JPH0670392B2 - Control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a PID for controlling the rotational speed of an internal combustion engine.
Alternatively, the present invention relates to a control device for an internal combustion engine having a rotation speed controller that produces a PI control signal.

[Prior Art] It is well known that, in an internal combustion engine, the NOx, CO and other harmful gas components in exhaust gas are reduced as the air-fuel ratio (A / F) is increased. . However, there is a difference in the output characteristics of the internal combustion engine when operating in a region where the air-fuel ratio is large and a region where the air-fuel ratio is small. This causes a shortage of output, causing a problem such as a reduction in rotation speed or engine stall.

For this reason, a potentiometer (a linear type or a rotary type) is provided inside the throttle portion or the actuator of the internal combustion engine to detect the throttle opening, reduce the rotational speed, or stop the internal combustion engine.

In addition, it is necessary to reduce the air-fuel ratio in order to improve the startability even when starting the internal combustion engine.

[Problems to be Solved by the Invention] However, this potentiometer becomes a load on the actuator for operating the throttle, and it is necessary to increase the capacity of the actuator, and a potentiometer satisfying high durability (high reliability) is expensive. Is. Further, if the throttle unit or the actuator unit of the internal combustion engine and the control unit are separated from each other, there is an inconvenience in wiring processing.

In addition, if a special choke mechanism is used to control the air-fuel ratio to improve the startability even when the internal combustion engine is started, the structure becomes complicated.

Therefore, the present invention improves the startability of the internal combustion engine with a simple structure, and further improves the rotation control device after the internal combustion engine is started.
Using the PID (PI) control signal, the air-fuel ratio is changed to automatically switch the output characteristics of the internal combustion engine, normalization of exhaust gas, and high efficiency operation of the internal combustion engine from start to stop are realized.
Moreover, it is an object of the present invention to provide an inexpensive control device for an internal combustion engine, which has high control accuracy.

[Means for Solving the Problems] In order to achieve the above object, an internal combustion engine control device according to the present invention provides an engine start / stop control device for controlling start and stop of an internal combustion engine, and a rotation speed of the internal combustion engine. A rotational speed controller that produces a PID or PI control signal for control, a first solenoid valve for varying the air-fuel ratio that is set to a normally open state, and a second empty space that supplies auxiliary fuel that is set to a normally closed state. The solenoid valve for varying the fuel ratio and the first solenoid valve for varying the air-fuel ratio at the time of starting the internal combustion engine are closed and the second solenoid valve for varying the air-fuel ratio is opened to start the engine.
When the start completion signal is input from the stop control device, the PID or PI control signal from the rotation speed controller is received as a load detection signal, and after a predetermined time, the first air-fuel ratio variable solenoid valve is opened. Hold and control the opening / closing of the second solenoid valve for varying the air-fuel ratio to decrease the air-fuel ratio when the level of the load detection signal exceeds the upper limit of the predetermined hysteresis width of the hysteresis comparison circuit. The air-fuel ratio is returned to a relatively large state and the output of the internal combustion engine is adjusted. When the internal combustion engine is stopped, the first air-fuel ratio varying solenoid valve is closed, and the second air-fuel ratio varying solenoid is closed. And an air-fuel ratio control device for starting the valve in an open state.

[Operation] According to the present invention, when the internal combustion engine is started, the first air-fuel ratio changing electromagnetic valve is closed and the second air-fuel ratio changing electromagnetic valve is opened to start the engine.

Also, when the start completion signal from the engine start / stop control device is input, the PID from the rotation speed controller or
The PI control signal is received as a load detection signal, and after a predetermined time, the first air-fuel ratio variable solenoid valve is held in the open state, and the second
When the level of the load detection signal exceeds the upper limit of the specified hysteresis width of the hysteresis comparison circuit, the air-fuel ratio is decreased, and when it falls below the lower limit of the hysteresis width, the air-fuel ratio is compared with the original comparison. Then, the output of the internal combustion engine is adjusted.

Furthermore, when the internal combustion engine is stopped, the first air-fuel ratio varying solenoid valve is closed and the second air-fuel ratio varying solenoid valve is opened, and the internal combustion engine is started.

[Embodiment] The present invention will be described in detail below based on an embodiment shown in the drawings.

FIG. 1 is an overall configuration diagram of an internal combustion engine controller according to the present invention, which includes a rotation speed controller 10 and an air-fuel ratio controller 20. The rotation speed controller 10 is, as shown in FIG.
A waveform shaping amplifier circuit 11 that receives a signal from a rotation sensor 6 that detects the rotation speed of the engine 1, a frequency / voltage conversion circuit 12, a differential amplifier circuit 13, a proportional / integral / derivative (PID) operation, Or P. to perform proportional / integral (PI) operation
It is composed of an ID (PI) controller 14, a pulse width modulation circuit 15, and a driver circuit 16.

An actuator 2 drives a throttle valve 5 of the engine 1 and is driven by a pulse output from a rotation speed controller 10. The actuator 2 is usually driven by a rectangular wave, and its pulse width is changed by the pulse width modulation circuit 15 in the rotation speed controller 10. This allows the actuator 2
The output of the throttle valve 5 is adjusted via the wire 3.
Is operated. The throttle opening is determined by the balance between this actuator output and the external spring 4. The rotation speed of the engine 1 is detected by the rotation sensor 6, is fed back to the rotation speed controller 10, and is compared with the value of the rotation speed setting device 7 which is manually operated, and further, a comparator which constitutes a pulse width modulation circuit 15. The level of the sawtooth wave from the reference frequency generation circuit 18 is compared at 17 to adjust the rotational speed of the engine.

The air-fuel ratio control device 20 uses one of the signals generated by the rotation speed controller 10 as a load detection signal, controls the control relay LY2 according to the load state of the engine 1, and from the engine start / stop control device 19 Control relay upon receipt of start-up completion signal
Control LY1.

As the load detection signal, a proportional / integral / derivative (PID) control signal or a proportional / integral (PI) control signal in the preceding stage of the pulse width modulation circuit 15 of the rotation speed controller 10 is used. P.
The reason for using the ID (PI) control signal is that the throttle opening and the PID (PI) control signal have a one-to-one characteristic curve as shown in FIGS. 3 and 4 (θ _L is V _L ,
This is because θ _{H corresponds} to V _H and θ max corresponds to V max), and since the load detection signal is a DC level signal instead of a rectangular wave, there are many advantages such as simplification in circuit processing.

The outline and operation of the air-fuel ratio control device 20 will be described below with reference to the block diagram of FIG. The circuit configuration of the air-fuel ratio control device 20 includes a buffer circuit 21, a filter circuit 22, a hysteresis comparison circuit 23, a gate (AND) circuit 24, a timer circuit 25, and relay driver circuits 26 and 27.

First, the buffer circuit 21 receives the PID signal input section of this control device with high impedance and prevents the PID control signal from being affected by the addition of this device.
Next, the filter circuit 22 by CR is for removing the ripple of the PID signal, and by this, the PID control signal is converted into a complete DC level signal, and the hysteresis comparison circuit of the next stage.
In addition to improving the detection accuracy of 23, it also prevents malfunctions when the PID control signal undergoes transient fluctuations (large level fluctuations). As will be described later in detail, the hysteresis comparison circuit 23 has a constant hysteresis width in which the upper limit is V _n and the lower limit is V _L with respect to the input level, as shown in FIG. This will be explained with reference to FIG. 5. When the load increases according to the route of the output characteristic I and exceeds the specified load, the throttle opening reaches θ _H , and the PID control signal accordingly When it reaches V _n, it is judged that it is overload, the control relay LY2 is turned on, and the second air-fuel ratio variable solenoid valve SV2 for supplementary combustion of the fuel supply device is opened, so the air-fuel ratio becomes small and the engine output characteristic is As the output characteristic changes from I to II, the throttle opening decreases from θ _{H to} θ _A as in the route. Then, if the load further increases, the route of the output characteristic II is followed. Conversely, when the load decreases according to the route and the throttle opening reaches θ _L , it is determined that the PID control signal becomes V _{L and the} overload is released, and control relay LY2
Is turned off, the second solenoid valve SV2 for varying the air-fuel ratio is closed, the air-fuel ratio is increased, and the engine output characteristic II is switched to I, and
The throttle opening decreases from θ _{L to} θ _B like the route. If the load increases thereafter, the operation follows the route, and if the load decreases, the operation follows the characteristic I of the route. Therefore, the whole operation is shown by the solid line in FIG.
Since the output is switched in accordance with the hysteresis characteristic of No. 2, there is no output shortage at the time of overload, and normalization of exhaust gas and high-efficiency operation are possible under normal load. However, when θ _A <θ _L or θ _B > θ _H is set, even if the load is constant, switching is performed again when the output is switched (route or), so that engine hunting occurs. Therefore, it is necessary to set θ _L <θ _A <θ _B <θ _H without fail. The hysteresis width (Δθ ₁ = θ _A −θ _L , Δ
Regarding the setting of θ ₂ = θ _H −θ _B ), it may be set to an optimum value in consideration of both the load fluctuation condition and the output characteristic of the engine.

Since the AND circuit 24 in the next stage uses the rotation speed controller that operates so that the throttle opening is fully opened when the engine is stopped or started as the rotation speed controller 10, the PID control signal output naturally exceeds θ _n. This is to prevent erroneous determination of overload and to start overload detection after the engine has completed startup. The detection starts when the start completion signal (completed at H level) is input from the external engine start / stop control device 19. The timer circuit 25 is for counting the elapsed time from the completion of the start of the engine. At the time of starting, the first solenoid valve SV1 for varying the air-fuel ratio is closed and only the solenoid valve SV2 for varying the second air-fuel ratio is opened. , The startability is improved by reducing the air-fuel ratio, and the timer set value T
After a second, the first air-fuel ratio variable solenoid valve SV1 is opened, and only the second air-fuel ratio variable solenoid valve SV2 is closed (stop, start mode).

FIG. 6 illustrates a specific circuit configuration of the control device 20. The hysteresis comparison circuit 23 includes a comparator 231 for comparison.
And a comparator 232 for switching are configured as a switching type hysteresis comparison circuit, and the upper and lower limits of the hysteresis width are set by the variable resistors VR1 and VR2.

Resistor R1 in the hysteresis comparison circuit is for current limiting, resistor R2
Is for current limitation (sink current of output transistor of comparator 232). Further, in the diode D1, when V _O is V _n (when the output transistor of the comparator 232 is off), a current flows into the V _L setting variable resistor VR ₁ side, and the set value of V _n is V _L. It is prevented from being affected by the set value. diode
When V _O becomes L level (when the output transistor of the comparator 232 is on), a current flows from the V _L setting variable resistor VR1 side to the output transistor of the comparator 232, and _{D 2} is set to V _L. The value is prevented from being affected when V _O changes from V _{n to} L level. Since the resistance R3 has a large input impedance of the comparator 231, the operation tends to be unstable. Therefore, by inserting the resistance R3, the impedance is lowered and the operation is stabilized.

Finally, based on the detailed circuit diagram of FIG. 6, the operation of the control device will be described with reference to FIG.

(Stop / Start Mode) First, when power is applied to the rotation speed controller 10 and the control device 20 when the engine is stopped (see FIG. 7), V _n > is applied to the − input terminal of the comparator 231. Due to V _L , V _n is applied via D2. On the other hand, the PID control signal from the rotation speed controller 10 is applied as V _C to the + input terminal of the comparator 231 via the filter circuit 22.

Therefore, when V _C <V _n , the output V _O of the comparator 231 is at L level. Thus the comparator 232 - input terminal is at the L level, the + input V _{for R} (reference voltage) is set at an intermediate position of the advance H level and L level, the output V _O of the comparator 232 is V _n Since it has passed through the setting VR2 and the resistor R2, it is at V _n (the output transistor of the comparator 232 is off). Next, when the throttle is fully opened when the engine is stopped, the level of the PID control signal rises with the lapse of time after the power is turned on, and finally exceeds V _n (the same state as at the time of overload). Therefore, when V _C > V _n , the comparator 23
It becomes larger than the + input (constant V _n ) of 1 and the output V _O is inverted to the H level. Therefore, the − input of the comparator 232 becomes larger than the + input, and the output V _O of the comparator 232 becomes L level (the output transistor of the comparator 232 is in the ON state). Then, the − input of the comparator 231 has been V _n until now, but since the output V _O of the comparator 232 becomes L level, it is switched to V _L. After that, when V _C <V _L , the comparator 231
The output V _O of switched again from the H level to L level. However, the input 2 of the AND circuit 24 is connected to the engine start / stop control device 19, and the start completion signal from the device is
Since the output is at the L level when the engine is stopped or started, the output of the AND circuit 24 is at the L level even if the input 1 of the AND circuit is at the H level as described above, and the transistor of the relay driver circuit 26 is Tr2 is not turned on and control relay LY2 is not energized. The overload indicator 28 prevents an erroneous overload display.

On the other hand, the operation of the timer circuit 25 when the engine is stopped and when the engine is started (see FIG. 7) is as follows. Under this condition, the start-up completion signal is at the L level, and therefore the reset input portion of the timer circuit 25 is at the L level, so the counting is stopped, the timer output is off, and the transistor Tr1 and the control relay LY1 are not energized. It is in a state. However, since the second solenoid valve SV2 for varying the air-fuel ratio is opened by the b contact (Fig. 1) of the control relay LY1, the air-fuel ratio is set small. After the engine start is completed, the start completion signal becomes H level, the timer circuit 25 starts counting, and the timer setting
After the time T seconds set by VR, the control relay LY1 is energized, the a contact of the relay is turned on, the b contact is turned off, the first solenoid valve SV1 for varying the air-fuel ratio is opened, and the second air valve is opened. The solenoid valve SV2 for varying the fuel ratio is closed and the air-fuel ratio is set large (characteristic curve I in FIG. 5).

(Normal mode / overload mode) After the timer circuit 25 times out, normally, the
The normal mode follows the characteristic curve I in the figure. When an overload occurs thereafter, the output V _O of the comparator 231 and the start completion signal are at the H level, so the output of the AND circuit 24 becomes the H level, and the second solenoid valve SV2 for varying the air-fuel ratio is opened. The air-fuel ratio is smaller than in the normal mode again (Characteristic curve II in Fig. 5)
Set to improve engine output. This second air-fuel ratio variable solenoid valve SV2 is closed and the air-fuel ratio becomes large (characteristic curve I in FIG. 1) because the load decreases and the PID control signal (V _C ) reaches V _L or less. It's time.

The switching type hysteresis comparison circuit 23 does not necessarily have to be configured by an operational amplifier, and for example, the switching comparator 232 can be configured by using a switching transistor as shown in FIG.

In the above embodiment, the hysteresis comparison circuit 23 is a reference voltage (V _n , V _L ) switching type hysteresis comparison circuit. This is because V _n and V _L are direct because the reference voltage by the external variable resistor is determined, and because V _n and V _L can be set independently, adjustment is convenient. However, a conventional positive feedback type hysteresis comparison circuit can also be used.

[Advantages of the Invention] As described above, the present invention, when starting the internal combustion engine,
The first solenoid valve for varying the air-fuel ratio is closed and the second solenoid valve for varying the air-fuel ratio is opened to increase the air-fuel ratio to start the engine, thereby improving startability.

Also, after the internal combustion engine is started, the first air-fuel ratio variable solenoid valve is held in the open state, and the PID (PI) of the rotation speed controller is maintained.
By controlling the second air-fuel ratio variable solenoid valve by using the control signal, the air-fuel ratio is automatically switched. Therefore, the output under engine load can be improved with a simple structure, and the exhaust gas It is possible to realize high-efficiency operation of the internal combustion engine from normalization and from start to stop.

Further, since the potentiometer is not used for load detection and the load is detected by an electric means, the output control of the engine can be performed quickly and accurately with a simple structure.

Further, when the internal combustion engine is stopped, the first air-fuel ratio varying solenoid valve is closed, and the second air-fuel ratio varying solenoid valve is opened, so that the internal combustion engine can be started. Guaranteed to start.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an internal combustion engine controller according to the present invention,
FIG. 2 is a block diagram of a rotation speed controller and a control device for an internal combustion engine controller according to the present invention, FIG. 3 is a diagram showing a load-throttle opening characteristic, and FIG. 4 is a load-PID (PI) control signal. FIG. 5 is a diagram showing characteristics, FIG. 5 is a diagram showing engine output versus throttle opening characteristic, FIG. 6 is a diagram showing a concrete circuit example of the control device of FIG. 2, and FIG. 7 is a diagram of the control device of FIG. An operation time chart, FIG. 8 is a diagram showing another circuit example of the switching comparator of the comparator circuit with hysteresis, and FIG. 9 is a diagram showing hysteresis characteristics of the hysteresis comparator circuit. 1 …… Engine 10 …… Rotation speed controller 19 …… Engine start / stop controller 20 …… Air-fuel ratio controller 23 …… Hysteresis comparison circuit 25 …… Timer circuit LY1, LY2 …… Control relay SV1 …… First Solenoid valve for varying the air-fuel ratio SV2 …… Second solenoid valve for varying the air-fuel ratio

Claims (1)

[Claims] 1. An engine start / stop control device for controlling start and stop of an internal combustion engine, a rotational speed controller for producing a PID or PI control signal for controlling the rotational speed of the internal combustion engine, and a normally open state. A first air-fuel ratio variable solenoid valve, a second air-fuel ratio variable solenoid valve that supplies auxiliary fuel that is normally set to a closed state, and the first air-fuel ratio variable solenoid when the internal combustion engine is started. When the valve is closed and the second air-fuel ratio variable solenoid valve is opened, and the start completion signal is input from the engine start / stop control device, the PID or PI control signal from the rotation speed controller is input. A load detection signal is received, and after a predetermined time, the first air-fuel ratio varying solenoid valve is held in an open state, the second air-fuel ratio varying solenoid valve is controlled to open and close, and the level of the load detection signal is a hysteresis comparison circuit. of When the upper limit of the predetermined hysteresis width is exceeded, the air-fuel ratio is reduced, and when it is lower than the lower limit of the hysteresis width, the air-fuel ratio is returned to a relatively large state, and the output of the internal combustion engine is adjusted. An air-fuel ratio control device for starting the first air-fuel ratio changing solenoid valve in a closed state and the second air-fuel ratio changing solenoid valve in an open state.