JP2016200032A - Cooling device of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further surely open a selector valve which should be opened.SOLUTION: When a first selector valve is opened, a lower limit guard value Dmin is set large as the fore-and-aft valve differential pressure of the first selector valve is small on the basis of a valve-opening state of a thermostat and a valve-opening state of a second selector valve by bringing a coli into a non-energized state (steps S100 to S160), a larger one out of a required drive duty ratio Dr and the lower limit value Dmin is set as a target drive duty ratio D*, and an electric W/P is controlled by using a drive signal of the target drive duty ratio D* (step S170). By this constitution, a valve body of the first selector valve is further surely separated from a valve seat, and the first selector valve can be further surely opened.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an engine cooling device, and more specifically, a first flow path for circulating a cooling medium between an engine and a radiator, and a branching of the cooling medium flowing through the first flow path to bypass the engine and the radiator. A second flow path that merges with the first flow path, a third flow path that causes the cooling medium that has flowed through the engine to flow through the second flow path without flowing through the radiator, and a switching valve that is attached to the third flow path. And an electric water pump attached to a first flow path for pumping a cooling medium.

  Conventionally, as this type of engine cooling device, a device including a first flow path, a second flow path, a third flow path, an electric pump, and a first valve has been proposed. (For example, refer to Patent Document 1). The first flow path constitutes a circulation flow path for circulating the refrigerant between the engine and the radiator. The second flow path divides the refrigerant upstream from the engine of the first flow path, distributes the divided refrigerant to the heater, and then merges it with the first flow path. The third flow path causes the refrigerant from the engine to flow upstream of the heater of the second flow path, bypassing the radiator. The electric pump discharges the refrigerant to the first flow path. The first valve is attached to the third flow path. The first valve includes a valve seat, a valve body, an urging member, and a solenoid. The first valve is closed when the solenoid is energized and the valve element comes into contact with the valve seat by the magnetic force and the urging force of the urging member, the solenoid is de-energized, and the pressure received by the valve element by the refrigerant is applied. When the urging force of the urging member is exceeded, the valve element is opened by separating from the valve seat. In this engine cooling device, when the first valve is opened, the refrigerant flow amount by the electric pump is increased to a predetermined amount with respect to the first valve being closed, and the first valve is increased. After opening the valve, the refrigerant flow rate is reduced. By reducing the flow rate of the refrigerant after opening the first valve, the refrigerant is prevented from excessively flowing into the engine and the internal temperature of the engine being excessively lowered.

JP 2013-108398 A

  In the engine cooling device described above, there are cases where the first valve cannot be opened even if the amount of refrigerant flowing from the electric pump is increased to a predetermined amount. In the engine cooling device, the pressure loss of the refrigerant changes depending on the open / closed state of other valves attached to a position different from the third flow path, the temperature of the refrigerant, and the like. For this reason, if the flow rate of the refrigerant from the electric pump is a uniform value regardless of the pressure loss of the refrigerant, the pressure of the refrigerant acting on the valve body cannot exceed the urging force of the urging member. The valve may not be opened.

  The engine cooling device of the present invention is mainly intended to open the switching valve more reliably when the switching valve needs to be opened.

  The engine cooling device of the present invention employs the following means in order to achieve the above-mentioned main object.

The engine cooling device of the present invention comprises:
A first flow path for circulating a cooling medium through the engine and the radiator in this order;
A second flow path that diverts the cooling medium flowing through the first flow path and bypasses the engine and the radiator to join the first flow path;
A third flow path that causes the cooling medium that has flowed through the engine to flow through the second flow path by bypassing the radiator;
A switching valve attached to the third flow path;
An electric water pump attached to the first flow path and pumping the cooling medium;
Control means for controlling the electric water pump with a drive signal having a required drive duty ratio based on at least the temperature of the cooling medium;
An engine cooling device comprising:
The switching valve shuts off the third flow path when a part of the valve seat and the surface on the first flow path side abuts on the valve seat, and a part of the surface on the first flow path side is the valve. A valve body that circulates through the third flow path by separating from the seat, a biasing member that biases the valve body toward the valve seat, and a coil that drives the valve body,
When the opening of the switching valve is requested, the control means deenergizes the coil, and the electric water pump is driven by a drive signal having a larger duty ratio between the required drive duty ratio and a lower limit duty ratio. Control
Furthermore, the control means increases the lower limit duty ratio as the pressure loss of the cooling medium increases.
This is the gist.

  In the engine cooling device according to the present invention, when the switching valve is requested to open, the coil is de-energized and the electric water is driven with a drive signal having a larger duty ratio between the required drive duty ratio and the lower limit duty ratio. Control the pump. The lower limit duty ratio is increased as the pressure loss of the refrigerant increases. Thereby, the lower limit value of the output of the electric water pump can be increased as the pressure loss of the refrigerant is larger, and the valve differential pressure can be set to a predetermined value or more. Therefore, the valve body can be more reliably separated from the valve seat, and the switching valve to be opened can be opened more reliably.

  In the engine cooling apparatus of the present invention, the lower limit duty ratio may be a value that is predetermined as a duty ratio at which the valve differential pressure is equal to or higher than a valve opening pressure at which the switching valve can be opened. In this way, the switching valve can be opened more reliably.

  The engine cooling device of the present invention further includes a second switching valve attached to the first flow path, and the control means increases the lower limit duty ratio as the opening of the second switching valve increases. It is good also as a thing. When the output of the electric water pump is constant, the refrigerant pressure loss increases as the opening of the second switching valve increases. Therefore, the lower limit duty ratio is increased as the opening degree of the second switching valve is increased, so that the lower limit value of the electric water pump can be increased as the opening degree of the second switching valve is increased. It can be set to a predetermined value or more. As a result, the valve body can be more reliably separated from the valve seat, and the switching valve to be opened can be opened more reliably.

  Furthermore, in the engine cooling device of the present invention, a fourth flow path branched from the second flow path and joined to the second flow path, and a third switching valve attached to the fourth flow path, The control means may increase the lower limit duty ratio as the opening of the third switching valve decreases. When the output of the electric water pump is constant, the refrigerant pressure loss increases as the opening of the third switching valve decreases. Therefore, the lower limit duty ratio is increased as the opening degree of the third switching valve is reduced, so that the lower limit value of the output of the electric water pump can be increased as the opening degree of the third switching valve is reduced. It can be set to a predetermined value or more. As a result, the valve body can be more reliably separated from the valve seat, and the switching valve to be opened can be reliably opened.

  In the engine cooling apparatus of the present invention, the lower limit duty ratio may be increased as the temperature of the cooling medium decreases. When the driving duty ratio of the electric water pump is constant, the viscosity of the cooling medium increases as the temperature of the cooling medium decreases, so that the pressure loss of the cooling medium increases. For this reason, the lower limit duty ratio is increased as the temperature of the cooling medium decreases, so that the lower limit value of the electric water pump output can be increased as the temperature of the cooling medium decreases, and the valve differential pressure is set to a predetermined value or more. Can do. The valve body can be reliably separated from the valve seat, and the switching valve to be opened can be reliably opened.

It is a block diagram which shows the outline of a structure of the cooling device 20 as one Example of this invention. It is explanatory drawing which shows a mode when the switching valve 30 is closing. It is explanatory drawing which shows a mode when the switching valve 30 is opening. 3 is a flowchart showing an example of an electric W / P control routine executed by an electronic control unit 50. An example of the time change of the target drive duty ratio D *, the front-rear valve differential pressure of the switching valve 30, and the lift amount of the switching valve 40 (amount of movement of the valve body 34 from the valve seat 32) in the cooling device 20 of the embodiment is shown. It is explanatory drawing. It is a flowchart which shows an example of the electrically-driven W / P control routine of a modification. It is explanatory drawing which shows an example of the relationship between the cooling water temperature Tw and the corrected lower limit guard value Dmin.

  Next, the form for implementing this invention is demonstrated using an Example.

  FIG. 1 is a configuration diagram showing an outline of a configuration of a cooling device 20 that cools an engine 10 as an embodiment of the present invention. The cooling device 20 is mounted on an automobile together with the engine 10 and the air conditioner 12, and as shown in the figure, a circulation flow path 22, bypass flow paths 24 and 25, a communication flow path 26, a radiator 27, an electric water pump ( W / P) 28, switching valves 30 and 40, a thermostat 42, and an electronic control unit 50.

  The circulation flow path 22 is configured as a flow path for circulating cooling water in the order of the electric W / P 28, the engine 10, the radiator 27, the thermostat 42, and the electric W / P 28.

  The bypass flow path 24 is branched from the circulation flow path 22 between the electric W / P 28 and the engine 10, and after the cooling water branched from the circulation flow path 22 is circulated to the heater core 14 of the air conditioner 12, It is made to merge with the circulation flow path 22 between electric W / P28. The bypass passage 24 is designed so that the pressure loss is larger than that of the circulation passage 22. Therefore, when the cooling water flows through the communication channel 26, it flows from the circulation channel 22 to the bypass channel 24.

  The bypass channel 25 branches from the bypass channel 24 upstream of the heater core 14 and merges with the bypass channel 24 downstream of the heater core 14.

  The communication flow path 26 branches from the circulation flow path 22 between the engine 10 and the radiator 27, and joins the bypass flow path 24 upstream from the heater core 14.

  The electric water pump (W / P) 28 is attached between the thermostat 42 of the circulation flow path 22 and the engine 10, and pumps cooling water to the circulation flow path 22. The electric water pump (W / P) 28 is controlled by the electronic control unit 50.

  The switching valve 30 is made of a magnetic material and is attached to the communication channel 26. FIG. 2 is an explanatory view showing a state when the switching valve 30 is closed, and FIG. 3 is an explanatory view showing a state when the switching valve 30 is opened. The switching valve 30 includes a valve seat 32, a valve body 34, an urging member 36, and a coil 38. The valve seat 32 is formed in a housing 31 that houses the valve body 34. The valve body 34 blocks the communication flow path 26 when a part of the surface on the bypass flow path 24 side abuts on the valve seat 32, and circulates the communication flow path 26 by separating from the valve seat 32. The urging member 36 urges the valve body 34 toward the valve seat 32. The coil 38 drives the valve element 34 by energization. When the coil 38 is energized so as to generate a magnetic field in the direction of attracting the valve body 34 (pressing the valve body 34 against the valve seat 32), the switching valve 30 generates the generated magnetic force and bias as shown in FIG. The valve element 34 is closed by contacting the valve seat 32 with the urging force of the member 36. When the coil 38 is de-energized, the switching valve 30 has a valve differential pressure Dp obtained by subtracting the pressure of the cooling water acting on the bypass flow path 24 from the pressure of the cooling water acting on the circulation flow path 22 side of the valve element 34. When the pressure is greater than the pressure applied by the urging member 36, the valve element 34 opens away from the valve seat 32 as shown in FIG. The coil 38 is energized by the electronic control unit 50.

  The switching valve 40 is attached to the bypass flow path 25. The switching valve 40 is controlled by the electronic control unit 50.

  The thermostat 42 always allows the cooling water to flow from the bypass flow path 24 to the downstream side (electric W / P 28 side) of the circulation flow path 22 from the bypass flow path 24, and has passed through the radiator 27 of the circulation flow path 22. The cooling water is allowed or prohibited from flowing downstream from the thermostat 42. Specifically, the thermostat 42 opens when the temperature of the cooling water flowing from the bypass flow path 24 to the thermostat 42 is equal to or higher than a predetermined water temperature T1, and the cooling water that has passed through the radiator 27 of the circulation flow path 22 is transferred to the thermostat 42. It is allowed to flow downstream from 42. Further, the thermostat 42 is closed when the temperature of the cooling water flowing from the bypass flow path 24 to the thermostat 42 is lower than the predetermined water temperature T1, and the cooling water that has passed through the radiator 27 of the circulation flow path 22 is more than that of the thermostat 42. Restrict distribution to the downstream side. Here, the predetermined water temperature T1 is set to the temperature of the cooling water flowing from the bypass passage 24 to the thermostat 42 when the engine 10 is warmed up, for example, 80 ° C., 82 ° C., 84 ° C., or the like.

  The electronic control unit 50 is configured as a microprocessor centered on a CPU (not shown). In addition to the CPU, none is shown, but a ROM for storing a processing program and a RAM for temporarily storing data. , With input / output ports. Various signals are input to the electronic control unit 50 from sensors necessary for controlling the electric W / P 28 and the switching valves 30 and 40. Examples of various signals include the following. A cooling water temperature Tw from a water temperature sensor 60 that is attached near the outlet of the engine 10 in the circulation channel 22 and detects the temperature of the cooling water. A heating request signal from the air conditioner 12. Various control signals for controlling the electric W / P 28 and the switching valves 30 and 40 are output from the electronic control unit 50. Examples of the various control signals include the following. Drive signal to electric W / P28. An energization signal for energizing the coil 38 of the switching valve 30. A control signal for turning on and off the switching valve 40.

  In the cooling device 20 of the embodiment thus configured, the thermostat 42 is opened and closed according to the temperature of the cooling water flowing to the thermostat 42 while the cooling water is pumped to the circulation flow path 22 by the electric W / P 28. When the thermostat 42 is closed, the engine 10 is warmed up by restricting the flow of the cooling water to the radiator 27. Further, when the thermostat 42 is open, the cooling water is circulated to the radiator 27 and the cooling water heated by the engine 10 is radiated by the radiator 27 while the cooling water is circulated through the circulation passage 22 so that the engine 10 can be circulated. Cooling.

  When the thermostat 42 is closed, the switching valve 30 is further opened and closed according to the cooling water temperature Tw from the water temperature sensor 60. When the thermostat 42 is closed, that is, when the cooling water temperature flowing to the thermostat 42 is the predetermined water temperature T1, the predetermined water temperature T2 (for example, 70 ° C., 72 ° C., 74, etc.) where the cooling water temperature Tw is lower than the predetermined water temperature T1. When the temperature is less than (° C.), the energization signal of the coil 38 of the switching valve 30 is turned on to energize the coil 38 and close the switching valve 30. Thus, by closing the switching valve 30 when the thermostat 42 is closed, the cooling water bypasses the engine 10 and the radiator 27, passes through the bypass flow path 24, and the electric W / P 28 and the heater core 14. , Circulate in the order of electric W / P28. At this time, since the cooling water stays inside the engine 10, the temperature of the cooling water inside the engine 10 can be increased by warming up the engine 10. Thereby, warm-up of the engine 10 can be promoted.

  When the engine 10 is warmed up with the switching valve 30 closed and the cooling water temperature Tw becomes equal to or higher than the predetermined water temperature T2, the energization signal is turned off and the coil 38 is de-energized to open the switching valve 30. . When the thermostat 42 is closed, the coolant circulates in the order of the engine 10, the heater core 14, and the electric W / P 28 through the communication flow path 26, bypassing the radiator 27. Since the cooling water circulates bypassing the radiator 27, the engine 10 is kept warm.

  Further, when the engine 10 is kept warming up, the temperature of the cooling water further increases. And if the temperature of the cooling water which distribute | circulates to the thermostat 42 becomes more than predetermined water temperature T1, the thermostat 42 will open. When the thermostat 42 is opened, the cooling water passes through the circulation passage 22, the bypass passage 24, and the communication passage 26, and circulates through the engine 10, the radiator 27, the thermostat 42, the electric W / P 28, the switching valve 40, and the heater core 14. . Accordingly, the engine 10 is cooled by circulating the cooling water while dissipating the warmed cooling water by the radiator 27.

  The electronic control unit 50 closes the switching valve 40 when the required blowing temperature of the air conditioner 12 is equal to or higher than a predetermined value, and opens the switching valve 40 when the necessary blowing temperature is lower than the predetermined value. Thereby, the air conditioning apparatus 12 can be operated appropriately by adjusting the amount of cooling water flowing through the heater core 14.

  Further, the electronic control unit 50 controls the electric W / P 28 so that the cooling water is discharged at a target flow rate corresponding to the cooling water temperature Tw. More specifically, the target discharge amount of the electric W / P 28 is set so as to increase as the cooling water temperature Tw increases, and the drive signal for causing the electric W / P 28 to rotate at the target pump speed corresponding to the target discharge amount. The required drive duty ratio Dr is set (time when the drive signal rises with respect to the cycle of the drive signal). Then, the set required drive duty ratio Dr is set as the target drive duty ratio D *, and the electric W / P 28 is driven using the drive signal of the target drive duty ratio D *.

  Next, the operation of the cooling device 20 of the embodiment configured as described above, particularly the operation when controlling the driving of the electric W / P 28 when the switching valve 30 is opened will be described. FIG. 4 is a flowchart showing an example of the electric W / P control routine executed by the electronic control unit 50. This routine is executed when the energization signal for energizing the coil 38 of the switching valve 30 is switched from on to off, that is, when the switching valve 30 is opened.

  When this routine is executed, the electronic control unit 50 checks the opening / closing state of the thermostat 42 (step S100), and executes a process of checking the opening / closing state of the switching valve 40 (steps S110, S120).

  When the thermostat 42 is closed and the switching valve 40 is open (steps S100 and S110), a value D1 is set as the lower limit guard value Dmin (step S130). When the thermostat 42 is closed and the switching valve 40 is closed (steps S100 and S110), a value D2 is set as the lower limit guard value Dmin (step S140). Further, when the thermostat 42 is opened and the switching valve 40 is opened (steps S100 and S120), a value D3 is set as the lower limit guard value Dmin (step S150). When the thermostat 42 is open and the switching valve 40 is closed (steps S100 and S120), a value D4 is set as the lower limit guard value Dmin (step S160). When the lower limit guard value Dmin is set in this way, the larger one of the required drive duty ratio Dr and the lower limit guard value Dmin is set as the target drive duty ratio D *, and the electric power W / P28 is controlled (step S170). With this control, the electric W / P 28 can be controlled with a drive signal having a target drive duty ratio D * within a range equal to or higher than the lower limit guard value Dmin.

  The value D1 is a drive signal for the electric W / P 28 that uses the valve differential pressure Dp as the valve differential pressure that reliably opens the switching valve 30 when the thermostat 42 is closed and the switching valve 40 is opened. In the embodiment, for example, the value is 50% of the maximum drive duty ratio Dmax of the drive signal when the electric W / P 28 is driven at the rated maximum output. Further, the value D2 is the value of the electric W / P 28 that uses the valve differential pressure Dp as the valve differential pressure at which the switching valve 30 opens reliably when the thermostat 42 is closed and the switching valve 40 is closed. The value is greater than the drive duty ratio of the drive signal, for example, a value greater than the value D1, such as 55% of the maximum drive duty ratio Dmax. Further, the value D3 is the value of the electric W / P 28 that uses the valve differential pressure Dp as the valve differential pressure for surely opening the switching valve 30 when the thermostat 42 is opened and the switching valve 40 is opened. The value is larger than the drive duty ratio of the drive signal, for example, a value larger than the value D2, such as a value of 60% of the maximum drive duty ratio Dmax. Then, the value D4 is the value of the electric W / P 28 that uses the valve differential pressure Dp as the valve differential pressure at which the switching valve 30 opens reliably when the thermostat 42 is open and the switching valve 40 is closed. The value is larger than the drive duty ratio of the drive signal, for example, a value larger than the value D3 such as 65% of the maximum drive duty ratio Dmax. Next, the reason why the values D1 to D4 are set as described above and the reason why the larger one of the required drive duty ratio Dr and the lower limit guard value Dmin is set as the target drive duty ratio D * will be described.

  First, the reason why the larger one of the required drive duty ratio Dr and the lower limit guard value Dmin is set as the target drive duty ratio D * will be described. FIG. 5 shows the change over time in the target drive duty ratio D *, the valve differential pressure Dp of the switching valve 30, and the lift amount of the switching valve 40 (the amount of movement of the valve body 34 from the valve seat 32) in the cooling device 20 of the embodiment. It is explanatory drawing which shows an example. In the figure, the broken line shows an example of a temporal change in the target duty ratio D *, the valve differential pressure, and the lift amount of the switching valve 40 in the comparative example. In the comparative example, the required drive duty ratio Dr is set to the target drive duty ratio D * as it is without using the lower limit guard value Dmin. In the comparative example, the required duty ratio Dr is set to the target drive duty ratio D * as it is. Therefore, when the required duty ratio Dr is small, the valve differential pressure Dp of the switching valve 30 can open the switching valve 30. The switch valve 30 cannot be opened without reaching Dopen. If the switching valve 30 cannot be opened, when the thermostat 42 is closed, the cooling water warmed by the engine 10 stays and the cooling water temperature rises more than necessary. Further, if the switching valve 30 cannot be opened, the cooling water warmed by the engine 10 does not flow to the heater core 14, so that the heating performance of the air conditioner 12 is deteriorated. In the embodiment, since the larger one of the required drive duty ratio Dr and the lower limit guard value Dmin is set as the target drive duty ratio D *, the electric drive is performed with the drive signal of the target drive duty ratio D * equal to or higher than the lower limit guard value Dmin. Drive W / P28. Thereby, it can suppress that the valve differential pressure | voltage Dp of the switching valve 30 becomes lower than the valve opening pressure Dopen of a switching valve. Thereby, the switching valve 30 can be opened reliably.

  Next, the reason why the above-described values D1 to D4 are set as the lower limit guard value Dmin will be described. Consider a case where the flow rate of cooling water from the electric W / P 28 is constant. In the embodiment, when the drive duty from the electric W / P 28 is constant, the valve differential pressure Dp when the switching valve 30 is closed is: (1) the thermostat 42 is closed and the switching valve 40 is When the valve is open (2) When the thermostat 42 is closed and the switching valve 40 is closed, (3) When the thermostat 42 is opened and the switching valve 40 is opened (4) When the thermostat 42 is opened and the switching valve 40 is closed, the order becomes smaller. This is because when the switching valve 30 is closed, the pressure loss of the cooling water becomes larger when the thermostat 42 is opened than when the thermostat 42 is closed, and the switching valve 40 is opened. This is based on the fact that the pressure loss of the cooling water is larger when the switching valve 40 is closed than when the valve is closed, and that the opening and closing of the thermostat 42 has a greater effect on the pressure loss than the opening and closing of the switching valve 40. . As the cooling loss of the cooling water increases, a higher output of the electric W / P 28 is required to set the valve differential pressure Dp to the valve opening pressure Dopen. Therefore, the values set to the lower limit guard value Dmin are set to the values D1 and D2. , Value D3, value D4 are increased in this order, that is, the lower limit value of the output of the electric W / P 28 is increased as the cooling loss of cooling water increases, so that the switching valve 30 can be opened more reliably. Further, since the lower limit guard value Dmin is changed in accordance with the opening / closing state of the thermostat 42 and the opening / closing state of the switching valve 40, the target drive duty ratio D regardless of the opening / closing state of the thermostat 42 or the opening / closing state of the switching valve 40. The power consumption can be reduced as compared with a case where the target drive duty ratio D * is uniformly increased, such as a case where * is the maximum value of the drive duty ratio.

  When the electric W / P 28 is controlled in this way, the elapsed time t from when the energization signal for energizing the coil 38 is switched from on to off is compared with the predetermined time tref (step S180). The predetermined time tref is a threshold value for determining whether or not the target drive duty ratio D * of the electric W / P 28 is set using a lower limit guard value Dmin described later, and is set to 2 sec, 3 sec, 4 sec, etc., for example. It was supposed to be.

  When the elapsed time t does not exceed the predetermined time tref (step S180), the process returns to step S100, and the processes of steps S100 to S180 are repeated. When the elapsed time t exceeds the predetermined time tref (step S180), this routine is terminated. Only when the elapsed time t exceeds the predetermined time tref, the larger one of the lower limit guard value Dmin and the required drive duty ratio D * is set as the target drive duty ratio D * and the electric W / P 28 is driven. Compared with the case where the lower limit guard value Dmin is set to the target drive duty ratio D * regardless of the elapsed time t and the electric W / P 28 is driven by the drive signal of the target drive duty ratio D *, the power consumption is reduced. be able to.

  After the end of this routine, as described above, the required drive duty ratio Dr is set to the target drive duty D *, and the electric W / P 28 is driven with the drive signal of the set target drive duty D *. At this time, as shown in FIG. 5, the drive duty ratio of the electric W / P 28 may be small. Once the switching valve 30 is opened, the area that receives the pressure of the cooling water on the circulation flow path 22 side of the valve element 34 becomes larger than before the valve is opened, so that the switching valve 30 remains open even when the cooling water pressure decreases. it can. Therefore, there is no problem even if the drive duty ratio of the electric W / P 28 is reduced.

  In the cooling device 20 of the embodiment described above, when the switching valve 30 is opened, the coil 38 is deenergized, and the larger of the required drive duty ratio Dr and the lower limit guard value Dmin is the target drive duty ratio D *. And the electric W / P 28 is controlled by a drive signal having a target drive duty ratio D *. And according to the open / close state of the switching valve 40 and the thermostat 42, the lower limit guard value Dmin is increased as the pressure loss of the cooling water increases. Thereby, the valve body 34 can be reliably separated from the valve seat 32, and the switching valve 30 can be opened reliably.

  In the cooling device 20 of the embodiment, the processes of steps S100 to S160 are executed. However, the processes of step S100, the process of step S130 or step S140, and the step are not performed without executing the processes of steps S110 and S120. The process of S150 or step S160 may be executed. In this case, when it is determined in step S100 that the thermostat 42 is open, the process of step S130 or step S140 is executed, and when it is determined in step S100 that the thermostat 42 is closed. The process of step S150 or step S160 may be executed.

  In the cooling device 20 of the embodiment, the processes of steps S100 to S160 are executed, but the processes of steps S110, S130, and S140 are executed without executing the processes of steps S100, S120, S150, and S160. Also good.

  In the cooling device 20 of the embodiment, the lower limit guard value Dmin is larger when the thermostat 42 is opened than when the thermostat 42 is closed, but the thermostat 42 is used as an adjustment valve whose opening degree can be changed. The lower limit guard value Dmin may be increased as the degree of opening increases. The lower limit guard value Dmin is larger when the switching valve 40 is closed than when the switching valve 40 is open. However, the switching valve 40 is an adjustment valve that can change the opening, and the opening of the adjustment valve is The lower limit guard value Dmin may be increased as the value decreases.

  In the cooling device 20 of the embodiment, the lower limit guard value Dmin is set according to the open / close state of the thermostat 42 and the switching valve 40 in the electric W / P control routine illustrated in FIG. 4, but according to the cooling water temperature Tw. Thus, the lower limit guard value Dmin may be set. Instead of the electric W / P control routine of FIG. 4, the lower limit guard value Dmin may be corrected based on the cooling water temperature Tw by executing the electric W / P control routine of the modified example of FIG. 6. The electric W / P control routine of the modified example is the electric motor shown in FIG. 4 except that the process of step S50 is executed before the process of step S100 and the process of step S165 is executed before the process of step 170. The process is the same as that of the W / P control routine. For this reason, the same processes as those in the electric W / P control routine are denoted by the same reference numerals, and the description thereof is omitted.

  In the electric W / P control routine of the modified example, first, a process of inputting the cooling water temperature Tw from the water temperature sensor 60 is executed (step S50). Subsequently, the processes of steps S100 to S160 are executed.

  And lower limit guard value Dmin is correct | amended using the cooling water temperature Tw input by the process of step S50 (step S165). Here, the correction of the lower limit guard value Dmin is performed by multiplying the lower limit guard value Dmin set in any of the processes of steps S130 to S160 by a coefficient f that increases as the cooling water temperature Tw decreases. FIG. 7 is an explanatory diagram showing an example of the relationship between the coolant temperature Tw and the corrected lower limit guard value Dmin. In the cooling device 20, the lower the cooling water temperature Tw, the higher the viscosity of the cooling water and the greater the pressure loss. Therefore, the lower limit guard Dmin of the correction g is increased as the cooling water temperature Tw is lower.

  When the lower limit guard value Dmin is corrected in this way, the process of step S180 is executed. If the elapsed time t does not exceed the predetermined time tref, the process returns to step S50. If the elapsed time t exceeds the predetermined time tref, this routine is executed. Exit. Thus, the switching valve 30 can be opened more reliably by increasing the lower limit guard value Dmin as the cooling water temperature Tw is lower.

  In the cooling device 20 of the embodiment, the bypass flow path 24 circulates the cooling water to the heater core 14 of the air conditioner 12. However, when the engine includes an EGR system, the bypass water 24 also circulates the cooling water to the EGR cooler. It is good.

  The correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problems will be described. In the embodiment, the circulation channel 22 corresponds to the “first channel”, the bypass channel 24 corresponds to the “second channel”, the communication channel 26 corresponds to the “third channel”, and the switching is performed. The valve 30 corresponds to a “switching valve”, the electric W / P 28 corresponds to an “electric water pump”, the electronic control unit 50 corresponds to a “control means”, the valve seat 32 corresponds to a “valve seat”, The valve body 34 corresponds to a “valve body”, the biasing member 36 corresponds to a “biasing member”, and the coil 38 corresponds to a “coil”.

  The correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problem is the same as that of the embodiment described in the column of means for solving the problem. Therefore, the elements of the invention described in the column of means for solving the problems are not limited. That is, the interpretation of the invention described in the column of means for solving the problems should be made based on the description of the column, and the examples are those of the invention described in the column of means for solving the problems. It is only a specific example.

  As mentioned above, although the form for implementing this invention was demonstrated using the Example, this invention is not limited at all to such an Example, In the range which does not deviate from the summary of this invention, it is with various forms. Of course, it can be implemented.

  The present invention can be used in the manufacturing industry of engine cooling devices.

  DESCRIPTION OF SYMBOLS 10 Engine, 12 Air conditioner, 14 Heater core, 20 Cooling device, 22 Circulation flow path, 24, 25 Bypass flow path, 26 Communication flow path, 27 Radiator, 28 Electric W / P, 30 Switching valve, 31 Housing, 32 Valve seat 34 Valve body 36 Energizing member 38 Coil 40 Switching valve 42 Thermostat 50 Electronic control unit 60 Water temperature sensor.

Claims (1)

A first flow path for circulating a cooling medium through the engine and the radiator in this order;
A second flow path that diverts the cooling medium flowing through the first flow path and bypasses the engine and the radiator to join the first flow path;
A third flow path that causes the cooling medium that has flowed through the engine to flow through the second flow path by bypassing the radiator;
A switching valve attached to the third flow path;
An electric water pump attached to the first flow path and pumping the cooling medium;
Control means for controlling the electric water pump with a drive signal having a required drive duty ratio based on at least the temperature of the cooling medium;
An engine cooling device comprising:
The switching valve shuts off the third flow path when a part of the valve seat and the surface on the first flow path side abuts on the valve seat, and a part of the surface on the first flow path side is the valve. A valve body that circulates through the third flow path by separating from the seat, a biasing member that biases the valve body toward the valve seat, and a coil that drives the valve body,
When the opening of the switching valve is requested, the control means deenergizes the coil, and the electric water pump is driven by a drive signal having a larger duty ratio between the required drive duty ratio and a lower limit duty ratio. Control
Furthermore, the control means increases the lower limit duty ratio as the pressure loss of the cooling medium increases.
Engine cooling system.

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