JPH0623549B2 - Internal combustion engine speed control device - Google Patents

Description

The present invention relates to a rotation speed control device for an internal combustion engine, and more particularly to a rotation speed of an internal combustion engine provided with an intake air amount control means for increasing an intake air amount when a speed reduction rate is equal to or higher than a predetermined value. Regarding the control device.

In recent years, internal combustion engines tend to be lighter in weight and have a lower idle speed in order to reduce fuel consumption.
Therefore, when idling, turn on the high beam,
In an engine equipped with an electric fan or automatic transmission, even if a slight load is applied by operating the shift lever, the engine speed will drop and the engine speed will become unstable during idling. There is. In addition, when deposits adhere to the throttle valve due to changes over time, the engine speed gradually decreases and the engine speed becomes unstable during idling.

For this reason, a bypass is provided so as to bypass the throttle valve so that the throttle valve is fully closed and the vehicle speed is a predetermined value (for example, 0
When the engine speed is less than 2.5 Km / h), that is, when the engine is idling, a method is known in which the amount of air flowing through the bypass is controlled to control the engine speed to a target speed by feedback control. An idle speed control valve (ISC valve), which controls the opening amount by a step motor or solenoid to control the amount of air flowing to the bypass route, is attached to this bypass route. By controlling the opening amount of this ISC valve, The feed back control is performed so that the engine speed is close to the target speed determined according to the engine load and the shift position. When the feed back control is not performed, the ISC valve is held at a predetermined opening.

Further, particularly in a lightweight internal combustion engine, the inertia is small, and the engine speed may undershoot and reach a stall when shifting from racing to an idling state or when decelerating and shifting to an idling state. In order to prevent this undershoot, etc., I
Using the SC valve, when the amount of decrease in engine speed is greater than or equal to a predetermined value, that is, when the speed of decrease in engine speed is less than or equal to a negative predetermined value, the ISC valve is opened by a predetermined amount to increase the air amount,
It is possible to prevent undershoot.

However, if the above control is performed when the engine speed drops from high speed, the air amount is increased before the undershoot occurs, and the engine speed bounces or stalls.
The problem occurs.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an engine speed control device for an internal combustion engine that can smoothly lower the engine speed.

In an engine speed control device for an internal combustion engine equipped with an intake air amount control means for increasing the intake air amount when the engine speed lowering speed is equal to or higher than a predetermined value, when the engine speed is higher than a target speed higher than a target speed. The configuration is such that it has a regulating means for regulating the operation of the intake air amount control means.

According to the above configuration of the present invention, when the engine speed is equal to or lower than the predetermined value, that is, when the decrease amount of the engine speed is equal to or higher than the predetermined value in the region where undershoot is likely to occur, the air amount is increased, so that bounce or the like occurs. The effect that the rotation speed can be smoothly lowered without doing so is obtained.

Next, an example of an internal combustion engine (engine) to which the present invention is applied will be described with reference to FIG. This engine has an automatic transmission, is controlled by an electronic control circuit such as a micro computer, and has an air flow meter 2 for detecting the intake air amount downstream of an air cleaner (not shown). . The air flow meter 2 is
The compensating plate rotatably provided in the damping chamber, the measuring plate connected to the compensating plate, and the potentiometer 4 for detecting the opening of the compensating plate are provided. Therefore, the intake air amount is obtained from the intake air amount signal output from the potentiometer as a voltage value. An intake air temperature sensor 6 that detects the intake air temperature and outputs an intake air temperature signal is provided near the air flow meter 2.

A throttle valve 8 is arranged on the downstream side of the air flow meter 2, and an idle switch 10 that is turned on when the throttle valve 8 is fully closed (idle position) is attached to the throttle valve 8, and a surge tank 12 is provided on the downstream side of the throttle valve 8.
Is provided. Further, a bypass 14 is provided so as to bypass the throttle valve 8 and connect the surge tongue 12 on the upstream side of the throttle valve and the surge tongue 12 on the downstream side of the throttle valve. An ISC valve 16 whose opening is adjusted by controlling an exciting current of a solenoid is attached to the bypass 14. The surge tank 12 is connected to the engine 2 via the intake manifold 18 and the intake port 22.
It is connected to the No. 0 combustion chamber. A fuel injection valve 24 is attached to each cylinder so as to project into the intake manifold 18.

The combustion chamber of the engine 20 is connected via an exhaust port 26 and an exhaust manifold 28 to a catalytic converter (not shown) filled with a three-way catalyst. An O ₂ sensor 30 that detects the residual oxygen concentration in the exhaust gas and outputs an air-fuel ratio signal is attached to the exhaust manifold 28. An engine cooling water temperature sensor 34 is attached to the engine block 32 so as to penetrate the block 32 and project into the water jacket. The cooling water temperature sensor 34 detects the engine cooling water temperature and outputs a water temperature signal.

A spark plug 38 is attached to each cylinder so as to penetrate the cylinder head 36 of the engine 20 and project into the combustion chamber. The ignition plug 38 is connected via a distributor 40 and an igniter 42 to an electronic control circuit 44 composed of a microcomputer or the like. Inside the distributor 40, a cylinder discrimination sensor 46 and a crank angle sensor 48, each of which is composed of a signal rotor fixed to the distributor shaft and a pick-up fixed to the distributor housing, are mounted. In the case of a 6-cylinder engine, the cylinder discrimination sensor 46 outputs a cylinder discrimination signal every 720 ° CA, and the crank angle sensor 48 outputs an engine speed signal every 30 ° CA.

The electronic control circuit 44 also includes a key switch 50, a neutral start switch 52, an air conditioner switch 54,
The vehicle speed sensor 56 and the battery 58 are connected.
The key switch 50 outputs a starter signal when the engine is started, the neutral start switch 52 outputs a neutral signal only when the transmission is in the neutral position, and the air conditioner switch 54 outputs an air conditioner signal when the air conditioner compressor is operating. . The vehicle speed sensor 56 is composed of a magnet fixed to the speedometer cable, a reed switch and a magnetic sensitive element.
The vehicle speed signal is output according to the rotation of the speedometer cable.

The electronic control circuit 44 includes a central processing unit (CPU) 60 and a read only memory (ROM) 6 as shown in FIG.
2, random access memory (RAM) 64, Batsukuatsupuramu _(B u -RAM) 66, input and output port 6
8, an analog digital converter (ADC) 70, and a bus such as a data bus or a control bus connecting these components. A vehicle speed signal, a cylinder discrimination signal, an engine speed signal, a throttle fully closed signal from the idle switch 10, an air-fuel ratio signal, a starter signal, a neutral signal and an air conditioner signal are input to the input / output port 68. Further, the input / output port 68 outputs an ISC valve control signal for controlling the opening of the ISC valve, a fuel injection signal for opening / closing the fuel injection valve, and an ignition signal for turning on / off the igniter to the drive circuit, The drive circuit controls the ISC valve, the fuel injection valve and the igniter according to these signals. Further, an intake air amount signal, an intake air temperature signal, a battery voltage and a water temperature signal are input to the ADC 70, and the ADC sequentially converts these signals into digital signals according to an instruction from the CPU. In the ROM 62, the target cooling speed determined according to the engine cooling water temperature, the intake air temperature, the load state, the shift lever range position, etc., the data for the expected amount for performing the feedforward control when a load is applied, Data for increasing the amount of air during transition and other control programs are stored in advance.

Next, an embodiment in which the present invention is applied to the above engine will be described in detail. The case of controlling the duty ratio of the ISC valve will be described below.

FIG. 3 shows the middle of the main routine according to the present invention. In step 100, the engine operating state is judged based on the air conditioner signal, the neutral signal, etc., and the target rotational speed NF according to this operating state and this operating state are determined. The estimated duty ratio De corresponding to the estimated air amount according to the state is set in a predetermined area of the RAM. The estimated duty ratio De is for feedforward control of the ISC valve when a load is applied.
In the next step 102, it is determined whether or not the idle speed control (ISC) timing has come by determining, for example, every 120 ° CA. IS
If the C timing is reached, the average value of the engine speed is calculated based on the engine speed signal in step 104.
▼ is calculated, and it is determined in step 106 whether or not the feed back control condition is satisfied. The feed back control conditions are, for example, that the throttle valve is fully closed, the vehicle speed is a predetermined value (for example, 2.5 km / h) or less, and the engine cooling water temperature is a predetermined temperature (for example, 70 ° C. or more).

When the feedback control condition is satisfied, the basic duty ratio Do for controlling the feedback control of the average value of the engine speed to the target rotation speed is calculated in step 110, and the feedback value is adjusted when the load is applied. The expected duty ratio De for controlling is added to the basic duty ratio Do to obtain the control duty ratio D.

In the next step 112, it is judged whether or not the learning control condition is satisfied. If the learning control condition is satisfied, the learning control is performed in step 114, and then the control duty ratio D is registered as the output duty ratio Dout in step 116. To set. An example of this learning control is as follows. Part 1
One is elapsed after fed back control a predetermined time, the engine rotational speed average value ▲ ▼ the target rotational speed NF ± predetermined value (e.g., 25R.Pm) output duty ratio Dout and B _u -RAM when are entering a port in This is a method of gradually increasing or decreasing the learning value to bring the learning value close to Dout when the deviation from the learning value stored in is greater than or equal to a predetermined value. The other one is a method in which the average value ▲ ▼ of the engine speed and the target speed are always compared, and the learning value is increased or decreased so as to bring the learning value closer to Dout based on the magnitude relationship.

When it is determined in step 106 that the feed back control condition is not satisfied, in step 108, the control duty ratio D is set to the duty ratio or the learning value at the end of the feed back control to perform the ISC open loop control. In step 116, the control duty ratio D is set as the output duty ratio Dout.

FIG. 4 shows an interrupt routine executed every predetermined time (for example, 4 msec) for controlling the ISC valve. Step 118 outputs an ISC valve control signal to excite the solenoid of the ISC valve, step 120 calculates the ISC valve off time for demagnetizing the solenoid from the output duty ratio Dout, and next step 122 compares the off time with the compare register. To set. As a result, the solenoid of the ISC valve is demagnetized at the off time.

As described above, when the feedback control condition is satisfied, the basic duty ratio Do is changed so that the average value of the engine speed becomes the target speed, and when the estimated duty ratio De is present, the estimated duty ratio De is calculated. The opening of the ISC valve is controlled by the value obtained by adding. During open loop control, the control duty ratio D becomes a predetermined value, so the ISC valve opening is kept constant.

FIG. 5 shows an increased duty ratio D for further opening the ISC valve in order to prevent the engine speed from undershooting.
₉ shows a routine for calculating _N. First,
In step 124, it is determined whether or not the idle switch is turned on, and if it is turned on, in step 126 the engine speed NE is a predetermined value (for example, 1000 to 1500 r.p.
m) or less, and if it is less than a predetermined value, step 1
At 28, the change rate ΔNE of the engine speed is calculated. At the next step 130, the engine speed change rate .DELTA.NE is a predetermined negative value (for example, -50 to -900 rpm./0.1).
s) whether the determined below, below a predetermined value, i.e., amount of drop in the engine speed is set to a predetermined value the increased duty ratio D _N at step 132 if more than a predetermined value. This predetermined value is given as a constant value or a function whose absolute value increases with the increase of the engine speed with the engine speed as a parameter, and the optimum value is determined by experiments for various engines. On the other hand, when the idle switch is off,
If the engine speed exceeds a predetermined value or the rate of change of the engine speed exceeds a predetermined value, step 134
The attenuation processing of the duty ratio D _N is performed. As the method of this attenuation processing, there are a method of subtracting a predetermined value at every predetermined time, a method of subtracting a predetermined value at every predetermined engine speed, and the like. The predetermined value is a constant value, and decreases as the engine speed increases. And a value that increases as the engine cooling water temperature increases.

In the next step 136, the control duty ratio D obtained in steps 110 and 108 (mainly because the idle switch is on in this embodiment, step 110
A value) to a value obtained by adding the increased duty ratio D _N and the output duty ratio Dout. As a result, the ISC valve is controlled in the routine of FIG. Steps 128, 130, 132, 134, 136 of the above routine and ISC
The valve corresponds to the intake air amount control means in the claims,
126 corresponds to the regulation means.

FIG. 6 shows a change in engine speed and a change in ISC valve opening when controlled as described above, in comparison with a conventional example. Broken lines L ₂ and L ₃ show the conventional example, and a solid line L ₁ shows the present embodiment.

When the idle switch is switched from off to on, the engine speed drops and the rate of change of engine speed also increases in the negative direction.

In the conventional example indicated by the broken line L ₂ , regardless of whether the engine speed is high or low, if the rate of change of the engine speed falls below a predetermined negative value, I
Since the SC valve opening is increased and the intake air amount of the engine is increased, the change in the engine speed is bound.

In the conventional example of the dashed line L _3, regardless of the level of the rate of change of engine speed, since the increased duty ratio D _N is not used, the change in engine speed is generating undershoot the target idling speed .

On the other hand, in the present embodiment indicated by the solid line L ₁ , even if the rate of change of the engine speed is lower than the negative predetermined value, the ISC valve opening degree is maintained when the engine speed is equal to or higher than the predetermined idling target speed. Since the increase in the engine speed is regulated, there is no bound in the change in engine speed.

Further, when the engine speed is equal to or lower than a predetermined speed higher than the idling target speed, the increase in the ISC valve opening is not regulated and the intake air amount of the engine is increased. No undershoot for numbers.

As a result, the engine speed smoothly drops to the target speed.

Incidentally, an example has been described in which the idle Sui Tutsi in the above is set to a predetermined value the increased duty ratio D _N on, Datsushiyupotsuto is provided Surotsutoru valve closing until the idle position is temporarily delayed in Surotsutorureba ,
Since the throttle valve may be slightly opened even when the foot is away from the accelerator pedal, the determination at step 124 may be omitted. Further, according to the present invention, an engine equipped with an ISC valve with a step motor that controls the opening of the valve by the number of pulses instead of the duty ratio, an engine equipped with a manual transmission, and an air flow meter in place of the throttle valve downstream side. It can also be applied to an engine or the like equipped with a pressure sensor that detects the intake pipe pressure.

[Brief description of drawings]

1 is a schematic diagram showing an example of an engine to which the present invention is applied, FIG. 2 is a block diagram showing the electronic control circuit of FIG. 1,
FIG. 3 is a flow chart showing a main routine according to the embodiment of the present invention, FIG. 4 is a flow chart showing a 4 msec interrupt routine according to the embodiment of the present invention, and FIG. 5 is an interrupt routine at every predetermined time of the present invention. The flow chart, FIG. 6, is a diagram showing changes in engine speed, ISC valve opening, and the like. 14 ... detour, 44 ... electronic control circuit, 16 ... IS
C valve, 52 ... Neutral start switch.

Claims (1)

[Claims] 1. A rotation speed control device for an internal combustion engine, comprising: an intake air amount control means for increasing an intake air amount when a reduction speed of the rotation speed of the internal combustion engine is a predetermined value or more; A rotation speed control device for an internal combustion engine, comprising: restriction means for restricting the operation of the intake air amount control means when the rotation speed is higher than a predetermined speed.