JPH0247580B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an electronically controlled fuel injection system, and more particularly to an improvement in fuel injection cut control thereof.

Prior Art and Problems In general, in conventional electronically controlled fuel injection systems, if the throttle valve is fully closed for a certain period of time, e.g. 0.5 seconds or more, and the engine speed is a certain value, e.g. 900 rpm or more, fuel is injected. It is being done to stop (cut). This is to prevent heating of the catalytic converter, but for this reason, in a system where such an electronically controlled fuel injection device and a so-called constant speed cruise control device coexist,
When driving down a long downhill slope during constant speed driving control, the fuel injection cut and injection restart are repeated at short intervals, resulting in intermittent shocks that result in poor ride comfort.

FIG. 1 is a diagram for explaining this problem, and shows an example of temporal changes in vehicle speed, throttle opening, and fuel injection cut state of the electronically controlled fuel injection device with respect to the vehicle speed setting a of constant speed cruise control. This is what is shown. On a long downhill slope, it is necessary to fully close the throttle opening in order to maintain the set vehicle speed a, and if the throttle opening is fully closed for a certain period of time, the electronically controlled fuel injection system detects this with a sensor. to cut fuel injection. Therefore, the speed of the car decreases quickly. When the traveling vehicle speed reaches a certain value below the set speed, the throttle opening becomes large again, and when the throttle opening is no longer zero, the electronically controlled fuel injection device resumes fuel injection. When this injection is resumed, torque is suddenly generated, causing a shock. When injection is restarted and the throttle opening gradually increases until the traveling vehicle speed reaches a certain value above the set vehicle speed, the throttle opening becomes smaller again, and if the target speed cannot be maintained, the throttle opening is fully closed. and fuel injection is also cut off. The cycle of fuel cut and restart is as follows:
In a conventional system that combines an electronically controlled fuel injection device and a constant speed cruise control device, the time required is very short, for example, about 10 seconds. For this reason, as mentioned above, the intermittent shocks are repeated at short intervals, resulting in extremely poor ride comfort.

As a means to solve this problem,
As shown in Japanese Patent No. 28931, there is a system that prohibits fuel cut during constant speed driving control. According to this, the shock does not occur at all, so deterioration of ride comfort can be prevented. However, during constant speed driving control, even if the throttle opening is fully closed, fuel continues to be supplied, so the vehicle speed does not decrease on long downhill slopes, and the deviation from the target vehicle speed only increases. It loses its meaning as a traveling device.

Purpose of the Invention The present invention has been made to solve such technical problems, and its purpose is to solve the above-mentioned problems in a system where a constant speed cruise control device and an electronically controlled fuel injection device coexist. To prevent deterioration of riding comfort on long downhill slopes and to enable constant speed driving around a target vehicle speed even on long downhill slopes.

Embodiments of the Invention FIG. 2 is a block diagram of essential parts showing an example of the hardware configuration of a system including the electronically controlled fuel injection device of the present invention. In the figure, reference numeral 10 denotes a control section of the electronically controlled fuel injection system, which includes a microcomputer 11, an input interface circuit 13 connected to it via a bus 12, a ROM 14 for storing programs, etc., and a ROM 14 for temporarily storing calculation results, etc. It consists of a RAM 15 for storage, an A/D converter 16 for converting analog signals into digital signals, an output interface circuit 17, and a constant voltage power supply 18. The input interface circuit 13 includes an output signal from a crank angle sensor provided in the distributor 19 that detects the crank reference position, rotation angle, and cylinder position, and a throttle opening sensor 20 that detects the opening of the throttle valve. , the output signal of the O ₂ sensor 21 that detects the oxygen concentration in the exhaust pipe, the output signal of the detection starter 22 that detects when the engine is starting, the output signal of the vehicle speed sensor 23 that detects the current vehicle speed, and the constant speed driving control. A signal from the device 28 indicating that constant speed running control is being applied is added to each of the vehicles. The A/D converter 16 includes an intake temperature sensor 25 that detects the output voltage of the battery 24 and the intake air temperature.
The output signal of the aeroflow meter 26 which detects the amount of intake air is added. Further, the output of the output interface circuit 17 is connected to an injector 27.

The constant speed cruise control device 28 uses a vehicle speed sensor 23 to detect and store the traveling vehicle speed of the automobile when a switch generally called a set switch is operated, and compares the subsequent traveling vehicle speed with the stored vehicle speed and controls the throttle valve using an actuator 29. By automatically adjusting the opening degree, the vehicle speed is controlled to be maintained at a desired value without the driver having to press the accelerator pedal, and its configuration is well known. In the present invention, a signal indicating that constant speed driving control is currently being performed is taken from the constant speed driving control device 28, and is inputted to the input interface circuit 13 of the electronically controlled fuel injection device as described above.
For example, the output of a self-holding circuit in the constant speed cruise control device can be used as the signal indicating that the constant speed cruise control is in progress.

Microcomputer 11 is A/D converter 1
6. Various signals from the input interface circuit 13 are read, known calculations are executed, and fuel is injected from the injector 27 via the output interface circuit 17 only at the timing and period determined by the calculation. Since such normal fuel injection control is well known, detailed explanation thereof will be omitted. In the present invention, in addition to such normal control, fuel injection cut determination is performed at certain intervals.

FIG. 3 is a flowchart showing an example of the fuel injection cutoff determination process, which is a process in which fuel cutoff is prohibited during the above-mentioned constant speed running control. S1 to S4 indicate each step. Microcomputer 11
is a signal indicating that the throttle opening sensor 20 is fully closed (generally an ON signal of the idle contact) for a predetermined period of time.
S
1, S2, if the condition is not met, the fuel injection cut determination process is terminated. The above conditions are the same as those conventionally used. If the above conditions are satisfied, the microcomputer 11 next determines whether or not a signal indicating that constant speed driving control is being inputted from the constant speed driving control device 28 is S3. Then, if the condition is not satisfied, the determination process is ended, and if the condition is satisfied, fuel injection cut is executed at S4. Therefore, when driving down a long downhill slope, even if the other conditions for fuel injection cut are satisfied, if constant speed driving control is in progress, injection cut will not be performed, and the fuel injection will not be cut due to repeated stopping and restarting of fuel injection. Since the shock is prevented from intermittent, the riding comfort can be improved. However, on the other hand, as mentioned above, on a long downhill slope,
Constant speed driving control centered around the target vehicle speed cannot be performed.

FIG. 4 is a flowchart showing another example of the fuel injection cut determination process according to the present invention. The difference from FIG. 3 is that step S5 is added, and step S3 determines that constant speed driving control is in progress. The purpose of this is to reduce the fuel injection amount to a certain value when the combustion condition occurs, resulting in a so-called lean combustion state. In this way, it is possible to perform constant speed driving control centered on the target vehicle speed, and the repetition of fuel injection cut and restart during constant speed driving control, which was conventionally performed, is replaced by a repetition of fuel injection amount reduction and return. , the torque fluctuation can be reduced by that much, so the shock can be softened. Furthermore, since the rate of decrease in vehicle speed when the fuel injection amount is reduced is smaller than the rate of decrease in vehicle speed when fuel is cut in the conventional case, the period in which fuel cut occurs becomes longer, and the number of times a shock occurs is reduced. Note that a specific method for reducing the fuel injection amount may be to reduce the injection amount correction coefficient.

FIG. 5 is a flowchart showing an example of fuel injection cut determination processing according to the present invention, and shows steps S10 to S1.
5 indicates each step. The present invention provides two times for the throttle valve to be fully closed, which is a condition for fuel injection cut. When the vehicle is not under constant speed driving control, it is set to 0.5 seconds, as in the conventional case, and in steps S10 and S11, when it is not under constant speed driving control. When is longer, for example 1 to 10
Steps S10 and S1 that take about seconds
2. In this way, even if the throttle valve is fully closed, the fuel injection cut is not executed immediately, so it is possible to lengthen the cycle of fuel injection cut and restart on long downhill slopes, and the number of shots is reduced. Riding comfort can be improved and constant speed driving control centered around the target vehicle speed can be performed.

Incidentally, by combining FIGS. 5 and 4 and replacing step S15 in FIG. 5 with steps S3 to S5 in FIG. 4, it is possible to further lengthen the repetition period of fuel injection cut and restart.

Effects of the Invention As explained above, the present invention provides an electronically controlled fuel injection device that cuts fuel injection when the throttle valve is fully closed and the engine speed remains at a predetermined number or more for a predetermined time or more. means for detecting whether constant speed driving control is being performed; and depending on whether constant speed driving control is being performed, the predetermined time is set to a larger value during constant speed driving control than when not being under constant speed driving control; Since a change means is provided to change the fuel injection, the fuel injection does not have to be cut and restarted in a short period like in the past, even when going down a long downhill slope during constant speed driving control, making it possible to improve ride comfort. In addition, constant-speed driving control centered around the target vehicle speed can be performed.

[Brief explanation of the drawing]

Fig. 1 is a diagram for explaining the problems of the conventional system, Fig. 2 is a block diagram of main parts showing an example of the hardware configuration of a system including the electronically controlled fuel injection device of the present invention, and Fig. 3 is a diagram for explaining the conventional problems. FIG. 4 is a flowchart showing an improved fuel injection cut determination process, and FIG. 5 is a flowchart showing an embodiment of the present invention. 10 is a control unit of an electronically controlled fuel injection device, 11 is a microcomputer, 19 is a distributor with a built-in crank angle sensor, 20
28 is a throttle opening sensor, and 28 is a constant speed traveling control device.

Claims (1)

[Claims] 1. In an electronically controlled fuel injection system that cuts off fuel injection when the throttle valve is fully closed and the engine speed remains above a predetermined number for a predetermined period of time or more, it is detected whether constant speed running control is in progress. and changing means for changing the predetermined time to a larger value during constant speed driving control than when not under constant speed driving control, depending on whether constant speed driving control is being performed. Electronically controlled fuel injection system.