JPH05222933A - Cooling control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce fuel consumption, and to improve exhaust emission in a cooling control device for an internal combustion engine. CONSTITUTION:A cooling control device is provided with a three-way flow control valve 30 which is connected both to a cooling water passage 15b for passing low-temperature cooling water passed through a radiator 12 and to a cooling water passage 20 for passing high-temperature cooling water not passed through the radiator 12, and by which the low-temperature cooling water is mixed with the high-temperature cooling water for passing it to the suction side of a cooling water pump 13. The device is also provided with a humidity sensor 45 for detecting the humidity of intake air. An ECU 50 feedback-controls the opening of the three-way flow control valve 30 so that the cooling water temperature at the inlet of an engine is decreased as the humidity of intake air becomes lower, while it is increased as the humidity thereof becomes higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling control device for an internal combustion engine, and more particularly to a cooling control device for an internal combustion engine which controls the cooling capacity of the cooling device to improve fuel consumption and exhaust emission.

[0002]

2. Description of the Related Art A conventional cooling control device for an internal combustion engine is disclosed in, for example, Japanese Patent Laid-Open No. 168017/1982. The cooling control device disclosed in this publication is
By controlling the cooling water circulation amount of the radiator, that is, the cooling water temperature at the engine inlet according to the load of the internal combustion engine (engine) represented by the intake pipe pressure, the engine is prevented from being overcooled in the low and medium load regions. It is an improvement in efficiency and exhaust emission.

As described above, in contrast to the technique in which the temperature of the cooling water at the engine inlet is controlled to a constant value by, for example, a thermostat valve, each value of the engine operating state (engine speed, load, etc.) is used as a parameter. A cooling control device that changes and controls the cooling water temperature at the engine inlet is well known in the related art.

[0004]

Generally, various data (humidity, temperature, air density, etc.) in engine intake air
It is known that changes in the engine influence the engine performance mainly related to the engine output, such as engine output and susceptibility to knock. Further, in the conventional cooling control device, the cooling capacity is controlled by using the engine speed, the load and the like as parameters as described above, but the cooling capacity is not controlled by using the above various data of the intake air as parameters. For this reason, by performing control to change the cooling capacity according to changes in the above-mentioned various data of the intake air, it is possible to expect effects such as an increase in engine output, a reduction in combustion consumption accompanying this, and an improvement in exhaust emission. However, these effects remain unclear in the prior art.

Therefore, the present invention has been made in view of the above problems, and controls the cooling performance according to the humidity of intake air to reduce the fuel consumption and improve the exhaust emission. The purpose is to provide a device.

[0006]

FIG. 1 is a block diagram showing the principle of the present invention for achieving the above object. As shown in the figure, the present invention provides a cooling capacity adjusting means 3 for changing the cooling capacity of a cooling system 2 of an internal combustion engine 1, a humidity sensor 4 for detecting the humidity of intake air, and an output signal of the humidity sensor 4. Enter
A cooling capacity control means 5 for controlling the cooling capacity adjusting means 3 is provided so that the cooling capacity is increased as the humidity of the intake air is lower.

[0007]

It is generally known that the lower the humidity of the intake air, the less the amount of water contained in the intake air and the more likely knocking occurs. Therefore, in the present invention, the cooling capacity control means 5 controls the cooling capacity adjusting means 3 so as to increase the cooling capacity as the humidity of the intake air becomes lower, so that the wall temperature of the combustion chamber becomes lower as the humidity of the intake air becomes lower. It is possible to prevent knocking without lowering the ignition retard. In this way, the ignition retard is not performed even in the state where knocking occurs, so the output for the ignition retard increases. In addition, the maximum combustion temperature is reduced due to the decrease in the wall temperature of the combustion chamber, and the generation of nitrogen oxides (NOx) whose amount is increased / decreased according to the maximum combustion temperature is suppressed.

On the contrary, the higher the humidity of the intake air, the less likely knocking occurs. Therefore, the cooling capacity adjusting means 3 is designed to lower the cooling capacity as the humidity of the intake air increases.
By controlling the wall temperature of the combustion chamber rises, the friction loss is reduced by this, and the loss of output due to the combustion energy in the combustion chamber being absorbed by the wall surface, so-called, cooling loss is reduced. The output increases accordingly. In addition, the output increases as the wall temperature of the combustion chamber rises and the combustion speed increases.

[0009]

Embodiments of the present invention will be described with reference to the drawings.
FIG. 2 shows a system configuration diagram of an embodiment of an internal combustion engine and its peripheral devices to which the present invention is applied.

In the figure, 11 is an engine body (simply referred to as engine), 12 is a radiator, 13 is a cooling water pump which is rotationally driven by an output shaft of the engine, 14 is provided in the engine body 11, and a cylinder block and A cooling water passage for cooling the cylinder head, 15a and 15b for connecting the cooling water passage 14 and the radiator 12, 16 for a throttle body, 17 for an idle speed control valve (ISCV), and 18 for a rear water Bypass joint, 19 is a water outlet housing, 20 is cooling water from the rear water bypass joint 18, throttle body 16 and ISCV17
It is a cooling water passage to flow to.

Further, 30 is connected with a cooling water passage 20 after passing through the ISCV 17 and a cooling water passage 15b after passing through the radiator 12, respectively, and cooling water passages 15b, 2 are provided.
Cooling water pump 1
3 is a three-way flow control valve that corresponds to the cooling capacity adjusting means 3 that flows to the suction side of 3. The cooling water flowing through the cooling water passage 20 has a relatively high temperature because it flows through the cooling water passage 14 in the engine body 11 and is heated.
The cooling water flowing through 5b has a low temperature because it passes through the radiator 12. Therefore, the three-way flow control valve 3
0 adjusts the valve opening to change the ratio between the flow rate of the cooling water passage 20 flowing to the cooling water pump 13 and the flow rate of the cooling water passage 15b flowing to the cooling water pump 13.
The cooling water temperature at the engine inlet can be changed.

In FIG. 2, 31 is a heater, 32 is a part of the cooling water from the rear water bypass joint 18, and the cooling water between the three-way flow control valve 30 and the cooling water pump 13 is passed through the heater 31. A cooling water passage flowing in the passage 15b, 33 a heater water valve, and 34 a radiator 1
2 is a reserve tank, 35 is a cooling water passage to the reserve tank 34, and 36 is a radiator cap.

Further, 41 is a water temperature sensor for detecting the cooling water temperature THW at the engine inlet, and 42 is the engine body 1.
1 is a pressure sensor for detecting the intake pipe pressure P, 43 is an air flow meter for detecting the intake air amount Q, 44 is an intake air temperature sensor for detecting the intake air temperature THA, and 45 is a humidity for detecting the intake air humidity Hu. Sensors (corresponding to the humidity sensor 4), 46 are provided in a distributor (not shown), a rotation angle sensor that outputs a signal corresponding to the engine speed Ne, and 47 is a throttle valve opening θth.
Knock control system (KCS) that detects the knock and controls the ignition timing to prevent the occurrence of knock
Is.

The engine control unit (E
The CU) 50 is composed of a microcomputer, and is generally suitable for various actuators such as a fuel injection valve, an igniter, and an ISCV 17 (not shown) by inputting signals from various sensors and performing predetermined calculation and control. Is output to control the engine to a desired operating state. In the present embodiment, as will be described later in detail, signals from the various sensors 41 to 48 are input to perform calculations and various processes, thereby controlling the three-way flow control valve 30 to an appropriate opening degree. , In addition to the control of the above-mentioned various actuators.

FIG. 3 shows specific components of the ECU 50. In the figure, the same components as those in FIG.
The description is omitted. In the figure, the central processing unit (CP
U) 51 inputs and calculates data output from each sensor according to a control program, and performs processing for controlling various actuators such as a fuel injection valve, an igniter, an ISCV 17, and a three-way flow control valve 30. It has become. The read only memory (ROM) 52 is
A storage device for storing data such as the control program and the ignition timing calculation map, which is a random access memory (R
AM) 53 is a storage device for temporarily reading and writing data output from each sensor and data necessary for arithmetic control. A backup random access memory (backup RAM) 54 has an ignition switch (not shown) turned off. Is a storage device in which data and the like necessary for driving the engine are backed up by a battery power source.

The input unit 55 also shapes the input signals from the sensors such as the pressure sensor 42 and the air flow meter 43 by a waveform shaping circuit (not shown) and selectively outputs this signal to the CPU 51 by a multiplexer (not shown). I have to. In the input unit 55, if the output signal from each sensor is an analog signal, this is converted into a digital signal by the A / D converter 57. The input / output unit 56 is
A rotation angle sensor 46 which is a basis of a signal of the engine speed Ne.
The input signal from the circuit is shaped by the waveform shaping circuit, and this signal is written to the RAM 53 and the like via the input port.
Further, the input / output unit 56 is driven by a drive circuit which is driven via the output port in response to a command from the CPU 51, so that the fuel injection valve, the igniter, and the ISCV 17, 3 (not shown) are provided.
The one-way flow control valve 30 and the like are driven by a predetermined amount at a predetermined timing. The bus line 58 connects various elements such as the CPU 51 and the ROM 52, the A / D converter 57 connected to the input section 55, and the input / output section 56 to send various data.

As described above, the ECU 50 uses the fuel injection valve,
In addition to controlling various actuators such as an igniter and an ISCV 17, 3 corresponding to the cooling capacity adjusting means 3
The one-way flow control valve 30 is controlled to an appropriate opening. That is, EC
The CPU 51 in the U50 executes the processing of the flowchart described below according to the program stored in the ROM 52, and implements the cooling capacity control means 5 described above by software processing.

Next, a cooling water temperature control routine will be described as a control program constituting a main part of an embodiment of the device of the present invention.

FIG. 4 shows a flow chart of the above cooling water temperature control routine. The cooling water temperature control routine shown in the figure is interrupted and activated at predetermined time intervals. When the routine is started, first in step 102, the CPU 51 is initialized and the input data from the various sensors 41 to 48 are read. In the next step 104, the cooling water temperature THW at which the fuel consumption is best with the engine speed Ne and the load Q / Ne as parameters is obtained from the map shown in FIG.
This is the target value THW ₀ . That is, the above step 10
Among various input data in 2, the engine speed Ne and the rotation angle sensor 46 are calculated from the input data of the rotation angle sensor 46.
Also, by calculating the value of the engine load Q / Ne from the input data of the air flow meter 43 and applying it to the map shown in FIG. 5, the cooling water temperature THW that gives the best fuel economy in the current engine operating state can be obtained. ..

Here, the map shown in FIG. 5 shows a standard state (for example, atmospheric pressure P ₀ = 760 mmHg, intake air temperature T ₀ =).
At 20 ° C. and intake air humidity Hu ₀ = 50%), the cooling water temperature at which the fuel consumption is the best was obtained experimentally using the engine speed Ne and the load Q / Ne as parameters, and was created by plotting this. , ROM in ECU 50
It is stored in 52. As shown in the figure, the temperature of the cooling water that provides the best fuel economy is not always constant, but tends to be higher in the low rotation speed and low load regions and lower in the high rotation speed and high load regions. The value representing the engine load, which is the vertical axis in the figure, is not limited to the value obtained by dividing the intake air amount Q by the engine speed Ne as shown in the diagram, but may be the fuel injection amount Qf calculated in the ECU 50, or Throttle position sensor 47
The throttle valve opening degree θth detected by

In the next step 106, the water temperature sensor 41
Cooling water temperature T at the engine inlet due to
HWs, intake air temperature T at present time by intake air temperature sensor 44
A knocking signal indicating whether or not knocking is currently occurring is read by signals from HA and KCS 48, respectively. Further, in the subsequent step 108, the humidity sensor 45
The humidity (intake humidity) Hu of the intake air at the present time is read by the input signal from. Here, the cooling water temperature THW
Each of s, the intake air temperature THA, the knocking signal, and the intake air Hu are once read in step 102, but are updated in step 106.

At the next step 110, step 1 is performed from the map of the correction value K ₁ for the humidity Hu shown in FIG.
A correction value K ₁ corresponding to the present intake air humidity Hu read at 08 is obtained. The correction value K ₁ is the standard state (intake humidity Hu ₀ = 50 obtained in step 104).
%) Is a correction value for correcting the target value THW ₀ of the cooling water temperature in (%) to the target value for the current intake humidity. The target value THW ₀ in the standard state is added and corrected by the correction value K ₁ . Therefore, in FIG. 6, the correction value K ₁ for the intake humidity Hu ₀ in the standard state is set to 0.
The map shown in FIG. 6 is also obtained in advance by an experiment, like the map shown in FIG.

In the next step 112, the above step 10 is carried out.
Intake air temperature THA (= large
Correction based on the air temperature)
Value K ₁Install a guard on. Figure 7 corresponds to intake air temperature THA
Represents the upper limit guard Kmax and the lower limit guard Kmin
It is a map. Intake air temperature obtained from the intake air temperature sensor 44
Upper and lower limit guards Kmax and Kmin are set by THA.
Correction value K₁Exceeds the upper and lower limit guards Kmax and Kmin
If you get K₁= Kmax or K₁= Kmin
To be done. Therefore, the correction value K₁Is hatched in FIG.
You will be guarded to be within the range shown. Shown in FIG.
The basic idea of the upper and lower limit guards Kmax and Kmin is
Prevent overcorrection, secure minimum water temperature in cold weather, and intense heat
It is to prevent the water temperature from overheating.

Next, at step 114, the final target value THWf of the cooling water temperature THW is calculated by the following equation.

THWf = THW ₀ + K ₁ (1) In the next step 116, it is determined whether or not knocking is occurring at the present time based on the knocking signal read in in step 106. When knocking has not occurred, the routine proceeds to step 118, where the current cooling water temperature THWs read at step 106 is compared with the final target value THWf of the cooling water temperature calculated at step 114. Cooling water temperature TH
When Ws has exceeded the target value THWf, the routine proceeds to step 120, where the three-way flow control valve (also simply referred to as the control valve) 30 is driven in the opening direction from the present opening degree. As the control valve 30 is driven in the opening direction, that is, the opening degree of the control valve 30 increases,
The proportion of the cooling water flowing from the cooling water passage 15b on the lower temperature side to the cooling water pump 13 than the cooling water passage 20 on the higher temperature side increases to lower the cooling water temperature at the engine inlet. Therefore, the detected cooling water temperature THWs is controlled so as to approach the target value THWf.

In step 118, the cooling water temperature T
If HWs is less than the target value THWf, step 1
In step 22, the control valve 30 is driven in the closing direction from the present opening degree. When the control valve 30 is driven in the closing direction, that is, when the opening degree of the control valve 30 decreases, contrary to the above, from the cooling water passage 15b on the low temperature side to the cooling water pump 13 from the cooling water passage 20 on the high temperature side. The proportion of the flowing cooling water increases, which raises the cooling water temperature at the engine inlet. Therefore, also in this case, the detected cooling water temperature THWs is equal to the target value THW.
It is controlled to approach f.

After the process of either step 120 or 122 is performed, the process is returned to step 106 again, and the process of step 106 and subsequent steps is repeatedly executed. As described above, the feedback control of the control valve 30 is performed so that the cooling water temperature THWs becomes the target value THWf by repeatedly executing the processing of steps 118, 120, and 122 described above.

If it is determined in step 116 that knocking has occurred, unconditionally step 12 is performed.
The temperature of the cooling water is lowered to 0 and the temperature of the wall surface of the combustion chamber is lowered to prevent knocking. As described above, in the present embodiment, in order to prevent the knocking by lowering the temperature of the wall surface of the combustion chamber, the above-described KCS 48 is controlled so as not to execute the ignition retard even when the knocking is detected. There is.

As described above, according to the cooling water temperature control routine shown in FIG. 4, the higher the intake humidity Hu, the larger the correction value K ₁ obtained from the map shown in FIG. 6, and the cooling water temperature THWs becomes Feedback control is performed to the higher final target value THWf obtained by the above equation (1). Therefore, the temperature of the cooling water at the engine inlet increases and the cooling capacity decreases. On the contrary, the lower the intake humidity Hu, it is feedback controlled to a lower final target value THWf by (a negative value if it is lower than the intake humidity Hu ₀ in the standard state) correction value K ₁ of small value. Therefore, the cooling water temperature at the engine inlet is lowered and the cooling capacity is increased. Therefore, FIG.
The cooling capacity control means 5 is realized by the cooling water temperature control routine shown in FIG.

Next, the effect of this embodiment will be described.

If only the humidity decreases under the same atmospheric conditions, the proportion of dry air increases and the proportion of moist air decreases. Therefore, the ratio of the air component in the intake air increases, and the combustion speed increases. Since the cooling effect of the latent heat of vaporization of water during intake air decreases, the combustion temperature, that is, the temperature of the combustion chamber wall surface rises. For the above reasons, knocking is likely to occur when the intake air humidity decreases.

In this embodiment, as the intake air humidity Hu is lower as described above, the cooling capacity is increased, so that the temperature of the wall surface of the combustion chamber is lowered, and the occurrence of knocking can be prevented without performing ignition retard. it can. As described above, in this embodiment, the ignition retard is not performed even in a state where knocking occurs, so that the output for the ignition retard is increased as compared with the conventional case. Also, because of this increase in output, the same output can be generated with a smaller amount of fuel than in the past,
Fuel consumption can be reduced. Further, since the maximum combustion temperature can be lowered by lowering the temperature of the wall surface of the combustion chamber, the generation of NOx whose amount increases and decreases according to the maximum combustion temperature is suppressed as compared with the conventional case, and the exhaust emission is improved. Can be made

On the other hand, when the humidity rises, the proportion of dry air decreases and the proportion of moist air increases, so that the burning rate decreases contrary to the above, and at the same time, the cooling effect largely acts and the burning temperature increases. descend. Therefore, when the humidity of the intake air rises, knocking is less likely to occur. Therefore, the higher the humidity of the intake air, the more the knocking is less likely to occur, so that the temperature of the wall surface of the combustion chamber can be increased.

In this embodiment, as the intake humidity Hu is higher as described above, the cooling capacity is lowered, so that the temperature of the wall surface of the combustion chamber rises. Therefore, the friction loss is reduced due to the decrease in the viscosity of the lubricating oil, and the cooling loss in which the combustion energy in the combustion chamber is absorbed by the wall surface is reduced.
The engine output increases. Further, when the temperature of the wall surface of the combustion chamber rises, the combustion speed increases, which also increases the output. And by increasing these outputs,
The fuel consumption can be reduced as in the above.

As described above, according to this embodiment, the cooling water temperature at the engine inlet is controlled to be lower as the intake air humidity is lowered to enhance the cooling capacity, and the cooling water temperature at the engine inlet is increased as the intake air humidity is raised. The engine output can be increased as compared to the conventional case by controlling the controllability to decrease the cooling capacity, thereby reducing the fuel consumption amount. Further, under low humidity conditions, exhaust emission can be improved.

In the above embodiment, the cooling water temperature at the engine inlet is provided by providing the three-way flow control valve 30 as the cooling capacity adjusting means 3 and appropriately mixing the low temperature cooling water and the high temperature cooling water. To change the cooling capacity. However, the present invention is not limited to the configuration of the above-mentioned embodiment, and other methods shown below as an example of the cooling capacity adjusting means 3 are conceivable. For example, a method of adjusting the rotation speed of the radiator fan, a method of changing the passage area of the cooling water in the radiator,
The cooling water temperature at the engine inlet may be changed by various methods such as a method of changing the passage area of the cooling air in the radiator and a method of adjusting the rotation speed of the cooling water pump. And the cooling capacity adjusting means 3
As an example, even in the example in which the above-mentioned configurations are provided,
It is possible to obtain the same effect as that of the above embodiment.

[0037]

As described above, according to the present invention, when the humidity of the intake air where knocking is likely to occur is low, the wall temperature of the combustion chamber is lowered to prevent knocking without retarding the ignition. Therefore, it is possible to increase the output of the internal combustion engine for the ignition retard angle, and also, in the state where the humidity of the intake air in which knocking is unlikely to occur is high, the wall temperature of the combustion chamber rises and friction loss is reduced. Since the cooling loss is reduced and the combustion speed is improved, the output of the internal combustion engine can be increased. The fuel consumption can be reduced by increasing the output. Also,
In the state where the humidity of the intake air is low, the wall temperature of the combustion chamber is lowered and the NOx emission amount is suppressed, so that the exhaust emission can be improved.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is a system configuration diagram of an embodiment of an internal combustion engine (engine) and peripheral devices to which the present invention is applied.

FIG. 3 is an engine control unit (EC
It is a figure which shows the specific structural element of U).

FIG. 4 is a flowchart of a cooling water temperature control routine which constitutes a main part of an embodiment of the device of the present invention.

FIG. 5 is a diagram showing a map for obtaining a cooling water temperature at which fuel consumption is best with the engine speed and load as parameters.

FIG. 6 is a diagram showing a map of a correction value K ₁ with respect to a humidity Hu of intake air.

FIG. 7: Upper limit guard Kmax corresponding to intake air temperature THA
It is a figure showing the map of the lower limit guard Kmin.

[Explanation of symbols]

 1 Internal Combustion Engine 2 Cooling System 3 Cooling Capacity Adjusting Means 4,45 Humidity Sensor 5 Cooling Capacity Controlling Means 11 Engine Main Body 12 Radiator 13 Cooling Water Pump 14, 15a, 15b, 20, 32, 35 Cooling Water Passage 30 3-way Flow Control Valve 41 Water Temperature Sensor 48 Knock Control System (KCS) 50 Engine Control Unit (ECU) 51 Central Processing Unit (CPU)

Claims (1)

[Claims] 1. A cooling capacity adjusting means for changing the cooling capacity of a cooling system of an internal combustion engine, a humidity sensor for detecting the humidity of intake air, and an output signal of the humidity sensor to input the humidity of the intake air. A cooling control device for an internal combustion engine, comprising: cooling capacity control means for controlling the cooling capacity adjusting means so that the cooling capacity is increased as the temperature is lowered.