JPH0344929B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a constant speed traveling device for an automobile.

Conventional technology and problems Conventionally, in a system that combines a constant speed vehicle for automobiles and an electronically controlled fuel injection device (hereinafter referred to as EFI) that stops fuel injection when the throttle opening is approximately zero, When the vehicle goes down a long slope during high-speed driving control, fuel injection is stopped and restarted repeatedly at short intervals, resulting in intermittent shocks that make the ride less comfortable.

Fig. 1 is a diagram for explaining this problem, and shows the traveling vehicle speed, throttle opening, and period during which the fuel injection output from the EFI is stopped relative to the set vehicle speed a of the constant speed cruise control as a logic "1". This figure shows an example of a temporal change in the fuel cut signal (hereinafter referred to as F/C signal) shown in FIG. On a long downhill slope, in order to maintain the set vehicle speed a, the throttle opening must be fully closed. When the throttle opening is fully closed, the EFI detects this with the throttle opening sensor and injects fuel. is cut only during the fully closed period. Therefore, the speed of the car decreases quickly. When the vehicle speed reaches a certain value below the set speed, the throttle opening increases again, and when the throttle opening is no longer approximately zero, the EFI resumes fuel injection. When this injection is restarted, a shock occurs because a large acceleration is temporarily generated. When injection is restarted and the throttle opening gradually increases until the traveling vehicle speed reaches a certain value above the set speed, the throttle opening becomes smaller again, and if the target speed cannot be maintained, the throttle opening becomes full. It is closed and fuel injection is also cut off. In the conventional constant speed driving system for automobiles, this cycle of fuel cut and restart is very short, for example, about 10 seconds. For this reason, as mentioned above, intermittent shots are repeated in short cycles,
It made the ride very uncomfortable.

OBJECT OF THE INVENTION The present invention has been made to improve these conventional drawbacks.The purpose of the present invention is to make the repetition cycle of fuel cut and restart as long as possible on long downhill slopes so as not to cause discomfort to the driver. The purpose is to improve riding comfort.

The structure of the present invention is as shown below. That is, the present invention provides constant-speed driving for automobiles in which the opening degree of a throttle valve is controlled by a control signal generating means that generates a control signal for driving an actuator according to the difference between a detected traveling vehicle speed and a preset set vehicle speed. In the apparatus, the control signal generating means generates two control signals, a first control signal generating means having a large control gain and a second control signal generating means having a small control gain with respect to a unit change in the difference between the set vehicle speed and the traveling vehicle speed. and selecting the second control signal generating means for a predetermined period longer than the generation period of the fuel cut signal every time a fuel cut signal indicating that fuel injection has been stopped is received from the electronically controlled fuel injection device. The present invention constitutes a constant speed traveling device for an automobile characterized by being provided with a time limit means.

Embodiment of the Invention FIG. 2 is a block diagram of essential parts of an embodiment of the constant speed traveling device for automobiles of the present invention.

In the figure, 10 is a reed switch for detecting the speed of an automobile, and 11 is a permanent magnet rotated by a speedometer cable. The reed switch 10 turns on and off as the permanent magnet 11 rotates, and generates a pulse signal having a frequency proportional to the vehicle speed. This pulse signal is converted into a DC voltage having a level proportional to the vehicle speed in a frequency-voltage conversion circuit (F/V conversion circuit) 12. F/V conversion circuit 1
The output voltage of 2 is held in the memory circuit 14 when the analog switch 13 is on. The set voltage held in the memory circuit 14 is input to the differential amplifier 15, where the difference between it and the output voltage of the F/V conversion circuit 12, that is, the running vehicle speed is determined. This difference signal is
The signal is input to either the first pulse generating circuit 17 or the second pulse generating circuit 18 via the changeover switch 16. The changeover switch 16 is a time limit circuit 30
When the output is "0", it is set on the upper side, that is, on the first pulse generation circuit 17 side, and when it is "1", it is set on the lower side, that is, on the second pulse generation circuit 18 side. The time limit circuit 30 normally has an output of "0" and is triggered by the rise of its input signal ("0" → "1"), and sets its output to "1" for a predetermined period of time. It has a so-called retriggerable function in which when the input signal rises, it is triggered again at that point and the output is set to "1" again for a predetermined time from that point.

On the other hand, the EFI (not shown in Fig. 2) detects whether the throttle opening is fully closed or not. When it detects that the throttle opening is fully closed, it sends an F/C signal (“1”) to stop the fuel supply for that period. Output. That is, the F/C signal is normally "0" and becomes "1" while the throttle is fully closed. This F/C signal is supplied as an input signal to the time limit circuit 30.

In both the first and second pulse generation circuits 17 and 18, when the vehicle speed corresponding voltage is higher than the set voltage, the energization time to the control valve 19a of the actuator 19 becomes shorter, and in the opposite case, the energization time becomes shorter. Pulse-like outputs of "1" and "0" are generated with the duty ratio controlled so as to be longer, but the change gains of the duty ratio with respect to the difference between the traveling vehicle speed and the set vehicle speed (referred to as vehicle speed difference) are different from each other. In other words, as shown in FIG. 3, for example, the first pulse generating circuit 17 has a duty ratio of 0% when the vehicle speed difference is -20 km, a duty ratio of +
The duty ratio is 100% at 20 km, and the duty ratio changes almost linearly during that time, whereas the second pulse generating circuit 18 has a characteristic that the duty ratio changes almost linearly during that time. The duty ratio is 0% when the vehicle speed difference is +40km, and the duty ratio is 100% when the vehicle speed difference is +40 km, and the duty ratio changes almost linearly during that time.

The actuator 19 includes a control valve 19a and a release valve 19b. The opening and closing of the control valve 19a is controlled by the output of the amplifier 20. When energized, the atmospheric pressure from port 19c is cut off and intake pipe negative pressure from port 19d is introduced into chamber 19e. When energized, negative pressure from port 19d is cut off and the intake pipe negative pressure is introduced into chamber 19e. Atmospheric pressure from 19c to chamber 19e
to be introduced. The release valve 19b is controlled to open and close by the output of the self-holding circuit 22 via the amplifier 21, and when energized shuts off atmospheric pressure from the port 19f.
When the current supply is cut off, this atmospheric pressure is introduced into the chamber 19e. As described above, by controlling the pressure in the chamber 19e, the diaphragm 19g moves, thereby moving the load 19h connected to the accelerator link (not shown) in its axial direction, and as a result, the throttle valve opens. degree is controlled.

Further, an AND circuit 25 is provided which receives the output of the set switch 23 and the output of the high-speed limiter circuit 24, and the output of the AND circuit 25 closes the analog switch 13 and presets the self-holding circuit 22. When the self-holding circuit 22 is preset, the AND circuit 26 is opened and the release valve 19b is energized through the amplifier 21, so that travel control becomes possible. High speed limiter 24
This is to prohibit the setting of constant speed driving when the vehicle speed is in a high speed range (for example, over 100 km).

In operation, the high-speed limiter 24 operates when the vehicle speed is 100.
Km or more (When the vehicle speed exceeds 100 Km, a warning chime signal is output, so this chime signal is used as a substitute in this embodiment.) When the vehicle speed is less than 100 Km, the output is set to "1". When the vehicle exceeds 100km, the output is set to "0". Therefore, the vehicle speed
If the distance is less than 100km, the AND25 is open.
When the set switch 23 is operated at this time, the output of the AND 25 changes and the self-holding circuit 22 is set, and at the same time, the analog switch 13 is closed, the current vehicle speed is stored in the memory circuit 14, and constant speed running is started. However, if the vehicle speed is over 100 km,
Since AND25 is closed, set switch 2
Even if 3 is operated, the output of AND 25 does not change, self-holding circuit 22 is not set, and analog switch 13 is not closed, so constant speed running is not started. Further, the cancel switch 28 is a switch that resets the self-holding circuit 22, and when reset, the self-holding circuit 22 stops supplying current through the amplifier 21. The resume switch 27 is used to restart the constant speed running control that was interrupted by the cancel switch 28, and when it is pressed, constant speed control is performed with the originally set vehicle speed as the target value. The constant speed limiter circuit 29 is for forcibly resetting the self-holding circuit 22 when the vehicle speed decreases to 30 km or less, for example.

In the above configuration, by pressing the set switch 23, the output of the F/V conversion circuit 12 is stored in the storage circuit 14 via the analog switch 13, and constant speed running control is performed at this set speed.
When the vehicle is traveling on a flat road, fuel cut is not performed in the EFI, so the F/C signal is "0" and the changeover switch 16 is set to the first pulse generation circuit 17 side. Therefore, the so-called gain of constant speed running control is large, and speed control with good responsiveness is executed. On the other hand, when a fuel cut is executed in the EFI due to a long downhill slope, the time limit circuit 30 is activated by the F/C signal.
The changeover switch 16 is set on the second pulse generation circuit 18 side.

FIG. 5 shows an example of temporal changes in the traveling vehicle speed, throttle opening, F/C symbol, and output of the time limit circuit 30 with respect to the set vehicle speed a when the second pulse generation circuit 18 is selected. .

In FIG. 5, when the vehicle approaches a long downhill slope during constant speed control, the vehicle speed increases and the throttle opening decreases accordingly. Eventually, when the throttle is fully closed, the EFI outputs an F/C signal (“1”), and at this rising edge, the timer circuit 30 is triggered and its output is set to “1”, causing the low gain second pulse generating circuit 18 Select. When performing F/C, the vehicle speed decreases, but the throttle opens accordingly.
The EFI detects this, stops outputting the F/C signal (to "0"), and resumes fuel supply. A shock occurs at this time. (Therefore, the F/C signal remains "1" while the throttle is fully closed, and becomes "0" when the throttle opens, so it is in a pulse form.)
When the fuel supply is resumed, the vehicle speed increases again, but
Since the low gain second pulse generation circuit 18 is selected, the vehicle speed gradually increases, and the throttle opening degree also gradually decreases accordingly. Eventually, when the throttle is fully closed again, as mentioned above,
F/C signal “1” is output from EFI.

On the other hand, the timer circuit 30 is triggered by the first F/C signal and outputs "1" for a predetermined time, but this predetermined time is the generation cycle of the F/C signal (period from one rising edge to the next rising edge). (for example, about 60 seconds), the output of the timer circuit 30 still maintains the "1" state when the next F/C signal is output, and therefore this F/C signal Retriggered by C signal.

Thereafter, the above phenomenon is repeated as long as the downhill slope continues, but during that time the time limit circuit 30 continues to output "1" by retriggering by the F/C signal and continues to select the low gain second pulse generation circuit 18. For,
Changes in vehicle speed and changes in throttle opening become gradual, and the period in which the F/C signal is generated becomes longer. In other words, the period of occurrence of shots becomes longer. Therefore, the second pulse generating circuit 18 is always selected while driving down a long downhill slope, and the number of repetitions per unit time of fuel cut and restart can be reduced compared to the conventional method. Since the number of times is also reduced, it is possible to improve riding comfort.

Further, it is clear that the same effect can be obtained by setting the time for selecting the second pulse generating circuit 18 to be a predetermined time determined by the timer circuit 30 during and after the F/C signal is "1". In this case, timed circuit 3
0 may be triggered when the F/C signal changes from "0" to "1", and the counter operation may be stopped while the F/C signal is "1".

Effects of the Invention As explained above, according to the present invention, the throttle valve is opened by the pulse generating means that generates a pulse signal whose duty ratio is controlled according to the difference between the detected running vehicle speed and the preset set vehicle speed. In the constant speed driving device for automobiles, the pulse generating means includes a first pulse generating means having a large duty ratio change of the output pulse with respect to a unit change in the difference between the set vehicle speed and the traveling vehicle speed, and a second pulse generating means having a small duty ratio change. and a pulse generating means for a predetermined period of time when receiving a signal indicating that fuel injection has been stopped from the electronically controlled fuel injection device, or a signal indicating that fuel injection has been stopped. Since a time limit means is provided for selecting the second pulse generating means for a predetermined period of time and for a predetermined period thereafter, the second pulse generating means is selected on a long downhill slope where fuel cut is performed, and the so-called constant speed is maintained. Since the travel control gain is reduced, the cycle of fuel cut and restart can be shortened, and the number of shocks is reduced, making it possible to improve ride comfort.

Furthermore, since the fuel cut signal output from the existing electronic fuel injection device is used to switch the gain, the cost is lower than when using a dedicated device such as an inclination sensor for detecting downhill slopes.

In addition, when driving on a flat road or on a gentle downhill slope where fuel cut is not normally performed, the first pulse generation means is selected, and the constant pulse generation means has the same good responsiveness as before. It becomes possible to execute speed traveling control.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the conventional problems, FIG. 2 is a block diagram of the main part of an embodiment of the constant speed traveling device for automobiles of the present invention, and FIG. 3 is a characteristic diagram of the pulse generating circuit 17. FIG. 4 is a characteristic diagram of the pulse generation circuit 18,
FIG. 5 is a diagram showing an example of temporal changes in the traveling vehicle speed, throttle opening, F/C signal, and output of the time limit circuit 30 with respect to the set vehicle speed a when the second pulse generation circuit 18 is selected. . 10 is a reed switch, 12 is an F/V conversion circuit, 13 is an analog switch, 14 is a memory circuit,
15 is a differential amplifier, 16 is a changeover switch, 17,
18 is a pulse generation circuit, 19 is an actuator,
30 is a time circuit.

Claims (1)

[Claims] 1. In a constant speed traveling system for an automobile, the opening degree of a throttle valve is controlled by a control signal generating means that generates a control signal for driving an actuator according to a difference between a detected traveling vehicle speed and a preset set vehicle speed. The signal generating means includes a first control signal generating means having a large control gain with respect to a unit change in the difference between the set vehicle speed and the traveling vehicle speed, and a second control signal generating means having a small control gain.
In addition, each time a fuel cut signal indicating that fuel injection is stopped from the electronically controlled fuel injection device is received, a predetermined control signal generating means that is longer than the generation cycle of the fuel cut signal is provided. A constant speed traveling device for an automobile, comprising: a time limit means for selecting a period of the second control signal generating means.