JP5579679B2 - Engine control device - Google Patents

Description

  The present invention relates to a technique for cooling an engine.

  As a technique for cooling the engine, as described in Japanese Patent Application Laid-Open No. 2004-353602 (Patent Document 1), a technique for controlling the opening degree of a passage bypassing the radiator by an electronically controlled thermostat has been proposed. . In such a technique, in order to improve the fuel consumption of the engine, control is performed to maintain the cooling water temperature at a high level (for example, 105 ° C.) during the constant road travel (Road Load).

JP 2004-353602 A

  However, the electronically controlled thermostat is effective in controlling the coolant temperature in steady-state driving, but the responsiveness is not good, so when shifting from a high water temperature state that emphasizes fuel efficiency to a low water temperature state that emphasizes output. There is a possibility that the target temperature cannot be tracked (during a transition), and output demands such as acceleration performance cannot be met.

  Therefore, in view of the problems of the prior art, the present invention controls the electronic control thermostat and the radiator fan in conjunction with each other, thereby cooling at the time of transition from a high water temperature state that emphasizes fuel consumption to a low water temperature state that emphasizes output. An object of the present invention is to provide an engine control device with improved water temperature response.

For this reason, an electronically controlled thermostat that changes the flow distribution to the radiator and an electric fan that blows air to the radiator are disposed in the engine cooling system. And when the target temperature of the cooling water in an engine cooling system exceeds a predetermined value, while controlling a thermostat to the close side, the air volume of an electric fan is controlled so that the temperature of the cooling water in a radiator falls.

  By controlling the electronically controlled thermostat and the electric fan in cooperation with each other, it is possible to improve the responsiveness of the cooling water temperature at the time of transition from the high water temperature state that emphasizes fuel efficiency to the low water temperature state that emphasizes output.

It is a schematic structure figure showing an example of a cooling system which cools an engine. It is a block diagram of various functions with which the engine control unit was equipped. It is a flowchart which shows an example of radiator fan control. It is explanatory drawing of the method of setting the cooling water target temperature in a radiator fan. It is a time chart which shows the control state of the radiator fan air volume in the case of controlling the cooling water temperature of a radiator. It is explanatory drawing of a fuel consumption priority area | region and an output importance area | region. It is explanatory drawing of the setting method of the upper limit in a fuel consumption priority area | region. It is a time chart which shows the control state of the radiator fan air volume in the case of controlling the cooling water temperature of an engine. It is a flowchart which shows an example of thermostat control. It is explanatory drawing of the method of correct | amending the control gain of a thermostat. It is a time chart which shows the control state of a thermostat at the time of transfering from a fuel consumption priority state to an output priority state. It is a time chart which shows the control state of a thermostat at the time of transfering from an output emphasis state to a fuel consumption emphasis state.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows an example of a cooling system for cooling an engine.
Cooling water that has cooled the cylinder block, cylinder head, and the like of the engine 10 is guided to the radiator 16 provided with the electric radiator fan 14 (electric fan) via the first cooling water passage 12. The cooling water guided to the radiator 16 exchanges heat with the outside air when passing through the radiator core to which the fins are attached, and the temperature thereof decreases. Then, the cooling water whose temperature has been lowered by passing through the radiator 16 is returned to the engine 10 via the second cooling water passage 18.

  Further, the first cooling water passage 12 and the second cooling water passage 18 are connected via a bypass passage 20 so that the cooling water discharged from the engine 10 bypasses the radiator 16. An electronically controlled thermostat that opens or closes the passage area of the bypass passage 20 in a multi-stage or continuous manner from fully open to fully closed at the junction between the downstream end of the bypass passage 20 and the second coolant passage 18. 22 is disposed. Therefore, by controlling the thermostat 22, it becomes possible to change the ratio of the cooling water passing through the radiator 16, and the cooling water temperature in the engine cooling system can be controlled. The thermostat 22 may be disposed at a joint portion between the upstream end of the bypass passage 20 and the first cooling water passage 12.

  A mechanical water pump 24 and an electric motor that forcibly circulate cooling water between the engine 10 and the radiator 16 at the downstream end of the second cooling water passage 18 and the intermediate portion downstream of the thermostat 22. Water pumps 26 are respectively provided. The mechanical water pump 24 is attached so as to close the cooling water inlet of the engine 10 and is driven by, for example, a camshaft of the engine 10. The electric water pump 26 is driven by, for example, a brushless motor as a drive source different from the engine 10 so that the cooling performance can be exhibited even when the engine 10 is stopped by the idle stop function.

  As a control system for controlling the driving of the radiator fan 14, the thermostat 22 and the electric water pump 26, a water temperature sensor 28 for detecting the temperature (cooling water temperature) of the cooling water discharged from the engine 10, a vehicle speed sensor 30 for detecting the vehicle speed, A temperature sensor 32 for detecting the outside air temperature, a rotation speed sensor 34 for detecting the engine rotation speed, and a load sensor 36 for detecting the engine load are attached. Here, as the engine load, for example, a state quantity closely related to the engine torque, such as an intake flow rate, an intake negative pressure, a supercharging pressure, a fuel injection amount, an accelerator opening degree, and a throttle opening degree, can be applied. The output signals of the water temperature sensor 28, the vehicle speed sensor 30, the temperature sensor 32, the rotation speed sensor 34, and the load sensor 36 are input to an engine control unit 38 having a built-in computer and stored in a ROM (Read Only Memory) or the like. The radiator fan 14, the thermostat 22 and the electric water pump 26 are controlled according to the control program.

  Specifically, the engine control unit 38 operates the electric water pump 26 when the engine 10 is stopped by an idle stop function, for example. Further, the engine control unit 38 is configured so that the cooling water temperature of the radiator 16 excludes the radiator 16 in the fuel consumption-oriented state in order to ensure responsiveness when the fuel temperature-oriented high water temperature state is shifted to the output-oriented low water temperature state. The radiator fan 14 and the thermostat 22 are controlled so as to be lower than the cooling water temperature of the cooling system.

  Note that at least one of the coolant temperature, the vehicle speed, the outside air temperature, the engine rotation speed, and the engine load may be read from, for example, another control unit connected via a CAN (Controller Area Network). The radiator fan 14, the thermostat 22 and the electric water pump 26 are not limited to the engine control unit 38, and may be controlled by a dedicated control unit or another control unit.

FIG. 2 shows various functions provided in the engine control unit 38.
The engine control unit 38 implements a target temperature setting unit 38A, a cooling water temperature estimation unit 38B, a radiator fan control unit 38C, a control gain setting unit 38D, and a thermostat control unit 38E by executing a control program.

  The target temperature setting unit 38A sets the target temperature of the cooling water in the radiator 16 based on the cooling water temperature. The coolant temperature estimating unit 38B estimates the coolant temperature in the radiator 16 based on the coolant temperature, the vehicle speed, the outside air temperature, the engine rotation speed, and the engine load. The radiator fan control unit 38C controls driving of the radiator fan 14 based on the target temperature of the cooling water set by the target temperature setting unit 38A and the cooling water temperature estimated by the cooling water temperature estimation unit 38B. The control gain setting unit 38D sets a control gain for performing feedback control of the thermostat 22 to the target opening based on the cooling water temperature estimated by the cooling water temperature estimation unit 38B. The thermostat control unit 38E feedback-controls the thermostat 22 to the target opening based on the control gain set by the control gain setting unit 38D.

  In FIG. 3, the target temperature setting unit 38A, the cooling water temperature estimation unit 38B, and the radiator fan control unit 38C of the engine control unit 38 cooperate with each other at a predetermined time when the ignition switch is turned on. An example of the radiator fan control to perform is shown.

  In step 1 (abbreviated as “S1” in the figure, the same applies hereinafter), the target temperature setting unit 38A sets the target temperature Rt of the cooling water in the radiator 16 based on the cooling water temperature detected by the water temperature sensor 28. To do. That is, as shown in FIG. 4, when the capacity of the radiator 16 is Rc [L] and the total capacity of the engine cooling system is Ac [L], the target temperature setting unit 38A determines that “Rt = (target temperature minimum value × The target temperature Rt of the cooling water is calculated by substituting the cooling water temperature into the equation “Ac− (Ac−Rc) × cooling water temperature) / Rc”. Here, as the target temperature minimum value, the minimum value of the target temperature of the engine cooling system, specifically, the cooling water temperature with emphasis on output, which is lower than the cooling water temperature with emphasis on fuel efficiency, is used. Note that the target temperature Rt has the outside air temperature as the minimum value.

The meaning of the target temperature Rt of the cooling water will be described as follows.
When moving from a fixed-level drive where the coolant temperature is controlled to a higher target temperature with emphasis on fuel efficiency to a fully open region where the coolant temperature is controlled to a lower target temperature with emphasis on output, the coolant temperature of the engine cooling system For example, from 105 ° C. to 90 ° C. Assuming that the radiator capacity Rc is 3 L and the total capacity Ac of the engine cooling system is 10 L, the engine cooling system is obtained by mixing 3 L cooling water of the radiator 16 with 7 L of the engine cooling system excluding the radiator 16 and 105 ° C. cooling water. The cooling water temperature will be 90 ° C. In this case, the target temperature is determined as to how much cooling water of the radiator 16 should be used. In the above example, the target temperature Rt = (90 [° C.] × 10 [L] − (10 [L] −3 [L]) × 105 [° C.]) / 3 [L] = 55 [° C.].

  In step 2, the coolant temperature estimation unit 38B detects the coolant temperature detected by the coolant temperature sensor 28, the vehicle speed detected by the vehicle speed sensor 30, the outside air temperature detected by the temperature sensor 32, and the rotational speed sensor 34. Based on the engine speed and the engine load detected by the load sensor 36, the coolant temperature in the radiator 16 is estimated. In other words, the cooling water temperature estimation unit 38B determines that “cooling water temperature estimated value = cooling water temperature × (a / vehicle speed) × (outside air temperature / b) × (lift amount / c) × (d / radiator fan rotational speed) × The cooling water temperature is estimated by substituting the cooling water temperature, the vehicle speed, the outside air temperature, the engine rotation speed, and the engine load into the equation of (engine rotation speed / e) × (engine load / f) ”. Here, the lift amount is a control variable indicating how much the valve body of the thermostat 22 is lifted from the seated state, and can be obtained from, for example, a control signal output to the thermostat 22. Further, a to f in the above formula are constants for correcting the coolant temperature at the engine outlet by the vehicle speed, the outside air temperature, the lift amount, the radiator fan rotation speed, the engine rotation speed, and the engine load. It has a meaning.

  As the vehicle speed increases, the traveling wind passing through the radiator 16 increases and the cooling water temperature decreases, so correction using the reciprocal of the vehicle speed is performed. The higher the outside air temperature, the lower the heat dissipation efficiency of the radiator 16 and the higher the cooling water temperature. Therefore, a correction proportional to the outside air temperature is performed. As the lift amount increases, the amount of cooling water that does not pass through the radiator 16 increases and the cooling water temperature rises. Therefore, correction proportional to the lift amount is performed. Since the wind passing through the radiator 16 increases and the coolant temperature decreases as the radiator fan rotational speed increases, correction using the reciprocal of the radiator fan rotational speed is performed. Since the heat generation amount increases and the coolant temperature rises as the engine speed increases, correction is performed in proportion to the engine speed. As the engine load is higher, the amount of heat generation increases and the coolant temperature rises. Therefore, correction proportional to the engine load is performed.

  Instead of estimating the coolant temperature in the radiator 16, a coolant temperature sensor that detects the coolant temperature in the radiator 16 may be attached, and the coolant temperature detected by the coolant temperature sensor may be used.

  In step 3, the radiator fan control unit 38C completes warming up of the engine 10 through whether or not the cooling water temperature detected by the water temperature sensor 28 is equal to or higher than a first temperature (for example, 80 ° C.). It is determined whether or not. If it is determined that the engine 10 has been warmed up, the radiator fan control unit 38C proceeds to step 4 (Yes), while if it is determined that the engine 10 has not been warmed up, the process is performed. Is terminated (No).

  In Step 4, the radiator fan control unit 38C determines whether the target temperature set in Step 1 is equal to or higher than a second temperature (for example, 105 ° C.) or not. ). And if the radiator fan control part 38C determines that it is a fuel consumption emphasis state, while advancing a process to step 5 (Yes), it is not a fuel economy emphasis state, that is, it is a low water temperature state (output emphasis state) in which output is emphasis. If it is determined, the process proceeds to step 8 (No).

  In addition, since there is a possibility that hunting may occur when the fuel consumption priority state and the output priority state are frequently switched, the first threshold value for determining the transition from the fuel efficiency priority state to the output priority state and the fuel efficiency priority from the output priority state. A so-called “hysteresis” may be provided by making the second threshold value for determining the transition to the state different.

  In step 5, the radiator fan control unit 38C determines whether or not the deviation between the target temperature set in step 1 and the coolant temperature (estimated temperature) estimated in step 2 is within a predetermined value. If the radiator fan control unit 38C determines that the deviation between the target temperature and the estimated temperature is within the predetermined value, the process proceeds to step 6 (Yes), while the deviation between the target temperature and the estimated temperature is the predetermined value. If it is determined that the value is larger, the process proceeds to Step 8 (No).

  In Step 6, the radiator fan control unit 38C controls the air volume of the radiator fan 14 so that the coolant temperature in the radiator 16 becomes the target temperature. That is, the radiator fan control unit 38C outputs a control signal corresponding to the deviation between the target temperature set in step 1 and the estimated temperature estimated in step 2 to the radiator fan 14, whereby the coolant temperature in the radiator 16 is increased. To be the target temperature.

  Specifically, when the radiator fan 14 is driven by PWM (pulse width modulation) control, the radiator fan control unit 38 </ b> C, as shown in FIG. 5, if the cooling water temperature in the radiator 16 is higher than the target temperature, The air volume of the radiator fan 14 is PID controlled with a duty ratio that increases as the deviation between the temperature and the target temperature increases. If the coolant temperature in the radiator 16 is lower than the target temperature, the radiator fan control unit 38C does not need to cool the coolant with the radiator 16, and therefore sets the duty ratio of PWM control to 0. Further, when the radiator fan 14 is driven by ON / OFF control, the radiator fan control unit 38C turns on the radiator fan 14 if the coolant temperature in the radiator 16 is higher than the target temperature, as shown in FIG. On the other hand, if the coolant temperature in the radiator 16 is lower than the target temperature, the radiator fan 14 is turned off. Note that the control of the radiator fan 14 in step 6 is performed in a fuel efficiency-oriented region where the vehicle speed and the load are small, as shown in FIG.

  At this time, if the radiator fan 14 is operated without restriction, the fuel consumption may be reduced due to an increase in power consumption or the durability of the radiator fan 14 may be affected. A value may be set. That is, the amount of air necessary for setting the coolant temperature in the radiator 16 to the target temperature is maximum when the vehicle speed is low and the load is high, and is minimum when the vehicle speed is high and the load is low. For this reason, as shown in FIG. 7, in the fuel efficiency-oriented region, an upper limit value is set that takes a small value when the vehicle speed is high and the load is low, and takes a large value when the vehicle speed is low and the load is high. Alternatively, the ON time should not exceed the upper limit value. In particular, for vehicle speed and load in the vicinity of a fixed ground travel line, it is preferable to set an upper limit within a range that has little influence on fuel consumption.

  In step 7, the radiator fan control unit 38C determines whether or not the target temperature of the cooling water has shifted from the fuel efficiency important region to the output important region. That is, the radiator fan control unit 38C determines whether or not the target temperature set in Step 1 has shifted to the output-oriented region through whether or not the target temperature has crossed a predetermined temperature that defines the fuel-considered and output-oriented regions. Determine. If it is determined that the radiator fan control unit 38C has shifted to the output-oriented region, the process proceeds to step 8 (Yes), while if it is determined that the region has not shifted to the output-oriented region, the process is terminated (No). .

  In step 8, the radiator fan control unit 38C controls the air volume of the radiator fan 14 so that the coolant temperature supplied to the engine 10 becomes the target temperature. That is, the radiator fan control unit 38C outputs a control signal corresponding to the deviation between the coolant temperature and the target temperature to the radiator fan 14 so that the coolant temperature becomes the target temperature.

  Specifically, as shown in FIG. 8, when the radiator fan control unit 38 </ b> C shifts from a high water temperature state with emphasis on fuel efficiency to a low water temperature state with emphasis on output, the radiator fan control unit 38 </ b> C rapidly sets the coolant temperature at least by the change in the target temperature. Since it is desired to decrease, the air volume of the radiator fan 14 is controlled according to the deviation between the coolant temperature and the target temperature. In this case, if the radiator fan 14 is driven by PWM control, as shown in FIG. 8, the radiator fan 14 is PID-controlled with a duty ratio corresponding to a deviation obtained by subtracting the target temperature from the coolant temperature. On the other hand, if the radiator fan 14 is driven by ON / OFF control, as shown in FIG. 8, the radiator fan 14 is turned on if the cooling water temperature is higher than the target temperature, while the cooling water temperature is lower than the target temperature. If low, the radiator fan 14 is turned off.

  According to this radiator fan control, when the warm-up of the engine 10 is completed, the fuel consumption is important, and the deviation between the target temperature and the estimated temperature is within a predetermined value, the coolant temperature in the radiator 16 is increased. The air volume of the radiator fan 14 is controlled so as to be lower than the cooling water temperature of the engine cooling system except for. At this time, if the warm-up of the engine 10 has not been completed, the radiator fan 14 is not driven, so that inhibition of warm-up promotion can be suppressed. In addition, when the output is important, or when the deviation between the target temperature and the estimated temperature exceeds a predetermined value, the radiator fan 14 is set so that the coolant temperature supplied to the engine 10 approaches the target temperature according to the operating state. The air volume is controlled. For this reason, in the case of steady running, that is, when the operation in the same operation region continues, the coolant temperature corresponding to the operation state at that time can be maintained.

  FIG. 9 shows that the target temperature setting unit 38A, the cooling water temperature estimation unit 38B, the control gain setting unit 38D, and the thermostat control unit 38E of the engine control unit 38 cooperate with each other when the ignition switch is turned on. An example of the thermostat control performed repeatedly every predetermined time is shown.

  In step 11, the target temperature setting unit 38 </ b> A sets a target temperature Rt for the cooling water in the radiator 16 based on the cooling water temperature detected by the water temperature sensor 28. In addition, since the setting method of the target temperature Rt of cooling water is the same as that of step 1 in FIG. 3, please refer to the description.

  In step 12, the cooling water temperature estimation unit 38 </ b> B is detected by the cooling water temperature detected by the water temperature sensor 28, the vehicle speed detected by the vehicle speed sensor 30, the outside air temperature detected by the temperature sensor 32, and the rotational speed sensor 34. Based on the engine speed and the engine load detected by the load sensor 36, the coolant temperature in the radiator 16 is estimated. The method for estimating the cooling water temperature is the same as that in step 2 in FIG. 3, so refer to the description thereof.

  In step 13, the control gain setting unit 38D completes warming up of the engine 10 through whether or not the cooling water temperature detected by the water temperature sensor 28 is equal to or higher than a first temperature (for example, 80 ° C.). It is determined whether or not. If the control gain setting unit 38D determines that the engine 10 has been warmed up, the control gain setting unit 38D advances the process to step 14 (Yes), while determining that the engine 10 has not been warmed up, the process Is terminated (No).

  In step 14, the control gain setting unit 38 </ b> D determines whether or not the fuel consumption priority state is established through whether or not the target temperature set in step 11 is equal to or higher than a second temperature (for example, 105 ° C.). To do. Then, if the control gain setting unit 38D determines that the fuel economy is important, the process proceeds to step 15 (Yes), while if it is determined that the fuel economy is not important, that is, the output is important, the process proceeds to step 17. Proceed to No (No).

  In step 15, the control gain setting unit 38D determines whether or not the deviation between the target temperature and the estimated temperature is within a predetermined value. Then, if the control gain setting unit 38D determines that the deviation between the target temperature and the estimated temperature is within the predetermined value, the process proceeds to step 16 (Yes), while the deviation between the target temperature and the estimated temperature is the predetermined value. If it is determined that the value is larger, the process proceeds to Step 17 (No).

  In step 16, the control gain setting unit 38D sets a control gain for performing PID control of the thermostat 22 based on the deviation between the target temperature and the coolant temperature. Further, since the required gain differs according to the coolant temperature in the radiator 16, the control gain setting unit 38D corrects the control gain based on the deviation between the target temperature and the estimated temperature as follows.

  That is, when the change in the lift amount of the thermostat 22 is the same, the lower the cooling water temperature in the radiator 16, the greater the temperature influence of the engine cooling system. For this reason, as shown in FIG. 10, when the coolant temperature in the radiator 16 is low and the deviation from the target temperature is large, the control gain is corrected to be small and the change in the lift amount of the thermostat 22 is suppressed. Regardless of the cooling water temperature in the radiator 16, the controllability of the cooling water temperature can be improved.

Specifically, TERR: cooling water temperature-target temperature, TERRz: previous TERR value, Pgain: P minute basic gain value, Igain: I minute basic gain value, Dgain: D minute basic gain value, RADHOSP: Pgain correction value , RADHOSI: Igain correction value, RADHOSD: Dgain correction value,
Control gain for P = TERR × Pgain × RADHOSP
Control gain for I = TERR × Igain × RADHOSI
Control gain for D = (TERR−TERRz) × Dgain × RADHOSD
It can be expressed as. The thermostat 22 is PID controlled using this control gain.

  In step 17, the control gain setting unit 38D clears RADHOSP, RADHOSI, and RADHOSD in order to stop the correction based on the deviation between the target temperature and the estimated temperature for the control gain for performing PID control of the thermostat 22, in short, these Is set to 1.

  That is, when shifting from a high water temperature state with emphasis on fuel efficiency to a low water temperature state with emphasis on output, it is desired to rapidly reduce the cooling water temperature by at least the change in the target temperature, as shown in FIG. For this reason, the control gain for performing the PID control of the thermostat 22 is set according to the deviation between the target temperature and the coolant temperature, and the correction for reducing the control gain is stopped. In this case, the control gain in PID control is as follows.

Control gain for P = TERR × Pgain
Control gain for I = TERR × Igain
Control gain for D = (TERR−TERRz) × Dgain
In step 18, the thermostat control unit 38 </ b> E adjusts the valve opening of the thermostat 22 so that the coolant temperature supplied to the engine 10 becomes the target temperature based on the control gain set in step 16 or step 17. Control. Specifically, the thermostat control unit 38E performs PID control of the thermostat 22 based on the control gain at a duty ratio that increases as the deviation between the target temperature and the estimated temperature increases.

  According to this thermostat control, when the warm-up of the engine 10 is completed, the fuel consumption is emphasized, and the deviation between the target temperature and the estimated temperature is within a predetermined value, depending on the deviation between the target temperature and the estimated temperature. The thermostat 22 is PID-controlled by the control gain so that the coolant temperature becomes the target temperature. At this time, if the cooling water temperature is higher than the target temperature, the lift amount of the thermostat 22 is set according to these deviations, so the flow rate of the cooling water passing through the radiator 16 becomes small or zero, and the air blown by the radiator fan 14 As a result, the temperature decreases.

  Further, when shifting from the output-oriented state to the fuel-consumption-oriented state, as shown in FIG. 12, the output-oriented state control is continued until the deviation between the target temperature and the estimated temperature is within a predetermined value. Thus, it is possible to perform control in consideration of the operation delay of the thermostat 22.

  When the radiator fan control and the thermostat control are performed in parallel, when the fuel temperature-oriented high water temperature state shifts to the output-oriented low water temperature state, the high-temperature cooling water and the low-temperature cooling water Are mixed to lower the temperature of the coolant supplied to the engine 10. For this reason, even immediately after the shift from the fuel efficiency-oriented state to the output-oriented state, it is possible to supply the coolant with the low water temperature state to the engine 10 and meet output demands such as acceleration performance.

Here, technical ideas other than the claims that can be grasped from the above embodiment will be described together with effects.
(A) In the engine control device according to any one of claims 1 to 3,
An engine control device that limits an operation amount of the electric fan according to a vehicle speed and an engine load.
According to the above configuration, since the cooling capacity of the radiator according to the vehicle state is taken into consideration, it is possible to suppress the decrease in fuel consumption due to the increase in power consumption and the influence on the durability of the electric fan.

(B) In the engine control device according to any one of claims 1 to 3 or (A),
The engine control apparatus which sets the operation amount of the said thermostat and the said electric fan according to the deviation of the temperature of the cooling water in the said radiator, and the target temperature of the cooling water in the said radiator.
According to the above configuration, the operation amount of the thermostat and the electric fan is set according to the deviation between the cooling water temperature and the target temperature in the radiator. Electric power can be suppressed.

(C) In the engine control device according to any one of claims 1 to 3, (a) or (b),
Immediately after the target temperature of the cooling water in the engine cooling system shifts from the low temperature side to the high temperature side, the deviation between the cooling water temperature in the engine cooling system and the cooling water target temperature in the engine cooling system is a predetermined value. An engine control device that continues the control on the low temperature side until the value falls within the range.
According to the above configuration, immediately after the target temperature of the cooling water in the engine cooling system shifts from the low temperature side to the high temperature side, even if the operation amount of the electronically controlled thermostat is zero, there is a certain delay until the thermostat is closed. Therefore, it is possible to realize thermostat control in consideration of this delay.

    DESCRIPTION OF SYMBOLS 10 ... Engine, 12 ... 1st cooling water passage, 14 ... Radiator fan (electric fan), 16 ... Radiator, 18 ... 2nd cooling water passage, 20 ... Bypass passage, 22 ... Thermostat, 28 ... Water temperature sensor, 30 ... Vehicle speed sensor, 32 ... Temperature sensor, 34 ... Rotational speed sensor, 36 ... Load sensor, 38 ... Engine control unit, 38A ... Target temperature setting unit, 38B ... Cooling water temperature estimation unit, 38C ... Radiator fan control unit, 38D ... Control gain setting unit, 38E ... Thermostat control unit

Claims (2)

In the engine cooling system, an electronically controlled thermostat that changes the flow distribution to the radiator and an electric fan that blows air to the radiator are arranged, and the target temperature of cooling water in the engine cooling system is a predetermined value The engine control device characterized by controlling the thermostat to the closed side and controlling the air flow rate of the electric fan so that the temperature of the cooling water in the radiator decreases when the temperature exceeds. When the temperature of the cooling water in the radiator is lower than a predetermined value, at least, based on the temperature of the cooling water in the radiator, according to claim 1, wherein the controlling thermostat to the closing side, characterized in that Engine control device.