JPS6334302B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for preventing deterioration of exhaust gas during deceleration of a gasoline engine having an electronically controlled carburetor.

As interest in environmental conservation such as the prevention of air pollution increases, regulations on exhaust gas from gasoline engines are becoming increasingly strict. It has become impossible to meet these strict exhaust gas regulations.

However, in conventional carburetors, which control the air-fuel ratio in response to engine operating conditions mainly through the response of mechanical parts, many factors that represent the engine operating conditions are used. Since it is difficult to take in the A/F for control and reflect it in the control, it is practically impossible to precisely control the A/F to satisfy exhaust gas regulations using such a carburetor. Therefore, so-called electronically controlled carburetors (ECCs) have been put into practical use, which are configured so that most of the controls necessary for the carburetor, such as A/F control, are performed electronically.

An example of such an A/F control device using ECC is shown in FIG.

In the figure, 1 is the engine, 2 is the carburetor, 3 is the slow solenoid, 4 is the main solenoid, 5 is the fuel solenoid, 6 is the limit switch, and 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 idle detection switch,
12 is a control unit.

FIG. 2 shows the configuration of the throttle actuator 7.

In the figure, 14 is a throttle valve (hereinafter referred to as
13 is a shaft (referred to as a throttle valve), 15 is an opening/closing lever attached to the shaft 14, 16 is a return lever, 1
7 is a return spring, 18 is a stroke shaft, 19 is a reduction gear, 20 is a DC motor, 21
is a spring. Note that 2 is a carburetor, 11 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, the switch 11 is opened by being displaced to the left, and when the throttle valve 13 returns to its return position under 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 11 is configured to close. Therefore,
By turning the switch 11 on and 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.

Furthermore, when the throttle valve 13 returns to the fully closed position, the limit switch 6 operates.
By the data L _iSW of the limit switch 6, it is possible to detect that the throttle valve 13 has returned to the fully closed position.

FIG. 3 shows an example of the control unit 12, which is composed of a control logic 22, a microcomputer 23, a ROM 24, a multiplexer 25, an analog-to-digital converter 26, etc. Intake negative pressure V _C
Analog data such as the engine temperature T _W from the coolant temperature sensor 9 is sent to the limit switch 6 via the multiplexer 25 and the analog-to-digital converter 26.
Digital data such as data L _iSW from the idle detection switch 11, data T _HSW from the idle detection switch 11, and engine rotation speed N from the rotation speed sensor 10 are each taken into the control logic 22 as they are, and are then processed by the microcomputer 23, ROM 24, etc. and controls various actuators such as slow solenoid 3, main solenoid 4, phenyl solenoid 5, throttle actuator 7, etc. to obtain the optimum A/F according to the engine operating condition. .

Therefore, in the A/F control device configured as described above, the optimum A/F is controlled by controlling the slow and main solenoids 3 and 4 in the steady operating state according to various data representing the operating state of the engine. In addition to controlling the A/F to the optimum state by controlling the phenyl solenoid 5 in the warm-up state, the throttle actuator 7 is further controlled to control the A/F in the idle state and the left-in warm-up state. The engine speed can be controlled to the optimum state.

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
3, and the pulse supplied at this time has a waveform as shown in FIG. 4, and has a predetermined pulse width P _W during a predetermined repetition period T. Therefore, when pulses are supplied to the DC motor 20, the number of revolutions obtained each time one pulse is supplied is a constant value, and the amount of movement of the stroke shaft 18 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. The throttle opening degree is controlled as shown in FIG. 5 by the number of pulses supplied to the DC motor 20 of No. 7, and the engine speed can be controlled as shown in FIG. 6. In this Fig. 5, the straight line A shows when a pulse of positive polarity is applied,
B is the characteristic when a pulse of negative polarity is applied.

By the way, even in such an ECC, when the accelerator pedal is depressed, the opening degree of the throttle valve 13 is naturally controlled by the driver, and the control by the throttle actuator 7 is stopped. The protruding position of the stroke shaft 18 remains at an opening position (hereinafter referred to as idle opening) corresponding to approximately the idle rotation speed.

Therefore, when the accelerator pedal is depressed and the engine speed is sufficiently higher than the idle speed, when the accelerator pedal is released, the throttle valve 13 suddenly idles as shown by the broken line in FIG. However, because the engine has inertia, the engine speed does not immediately return to the idle speed as shown by the broken line in Figure 8B, but drops to the idle speed with a time delay. do. As a result, the intake negative pressure rises rapidly and the condition of the exhaust gas deteriorates extremely. Therefore, in order to pass exhaust gas regulations, it is necessary to prevent the throttle valve 13 from suddenly returning to the idle opening even when the accelerator pedal is released.

For this purpose, it is conceivable to provide a mechanical damper such as a dart pot in the throttle valve 13, for example.

However, since the ECC is characterized by a structure in which various functions are performed electronically without providing a mechanical control device as a mechanical part of the carburetor body, it is not necessary to install a dash pot in the vaporizer. Providing mechanical parts such as
This is contrary to the original purpose of ECC, and the angle ECC
This method has the disadvantage that the meaning of the method is lost, and it is also undesirable in terms of cost.

Therefore, as a method suitable for ECC, the throttle actuator 7 is controlled even when the accelerator pedal is depressed from the idle position, and the throttle valve 1
3, the protruding position of the stroke shaft 18 is changed from the idle opening, and when the throttle valve 13 is about to return to the idle opening after the accelerator pedal is released, the opening/closing lever 15 is immediately moved.
(Fig. 2) comes into contact with the stroke shaft 18,
The opening degree of the throttle valve 13 is determined by the throttle actuator 7.
A method was devised to bring it under the control of

In any case, if the opening degree of the throttle valve 13 can be controlled by the throttle actuator 7, then the control unit 12 controls the throttle actuator 7, and the throttle valve 13 is slowly brought to the idle opening degree. It is possible to easily prevent deterioration of the exhaust gas by returning the throttle valve 13 to the same level as that of a dart pot, or by controlling the opening degree of the throttle valve 13 while monitoring the value of the intake negative pressure V _C. Because it can be done.

However, with this method, the throttle actuator 7 must be controlled to move the stroke shaft 18 to a predetermined position each time the accelerator pedal is depressed and the throttle valve 13 is opened from the idle position. The drawback was that it was difficult to determine conditions and set timing, making the configuration quite complex.

Additionally, related devices of this type include:
For example, Japanese Patent Publication No. 55-15623 can be mentioned.

SUMMARY OF THE INVENTION An object of the present invention is to provide an ECC deceleration correction device that eliminates the drawbacks of the prior art described above and that has a simple configuration and prevents the exhaust gas condition from deteriorating when the accelerator pedal is released.

In order to achieve this object, the present invention provides that when the engine speed is above a predetermined value and the idle detection switch is turned on, the throttle actuator is immediately controlled to move the stroke shaft from the idle opening position to the desired position. It is characterized by a displacement in the direction of opening the throttle valve by a fixed amount.

Embodiments of the deceleration correction device according to the present invention will be described below with reference to FIGS. 7 and 8 of the drawings.

FIG. 7 is a flow chart of one embodiment of the present invention, which is configured as one of various control programs executed by the control unit 12.

The control program shown in the flowchart of FIG. 7 is executed every 15 ms, for example. When this program is entered, the engine speed N is first read from the rotation speed sensor 10 (FIG. 1), and in the next step N ＞N See _OP . Here, N _OP represents data when the engine speed is 1300 rpm.

When N> _NOP is found, the program does not enter into the deceleration correction operation according to _the present invention, but instead proceeds to the step on the right side of the figure, and ends this program with control of the throttle actuator 7 remaining stopped.

When you look at N>N _OP , if it says YES, the idle detection switch 11 will be set in the next step.
Check whether it is ON or not using the data TH _SW . and
If NO, that is, the idle detection switch 11 is not closed, turn to the right step and end this program with the throttle actuator 7 fixed.

Also YES, that is, idle detection switch 11
is closed, in the next step V _C >
Determine V _OP ′. Here, V _C is intake negative pressure sensor 8
This is the intake negative pressure data obtained from the above, and V _OP ' is a preset discrimination value, the details of which will be described later.

When V _C >V _OP ' is NO, the step on the right side of the figure is executed and a positive pulse having a preset pulse width t _OP is supplied to the motor 20 of the throttle actuator 7.

Subsequently, in the next step, negative pulses are supplied to the motor 20 of the throttle actuator 7 at preset time intervals _td .

The next step is normal control by ECC,
The rotational speed control of the engine in the idle state is carried out via the throttle actuator 7, and this program is terminated.

Also, when it is determined that V _C > V _OP ′, it is YES.
If it is, the next step is to reduce the intake negative pressure V _C
Supply a positive pulse to the motor 20 of the throttle actuator 7 while looking at the
Control is performed so that V _C = V _OP , and then V _C
>The same program as when V _OP ′ is NO is executed and terminates.

Next, the operations obtained when the control program shown in the flowchart of FIG. 7 is executed will be explained with reference to FIGS. 8A to 8F.

Assume now that a car that is traveling at a certain speed at time _t0 enters a deceleration state at time _t1 , releases the accelerator pedal at time _t2 , and stops at time _t3 , as shown in Figure 8A. .

During this period, from time t ₀ to t ₂ , the engine speed N was greater than the rotation speed N _OP , that is, greater than 1300 rpm, as shown in Figure 2B, and the opening degree of the throttle valve 13 at this time was also Assume that the situation is as shown in Figure C.

Then, since the idle detection switch 11 is not closed until time t ₂ is reached, the control shown on the right in the flowchart of FIG. 7 is executed, and the control of the throttle actuator 7 remains fixed. There is.

Therefore, at this time, the stroke shaft 18 of the throttle actuator 7 remains stopped at the idle opening as shown in FIG. 8D.

At time _t2 , the accelerator pedal is released, so the idle detection switch 11 is turned on as shown in FIG. 8E.

Therefore, in this case, execution of the program on the left starts from the step of determining whether switch 11 is ON or not in the flowchart of FIG. 7, and V _C > V _OP '.
When the determination is NO, first, a positive pulse PP with a pulse width _tOP is supplied to the motor 20 of the throttle actuator 7, as shown in FIG. Therefore, as shown in FIG. 2D, the position of the stroke shaft 18 of the throttle actuator 7 increases rapidly at time _t2 and moves to a position corresponding to the pulse width _tOP . The pulse width t _OP at this time is set to a value necessary to open the throttle valve 13 from the idle opening to the opening corresponding to 1300 rpm at the engine speed. As a result, as shown in FIG. 8C, the throttle valve 1
3, the opening degree of the accelerator is temporarily returned to the opening degree at time _t2 , but the opening degree is immediately returned to the original opening degree. Since the movement of the throttle valve 13 at this time is quite fast, there is almost no change in the engine speed shown in FIG.

In the next step, as shown in FIG. 8, negative polarity pulses NP having a predetermined pulse width _td are sequentially supplied. Then, as shown in FIGS. 2 and 3, the stroke shaft 18 of the throttle actuator 7 slowly returns to the idle opening, and the throttle valve 13 accordingly returns to the idle opening. Therefore, as shown in Figure B, the engine speed N also decreases to the idle speed over a relatively long period from time t ₂ to t ₄ , so the intake negative pressure V _C increases. This prevents the exhaust gas from deteriorating. In other words, it is possible to provide the same effect as when a dart pot is provided.

The pulse width t _d at this time is equal to the engine speed N.
Set the intake negative pressure V _C to a value that does not rise above a predetermined value when the rotation speed decreases from N _OP to idle speed.
It may be determined in advance through experiments.

Also, when determining V _C > V _OP ′, it is
If YES, in the next step, while monitoring the intake negative pressure V _C , positive pulses are supplied to the motor 20 of the actuator 7 until it reaches V _OP '. In other words, at this time, the pulse width of the positive pulse PP shown in FIG. 8 becomes a function of the intake negative pressure V _C instead of the set value t _OP .

Therefore, at this time as well, as shown in FIG. 8 d and c, the position of the stroke shaft 18 of the throttle actuator 7 immediately moves to the opening position of the throttle valve 13 at time _t2 , and the throttle valve 13 also returns to its original position. Since the engine speed returns to the position shown in _FIG .

When entering the next step, the throttle actuator 7 is controlled so that V _C =V _OP . V _OP at this time is the intake negative pressure that can be tolerated against deterioration of exhaust gas, for example, a value of about -570 mmHg. Therefore, the so-called throttle opener function is performed by controlling this step. Become.

Note that this throttle opener is installed as a countermeasure against exhaust gas, and in any case, the intake negative pressure V _C is set to a predetermined value, for example -570 mmHg,
This is a function that controls the amount of water so that it does not increase beyond that level.

Also, as is clear from the above explanation, V _C >
V _OP ' in the V _OP ' determination step is the level that determines whether or not the throttle opener function is activated. Normally, V _OP ' = V _OP + C, and the value of C is Use several tens of mmHg. and,
Since it is considered that there is no need to operate the throttle opener when V _C >V' _OP is NO, such a determination step is provided.

As already explained, in the following steps, the dumppot function is performed by the negative polarity pulse NP shown in FIG.

In addition, the part after time _t4 in FIG.

As described above, according to the embodiment of the present invention, unlike the conventional example, it is not necessary to provide a dart pot or to constantly control the throttle actuator to follow the opening degree of the throttle valve. As shown by the broken line, the throttle valve closes abruptly, and this can prevent the engine speed from decreasing and the exhaust gas from worsening.

In addition, in Figure 8 A to D, the period from time t ₀ to t ₁ is all shown as a straight line to simplify the explanation, but in reality, the amount of depression of the accelerator pedal is not necessarily kept constant. It changes considerably depending on the driving conditions.

By the way, the broken line in Figure 8D shows the characteristics of the conventional example of the system in which the throttle actuator is controlled to constantly follow the throttle valve opening, but in reality, the part indicated by this broken line also changes considerably as mentioned above. doing.

Therefore, in this conventional example, pulses are supplied to the DC motor 20 of the throttle actuator 7 at an extremely high frequency. On the other hand, since such a DC motor includes a commutator and a brush, its lifespan is relatively short compared to other mechanical parts.

Therefore, in the conventional example described above, the throttle actuator reaches its service life limit in a relatively short period of time, making maintenance troublesome and disadvantageous in terms of cost. However, according to the embodiment of the present invention, Control of the throttle actuator is stopped during normal driving conditions where the operating time is relatively long, and control is only performed for relatively short periods such as during deceleration.
A great effect can be achieved in that the service life of the throttle actuator can be significantly extended.

Although the explanation has been mixed up, the flowchart in Figure 7 includes a step for determining N>N _OP , and this
The reason why the throttle actuator 7 remains fixed when NO is set is that the engine speed N is
This is to prevent deceleration correction from being performed when the engine enters a deceleration state from lower than 1300 rpm, since the intake negative pressure V _C hardly increases significantly and therefore the exhaust gas does not deteriorate. This further extends the service life of the throttle actuator 7.

Here, the correspondence between the structure of the present invention described in the claims and the structure of the above embodiment is as follows.

a [Idle detection switch means for detecting that the throttle valve has returned to a state where it can be controlled by the actuator means] → [Idle detection switch 11] b [Sensor means for detecting the engine speed] →
[Pulse type engine speed sensor 10] C [On condition that the engine speed is above a predetermined value and the idle detection means is activated, the actuator means is moved by a predetermined amount in the direction in which the opening degree of the throttle valve increases. [Control unit 12] → [Control unit 12
[Microcomputer 23] As explained above, according to the present invention, the exhaust gas during engine deceleration can be controlled without providing a dart pot on the throttle valve or setting complicated conditions for controlling the throttle actuator. Since gas deterioration can be prevented, it is possible to provide a deceleration correction device for ECC that has a long service life, is highly reliable, and is low cost, without the drawbacks of the prior art.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing an example of an internal combustion engine having an electronically controlled carburetor, Figure 2 is a conceptual diagram of the throttle actuator, Figure 3 is a block diagram of the control unit, and Figure 4 is a diagram of the throttle actuator. Figure 5 is a waveform diagram of the current supplied to the yuator, and Figure 5 is an explanatory diagram showing the operation of the throttle actuator.
The figure is a characteristic diagram showing the relationship between throttle opening and engine speed, Figure 7 is a flow chart showing the operation of an embodiment of the deceleration correction device according to the present invention, and Figure 8 A to F are characteristic diagrams showing the same operation. It is. 1... Engine, 2... Carburetor, 7... Throttle actuator, 8... Intake negative pressure sensor, 1
0... Pulse type engine speed sensor, 11...
Idle detection switch, 12... Control unit, 13... Throttle valve, 18... Stroke shaft, 20... DC motor.

Claims (1)

[Scope of Claims] 1. A deceleration correction device for an internal combustion engine having a motor-driven actuator means for controlling the return opening of the throttle valve and having a function of electronically controlling the engine speed, wherein the throttle valve is an idle detection switch means for detecting that the actuator means has returned to a state in which control is possible; a sensor means for detecting the engine speed; On condition that the throttle valve opening is increased by a predetermined amount, the actuator means is driven by a predetermined amount in a direction in which the opening of the throttle valve is decreased, and the control means is then driven in a direction in which the throttle valve opening is decreased at a predetermined rate. deceleration compensation device. 2. In claim 1, the control means is configured to include an intake negative pressure control function by the actuator means, and the predetermined amount is an amount necessary to maintain the intake negative pressure at a predetermined target value. A deceleration correction device characterized by: