JPS6318012B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the idle rotation speed of an engine that drives an automobile or the like.

Conventionally, in order to control the idle rotation speed of an automobile engine to a designed target value in a maintenance-free manner, an analog computer was used to find the deviation between the actual engine idle rotation speed and the target value, and this deviation was calculated using an analog computer. A closed-loop control method has been proposed that controls the intake air amount or air-fuel mixture supply amount of the engine according to the following.

However, in the above control method, the computer calculates the target value using only the engine cooling water temperature as a parameter, and one target value is determined for the same engine temperature condition and control is performed. If the engine temperature is the same, even if the engine is started immediately, even if it is started at a lower temperature and reaches that temperature after a certain period of time, the engine speed will be controlled to the same speed. It was difficult to satisfy the three elements of shortening warm-up time, reducing fuel consumption, and improving drivability.

This invention was made in view of the above points,
It is an object of the present invention to provide an engine rotation speed control method that can satisfy the above three elements.

In particular, in this invention, the target value is set according to the warm-up state of the engine, and the target value is set higher than the value set according to the warm-up state of the engine until a predetermined period of time has elapsed from the start of the engine. The present invention is characterized by a control method that changes the value to a certain value, thereby solving the above problem.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An apparatus for carrying out the control method according to the present invention will be described below with reference to embodiments shown in the drawings.

In FIG. 1, an engine 10 is a known four-cycle spark ignition engine that drives an automobile, including an air cleaner 11, an air flow meter 12, and an intake pipe 1.
3. Main air is taken in through the surge tank and each intake branch pipe 14, and fuel, such as gasoline, is injected and supplied from an electromagnetic fuel injection valve 15 provided in the intake branch pipe 14.

The main intake air amount of the engine 10 is adjusted by a throttle valve 16 that is arbitrarily operated, while the fuel injection amount is adjusted by a fuel control unit 20 that constitutes a computer. The fuel control unit 20 is a known unit that determines the fuel injection amount using the engine rotational speed measured by an electromagnetic pickup 21 serving as a rotational speed sensor and the intake air amount measured by the airflow meter 12 as basic parameters. In addition, signals are input from the warm-up sensor 22, etc., and the fuel injection amount is increased or decreased based on these signals.

The air conduits 18, 19 are provided so as to bypass the throttle valve 16, and an air control valve 30 is provided between the two conduits 18, 19. Further, one end of the conduit 18 is connected to an air inlet provided between the throttle valve 16 and the air flow meter 12, and one end of the conduit 19 is connected to an air outlet provided downstream of the throttle valve 16. ing.

The air control valve 30 is basically a diaphragm type control valve, and transmits the displacement of a diaphragm 33 whose outer periphery is wound between housings 31 and 32 to a valve body 35 via a shaft 34, 36 is of the type that opens and closes. diaphragm 33
is displaced by the pressure difference between the chambers 37 and 38, and is biased by a compression coil spring 40 via a spring receiver, thereby applying a valve closing force to the valve body 35.

A diaphragm 33 is provided between the housings 31 and 32.
A holding plate 41 is secured together with the holding plate 41 by tightening, and the shaft 34 is guided in an airtight manner by a sleeve provided on the holding plate 41.

Further, a small hole is formed in the holding plate 41, and the atmosphere is introduced into the chamber 37 through this small hole.

Note that the valve body 35 is a needle valve, and the valve seat 3
6 is continuously changed with respect to the amount of displacement of the shaft 34.

Furthermore, the air control valve 30 includes an electromagnetic mechanism 50 that indirectly changes the opening degree of the valve body 35.
This electromagnetic mechanism 50 includes an electromagnetic coil 5 wound around a synthetic resin bobbin and fixed to a housing 31.
1, a fixed iron core 52 disposed at the center of the electromagnetic coil 51, a plate spring 53 made of a magnetic material and fixed to the housing 31 with a pin, and a plate spring 53 facing the valve body 54 at the tip of the plate spring 53. provided tube 55,
It is composed of 56. And leaf spring 53
When the electromagnetic coil 51 is not energized, the tube 56 is closed by its own spring force, and when the electromagnetic coil 51 is energized, the tube 55 is closed by electromagnetic force. here,
Pipe 55 is open to the atmosphere via an air filter to introduce atmospheric pressure into chamber 38, while pipe 56
is connected to a surge tank via a pipe 57 for conducting negative intake pressure to the chamber 38.

Therefore, the electromagnetic coil 51 of this electromagnetic mechanism 50
The pressure inside the chamber 38 changes depending on the duty ratio of the pulse signal applied to the valve body 35, and the opening degree of the valve body 35 changes.

Excitation of the electromagnetic mechanism 50 is controlled by an air control unit 60 that constitutes a computer. This air control unit 60 includes an electromagnetic pickup 2
1. It is connected to a warm-up sensor 22, an air conditioning switch 23, and a starter switch 24, from which various signals are input.

Here, the electromagnetic pickup 21 is connected to the engine 10.
Ring gear 25 rotates in synchronization with the crankshaft of
It outputs a pulse signal with a frequency proportional to the engine rotation speed. Further, the warm-up sensor 22 is composed of a temperature sensing element such as a thermistor and detects, for example, the cooling water temperature, which is representative of the engine temperature.

Further, when the air conditioning switch 23 is turned on, the electromagnetic clutch 27 becomes connected, and the air conditioner compressor 28 is connected as a load of the engine 10.

The starter switch 24 is connected to the starting electric motor 26 of the engine 10, and is turned on when the key switch of the automobile is placed in the start position.

Next, the air control unit 60 of the computer will be explained in detail with reference to FIG. Digital/
The analog (D/A) conversion circuit 100 receives a pulse signal of a frequency corresponding to the engine speed from the electromagnetic pickup 21. 3. After being waveform-shaped into the waveform shown in FIG. 1, it is output from terminal A. Then, this signal is transferred to capacitors 107, 1
11, diodes 109, 110, and resistor 105 convert the voltage proportional to the actual engine rotation speed and the sawtooth voltage synchronized with the engine rotation into the voltage shown in FIG. Output from terminal B.

The function voltage generation circuit 200 receives the output signal of the warm-up sensor 22, the on/off signal of the air conditioning switch 23, and the on/off signal of the starter switch 24. Among these, the output of the warm-up sensor 22 is amplified by a known amplification circuit 201 and becomes a voltage signal corresponding to the engine water temperature. This voltage signal is resistor 20
2. Through the diode 203, the on/off signal from the air conditioning switch 23 is outputted to the comparison circuit 300 through the resistor 204 and the diode 205, and provides a comparison level VD of the comparison circuit 300.

Diode 207, capacitor 209, resistor 2
08, 210, 211 and an operational amplifier 206 constitute a timer circuit, the signal from the starter switch 24 is input to this timer circuit, and the output of the timer circuit is added to the comparator circuit 300 via a resistor 212 and a diode 213. is used to change the comparison level VD.

In other words, this function voltage generation circuit 200 is for changing the comparison level VD representing the target value of the idle rotation speed, and its output characteristics are as shown in FIG.
When T increases, the comparison level VD is lowered, and when the air conditioning switch 23 is off, the comparison level VD is changed to a low level as shown by the solid line, and when the air conditioning switch 23 is on, it is changed to a high level as shown by the broken line. to change the comparison level VD.

Further, when the starter switch 24 is turned on for a certain period of time, the terminal K is at the 1 level during that period, and when the switch 24 is turned off, it goes to the 0 level, resulting in a waveform as shown in FIG. 4. As a result, the voltage waveform at terminal L becomes the discharge waveform shown in FIG.
voltage is applied to resistors 210 and 21 as shown in FIG.
When the voltage at terminal L decreases to the voltage Vo determined by 1, the voltage gradually decreases. Therefore _, the comparison level VD changes with respect to the elapsed time as shown in _FIG . It will reach a certain level.

Comparison circuit 300 consists of resistors 301 to 303 and comparator 304, and is determined by the output voltage of D/A conversion circuit 100 representing the actual idle rotation speed and the output voltage of function voltage generation circuit 200 representing the target value. It compares the comparison level VD, calculates the deviation △N (=N-Nref) between the actual idle rotation speed N and the target value Nref, and outputs a signal according to the deviation △N.

The comparison circuit 300 includes the D/A conversion circuit 1
Only during the period in which the output voltage of 00 is lower than the comparison level VD, the signal C which becomes O level as shown in FIG. 3 is output.

The integrating circuit 400 charges or discharges a capacitor 401 at a constant current according to the output signal C of the comparing circuit 300, and outputs an integrated voltage E as a control amount from the deviation ΔN. This integrating circuit 400 includes resistors 402 to 404 and a transistor 409 as a constant current charging circuit that operates when the signal C is at the 0 level, resistors 405 to 407 as a constant current discharging circuit that operates when the signal C operates at the 1 level, a diode 408, A transistor 410 is provided. As shown by the broken line in FIG. 3, this integrating circuit 400 is configured such that while the output signal C of the comparator circuit 300 is at 0 level, the capacitor 401 is charged with a constant current, so the output voltage E increases, and the output signal is at the 1 level. At this time, the capacitor 401 is discharged at a constant current, and the output voltage E is reduced.

The pulse modulation circuit 600 includes a resistor 601, a comparator 602, and an oscillator 603, and outputs a pulse signal with a duty ratio corresponding to a voltage E representing a control amount. Of these, the oscillator 603 is a known one that outputs a triangular wave voltage F with a constant period, as shown by the solid line in FIG. 3.

The comparator 602 outputs the output voltage E of the integrating circuit 400.
and the triangular wave voltage F of the oscillator 601 are input, and by comparing both voltages, the integrating circuit 40
It outputs a pulse signal G that is at 1 level only during a period in which the output voltage E at 0 is greater.

The amplifier circuit 700 is based on this pulse modulation circuit 600.
A power transistor 70 that inverts and amplifies the signal G of
The output after amplification is supplied to the electromagnetic coil 51 of the electromagnetic mechanism 50.

The voltage limiting circuit 800 includes resistors 801 to 805,
It is composed of diodes 806 and 807, and limits the output voltage of the terminal E of the integrating circuit 400 within a control range between the upper limit voltage Vmax of the terminal H and the lower limit voltage Vmin of the terminal J.

Since the resistor 804 of the limiting circuit 800 is connected to the output of the amplifier circuit 201 that outputs a voltage signal according to the engine temperature of the functional voltage generating circuit 200, the upper limit voltage Vmax and the lower limit voltage min are determined by each resistor 80.
If the values of 1,802,803 are appropriately selected, characteristics dependent on the engine temperature T can be obtained as shown in FIG.

Further, the resistor 805 is connected to the function voltage generation circuit 200.
is connected to the I terminal of the timer circuit, and until time _t0 has elapsed after the engine has started, the upper limit voltage Vmax and lower limit voltage Vmin are raised by a certain level and are higher due to the voltage at terminal I shown in FIG. Changes in level, then upper, lower limit voltage
VmaxVmin varies at normal levels.

With this configuration, the integrating circuit 400
When the potential of the capacitor 401 increases and exceeds the upper limit voltage Vmax, the diode 806 becomes conductive.
In the end, the potential of the capacitor 401 cannot rise above the upper limit voltage Vmax, and conversely, even if the potential falls, it cannot be lowered below the lower limit transmission voltage Vmin.
Therefore, the voltage amplitude of capacitor 401 can be limited.

Next, the operation of the above configuration will be explained. When the throttle valve 16 is closed and the engine 10 is in idle operation, the idle rotational speed is a function of the voltage generation circuit 20 of the air control unit 60.
0, the output of the D/A conversion circuit 100 also decreases with respect to the comparison level VD.

Therefore, the output of the D/A conversion circuit 100 is always lower than the comparison level VD, or even if it becomes higher, it is only for a short time. Therefore, the output signal of the comparison circuit 300 indicating the rotational speed deviation △N is the deviation △ Depending on N, the pulse signal is always at 0 level or has a small duty ratio. As a result, the output voltage E of the integrating circuit 400, which indicates the control amount, increases.

Therefore, in the pulse modulation circuit 600, the oscillator 6
The period t during which the integrated voltage E becomes larger than the triangular wave voltage F in 03 (the period during which the comparator 602 is at the 1 level) increases, the duty ratio increases, and the electromagnetic mechanism 5
The proportion of time that the zero electromagnetic coil 51 is energized increases, the opening degree of the air control valve 30 increases, the amount of auxiliary air that bypasses the throttle valve 16 increases, and the idle speed of the engine 10 increases.

On the other hand, when the idle rotation speed is equal to or higher than the target value (set rotation speed), the output of the D/A conversion circuit 100 is always higher than the comparison level VD that gives the target value, or even if it is lower, it is only for a short time. The output signal of the circuit 300 is always 1 level or a pulse signal with a large duty ratio. As a result, the output voltage E of the integrating circuit 400 decreases.

Therefore, in the pulse modulation circuit 600, the oscillator 60
A period t during which the integrated voltage E is larger than the triangular wave voltage F of No. 3 (that is, a period during which the comparator 602 is at the 1 level)
decreases, and the proportion of time during which the electromagnetic coil 51 of the electromagnetic mechanism 50 of the air control valve 30 is energized decreases, which means that the opening degree of the air control valve 30 decreases, and the amount of auxiliary air that bypasses the throttle valve 16 decreases. and decrease the idle rotational speed of the engine 10.

In this way, the engine rotational speed is controlled by the air control unit 60 to a target value (set rotational speed) corresponding to the comparison level VD, which determines the output of the function voltage generation circuit 200, when the throttle valve 16 is closed and the engine is idling. .

However, the comparison level VD that determines the target value of the lever
depends on the output of the warm-up sensor 22, and increases as the engine temperature decreases, as shown by the solid line in FIG.
During warm-up operation, the rotational speed can be increased according to the engine temperature, so stable idling operation can be maintained.

Also, after starting the engine, the time from several seconds to several minutes
Since the comparison level VD representing the target value is raised by the timer circuit until to has elapsed, the idle speed is maintained at a high level immediately after starting, regardless of the engine temperature, and the engine warm-up time is shortened.

In other words, even if the engine temperature is the same, if the engine is just started, the idle speed will be maintained higher than if it was started at a lower temperature and reached that temperature after a certain period of time, which has the effect of shortening warm-up time. Great effects can also be obtained in terms of reducing fuel consumption and improving drivability.

Furthermore, when the compressor 28 for the automobile cooler or air conditioner is connected to the engine 10 and driven, the ON signal of the air conditioning switch 23 is input to the function voltage generating circuit 200.
0 indicates the comparison level as shown by the dashed line in Figure 5.
The target value for raising the VD can be switched to a higher value, thus eliminating problems such as impairing the cooling capacity of the vehicle or causing engine stalls.

Further, for example, when the engine temperature rises and warm-up is completed, the load such as the viscous resistance of the engine oil becomes small, so the amount of auxiliary air may be small. When such warm-up is completed, the throttle valve 16 is closed and the air control unit 60 is closed even when the vehicle is stopped by releasing the accelerator pedal and depressing the brake pedal to decelerate and stop the vehicle. Performs closed-loop control of rotation speed. Therefore, if the brake operation is performed until the rotational speed becomes lower than the target value determined by the voltage generating circuit 200, the integrating circuit 400
Since the output of the engine continues to rise, that is, the opening degree of the air control valve 30 increases, and the amount of auxiliary air increases all at once, there is a possibility that the engine rotation speed becomes abnormally high, albeit temporarily.

However, the output of the integrating circuit 400 is limited to the upper limit voltage Vmax by the voltage limiting circuit 800, and the amount of auxiliary air does not increase beyond the amount determined by the upper limit voltage Vmax, thereby preventing an abnormal increase in engine speed.

Also, the voltage limiting circuit 800 causes the integrating circuit 40 to
0 output is limited to within the upper and lower limits, so even if a problem occurs with the rotation speed signal from the rotation speed sensor, at least the rotation speed at idle will remain within the upper and lower limits depending on the engine temperature. It can be controlled within the control range corresponding to the voltage within.

In the above embodiment, a wired logic type analog computer is used as the computer, but a stored program type microcomputer may be used for control.

In this case, the computer 60 is composed of an input interface 61, a microcomputer 62, an output interface 63, and drive circuits 64, 65 as shown in FIG.
It is sufficient to cause a time interrupt every 20 msec and execute an interrupt routine as shown in FIG.

In FIG. 9, this interrupt routine starts at step 70, and at step 71 output signals from each sensor and switches 21 to 24 are input.
In step 72, it is determined whether the starter switch 24 is on, and if it is on, a target value Nref (rpm) is calculated in step 73. This target value Nref is
As shown in FIG. 8, it is determined by a function f(T) of the cooling water temperature T, and this f(T) is stored in the memory as f(T)st in step 74.

If the starter switch 24 is off in step 72, it is determined in step 75 whether the cooling water temperature T is 60°C or higher, and if not, in step 76 the starter switch 24 is turned off by the timer built in the microcomputer 62. Determine whether it has been within 5 minutes since it was turned off. If the time is within 5 minutes, in step 77 the target value Nref is set to f(T)st stored in the memory.

If the water temperature T is 60°C or higher in step 75, or if 5 minutes have passed since the starter switch 24 was turned off in step 76, the previously calculated target value N'ref is changed to the function value f(T) in step 78. Determine whether it is larger than the
Set the target value Nref to (N'ref - 2 (rpm)).

If N'ref is smaller than the function value f(T) in step 78, the target value Nref is changed to the function value f(T) in step 80.
(T).

When the target value Nref is set as above,
In step 81, a deviation ΔN is calculated from the actual idle rotation speed and the target value ΔN based on the following equation.

ΔN=N−Nref Next, in step 82, a value representing the duty ratio based on the deviation ΔN is read from a map stored in advance in a ROM (read-only memory) and used as the control amount. Then, the control amount is set within a control range between the upper limit value and the lower limit value, and the control amount is output to the output interface 63 in step 83.

Then, in step 84, the process returns to the main routine. The control amount indicating the duty ratio calculated by the microcomputer 62 in this way is
The pulse signal is output to the output interface 63, thereby converted into a pulse signal having the duty ratio, and output to the electromagnetic valve 51 via the drive circuit 65.

Thus, it performs control similar to that of the wired logic computer described above.

In addition, in the above-mentioned embodiment, the air control valve 30
The amount of auxiliary air that bypasses the throttle valve 16 is controlled by, for example, the opening degree of the throttle valve 16 instead of the valve body 35 by the displacement of the shaft 34 of the air control valve 30. It is thus also possible to control the amount of air or mixture during idle operation.

Further, in the above embodiment, an air control valve of a type in which a diaphragm valve is actuated by the electromagnetic mechanism 50 is used, but an electromagnetic air control valve in which a valve body is actuated directly by the electromagnetic force of the electromagnetic mechanism 50 may be used.

Further, although a cooling water temperature sensor is used as the warm-up sensor, an engine oil temperature sensor, block temperature sensor, etc. may also be used.

Furthermore, although the warm-up state of the engine and the connection state of the compressor are used as elements of the functional voltage, the functional voltage may be generated based on other engine operating states.

Further, in the above embodiment, during normal operation other than idling operation in which the throttle valve 16 is opened, it is possible to additionally provide a circuit for maintaining the output voltage of the integrating circuit 400 at a predetermined value depending on the engine temperature. This makes it possible to supply a predetermined amount of auxiliary air depending on the engine temperature during normal operation.

As described above, according to the present invention, the target value of the idle rotation speed of the engine is calculated, the actual idle rotation speed of the engine is determined,
The deviation between this actual idle rotation speed and the target value is calculated, a control amount is calculated according to this deviation, and the engine rotation speed is controlled based on this control amount to control the intake air or mixture supply amount to the engine. In the control method, the target value is set according to the warm-up state of the engine, and the target value is set to be lower than the value set according to the warm-up state of the engine until a predetermined period of time has elapsed from the start of the engine. Since the engine speed control method is characterized by changing the rotational speed to a higher value, even if the engine temperature is the same, immediately after starting the engine, the increased target value will cause The engine warm-up time can be shortened because the idle speed is higher than if the engine was started at a temperature lower than the engine temperature at that time and reached this temperature after a certain period of time. Furthermore, since warming up can be completed in a short time, it is possible to reduce fuel consumption and to improve drivability, which is an excellent effect.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a system to which the method of the present invention is applied, FIG. 2 is an electric circuit diagram showing the air control unit shown in FIG. 1, and FIGS.
2 is a signal waveform diagram of each part, FIGS. 5 and 6 are graphs for explaining the operation, FIG. 7 is a block diagram showing another embodiment of the computer, and FIG. 8 is a graph for explaining the operation. FIG. 9 is a flowchart for explaining the operation. 10...Engine, 16...Throttle valve, 2
1...Electromagnetic pickup, 22...Warm-up sensor,
24... Starter switch, 30... Air control valve, 50... Electromagnetic mechanism, 62... Microcomputer, 100... A-D conversion circuit, 200...
Functional voltage generation circuit, 300... Comparison circuit, 400
...Integrator circuit, 600...Pulse modulation circuit.

Claims (1)

[Claims] 1. Calculate the target value of the idle rotation speed of the engine, obtain the actual idle rotation speed of the engine,
The deviation between this actual idle rotation speed and the target value is calculated, a control amount is calculated according to this deviation, and the engine rotation speed is controlled based on this control amount to control the intake air or mixture supply amount to the engine. In the control method, the target value is set according to the warm-up state of the engine, and the target value is set to be lower than the value set according to the warm-up state of the engine until a predetermined period of time has elapsed from the start of the engine. A method for controlling an engine rotation speed, characterized by changing the rotation speed to a higher value.