JPH045155A - Braking force control device for vehicle - Google Patents

Abstract

PURPOSE:To avoid or reduce a nose dive automatically by providing a moment before stop detecting means for detecting the moment immediately before the stop of a vehicle, and controlling a braking force adjusting means to reduce braking force immediately before the stop. CONSTITUTION:In a controller 16 including an anti-skid control device 30 receiving the output of a G-sensor 20 and wheel speed sensors 24 27 to regulate the braking liquid pressure of each wheel so that a slip factor becomes the target slip factor, there are further provided a moment before vehicle stop detecting means 17 and a braking force reduction control means 18. The output of the G-sensor 20 and a vehicle speed sensor 21 is received by the moment before stop detecting means 17, and when the time immediately before stop is detected, a deceleration line is predicted by the braking force reduction control means 18 from the degree of deceleration at the time immediately before stop, and control signals are output to braking liquid pressure control valves 12-15 so that deceleration is changed along the target deceleration line B.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a braking force control device for a vehicle that controls the braking force of wheels to reduce nose dive that occurs immediately before a vehicle stops.

(Prior Art) When stopping a vehicle by applying braking force (brake fluid pressure) to the wheels, a phenomenon called nose dive occurs in which the vehicle deceleration suddenly increases just before stopping, causing the tip of the vehicle to dive.

The nose dive occurs when the wheels first stop when the vehicle stops, and the vehicle body, which is still moving forward due to inertia, is pulled by the stopped wheels and brought to a sudden stop immediately before and immediately after the wheels stop.

When the nose dive occurs, the vehicle body is brought to a sudden stop as described above, resulting in a rapid increase in vehicle deceleration (vehicle body deceleration), which causes the occupant to suddenly lean forward and reduce ride comfort. Therefore, for example, a skilled driver releases the brake pedal just before stopping the vehicle in order to avoid or reduce such nose dive.

Heretofore, so-called anti-skid control has been known, for example, as described in Japanese Patent Publication No. 63-41332, which controls the braking force of the wheels during braking to avoid the wheels from locking. In conventional anti-skid control, no consideration is given to countermeasures against nose dive as described above.

(Problem to be Solved by the Invention) As mentioned above, conventionally nose dive has been avoided or reduced when the vehicle is stopped by the driver's brake pedal operation. If it is possible to avoid or reduce nose dive, anyone can avoid or reduce nose dive without delicately operating the brake pedal just before stopping, and it will be possible to stop the vehicle smoothly, improving ride comfort.

In view of the above circumstances, an object of the present invention is to provide a braking force control device for a vehicle that can automatically avoid or reduce the nose dive by appropriately controlling the braking force of the wheels immediately before the vehicle stops. .

(Means for Solving the Problems) In order to achieve the above object, a braking force control device for a vehicle according to the present invention includes a braking force applying means that applies a braking force to a wheel, and a braking force applying unit that adjusts the braking force applied to the wheel. a braking force adjustment means for detecting a moment immediately before the vehicle stops; a braking force reduction means for receiving an output from the immediately before stopping detecting means and causing the braking force adjusting means to reduce the braking force immediately before the vehicle stops; It is characterized by comprising a control means.

Immediately before the vehicle stops is a predetermined period from when the vehicle stops until slightly before that period, and is a period during which nose dive can be avoided or reduced by reducing the braking force. For example, it means from the start of the nose dive to the time of stopping, or from a little before the start of the nose dive to the time of stopping. Note that the above-mentioned stopping of the vehicle means that the vehicle body comes to a complete stop.

The above-mentioned detection just before the vehicle stops may be performed using any method. For example, if the period just before the vehicle stops is determined from the start of the nose dive to the time of stopping, changes during vehicle deceleration or vehicle height (height of the vehicle body relative to each wheel) may be used. This can be done by detecting the start of a nose dive from a change or the like.

In addition, the reduction of the braking force immediately before the stop described above is simply a matter of reducing the braking force so as to avoid or reduce nose dive, and the specific mode is not limited to a specific one.

The reduction of the braking force immediately before the vehicle stops is determined by detecting that the vehicle is about to stop (starting point of the period immediately before stopping) from an increase in vehicle deceleration after the vehicle speed has fallen below a predetermined value, and This can be done by predicting the vehicle deceleration immediately before stopping if braking force reduction control is not performed based on the prediction, and reducing the braking force so that it follows a target deceleration that is lower than the predicted deceleration.

Note that the vehicle deceleration used to predict the vehicle deceleration immediately before the stop mentioned above is the deceleration during braking, and it is possible to predict the vehicle deceleration (degree of nose dive) just before the above stop. Any deceleration may be used, for example, the deceleration when the vehicle is about to stop, or a corresponding value, such as the deceleration when the vehicle speed reaches a low predetermined value, such as 5 b/h.

In addition, when performing the braking force reduction control, the larger the deceleration of the vehicle is, the more the start of the braking force reduction control is delayed, or the target deceleration is set such that the expected deceleration immediately before the stop remains in an increased state. can be set.

In addition, the deceleration when the above-mentioned deceleration is larger is also the same as above, and for example, the deceleration when the vehicle is about to stop, the deceleration when the vehicle speed reaches 51 m/h, etc. can be used. . Further, the start time of the braking force reduction control and the setting of the target deceleration may be changed continuously or in stages depending on the magnitude of the deceleration.

(Function) In the braking force control device comprising the just-before-stop detection means and the braking force reduction control means as described above, by reducing the braking force just before the vehicle stops when nose dive occurs, the wheels are slightly reduced. The vehicle will rotate slightly forward, and the vehicle will decelerate and come to a smooth stop, making it possible to avoid or reduce nose dive.

In addition, when reducing the braking force just before stopping, the occurrence of nose dive can be reliably detected by detecting just before stopping based on the increase in vehicle deceleration after the vehicle speed drops below a predetermined value. By controlling the speed to follow the target deceleration that is set lower than the expected deceleration, it is possible to reliably avoid or reduce nose dive.

Furthermore, when performing the braking force reduction control described above, by setting the target deceleration so that the larger the deceleration of the vehicle is, the start of the braking force reduction control is delayed, or the increase in expected deceleration is left larger. In this case, the higher the vehicle deceleration is, the more the expected deceleration increases.
As a result, the higher the vehicle deceleration, that is, the greater the driver's request to stop, the more the driver can feel the increase in deceleration.
Preferred control that does not cause the driver to feel uneasy about not stopping is possible (Example) Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing an overall schematic configuration of a vehicle equipped with an embodiment of the braking force control device according to the present invention.

In this vehicle, the output of a power plant 3 consisting of an engine 1, a transmission 2, etc. is input to a rear differential 5 via a propeller shaft 4, and the output of the power plant 3 divided by this rear differential 5 is divided into left and right rear axles 6L. , 6R to the left and right rear wheels 7L, 7R, each rear wheel 7L, 7R is rotationally driven, and along with this, the left and right front wheels 8L, 8R are also rotated. ing.

Furthermore, this vehicle is equipped with a braking force control device 10 that reduces the braking force of each wheel during braking (when the brake pedal is depressed) immediately before the vehicle stops.

The braking force control device IO includes a brake device 1 which is a braking force applying means and includes a disc rotor lla that rotates integrally with each of the wheels and a caliper llb that is supplied with brake fluid pressure and controls the rotation of the disc rotor lla.
1, and a brake fluid pressure control valve 12, which is a braking force adjusting means for adjusting the brake fluid pressure supplied to each brake device 11.
13.14.15, and vehicle stop immediately before detection means 17 configured by the controller 16 and detects immediately before the vehicle stops.
(See Fig. 2), which is also constituted by a controller 16, receives the output from the vehicle stop detection means 17, and outputs a control signal to the brake fluid pressure control valves 12 to 15 to each wheel immediately before the vehicle stops. A braking force reduction control means 18 (see FIG. 2) that reduces the brake fluid pressure of The vehicle includes a vehicle speed sensor 21 serving as a detection means, a brake depression force sensor 22 that detects the depression force of the brake pedal, and a road surface gradient sensor 23 that detects the gradient of the road surface.

In this embodiment, the G sensor 20 is a sensor disposed at an appropriate position on the vehicle body and detects acceleration/deceleration in the longitudinal direction of the vehicle body, and the vehicle speed sensor 21 is used to detect vehicle speed based on the number of rotations of the propeller shaft. It uses sensors.

The braking force control device 10 also functions as an anti-skid control device that performs anti-skid control by individually controlling the brake fluid pressure for each brake device 11 during braking. Each of the above-mentioned brake fluid pressure control valves 12 for controlling
anti-skid control means 3 for outputting control signals to ~15;
0 (see Figure 2), and each wheel speed (rotational speed of the wheel) necessary to perform the anti-skid control.
The controller 16 is configured to input the outputs of the wheel speed sensors 24, 25, 28, and 27 that detect the .

FIG. 2 is a block diagram showing the controller 16 in more detail.

As shown in the figure, the controller 16 includes the vehicle stop immediately before detection means 7, a braking force reduction control means 1B, and an anti-skid control means 30.

In this embodiment, the anti-skid control means 30 receives the outputs of the G sensor 20 and the wheel speed sensors 24 to 27, and estimates the vehicle speed from the maximum wheel speed of each wheel speed and the deceleration of the vehicle. , the slip rate of each wheel is calculated from the estimated vehicle speed and each wheel speed, and the slip rate is determined by a separately set target slip rate (usually a slip rate that provides the maximum coefficient of friction between the wheels and the road surface). The system is configured to adjust the brake fluid pressure of each wheel so that the

Hereinafter, the just-before-stop detection means 17 and the braking force reduction control means 18 will be described in detail with reference to FIGS. 3(a), 1(b), and 3(c).

FIGS. 3(a) and 3(b) are diagrams showing changes in vehicle deceleration and vehicle speed from when the vehicle approaches a stop (in this example, the vehicle speed is 5 touch/h or less) until it stops. Figure 3 (C
) is a diagram showing a manner in which brake fluid pressure is reduced by braking force reduction control.

As shown in Figure 3 (a), when a vehicle is stopped by the brakes, the vehicle deceleration G gradually decreases, and just before the vehicle stops, the deceleration G increases and nose dive occurs, and then the vehicle deceleration G gradually decreases. The speed G rapidly decreases to zero.

The immediately before stop detection means 17 in the present embodiment is configured to detect the G
In response to the outputs of the sensor 20 and the vehicle speed sensor 21, the vehicle deceleration begins to increase after the vehicle is about to stop, for example after the vehicle speed reaches a predetermined extremely low value (57/h or less in this embodiment). This is to detect the point in time when the vehicle is about to stop, and more specifically, as shown in FIG. The rate G is a predetermined value G. The point at which it becomes more than t
1 is detected as the point immediately before stopping.

Here, Go may be set to 0 or a value slightly larger than 0, taking into consideration that G may vary somewhat due to various causes.

When the braking force reduction control means 18 receives the output of the immediately before stopping detection means 17 and is about to stop, the braking force reduction control means 18 determines, based on the vehicle deceleration, the deceleration immediately before the stop when the braking force reduction control described below is not performed. and a target deceleration setting means 19 for predicting a change in the predicted deceleration line and setting a target deceleration line lower than the predicted deceleration line, and the brake system is configured such that the deceleration of the vehicle changes along the target deceleration line. The control is performed to reduce the hydraulic pressure, and more specifically, as shown in Fig. 3(a), the control is performed at the point just before the stop (
tx ) or the degree of increase in deceleration at or around t1, predict the deceleration line shown by the solid line A after t1, and the dot-dashed line in the figure lower than the predicted deceleration line A. A target deceleration line B shown by is set, and a control signal is output to each brake fluid pressure control valve 12 to 15 in order to reduce the brake fluid pressure so that the deceleration G changes along the target deceleration line B. It is something.

The above-mentioned brake fluid pressure reduction control may be any control that can reduce the brake fluid pressure in order to avoid or reduce the nose dive that occurs immediately before stopping.
As shown in Figure (c), this can be done by reducing the brake fluid pressure by a predetermined amount for a predetermined period of time from time t1 when it is detected that the vehicle is about to stop.

FIG. 4 is a flowchart showing the procedure of the above-mentioned immediate-stop detection and braking force reduction control.

Further, the detection of increase in vehicle deceleration after the vehicle speed becomes below the predetermined value of 5 b/h is as shown in FIG. 3(a).
The deceleration CO when the vehicle speed becomes 5 KIn/h or less is stored, and after that, the vehicle deceleration G is the deceleration G at that time. This may be done by detecting the time point (t2) when the value becomes larger. In addition, finding the above expected deceleration line A and setting a target deceleration line B lower than it means predicting the vehicle speed line C after time t1 and predicting the expected vehicle speed as shown in FIG. 3(b). This is substantially the same as setting a target vehicle speed line D that is larger than line C. Therefore, in the braking force reduction control, the predicted vehicle speed line D is set based on the change in vehicle speed immediately before stopping. C is determined, a target vehicle speed line D larger than that is set, and a control signal is output to each brake fluid pressure control valve 12 to 15 to reduce the brake fluid pressure so that the vehicle speed changes along the target vehicle speed line D. You may do so.

FIG. 5 is a flowchart showing the procedure for detection immediately before stopping and braking force reduction control in such a case.

Note that the target deceleration line B and the target vehicle speed line D
The setting may be any setting as long as it can avoid or reduce the increase in deceleration (occurrence of nose dive) just before stopping and bring the vehicle to a smooth stop. For example, Fig. 3 (a) and (b)
), it is desirable to set the deceleration G and vehicle speed V so that they decrease smoothly without rapidly increasing or decreasing.

As mentioned above, the point at which the deceleration increases or the vehicle speed suddenly decreases is detected as immediately before stopping, and the deceleration or vehicle speed is detected along the target deceleration line that is lower than the expected deceleration line or the target vehicle speed line that is higher than the expected vehicle speed line. By reducing the brake fluid pressure as the vehicle speed changes, nose dive just before stopping can be avoided or reduced, and ride comfort can be improved.

Incidentally, it is desirable that the braking force reduction control (dive control) be prohibited in certain cases.

That is, when performing anti-skid control (ABS control), it is desirable to give priority to anti-skid control and not to perform braking force reduction control.

In addition, if the vehicle speed is still high to some extent, for example, 5KJn
It is also preferable not to perform this when the value is greater than /h.

This braking force reduction control is originally intended for the period just before stopping, and if the deceleration increases for some reason at a certain high speed and the braking force is reduced, the vehicle will not be able to stop. In consideration of this, the embodiment described above is configured to perform the detection immediately before stopping on the condition that the vehicle speed becomes 5 visits/h or less.

In addition, the road surface slope K is 1% or more (uphill) or -1%
In the following cases (downhill), it is also preferable not to do this because if it is uphill, the vehicle may fall backwards after stopping, or if it is downhill, the stopping distance may be longer.

Furthermore, if the brake pedal force is very large, for example 80
If it is 9 or more, it is a sudden brake and the driver wants to stop immediately, so it is preferable not to perform braking force reduction control.

In addition, whether the brake is sudden or not depends on, for example, the vehicle speed of 51Q.
Judgment is made based on whether the deceleration when the brake pedal speed decreases to 1/h or less is larger or smaller than a predetermined deceleration G (G1 is the deceleration expected to occur when the brake pedal force is 30 kg). is also possible.

FIG. 6 is a flowchart showing the procedure for checking the above-mentioned conditions and then permitting the start of braking force reduction control, and FIG. 12 is a flowchart showing a procedure for canceling braking force reduction control in such a case.

Further, it is desirable that the braking force reduction control changes the control content depending on the magnitude of vehicle deceleration.

In other words, the greater the deceleration, the more the driver intends to stop suddenly. Therefore, the greater the deceleration, the greater the expected increase in deceleration immediately before the stop, giving the driver the feeling that the vehicle is coming to a stop. It is desirable to avoid giving a feeling of anxiety that it will not stop.

As an example of such control, as shown in Figure 8, the larger the deceleration, the slower the start of the braking force reduction control. One method is to lengthen the delay time to (black circle in the figure) so that a state in which the expected deceleration increases (a state in which the expected deceleration is convex above the expected deceleration line) remains large. In the figure, when the solid line H indicates the smallest deceleration, the delay time is zero, and as the deceleration increases with the solid lines I and J, the delay time increases (Dz
>DI). Furthermore, the solid line indicates the case where, as described above, the deceleration is greater than the predetermined value G1, so it is determined that the braking is sudden and the braking force reduction control is not performed.

Further, as another example of such control, as shown in FIG. 9, a method may be considered in which the target deceleration line is set so that the larger the deceleration is, the larger the expected deceleration line remains in the rising state.

The magnitude of the deceleration in the above case can be determined based on the magnitude of the deceleration (brake pedal depression force) during each control. Specifically, for example, as shown in FIGS. 8 and 9, Vehicle speed increased to 5! This can be determined based on the magnitude of the deceleration when the speed drops to n/h or less. Also,
In FIGS. 8 and 9, the solid line on the right side of the white circle indicates the predicted deceleration line and the corresponding predicted vehicle speed line, and the dashed-dotted line indicates the target deceleration line and the corresponding target vehicle speed line.

In addition, in performing the above-mentioned braking force reduction control, the first
As shown in the figure, automatic transmission (A T) and manual transmission (M
Regarding T), it is preferable to set the brake fluid pressure reduction amount to be smaller in the automatic transmission. In the case of an automatic transmission, there is an acceleration component due to the creep phenomenon, so if the brake fluid pressure is reduced too much, the vehicle speed will increase due to the acceleration component, and the driver will accelerate slightly even though he is trying to stop, and the vehicle will try to move forward. I get the feeling that there is. Therefore, in the case of an automatic transmission, it is preferable to reduce the brake fluid pressure by a smaller amount than in the case of a manual transmission, thereby suppressing the adverse effects of the creep phenomenon when the brake fluid pressure is reduced.

Also, if the deceleration is large, the amount of increase in deceleration immediately before stopping is large, so the brake fluid pressure will be reduced more greatly, but when the amount of reduction in brake fluid pressure is large like this, it is shown in Figure 11. It is better to reduce it to two stages.

In addition, when equipped with a wheel speed sensor that detects the wheel speed of each wheel for anti-skid control as in the above embodiment, the wheel speed sensor can be used as a vehicle speed sensor by, for example, using the average of each wheel speed as the vehicle speed. May be used.

(Effects of the Invention) As detailed above, the braking force control device for a vehicle according to the present invention is configured to reduce the braking force immediately before stopping the vehicle where the nose dive occurs. You can try to avoid or reduce it.

In addition, the occurrence of a nose dive can be reliably detected by detecting just before stopping based on the increase in vehicle deceleration after the vehicle speed has fallen below a predetermined value, and the vehicle deceleration can be set lower than the above expected deceleration. By performing control in accordance with the set target deceleration, it is possible to reliably avoid or reduce nose dive.

In addition, by setting the target deceleration in such a way that the start of braking force reduction control is delayed as the vehicle deceleration is large, or the increase in expected deceleration is left larger, the higher the vehicle deceleration, the more the driver's The larger the stop request, the more the driver can feel the increase in deceleration, and it is possible to perform favorable control without causing the driver to feel anxious that the vehicle will not stop.

[Brief explanation of drawings]

Fig. 1 is an overall schematic diagram of a vehicle equipped with an embodiment of the present invention, Fig. 2 is a block diagram showing details of the controller portion in Fig. 1, and Figs. 3 (a), (b), (c). are diagrams showing changes over time in vehicle deceleration, vehicle speed, and brake fluid pressure, respectively.
5 and 5 are flowcharts showing the braking force reduction control procedure, FIGS. 6 and 7 are flowcharts showing the braking force reduction control prohibition procedure, and FIGS. a) , (
b) is a diagram showing changes in vehicle deceleration and vehicle speed over time, respectively;
Figures 10(a), (b) and 11(a),
(b) is a diagram showing changes over time in vehicle deceleration and brake fluid pressure, respectively. 7L, 7R, 8L, 8R... Wheels 10... Braking force control device 11... Braking force applying means 12-15... Braking force adjusting means 17... Immediately before stop detection means 18... Braking Power reduction control means 19...Target deceleration setting means 20...Deceleration detection means 21...Vehicle speed detection means % formula % 2, Name of the invention Toshidono No. 104 Relationship with the case of the person who corrects the braking force control II device of a vehicle Patent applicant Location 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Name (
313) Mazda Motor Corporation

Claims (4)

[Claims] (1) Braking force applying means for applying braking force to the wheels, braking force adjusting means for adjusting the braking force applied to the wheels, immediately before stopping detecting means for detecting when the vehicle is about to stop, and immediately before stopping detecting means A braking force control device for a vehicle, comprising: braking force reduction control means for receiving an output from the braking force adjusting means and causing the braking force adjusting means to reduce the braking force immediately before stopping the vehicle. (2) The braking force control device for a vehicle according to claim 1, further comprising deceleration detection means for detecting deceleration of the vehicle and vehicle speed detection means for detecting vehicle speed, wherein the immediately-before-stop detection means is configured to detect the deceleration of the vehicle. Immediately before the stop is detected from an increase in the deceleration of the vehicle after the vehicle speed has fallen below a predetermined value in response to outputs from the deceleration detection means and the vehicle speed detection means, and the braking force reduction control means detects when the vehicle stops. and a target deceleration setting means for predicting the deceleration of the vehicle immediately before the vehicle stops when the braking force reduction control is not performed based on the deceleration of the vehicle, and setting a target deceleration lower than the predicted deceleration. A braking force control device for a vehicle, wherein the braking force is reduced so that the deceleration of the vehicle becomes the target deceleration. (3) The braking force control device for a vehicle according to claim 2, wherein the braking force reduction control means delays the start of the braking force reduction control as the deceleration of the vehicle increases. Braking force control device for vehicles. (4) The braking force control device for a vehicle according to claim 2, wherein the target deceleration setting means is configured such that the higher the deceleration of the vehicle, the greater the expected deceleration increase immediately before the stop. A braking force control device for a vehicle, characterized in that it sets a target deceleration.