JP2014069679A - Braking control system of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve braking stability of a vehicle during rectilinear braking succeeding high-velocity traveling.SOLUTION: A skidding prevention control system of a vehicle includes skidding prevention means that computes a difference Δψ between a target yaw rate ψt based on a steering angle of a vehicle or a vehicle velocity and an actual yaw rate ψ (S40), that when the difference Δψ between the target yaw rate ψt and actual yaw rate ψ exceeds a threshold ψa (S90), independently brakes and controls the left and right wheels of the vehicle (S100) so as to reduce skidding of the vehicle. Herein, a rear-wheel load Fr of the vehicle is detected (S50). When the rear-wheel load Fr is smaller than a first predetermined value F1, the threshold ψa is set to be lower than a normal threshold ψ1 set when the rear-wheel load Fr is equal to or larger than the first predetermined value F1, according to the rear-wheel load Fr (S70).

Description

  The present invention relates to a control technology for a braking device for a vehicle.

A skid prevention device has been developed as one of safety devices in a vehicle braking device.
The skid prevention device can change the distribution of braking force independently for the left and right wheels of the vehicle. For example, there is a difference between the target yaw rate of the vehicle intended by the driver's steering operation and the actual yaw rate of the vehicle detected by the yaw rate sensor. When there is, there is an effect of suppressing the side slip of the vehicle by controlling the braking force of the left and right wheels of the vehicle so as to coincide with the target yaw rate.

  Further, in the vehicle in which the distribution of the braking force of the left and right wheels can be changed as described above, the sum of the braking forces of the left wheel (left front wheel + left rear wheel) of the vehicle and the right wheel of the vehicle when the vehicle is driven straight forward. A braking force control technique for improving braking stability by matching the sum of braking forces of (right front wheel + right rear wheel) has been proposed (Patent Document 1).

JP-A-5-262213

In a vehicle equipped with the above-described vehicle skid prevention device, when the vehicle travels in the vicinity of a straight line, generally, the skid prevention control for matching the actual yaw rate of the vehicle to the target yaw rate is not performed. This is because if the anti-skid control is activated during traveling in the vicinity of a straight line, the anti-slip control may function excessively, leading to a decrease in posture stability.
Further, as in Patent Document 1 described above, even when control is performed to match the sum of the braking forces of the left wheels of the vehicle and the sum of the braking forces of the right wheels of the vehicle during straight braking, for example, from high speed running When the vehicle is suddenly braked, the vehicle tends to slip sideways, and the braking stability may not be ensured.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a vehicle braking control device that improves the braking stability of the vehicle during straight braking from high-speed traveling. is there.

  In order to achieve the above object, the vehicle braking control apparatus according to claim 1 independently controls the braking force of the left and right wheels of the vehicle based on the difference between the target yaw rate based on the running state of the vehicle and the actual yaw rate of the vehicle. Thus, in a vehicle braking control device having a skid prevention means for reducing the side slip of the vehicle by bringing the actual yaw rate close to the target yaw rate, a load detection means for detecting a ground contact load of the rear wheel of the vehicle, and a load detection means. And an operation control means for operating the skid prevention means when the ground contact load of the rear wheel decreases.

According to a second aspect of the present invention, there is provided the vehicle braking control device according to the first aspect, wherein the skid prevention means starts independent control of the braking force of the left and right wheels when the difference between the target yaw rate and the actual yaw rate exceeds a threshold value. The operation control means is characterized in that the threshold value is set to decrease as the ground contact load on the rear wheel decreases.
According to a third aspect of the present invention, there is provided the vehicle braking control device according to the first or second aspect, wherein the operation control means has a lower ground contact load detected by the load detection means than a rear wheel ground load when the vehicle is stationary. Sometimes, the skid prevention means is actuated.

  According to a fourth aspect of the present invention, there is provided the vehicle braking control device according to any one of the first to third aspects, wherein the load detecting means is based on the acceleration of the vehicle detected by the acceleration detecting means provided in the vehicle. It is characterized by detecting the ground contact load of the wheel.

According to the vehicle braking control device of the first aspect, when the ground contact load of the rear wheel is reduced, the skid prevention means is operated, so that the braking force of the rear wheel cannot be sufficiently exerted and slipping easily occurs. Control by the skid prevention means can be started to quickly reduce the skid of the vehicle.
In particular, when the grounding load of the rear wheels is ensured during straight braking of the vehicle, excessive control by the skid prevention means is suppressed, and even during straight braking, such as during straight braking from high speed running, Under such circumstances, the control by the skid prevention means can be performed quickly, and the braking stability of the vehicle can be improved.

According to the vehicle braking control device of the second aspect, since the threshold value is set so as to decrease as the rear wheel ground contact load decreases, the threshold value is appropriately set corresponding to the rear wheel ground load. Thus, the braking stability of the vehicle can be further improved.
According to the vehicle braking control apparatus of claim 3, the skid prevention means is operated when the ground contact load of the rear wheel detected by the load detection means is lower than the ground load of the rear wheel when the vehicle is stationary. The timing for starting the independent control of the braking force of the wheel can be easily advanced.

  According to the vehicle braking control apparatus of the fourth aspect, since the ground contact load of the rear wheel is detected based on the acceleration of the vehicle detected by the acceleration detecting means provided in the vehicle, the rear wheel can be easily configured with a simple configuration. Can be detected.

1 is a schematic configuration diagram of a braking control device according to an embodiment of the present invention. It is a flowchart which shows the execution determination point of the skid prevention control performed in a brake control control unit. It is an example of the map which sets threshold value (psi) a for execution determination of skid prevention control. It is a time chart which shows an example of transition of the target yaw rate at the time of turning at the normal time, and an actual yaw rate. It is a time chart which shows an example of transition of the target yaw rate and actual yaw rate at the time of cornering when the rear wheel load is smaller than normal.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a braking control apparatus according to an embodiment of the present invention.
The vehicle 1 provided with the braking control device of the present embodiment is a four-wheel vehicle, and is a front-wheel drive vehicle that can travel by driving the front wheels 2L and 2R by the engine 30. Each wheel 2L, 2R, 3L, 3R of the vehicle 1 is provided with a brake device 4L, 4R, 5L, 5R, and the braking force can be controlled independently in each brake device 4L, 4R, 5L, 5R. It has become.

  Each wheel 2L, 2R, 3L, 3R of the vehicle 1 is provided with a wheel speed sensor 6L, 6R, 7L, 7R for detecting a wheel speed. The vehicle 1 also controls a steering angle sensor 8 that detects the steering angle of the steering, a yaw rate sensor 9 (actual yaw rate detection means) that detects the actual yaw rate of the vehicle 1, and brake devices 4L, 4R, 5L, and 5R. A brake control control unit 20 (operation control means) is provided.

Further, the vehicle is provided with load sensors 10L and 10R (load detection means) for detecting the ground load of the rear wheels 3L and 3R.
An electronic control unit including a brake control unit 20, an interface (not shown), a memory, a CPU, and the like, and has a skid prevention function that suppresses the yaw rate of the vehicle 1 using the brake devices 4L, 4R, 5L, and 5R. doing. The brake control control unit 20 inputs detection information from the steering angle sensor 8, the wheel speed sensors 6L, 6R, 7L, 7R, the yaw rate sensor 9, and the load sensors 10L, 10R, and the brake devices 4L, 4R, 5L, The braking force is controlled by setting a braking pressure of 5R.

A system constituted by the skid prevention function of the rudder angle sensor 8, the wheel speed sensors 6L, 6R, 7L, 7R, the yaw rate sensor 9, the brake devices 4L, 4R, 5L, 5R and the brake control control unit 20 is the present invention. Corresponds to skid prevention means.
FIG. 2 is a flowchart showing execution determination points for the skid prevention control executed in the brake control control unit 20. FIG. 3 is an example of a map for setting the threshold value ψa for determining whether to perform the skid prevention control.

This routine is repeatedly executed while the vehicle is traveling.
First, in step S10, the steering angle of the steering is input from the steering angle sensor 8, and the wheel speed is input from the wheel speed sensors 6L, 6R, 7L, 7R, and the vehicle speed V is obtained. For the vehicle speed V, for example, the second largest wheel speed among the wheel speeds detected by the wheel speed sensors 10L, 10R, 11L, and 11R may be obtained as the vehicle speed V. Then, the process proceeds to step S20.

In step S20, the target yaw rate ψt is calculated. Specifically, the theoretical target yaw rate ψt is calculated based on the steering angle input from the steering angle sensor 8 in step S10 and the vehicle speed V detected by the wheel speed sensors 6L, 6R, 7L, 7R. Then, the process proceeds to step S30.
In step S30, the actual yaw rate ψ of the vehicle 1 is input from the yaw rate sensor 9. Then, the process proceeds to step S40.

In step S40, a yaw rate deviation Δψ that is a difference between the target yaw rate ψt calculated in step S20 and the actual yaw rate ψ input in step S30 is calculated (Δψ = ψ−ψt). Then, the process proceeds to step S50.
In step S50, the rear wheel load Fr is input. The rear wheel load Fr is the ground load of the rear wheels 3R and 3L, and is the sum of the ground load Frr of the right rear wheel 3R and the ground load Frl of the left rear wheel 3L input from the rear wheel load sensors 10L and 10R. (Fr = Frr + Frl). Then, the process proceeds to step S60.

  In step S60, it is determined whether or not the rear wheel load Fr input in step S60 is less than a first predetermined value F1. The first predetermined value F1 may be set near a lower limit value that ensures straight running stability when a braking operation is performed during straight running, for example, a rear wheel load when the vehicle 1 is stationary. If the rear wheel load Fr is less than the first predetermined value F1, the process proceeds to step S70. If the rear wheel load Fr is greater than or equal to the first predetermined value F1, the process proceeds to step S80.

  In step S70, the threshold value ψa for starting the side slip prevention control is set based on the rear wheel load Fr input in step S50. The threshold value ψa may be set using, for example, a map as shown in FIG. As shown in FIG. 3, when the rear wheel load Fr is less than the first predetermined value F1, the threshold value ψa may be set to decrease as the rear wheel load Fr decreases. Then, the process proceeds to step S90.

In step S80, the threshold value ψa for starting the side slip prevention control is set to the normal threshold value ψ1. The normal threshold value ψ1 is a threshold value for starting the side slip prevention control at the normal time when the rear wheel load Fr is sufficient. Then, the process proceeds to step S90.
In step S90, it is determined whether the yaw rate deviation Δψ calculated in step S40 is greater than a threshold value ψa. When the yaw rate deviation Δψ is larger than the threshold value ψa, the process proceeds to step S100. If the yaw rate deviation Δψ is equal to or less than the threshold ψa, the process returns to step S10.

  In step S100, skid prevention control is executed. This side slip prevention control is a known side slip prevention control, and the braking force of the brake devices 4L, 4R, 5L, and 5R is set so that the actual yaw rate ψ approaches the target yaw rate ψt, that is, the yaw rate deviation Δψ approaches 0. To control. Specifically, when the actual yaw rate ψ is larger than the target yaw rate ψt in the vehicle clockwise rotation direction, the braking force of the left wheel 2L, 3L brake devices 4L, 5L is applied to the right wheel 2R, 3R brake devices 4R, 5R. When the actual yaw rate ψ is larger than the target yaw rate ψt in the left rotation direction of the vehicle, the braking force of the brake devices 4R and 5R for the right wheels 2R and 3R is set to the brake device 4L for the left wheels 2L and 3L. The braking force is distributed so as to be larger than the braking force of 5L. Then, the process returns to step S10.

As described above, in the present embodiment, the threshold value ψa of the yaw rate deviation Δψ that determines whether to perform the skid prevention control is changed according to the rear wheel load Fr.
The threshold value ψa is set to the normal threshold value ψ1 when the rear wheel load Fr is equal to or greater than the first predetermined value F1 at which the braking force can be sufficiently exerted. Thus, by setting the threshold value ψa of the yaw rate deviation Δψ to a value other than 0, when the yaw rate deviation Δψ occurs, the side slip prevention control is not immediately executed, and the execution of the excessive side slip prevention control is suppressed. it can.

FIG. 4 shows the transition of the target yaw rate ψt and the actual yaw rate ψ during turning when the rear wheel load Fr is larger than the first predetermined value F1, that is, when the braking force of the rear wheels 3L and 3R can be sufficiently exerted. It is a time chart which shows an example. FIG. 4 shows changes in the target yaw rate ψt and the actual yaw rate ψ when the vehicle 1 travels while turning the steering wheel back and forth.
In FIG. 4, the thick line indicates the target yaw rate ψt, the thin solid line indicates the actual yaw rate ψ before the side slip prevention control is performed, and the thin broken line indicates the actual yaw rate ψ after the side slip prevention control is performed.

As shown in FIG. 4, for example, when the steering is operated to the left in the straight traveling state, the target yaw rate ψt increases in accordance with the steering operation, but the actual yaw rate ψ of the vehicle 1 is slightly delayed from the target yaw rate ψt. The same trend.
Then, as shown on the right side of FIG. 4, when a side slip occurs and the yaw rate deviation Δψ increases and exceeds the threshold value ψa, here the normal threshold value ψ1, the side slip prevention control is executed. Therefore, the actual yaw rate ψ is reduced and the side slip is suppressed.

  In addition, when the rear wheel load Fr is equal to or greater than the first predetermined value F1, the threshold value ψa is set to the normal threshold value ψ1, so that, for example, as shown on the left side of FIG. Without reaching the threshold value ψa, the skid prevention control is not executed, and braking by excessive skid prevention control can be reduced. Particularly during straight braking, braking performance can be ensured by reducing braking by excessive skid prevention control.

On the other hand, when the rear wheel load Fr is less than the first predetermined value F1 at which the braking force cannot be sufficiently exerted, the threshold ψ is set to a value lower than the normal threshold ψ1. Thereby, execution of skid prevention control can be started quickly.
FIG. 5 is a time chart showing an example of changes in the target yaw rate ψt and the actual yaw rate ψ during turning when the rear wheel load Fr is less than the first predetermined value F1, that is, when the braking force cannot be sufficiently exerted. It is. In FIG. 5, as in FIG. 4, changes in the target yaw rate ψt and the actual yaw rate ψ when the steering wheel is turned back and forth are shown. The thick line indicates the target yaw rate ψt, and the thin solid line indicates the actual value before the skid prevention control is performed. The yaw rate ψ and the thin broken line indicate the actual yaw rate ψ after the side slip prevention control is performed.

When the rear wheel load Fr is less than the first predetermined value F1, the threshold value ψa is set to a value smaller than the normal threshold value ψ1. Therefore, as shown in the left side of FIG. 5, there is a possibility that a side slip may occur even if the yaw rate deviation Δψ is small. However, since the threshold ψa is set small, the side slip prevention control is activated, the actual yaw rate ψ is suppressed, and the side slip is suppressed. Reduce.
Further, as shown on the right side of FIG. 5, even when the yaw rate deviation Δψ is large, the skid prevention control of course operates. However, since the threshold ψa is set low, the start timing of the skid prevention control is accelerated and the yaw rate deviation is increased. Δψ can be quickly suppressed.

  In particular, particularly during sudden braking from high speed traveling, the rear wheel load Fr generally decreases, so that the braking force of the rear wheels 3L and 3R decreases. For example, even during straight forward braking, skidding occurs. It becomes easy. On the other hand, in the present embodiment, as the rear wheel load Fr decreases, the threshold ψa of the yaw rate deviation Δψ is reduced below the normal threshold ψ1, so that the side slip prevention control can be activated quickly. Therefore, when the rear wheel load Fr decreases as in the case of sudden braking from high speed traveling, the skid prevention control can be started quickly to improve braking stability.

As described above, in the present embodiment, the threshold value ψa for determining the execution of the skid prevention control is changed according to the rear wheel load Fr, and the rear wheel load Fr sufficiently increases the braking force when the vehicle 1 is linearly braked. In a normal time when it can be exerted, the threshold ψa is set to the normal threshold ψ1, and excessive control of the skid prevention control can be suppressed to ensure posture stability.
And, for example, when the rear wheel load Fr cannot sufficiently exert the braking force as in the case of straight braking from high speed running, the threshold ψa is set to be smaller than the normal threshold ψ1, so the skid prevention control is quickly started. The braking stability of the vehicle 1 can be improved.

  In addition, this invention is not limited to the above embodiment. For example, in the above-described embodiment, when the rear wheel load Fr is less than the first predetermined value F1, the threshold value ψa is set to continuously decrease as the rear wheel load Fr decreases. May be set. In the present invention, at least when the rear wheel load Fr is less than the first predetermined value F1, it may be set smaller than the normal threshold value ψ1 set when the rear wheel load Fr is not less than the first predetermined value F1.

  Further, for example, in the above embodiment, when the rear wheel load Fr is reduced, the threshold ψa is set small so that the start of the side slip prevention control is advanced, but the side slip prevention control is performed by making a difference in the braking force between the left and right wheels. The start of execution may be accelerated. This is because the actual moment is intentionally generated early by making a difference in the braking force between the left and right wheels, and the start of the side slip prevention control is advanced, thereby preventing a sudden side slip during straight-ahead braking. The braking stability can be improved.

  In the above embodiment, the rear wheel load Fr is detected by the load sensors 10L and 10R. However, even if the acceleration sensor 11 is provided in the vehicle 1 and the rear wheel load Fr is estimated based on the acceleration of the vehicle 1, Good. In this way, the rear wheel load Fr can be easily detected with a simple configuration. In addition to the acceleration sensor 11, a rear acceleration sensor 12 that detects acceleration at the rear of the vehicle may be provided, and the rear wheel load Fr may be estimated based on the difference in acceleration before and after the vehicle 1.

In the above embodiment, the rear wheel load Fr is detected by the load sensors 10L, 10R. However, based on the difference between the front and rear wheel speeds of the vehicle 1 obtained from the wheel speed sensors 6L, 6R, 7L, 7R. The rear wheel load Fr may be estimated. In this way, the rear wheel load Fr can be easily detected without providing the load sensors 10L and 10R.
In the above embodiment, as the skid prevention control, the skid prevention is performed by the control of the left and right brake devices 4L, 4R, 5L, and 5R. However, the output of the engine 30 is reduced or the driving force of the left and right drive wheels of the vehicle is reduced. Or may be controlled to further reduce the actual moment of the vehicle 1. In this way, the side slip of the vehicle can be further reduced.

1 Vehicle 3L, 3R Rear wheel 4L, 4R, 5L, 5R Brake device (side slip prevention means)
6L, 6R, 7L, 7R Wheel speed sensor (side slip prevention means)
8 Snake angle sensor (side skid prevention means)
9 Yaw rate sensor (side skid prevention means)
10L, 10R load sensor (load detection means)
11, 12 Acceleration sensor (load detection means)
20 Brake control control unit (side slip prevention means, operation control means)

Claims (4)

Based on the difference between the target yaw rate based on the running state of the vehicle and the actual yaw rate of the vehicle, the braking force of the left and right wheels of the vehicle is independently controlled to bring the actual yaw rate closer to the target yaw rate, thereby reducing the side slip of the vehicle. In a vehicle braking control device having a skid prevention means for reducing,
Load detecting means for detecting a ground load of a rear wheel of the vehicle;
An operation control means for activating the skid prevention means when a ground contact load of the rear wheel detected by the load detection means decreases;
A braking control device for a vehicle, comprising: The skid prevention means starts independent control of the braking force of the left and right wheels when the difference between the target yaw rate and the actual yaw rate is greater than a threshold value.
2. The vehicle braking control device according to claim 1, wherein the operation control unit sets the threshold value to decrease as the ground contact load of the rear wheel decreases.   The operation control means activates the skid prevention means when the ground load of the rear wheel detected by the load detection means is lower than the ground load of the rear wheel when the vehicle is stationary. The vehicle braking control device according to claim 1 or 2.   The load detection means detects a ground contact load of the rear wheel based on an acceleration of the vehicle detected by an acceleration detection means provided in the vehicle. The vehicle brake control device according to the item.

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