JPS63180529A - Control device for driving with constant speed - Google Patents

Abstract

PURPOSE:To prevent hunting a downhill by detecting the difference between a real car speed and a set car speed in a vehicle having a fuel cut function to input a duty and memorizing a duty integral value at the time of the restart of fuel supply for performing a throttle driving with the stored value during a period from the fuel cut to the restart. CONSTITUTION:In a control device for driving with a constant speed, a duty converter 31 for converting the difference between a real car speed and target card speed 2 to a duty and an actuator 4 is driven with the duty which is converted in the duty converter 31 and the opening of a throttle 5 is adjusted to perform a constant speed control. The outputted duty is integrated and stored in serial. Upon driving on a downhill, at the time of restarting after the elapse of cutting of fuel supply, switches S1 and S2 are turned off and a switch S3 is turned on through the set of FF81 so that the control is performed with a constant value of the stored integrated duty. Therefore, it is possible to effectively prevent a car seed hunting due to the repeat of the fuel cut and the restart.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a constant speed running control device for a vehicle that performs fuel cut when the throttle opening is fully closed, and in particular, reduces vehicle speed hunting on downhill slopes by controlling the throttle opening. The aim is to avoid this by fixing the

[Conventional technology]

The constant speed cruise control device, which detects the difference between the target vehicle speed and the traveling vehicle speed and automatically adjusts the throttle/notch opening, does not use a braking function, so when the vehicle approaches a downhill slope, it reduces the throttle opening and adjusts the target vehicle speed. Generally speaking, it should not be exceeded.

By the way, depending on the vehicle, when the throttle opening is fully closed at a predetermined engine speed or higher, the fuel supply to the engine is stopped to reduce the load on the exhaust gas processing catalyst (which also improves fuel efficiency). may be done. When constant speed driving control is performed on a vehicle equipped with such a steering/rotation function, if the vehicle is traveling downhill where the throttle opening must be close to fully closed, the vehicle speed will be reduced by the engine fuel cut when the throttle opening is fully closed. Hunting occurs. This occurs when the vehicle attempts to travel in an area where constant speed travel is not possible, as shown by the shaded area in FIG.

In this figure, the horizontal axis shows the slope of the downhill slope, and the vertical axis shows the vehicle speed.
The straight line ■ is the vehicle speed-gradient characteristic when the fuel is cut off (throttle opening fully closed, so engine braking is applied), and the straight line ■ is the vehicle speed-gradient characteristic when the fuel is on (throttle opening fully closed + slight opening). The shaded area between these straight lines is an area that cannot exist constantly. In other words, for example, in the case of a 5% downward slope, the vehicle speed will be, for example, 70 Km/h with the throttle opening fully closed (■), and if the throttle is opened even slightly, the vehicle speed will be, for example, 90 Km/h (90 Km/h), and if the throttle opening is fully closed, the vehicle speed will be, for example, 90 km/h. It is not possible to drive steadily at vehicle speeds such as 80 km/h. This is shown in Figure 4,
When the throttle opening is fully open and the engine speed is at a certain value, the engine control device will cut off the fuel, and when it opens a little more than fully closed and reaches ■, it will start fuel injection, but in these ■ and ■ This is due to a step change in the amount of fuel. The subsequent change in fuel amount is proportional to the throttle opening.

In the above example, the target speed set for constant speed driving is 80km/h.
If so, when the fuel is cut O, the vehicle speed is lower than the target speed, and when the fuel is on, the vehicle speed is higher than the target speed.
For this reason, the constant speed traveling device repeats ■ and ■, which causes hunting in the vehicle speed.

The range in which constant speed driving is not possible in Figure 3 occurs even when the driver is operating; if the accelerator is released, the vehicle speed will drop below the desired value, and if the accelerator is slightly depressed, the vehicle speed will rise above the desired value. Or, the vehicle speed is hunting while driving. However, the driver does not notice the increase or decrease in vehicle speed as a result of his/her own operations. On the other hand, in the case of automatic driving (driving at a constant speed), the driver does not do anything and is forced to stop frequently, so the shock (hunting) caused by the increase or decrease in vehicle speed is quite noticeable.

Hunting occurs because the vehicle speed at which constant speed travel is desired is in a vehicle speed range where constant speed travel is impossible, and the constant speed travel device opens and closes the throttle in an attempt to keep the vehicle speed constant. Therefore, when driving downhill where you cannot drive unless the throttle opening is close to fully closed, the throttle opening is fixed, sacrificing the accuracy of constant speed driving to some extent to prevent hunting, and the throttle opening is fixed. Area where the degree is far from fully closed (
When the vehicle returns to driving in the vehicle speed range (in which the vehicle can travel), it is sufficient to return to the original throttle opening control.

FIG. 5 is a control characteristic diagram of a duty control type constant speed traveling device that is compatible with this method. The figure shows that the vehicle enters a downhill slope from a flat road, and as the vehicle speed increases, the output duty is initially reduced and the throttle opening is reduced, and then the fuel is cut (0 point) when the throttle opening is fully closed, and from there the vehicle speed decreases. Then, the output duty increases, and as a result, the throttle opening increases again, and eventually when the fuel turns on (point a), the output duty at that time is memorized and fixed, so from then on the vehicle speed will not increase according to the slope. However, this shows that the driving characteristics are such that hunting does not occur.

[Problem that the invention seeks to solve]

However, a duty control type constant speed traveling device converts the difference between the target vehicle speed and the traveling vehicle speed into a duty, and uses the duty to drive an actuator to adjust the throttle opening. Therefore, from a change in duty to a change in throttle opening There is a mechanical response delay between the actuator and throttle.

This is tl in Figure 5. Due to this delay, the throttle opening is fixed at 5 points away from point a when the fuel is turned on, and the vehicle speed increases by that difference to reduce the deviation from the target vehicle speed. Expanding.

The present invention attempts to improve the above-mentioned points by using a duty integral value having an appropriate time constant.

[Means for solving problems]

The present invention is installed in a vehicle that cuts the fuel supply when the throttle opening is fully open at a predetermined engine speed or higher, and restarts the fuel supply when the throttle opening is a small angle smaller than fully closed. A duty control type constant speed cruise control device comprising a duty output section that outputs a duty that makes a difference from a target vehicle speed zero, and an actuator that is energized by the output duty and adjusts the throttle opening. a duty integrator that integrates duty;
A memory section that holds the output of the integrator when the fuel supply is restarted, and a memory section that normally selects the output duty of the duty output section and stores the output duty of the duty output section when the fuel supply is restarted from the cut state. The actuator is characterized by comprising a control section that selects an output and applies the selected output to the actuator.

[Effect]

If the output duty obtained from the duty output section is integrated with an appropriate time constant, the change in the integral value will be slower than the change in the output duty. Then, in the process where the fuel supply is cut on a downhill slope and then restarted, the output duty changes in a square shape, so the duty integral value at the time of restart is smaller than the output duty value. Therefore, if the integral value is maintained and the actuator is energized, even if the throttle opening increases from a fully closed angle thereafter, the angle can be kept sufficiently small. As a result, the increase in vehicle speed can be suppressed to a small extent, so that the vehicle speed deviation from the target vehicle speed can be reduced.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention, in which 1 is a vehicle speed signal processing section, 2 is a target vehicle speed setting section, 3 is a duty output section, 4 is an actuator, 5 is a throttle, 6 is a duty integrator, 7 is a storage section, and 8 is a control section. The duty output unit 3 includes a duty conversion unit 31 that converts the difference between the traveling vehicle speed at each point in time from the vehicle speed signal processing unit 1 and the target vehicle speed stored in the target vehicle speed setting unit 2 into a duty, It consists of a basic duty setting section 32 that is set accordingly, and an adder 33 that adds the duty of the converting section 31 to the basic duty to obtain an output duty. The control unit 8 includes switches Sl and 32 that operate in the same manner,
A switch S3 operates in the opposite direction to these, and an R-3 flip-flop (FF) controls the opening and closing of these switches.
) 81, this FF 81 is set when changing from fuel cut to on (resumption), and is reset when the return condition is satisfied. 82 is a fuel supply restart detector, and 83 is a return condition satisfaction detector. Switch Sl, S
2 turns off when the FF81 is set (S) and turns on when it is reset (R).

Switch S3 is the opposite of this, and the overall relationship is as shown in the table below.

Table 1 The operation will be explained below with reference to the control characteristics shown in FIG.

The duty during constant speed running is determined by adding a correction duty according to the differential speed output from the comparator 31 to the basic duty output from the basic duty setter 32, using an adder 33. Normally, the switch S1.52 is on and 33 is off, and the output of the adder 33 is applied to the actuator 4.
It is also integrated by an integrator 6 and the contents of the storage section 7 are updated.

It is preferable that the time constant of the integrator 6 be made approximately equal to the response delay time constant Ts of the actuator 4 and the throttle 5, but if this is done, the throttle will close due to a slight change in the intake manifold negative pressure and a fuel cut will occur. be. To avoid this, it is possible to stop the throttle opening slightly by setting the time constant to be smaller than Ts, thereby suppressing the possibility of the fuel cut occurring again.

In this state, when the vehicle approaches a downhill slope, the increase in vehicle speed cannot be suppressed even if the throttle opening is reduced, and when the throttle is finally fully closed, the fuel is cut (point C). As a result of the fuel cut, the vehicle speed decreases, the output duty increases to compensate for this, and eventually, when the throttle opening changes from fully closed to slightly open, the fuel is turned on (point a). The process up to this point is the same as in Figure 5.

In the present invention, when the fuel is turned on, FF81 is set, and switch S1. Since S2 is turned off and S3 is turned on, the duty applied to the actuator 4 until then is switched from the output duty of the adder 33 (solid line) to the duty integral value in the storage section 7 (dotted chain line). Since the switch S2 is off, this integral value does not change thereafter. For this reason, the throttle opening is fixed at a slightly open angle from point a, so the increase in vehicle speed is caused by the fifth point.
This is significantly reduced compared to the figure. Therefore, similar to the method shown in Figure 5, vehicle speed hunting due to repeated fuel canting/on can be prevented, and the traveling vehicle speed after the throttle opening is fixed can be kept at a value close to the target vehicle speed, more precisely around ■ in Figure 3. You can keep it.

The change to fuel cut-on can be detected by the change in the idle switch from on (throttle opening fully closed) to off (slightly opened). The detector 82 is for this purpose, and if the throttle is fully closed during constant speed driving, it may be determined that the vehicle is going downhill.

There are other times when I step on the brake, but at this time the constant speed driving state is canceled. Further, when accelerating by stepping on the accelerator, then releasing the accelerator and pressing the set switch, the fully closed state may occur, but in this case, the control is inhibited by the set timer (for example, for 24 seconds).

In addition, full closure may occur during override, that is, when you step on the accelerator while driving at a constant speed, then release the accelerator to return to constant speed driving, but in this case as well, control is prohibited (for example, within a range of 7 km or more from the target speed). It has become. When the vehicle reaches a flat road after going downhill, the vehicle speed decreases, so this can be used as a return condition. In other words, the detector 83 is equipped with a vehicle speed differentiator, and if the negative output (deceleration) of the detector 83 exceeds a certain value, it is determined that the road is flat and the FF 81 is reset. Integrator 6
For example, the integral formula can be set as follows.

The same effect as the present invention can also be achieved by storing in memory the output duty value A before t1 from point a in FIG. This is not a good idea because it requires a memory to store it, but in this respect, the storage section 7 of the present invention only needs to store one calculation result.

〔Effect of the invention〕

As explained above, according to the present invention, vehicle speed hunting that occurs on a downhill slope can be avoided by simple means, and the vehicle speed deviation from the target vehicle speed can be kept small.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a control characteristic diagram thereof, FIG. 3 is an explanatory diagram of a region where constant speed running is impossible, FIG. 4 is an explanatory diagram of fuel cant/on, and FIG. FIG. 5 is a control characteristic diagram of the throttle opening fixed method. In the figure, 1 is a vehicle speed signal processing section, 2 is a target vehicle speed setting section, 3 is a duty output section, 4 is an actuator, 5 is a throttle, 6 is a duty integrator, 7 is a storage section, and 8 is a control section.

Claims (1)

[Claims] Equipped with a vehicle that cuts fuel supply when the throttle opening is fully closed at a predetermined engine speed or higher, and resumes fuel supply when the throttle opening is slightly wider than fully closed. A duty control type constant speed cruise control device comprising a duty output section that outputs a duty that makes the difference between zero, and an actuator that is energized by the output duty to adjust the throttle opening,
A duty integrator that integrates the duty, a storage unit that holds the output of the integrator when the fuel supply is restarted, and a memory unit that normally selects the output duty of the duty output unit and the fuel supply is in a cut state. 1. A constant speed cruise control device of duty control type, comprising: a control section that selects the output of the storage section and applies the selected output to the actuator when restarting from the start.