JPS6364621B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an idle speed control device that controls the idle speed to a predetermined idle speed without abnormally increasing the idle speed even when the idle speed control system fails.

Conventionally, in gasoline engines for automobiles, the air-fuel ratio (referred to as A/F) has been mechanically controlled independently by a means for supplying fuel to engine intake air, such as a carburetor.

However, with this method, it is difficult to finely control the A/F appropriately and accurately depending on the operating state of the engine.
A microcomputer (called a microcomputer) is used to capture various data representing the operating status of the engine, and an electro-mechanical actuator is used to control the operation of the carburetor, etc., and A/F control is performed appropriately and accurately. Electronic control systems have become widely adopted.

An example of such an electronic control system (hereinafter referred to as EEC) is shown in FIGS. 1 to 4.

Figure 1 shows the entire system, where 1 is the engine, 2 is the carburetor, 3 is the slow solenoid, and 4 is the
is the main solenoid, 5 is the fuel solenoid,
6 is an idle detection switch, 7 is a throttle actuator, 8 is an intake negative pressure sensor, 9 is a cooling water temperature sensor, 10 is a pulse type engine speed sensor,
11 is an O ₂ sensor, and 12 is a control unit. Note that 30 to 32 will be described later.

FIG. 2 shows the configuration of the carburetor 2 and the solenoids 3 to 5 associated therewith.

In the figure, 13 is a throttle valve (hereinafter referred to as
It is called a throttle valve).

The slow solenoid 3 controls the amount of fuel supplied to the slow port and idle port of the carburetor 2 by controlling the air of the slow air bleed, and the main solenoid 4 controls the amount of fuel supplied to the main nozzle. Further, the fuel solenoid 5 controls the amount of fuel supplied to a bypass air passage provided for the throttle valve 13.

Therefore, by controlling the slow solenoid 3 and the main solenoid 4, the A/F in the slow main system of the carburetor 2 is controlled, and the fuel solenoid 5
If this is controlled, the A/F in the increase system of the carburetor 2 will be controlled.

FIG. 3 shows the configuration of the throttle actuator 7.

In the figure, 14 is the shaft of the throttle valve 13, 15 is the opening/closing lever attached to the shaft 14, 16 is the return lever, 17 is the return spring, 18 is the stroke shaft, 19 is the reduction gear, 20 is the DC motor, and 21 is the It's a spring. Note that 2 is a carburetor, 6 is an idle detection switch, 12 is a control unit, and 13 is a throttle valve.

When the accelerator pedal is not operated, the throttle valve 13 returns to the return position due to the tension of the return spring 17. At this time, the return position is such that the opening/closing lever 15 is in the position of the stroke shaft 18.
It is determined by the position where it touches. Since the stroke shaft 18 is held on the gear 19 by a screw, it sends a signal to the motor 20 to move the gear 1.
By rotating the throttle valve 9, the return position of the throttle valve 13 can be arbitrarily controlled.

The stroke shaft 18 and the gear 19 as a whole are configured to be able to move slightly in the longitudinal direction of the shaft 18, and when the throttle valve 13 is opened from the return position by operating the accelerator pedal, the stroke shaft 18 and the gear 19 are moved as shown in the figure by the spring 21. As shown by the broken line, when the switch 6 is opened by being displaced to the left and the throttle valve 15 returns to its return position due to the tension of the return spring 17, the opening/closing lever 15 is pressed against the stroke shaft 18, and the spring 21 is pushed in. The switch 6 is configured to close. Therefore, depending on whether the switch 6 is turned ON or OFF, it is possible to detect whether the throttle valve 13 is being operated via the accelerator pedal or whether it has returned to the return position.

FIG. 4 shows an example of the control unit 12, which includes a control logic 22, a microprocessor 23, a ROM 24, and a multiplexer 2.
5. Consists of an analog/digital converter 26, etc., and detects the intake negative pressure V _c from the negative pressure sensor 8 (Fig. 1).
and the engine temperature T _w from the water temperature sensor 9, and
Analog data such as the voltage V ₀ from the O ₂ sensor 11 is converted to digital data such as data T _HSW from the idle detection switch 6 and engine speed N from the rotation speed sensor 10 via the multiplexer 25 and analog-to-digital converter 26. are taken into the control logic 22 as they are, processed by the microprocessor 23 and ROM 24,
Various actuators, such as the slow solenoid 3, main solenoid 4, fuel solenoid 5, and throttle actuator 7, are controlled to obtain the optimum A/F according to the operating state of the engine.

Therefore, in the electronic control system configured as described above, the optimum control is performed by controlling the slow and main solenoids 3 and 4 in the steady operating state and the warm-up operating state, depending on various data representing the operating state of the engine. At the time of starting, the A/F is controlled to the optimum state by controlling the fuel solenoid 5, and furthermore, by controlling the throttle actuator 7, the idle state and left warm-up state are controlled. The engine speed can be controlled to the optimum condition.

The control mode for the throttle actuator 7 at this time is to drive the DC motor 20 with pulses in order to enable digital control by the control unit 12, thereby moving the stroke shaft 18 in and out to adjust the throttle. Valve 1
The pulses supplied at this time have a waveform as shown in FIG. 5, and have a predetermined pulse width _Pw during a predetermined repetition period T. Therefore, when this pulse is supplied to the DC motor 20, the number of rotations obtained each time one pulse is supplied is a constant value, and the amount of movement of the stroke shaft is determined by the number of supplied pulses. That will happen.

Then, the return position of the throttle valve 13, that is, the opening degree of the throttle valve 13 in the idle state is determined depending on the position to which the stroke shaft 18 has moved, and the engine rotation speed is thereby determined. As shown in FIG. 6, the number of revolutions of the engine can be controlled by the number of pulses supplied to the DC motor 20 of FIG. In this Fig. 6, the straight line A shows that when a positive pulse is applied,
B is the characteristic when a pulse of negative polarity is applied.

Further, such a system is usually equipped with an exhaust gas recirculation rate (EGR) control device, and therefore an EGR solenoid 30 and an EGR valve 31 are provided as shown in FIG. The details are shown in FIG.

This EGR solenoid 30 is driven by a pulsed on/off signal from the control unit 12 as shown in FIG. Therefore, the valve opening rate is controlled and air leaks.
Ai is adjusted, the negative pressure given to the EGR valve 31 is changed, and the recirculation amount of exhaust gas Ga is controlled.
Controls EGR. The relationship between the period t and the period T in FIG. 8 is represented by [t/T×
100%] is called on-duty, and by controlling this on-duty, Figs. 9 and 10
As shown in the figure, the negative pressure applied to the EGR valve 31 changes, and EGR is controlled.

Therefore, in the above-described system, EGR can be controlled according to the operating state of the engine, and the state of exhaust gas can be maintained in an optimal state.

Thus, according to the EEC mentioned above,
Most of the engine-related controls such as A/F control can be performed appropriately, and it is possible to fully meet strict exhaust gas regulations, as well as provide an engine control device with excellent fuel ratio and driving feel.
It has come to be adopted in many cars.

By the way, since various actuators are used in cars equipped with such EEC, if any of these actuators malfunction, control operations will not be performed properly, and in extreme cases, it will be impossible to continue driving. This poses a problem in that the vehicle may become damaged or it may become dangerous to continue driving.

For example, if the throttle actuator 7, which is the actuator of the idle speed control system (ISC), fails and the throttle valve 13 remains open, the engine speed in the idle state will suddenly increase.
In extreme cases, it can become a dangerous situation.

Therefore, the conventional EEC has the disadvantage that if the actuator of the ISC fails, it becomes difficult to drive the vehicle and it is likely to cause a breakdown on the road.

SUMMARY OF THE INVENTION An object of the present invention is to provide an ISC device that eliminates the drawbacks of the prior art described above and can prevent the idle speed from increasing rapidly even if the ISC actuator fails.

In order to achieve this object, the present invention is characterized in that when a failure of the ISC actuator is detected, EGR control is performed in an idling state according to the engine speed.

Embodiments of the idle speed control device according to the present invention will be described below with reference to the drawings.

FIG. 11 is a flowchart illustrating the operation of one embodiment of the present invention. Note that even in this example
The overall structure of the EEC is shown in Figures 1 to 10.
It is almost the same as the conventional EEC shown in the figure,
However, the operation shown in Fig. 11 is incorporated as one of the control programs of the microcomputer consisting of the CPU 102, ROM 104, etc. shown in Fig. 4, and the vehicle speed sensor shown as 32 in Fig. 1 is installed. The only difference is that the control unit 12 is configured to be able to read data representing vehicle speed.

The program that executes the flowchart shown in FIG. 11 is started at predetermined intervals like other control programs, and when the program is started and the flowchart starts to be executed, First, in step (hereinafter referred to as S) 1, [vehicle speed>
0], and if the result is YES,
In other words, when the car is running, it goes to S2, first clears the elapsed time measurement memory (described later), then goes to S3, outputs the on-duty signal to the EGR solenoid 30, and outputs a stop signal to the throttle actuator 7 in S4. and exit to the exit.

Therefore, at this time, normal EGR control is performed and ISC control is stopped.

On the other hand, if the result in S1 is NO, that is, it is determined that the car is stopped, turn to S5,
The data of the idle detection switch 11 is checked to determine whether it is ON or not. When the result is NO, that is, it is determined that the accelerator pedal is depressed, the driver turns to S2 in the same way as when the result was YES in S1, stops ISC control, and resumes normal operation.
Enter EGR control.

However, when the result in S5 is determined to be YES, proceed to the next step S6 and check whether the throttle actuator failure flag (described later) is set, that is, whether the failure flag is 1, and if the result is YES. In some cases, it immediately goes to S7, reads the engine speed N from the speed sensor 10, and checks whether it is equal to or higher than a predetermined speed N _set given in advance as a function of engine temperature as shown in FIG. In other words, it is checked whether [N≧N _set ]. If the result is YES, proceed to S8 and increase the on-duty of the EGR solenoid 30 by a predetermined value; on the other hand, if the result is NO, proceed to S9.
The on-duty for the EGR solenoid 30 is reduced by a predetermined value, and each exits to the exit. By the way, it is known that changing EGR changes the operating state of the engine, resulting in a change in engine speed. Therefore, by changing the on-duty of the EGR solenoid 30, the engine speed can be controlled as shown in FIG. 13. In FIG. 13, the rotation speed N ₃ indicates the engine rotation speed at a certain throttle valve opening state. At this time, when the on-duty of the EGR solenoid 30 is changed from 100% to 0%, the engine rotation speed increases. It has been shown that it can be reduced to _N4 .

Therefore, the operation according to the flowchart shown in FIG. 11 is repeated every predetermined activation cycle,
If you pass from S7 to S8 or S9 each time,
The rotational speed of the engine in the idle state is convergently controlled to a predetermined rotational speed N _set without using the throttle actuator 7.

Now, returning to S6, when the judgment result in S6 is NO, the process goes to S10 and measures the elapsed time since the vehicle speed was 0 and the idle detection switch 6 was turned ON. This measurement operation may be performed as follows. In other words, the operation according to this flowchart is repeated at a predetermined starting cycle, and S10 is only entered when the vehicle speed is 0 through S5 and S6 and the idle detection switch 6 is turned on. Every time this S10 is entered, 1 is added to the addition memory.

After 1 is added to the addition memory through S10, the process proceeds to the next S11, and in S10 it is determined whether the elapsed time being measured has exceeded a predetermined time. Of course, this judgment is made by comparing the added value in the addition memory with a predetermined value,
This is done depending on whether the added value exceeds a predetermined value.

If the result in S11 is YES, proceed to S12,
First, in S10, the memory for adding the elapsed time being added is cleared, and then in S13, the engine rotation speed N is checked to see if it has reached the predetermined rotation speed N _set plus alpha.
It is determined whether [N≧N _set +α].
Then, only when the result becomes YES, it is determined that the throttle actuator 7 has failed, and the failure flag is set to 1 in the following S14.

Therefore, from now on, when the program to execute this flowchart starts and advances to S6 through S1 and S5, it will all turn to S7,
Step S8 or S9 is executed, and the engine speed in the idle state is set to a predetermined value by EGR.
Control will be performed to converge to N _set .

On the other hand, when the result in S13 is ON, that is, when the engine speed in the idle state has not increased by plus alpha from the predetermined value N _set , it indicates that the control by the throttle actuator 7 is in a normal state. , turn to S15, set the on-duty for EGR solenoid 30 to 100%, and set the EGR
to zero. This is because EGR is not performed during idling under normal conditions.

After S15, the process proceeds to S16, where the engine rotation speed N is taken in and checked to see if it is greater than a predetermined value N _set . Figure)
If the result is NO, the normal rotation pulse A is supplied to the throttle actuator 7 in S18, and each exits to the exit.

By passing through these steps S15 to S18,
Since the throttle actuator 7 performs the normal idle speed control operation, that is, the ISC function, when S6 is reached after passing through S1 and S5,
That is, when the engine is at idle,
Moreover, if the failure flag was not set in S6, the predetermined time had not elapsed in subsequent S10 and S11, or the engine speed did not exceed [N _set + α] even after passing through S12 and S13. In other words, when it is determined that a failure has not occurred in the throttle actuator 7 after performing the operations necessary to determine the failure of the throttle actuator 7, the process always passes through S15 to S17 or S18. Control will be executed and normal ISC operations will occur.

Therefore, according to this embodiment, while the throttle actuator 7 is determined to be normal, the normal operation is performed via the throttle actuator 7.
Once the ISC function is performed and an abnormality occurs in the throttle actuator 7, the ISC function will be performed under EGR control. Also, the engine speed in the idle state does not increase, and the idle speed can always be controlled to the predetermined value N _set .

In the embodiment shown in FIG. 11, S2 is provided in order to ensure that the elapsed time in S10 is measured correctly.

The idle speed control operation according to this embodiment will be explained in more detail with reference to FIG. 14.

Since the temperature of the engine changes depending on the elapsed time after starting, the horizontal axis in FIG. 14 can be considered to represent time t and also the horizontal axis in FIG. 12, which is the engine temperature. Therefore, in FIG. 14, the predetermined rotational speed N _set is also a function of time t.

Therefore, after the engine is started, when the idle speed of the engine is controlled to a predetermined target speed N _set via the throttle actuator 7, the throttle actuator 7 breaks down at time _t0 . shall be.

Then, in the prior art, the broken line C in FIG.
As shown in , after this point t ₀ it becomes impossible to control the idle rotation speed to be less than the current rotation speed Nt ₀ .

However, in this example, time t ₀
At time _t1 , when a predetermined time has elapsed since then, the throttle actuator 7 is determined to have failed, and from this time _t1 onwards, the idle speed is controlled by EGR, so the solid line D in FIG. As shown by , control is performed to converge to the predetermined target value N _set even after time t ₁ , and the idle speed does not increase abnormally.

It should be noted that although the above description is about an embodiment of a carburetor type engine, it goes without saying that it is also applicable to a fuel injection type engine.

As explained above, according to the present invention, in the EEC of an automobile engine equipped with an idle speed control system, even if a failure occurs in the actuator for controlling the idle speed, the idle speed will not rise abnormally. Since it is possible to provide a back-up function that correctly controls the rotation speed to a predetermined rotation speed, it eliminates the drawbacks of the conventional technology and allows safe operation even if the actuator fails, and the EEC idle rotation that does not cause failures on the road. A number control device can be provided.

[Brief explanation of drawings]

Figures 1 to 8 show the electronically controlled engine control system. Figure 1 is a schematic diagram showing the entire system, Figure 2 is a sectional view of the carburetor, and Figure 3 is the throttle actuator. Fig. 4 is a block diagram of the control unit, Fig. 5 is a waveform diagram for explaining the operation, Fig. 6 is a characteristic diagram for explaining the operation, Fig. 7 is a schematic diagram of the exhaust gas recirculation amount control system, FIG. 8 is a waveform diagram for explaining the operation, FIGS. 9 and 10 are characteristic diagrams for explaining the operation, FIG. 11 is a flowchart showing one embodiment of the idle speed control device according to the present invention, and FIG. 14 through 14 are characteristic diagrams for explaining the operation. 6... Idle detection switch, 7... Throttle actuator, 12... Control unit, 30... EGR solenoid, 31... EGR valve, 32... Vehicle speed sensor.

Claims (1)

[Scope of Claims] 1. In an electronically controlled engine control device equipped with an idle speed control system and an exhaust gas recirculation system, there is provided a failure detection means for detecting an abnormality in an actuator means for controlling the idle speed; idling detection means for detecting that the state is in the idle state, and recirculation flow control actuator means for controlling the amount of exhaust gas recirculation, and when an abnormality in the actuator means is detected by the failure detection means, the recirculation flow control actuator means is activated. An idle rotation speed control device, characterized in that the idle rotation speed control device is configured to perform control according to the engine rotation speed in an idle operating state, and to control the idle rotation speed to a predetermined value. 2. The idle rotation speed control device according to claim 1, wherein the actuator means for controlling the idle rotation speed is an actuator means for controlling the throttle valve return opening degree of the carburetor. 3 In claim 1 or 2,
The failure detection means for the actuator means for controlling the idle rotation speed includes a sensor means for detecting the running speed of the vehicle, and a predetermined period of time has elapsed since it is detected that the running speed of the vehicle is zero and the engine is in an idle state. An idle rotation speed control device characterized in that it is configured to perform failure detection on the condition that the engine rotation speed is equal to or higher than a predetermined value.