JPS628623B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control device for improving starting characteristics in an electronically controlled carburetor of an automobile gasoline engine.

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 idle detection switch, 7 is the throttle actuator, 8 is the intake negative pressure sensor, 9 1 is a cooling water temperature sensor, 10 is a pulse type engine speed sensor, 11 is an intake temperature sensor, 1
2 is a control unit.

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.

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 the bypass air passage provided for the throttle valve 13, and operates as a fuel increasing means for enriching the air-fuel mixture.

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 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, and 20 is a DC motor. Note that 2 is a carburetor, 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.

Furthermore, when the stroke shaft 18 returns to its full capacity and the throttle valve 13 returns to the fully closed position, the idle detection switch 6 (Fig. 1) operates to output the signal T.
_{The HSW} is sent to the control unit 12.

FIG. 4 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
The analog data such as the engine temperature T _W from the water temperature sensor 9 and the engine temperature T W from the idle detection switch 6 are sent via the multiplexer 25 and the analog-to-digital converter 26 to the data T _HSW from the idle detection switch 6, the engine speed N from the rotation speed sensor 10, and the starter. Digital data such as signals K and SW from the switch is input as is into the control logic 22, processed by the microcomputer 23, ROM 24, etc., and is then processed by various actuators such as slow solenoid 3, main solenoid 4, fuel solenoid 5, etc. The throttle actuator 7 and the like are controlled to obtain the optimum A/F according to the operating state of the engine.

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. By controlling the fuel solenoid 5 and the throttle actuator 7 at the same time as controlling the fuel solenoid 5 and the throttle actuator 7, it is possible to control the rich air-fuel mixture required at the time of starting cranking to an optimal state.

At this time, the opening degree control for these solenoids 3, 4, and 5 is so-called ON/OFF duty control, which is basically operated at a fixed period T, and is turned ON for a time t at each period T, that is, The solenoid is opened, and the degree of opening is controlled by changing the ratio of time t to period T, t/T. And (t/T×100) is called ON duty, slow and main solenoid 3,
By controlling the ON duty of fuel solenoid 5, the A/F can be controlled by the slow main system as shown in Figure 5, and by changing the ON duty of fuel solenoid 5, the A/F can be controlled from the increasing system as shown in Figure 6. Because it is possible to control the amount of fuel supplied,
The control unit 12 can control the A/F.

Also, so-called map control is used for control at this time, and this map is a kind of memory device consisting of a ROM 24, and for example, as shown in FIG. 7, the engine speed N and intake negative pressure V _C The corresponding values are memorized in advance so that when given, the ON duty required for the slow main solenoid required to keep the A/F constant can be obtained. A/
F control can be performed easily and accurately.

By the way, in conventional mechanical vaporizers,
The so-called chiyoke system is used as a starting correction device during engine starting cranking, which uses a chiyoke valve to increase the negative pressure in the fuel supply system in the carburetor.
This is a method of forcibly sucking out more fuel,
The correction for cranking and firing during startup is a method called complete explosion correction, in which when the intake negative pressure reaches a predetermined value or higher, the choke valve is opened and the negative pressure in the fuel supply system is slightly lowered. was.

However, one of the features of the above-mentioned ECC is that it can perform various functions electronically without providing an extra control mechanism in the mechanical part of the carburetor body, so a starting correction device is required. In this case, the throttle valve 13 determines the amount of air supplied, and the fuel solenoid 5 determines the amount of fuel supplied to perform starting correction, and additional mechanical control members such as a choke valve are used. It is customary not to use it, and as a result, an A/F control device with start correction that fully utilizes the characteristics of ECC has been obtained.

In this above-mentioned device, during starting cranking, the engine temperature T _W from the cooling water temperature sensor 9 is
The throttle valve opening degree is set by the actuator 7 according to the amount of air, so that the required amount of air supply can be obtained. At this time, the throttle actuator 7 is controlled by using the DC motor 20 like a pulse motor, supplying pulses of a constant width to rotate the DC motor 20 by a constant number of rotations each time. Therefore, as shown in FIG. 8, the opening degree of the throttle valve 13 is controlled by the number of pulses P _UTH supplied to the DC motor 20.

However, since rotational phase control of the DC motor 20 is not possible, such control may cause the throttle valve to change due to fluctuations in the power supply voltage or changes in the frictional force in the drive section of the actuator 7 and the bearing section of the throttle valve 13. Although there are variations in the opening degree of 13, and the characteristics are as shown in Figure 8 on average, each time the control is performed,
Only slightly different degrees of opening can always be obtained.

At this time, the opening degree of the throttle valve 13 determines the characteristics of the engine speed N and intake negative pressure V _C at the time of starting cranking as shown in FIG. If the engine speed cannot be controlled accurately, the rotational speed N and intake negative pressure _Vc cannot be controlled accurately either.

On the other hand, during start-up cranking, fuel is supplied from the fuel solenoid 5, but the fuel supplied by the fuel solenoid 5 is of a negative pressure type, as in the case of a slow main system, that is, it is sucked out by negative intake pressure. In addition, unlike the slow main type, the influence of the negative intake pressure V _C is extremely large, as shown in Fig. 6. Therefore, if the intake negative pressure V _C cannot be controlled accurately as described above, the fuel solenoid 5
The problem is that the amount of fuel supplied by the engine is inaccurate and sufficient starting correction cannot be obtained.

In addition, in the above device, the engine temperature T
The opening degree of the throttle valve 13 is set from _W (by using a table, etc.), but the engine speed N relative to the opening degree of the throttle valve 13 is not necessarily uniquely determined as shown in FIG. It changes depending on the voltage supplied to the motor and the condition of the engine oil.

Therefore, even if the throttle valve opening is set based on the engine temperature T _W , the predetermined engine speed N,
Furthermore, since there is no guarantee that a predetermined intake negative pressure V _C will be obtained, the above-mentioned device has the disadvantage that starting correction cannot be obtained correctly from this point of view as well, and the starting characteristics are not good.

Additionally, related devices of this type include:
For example, Japanese Patent Application Laid-Open No. 48-21032 can be mentioned.

An object of the present invention is to eliminate the drawbacks of the prior art described above, and to provide an A/F with start correction for ECC that enables accurate start correction at all times and provides sufficient starting characteristics.
Provides control equipment.

In order to achieve this object, the present invention is characterized in that the throttle valve actuator during startup cranking is controlled using an intake negative pressure target.

Embodiments of the A/F control device with start correction according to the present invention will be described below with reference to the drawings.

As already explained, A/F control in the ECC is performed by the control unit 12, and the control is executed as one of the programs of the microcomputer 23 included therein.

The A/F control device with start correction according to the present invention is also configured as one of the controls performed by the control unit 12, and one embodiment thereof will be described below with reference to the flowchart of FIG. This will be explained using a chart.

This control program is executed every 40ms, for example, and when this program starts running, it first determines whether the starter switch is ON or OFF from the data K and SW, and if it is ON, that is, during starting cranking. If it is determined that V _C -V _CR <0 is checked in the next step. Here, V _CR is the value of the intake negative pressure that is unlikely to be reached at the time of starting cranking and will naturally be reached when the engine fires, for example.
The negative pressure value is about 200mmHg.

Therefore, if the result in this step is YES, that is, the intake negative pressure V _C has not reached 200 mmHg, this indicates that the engine has not started yet, so proceed to the next step and check the output from the cooling water temperature sensor 9. The engine temperature T _W is taken in, and in the following step a table is entered to look at the target intake negative pressure V _CT for the data T _W . Engine temperature T _W at this time
The characteristics of the intake negative pressure target value _VCT relative to the target value VCT are set, for example, as shown in FIG.

The next two steps are steps for controlling the throttle valve actuator 7 so that this target negative pressure V _CT is achieved. First, V _C - V _CT ≧0.
is checked, and if this is YES, it means that the intake negative pressure V _C is equal to or larger than the target value V _CT , so in the next step, a predetermined number of positive pulses P _UTH are supplied to the motor 20 of the actuator 7. , open the throttle valve 13 a little.

Also, when V _C −V _CT ≧0 becomes NO,
Since this indicates that the intake negative pressure V _C has not reached the target value V _CT , in the next step a predetermined number of negative pulses P _UTH are supplied to the motor 20 to slightly close the throttle valve 13 .

This series of controls is repeated at 40ms intervals every time this program is executed, so the throttle valve 13 is controlled so that the intake negative pressure V _C converges to the target value V _CT . It depends on the opening degree,
The intake negative pressure V _C is always kept very close to the target value V _CT .

In the last step, the fuel solenoid 5 is turned ON based on the target intake negative pressure _VCT using the table.
The duty is determined, the fuel solenoid 5 is controlled to supply a predetermined amount of fuel, and one cycle of the control program is completed.

Next, go back to the beginning of this control program and
When looking at the data K/SW from the starter switch, it is determined that it is OFF, that is, starting cranking is not being performed, and when V _C - V _CR <0 becomes NO in the next step. In other words, when it is determined that the engine is ignited and is generating its own torque (this is the so-called complete explosion state), control to bring the intake negative pressure V _C to the target value V _CT is not entered. The so-called idle speed control operation N F/B, which is shown on the right, starts control execution and keeps the idle speed at a predetermined value, and the so-called throttle opener, which prevents the intake negative pressure from reaching a predetermined value or more. When the control SO is executed, the throttle valve actuator 7 is controlled thereby, and one cycle of the control program is completed.

As a result, in the embodiment of the present invention, even if there is variation in the opening degree setting operation of the throttle valve 13 by the throttle valve actuator 7, the variation occurs in the repeated control before it becomes a large change in the intake negative pressure _Vc . Therefore, it is converged and has almost no effect on the control of the intake negative pressure V _C with respect to the target value V _CT .
The correct intake negative pressure V _C is always obtained, and the control of the fuel supplied by the fuel solenoid 5 is performed accurately, making it possible to provide the A/F necessary for starting with sufficient accuracy. Therefore, it is possible to always obtain good starting correction characteristics for starting the engine.

Further, at this time, there is no need to know the opening degree of the throttle valve 13 by the actuator 7 in order to control the intake negative pressure V _C and maintain it at the target value V _CT .
In order to control the intake negative pressure V _C to the target value V _CT , the throttle valve 13 is opened or closed from that state based on the relationship between the actually measured intake negative pressure V _C and the target value V _CT . Therefore, it is not necessary to know the opening degree of the throttle valve 13.

However, in order to set the opening degree of the throttle valve 13 from the engine temperature like in the conventional device, control cannot be performed unless the opening degree of the throttle valve 13 is known. The normal actuator 7 is not equipped with a throttle valve opening sensor.

Therefore, in the conventional device, for example, the actuator 7 is operated while checking the data T _HSW from the idle detection switch 6, and the throttle valve 13 is in the fully closed position (as shown in FIG. 8) until a signal from the data T _HSW is obtained. The operation is complicated because a so-called initializing operation is required, in which the actuator 7 is returned to its original position until it returns to T _Hio ), and then a predetermined number of pulses P _UTH are supplied to open the throttle valve 13 to a predetermined position. However, according to the embodiment of the present invention, such a drawback can be eliminated unless a throttle valve opening position sensor is provided to eliminate this problem.

In addition, during start-up cranking, the value of intake negative pressure V _C tends to pulsate greatly due to the mechanical resistance of the engine, which may cause control operation to become _unstable . For example, by setting a hysteresis or dead zone to determine the magnitude relationship between the intake negative pressure V _C and the target value V _CT , for example, V _C - V _CT
≧0 as V _C -V _CT ≧±ΔV _C and not applying the pulse P _UTH to the actuator 7 during this ±ΔV _C , either method can be said to be effective. . Similarly, the target value V CT varies depending on whether the intake negative pressure V _C decreases toward the target value V _CT or increases toward the target value V _CT.
Hysteresis may be provided by changing the value of .

In the above embodiment, the target intake negative pressure V _CT was determined from the engine temperature T _W and the intake negative pressure V _C was controlled using this as the target, but as is clear from Fig. 9, the same throttle valve Engine rotation speed N for opening degree
Since there is a one-to-one correspondence between the engine temperature T _W and the intake negative pressure V _C , the target rotation speed N _T is given in the table from the engine temperature T W and the throttle valve actuator 7 is adjusted so that the engine rotation speed N converges to the target value N _T . May be controlled.

In this case, in the flow chart of FIG. 11, instead of the step of determining V _C -V _CT ≧0, N-
The motor 2 of the actuator 7 determines that N _T ≧0.
Needless to say, it is only necessary to provide a step of setting the pulse P _UTH to 0.

As explained above, according to the present invention, the necessary fuel is always accurately supplied even during start-up cranking, and additional operations such as initialization are not required for control, so the configuration is simple.
It is possible to provide an A/F control device with starting correction that always performs correct starting correction and has good engine starting characteristics, excluding the drawbacks of the prior art.

[Brief explanation of the drawing]

Fig. 1 is a schematic block diagram showing an example of an air-fuel ratio control device using an electronically controlled carburetor, Fig. 2 is a sectional view showing an example of the carburetor, and Fig. 3 is a schematic diagram showing an example of a throttle actuator. Figure 4 is a block diagram showing the configuration of the control unit, Figure 5 is a block diagram showing the configuration of the control unit.
Figure 6 is a characteristic diagram showing the air-fuel ratio control characteristics by the slow main solenoid, Figure 6 is a characteristic diagram showing the air-fuel ratio control characteristics by the fuel solenoid, Figure 7 is a conceptual diagram showing the setting of data using a map, and Figure 8 is a characteristic diagram showing the air-fuel ratio control characteristics by the fuel solenoid. A characteristic diagram showing the control of the throttle valve opening by the throttle actuator. Figure 9 is a characteristic diagram showing the rotational speed and intake negative pressure during engine startup cranking. Figure 10 is a characteristic diagram showing the intake negative pressure from the engine temperature. FIG. 11 is a flowchart showing the operation of an embodiment of the air-fuel ratio control device with starting correction according to the present invention. 1... Engine, 2... Carburetor, 3... Slow solenoid, 4... Main solenoid, 5... Fuel solenoid, 6... Idle detection switch, 7... Throttle actuator, 8... Intake Negative pressure sensor, 9...Cooling water temperature sensor, 10...
Pulse type engine speed sensor, 11... Intake temperature sensor, 12... Control unit, 13...
... Throttle valve, 14... Throttle valve shaft, 15... Opening/closing lever, 16... Return lever, 17... Return spring, 18... Stroke shaft, 19... Reduction gear, 20... DC motor.

Claims (1)

[Scope of Claims] 1. In an air-fuel ratio control device with start correction having an actuator means for controlling the return position of a throttle valve and a fuel increase means for enriching the air-fuel mixture, an engine start cranking state is detected. means and
The storage means provides predetermined target data required during engine starting cranking, and a sensor detects engine intake negative pressure or data related thereto, and the engine intake negative pressure is provided from the storage means during engine starting cranking. An air-fuel ratio control device with starting correction, characterized in that starting characteristics are improved by controlling the actuator means so as to reach a predetermined target value based on the obtained target data. 2. The air-fuel ratio control with starting correction according to claim 1, characterized in that the storage means is constituted by a storage means that inputs data representing engine temperature and provides target intake negative pressure data as a function thereof. Device. 3. The startup correction according to claim 1, characterized in that the increased fuel supply amount by the fuel increase means is controlled in accordance with the target intake negative pressure given by the storage means. Air-fuel ratio control device.