JPS6321027B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control device in an intake negative pressure control state of an electronically controlled carburetor for a gasoline engine.

As interest in environmental conservation, such as the prevention of air pollution, increases, exhaust gas regulations for automobile engines such as gasoline engines are becoming increasingly strict, and air-fuel ratios (A/F) must be adjusted in detail according to engine operating conditions. Unless you control it,
It has become impossible to meet these strict exhaust gas regulations.

However, the vaporizers that have traditionally been used,
In most cases, the A/F is controlled in response to the operating state of the engine, mainly through the response of mechanical parts.In such carburetors, a large number of factors representing the operating state of the engine are incorporated for control. Since it is quite difficult to reflect this in the control, it is almost impossible in practice to precisely control the A/F so as to satisfy exhaust gas regulations.

Therefore, most of the controls necessary for the carburetor, such as A/F control, are performed electronically.
So-called electronically controlled vaporizers (ECCs) have come into practical use.

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 increase system fuel solenoid, 6 is the throttle switch, 7 is the increase system air solenoid, 8 is the intake negative pressure sensor, 9 is a cooling water temperature sensor, 10 is a pulse type rotational speed sensor, 11 is an intake air temperature sensor, 12 is an O ₂ sensor, and 13 is a control unit.

Note that other parts are omitted because they are not particularly relevant to the present invention.

FIG. 2 shows the structure of the carburetor 2 and its accompanying solenoids.

The slow solenoid 3 controls the amount of air supplied to the slow air bleed.
The main solenoid 4 controls the amount of fuel supplied to the main nozzle. Further, the increasing air solenoid 7 controls the amount of air flowing into the bypass air passage for the throttle valve of the carburetor 2, and the increasing fuel solenoid 5 controls the amount of fuel supplied to the bypass air passage. Although it is not shown in Fig. 2, a throttle switch 6 is also provided on the carburetor 2, so that the switch contacts are closed when the throttle valve returns to the fully closed position due to the tension of the return spring. It's summery.

Figure 3 shows the configuration of the control unit 13, which consists of a control logic 14, a microcomputer 15, a ROM 16, a multiplexer 17, an AD converter 18, etc. Load it into the computer 14 and transfer it to the microcomputer 1.
5. The ROM 16 is used to control various actuators associated with the carburetor 2, such as the slow solenoid 3, main solenoid 4, fuel solenoid 5, and air solenoid 7.

At this time, analog data such as data T _W representing the engine temperature from the cooling water temperature sensor 9, intake negative pressure data V _C from the intake negative pressure sensor 8, and _O2 data from the _O2 sensor 12 are sent to the multiplexer 17.
Control logic 1 via AD converter 18
4, and digital data such as data T _HSW from the throttle switch 6 and rotational speed data N from the rotational speed sensor 10 are directly input.

Therefore, in the A/F control device having such a configuration, the A/F is controlled in the steady operating state by controlling the slow and main solenoids 3 and 4 according to various data representing the operating state of the engine. In addition, in the case of warm-up operation, the A/F can be controlled correctly by controlling the increasing solenoids 5 and 7, and the mechanical response part can be controlled correctly. Appropriate A/F control can be performed over all operating conditions with almost no use.

In addition, the opening degree control for these solenoids 3, 4, 5, and 7 is so-called ON/OFF duty control, which is basically operated at a fixed period T, and is ON only for a time t in each period T. That is, a solenoid operates to open the valve, and the degree of opening is controlled by changing the ratio of time t to period T, t/T. Then, (t/T x 100) is called the ON duty, and by changing the ON duty of the slow main solenoids 3 and 4, the A/F is controlled as shown in Figure 4, and the ON duty of the air solenoid 7 is changed. By changing , it is possible to control the engine speed when the throttle valve is in its returned position, as shown in Figure 5.
The A/F at this time can be controlled by the ON duty of the fuel solenoid 5 as shown in FIG.

So-called map control is used for control at this time, and for example, as shown in Fig. 7, when engine speed N and intake negative pressure V _C are given, A/
A memory element is used that can immediately obtain the ON duty value for the slow main solenoid necessary to keep F constant. This is due to the ROM 16 shown in FIG. 3, etc.

By the way, in such ECC, A/
Various types of control are possible, including not only F control, but control that maintains the rotation speed at the target value when the accelerator pedal is not operated, so-called first idle speed control (FISC), idle speed control (ISC), In addition, control functions such as a so-called throttle opener (SOP) are often added to keep the intake negative pressure below the target value regardless of the engine operating state.

Among these, SOP prevents the intake negative pressure from exceeding the target value even if the engine speed becomes higher than the speed corresponding to the throttle valve opening at that time due to engine braking conditions. This function is provided to many ECCs because it is a particularly necessary function for exhaust gas regulations. In general, a throttle opener is a diaphragm drive device that uses intake negative pressure to prevent the throttle valve from immediately returning to the fully closed position when the throttle valve is returned quickly, such as immediately after deceleration. In many cases, this refers to mechanical means to maintain a predetermined opening degree, but the same effect can be obtained by increasing the flow rate of bypass air and the amount of fuel supplied into this bypass air. The control may also be collectively referred to as a throttle opener, and therefore, in this explanation as well, the throttle opener function is described as being performed by the increasing air supply amount control means.

However, the ECC with this SOP function
The F control device has the disadvantage that when the SOP function is activated, a type of hunting occurs in the A/F control operation, causing the A/F to pulsate greatly and worsening the exhaust gas condition, albeit transiently. It was hot.

Additionally, related devices of this type include:
For example, Japanese Patent Application Laid-open No. 130729/1984 can be cited.

An object of the present invention is to provide an ECC A/F control that eliminates the drawbacks of the prior art described above and that does not cause pulsation in the A/F characteristics even when the SOP functions, thereby sufficiently satisfying exhaust gas regulations. We are here to provide you with the equipment.

In order to achieve this object, the present invention is characterized in that the A/F control operation by the slow-main fuel supply amount control means is stopped while the SOP function is operating.

First, before explaining the present invention, it will be explained why large pulsations occur in the A/F control when the SOP function is activated in the A/F control device of the ECC.

FIG. 8 shows changes in engine speed N and changes in intake negative pressure V _C when the SOP function is activated.

In this figure, it is also assumed that the accelerator pedal is released at time _t1 and the throttle valve returns to the fully closed position.

Or suppose that for some reason, for example, the engine brakes.

And, due to any of these causes, negative intake pressure
Suppose that V _C attempts to exceed the target intake negative pressure V _COP set in SOP.

As a result, the SOP function operates at time t ₁ , and the intake negative pressure
Control is applied to prevent V _C from exceeding the target value V _COP .
The intake negative pressure V _C remains constant until time t ₂ , when the engine speed reaches near the idle speed and there is no longer any risk that the intake negative pressure V _C will exceed the target value V _COP .
Control is performed using the SOP function.

Therefore, during this period, the intake negative pressure V _C remains at the target value.
This prevents the exhaust gas condition from deteriorating beyond V _COP .

However, this SOP control is a type of system that measures the intake negative pressure V _C and processes it electronically, thereby controlling the increase system air solenoid 7 to maintain the intake negative pressure V _C at a predetermined value. With feedback control,
Moreover, since the intake negative pressure V _C is a function of the engine speed N, the system that makes up this feedback control includes electronic and mechanical parts, so the control in the mechanical part is difficult. A type of pulsation is almost inevitably induced in the control results due to delays and bumps.

As a result, during the period from time t ₁ to t ₂ , the 8th
As shown in the figure, although the average value of intake negative pressure V _C is maintained at the target value V _COP , the instantaneous value of intake negative pressure V _C shows large fluctuations, accompanied by relatively large pulsations. It becomes a thing.

However, even at this time, the A/F control by the slow main type solenoids 3 and 4 was being carried out, and as mentioned above, the control was based on the map shown in Figure 7, and the engine speed The variables are N and negative intake pressure _Vc .

Therefore, if the intake negative pressure V _C is pulsated by the SOP, pulsations will naturally appear in the A/F control results.

In addition, as is clear from the above explanation,
The SOP is required to operate mainly when the engine is decelerating, and therefore most of the time the engine speed has dropped to relatively close to the idle speed.

However, as is clear from Fig. 7, in this region, that is, in the region where the engine speed N is approaching the idle speed, the A/F is kept at a constant value with respect to changes in the intake negative pressure V _C. Turn on slow main solenoids 3 and 4 required to control
The duty value is changing significantly.

Therefore, even if the pulsation applied to the intake negative pressure V _C by the SOP is not very large, the ON duty values for solenoids 3 and 4 of the slow main system will vary considerably, and furthermore, What is controlled by these solenoids 3 and 4 is the size of the fuel passage, and there is a large time lag before it actually appears as a change in the amount of fuel supplied, so the intake negative pressure V The pulsation of _C does not reflect directly on the amount of fuel supplied, resulting in a kind of hunting condition in the A/F control results.

Therefore, in the conventional A/F control device for ECC, these causes are superimposed, causing large pulsations in A/F control, resulting in deterioration of exhaust gas.

Next, an embodiment of the A/F control device according to the present invention will be described.

FIG. 9 is a flowchart for explaining the operation of one embodiment of the present invention, which is performed by the control unit 13 in the A/F control device shown in FIGS. 1 to 3. 3 shows an A/F control operation according to an embodiment of the present invention.

Therefore, this embodiment also has a carburetor 2, various solenoids 3, 4, 5, 7, a switch 6, various sensors 8 to 12, and a control unit 13, and controls the carburetion according to the operating state of the engine. The point that each solenoid of the device 2 is controlled is the same as in the case of FIGS. 1 to 3, and the point that it has the SOP function is also the same.

Furthermore, the operation according to the embodiment of the present invention shown in FIG. 9 is similar to the other control operations in the apparatus shown in FIGS. It is a type of control, and is executed every predetermined control cycle.

In FIG. 9, when this control program is executed, the ON/OFF state of the throttle switch 6 is checked in the first step.

In a subsequent step, the engine speed N from the sensor 10 is checked and compared to a predetermined speed _NOP, which has a value of, for example, 13,000 rpm, to see N- _NOP .

In the next step, the intake negative pressure V _C is determined and expressed by V _C −V _COPH . This V _COPH is SOP
ΔV _C is added to the target value V _COP set for the target value V COP.

These steps are for determining whether or not to activate the SOP function. If the result in the first step is OFF, it means that the throttle valve has not returned to the return position, that is, the accelerator pedal is not being operated. Therefore, SOP is unnecessary and normal A/F control starts.

When the result is <0 in the second step, it means that the engine speed N immediately before the throttle valve returns is lower than the predetermined value, 1300 rpm, and in practice this is the case. When the throttle valve is returned from a low rotational speed to enter a deceleration state, the intake negative pressure V _C almost never exceeds the target value V _COP , so the SOP is designed to determine this and prevent it from working. be.

The third step, along with the step on the lower right, is a step to check whether the intake negative pressure V _C is within a predetermined range ±ΔV _C with respect to the target value V _COP , and calculates V _C −V _COPH . If this is <0, check V _C -V _COPL in the next step, and if this is <0, the SOP operation will not be entered. where V _COPL
is the target value V _COP minus ΔV _C.

In this way, the operating state of the engine is determined,
When it is determined that the SOP operation is not necessary, that is, when normal A/F control starts to be executed, the program on the right side of FIG.
The ON duty data D _AC is fixed at the previous value, and in the next step it is applied to the air solenoid 7, leaving the air supply amount from the increase system at the previous value. At this time, the value of the data D _AC becomes almost 0 when the engine is in normal operating condition, and shows an appropriate value only during warm-up operation.

In the next step, a map is viewed based on the engine speed N and intake negative pressure V _C and data D _SM necessary to maintain the A/F at a predetermined value is read. This duty D _SM is ON duty data necessary for the slow main type solenoids 3 and 4, and is applied to the slow main actuator, that is, the solenoids 3 and 4 in the next step.

In the next step, data _DRS is obtained from the data _DAC given to the increase air solenoid 7 and the intake negative pressure _VC by looking at a table or map.

Finally, this data _DRS is applied to the increase system fuel solenoid 5, fuel corresponding to the air being supplied by the increase system air solenoid 7 is supplied, and the control cycle is completed. It goes without saying that when the amount of air supplied by the increasing air solenoid 7 is 0, that is, in the normal engine operating range, the data D _SM is also 0.

In this way, when the SOP is not operating, the A/F is controlled to maintain the correct exhaust gas condition.

Now, when time _t1 in Figure 8 is reached and it is determined in the first to third or fourth steps in Figure 9 that SOP operation is required, the SOP control program is executed. to go into.

First, in the third step, V _C −V _COPH is ≧0.
When it is determined that ΔD _AC is the ON duty data D _AC ' for the air increase actuator, that is, the solenoid 7, the data to be given to the air increase system solenoid 7 is calculated in the next step. Determine D _AC and apply it to air solenoid 7 in the next step.

Also, if V _C -V _COPH is <0 in the third step, check V _C -V _COPL in the next step, and only when this is ≧0, in the next step subtract ΔD _AC from data D _AC ' and calculate the data. Determine D _AC and apply it to air solenoid 7 in the next step. In addition,
The data D _AC ' is the ON duty data given to the increase system air solenoid 7 in the control cycle before this control cycle.

Further, at this time, if V _C -V _COPL <0, A/F control in the normal region on the right side is entered, as already explained.

To summarize the control by this part, the intake negative pressure
When V _C is larger than the target value V _COP by more than ΔV _C , the opening rate of the increase system air solenoid 7 is increased to increase the amount of air inflow by an amount equivalent to ΔD _AC , and the intake negative pressure V _C is set to the target value. When the value V _COP is in the range of ±ΔV _C , the opening rate of the increase system air solenoid 7 is decreased by ΔD _AC from the valve opening rate of the data D _AC ′ in the previous control cycle to reduce the amount of air inflow. Make it.

As a result, when the intake negative pressure V _C is larger than V _COP +ΔV _C , the amount of air supplied by the air solenoid 7 is increased little by little each time the control cycle is repeated, and the intake negative pressure V _C becomes V _COP ±ΔV _C
When , the amount of air is decreased one after another, so the intake negative pressure V _C is controlled so that it eventually converges around the target value V _COP , and the SOP function is carried out. Become.

Now, when entering the control program in which SOP control is executed _in this way, the data D _SM is obtained in the next _step . Instead of finding the data D SM ' in the control cycle before this control cycle, the data D _SM ' is taken out as it is as the data D _SM . Then, in a subsequent step, this data D _SM =D _SM ' is applied to the slow main solenoids 3 and 4 to control the amount of fuel supplied.

In addition, in the next step, data D _RS for the fuel solenoid 5 is obtained from the target value V _COP of the intake negative pressure and data D _AC of the air solenoid 7, and in the last step, data D RS for the fuel solenoid 5 is obtained. is set to control the supply of fuel to the increase system.

Therefore, in this part, when the SOP is operating, the ON duty data D _SM to be given to the solenoids 3 and 4 of the slow main system is at time t ₁
Furthermore, at this time, the data D _RS to be given to the fuel solenoid 5 is determined not from the engine's actual intake negative pressure V _C but from the target value V _COP . This means that control is in place.

As a result, in the embodiment of the present invention, SOP
When a relatively large pulsation appears in V _C , the control of the fuel supply amount by solenoids 3 and 4 of the slow main system reduces the intake negative pressure immediately before entering the SOP control _. It will be fixed to the data obtained from the map from V _C and rotation speed N, and the slow main solenoids 3 and 4 will be fixed.
The amount of fuel supplied from the station remains constant.

In addition, at this time, fuel solenoid 5
The data D _RS given to is not calculated from the intake negative pressure V _C which includes pulsation, but from the target value V _COP set in SOP, so this data D _RS Pulsation does not occur, and it is possible to almost completely prevent pulsation from occurring in A/F control.

However, in the present invention, when the SOP is activated and the intake negative pressure control is started, the A/F control is no longer feedback control, and after a long period of time, the A/F control is Although it is possible that the intake negative pressure V _{C exceeds the target value V COP, the situation in which the intake negative pressure V C} exceeds the target value V _COP is limited to a transient state such as when the engine is decelerating; Since the time is actually quite short, deterioration of exhaust gas conditions due to separation of A/F control from feedback control is hardly a problem, and the present invention prevents pulsation in A/F control. The improvement in exhaust gas conditions resulting from this can be said to be extremely significant.

The purpose of the present invention is to provide an A/F control device for a carburetor having an SOP function,
It is clear that this can be achieved by any configuration as long as it stops A/F control by the slow-main fuel supply amount control means when the SOP function is activated, and Fig. 9 is based on this book. This is just one embodiment of the invention.

As explained above, according to the present invention, it is possible to prevent pulsation in the A/F even when the intake negative pressure is controlled by the SOP function in the A/F control device of the ECC. It is possible to provide an A/F control device that can fully comply with exhaust gas regulations, except for the following drawbacks.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an example of a general configuration of an air-fuel ratio control device in an electronically controlled carburetor, Fig. 2 is a sectional view showing an example of the carburetor, and Fig. 3 is an example of a control unit. Block diagram, 4th
The figure is a characteristic curve diagram showing an example of air-fuel ratio control characteristics by a slow main solenoid, Figure 5 is a characteristic curve diagram showing rotation speed control characteristics by an air solenoid, and Figure 6 is a characteristic curve diagram showing air-fuel ratio control characteristics by a fuel solenoid. Figure 7 is a conceptual diagram showing air-fuel ratio control using the map, Figure 8 is a characteristic curve diagram showing changes in rotation speed and intake negative pressure when the throttle opener function is activated, Figure 9 1 is a flowchart showing the operation of an embodiment of the air-fuel ratio control device according to the present invention. 1... Engine, 2... Carburetor, 3... Slow solenoid, 4... Main solenoid, 5... Fuel solenoid, 6... Throttle switch,
7...Air solenoid, 8...Intake negative pressure sensor,
9...Cooling water temperature sensor, 10...Rotation speed sensor,
11...Intake temperature sensor, 12... _O2 sensor, 1
3...Control unit.

Claims (1)

[Scope of Claims] 1. Slow main type fuel supply amount control means, increasing type air supply amount control means for controlling the amount of air flowing in the bypass passage that bypasses the throttle valve, and fuel supply amount to this bypass passage. and a throttle opener function for controlling the intake negative pressure to a predetermined value or less when the throttle valve returns to the fully closed position. In the air-fuel ratio control device for an electronically controlled carburetor, the air-fuel ratio is controlled by the slow main type fuel supply amount control means by detecting the operation of the throttle opener function by the increase system air supply amount control means. A control fixing means for maintaining the control state at a constant state is provided, and when the throttle opener function is activated, the increasing system fuel supply amount control means is controlled by the control amount given to the increasing system air supply amount controlling means, An air-fuel ratio control device characterized in that air-fuel ratio control is performed by controlling according to target intake negative pressure data set for the throttle opener function at this time. 2. In claim 1, the control state maintained by the control fixing means is the control state immediately before the throttle opener function is activated by the increase system air supply amount control means. An air-fuel ratio control device characterized by: