In Fig. 2B, path 63 communicates with paths 62 and 65, and path 61 is blocked. In this state, EWP 12 is stopped and HWP 22 is operating. Coolant circulates through heater core 20 and heater 24 via part of path 62 and path 63, and circulates through heat exchanger 50 via path 65. When the rotor rotates in one direction from Fig. 2B, the opening ratio of the opening communicating path 63 and path 62 decreases to zero, and the opening ratio of the opening communicating path 63 and path 65 increases to its maximum, as shown in Fig. 2C.

[0020] In FIG. 2C, path 63 and path 65 are connected, and path 61 and path 62 are blocked. In this state, EWP 12 is stopped and HWP 22 is operating. Cooling water circulates through heat exchanger 50 and heater 24 via part of path 62, path 63, and path 65. The aperture ratio of the opening that connects path 63 and path 65 of four-way valve 40 is maximum. When the rotor rotates in one direction from FIG. 2C, the aperture ratio of the opening that connects path 63 and path 65 decreases, and the aperture ratio of the opening that connects path 61 and path 62 increases, as shown in FIG. 2D.

[0021] In FIG. 2D , path 63 and path 65 are connected, and path 61 and path 62 are connected. Note that paths 63 and 65 are not connected to paths 61 and 62. In this state, EWP 12 and HWP 22 are operating. The coolant circulates through heat exchanger 50 and heater 24 via part of path 62, path 63, and path 65, and then circulates through engine 10, heater core 20, and heater 24 via paths 61 and 62. Therefore, paths 61 and 62 correspond to paths through which the coolant that has passed through engine 10 passes again through engine 10 without passing through radiator 14. Note that when thermostat 30 is fully open, the coolant also circulates through path 66 to radiator 14 and reserve tank 16. As the rotor rotates in one direction from Figure 2D, the opening ratio of the opening connecting path 63 and path 65 decreases to zero, and the opening ratio of the opening connecting path 61 and path 62 increases to its maximum, as shown in Figure 2E.

[0022] In FIG. 2E, path 61 and path 62 are connected, and paths 63 and 65 are blocked. In this state, at least EWP 12 is operating. Coolant circulates through engine 10, heater core 20, and heater 24 via paths 61 and 62. The aperture ratio of the opening in four-way valve 40 that connects paths 61 and 62 is at its maximum. When thermostat 30 is fully open, coolant also circulates to radiator 14 and reserve tank 16 via path 66. As the rotor rotates in one direction from FIG. 2E, the aperture ratio of the opening that connects paths 61 and 62 decreases, and the aperture ratio of the opening that connects paths 61 and 65 increases, as shown in FIG. 2F.

[0023] 2F, path 61 communicates with paths 62 and 65, and path 63 is blocked. The coolant is circulated through engine 10, heater core 20, heater 24, and heat exchanger 50 via paths 61, 62, and 65 by at least EWP 12. Therefore, paths 61, 62, and 65 correspond to paths through which the coolant that has passed through engine 10 passes through engine 10 again without passing through radiator 14. When thermostat 30 is fully open, the coolant also circulates through path 66 to radiator 14 and reserve tank 16.

[0024] The sum of the aperture ratio of the opening connecting path 61 and path 62 in FIG. 2F and the aperture ratio of the opening connecting path 61 and path 65 in FIG. 2E is lower than the maximum aperture ratio of the opening connecting path 61 and path 62 in FIG. 2E. For example, the aperture ratio of the opening connecting path 61 and path 62 in FIG. 2E is 100%. The aperture ratio of the opening connecting path 61 and path 62 in FIG. 2F is 40%, and the aperture ratio of the opening connecting path 61 and path 65 is 40%. Therefore, the aperture ratio of path 61 in FIG. 2F is 80% in total, which is lower than the aperture ratio of 100% in FIG. 2E.

[0025] Therefore, the aperture ratio of the opening connecting path 61 and path 62 in FIG. 2C increases from zero to the state shown in FIG. 2D. Next, the aperture ratio of the opening connecting path 61 and path 62 reaches a maximum, resulting in the state shown in FIG. 2E. Next, the aperture ratio of the opening connecting path 61 with paths 62 and 65 gradually decreases to the state shown in FIG. 2F. In this way, the four-way valve 40 is an example of an on-off valve that adjusts the aperture ratio of the path through which the coolant that has passed through the engine 10 passes again through the engine 10 without passing through the radiator 14. The ECU 100 obtains the aperture ratio of such a path by referring to a map defined according to the target rotational position of the rotor.

[0026] [thermostat] Next, the fully closed and fully open states of the thermostat 30 will be described. Fig. 3A is an explanatory diagram of the coolant flow paths when the thermostat 30 is in the fully closed state. Fig. 3A shows a state in which the four-way valve 40 connects paths 61 and 62 and blocks paths 63 and 65. The coolant flows through the EWP 12, engine 10, four-way valve 40, heater core 20, HWP 22, heater 24, and thermostat 30 in this order. The coolant flows through path 64 from the temperature sensor 18 toward path 62. Because the thermostat 30 is in the fully closed state, the coolant does not flow through the radiator 14, allowing the engine 10 to warm up.

[0027] FIG. 3B is an explanatory diagram of the coolant flow paths when the thermostat 30 is fully open. Like FIG. 3A, FIG. 3B also illustrates a state in which the four-way valve 40 connects paths 61 and 62 and blocks paths 63 and 65. A portion of the coolant that has passed through the engine 10 flows to the heater core 20 via path 62, and the remainder of the coolant that has passed through the engine 10 flows to the radiator 14 via path 66. The coolant that has passed through the heater core 20, HWP 22, and heater 24 via path 62 also flows into the thermostat 30. The coolant that has passed through the radiator 14 and reserve tank 16 via path 66 also flows into the thermostat 30. The coolant that has flowed into the thermostat 30 from both directions in this way flows through the EWP 12 and the engine 10 via path 61. Because a portion of the coolant also flows through the radiator 14 in this way, the coolant is prevented from becoming too hot.

[0028] [EWP flow control] 4 is a flowchart illustrating the flow rate control of the EWP 12 executed by the ECU 100. The ECU 100 acquires the target flow rate of the coolant flowing through the EWP 12, the opening degree of the thermostat 30, the rotation speed of the HWP 22, and the opening rate of the path 61 defined by the four-way valve 40 (step S1). The target flow rate of the coolant flowing through the EWP 12 is calculated by the engine 100 mainly in accordance with the operating state of the engine 10. The opening degree of the thermostat 30 is estimated by the ECU 100 based on the temperature of the coolant detected by the temperature sensor 18, for example. The ECU 100 acquires the target rotation speed of the HWP 22, which is calculated in response to a heating request, for example, as the rotation speed of the HWP 22. The ECU 100 acquires the opening rate of the path 61 by referring to a map that defines the opening rate of the path 61 in accordance with the target rotation position of the rotor of the four-way valve 40, for example, as described above.

[0029] Next, the ECU 100 calculates a target rotation speed of the EWP 12 to achieve the target flow rate based on the acquired information (step S2). The method for calculating the target rotation speed will be described in detail later. Next, the ECU 100 controls the duty ratio of the voltage applied to the EWP 12 so that the rotation speed of the EWP 12 becomes the target rotation speed (step S3). This allows the flow rate passing through the EWP 12 to be controlled to the target flow rate.

[0030] [Calculating the target rotation speed of the EWP] The ECU 100 calculates the target rotation speed of the EWP 12 by referring to the maps shown in Figures 5A to 6. Figures 5A to 6 are illustrations of maps that define the target rotation speed of the EWP 12 corresponding to the target flow rate of the cooling water passing through the EWP 12. Figure 5A is an illustration of a map that defines the target rotation speed of the EWP 12 corresponding to the target flow rate of the cooling water passing through the EWP 12 and the opening degree of the thermostat 30. The target rotation speed of the EWP 12 is defined to be a higher value as the target flow rate of the EWP 12 is larger.

[0031] 5A, the smaller the opening of the thermostat 30, the higher the target rotation speed of the EWP 12. This is because the smaller the opening of the thermostat 30, the lower the flow rate of the coolant that passes through the radiator 14 and reserve tank 16 shown in FIG. 3B and flows into the EWP 12 and engine 10 via the thermostat 30, even if the rotation speed of the EWP 12 is constant.

[0032] The target rotation speed of the EWP 12 is set to be reduced by a predetermined reduced rotation speed depending on the rotation speed of the HWP 22 and the opening of the thermostat 30. Figures 5B and 5C are explanatory diagrams of the reduced rotation speed of the target rotation speed depending on the rotation speed of the HWP 22 and the opening of the thermostat 30.

[0033] FIG. 5B is an explanatory diagram of the reduced rotation speed of the EWP 12 when the thermostat 30 is fully closed in the map of FIG. 5A. When the rotation speed of the HWP 22 is 0, the reduced rotation speed of the EWP 12 is calculated as zero. When the rotation speed of the HWP 22 is R1, the reduced rotation speed of the EWP 12 is calculated as D1. When the rotation speed of the HWP 22 is R2, which is higher than R1, the reduced rotation speed of the EWP 12 is calculated as D2, which is higher than D1. That is, the higher the rotation speed of the HWP 22, the larger the reduced rotation speed of the EWP 12 is calculated to be. This is because the higher the rotation speed of the HWP 22, the greater the flow rate of coolant flowing from the heater core 20, the HWP 22, and the heater 24 to the EWP 12 and the engine 10 via the thermostat 30. Therefore, the higher the rotation speed of the HWP 22, the larger the reduced rotation speed of the EWP 12 is calculated to be, and as a result, the target rotation speed of the EWP 12 is calculated to be smaller.

[0034] FIG. 5C is an explanatory diagram of the reduced rotation speed when the thermostat 30 is in a half-open state in the map of FIG. 5A. As in the fully closed state, when the rotation speed of the HWP 22 is 0, the reduced rotation speed of the EWP 12 is calculated as zero. When the rotation speed of the HWP 22 is rotation speed R1, the reduced rotation speed of the EWP 12 is calculated as rotation speed d1. When the rotation speed of the HWP 22 is rotation speed R2, the reduced rotation speed of the EWP 12 is calculated as rotation speed d2, which is larger than rotation speed d1. Here, rotation speed d1 is lower than rotation speed D1. Rotation speed d2 is lower than rotation speed D2. In other words, even if the rotation speed of the HWP 22 is the same, when the thermostat 30 is in a half-open state, the reduced rotation speed of the EWP 12 is lower than when the thermostat 30 is in a fully closed state. When the thermostat 30 is in a half-open state, unlike when the thermostat 30 is in a fully closed state, the coolant that has passed through the radiator 14 and reserve tank 16 flows into the EWP 12 and engine 10 via the thermostat 30. This is because the flow rate of the coolant flowing from the radiator 14 side into the EWP 12 is less affected by the rotation speed of the HWP 22.

[0035] When the thermostat 30 is fully open, the reduced rotation speed of the EWP 12 is calculated as zero, regardless of the rotation speed of the HWP 22. This is because when the thermostat 30 is fully open, the ratio of the flow rate of coolant flowing into the EWP 12 from the radiator 14 side to the flow rate of coolant flowing into the EWP 12 from the HWP 22 side is higher than when the thermostat 30 is half open or fully closed, and the rotation speed of the HWP 22 has less of an effect on the flow rate of coolant passing through the EWP 12. In this way, the smaller the opening of the thermostat 30, the larger the reduced rotation speed of the EWP 12 is calculated to be.

[0036] FIG. 6 is an example of a map that defines a target rotation speed of the EWP 12 according to the target flow rate of the coolant passing through the EWP 12 and the opening ratio of the path 61 of the four-way valve 40. FIG. 6 illustrates a map for the case where the thermostat 30 is in a half-open state. The smaller the opening ratio of the path 61, the higher the target rotation speed of the EWP 12 is defined. This is because the smaller the opening ratio of the path 61, the lower the flow rate of the coolant passing through the EWP 12 and the engine 10. Regardless of the open / closed state of the thermostat 30, the smaller the opening ratio of the path 61, the higher the target rotation speed of the EWP 12 is defined. The ECU 100 calculates the target rotation speed of the EWP 12 by referring to the multiple maps described above. This allows the flow rate of the coolant passing through the EWP 12 to be accurately controlled to the target flow rate.

[0037] 5A to 6, the target rotation speed of the EWP 12 is calculated based on the maps, but this is not limiting. For example, the target rotation speed of the EWP 12 may be calculated using an arithmetic expression that uses the target flow rate of the cooling water flowing through the EWP 12, the opening of the thermostat 30, the rotation speed of the HWP 22, and the opening rate of the path 61 defined by the four-way valve 40 as arguments.

[0038] Although an example has been described in which the reduced rotation speed is set to zero when the thermostat 30 is fully open, regardless of the rotation speed of the HWP 22, the present invention is not limited to this. For example, if the reduced rotation speed is calculated to be a larger value the smaller the opening of the thermostat 30, the reduced rotation speed may be calculated to be larger the greater the rotation speed of the HWP 22, even when the thermostat 30 is fully open.

[0039] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0040] 1 Engine Cooling System 2 Engine cooling circuit 10 Engine 12 Engine water pump 14 Radiator 20 Heater Core 22 Heater water pump 30 Thermostat 40 4-way valve (on-off valve)

Claims

1. a cooling circuit including an engine water pump that circulates cooling water through an engine and a heater water pump that circulates cooling water through a heater core for heating, whereby cooling water circulates between the engine and the heater core when the thermostat is fully closed, and whereby when the thermostat is fully open, a portion of the cooling water that has passed through the engine flows into the heater core and then flows back into the engine, and a portion of the cooling water that has passed through the engine flows into a radiator and then flows back into the engine; a control device that calculates a target rotation speed of the engine water pump based on a target flow rate of cooling water flowing through the engine water pump, an opening of the thermostat, and a rotation speed of the heater water pump, and controls the rotation speed of the engine water pump to the target rotation speed, The control device The larger the target flow rate, the higher the target rotation speed is calculated, The smaller the opening of the thermostat, the higher the target rotation speed is calculated, reducing the target rotation speed by a predetermined reduced rotation speed in accordance with the rotation speed of the heater water pump and the opening degree of the thermostat; The higher the rotation speed of the heater water pump, the larger the calculated reduced rotation speed. The engine cooling system calculates the reduced rotation speed to be greater as the opening of the thermostat becomes smaller.

2. 2. The engine cooling system according to claim 1, wherein the control device calculates the reduced rotation speed as zero regardless of the rotation speed of the heater water pump when the thermostat is in a fully open state.

3. the cooling circuit includes an on-off valve that adjusts an opening rate of a path through which the cooling water that has passed through the engine passes through the engine again without passing through the radiator, 3. The engine cooling system according to claim 2, wherein the control device calculates the target rotation speed to be higher as the opening ratio decreases.

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