JPH0536614B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an electronic fuel injection control device having a constant speed running control function that maintains a vehicle speed at a set speed by adjusting the amount of air that bypasses the throttle. When the valve is closed and constant speed driving is instructed, the air-fuel ratio is always adjusted to a lean state.

Prior Art and Problems In an electronic fuel injection system that detects the intake air amount A to determine the fuel injection amount F, the air-fuel ratio K is determined during normal control.
= A/F is generally set to 14.5 (stoichiometric air-fuel ratio). However, when the engine condition is stable, the air-fuel ratio K can be set to, for example, 16.5 (lean) to improve fuel efficiency. FIG. 1 is a flowchart in this case, and the "stable engine condition" is determined based on conditions such as the throttle opening being constant, the amount of intake air being constant, and the vehicle speed being above a certain level.

When the above air-fuel ratio switching control is combined with constant speed driving (auto drive) control that maintains the vehicle speed at a set speed, it is determined that the engine condition is stable when driving at a constant speed on a flat road, etc., and automatically shifts to lean control. However, this is not because the constant speed running control necessarily shifted to the lean control, but because each condition was determined to be stable in the engine state as a result of the constant speed running control. Therefore, even during constant speed driving control, the condition of the road surface changes, and for example, the vehicle speed decreases when approaching a hill.In order to compensate for this, a device that automatically increases the throttle opening using a motor etc. Since it cannot be distinguished from the acceleration state caused by normal accelerator operation, it is determined that the engine condition is not stable and returns to normal control (fuel injection amount control at the stoichiometric air-fuel ratio).

The advantage of normal control is that the A/F drops below the lean state, so torque can be increased instantaneously.
The point is that the responsiveness is improved. Therefore, if the vehicle speed decreases, the vehicle speed can be returned to the set speed within a short time. However, this comes at the expense of fuel efficiency. In addition, some drivers often require improved fuel efficiency and smooth driving performance rather than sharp responsiveness. In this case, it is sufficient to prioritize the condition of constant speed driving and always adjust the lean state. However, even when driving at a constant speed, the driver may want to accelerate when overtaking, etc. In this case, it would be possible to temporarily return to normal control without canceling constant speed driving control and improve responsiveness. convenient.

OBJECTS OF THE INVENTION The present invention seeks to provide an electronic fuel injection control device that can meet each of the above demands.

Structure of the Invention The present invention adjusts the intake air amount of an engine through two routes: a throttle valve linked to an accelerator pedal and a bypass air control valve that bypasses the throttle valve, and detects the intake air amount with a sensor. In an electronic fuel injection control device that inputs a signal to an engine control circuit and supplies an amount of fuel proportional to the intake air amount to the engine together with the intake air, the engine control circuit is provided with a signal that inputs a signal to an engine control circuit to supply an amount of fuel proportional to the amount of intake air to the engine. The constant speed driving control is performed by inputting an idle switch signal indicating whether the bypass air control valve is open, and a constant speed driving control signal from the constant speed driving control circuit that controls the vehicle speed to the set speed by adjusting the opening degree of the bypass air control valve. If the throttle valve is fully closed during the engine, lean control is always performed, and if the throttle valve is open even during constant speed driving control, the engine condition is checked and if stable, lean control is performed, and if unstable, theoretical empty is performed. The present invention is characterized in that fuel ratio control is performed, and this will be explained in detail below with reference to the illustrated embodiment.

Embodiment of the invention FIG. 2 is a block diagram showing an embodiment of the invention.
is an air cleaner, 2 is an intake air amount sensor, 3 is a throttle valve linked to an accelerator pedal (not shown), 4 is a bypass air control valve that bypasses the throttle valve, 5 is a surge tank, 6 is an engine,
7 is an exhaust pipe, 8 is a catalyst, 9 is a muffler, 10 is a transmission, 11 is a shaft, 12 is a fuel injection injector, 13 is an engine control circuit, 14 is a constant speed driving control circuit, 15 to 18 are various sensors It is.

The general operation will be explained. Intake air A that has passed through the air cleaner 1 is branched into A ₁ and A ₂ , A ₁ passes through a throttle valve 3 , and A ₂ passes through a bypass air control valve 4 and both enter a surge tank 5 . At this time, the sensor 2 detects the total intake air amount A=A ₁ +A ₂ and inputs the signal to the engine control circuit 13, so the control circuit detects the fuel injection amount F that satisfies the relationship A=K・F. A control signal is given to the injector 12 to obtain the following. In addition to this, the engine control circuit 13 also includes the output of the rotation sensor 15, O ₂
The output of the sensor 16 and the like are input, and various corrections are made to the fuel injection amount F.

Switching between the stoichiometric air-fuel ratio control and the lean control explained in FIG. 1 is one of these, and if the engine condition is determined to be stable from various sensor inputs, the control is switched to the lean control. In other words, by reducing the fuel injection amount F for the same intake air amount A as in the stoichiometric air-fuel ratio control, for example,
= 16.5. However, in the conventional method, the switching of the air-fuel ratio control is determined based only on the engine state, so it does not matter whether the vehicle is running at a constant speed or not. Here, conventional constant-speed running control will be briefly explained.The feature is that the intake air amount control is performed by the throttle valve 3.
In other words, the opening degree of the throttle valve 3, which normally changes in conjunction with the accelerator pedal, is changed by a motor or the like (not shown) during constant speed driving control. This is because the conventional bypass air control valve 4 is formed for idle control and has a narrow flow rate control range, so it cannot be used for constant speed driving control.

Therefore, in the present invention, a bypass air control valve 4 of a variable flow rate characteristic type as shown in FIG. 3 is used to adjust the intake air amount during constant speed running. As a result, the opening degree of the throttle valve 3 can be changed only by the accelerator pedal, so the idle switch (SW) 18 detects whether or not the throttle is fully closed. Here, the fully closed state is a state in which the driver has taken his/her foot off the accelerator, and generally includes idling and constant speed driving. Whether or not the vehicle is in the constant speed running control state is determined by inputting a constant speed running control signal from the control circuit 14 to the engine control circuit 13.

Next, details of each part will be explained with reference to FIGS. 3 to 5. FIG. 3 is a sectional view of a duty control type bypass air control valve that can switch the input/output characteristics of air flow rate into two stages, one of which can be used for idle control and the other for speed control. In the figure, 20
is a metal case, 21 and 22 are fluid conduit sections on the input side (inflow conduit section), 23 is a fluid conduit section on the output side (outflow conduit section), and 24 is a shut-off valve for one inflow conduit section 21. . The valve 24 is composed of a movable part 25, a coil 26, and a return spring 27, and is controlled to be fully open or fully closed depending on whether the coil 26 is energized or not. 28 is the inflow conduit section 21,
A cylindrical movable part that simultaneously contacts the internal opening end of 22 and changes the effective opening area of the opening end,
is a contact surface with the open end, and 30 is a recess for communicating the open end with the outflow conduit portion 23. Reference numeral 31 denotes a coil for continuously changing the amount of movement of the movable portion 28, to which duty control is applied. 32
is a return spring for the movable part 28, 33 is a damper bellows, and 28 to 33 constitute a control valve.

Air A ₂₁ and A ₂₂ obtained by further dividing the bypass air input A ₂ shown in FIG. There is no outflow of bypass air output A ₂₃ from section 23. On the other hand, coil 31
When the movable part 28 is pulled to the right in the figure by applying electricity, an effective opening is created in the inflow conduit section 22, through which the air A ₂₂ flows out to the outflow conduit section 23 side. Since the flow rate of the air A ₂₂ at this time is controlled by the area of the effective opening, and therefore by the fluid resistance, linear input/output characteristics can be obtained by changing the resistance value by duty control. The movable part 28 linearly changes its position from fully closed to fully open by changing the duty of the pulsed current applied to the coil 31 from 0 to 100%, but as shown in the figure, when the shut-off valve 24 is closed, 2, the flow rate of the outflow air A ₂₃ toward the surge tank 5 in FIG. 2 is small. Therefore, this is used to control the rotational speed during idling. On the other hand, the shutoff valve 24
When opened, the outflow air A ₂₃ becomes the sum of the inflow air A ₂₁ and A ₂₂ , so the total amount increases. Therefore, the input/output characteristics at this time are used for speed control during constant speed running.

Fig. 4 shows a specific example of the constant speed running control circuit 14.In addition to the speed signal from the vehicle speed sensor 17 (Fig. 2), the inputs include a manual set switch that instructs constant speed running, and a manual set switch that instructs constant speed running, and when the constant speed is exceeded. There are signals from a chime that issues a speed warning and a manual cancel switch that instructs to cancel constant speed driving. 40 is a D/A converter that converts a pulsed vehicle speed signal into an analog value; when the set switch is turned on when the speed is below a certain level that is not prohibited by the high speed limiter 47, the switch 41 is temporarily closed and the vehicle speed at that time is stored. It is held in circuit 42. This is the set speed V _S that is the control target for constant speed driving, and is compared with the current vehicle speed V at each point in time in the comparator 43 . Reference numeral 45 denotes a self-holding circuit, into which information indicating constant speed running control is set when the set switch is turned on. still,
Low speed limiter 4 is used for constant speed driving below a certain speed.
6 is prohibited.

The duty control circuit 44 outputs a duty pulse (constant period) according to the output of the comparator 43 (difference between the current vehicle speed V and the set speed V _S ), and uses this to control the control valve shown in FIG. 3 . Specifically, the current to the coil 31 is intermittent in accordance with the duty, and the valve opening degree of the control valve and thus the amount of bypass air are controlled so that the input V of the comparator 43 matches the set value V _S . In the present invention, the constant speed driving control signal obtained from the constant speed driving control circuit 14 is applied to the engine control circuit 13 (FIG. 1).

Therefore, the engine control circuit 13 can perform control as shown in FIG. 5 from this constant speed running control signal and the idle SW signal from the idle switch 18. First, it is determined whether the idle SW is on. If it is on, it means either the idle state or constant speed driving control, so constant speed driving control circuit 1
This is distinguished by the signal from 4. As a result, if it is determined that constant speed driving control is in progress, the lean control is shifted to lean control unconditionally, that is, without checking the stability of the engine state. Lean control will continue as long as this condition does not change. As is clear from a comparison with Figure 1,
Conventionally, lean control has not been entered in this manner.

In the present invention, lean control is not simply performed under the condition that constant speed driving control is in progress, but the idle switch on is added as an AND condition. Therefore, when the idle switch is turned off, that is, when the driver depresses the accelerator pedal, the lean control may be released even during constant speed driving control. This is the case when the driver wishes to temporarily accelerate for overtaking or the like even during constant speed driving control. At this time, the same judgment and processing loop as in FIG. 1 is performed. Then, if any of the above-mentioned conditions such as "engine condition is stable" is lacking, the system shifts to stoichiometric air-fuel control to improve responsiveness. It is clear that if the constant speed running control is continued after this, the lean control will return again. In normal driving conditions (not constant speed driving), the control is divided into idle control and normal control depending on whether the idle switch is on or off.

In the embodiment, the engine control circuit and the constant speed running control circuit are shown as separate circuits, but they can also be realized as each function of one microcomputer.

Effects of the Invention As described above, according to the present invention, lean control is continued as a general rule while driving at a constant speed, and even if the speed decreases on the uphill road etc. during this period, the lean control is not automatically canceled. Fuel efficiency during driving can be improved and smooth driving performance can be obtained. Moreover, the responsiveness during that time can be increased at any time by pressing the accelerator pedal when the driver deems it necessary, so there is an advantage that there is no problem with temporary acceleration such as when overtaking.

[Brief explanation of the drawing]

FIG. 1 is a schematic flowchart of engine control in a conventional electronic fuel injection control device, FIG. 2 is a configuration diagram showing an embodiment of the present invention, FIG. 3 is a sectional view showing an example of a bypass air control valve, and FIG. FIG. 4 is a block diagram showing an example of a constant speed running control circuit, and FIG. 5 is a schematic flowchart showing a part of the processing of the engine control circuit of the present invention. In the figure, 2 is an intake air amount sensor, 3 is a throttle valve, 4 is a bypass air control valve, 6 is an engine, 12 is an injector, 13 is an engine control circuit, 14 is a constant speed driving control circuit, 17 is a vehicle speed sensor, 18 is an idle switch.

Claims (1)

[Claims] 1. The intake air amount of the engine is adjusted through two routes: a throttle valve linked to the accelerator pedal and a bypass air control valve that bypasses the throttle valve, and the intake air amount is detected by a sensor and the signal is sent to the engine control circuit. In an electronic fuel injection control device that inputs and supplies an amount of fuel proportional to the intake air amount to the engine together with the intake air, the engine control circuit includes:
an idle switch signal indicating whether the throttle valve is fully closed; and a constant speed driving control signal from a constant speed driving control circuit that adjusts the opening degree of the bypass air control valve to control the vehicle speed to a set speed. If the throttle valve is fully closed during constant speed driving control, lean control will always be performed, and if the throttle valve is open even during constant speed driving control, the engine condition will be checked and stabilized. An electronic fuel injection control device characterized in that it performs lean control if it is unstable, and performs stoichiometric air-fuel ratio control if it is unstable.