Engine cooling system

Abstract

The present invention provides an engine cooling system that can appropriately control the flow rate of cooling water passing through the heater core. [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 water pump that circulates coolant to the heater core for heating; a control device that controls the engine water pump; an acquisition unit that acquires the target flow rate of coolant in the heater core water pump and the rotational speed of the heater water pump; and a control unit that calculates the target flow rate of coolant flowing to the engine water pump based on a rotational speed ratio which is the ratio of the rotational speed of the heater water pump to the rotational speed of the engine water pump, a distribution ratio which is the ratio of the flow rate of coolant in the heater water pump to the flow rate of coolant in the engine water pump and the target flow rate of the heater core, and controls the rotational speed of the engine water pump.

Description

Technical Field

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

Background Art

[0002] There is an engine cooling system provided with a cooling circuit including a circulation path in 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 circulation path to the engine and the heater core, respectively. For example, it is conceivable to control the rotational speed of the heater water pump based on the target flow rate of the cooling water passing through the heater core water pump (hereinafter referred to as the heater core target flow rate) calculated according to the heating demand. In this case, if the target flow rate of the cooling water passing through the engine water pump (hereinafter referred to as the engine target flow rate) is calculated without considering the heater core target flow rate, there is a possibility that the flow rate of the cooling water passing through the heater core water pump cannot be appropriately controlled so as to be the heater core target flow rate due to the influence of the flow rate of the cooling water passing through the engine water pump.

[0005] Therefore, an object of the present invention is to provide an engine cooling system capable of appropriately controlling the flow rate of the cooling water passing through the heater core 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 water pump that circulates coolant to a heater core for heating; and a control device that controls the engine water pump, the system comprising: an acquisition unit that acquires a heater core target flow rate, which is a target flow rate of coolant passing through the heater core water pump, and the rotational speed of the heater water pump; a calculation unit that calculates the distribution ratio based on the acquired rotational speed of the heater water pump by referring to the correlation between the rotational speed ratio, which is the ratio of the rotational speed of the heater water pump to the rotational speed of the engine water pump, and the distribution ratio, which is the ratio of the flow rate of coolant passing through the heater water pump to the flow rate of coolant passing through the engine water pump; and a control unit that calculates an engine target flow rate, which is a target flow rate of coolant flowing to the engine water pump, based on the calculated distribution ratio and the heater core target flow rate, and controls the rotational speed of the engine water pump according to the engine target flow rate. [Effects of the Invention]

[0007] This system provides an engine cooling system that can appropriately control the flow rate of coolant passing through the heater core water pump. [Brief explanation of the drawing]

[0008] [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 rotation speed control performed by the ECU. [Figure 5]Figure 5 is an example of a map that defines the correlation between rotational speed ratio and distribution ratio. [Modes for carrying out the invention]

[0009] [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 water pump (hereinafter referred to as HWP) 22, a heating element 24, a thermostat 30, a four-way valve 40, and a heat exchanger 50.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] 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).

[0014] 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 status of the engine 10, heating requests, and battery cooling requests. The ECU100 functionally implements an acquisition unit, a calculation unit, and a control unit, as will be described in more detail later.

[0015] 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 element 24 located in between. Route 63 has its upstream end connected between the heating element 24 and thermostat 30 of route 62 and its downstream end connected to a 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 element 24 and thermostat 30 of route 62. A temperature sensor 18 is provided at the point where routes 61 and 64 are connected. Route 65 has its upstream end connected to the 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 temperature sensor 18 of route 61 and its downstream end connected to the thermostat 30, with a radiator 14 and a reserve tank 16 located in between.

[0016] [4-way valve] Next, the four-way valve 40 will be described. Figures 2A to 2F are explanatory diagrams of the communication state of the four-way valve 40. By rotating the rotor of the four-way valve 40 in one direction, the communication state is switched in the order of Figures 2A to 2F. In Figure 2A, paths 63 and 62 are in communication, and paths 61 and 65 are blocked. In this state, the EWP 12 is stopped and the HWP 22 is driven. Cooling water circulates through the heater core 20 and the heating heater 24 via part of path 62 and path 63. The opening ratio of the opening of the four-way valve 40 connecting paths 63 and 62 is at its maximum. In Figure 2A, the rotor of the four-way valve 40 is in its initial position. As the rotor rotates in one direction from its initial position, the opening ratio of the opening connecting paths 63 and 62 decreases, and the opening ratio of the opening connecting path 63 and path 65 increases, as shown in Figure 2B.

[0017] In Fig. 2B, path 63 communicates with paths 62 and 65, and path 61 is blocked. In this state, EWP12 stops and HWP22 is driven. The cooling water circulates through part of path 62, path 63, the heater core 20, and the heating heater 24, and circulates through the heat exchanger 50 via path 65. As the rotor rotates in one direction from Fig. 2B, as shown in Fig. 2C, the opening ratio of the opening that connects path 63 and path 62 decreases to zero, and the opening ratio of the opening that connects path 63 and path 65 increases to the maximum.

[0018] In Fig. 2C, path 63 communicates with path 65, and paths 61 and 62 are blocked. In this state, EWP12 stops and HWP22 is driven. The cooling water circulates through part of path 62, path 63, path 65, the heat exchanger 50, and the heating heater 24. The opening ratio of the opening that connects path 63 and path 65 of the four-way valve 40 is the maximum. As the rotor rotates in one direction from Fig. 2C, as shown in Fig. 2D, the opening ratio of the opening that connects path 63 and path 65 decreases, and the opening ratio of the opening that connects path 61 and path 62 increases.

[0019] In Fig. 2D, path 63 communicates with path 65, and path 61 communicates with path 62. Note that paths 63 and 65 do not communicate with paths 61 and 62. In this state, EWP12 and HWP22 are driven. The cooling water circulates through part of path 62, path 63, path 65, the heat exchanger 50, and the heating heater 24, and circulates through the engine 10, the heater core 20, and the heating heater 24 via paths 61 and 62. Therefore, paths 61 and 62 correspond to the path through which the cooling water that has passed through the engine 10 passes through the engine 10 again without passing through the radiator 14. Note that when the thermostat 30 is fully open, the cooling water also circulates through the radiator 14 and the reserve tank 16 via path 66. As the rotor rotates in one direction from Fig. 2D, as shown in Fig. 2E, the opening ratio of the opening that connects path 63 and path 65 decreases to zero, and the opening ratio of the opening that connects path 61 and path 62 increases to the maximum.

[0020] In Figure 2E, path 61 and path 62 are in communication, and paths 63 and 65 are blocked. In this state, at least EWP12 is driving. The cooling water circulates through the engine 10, the heater core 20, and the heating heater 24 via paths 61 and 62. The opening ratio of the opening that connects path 61 and path 62 of the four-way valve 40 is the maximum. When the thermostat 30 is in the fully open state, the cooling water also circulates through the radiator 14 and the reserve tank 16 via path 66. As the rotor rotates in one direction from Figure 2E, as shown in Figure 2F, the opening ratio of the opening that connects path 61 and path 62 decreases, and the opening ratio of the opening that connects path 61 and path 65 increases.

[0021] In Figure 2F, path 61 is in communication with paths 62 and 65, and path 63 is blocked. The cooling water circulates through the engine 10, the heater core 20, the heating heater 24, and the heat exchanger 50 via paths 61, 62, and 65 by at least EWP12. Therefore, paths 61, 62, and 65 correspond to the path through which the cooling water that has passed through the engine 10 passes through the engine 10 again without passing through the radiator 14. When the thermostat 30 is in the fully open state, the cooling water also circulates through the radiator 14 and the reserve tank 16 via path 66.

[0022] The total value of the opening ratio of the opening that connects path 61 and path 62 and the opening ratio of the opening that connects path 61 and path 65 in Figure 2F is lower than the maximum value of the opening ratio of the opening that connects path 61 and path 62 in Figure 2E. For example, assume the opening ratio of the opening that connects path 61 and path 62 in Figure 2E is 100%. The opening ratio of the opening that connects path 61 and path 62 in Figure 2F is 40%, and the opening ratio of the opening that connects path 61 and path 65 is 40%. Therefore, the opening ratio of path 61 in Figure 2F is 80% in total, which is lower than the opening ratio of 100% in Figure 2E.

[0023] 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, resulting in 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 these paths by referring to a map defined according to the target rotation position of the rotor.

[0024] [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.

[0025] 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.

[0026] [EWP rotation speed control] Figure 4 is a flowchart illustrating the rotational speed control of the EWP12 performed by the ECU100. As described above, the EWP12 is stopped in the states shown in Figures 2A to 2C, and is driven in the states shown in Figures 2D to 2F. In the states shown in Figures 2D and 2E, the target engine flow rate is calculated based on the target heater core flow rate, and the rotational speed of the EWP12 is controlled based on the target engine flow rate. In the state shown in Figure 2F, the rotational speed of the EWP12 is controlled based on the target flow rate of the cooling water flowing through the heat exchanger 50. Figure 4 illustrates the case where the rotational speed of the EWP12 is controlled based on the target heater core flow rate.

[0027] The ECU100 acquires the heater core target flow rate and the rotational speeds of EWP12 and HWP22 (step S1). The heater core target flow rate is calculated according to the heating request. Here, the rotational speeds of EWP12 and HWP22 may be command values ​​for EWP12 and HWP22, or values ​​detected by sensors may be used. Step S1 is an example of the processing performed by the acquisition unit.

[0028] Next, the ECU 100 refers to the map in Figure 5, which predefines the correlation between the rotational speed ratio and the distribution ratio, and calculates the distribution ratio based on the rotational speeds of EWP12 and HWP22 obtained in step S1 (step S2). The rotational speed ratio is the ratio of the rotational speed of HWP22 to the rotational speed of EWP12. The distribution ratio is the ratio of the flow rate of coolant passing through HWP22 to the flow rate of coolant passing through EWP12. Speed ​​ratio = (HWP22 speed) / (EWP12 speed) ... (1) Distribution ratio = (Flow rate of cooling water passing through HWP22) / (Flow rate of cooling water passing through EWP12) ... (2)

[0029] Figure 5 is an example of a map that defines the correlation between the rotational speed ratio and the distribution ratio. The distribution ratio increases as the rotational speed ratio increases. Figure 5 shows the cases where the thermostat 30 is fully closed and fully open with solid lines. The distribution ratio increases as the opening degree of the thermostat 30 decreases. The solid line in Figure 5 shows the case where the opening ratio of the opening connecting path 61 and path 62 is 100%. As the opening ratio of the opening connecting path 61 and path 62 decreases, the distribution ratio decreases as shown by the dotted line in Figure 5. The correlation in the map in Figure 5 is defined based on experimental results that confirmed how the actual distribution ratio changes in accordance with the rotational speed ratio in the engine cooling circuit 2. Step S2 is an example of a process executed by the calculation unit.

[0030] Next, the ECU100 calculates the target engine flow rate (step S3) based on the distribution ratio calculated in step S2 and the target heater core flow rate obtained in step S1. Specifically, the target engine flow rate is calculated using the following formula. Engine target flow rate = (Heater core target flow rate) / (Calculated distribution ratio) ... (3)

[0031] Next, the ECU 100 calculates the target rotational speed of the EWP 12 based on the calculated target engine flow rate and controls the rotational speed of the EWP 12 to match the target rotational speed (step S4). By repeating steps S1 to S4 as described above, the rotational speed of the EWP 12 is controlled while controlling the flow rate of the coolant passing through the HWP 22 to the target flow rate of the heater core. Steps S3 and S4 are examples of processes performed by the control unit.

[0032] As described above, the engine target flow rate is calculated based on the heater core target flow rate and the rotational speeds of HWP22 and EWP22 by referring to a map that pre-defines the correlation between the rotational speed ratio and the distribution ratio based on experimental results. Therefore, an engine target flow rate is calculated that allows the flow rate of the coolant passing through HWP22 to be controlled to the heater core target flow rate. This makes it possible to appropriately control the flow rate of the coolant passing through HWP22 to the heater core target flow rate. As a result, the heater core target flow rate can be calculated and achieved according to the heating requirements.

[0033] Furthermore, if EWP12 is stopped, its rotational speed is zero, and therefore the engine target flow rate is calculated as zero based on equation (1), the map in Figure 5, and equation (3). Consequently, when EWP12 is stopped, the engine target flow rate may be calculated as follows. For example, if the rotational speed of EWP12 is zero, the rotational speed ratio is calculated using a predetermined upper limit. This results in the engine target flow rate being calculated as a small value other than zero, and the rotational speed of EWP12 is controlled accordingly. Alternatively, the rotational speed ratio may be calculated by substituting a predetermined expected rotational speed of EWP12 (other than zero) based on the heater core target flow rate into the rotational speed of EWP12 in equation (1). Alternatively, the engine target flow rate may be calculated by substituting a predetermined fixed value into the rotational speed of EWP12 in equation (1), and the engine target flow rate may be repeatedly calculated by substituting the target rotational speed of EWP12 corresponding to the engine target flow rate into the rotational speed of EWP12 in equation (1).

[0034] In the above embodiment, a map defining the correlation between the rotation speed ratio and the distribution ratio was referred to, but a calculation formula defining this correlation may also be referred to. The calculation formula may take the opening degree of the thermostat 30 and the opening ratio of the path 61 by the four-way valve 40 as arguments. Figure 4 illustrates a case where the rotation speed of the EWP 12 is controlled based on the target flow rate of the heater core. When the rotation speed of the EWP 12 is controlled based on the target flow rate to the heat exchanger 50, the target flow rate of the cooling water passing through the heat exchanger 50 is used instead of the target flow rate of the heater core.

[0035] 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]

[0036] 1. Engine Cooling System 2. Engine cooling circuit 10 Engines 12. Engine water pump 14 Radiator 20 Heater Cores 22 Heater water pump 100 ECU (Control Unit, Acquisition Unit, Calculation Unit, Control Unit)

Claims

[Claim 1] A cooling circuit having a circulation path through which coolant circulates between the engine and the heater core, via an engine water pump that circulates coolant to the engine and a heater water pump that circulates coolant to the heater core for heating, The system includes a control device for controlling the engine water pump, An acquisition unit that acquires the target flow rate of the cooling water passing through the heater core water pump, which is the target flow rate of the heater core, and the rotational speed of the heater water pump. A calculation unit calculates the distribution ratio based on the acquired rotation speed of the heater water pump, by referring to the correlation between the rotation speed ratio, which is the ratio of the rotation speed of the heater water pump to the rotation speed of the engine water pump, and the distribution ratio, which is the ratio of the flow rate of the coolant passing through the heater water pump to the flow rate of the coolant passing through the engine water pump. An engine cooling system comprising: a control unit that calculates an engine target flow rate, which is a target flow rate of cooling water flowing to the engine water pump, based on the calculated distribution ratio and the heater core target flow rate, and controls the rotational speed of the engine water pump according to the engine target flow rate.

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