Engine cooling system

Abstract

The objective is to provide an engine cooling system that suppresses engine water pump step-out. [Solution] An engine cooling system comprising: a cooling circuit having a circulation path through which coolant circulates between the engine and the heater core by an engine water pump that circulates coolant to the engine and a heater core water pump that circulates coolant to the heater core for heating; and a control device that controls the engine water pump and the heater core water pump, wherein the control device includes a first control unit that controls the heater core water pump so that a correlation value correlated with the head of the heater core water pump is less than or equal to an upper limit value that can prevent the engine water pump from losing synchronism when there is a request to drive the engine water pump in a stopped state, and a second control unit that starts driving the engine water pump when the heater core water pump is controlled so that the correlation value is less than or equal to the upper limit value.

Description

Technical Field

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

Background Art

[0002] There is an engine cooling system including a cooling circuit having a circulation path through which cooling water circulates by a water pump between an engine and a heater core for heating (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] There may be provided an engine water pump and a heater core water pump for circulating cooling water through the engine and the heater core, respectively. When the heater core water pump starts driving while the heater core water pump is in a driving state, the engine water pump may become out of adjustment due to the pressure of the cooling water conveyed from the heater core water pump. As a result, the controllability of the engine water pump may be reduced.

[0005] Therefore, an object of the present invention is to provide an engine cooling system that suppresses out-of-adjustment of an engine water pump.

Means for Solving the Problems

[0006] The above objective can be achieved by an engine cooling system comprising: a cooling circuit having a circulation path through which coolant circulates between the engine and the heater core by an engine water pump that circulates coolant to the engine and a heater core water pump that circulates coolant to the heater core for heating; and a control device that controls the engine water pump and the heater core water pump, wherein the control device includes a first control unit that controls the heater core water pump so that, when there is a request to drive the engine water pump in a stopped state, the correlation value correlated with the head of the heater core water pump is less than or equal to an upper limit value that can prevent the engine water pump from losing synchronism; and a second control unit that starts driving the engine water pump when the heater core water pump is controlled so that the correlation value is less than or equal to the upper limit value.

[0007] The cooling circuit includes a radiator path that communicates with the circulation path and through which coolant flows from the engine to the radiator without passing through the heater core, and a thermostat provided in the radiator path. The control device includes a setting unit for setting the upper limit value, and the setting unit may set the upper limit value to a lower value when the thermostat is fully closed than when the thermostat is fully open.

[0008] The cooling circuit has an on / off valve that adjusts the opening ratio of the circulation path, and the setting unit may set the upper limit to a higher value as the opening ratio decreases. [Effects of the Invention]

[0009] This system can provide an engine cooling system that suppresses engine water pump loss of synchronism. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is an explanatory diagram of the engine cooling system. [Figure 2] Figures 2A to 2F are explanatory diagrams illustrating the communication state of the four-way valve. [Figure 3]Figure 3A is an explanatory diagram of the coolant flow path when the thermostat is fully closed, and Figure 3B is an explanatory diagram of the coolant flow path when the thermostat is fully open. [Figure 4] Figure 4 is a flowchart illustrating the EWP drive start control performed by the ECU. [Figure 5] Figure 5 is a map that defines the relationship between the head of the HWP, the flow rate of the cooling water passing through the HWP, and the rotational speed of the HWP. [Figure 6] Figure 6 is a map that defines the relationship between the thermostat state, the path opening ratio, and the upper limit. [Modes for carrying out the invention]

[0011] [Engine Cooling System] Figure 1 is an explanatory diagram of the engine cooling system 1. The engine cooling system 1 is installed, for example, in 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 core water pump (hereinafter referred to as HWP) 22, a heating heater 24, a thermostat 30, a four-way valve 40, and a heat exchanger 50.

[0012] Engine 10 is the power source for the vehicle's movement. EWP 12 is an electric water pump that circulates coolant to engine 10 by pressurizing and sending coolant towards engine 10 in the direction of the arrow in Figure 1. Radiator 14 cools the coolant by exchanging heat between the coolant and the air outside the vehicle. Reserve tank 16 stores excess coolant. Heater core 20 heats the passenger compartment using the heat from the coolant. HWP 22 is an electric water pump that circulates coolant to heater core 20 by drawing coolant from heater core 20 in the direction of the arrow in Figure 1. Heating heater 24 heats the coolant when the temperature of the coolant is insufficient for heating the passenger compartment by heater core 20.

[0013] Thermostat 30 is fully closed when the temperature of the coolant flowing into it is below the first temperature, and fully open when the temperature of the coolant flowing into it is above the first temperature (second temperature or higher). Furthermore, when the temperature of the coolant flowing into it is above the first temperature but below the second temperature, the opening of the thermostat 30 increases as the coolant temperature increases. For example, before the engine 10 is fully warmed up, the temperature of the coolant flowing into thermostat 30 is below the first temperature, and after the engine is fully warmed up, the temperature of the coolant flowing into thermostat 30 is above the second temperature. The coolant flow path in the fully closed and fully open states of thermostat 30 will be described in detail later.

[0014] The four-way valve 40 circulates cooling water through predetermined paths, which will be described in more detail later, by switching the communication state of the four paths. The four-way valve 40 is equipped with a rotor rotatably housed within the housing and an actuator that drives the rotor. The communication state of the four paths is switched according to 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 the battery cooling circuit for cooling a battery (not shown).

[0016] The ECU100 is an electronic control unit comprising an arithmetic processing circuit that performs various calculations related to vehicle driving control, and a memory that stores control programs and data. The ECU100 acquires the temperature of the coolant based on the temperature sensor 18. The ECU100 controls the rotational speeds of the EWP12 and HWP22, the amount of current supplied to the heating heater 24, and the communication state of the four-way valve 40 in accordance with the operating state of the engine 10, heating requests, and battery cooling requests. The ECU100 functionally implements the first control unit, the second control unit, and the setting unit, which will be described in more detail later.

[0017] Route 61 has a thermostat 30 at its upstream end and is connected to a four-way valve 40 at its downstream end, with an EWP 12 and engine 10 located in between. Route 62 has a four-way valve 40 at its upstream end and is connected to a thermostat 30 at its downstream end, with a heater core 20, HWP 22, and heating heater 24 located in between. Routes 61 and 62 are examples of circulation routes in which cooling water circulates between the engine 10 and the heater core 20 when they are connected by the four-way valve 40. Route 63 has its upstream end connected between the heating heater 24 and thermostat 30 of route 62 and its downstream end connected to the four-way valve 40. Route 64 has its upstream end connected between the engine 10 and four-way valve 40 of route 61 and its downstream end connected between the heating heater 24 and thermostat 30 of route 62. A temperature sensor 18 is provided at the point where routes 61 and 64 are connected. Route 64 is connected to routes 61 and 62 and is an example of a bypass route in which the coolant that has passed through the engine 10 bypasses the heater core 20 and flows back into the engine 10. Route 65 has its upstream end connected to a four-way valve 40 and its downstream end connected between the heater core 20 and HWP 22 of route 62, with a heat exchanger 50 located in between. Route 66 has its upstream end connected between the engine 10 and the temperature sensor 18 of route 61 and its downstream end connected to a thermostat 30, with a radiator 14 and a reserve tank 16 located in between. Route 66 is an example of a radiator route.

[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 states are switched in the order of FIGS. 2A to 2F. In FIG. 2A, the path 63 and the path 62 are in communication, and the paths 61 and 65 are blocked. In this state, the EWP12 is stopped and the HWP22 is driven. The cooling water circulates through a part of the path 62 and the path 63 to the heater core 20 and the heating heater 24. The opening ratio of the opening that connects the path 63 and the path 62 of the four-way valve 40 is the maximum. In FIG. 2A, the rotor of the four-way valve 40 is in the initial position. As the rotor rotates in one direction from the initial position, the opening ratio of the opening that connects the path 63 and the path 62 decreases, and the opening ratio of the opening that connects the path 63 and the path 65 increases as shown in FIG. 2B.

[0019] In FIG. 2B, the path 63 is in communication with the paths 62 and 65, and the path 61 is blocked. In this state, the EWP12 is stopped and the HWP22 is driven. The cooling water circulates through a part of the path 62 and the path 63 to the heater core 20 and the heating heater 24, and circulates through the heat exchanger 50 via the path 65. As the rotor rotates in one direction from FIG. 2B, the opening ratio of the opening that connects the path 63 and the path 62 decreases to zero as shown in FIG. 2C, and the opening ratio of the opening that connects the path 63 and the path 65 increases to the maximum.

[0020] In FIG. 2C, the path 63 and the path 65 are in communication, and the paths 61 and 62 are blocked. In this state, the EWP12 is stopped and the HWP22 is driven. The cooling water circulates through a part of the path 62, the path 63, and the path 65 to the heat exchanger 50 and the heating heater 24. The opening ratio of the opening that connects the path 63 and the path 65 of the four-way valve 40 is the maximum. As the rotor rotates in one direction from FIG. 2C, the opening ratio of the opening that connects the path 63 and the path 65 decreases, and the opening ratio of the opening that connects the path 61 and the path 62 increases as shown in FIG. 2D.

[0021] In Figure 2D, paths 63 and 65 are connected, and paths 61 and 62 are connected. Paths 63 and 65 are not connected to paths 61 and 62. In this state, EWP12 and HWP22 are operating. Coolant circulates through part of path 62, paths 63 and 65 to the heat exchanger 50 and heating heater 24, and through paths 61 and 62 to the engine 10, heater core 20, and heating heater 24. Therefore, paths 61 and 62 correspond to paths through which coolant that has passed through the engine 10 passes through the engine 10 again without going through the radiator 14. When the thermostat 30 is fully open, coolant also circulates through path 66 to the radiator 14 and reserve tank 16. As the rotor rotates in one direction, as shown in 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 Figure 2E, paths 61 and 62 are connected, while paths 63 and 65 are blocked. In this state, at least the EWP 12 is driven. Coolant circulates through paths 61 and 62 to the engine 10, heater core 20, and heating element 24. The opening ratio of the opening of the four-way valve 40 connecting paths 61 and 62 is at its maximum. When the thermostat 30 is fully open, coolant also circulates through path 66 to the radiator 14 and reserve tank 16. As the rotor rotates in one direction from Figure 2E, the opening ratio of the opening connecting paths 61 and 62 decreases, and the opening ratio of the opening connecting paths 61 and 65 increases, as shown in Figure 2F.

[0023] In Figure 2F, paths 61, 62, and 65 are connected, while path 63 is blocked. Coolant circulates through paths 61, 62, and 65 via at least the EWP 12 to the engine 10, heater core 20, heating heater 24, and heat exchanger 50. Therefore, paths 61, 62, and 65 are examples of circulation paths through which coolant circulates between the engine 10 and the heater core 20 when these paths are connected by the four-way valve 40. When the thermostat 30 is fully open, coolant also circulates through path 66 to the radiator 14 and the reserve tank 16.

[0024] The sum of the opening ratios of the openings connecting paths 61 and 62 and the opening ratio of the openings connecting paths 61 and 65 in Figure 2F is lower than the maximum opening ratio of the openings connecting paths 61 and 62 in Figure 2E. For example, let's assume the opening ratio of the openings connecting paths 61 and 62 in Figure 2E is 100%. In Figure 2F, the opening ratio of the openings connecting paths 61 and 62 is 40%, and the opening ratio of the openings connecting paths 61 and 65 is 40%. Therefore, the total opening ratio of path 61 in Figure 2F is 80%, which is lower than the 100% opening ratio in Figure 2E.

[0025] Therefore, the opening ratio of the opening connecting path 61 and path 62 in Figure 2C increases from zero to the state shown in Figure 2D. Next, the opening ratio of the opening connecting path 61 and path 62 reaches its maximum, reaching the state shown in Figure 2E. Then, the opening ratio of the opening connecting path 61 and paths 62 and 65 gradually decreases to the state shown in Figure 2F. The ECU 100 obtains the opening ratio of such paths by referring to a map defined according to the target rotation position of the rotor. The four-way valve 40 is an example of an on-off valve.

[0026] [thermostat] Next, the fully closed and fully open states of the thermostat 30 will be explained. Figure 3A is an explanatory diagram of the coolant flow path when the thermostat 30 is in the fully closed state. Figure 3A shows the state in which the four-way valve 40 connects paths 61 and 62 and blocks paths 63 and 65. The coolant flows in the following order: EWP 12, engine 10, four-way valve 40, heater core 20, HWP 22, heating heater 24, and thermostat 30. Coolant flows from the temperature sensor 18 to path 62 in path 64. Since the thermostat 30 is in the fully closed state, coolant does not flow to the radiator 14, and the engine 10 is warmed up.

[0027] Figure 3B is an explanatory diagram of the coolant flow path when the thermostat 30 is fully open. Similar to Figure 3A, Figure 3B shows the 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 remaining coolant that has passed through the engine 10 flows to the radiator 14 via path 66. In addition, the coolant that has passed through the heater core 20, HWP 22, and heating heater 24 via path 62 flows into the thermostat 30. Furthermore, the coolant that has passed through the radiator 14 and reserve tank 16 via path 66 also flows into the thermostat 30. In this way, the coolant that has flowed into the thermostat 30 from both directions circulates through the EWP 12 and engine 10 via path 61. In this way, a portion of the coolant also circulates to the radiator 14, which suppresses the overheating of the coolant.

[0028] [EWP drive start control] Figure 4 is a flowchart illustrating the EWP12 drive start control performed by the ECU100. The ECU100 determines whether there is a request for communication between path 61 and path 62, or a request for communication between path 61, path 62, and path 65, and whether there is a request to drive the EWP12 (step S1). The above communication request is a request for the four-way valve 40 to enter the communication state shown in Figures 2D to 2F. This communication state is the state in which the cooling water transported by the HWP22 flows through the EWP12. If the answer in step S1 is No, this control is terminated.

[0029] If the answer in step S1 is Yes, the ECU 100 calculates the head [kPa] of HWP22 by referring to the map in Figure 5 (step S2). Figure 5 is a map that defines the relationship between the head of HWP22, the flow rate of cooling water passing through HWP22 [L / min], and the rotational speed of HWP22 [rpm]. The map in Figure 5 is defined based on experimental and simulation results. As shown in Figure 5, the less the flow rate of cooling water passing through HWP22, and the higher the rotational speed of HWP22, the greater the head of HWP22. The ECU 100 calculates the head of HWP22 based on the target flow rate of cooling water passing through HWP22 and the target rotational speed or instructed rotational speed by referring to the map in Figure 5. The greater the head of HWP22, the greater the flow rate of cooling water passing through EWP12 when EWP12 is stopped in the connected state shown in Figures 2D to 2F, due to the driving of HWP22. Alternatively, instead of the map in Figure 5, the head of HWP22 may be calculated using a formula that takes the flow rate of the cooling water passing through HWP22 and the rotational speed of HWP22 as arguments.

[0030] Next, the ECU 100, based on the opening degree of the thermostat 30 and the opening ratio of the path 61, refers to the map in Figure 6 and sets an upper limit value for limiting the head of the HWP 22, which will be described later (step S3). The upper limit value is set to the upper limit of the head of the HWP 22 that prevents the EWP 12 from losing step when the EWP 12 is started to drive in the communication state shown in Figures 2D to 2F. Step S3 is an example of the process performed by the setting unit.

[0031] Figure 6 is a map that defines the relationship between the state of the thermostat 30 and the opening ratio and upper limit of the path 61. Figure 6 defines the upper limit for the case where the thermostat 30 is fully closed and the case where it is fully open. The map in Figure 6 is defined based on experimental and simulation results. As shown in Figure 6, the upper limit is set to a lower value when the thermostat 30 is fully closed than when it is fully open. This is because when the thermostat 30 is fully closed, the total volume of the path through which the cooling water flows is smaller than when it is fully open, and the pressure exerted on the EWP 12 by the cooling water transported from the HWP 22 is greater. Also, as shown in Figure 6, the smaller the opening ratio of the path 61, the higher the upper limit is set. This is because the smaller the opening ratio of the path 61, the greater the pressure loss of the cooling water, and the less pressure exerted on the EWP 12 by the cooling water transported from the HWP 22. Also, as shown in Figure 6, the smaller the opening ratio of the path 61, the smaller the difference in the upper limit between the case where the thermostat 30 is fully open and the case where it is fully closed. This is because a smaller opening ratio in the path 61 reduces the influence that the state of the thermostat 30 has on the pressure experienced by the EWP 12.

[0032] 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 opening ratio of the path 61 is estimated by the ECU 100 according to the target rotational position of the rotor of the four-way valve 40 in the communication request in step S1. In the map of Figure 6, the upper limit of the opening ratio of the path 61 changes continuously, but it may also change in steps. Instead of the map of Figure 6, the upper limit may be calculated using a formula that takes the opening degree of the thermostat 30 and the opening ratio of the path 61 as arguments.

[0033] Next, the ECU 100 limits the head of the HWP 22 to below the upper limit (step S4). Specifically, if the calculated head of the HWP 22 exceeds the upper limit, the ECU 100 reduces the rotational speed of the HWP 22 to a rotational speed that keeps the head of the HWP 22 below the upper limit. EWP 12 losing synchronism occurs when the impeller of the EWP 12 receives an external force from the cooling water due to the head of the HWP 22, causing the rotor position of the EWP 12 to deviate from the desired position. When the EWP 12 loses synchronism, it becomes difficult to control the rotor position of the EWP 12 with high precision, and the controllability of the EWP 12 may decrease. Step S4 is an example of a process performed by the first control unit.

[0034] Next, the ECU 100 controls the four-way valve 40 in accordance with the communication request in step S1 to achieve one of the communication states shown in Figures 2D to 2F, and starts driving the EWP 12 (step S5). In this way, the EWP 12 is driven when the communication state is achieved with the head of the HWP 22 limited to below the upper limit value mentioned above. As a result, step S5 is suppressed, and the decrease in the controllability of the EWP 12 is also suppressed. Step S5 is an example of a process executed by the second control unit.

[0035] Furthermore, as described above, the upper limit is set according to the fully open and fully closed states of the thermostat 30 and the opening ratio of the path 61. Therefore, the upper limit is set high enough to suppress the EWP12 from losing synchronism, and the output of the HWP22 is not restricted more than necessary.

[0036] The higher the rotational speed of HWP22, the greater the head of HWP22. Therefore, the rotational speed of HWP22 is correlated with the head. Accordingly, for example, the rotational speed of HWP22 may be limited to an upper limit that prevents EWP12 from losing step when the EWP12 is started to drive in the connected state shown in Figures 2D to 2F.

[0037] Although embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of symbols]

[0038] 1. Engine Cooling System 2. Engine cooling circuit (cooling circuit) 10 Engines 12. Engine water pump 20 Heater Cores 22 Heater core water pump 30 Thermostats 40 4-way valve (on / off valve) Routes 61 and 62 (Circular Routes) 100 ECU (Control Unit, First Control Unit, Second Control Unit, Setting Unit)

Claims

1. A cooling circuit having a circulation path through which coolant circulates between the engine and the heater core, comprising an engine water pump that circulates coolant to the engine and a heater core water pump that circulates coolant to the heater core for heating, The system includes a control device for controlling the engine water pump and the heater core water pump, The control device is A first control unit controls the heater core water pump so that, when there is a request to drive the engine water pump while it is stopped, the correlation value that correlates with the head of the heater core water pump is less than or equal to an upper limit that prevents the engine water pump from losing synchronism. An engine cooling system comprising: a second control unit that starts driving the engine water pump while the heater core water pump is controlled so that the correlation value is less than or equal to the upper limit value.

2. The cooling circuit includes a radiator path that communicates with the circulation path and through which coolant flows from the engine to the radiator without passing through the heater core, and a thermostat provided in the radiator path. The control device includes a setting unit for setting the upper limit value, The engine cooling system according to claim 1, wherein the setting unit sets the upper limit to a lower value when the thermostat is fully closed than when the thermostat is fully open.

3. The cooling circuit has an on / off valve that adjusts the opening ratio of the circulation path, The engine cooling system according to claim 2, wherein the setting unit sets the upper limit to a higher value as the opening ratio decreases.

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