JP4975153B2 - Cooling device for internal combustion engine - Google Patents

Description

  The present invention relates to a cooling device for an internal combustion engine that cools a water-cooled internal combustion engine, and more particularly to controlling the temperature of cooling water.

  In general, in order to improve the fuel efficiency of a vehicle equipped with a water-cooled internal combustion engine (hereinafter referred to as a water-cooled engine), the temperature of the cooling water (hereinafter referred to as the cooling water temperature) is increased during low-load driving. It is known that driving a water-cooled engine can reduce cooling loss and friction loss of the water-cooled engine. However, it is desirable to drive the water-cooled engine at a low cooling water temperature for the purpose of suppressing knocking and improving the air filling rate of the water-cooled engine during high-load traveling.

  Therefore, the load change rate of the water-cooled engine is integrated, and a learning value is calculated as a time average from the start of traveling. When this learning value is larger than a predetermined value, a cooling device is used for low-temperature control. It is disclosed (for example, see Patent Document 1).

  In addition, a cooling device is disclosed that sets a target temperature so as to improve the overall efficiency in consideration of the drive consumption energy of the electric water pump and the electric cooling fan and the energy of the engine efficiency improvement due to the change in cooling water temperature ( For example, see Patent Document 2).

JP 2003-193838 A JP 2004-204708 A

  However, in the cooling device described in Patent Document 1, since the target cooling water temperature is set stepwise with respect to the driver's operation, the responsiveness when the driving style changes is poor, and the target cooling water temperature depends on the engine output. There is a problem that the optimum cooling water temperature is not set.

Further, the cooling device described in Patent Document 2 does not consider actual load fluctuations, and the overall efficiency may deteriorate instead of simply performing the target cooling water temperature control based on the engine efficiency map. For example, when there is a temporary high-load output, the process shifts to low-temperature control with good engine efficiency. However, when the output becomes low-load output after that, the engine efficiency decreases and the fuel consumption deteriorates.
In addition, since the electric water pump is driven based on the engine efficiency and the power consumption of the cooling device, if the heat dissipation efficiency decreases due to contamination of the radiator, efficient cooling cannot be performed and the cooling water temperature can rise excessively There is sex.

  The present invention has been made to solve the above-described problems, and contributes to improving the fuel consumption of the engine by setting a target cooling water temperature with good control responsiveness and optimal engine driving efficiency. An object of the present invention is to provide a cooling device for an internal combustion engine that suppresses overheating and knocking.

A cooling device for an internal combustion engine according to the present invention includes a water jacket that is provided around a cylinder of a water-cooled engine and in which cooling water flows, a radiator that radiates cooling water flowing from the water jacket, and cooling water that is radiated by the radiator An electric water pump that circulates by returning it to the water jacket, an electric cooling fan that blows air to the radiator, and a cooling water temperature control device that controls the electric water pump and the electric cooling fan , wherein the cooling Cooling water temperature detecting means for detecting the water temperature of the water is provided, and the cooling water temperature control device calculates the engine output from the rotation speed and output torque of the water-cooled engine, and calculates the target cooling water temperature based on the engine output. Smoothing the time variation of the target cooling water temperature And means, means for smoothing the time variation of the target coolant temperature, the target coolant temperature is calculated based on the engine output is corrected by a function with a time constant of the primary delay, the time change is smooth In the internal combustion engine cooling system that controls the electric water pump and the electric cooling fan based on the target cooling water temperature to be converted, the time constant of the first-order lag is set based on the target cooling water temperature calculated based on the engine output And the means for setting the time constant sets a time constant that is smaller as the target cooling water temperature is higher.

The cooling device for an internal combustion engine according to the present invention corrects the target cooling water temperature according to the engine output by a function having a time constant of a first-order lag, and therefore can suppress hunting of the target cooling water temperature for a temporary high engine output, which is unnecessary. It is possible to reduce the operation of the electric water pump and the electric cooling fan and to efficiently drive the engine at the optimum cooling water temperature.
Further, when the absolute value of the difference between the cooling water temperature and the target cooling water temperature is equal to or less than a predetermined value, the electric water pump is intermittently driven or stopped, so that the power consumption of the electric water pump can be reduced. When the cooling water temperature value is equal to or higher than the abnormal value, knocking and overheating can be suppressed because the electric water pump and the electric cooling fan are continuously operated.

It is a figure which shows the structure of the cooling device of the vehicle carrying the water cooling type engine which concerns on Embodiment 1 of this invention. It is a functional block diagram of the cooling water temperature control apparatus of FIG. It is a flowchart which shows the drive process based on the target cooling water temperature correct | amended by the function with a primary delay time constant in the cooling water temperature control apparatus which concerns on Embodiment 1 of this invention. It is a functional block diagram of the cooling water temperature control apparatus which concerns on Embodiment 2 of this invention. It is a flowchart which shows the drive process based on the target cooling water temperature restrict | limited by the temperature change rate in the cooling water temperature control apparatus which concerns on Embodiment 1 of this invention.

A preferred embodiment of a cooling water temperature control device for an internal combustion engine according to the present invention will be described below with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a configuration diagram showing an entire vehicle equipped with a cooling device for an internal combustion engine according to Embodiment 1 of the present invention. FIG. 2 is a functional block diagram of the coolant temperature control apparatus according to Embodiment 1 of the present invention.
The vehicle 1 according to the present invention is equipped with a water-cooled engine 2, and a cooling device for water-cooling the water-cooled engine 2 is provided around a cylinder (not shown) of the water-cooled engine 2, and cooling water flows in from the inlet. A water jacket 3 discharged from the through outlet, a radiator 6 that dissipates heat by applying air from outside to the cooling water flowing inside, and an electric water pump 8 that is disposed at the inlet of the water jacket 3 and circulates the cooling water. A cooling water temperature sensor 4 as a cooling water temperature detecting means for detecting the temperature of the cooling water flowing through the outlet of the water jacket 3, a first water passage 11 communicating the outlet of the water jacket 3 and the inlet of the radiator 6, and the radiator 6. And a second water channel 12 communicating with the inlet of the electric water pump 8.

  In addition, the cooling device for cooling the water-cooled engine 2 with water is a first T-type branch pipe 13 interposed in the middle of the first water channel 11 and a second one interposed in the middle of the second water channel 12. The T-type branch pipe 14, the bypass water channel 5 that communicates one end of the first T-type branch pipe 13 and one end of the second T-type branch pipe 14, and the second T-type branch pipe 14 are arranged. In addition, a thermostat 7 for switching the cooling water flowing into the electric water pump 8 from the radiator 6 or the bypass water channel 5, an electric cooling fan 9 for cooling the radiator 6 by air, an electric water pump 8 and an electric cooling fan 9 to keep the cooling water temperature optimal. And a cooling water temperature control device 10 that performs the rotation control.

  In the water-cooled engine 2, dust or the like is removed from the air drawn from the air intake by an air cleaner, and air is supplied to each cylinder from the intake manifold. The supplied air is mixed with the fuel injected by the injector in the cylinder to become an air-fuel mixture, and is burned by the spark generated by the spark plug. The piston in the cylinder reciprocates due to the expansion force of the combustion, and this movement is converted into the driving force of the vehicle 1 by the crankshaft.

  The water-cooled engine 2 has a risk of causing knocking or the like when a cylinder in the water-cooled engine 2 becomes hot due to combustion. Therefore, a water jacket 3 is provided around the cylinder in the water-cooled engine 2 to cool the cylinder that has become hot due to combustion.

  The cooling water temperature sensor 4 detects the temperature of the cooling water circulating in the cooling water passage of the water-cooled engine 2 and outputs a signal to the cooling water temperature control device 10.

  The bypass water channel 5 bypasses the radiator 6 from the outlet of the water jacket 3 and communicates with the inlet of the electric water pump 8. When the cooling water temperature is equal to or lower than the warm-up temperature, the friction loss of the water-cooled engine 2 is increased and the fuel consumption is deteriorated. Therefore, the cooling water flowing out from the outlet of the water jacket 3 is caused to flow into the bypass water channel 5 to be in the water jacket 3. The temperature drop of the cooling water flowing through and the drive loss of the electric water pump 8 are reduced.

  The radiator 6 radiates the cooling water heated by the water-cooled engine 2. The amount of heat radiated from the radiator 6 is determined by the amount of air passing through the radiator 6 and the flow rate of cooling water flowing through the radiator 6.

The thermostat 7 switches between flowing the cooling water to the bypass water channel 5 or the radiator 6 by opening and closing the valve according to the cooling water temperature.
When the cooling water temperature is lower than a predetermined value, the valve of the thermostat 7 is closed, and a bypass water channel 5 that bypasses the radiator 6 and a water channel that circulates through the water jacket 3 are formed. The cooling water circulation path promotes warm-up of the water-cooled engine 2 without lowering the temperature of the cooling water.

  When the cooling water temperature is equal to or higher than a predetermined value, the valve of the thermostat 7 is opened, and a water passage that circulates between the radiator 6 and the water jacket 3 is formed. The cooling water is radiated by the radiator 6 through the cooling water circulation path.

  The electric water pump 8 is composed of an electric motor and an impeller, and controls the flow rate of the cooling water circulating in the cooling device. The electric water pump 8 is supplied with electric power from a battery mounted on the vehicle 1, and the number of revolutions of the impeller is controlled by the cooling water temperature control device 10.

  The electric cooling fan 9 is composed of an electric motor and a fan, and controls the amount of air passing through the radiator 6. The electric cooling fan 9 is supplied with electric power from a battery mounted on the vehicle 1, and the number of rotations of the fan is controlled by the cooling water temperature control device 10.

  As shown in FIG. 2, the cooling water temperature control apparatus 10 includes means 31 for calculating the engine output from the rotational speed NE and the output torque N of the water-cooled engine 2, and means for calculating the target cooling water temperature Ta based on the engine output. 32, a means 33 for smoothing the time change of the target cooling water temperature Ta with a function having a time constant τ of the first order lag, and a time constant τ of the first order lag based on the target cooling water temperature Ta calculated based on the engine output. Means 34 for setting, and means 35 for controlling the cooling water temperature by driving the electric water pump 8 and the electric cooling fan 9 based on the target cooling water temperature whose time change is smoothed.

  The cooling water temperature control device 10 is composed of a computer having a CPU, a memory, and an interface, and a program is stored in the memory, and the CPU takes in via the interface in accordance with an instruction of the program read from the memory. Calculation is performed using the data, and the calculation result is output via the interface.

The means 33 for smoothing the time variation of the target coolant temperature corrects the target coolant temperature Ta calculated based on the engine output by a function having a first-order delay time constant τ.
The means 34 for setting the time constant sets a time constant τ that is smaller as the target cooling water temperature Ta is higher.

  The cooling water temperature control device 10 sets an optimum target cooling water temperature for combustion of the water-cooled engine 2 mounted on the vehicle 1, and improves the fuel consumption of the vehicle 1 and prevents knocking so that the electric water pump 8 and the electric cooling fan are used. 9 is controlled. In addition, the coolant temperature control apparatus 10 may use the engine control unit of the vehicle 1 in order to easily acquire vehicle information.

  The cooling water temperature control device 10 detects the output of the water-cooled engine 2 in order to estimate the target cooling water temperature optimal for the water-cooled engine 2 to burn. The output of the water-cooled engine 2 is calculated from the rotational speed NE and the output torque N of the water-cooled engine 2. At this time, the rotational speed NE of the water-cooled engine 2 is obtained from the crank angle sensor 21, and the output torque N is obtained from the intake pressure measured by the intake pressure sensor 22 disposed in the intake manifold and the fuel injection amount of the injector.

  The cooling water temperature control device 10 corrects the target cooling water temperature with a function having a first-order lag time constant τ because the cooling water temperature is not lowered by a temporary engine output.

  The cooling water temperature control device 10 sets the time constant τ according to the target cooling water temperature Ta. When the target cooling water temperature Ta is high, the time constant τ is reduced to improve the responsiveness and make it easier to shift to the optimum temperature for driving the engine. Further, when the target cooling water temperature Ta is low, the time constant τ is increased to suppress a decrease in the cooling water temperature due to a temporary high engine output.

  When the absolute value of the difference between the target cooling water temperature Ta and the cooling water temperature T is equal to or less than a predetermined value, the cooling water temperature control device 10 reduces the wasteful power consumption of the electric water pump 8 by intermittently driving the electric water pump 8. . If the absolute value of the difference between the target cooling water temperature Ta and the cooling water temperature T is equal to or less than a predetermined value, the electric water pump 8 may be stopped.

  The cooling water temperature control device 10 continuously operates the electric water pump 8 and the electric cooling fan 9 when the cooling water temperature T is an abnormal value, and suppresses overheating and knocking.

Next, a cooling water temperature control procedure executed by the cooling water temperature control apparatus 10 according to Embodiment 1 of the present invention will be described with reference to FIG.
First, in step S101, an engine output is calculated from the rotational speed NE and the output torque N of the water-cooled engine 2 in order to set the target cooling water temperature Ta.
Next, in step S102, the target cooling water temperature Ta is calculated from the obtained engine output.

  Next, in step S103, a time constant τ is set based on the target cooling water temperature Ta.

  Next, in step S104, the target cooling water temperature Ta is corrected by a function having a first-order lag time constant τ. The time constant τ is such that the higher the target cooling water temperature Ta is, the smaller the time constant τ is, so that it is easy to shift to the target cooling water temperature Ta that is optimal for driving the engine at high temperatures, and a temporary high engine at low temperatures. Hunting of the target cooling water temperature Ta with respect to the output is suppressed.

Next, in step S105, it is determined whether or not the absolute value ΔT of the difference between the cooling water temperature T for cooling the water-cooled engine 2 and the target cooling water temperature Ta exceeds a predetermined value. When it is determined that the absolute value ΔT of the difference between the cooling water temperature T and the target cooling water temperature Ta is equal to or smaller than the predetermined value, the process proceeds to step S106, and it is determined that the absolute value ΔT of the difference between the cooling water temperature T and the target cooling water temperature Ta exceeds the predetermined value. If so, the process proceeds to step S107.
In step S106, it is determined that the cooling water temperature T is optimal for the combustion of the water-cooled engine 2, and the electric water pump 8 is intermittently driven to end the cooling water temperature control procedure.

In step S107, it is determined whether or not the cooling water temperature T exceeds an abnormality determination value. When it is determined that the cooling water temperature T exceeds the abnormality determination value, the process proceeds to step S108, and when it is determined that the cooling water temperature T is equal to or lower than the abnormality determination value, the process proceeds to step S109.
In step S108, the electric water pump 8 and the electric cooling fan 9 are continuously driven to end the cooling water temperature control procedure.

  In step S109, it is determined that the cooling system is operating normally, the electric water pump 8 and the electric cooling fan 9 are driven based on the target cooling water temperature Ta, and the cooling water temperature control procedure is terminated.

By correcting the target cooling water temperature Ta by a function having a time constant τ of the first-order delay in this way, hunting of the target cooling water temperature Ta with respect to a temporary high engine output can be suppressed, and efficient at the optimum cooling water temperature T can be achieved. Engine drive can be performed.
Further, when the engine output is maintained at a high output, the target cooling water temperature Ta becomes a low temperature, so that it is possible to suppress a decrease in output due to a decrease in the isovolume.
Further, when the absolute value of the difference between the cooling water temperature T and the target cooling water temperature Ta is equal to or less than a predetermined value, the electric water pump 8 is intermittently driven or stopped, so that the power consumption of the electric water pump 8 can be reduced.
Further, when the cooling water temperature T is abnormal, the electric water pump 8 and the electric cooling fan 9 are continuously operated, so that knocking and overheating can be suppressed.

Embodiment 2. FIG.
FIG. 4 is a functional block diagram of a coolant temperature control apparatus according to Embodiment 2 of the present invention.
The cooling device according to Embodiment 2 of the present invention is different from the cooling device according to Embodiment 1 of the present invention in that it is the same except for the cooling water temperature control device 10B. Description is omitted.
As shown in FIG. 4, the cooling water temperature control apparatus 10B according to the second embodiment of the present invention is a target cooling function that has a first-order lag time constant τ from the cooling water temperature control apparatus 10 according to the first embodiment of the present invention. The means 33 for smoothing the time change of the water temperature Ta and the means 34 for setting the time constant τ of the first-order lag based on the target cooling water temperature Ta calculated based on the engine output are omitted, and the calculation is based on the engine output. Means 33B for limiting the temperature change rate of the target coolant temperature to smooth the time change of the target coolant temperature and means 36 for setting the temperature change rate based on the target coolant temperature calculated based on the engine output are added. However, the other parts are the same, and the same parts are denoted by the same reference numerals and the description thereof is omitted.

  The means 36 for setting the temperature change rate sets a larger temperature change rate as the target cooling water temperature Ta is higher.

Next, a cooling water temperature control procedure executed by the cooling water temperature control apparatus 10B according to Embodiment 2 of the present invention will be described with reference to FIG.
First, in step S201, an engine output is calculated from the rotational speed NE and the output torque N of the water-cooled engine 2 in order to set the target cooling water temperature Ta.
Next, in step S202, the target cooling water temperature Ta is calculated from the obtained engine output.

Next, in step S203, a temperature change rate is calculated based on the target cooling water temperature Ta.
Next, in step S204, the target cooling water temperature Ta is limited by the temperature change rate. The higher the target cooling water temperature Ta, the larger the rate of change in temperature, making it easier to shift to the target cooling water temperature Ta that is optimal for engine driving at high temperatures, and target cooling for temporary high engine output at low temperatures. Suppresses hunting of water temperature Ta.

Next, in step S205, it is determined whether or not the absolute value ΔT of the difference between the cooling water temperature T for cooling the water-cooled engine 2 and the target cooling water temperature Ta exceeds a predetermined value. If it is determined that the absolute value ΔT of the difference between the cooling water temperature T and the target cooling water temperature Ta is equal to or less than the predetermined value, the process proceeds to step S206, and it is determined that the absolute value ΔT of the difference between the cooling water temperature T and the target cooling water temperature Ta exceeds the predetermined value. If so, the process proceeds to step S207.
In step S206, it is determined that the cooling water temperature T is optimal for the combustion of the water-cooled engine 2, and the electric water pump 8 is intermittently driven to end the cooling water temperature control procedure.

In step S207, it is determined whether or not the cooling water temperature T exceeds the abnormality determination value. When it is determined that the cooling water temperature T exceeds the abnormality determination value, the process proceeds to step S208, and when it is determined that the cooling water temperature T is equal to or lower than the abnormality determination value, the process proceeds to step S209.
In step S208, the electric water pump 8 and the electric cooling fan 9 are continuously driven to end the cooling water temperature control procedure.

  In step S209, it is determined that the cooling system is operating normally, the electric water pump 8 and the electric cooling fan 9 are driven based on the target cooling water temperature Ta, and the cooling water temperature control procedure is terminated.

Thus, the fluctuation | variation of the cooling water temperature by temporary engine output fluctuation | variation can be suppressed by restrict | limiting the temperature change rate of target cooling water temperature.
In addition, by setting the temperature change rate to be higher as the target cooling water temperature is higher, smooth transition to high temperature control of the cooling water and hunting of the target cooling water temperature that occurs in temporary high engine output can be suppressed.
Further, by limiting the temperature change rate, the overshoot of the target cooling water temperature can be reduced. By controlling the target cooling water temperature by setting such a temperature change rate, it is possible to set the target cooling water temperature with good control response.

The cooling apparatus for an internal combustion engine of the present invention is not limited to the above-described embodiment, and can be implemented with various modifications without departing from the spirit of the present invention. For example, the engine output is calculated from the engine speed and the output torque, but it can also be estimated from the throttle opening, intake manifold pressure, and vehicle speed.
Further, in order to prevent a temperature change of the target cooling water temperature due to a temporary high engine output, a time constant of second order or third order delay may be used instead of the first order delay time constant.
Further, although the time constant is set according to the target cooling water temperature, the time constant can also be set using the engine output.

  DESCRIPTION OF SYMBOLS 1 Vehicle, 2 Water-cooled engine, 3 Water jacket, 4 Cooling water temperature sensor, 5 Bypass water channel, 6 Radiator, 7 Thermostat, 8 Electric water pump, 9 Electric cooling fan, 10, 10B Cooling water temperature control apparatus, 11 1st water channel , 12 2nd water channel, 13 1st T type branch pipe, 14 2nd T type branch pipe, 21 crank angle sensor, 22 intake pressure sensor, 31 engine output calculation means, 32 target cooling water temperature calculation means, 33, 33B Smoothing means, 34 Time constant setting means, 35 Water temperature control means, 36 Temperature change rate setting means.

Claims (4)

A water jacket provided around the cylinder of a water-cooled engine and in which cooling water flows, a radiator that radiates cooling water flowing from the water jacket, and an electric motor that circulates the cooling water radiated by the radiator by returning it to the water jacket A cooling device for an internal combustion engine comprising a water pump, an electric cooling fan that blows air to the radiator, and a cooling water temperature control device that controls the electric water pump and the electric cooling fan ,
A cooling water temperature detecting means for detecting the cooling water temperature,
The cooling water temperature control device
Means for calculating the engine output from the rotational speed and output torque of the water-cooled engine;
Means for calculating a target cooling water temperature based on the engine output;
Means for smoothing the time variation of the target cooling water temperature,
The means for smoothing the time variation of the target cooling water temperature corrects the target cooling water temperature calculated based on the engine output by a function having a time constant of a first-order lag,
In the cooling apparatus for an internal combustion engine that controls the electric water pump and the electric cooling fan based on a target cooling water temperature at which the time change is smoothed ,
Means for setting a time constant of the first-order lag based on a target coolant temperature calculated based on the engine output,
The cooling apparatus for an internal combustion engine, wherein the means for setting the time constant sets a smaller time constant as the target cooling water temperature is higher. A water jacket provided around the cylinder of a water-cooled engine and in which cooling water flows, a radiator that radiates cooling water flowing from the water jacket, and an electric motor that circulates the cooling water radiated by the radiator by returning it to the water jacket A cooling device for an internal combustion engine comprising a water pump, an electric cooling fan that blows air to the radiator, and a cooling water temperature control device that controls the electric water pump and the electric cooling fan ,
A cooling water temperature detecting means for detecting the cooling water temperature,
The cooling water temperature control device
Means for calculating the engine output from the rotational speed and output torque of the water-cooled engine;
Means for calculating a target cooling water temperature based on the engine output;
Means for smoothing the time variation of the target cooling water temperature,
The means for smoothing the time variation of the target cooling water temperature limits the temperature change rate of the target cooling water temperature calculated based on the engine output,
In the cooling apparatus for an internal combustion engine that controls the electric water pump and the electric cooling fan based on a target cooling water temperature at which the time change is smoothed ,
Means for setting the temperature change rate based on a target cooling water temperature calculated based on the engine output,
The cooling apparatus for an internal combustion engine, wherein the means for setting the temperature change rate sets a temperature change rate that is larger as the target cooling water temperature is higher . The electric water pump, when the absolute value of the difference between the cooling water temperature and the target coolant temperature the cooling water temperature detecting means for detecting is equal to or less than a predetermined value, according to claim 1 or claims characterized in that it is intermittently driven or stopped Item 3. The cooling device for an internal combustion engine according to Item 2 . The electric water pump and the electric cooling fan are continuously driven when it is determined that the cooling water temperature detected by the cooling water temperature detecting means is an abnormal value . the cooling system of an internal combustion engine according to any one.

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