JPH09301143A - Braking force distribution device - Google Patents

Abstract

(57) Abstract: A braking force capable of determining a spin tendency of a vehicle and reducing costs without providing an acceleration sensor or the like for detecting a longitudinal acceleration and a lateral acceleration of the vehicle. Provide a distribution device. A wheel cylinder that generates a braking force on each wheel by brake fluid pressure, an actuator that can adjust the brake fluid pressure of each wheel cylinder, and a wheel speed sensor that outputs a detection signal corresponding to the wheel speed, By determining whether or not the vehicle has a spin tendency based on only the detection signal from the wheel speed sensor at the time of turning braking, and including a controller that controls the actuator based on the determination result, The spin tendency of the vehicle is determined without providing an acceleration sensor or the like for detecting acceleration and lateral acceleration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a braking force distribution device for preventing a vehicle from entering a spin state during turning braking.

[0002]

2. Description of the Related Art In order to prevent a vehicle from entering a spin state during turning braking, the tendency of spin of the vehicle immediately before it falls into a spin state is detected to forcibly reduce the brake fluid pressure of a wheel cylinder on the rear wheel side, for example. The present applicant has filed an earlier application regarding a braking force distribution device that performs such control as described above (Japanese Patent Application No. 5-245701). This braking force distribution device determines the spin tendency of a vehicle in a vehicle equipped with a so-called active suspension device that actively controls the suspension device, by using an acceleration sensor that detects the vertical acceleration of the active suspension device. Then, the braking force is distributed, and it is not necessary to provide an acceleration sensor for detecting the acceleration in the longitudinal direction and the acceleration in the lateral direction of the vehicle.

[0003]

However, in a vehicle not equipped with an active suspension device, the longitudinal acceleration and the lateral acceleration of the vehicle are detected in order to determine the spin tendency of the vehicle. Since it is necessary to provide an acceleration sensor, a hydraulic pressure sensor, etc., there is a problem that the cost cannot be reduced.

Therefore, an object of the present invention is to determine the spin tendency of the vehicle and to reduce the cost without providing an acceleration sensor or the like for detecting the longitudinal acceleration and the lateral acceleration of the vehicle. It is to provide a braking force distribution device.

[0005]

In order to achieve the above object, a braking force distribution device according to claim 1 of the present invention is a wheel cylinder which is provided on each wheel and generates a braking force on each wheel by brake hydraulic pressure. An actuator that can adjust the brake fluid pressure of each wheel cylinder, a wheel speed sensor that is provided for each wheel and outputs a detection signal according to the speed of the wheel, and only a detection signal from the wheel speed sensor during turning braking And a controller for controlling the actuator based on the result of the determination. As a result, the controller determines whether or not the vehicle has a spin tendency based on only the detection signal from the wheel speed sensor at the time of turning braking, and thus detects the acceleration in the front-rear direction and the acceleration in the left-right direction of the vehicle. It is possible to determine the spin tendency of the vehicle without providing an acceleration sensor or the like.

A braking force distribution device according to a second aspect of the present invention relates to the braking force distribution device according to the first aspect, wherein the controller is
From the detection signal from the wheel speed sensor, the outside in the radial direction of turning is calculated, and the wheel acceleration of the outside front wheel is calculated, and the wheel acceleration is compared with a preset threshold value to spin the vehicle. It is characterized by determining whether there is a tendency. This is focused on that the wheel acceleration of the outer front wheel during turning approaches a preset threshold value in line with the boundary of whether or not the vehicle tends to spin, and the controller controls the wheel speed during turning braking. From the detection signal from the sensor, the outside in the radial direction of the turning is determined, and the wheel acceleration of the outside front wheel is calculated, and the vehicle is in a tendency to spin by comparing the wheel acceleration with a preset threshold value. It is determined whether or not. Therefore, the spin tendency of the vehicle can be determined without providing an acceleration sensor or the like for detecting the acceleration in the front-rear direction and the acceleration in the left-right direction of the vehicle.

A braking force distribution device according to claim 3 of the present invention relates to the braking force distribution device according to claim 1, wherein the controller is
From the detection signal from the wheel speed sensor, the inside in the radial direction of turning is determined, and the front and rear wheel speed difference between the front and rear wheels, which are the inside, is calculated, and the front and rear wheel speed difference and a preset threshold value. It is characterized in that whether or not the vehicle has a spin tendency is determined by comparing with. This is because the front / rear wheel speed difference between the front and rear wheels on the inside of the vehicle turns around a preset threshold value in accordance with the boundary whether the vehicle tends to spin or not. Is used to calculate the inner side in the radial direction of turning from the detection signal from the wheel speed sensor during turning braking and to calculate the front-rear wheel speed difference between the front and rear wheels, which is the inner side, and to set the front-rear wheel speed difference in advance. It is determined whether the vehicle has a tendency to spin by comparing the threshold value with the threshold value. Therefore, the spin tendency of the vehicle can be determined without providing an acceleration sensor or the like for detecting the acceleration in the front-rear direction and the acceleration in the left-right direction of the vehicle.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of a braking force distribution device of the present invention will be described below with reference to FIGS.

In FIG. 1, reference numeral 11a is the left front wheel of the vehicle, reference numeral 11b is the right front wheel, reference numeral 11c is the left rear wheel, and reference numeral 11d.
Indicates the right rear wheel, respectively, and the wheels 11a to 11d.
Is a wheel that is driven by integrally rotating disc rotors 12a to 12d and brake fluid pressure to bring a pad (not shown) into pressure contact with a corresponding one of the disc rotors 12a to 12d to generate a braking force according to the brake fluid pressure. Disc brake 14a including cylinders 13a to 13d
˜14d and rotation of each wheel 11a to 11d at a predetermined angle and outputs a pulse for each rotation of the predetermined angle. In other words, a wheel speed sensor 15a to output a detection signal corresponding to the speed of each wheel 11a to 11d. 15d and 15d, respectively (note that a to d correspond to a to d on the wheels).

The wheel cylinders 13a to 13d are connected through an actuator 18 to a master cylinder 17 which generates a brake fluid pressure according to the amount of depression of a brake pedal by a driver. The actuator 18 is controlled by a control signal from the controller 20 that is output based on the detection signals from the wheel speed sensors 15a to 15d, and adjusts the brake fluid pressure transmitted from the master cylinder 17 to each wheel cylinder 18. It is possible. The braking force distribution device is composed of an actuator 18, wheel cylinders 13a to 13d, wheel speed sensors 15a to 15d, and a controller 20.

Next, the principle of determining whether or not the vehicle has a spin tendency in the first embodiment will be described. During turning braking, if a spin tendency (state immediately before the actual occurrence of spin) occurs, the case of left turning is illustrated in FIG. 2 and explained below. A direction, that is, a counterclockwise yaw angular acceleration indicated by an arrow 22 is generated, and due to the generation of the yaw angular acceleration, each wheel 11a to 11d has a line connected to the center of gravity 23 as indicated by arrows 24a to 24d in FIG. Acceleration is generated in the turning direction perpendicular to the minute, that is, in the leftward direction when viewed from the center of gravity 23. Here, the arrow shown with a broken line in FIG. 2 has shown the advancing direction of a wheel.

As described above, the yaw is the center of gravity 23 of the vehicle.
Is generated for each wheel 11 based on this yaw.
The accelerations generated in a to 11d are smaller on the side closer to the center of gravity 23 and larger on the side farther from the center of gravity 23 according to the distance from the center of gravity 23 of the vehicle. In this case, since the center of gravity 23 is located in front of the center of the vehicle, the accelerations 24a, 24b of the left and right front wheels 11a, 11b due to the generation of the yaw angular acceleration are small,
The accelerations 24c and 24d on the left and right rear wheels 11c and 11d are increased.

As is clear from FIG. 2, the influence of the generation of yaw angular acceleration on the traveling direction of the wheels 11a to 11d is greatest at the front wheel on the outer side in the radial direction of the turn, that is, the right front wheel 11b. Then, the relationship between the speed and acceleration of the front wheel, that is, the right front wheel 11b, which is on the outer side of the turning where the generation of the yaw angular acceleration has the greatest influence on the traveling direction during turning braking, is shown in time series together with the yaw angular acceleration and the yaw angular speed. , As shown in FIG.
In FIG. 3, when the vehicle is in the turning braking state at the time point t ₀ and has a spin tendency at the time point t ₁ , the yaw angular velocity sharply increases, and accordingly, the yaw angular acceleration sharply increases from 0 and then decreases to 0. (Time point t ₁ to time point t ₂ ). During this time t ₁ ~ time t _2, without the wheel speed of the front outside wheel ie right front wheel 11b was reduced at a constant rate reduced by previous braking, the yaw angular acceleration 0
And rapidly decreases after the time point t ₂ made will be then returned to the normal characteristics, therefore, the front outside wheel i.e. right acceleration of the front wheel 11b is reduced After rapidly increases from the time t ₁ time t ₂ After that, the characteristic is that it further decreases rapidly and increases again until the time point t ₃ .

Then, the acceleration of the front wheel on the outside of the turn, that is, the right front wheel 11b, which appears in the above-mentioned spin tendency, increases and decreases (between time t ₁ and time t ₂ ) and increases continuously from this decrease (time t ₂ -time t). Focusing on the characteristic of (between t ₃ ), if the characteristic of increase to decrease is detected, it is determined that there is a tendency to spin when the wheel acceleration is equal to or greater than a preset threshold value (positive value). However, in other cases, it is determined that there is no tendency to spin, and on the other hand, if the characteristic of increase from decrease is detected, when the wheel acceleration is equal to or less than a preset threshold value (negative value), It is determined that the spin tendency is present, and in other cases, it is determined that the spin tendency is not present.

In the above, since the vehicle is in the braking state and the wheel speed naturally tends to decrease, the characteristic of the decrease to increase characteristic appears more significantly. In this case, the range is indicated by X in FIG. The characteristic of decrease to increase is detected, and it is determined whether or not the wheel acceleration (negative value) at this time is less than or equal to a preset threshold value A (negative value).

Next, the controller 20 according to the above
The determination of whether or not the vehicle has a spin tendency and the braking force distribution control started based on this determination will be described. After the ignition key is turned on, the controller 20 inputs the detection signals, that is, the wheel speeds from all the wheel speed sensors 15a to 15d according to the flowchart shown in FIG. 4 (step S1), and based on the wheel speeds. During turning, a speed difference of a predetermined value or more occurs between the outside and the inside in the radial direction of turning, so if the following expression (1) is satisfied, it is determined that the vehicle is in a turning state, and this expression (1) is used. If not satisfied, it is determined that the vehicle is not in a turning state and is in a straight running state, and it is determined whether the wheel is a right turn or a left turn because the outside wheel at the time of turning becomes faster than the inside wheel among the wheels 11a to 11d. (Step S2). Left / right wheel speed difference = | left wheel speed−right wheel speed | ≧ B (km / h) (1)

In the above, the difference between the left and right wheel speeds may be the difference between the averages of the front and rear wheels or the difference between the front wheels.
It can be used as the difference between the rear wheels, and whether it is a right turn or a left turn can be determined by comparing the average of the front and rear wheels, comparing the front wheels, comparing the rear wheels. However, in this case, the front wheels should be used in each case.

Next, in step S2, the wheels 11a to 11d are
Among them, the wheel acceleration of the front wheel that is determined to be outside the turning is calculated by differentiating the wheel speed (step S
3). Then, it is determined whether or not the calculated wheel acceleration of the front wheel on the outside of the turning is equal to or less than a threshold value A (negative value) (step S4). It is determined whether the time ta, which is started at the time when the state occurs and resets when the state disappears, is equal to or longer than a preset predetermined time T (step S5). Then, when the measured time ta becomes equal to or longer than the preset predetermined time T, a control start signal is output and the braking force distribution control is executed (step S6).

On the other hand, when it is determined in step S2 that the vehicle is not in a turning state and is in a straight traveling state, when it is determined in step S4 that the wheel acceleration of the front wheel on the outside of the turning is not equal to or less than the threshold value A, and in step S5, If it is determined that the measured time ta is not equal to or longer than the predetermined time T, the process returns to step S1 after step S6. Here, in step S5, the duration ta in which the wheel acceleration of the front wheel on the outside of the turning is equal to or less than the threshold value A is ta.
Is monitored in order to eliminate such an influence because there is a possibility that the above state is temporarily brought about by the influence of noise or disturbance.

The braking force distribution control executed in step S6 is executed according to the flow chart shown in FIG. That is, all the wheel speed sensors 15a-15
The detection signal from d, that is, the wheel speed is input (step S7), the vehicle speed is calculated by a known method (step S8), and the slip ratios of the wheels 11a to 11d are calculated (step S9). Then, the left and right front wheels 11a, 1
1b is calculated (step S10), the actuator 18 is driven from the slip ratio difference between the left and right front wheels 11a and 11b and its differential value, for example, according to the map shown in FIG. 6 to drive the wheels 11a to 11d. Among the wheel cylinders 13a to 13d, the brake fluid pressure of the wheel cylinder of the rear wheel of which is determined to be inside the turning in step S2 is controlled (step S11).

That is, the controller 20 sets the slip ratio difference between the left and right front wheels 11a and 11b to the preset first threshold value S ₁ and the preset second threshold value S ₂ larger than this. On the other hand, S ₁ or less or S
Or is larger S ₂ less than _1, divided into three states of greater than S _2, the left and right front wheels 11a, the differential value of the slip ratio difference 11b, the first threshold value S _'1 set in advance
And 'to _2, S' second threshold S that is greater than this pre-set or is ₁ or less, or is' greater S than _{1 '2} or less S, S' ₂ greater than or three states And the combination of these is used to determine whether the brake fluid pressure of the wheel cylinder of the rear wheel on the inside of the turn is forcibly reduced, held or increased with respect to the brake fluid pressure at that time, and the actuator 18 is controlled. is there.

According to the braking force distribution system of the first embodiment having the above-described structure, the wheel acceleration of the outer front wheel during turning is preset in accordance with the boundary of whether the vehicle has a tendency to spin. Focusing on moving the threshold value A around, the controller 20 controls the wheel speed sensors 15a to 15d during turning braking.
The vehicle acceleration is calculated by calculating the wheel acceleration of the front wheel, which is the outer side in the radial direction of the turning, from the detection signal from, and comparing the wheel acceleration with a preset threshold value A. It is determined whether or not. Therefore, without providing an acceleration sensor or the like that detects the longitudinal acceleration and the lateral acceleration of the vehicle,
The spin tendency of the vehicle can be determined. Therefore, since the number of sensors can be reduced, the cost can be reduced, the reliability can be improved, and the configuration can be simplified.

Next, a second embodiment of the braking force distribution device of the present invention will be described below mainly with reference to FIGS. The second embodiment is different from the first embodiment in the principle of determining whether the vehicle has a spin tendency and the controller 20 according to the principle of determining whether the vehicle has a spin tendency. Since the controls are different, the difference will be mainly described below.

The principle of determining whether or not the vehicle has a spin tendency in the second embodiment will be described. Note that FIG. 7 shows the yaw rate (upper stage, the vertical axis is small and the upper side is small, and the lower side is large) during turning braking, the front and rear wheel speed difference (middle stage) on the inside of the turning among the wheels 11a to 11d, and the left and right wheel speed differences ( (Lower row) is shown over time.

First, from the viewpoint of preventing the rear wheels 11c and 11d from leading to the locked state during braking, generally in the case of an FF vehicle, by increasing the caliper size of the disc brake or using a valve. The front wheels 11a and 11b, which are the driving wheels, generate a higher braking force than the rear wheels 11c and 11d, and the turning is started (t
₁₁ ), immediately after braking is started (t ₁₂ ), as shown in FIG.
As shown in the middle row, the wheel speed of the front wheel on the inside of the turn is smaller than the wheel speed of the rear wheel on the inside of the turn.Therefore, the wheel speed difference between the front and rear wheels obtained by subtracting the wheel speed of the rear inside wheel from the wheel speed of the front inside wheel is It shows a slightly negative tendency.

Then, the yaw rate increases from the time (t ₁₁ ) when the turning is started, and when the spin tendency (state immediately before the actual occurrence t ₁₄ of spin) occurs, as in the first embodiment. Yaw angular acceleration occurs with respect to the center of gravity of the vehicle,
Accelerations indicated by arrows a to d in FIG. 2 are generated on the wheels 11a to 11d. As is apparent from FIG. 2, the influence of the generation of the yaw angular acceleration on the traveling direction of the wheels 11a to 11d (acting on the deceleration tendency) has an effect on the inner rear wheel rather than the inner front wheel in the turning radial direction. Is large, and when load movement starts due to deceleration, the wheel load of the rear wheel on the inside of the turning sharply decreases, so that the rear wheel on the inside of the turning tends to lock, and the wheel speed is greatly reduced with respect to the front wheel on the inside of the turning. As a result, when the spin tendency occurs, the value of the inner front-rear wheel speed difference obtained by subtracting the wheel speed of the inner rear wheel from the wheel speed of the front wheel on the inside of the turn positively increases.

Then, paying attention to the characteristic that the value of the wheel speed difference between the front and rear wheels increases positively, which appears in the spin tendency as described above, the value of the wheel speed difference between the front and rear wheels is set to a preset threshold value C. If it is above, it is determined that the spin tendency is present, and in other cases, it is determined that the spin tendency is not present. The value of the wheel speed difference between the front and rear wheels is the threshold value C.
In other words, the determination of whether or not there is the above is also a determination of whether or not the rear wheel on the inside of the turning tends to be locked.

Next, the controller 20 according to the above
Regarding the determination as to whether or not the vehicle is in the tendency to spin, only the part different from that of the first embodiment will be described. The controller 20 executes steps S12 and S13 of the flowchart shown in FIG. 8 instead of steps S3 to S5 of the flowchart shown in FIG. 4 of the first embodiment. That is, in step S2, the wheel speed of the inner rear wheel is subtracted from the wheel speed of the inner front wheel that is determined to be inside of the turn to obtain the inner front-rear wheel speed difference (step S1).
2). Then, it is determined whether or not the front and rear wheel speed difference between the calculated inner is greater than or equal to a preset threshold value C (step S13), and if it is equal to or greater than the threshold value C (t ₁₃ time ), The control start signal is output, and the braking force distribution control is executed as in the first embodiment (step S).
6). On the other hand, if it is determined in step S13 that the wheel speed difference between the front and rear wheels on the inside of the turn is not equal to or greater than the threshold value C, after step S6, that is, step S1 is executed.

According to the braking force distribution system of the second embodiment having the above-described structure, the front wheel and the rear wheel on the inner side during turning are matched with the boundary of whether or not the vehicle tends to spin. Paying attention to the fact that the front-rear wheel speed difference is around a preset threshold value, the controller 20 controls the wheel speed sensor 1 during turning braking.
From the detection signals from 5a to 15d, the inside in the radial direction of turning is determined, and the front and rear wheel speed difference between the front and rear wheels, which are the inside, is calculated, and the front and rear wheel speed difference and a preset threshold value C It is determined whether or not the vehicle has a spin tendency by comparing with. Therefore, the spin tendency of the vehicle can be determined without providing an acceleration sensor or the like for detecting the acceleration in the front-rear direction and the acceleration in the left-right direction of the vehicle. Therefore, the number of sensors can be reduced, and the same effect as that of the first embodiment can be obtained.

[0030]

As described in detail above, claim 1 of the present invention
According to the described braking force distribution device, the controller determines whether or not the vehicle has a tendency to spin based on only the detection signal from the wheel speed sensor during turning braking. Also, the spin tendency of the vehicle can be determined without providing an acceleration sensor or the like for detecting the acceleration in the left-right direction. Therefore, since the number of sensors can be reduced, the cost can be reduced, the reliability can be improved, and the configuration can be simplified.

According to the braking force distribution device of the second aspect of the present invention, the wheel acceleration of the outer front wheel at the time of turning coincides with the boundary of whether the vehicle has a tendency to spin or not, and the threshold value is set in advance. Focusing on going back and forth, the controller calculates the wheel acceleration of the front wheel which is the outer side in the radial direction of the turning from the detection signal from the wheel speed sensor at the time of turning braking and calculates the wheel acceleration in advance. It is determined whether or not the vehicle has a tendency to spin by comparing it with the threshold value. Therefore, the spin tendency of the vehicle can be determined without providing an acceleration sensor or the like for detecting the acceleration in the front-rear direction and the acceleration in the left-right direction of the vehicle. Therefore, since the number of sensors can be reduced, the cost can be reduced, the reliability can be improved, and the configuration can be simplified.

According to the braking force distribution apparatus of the third aspect of the present invention, the front-rear wheel speed difference between the front and rear wheels on the inner side at the time of turning coincides with the boundary of whether or not the vehicle tends to spin. Focusing on moving around a preset threshold value, the controller detects from the detection signal from the wheel speed sensor during turning braking,
The inside of the turning radius is determined, and the front and rear wheel speed difference between the front and rear wheels, which is the inside, is calculated, and the front and rear wheel speed difference is compared with a preset threshold value to make the vehicle tend to spin. It is determined whether or not there is. Therefore, the spin tendency of the vehicle can be determined without providing an acceleration sensor or the like for detecting the acceleration in the front-rear direction and the acceleration in the left-right direction of the vehicle. Therefore, since the number of sensors can be reduced, the cost can be reduced, the reliability can be improved, and the configuration can be simplified.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing a first embodiment of a braking force distribution device of the present invention.

FIG. 2 is a plan view showing a situation of each acceleration during turning braking.

FIG. 3 is a characteristic diagram showing variations in yaw angular acceleration, yaw angular velocity, turning outside wheel acceleration, and turning outside wheel speed with respect to time during turning braking, arranged in order from the top.

FIG. 4 is a flowchart of a determination control by the controller according to the first embodiment of the braking force distribution device of the present invention whether or not the vehicle has a spin tendency.

FIG. 5 is a flowchart of a braking force distribution control by the controller of the first embodiment of the braking force distribution device of the present invention.

FIG. 6 is a control map of the braking force distribution control by the controller of the first embodiment of the braking force distribution device of the present invention.

FIG. 7 is a characteristic diagram showing variations in yaw rate (vertical axis is small and upper side is large), turning front and rear wheel speed difference and left and right wheel speed difference with respect to time during turning braking, arranged in order from the top.

FIG. 8 is a flowchart of braking force distribution control by the controller of the second embodiment of the braking force distribution device of the present invention.

[Explanation of symbols]

 11a-11d Wheels 13a-13d Wheel cylinder 15a-15d Wheel speed sensor 18 Actuator 20 Controller

Claims (3)

[Claims] 1. A wheel cylinder provided on each wheel to generate a braking force on each wheel by a brake fluid pressure, an actuator capable of adjusting the brake fluid pressure of each wheel cylinder, and a wheel speed provided on each wheel. A wheel speed sensor that outputs a detection signal according to the above, and whether or not the vehicle has a spin tendency is determined based on only the detection signal from the wheel speed sensor during turning braking, and the actuator is determined based on the determination result. A controller for controlling the braking force distribution device. 2. The controller calculates the wheel acceleration of a front wheel, which is the outer side in the radial direction of turning from the detection signal from the wheel speed sensor and which is the outer side, and the wheel acceleration and a preset threshold value. The braking force distribution device according to claim 1, wherein it is determined whether or not the vehicle has a spin tendency by comparing with the value. 3. The controller calculates an inner side in a radial direction of turning from a detection signal from the wheel speed sensor and calculates a front / rear wheel speed difference between a front wheel and a rear wheel, which is the inner side, to calculate the front / rear wheel speed. The braking force distribution device according to claim 1, wherein the difference is compared with a preset threshold value to determine whether or not the vehicle has a spin tendency.