JPH08192729A - Braking force controller - Google Patents

Abstract

PURPOSE: To provide a braking force controller constituted so as to control a braking force of each wheel so that the traveling stability in turning braking is improved. CONSTITUTION: An antilock braking force control circuit 60, when a brake switch 67 is changed over to ON, reads the acceleration detected by an acceleration sensor 62, the rotational speed of each wheel detected by wheel rotation sensors 63-66 and the car body speed detected by a vehicle speed sensor 61. The control circuit 60 calculates the aimed wheel speed of inner wheel in turning so that left and right wheels are simultaneously locked on the basis of the car body speed, turning outer wheel speed and lateral acceleration, and controls a braking force for the turning inner wheel to provide the aimed wheel speed obtained by that calculation. Thus, the brake pressure is controlled to provide the same slip ratio in each wheel so that the traveling stability in the turning braking can be improved while a braking distance can be shortened to improve the braking performance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a braking force control device, and more particularly, to a braking force control configured to control the braking force of each wheel so that the slip ratio of each wheel becomes the same when a braking operation is performed during turning. Regarding the device.

[0002]

2. Description of the Related Art In a braking force control device for braking each wheel of an automobile, the braking force during braking is controlled depending on the road surface condition (for example, a dry road surface, a wet road surface, a frozen road surface, etc.). In order to prevent the wheels from locking due to sudden braking on the easy road surface and making the vehicle difficult to control,
An anti-lock braking force control system is adopted.

This type of anti-lock braking force control system has a solenoid valve for increasing pressure and a solenoid valve for reducing pressure, and a pressure increasing mode, a holding mode, and a pressure reducing mode are achieved by opening / closing operations of the pressure increasing solenoid valve and the pressure reducing solenoid valve. It is designed to switch to one of the modes. Therefore, when the driver depresses the brake pedal and the brake pressure is supplied to each wheel, if the vehicle is running, the brake pressure to each wheel is increased or held to the pressure increasing mode or the holding mode. When the vehicle is traveling and the wheels are being locked just before the wheels are locked, the brake pressure is reduced to a depressurization mode to prevent the wheels from locking. Then, when the vehicle stops, the solenoid valve for increasing pressure and the solenoid valve for reducing pressure are controlled to be opened and closed so as to adjust the brake pressure to each wheel so that the wheels are not locked at the same time.

Further, in a vehicle that is traveling in cornering, the load on the outside wheels of the vehicle is large due to the lateral acceleration, while the load on the inside wheels is small. Therefore, when the driver depresses the brake pedal when turning the vehicle, if the brake pressure to each wheel is increased evenly, the inner wheel will be locked before the outer wheel.
Therefore, in the braking force control device having the anti-lock braking force control system, the brake pressure (braking force) is controlled so that the brake pressure supplied to the inner wheels during turn braking is smaller than the brake pressure supplied to the outer wheels. Was.

It is considered to stabilize the behavior of the vehicle by controlling the braking force of each wheel so that the brake pressure to the inside wheel during turning becomes small when the lateral acceleration exceeds a predetermined value during turning braking. Has been. As a braking force control device for controlling this type of braking force, for example, Japanese Patent Application Laid-Open No. 1-17
There is a device as seen in Japanese Patent No. 8059.

In the device of the above publication, when braking is detected while the vehicle is turning, the solenoid valve for increasing pressure on the inner wheel is closed and the solenoid valve for reducing pressure on the same wheel is opened for a certain period of time to apply the brake pressure. The braking force of each wheel is controlled so as to decrease. Therefore, at the time of turning braking, the anti-spin moment in the direction opposite to the direction in which the vehicle tends to spin due to the decrease in the brake pressure of the inner wheels is generated to improve the running stability during turning braking.

[0007]

However, in the device disclosed in the above publication, during turning braking, the solenoid valve for increasing pressure on the inner wheel is closed and the solenoid valve for reducing pressure on the same wheel is opened for a certain period of time to reduce the brake pressure. Although the anti-spin moment is generated in the inner wheels by decreasing the braking force, there is no description about how much the braking pressure is decreased regarding the braking force reduction amount (or the braking pressure reduction amount).

Therefore, in the device of the above publication, for example, when the brake pressure is not sufficiently reduced even when the brake pressure of the inner wheel is reduced at the time of turning braking, the difference between the braking forces of the inner wheel and the outer wheel causes the turning braking. However, if the brake pressure is reduced too much, the braking performance of the inner wheels will be reduced, which will increase the braking distance, and the outer wheels will generate excessive anti-spin moments. .

Therefore, in view of the above problems, the present invention maintains the running stability during turning braking by adjusting the brake pressure so that the slip ratios of the inner wheel and the outer wheel are the same according to the lateral acceleration generated during turning braking. The purpose is to

[0010]

The above-mentioned object is defined in claim 1.
And a vehicle speed detecting means for detecting a vehicle speed of the vehicle, a wheel speed detecting means for detecting a speed of each wheel of the vehicle, and a lateral acceleration detecting means for detecting a lateral acceleration acting on the vehicle. It is determined that the vehicle is in the turning braking state, the turning state determining unit that determines whether the vehicle is in the turning state, the braking state determining unit that determines whether the vehicle is in the braking state, and the vehicle is in the turning braking state. In this case, based on the vehicle speed, the lateral acceleration, and the wheel speed of the turning outer wheel detected by the wheel speed detecting means, the slip state of the turning outer wheel and the slip state of the turning inner wheel are the same, Target turning inside wheel speed calculating means for calculating the target wheel speed of the turning inside wheel, and inside the turning so that the wheel speed of the turning inside wheel becomes the target wheel speed calculated by the target turning inside wheel speed calculating means. A braking force control means for controlling the braking force is achieved by the braking force control device comprising a.

According to the first aspect of the present invention, the target wheel speed of the inner wheels at the time of turning is calculated based on the vehicle speed, the wheel speed on the outside of the turn, and the lateral acceleration so that the left and right wheels are locked simultaneously.
By controlling the braking force of the wheels on the inside of the turn so as to reach the target wheel speed obtained by this calculation, the brake pressure is controlled so that the slip ratio of each wheel becomes the same, and the running stability during turning braking is enhanced. At the same time, it is possible to shorten the braking distance for further enhancing the braking performance.

The above object is as described in claim 2.
2. The braking force control device according to claim 1, wherein the target turning inner wheel speed calculation means is a target turning inner wheel speed V _WI , a vehicle body speed V _B , a lateral acceleration Gy, and a turning outer wheel speed is V _WO . In this case, V _WI = {(V _B −d · Gy / 2V _B ) / (V _B + d · G)
y / 2V _B )} · V _{WO This} is achieved by the braking force control device that calculates the target turning inner wheel speed V _WI .

According to claim 2, when the target turning inner wheel speed is V _WI , the vehicle body speed is V _B , the lateral acceleration is Gy, and the turning outer wheel speed is V _WO , V _WI = {(V _B- d · Gy / 2V _B ) / (V _B + d · G
y / 2V _B )} · V _WO By calculating the target turning inner wheel speed V _WI , the yaw rate of the vehicle rotation and the yaw rate of the revolution match so that the inner wheel side and the outer wheel side at the time of turning braking simultaneously. The braking force of each wheel is controlled so as to lock.

The above object is as described in claim 3.
The braking force control apparatus according to the first aspect, the braking force the target turning inner wheel speed calculating means for calculating a ^{_{V WI = (V WO 2 -2dGy}} ) 1/2 target turning inner wheel speed V _WI by the following formula It is also achieved by the control device.

According to the third aspect, V _WI = (V _WO ² -2dGy) ^1/2 target turning inner wheel speed V _WI is calculated by the following equation to calculate the slip ratio between the inner wheel side and the outer wheel side during turning braking. The braking force of each wheel is controlled so that the deviation becomes zero, and the inner wheel side and the outer wheel side are locked simultaneously during turning braking.

The above object is as described in claim 4.
A turning outer wheel speed detecting means for detecting the turning outer wheel speed V _WO, a turning inner wheel speed detecting means for detecting the turning inner wheel speed V _WI, with ^{_{V WO 2 -V WI 2> K}} (K is a predetermined value) Determining means for determining whether or not there exists, non-braking state detecting means for detecting a non-braking state, V _WO ² -V _WI ² during turning braking
It is also achieved by a braking force control device that includes a braking force control unit that controls the braking force of the wheel on the inside of the turn such that V _WO ² −V _WI ² = K when it is determined that> K.

According to the fourth aspect, the lateral acceleration Gy is detected.
V during turning braking without_WO ²-V _WI ²> K
When V_WO ²-V_WI ²Of the inner wheel turning so that
By controlling the braking force, the slip between the inner wheel side and the outer wheel side during turning braking
Control the braking force of each wheel so that the deviation of the turn-up rate becomes zero
And the inner and outer wheels are locked simultaneously during turning braking.
It

The above object is as described in claim 5.
Vehicle body speed detecting means for detecting the vehicle body speed of the vehicle, wheel speed detecting means for detecting the speed of each wheel of the vehicle, lateral acceleration detecting means for detecting the lateral acceleration of the vehicle, and the braking state of the vehicle Anti-spin based on the braking detection means for detecting the vehicle speed, the vehicle body speed detected by the vehicle body speed detection means, the turning inner wheel speed detected by the wheel speed detection means, and the lateral acceleration detected by the lateral acceleration detection means. Target turning outer wheel speed calculation means for calculating a target turning outer wheel speed for generating a moment, and braking force control for applying a braking force to the outer wheels so that the turning outer wheel speed becomes the target turning outer wheel speed. Means and
It is also achieved by a braking force control device including.

According to the fifth aspect, the target turning outer wheel speed for generating the anti-spin moment is calculated based on the vehicle speed, the turning inner wheel speed, and the lateral acceleration, and the turning outer wheel speed is the target turning outer wheel speed. By applying the braking force to the outer wheels so as to satisfy the following condition, it is possible to generate an optimal anti-spin moment when the vehicle is not turning and to maintain the running stability.

The above-mentioned object is as described in claim 6.
A turning outer wheel speed detecting means for detecting the turning outer wheel speed V _WO, a turning inner wheel speed detecting means for detecting the turning inner wheel speed V _WI, with ^{_{V WO 2 -V WI 2> K}} (K is a predetermined value) Determination means for determining whether or not there exists, non-braking state detection means for detecting a non-braking state, and V _WO ² −V _WI ² > when non-braking
It is also achieved by a braking force control device that includes a braking force control unit that applies a braking force to the wheels on the outside of the turning so that V _WO ² −V _WI ² = K when determined to be K.

According to the sixth aspect, V _WO ² -V when not braking
By applying the braking force of the wheel on the outside of the turning so that V _WO ² −V _WI ² = K when it is determined that _WI ² > K, the optimum anti-spin during turning non-braking without detecting the lateral acceleration Gy. A moment can be generated to maintain running stability.

The above object is as described in claim 7.
Vehicle body speed detecting means for detecting the vehicle body speed of the vehicle, wheel speed detecting means for detecting the speed of each wheel of the vehicle, lateral acceleration detecting means for detecting the lateral acceleration of the vehicle, and the braking state of the vehicle A braking detection means for detecting the lateral acceleration, a lateral acceleration estimating means for calculating an estimated lateral acceleration from the wheel speed detected by the wheel speed detecting means, and a lateral acceleration detected by the lateral acceleration detecting means and the estimated lateral acceleration. When the lateral acceleration detecting means determines that the lateral acceleration detecting means is abnormal by comparing the occurrence of abnormality in the lateral acceleration detecting means by comparing, the wheel speed detecting means determines whether the lateral acceleration detecting means is abnormal. Target turning inside wheel speed calculation means for calculating a target wheel speed of the inside wheel during turning based on the detected turning outside wheel speed, and the turning inside wheel speed is the target. A braking force control means for controlling the braking force of the turning inner wheel such that it becomes equal to the target wheel speed calculated by rotating the inner wheel speed calculating means also achieved by the braking force control device comprising a.

According to the present invention, the estimated lateral acceleration is calculated from the wheel speed, and the lateral acceleration detected by the lateral acceleration detecting means is compared with the estimated lateral acceleration to determine whether or not an abnormality has occurred in the lateral acceleration detecting means. judge. Then, when it is determined that the lateral acceleration detecting means is abnormal, the target wheel speed of the inside wheel at the time of turning is calculated based on the turning outside wheel speed detected by the wheel speed detecting means, and the turning inside wheel speed is the target. By controlling the braking force of the wheel on the inside of the turn so as to reach the target wheel speed calculated by the wheel speed on the inside of the turning means, the running stability during turning braking can be maintained even if the lateral acceleration detecting means fails. .

The above object is as described in claim 8.
A vehicle body speed detecting means for detecting a vehicle body speed of the vehicle; a wheel speed detecting means for detecting a speed of each wheel of the vehicle; and a lateral acceleration detecting means for detecting a lateral acceleration acting on the vehicle,
A turning braking state determining means for determining whether the vehicle is in a turning braking state, a vehicle body speed detected by the vehicle body speed detecting means during braking, and a front turning outer wheel wheel speed detected by the wheel speed detecting means And, based on the lateral acceleration detected by the lateral acceleration detecting means, the target wheel speed of the inner wheel before turning is calculated so that the slip state of the outer wheel before turning and the slip state of the inner wheel before turning become the same. Target braking front inner wheel speed calculation means and during braking,
A target turning rear outer wheel speed calculating means for calculating a target wheel speed of a rear turning outer wheel based on a front turning outer wheel wheel speed detected by the wheel speed detecting means, and a braking speed detected by the wheel speed detecting means. A target rear-rear inner-wheel speed calculating means for calculating a target wheel speed of the rear-rear inner wheel based on the front-rear outer wheel speed is compared with each wheel speed detected by the wheel speed detecting means and each target wheel speed. However, brake pressure adjusting means for adjusting the brake pressure supplied to the brake mechanism so that the wheel speed of each wheel becomes the target wheel speed, and the brake pressure for each wheel is adjusted by a command from the brake pressure adjusting means. Brake pressure switching means for switching between pressure increase, holding, and pressure reduction, and when turning, the road surface on which the outer wheel travels has a lower friction road (lower μ) than the road surface on which the inner wheel travels.
Road crossing road detecting means for detecting that the vehicle is on the road) and when the crossing road is detected by the crossing road detecting means, the brake pressure increasing, holding, and decompressing commands for the inner wheel after turning and the outer wheel after turning are compared. Then, the brake pressure command selecting means for selecting a command to set the brake pressure to a lower pressure side, and the brake pressure switching mechanism based on the brake pressure command selected by the brake pressure command selecting means are switched to perform the turning. It is also achieved by a braking force control device that includes a braking force control unit that controls the braking pressure to the rear inner wheel and the turning rear outer wheel.

According to the eighth aspect of the present invention, the target wheel speed of the front inner wheel is calculated so that the left and right wheels are locked simultaneously based on the vehicle speed, the front outer wheel wheel speed before turning, and the lateral acceleration during braking, and the target wheel speed during braking is determined during turning. The target wheel speed of the rear outer wheel after turning is calculated based on the front wheel speed of the outer wheel, and the target main wheel speeds of the rear inner wheel and rear outer wheel are calculated based on the front wheel speed of the outer front wheel. Then, each wheel speed is compared with each target wheel speed, and the brake pressure supplied to the brake mechanism is adjusted so that the wheel speed of each wheel becomes the target wheel speed, so that each wheel locks simultaneously. Apportions braking force to. Further, when it is detected that the road surface on which the outer wheel travels is lower in friction than the road surface on which the inner wheel travels (low μ road) at the time of turning, an increase in brake pressure is applied to the inner wheel after turning and the outer wheel after turning, In order to control the brake pressure to the inner wheel after turning and the outer wheel after turning by comparing the holding and decompressing commands and selecting the command to lower the brake pressure, if the outer wheel side is on a low μ road, the rear wheel If the brake pressure to the wheels on the outside of the turn is first reduced, a moment that promotes turning of the vehicle is generated and oversteer occurs, but in such a case, the rear wheels are controlled to the same wheel speed and Prevents the generation of a moment in the turning direction due to the difference in braking force from the turning outer wheel.

For the above-mentioned purpose, as described in claim 9, in the braking force control device according to claim 1, the turning state judging means uses a threshold value used for judging the turning state as a vehicle body speed. It is also achieved by a braking force control device that includes a threshold value changing means that changes the threshold value according to.

In the present invention, the threshold value changing means changes the threshold value used for determining the turning state according to the vehicle body speed. Therefore, whether or not the vehicle is in a turning state is determined by different criteria depending on the vehicle body speed.
When the vehicle body speed is high, it is desirable that the control of the braking force of the turning inner wheel be started immediately after the turning is started. On the other hand, when the vehicle body speed is low, it is desirable to execute the braking force control only when a relatively large turn is made in order to prevent unnecessary braking force control.
As described above, when it is determined whether or not the vehicle is in the turning state based on different criteria depending on the vehicle speed, the control of the braking force is started at an appropriate timing during both the high speed traveling and the low speed traveling.

The above-mentioned object is, as described in claim 10, in the braking force control device according to claim 1, when the vehicle is in a braking state, the target wheel speed of the rear wheels is the target wheel speed of the front wheels. It is also achieved by the braking force control device including first target wheel speed setting means for setting the target wheel speeds of the front and rear wheels so as to be smaller than the above.

In the present invention, the first target wheel speed setting means sets the target wheel speeds of the front and rear wheels during braking,
The target wheel speed of the rear wheels is set to be smaller than the target wheel speed of the front wheels. When such a target wheel speed is realized, the slip ratio of the rear wheels becomes larger than the slip ratio of the front wheels, and the braking ability of the rear wheels is effectively used.

Further, as described in claim 11, the above object is, in the braking force control device according to claim 10, slip ratio detecting means for detecting a slip ratio of at least one of front wheels and rear wheels, and a vehicle. Second target wheel speed setting means for setting the target wheel speeds of the front and rear wheels such that the target wheel speed of the rear wheels becomes higher than the target wheel speed of the front wheels when the vehicle is in a braking state. The target wheel speed set by the first target wheel speed setting means is set when the slip ratio detected by the slip ratio detecting means is less than or equal to a predetermined value, and the second wheel speed is set by the second target speed when the slip rate exceeds a predetermined value. It is also achieved by a braking force control device that includes target wheel speed switching means that uses the target wheel speeds set by the target wheel speed setting means as target wheel speeds.

In the present invention, the slip ratio detecting means detects the slip ratio of at least one of the front wheels and the rear wheels. If the slip ratio of the wheel exceeds a predetermined value during braking, the wheel cannot shift to a proper grip state and shifts to a locked state. During braking of the vehicle, it is desirable to generate a large braking force on the rear wheels while all the wheels maintain proper grip conditions. Therefore, in such a situation, the target wheel speed switching means employs the target wheel speed set by the first target wheel speed setting means as the target wheel speed. By the way, when there is a possibility that any of the wheels may shift to the locked state, it is desirable to shift the front wheels to the locked state prior to the rear wheels in order to maintain stable vehicle behavior. In order to shift the front wheels to the locked state prior to the rear wheels, it is necessary to make the target wheel speed of the rear wheels higher than the target wheel speed of the front wheels. Therefore, the target wheel speed switching means, when the slip ratio detected by the slip ratio detecting means exceeds a predetermined value, it is determined that one of the wheels may shift to the locked state, The target wheel speed set by the second target wheel speed setting means is adopted as the target wheel speed.

Further, as described in claim 12, in the above-mentioned object, in the braking force control device according to claim 1,
Braking force provided with wheel speed instability detection means for detecting instability of wheel speed, and braking force control prohibiting means for prohibiting control of braking force when the instability of wheel speed exceeds a predetermined value It is also achieved by the control device.

In the present invention, the wheel speed instability detecting means detects the instability of the wheel speed detected by the wheel speed detecting means. As described above, the target wheel speed of the turning inner wheel, which is the basis of the braking force control, is calculated based on the wheel speed of the turning outer wheel and the like. Therefore, stable braking force control cannot be realized in a situation where the wheel speed is unstable. In such a case, the braking force control prohibiting means prohibits the braking force control in order to prevent the braking force of the turning inner wheel from being inappropriately controlled.

The above object is, as described in claim 13, in the braking force control device according to claim 1, when the braking force of the turning inner wheel is continuously reduced for a predetermined time, the turning inner wheel is reduced. It is also achieved by a braking force control device including a first braking force control stopping means for stopping the control of the braking force.

In the present invention, the first braking force control stopping means is configured to control the braking force when the control for reducing the braking force is continuously executed for a predetermined time after the control of the braking force for the turning inner wheel is started. Stop control. The control of the braking force of the turning inner wheel is executed when the vehicle is in the turning braking state, that is, when the braking force is required for both the turning inner wheel and the turning outer wheel. Therefore, when the control for reducing the braking force of the turning inner wheel is executed for an unreasonably long time, it can be determined that the system is abnormal. The first braking force control stopping means stops controlling the braking force in the event of such an abnormality.

The above-mentioned object is, as described in claim 14, in the braking force control device according to claim 1, when the steering characteristic detecting means for detecting the steering characteristic of the vehicle and the steering characteristic is understeer,
It is also achieved by a braking force control device including a second braking force control stopping means for stopping the control of the braking force of the turning inner wheel.

In the present invention, the steering characteristic detecting means detects the steering characteristic of the vehicle. When the vehicle is turning, the oversteer characteristic is detected when the degree of turning is excessive with respect to the steering angle, while the understeer characteristic is detected when the degree of turning is insufficient with respect to the steering angle. To be detected. In order to correct the understeer characteristic, it is necessary to give a larger turning moment to the vehicle. By the way, if the slip state of the turning inner wheel and the slip state of the turning outer wheel are equal, a large braking force is generated on the turning outer wheel side compared to the turning inner wheel side due to the load difference applied to the turning inner and outer wheels. To do. The braking force deviation acts on the vehicle as a moment in a direction that hinders turning. Therefore, when the braking force of the turning inner wheel is controlled by the braking force control means, the understeer characteristic of the vehicle is promoted. The second braking force control stopping means stops the control of the braking force when the understeer characteristic is detected. When the control of the braking force is stopped, the braking force deviation between the inner and outer wheels for turning is reduced, that is, the moment in the non-turning direction acting on the vehicle is reduced, and the understeer characteristic is corrected.

The above-mentioned object is, as described in claim 15, in the braking force control device according to claim 14, when the control of the braking force of the turning inner wheel is stopped, the braking force of the turning outer wheel is increased. Is also achieved by a braking force control device including a turning outer wheel braking force control means for controlling the braking force of the turning outer wheel.

In the present invention, the turning outer wheel braking force control means controls the braking force of the turning outer wheel when the braking force control of the turning inner wheel is stopped by the second braking force control stopping means. The second braking force control stopping means stops the braking force control in order to prevent the moment in the non-turning direction acting on the vehicle from being increased by controlling the braking force of the turning inner wheel. After that, the steering characteristic of the vehicle approaches the neutral characteristic from the understeer characteristic as the braking force of the turning inner wheel approaches the braking force of the turning outer wheel. In the present invention, after the braking force control of the turning inner wheel is stopped, the increase of the braking force of the turning outer wheel is suppressed by the turning outer wheel braking force control means. The braking force is approached, and the understeer characteristic is quickly eliminated.

The above-mentioned object is, as described in claim 16, the outer wheel wheel speed detecting means for detecting the wheel speed of the turning outer wheel, the inner wheel wheel speed detecting means for detecting the wheel speed of the turning inner wheel, and the turning outer wheel. Based on the wheel speed and the wheel speed of the turning inner wheel, the lateral acceleration estimating means for estimating the lateral acceleration acting on the vehicle, and whether the lateral acceleration estimated by the lateral acceleration estimating means exceeds a first set value. Based on the wheel speed of the turning outer wheel, it is assumed that the lateral acceleration determining means that determines whether or not the lateral acceleration acting on the vehicle is a second set value that is larger than the first set value. A target turning inner wheel speed calculating means for calculating a target wheel speed of the turning inner wheel for equalizing the slip state of the turning outer wheel and the slip state of the turning inner wheel, and the lateral load estimated by the lateral acceleration estimating means. Braking force control device that controls the braking force of the turning inner wheel so that the wheel speed of the turning inner wheel becomes the target wheel speed when the degree exceeds the first set value. Also achieved by.

In the present invention, the lateral acceleration estimating means estimates the lateral acceleration acting on the vehicle on the basis of the wheel speed of the outer turning wheel and the wheel speed of the inner turning wheel.
The lateral acceleration determining means determines whether or not the estimated value of the lateral acceleration estimated as described above exceeds the first set value. When the estimated value of the lateral acceleration exceeds the first set value, the braking force of the turning inner wheel is controlled by the braking force control means so that the wheel speed of the turning inner wheel becomes the target wheel speed. In the present invention, the target wheel speed of the turning inner wheel is calculated by the target turning inner wheel speed calculating means. When the wheel speed of the turning inner wheel is controlled to the target wheel speed, the slip state of the turning inner wheel and the slip state of the turning outer wheel under the condition that the acceleration equal to the second set value acts on the vehicle. And are equivalent. Further, in a situation in which a small acceleration as compared with the second set value or a large acceleration as compared with the second set value is applied to the vehicle, the turning inner wheel and the turning outer wheel are It is controlled so that the slip states of the two do not differ greatly. Therefore, in the present invention, when the lateral acceleration estimated by the lateral acceleration estimating means exceeds the first set value, a braking state in which the slip state of the turning inner wheel and the slip state of the turning outer wheel are not significantly different from each other is realized. To be done.

Further, as described in claim 17, the above-mentioned object is, in the braking force control device according to claim 1, the target turning inner wheel speed calculating means calculates the target wheel speed V _WI ^* of the turning inner wheel, The wheel speed V _{WO of the} outer turning wheel, the tread d of the vehicle, the lateral acceleration Gy, and the vehicle speed V _B
Can also be achieved by a braking force control device that calculates according to the following equation: V _WI ^* = V _WO −d · Gy / V _B.

In the present invention, the target turning inner wheel speed calculation means calculates the target wheel speed V _WI ^* of the turning inner wheel in accordance with the calculation formula V _WI ^* = V _WO −d · Gy / V _B. The arithmetic expressions used in the present invention include a square operation,
No complicated calculation rules such as root calculation are used. Therefore, the calculation can be executed in a short time without requiring a large memory capacity, without using a complicated program.

[0044]

1 shows an antilock braking force control system to which a first embodiment of a braking force control device according to the present invention is applied. In the figure, 1 is a brake pedal, 2 is a vacuum booster, 3 is a master cylinder (actuator) that generates a brake pressure according to the stepping force of the brake pedal 1 and the boosting action of the vacuum booster 2, and 4 and 5 are brake fluids. Reservoirs for replenishing (return oil) to a return passage described later, and reference numerals 6 to 9 are wheel cylinders of a brake mechanism that receives brake pressure from the master cylinder 3 to brake each wheel.

The brake pressure generated from the master cylinder 3 when the brake pedal 1 is depressed is connected to the wheel cylinders 6 to 9 via the first and second brake pipe lines 10 and 11. Numerals 12 to 15 are pressure-increasing hydraulic pressure switching valves each of which is a normally-open solenoid valve. Normally, the valve bodies 12a to 15a are urged to open positions, and the brake pressure from the master cylinder 3 is applied to each wheel cylinder 6 to 9. Is being supplied to. But,
The hydraulic pressure switching valves 12 to 15 for increasing pressure have the solenoids 12b to 15b excited immediately before the wheels are locked, so that the valve bodies 12a to 15 are driven.
a is switched to the valve closing position, and the brake pressure supply from the master cylinder 3 is stopped.

Numerals 16 to 19 are depressurizing hydraulic pressure switching valves which are normally closed electromagnetic valves, and normally the valve bodies 16a to 19a are urged to the closed position to apply the brake pressure to each wheel cylinder 6 to 9. keeping. However, the pressure-reducing hydraulic pressure switching valves 16 to 1
9, the solenoids 16b to 19b are excited immediately before the wheels are locked and the valve bodies 16a to 19a are switched to the open position, and the brake pressure to the wheel cylinders 6 to 9 is released to the reservoirs 4 and 5 to release the brake pressure. Operates to reduce pressure.

Supply pipelines 20-23 communicated with the first and second brake pipelines 10, 11 and one end communicated with the pressure increasing hydraulic pressure switching valves 12-15 and the pressure reducing hydraulic pressure switching valves 16-19. The supply pipe passages 24 to 27 having the other ends communicated with the wheel cylinders 6 to 9 form supply system passages 28a to 28d for the wheel cylinders 6 to 9, respectively.

A return line 2 having one end connected to the pressure-reducing hydraulic pressure switching valves 16 to 19 and the other end connected to the reservoirs 4 and 5.
9 to 32 and the return conduits 33 and 34 extending from the reservoirs 4 and 5 so as to be connected to the first and second brake conduits 20 and 21 form return system passages 35a and 35b. .

The pressure-increasing hydraulic pressure switching valves 12 to 15 are the throttles 3 provided in the flow paths communicating with the supply-side pipe lines 20 to 23.
6 to 39, the bypass flow passages 40 to 43 bypassing the throttles 36 to 39, and the brake fluid on each wheel cylinder 6 to 9 side is allowed to return to the master cylinder 3 side via the bypass flow passages 40 to 43. And check valves 44 to 47 for preventing the brake fluid from flowing from the master cylinder 3 side to the wheel cylinders 6 to 9 side.

Further, the depressurizing hydraulic pressure switching valves 26 to 29 are throttles for narrowing the amount of brake fluid recirculated from each wheel cylinder 6 to 9 to a predetermined amount in the flow path communicating with the downstream recirculation pipes 29 to 32. 50-53. Suction pumps 54 and 55 for sucking the brake fluid of the reservoirs 4 and 5 to circulate the fluid to the master cylinder 3 side, and reverse pumps arranged upstream of the suction pumps 54 and 55 are provided in the respective circulation pipe lines 33 and 34. Stop valve 56, 57
And check valves 58 and 59 arranged downstream of the suction pumps 54 and 55.

The suction pumps 54 and 55 are constantly driven by a pump motor (not shown) while the antilock braking force control is being executed. Then, the suction pump 54,
55 is a suction process when a pump plunger (not shown) moves down, and a discharge process when a pump plunger (not shown) moves up.

In the suction process, the suction pump 5 is used.
The check valves 56, 57 arranged upstream of the valves 4, 55 are opened, and the check valves 58, 59 arranged downstream of the suction pumps 54, 55 are closed. Then, in the discharge step, the check valves 56, 5 are provided upstream of the suction pumps 54, 55.
7 is closed, and check valves 58 and 59, which are arranged downstream of the suction pumps 54 and 55, are opened.

As described above, the suction pumps 54 and 55 are moved in accordance with the operating directions of the pump plungers of the suction pumps 54 and 55.
The brake fluid is recirculated to the master cylinder 3 by opening and closing the check valves 56, 57 and the check valves 58, 59 disposed upstream and downstream of the above. In the brake device having the anti-lock braking force control system configured as described above, when the brake pedal 1 is depressed, the master cylinder 3 increases the brake pressure to enter the pressure increasing mode. In this pressure increasing mode, the pressure increasing hydraulic pressure switching valves 12 to 15 are held in the open state, and the pressure reducing hydraulic pressure switching valves 16 to 19 are held in the closed state. Therefore, the increased brake pressure is applied to the first and second brake pipelines 10 and 11 and the supply pipeline 2.
It is supplied to each wheel cylinder 6-9 through 0-23 and supply lines 24-27, and each wheel is braked.

Then, for example, when the vehicle is running on a low μ road and is braked until just before the wheels are locked, the anti-lock braking force control system is switched to the pressure reducing mode or the holding mode. In this pressure reducing mode, the solenoid 12b of the pressure increasing hydraulic pressure switching valves 12 to 15 corresponding to the wheel immediately before being locked.
~ 15b is excited and switched to the closed state,
Solenoids 16b to 19 of the pressure reducing fluid pressure switching valves 16 to 19
b is switched to the valve open state. As a result, the brake pressure of the wheel cylinders 6 to 9 escapes to the reservoirs 4 and 5 via the recirculation pipes 29 to 32, so that the braking force on the wheels is released and the wheels are prevented from locking.

In the holding mode, the pressure increasing hydraulic pressure switching valve 1
2 to 15 and the pressure-reducing hydraulic pressure switching valves 16 to 19 are kept closed, and the brake pressure of the wheel cylinders 6 to 9 is held. During such anti-lock braking operation, the suction pumps 54 and 55 are always activated in order to prevent the master cylinder 3 from running out of brake fluid. Therefore, when the pressure reducing mode is set during the anti-lock braking operation and the pressure reducing hydraulic pressure switching valves 16 to 19 are opened, the brake fluid from the wheel cylinders 6 to 9 side flows out to the return pipe lines 29 to 32. Then, the brake fluid in the return conduits 29 to 32 is sucked into the return conduits 33 and 34 by the suction operation of the suction pumps 54 and 55.

After that, the brake fluid sucked by the suction pumps 54, 55 passes through the check valves 58, 59 and is returned to the first and second brake pipelines 10, 11. However, during the anti-lock braking operation, for example, when the rotation speed of each wheel becomes high, the pressure reducing mode is switched to the pressure increasing mode or the holding mode, and the pressure reducing hydraulic pressure switching valves 16 to 19 are closed and the pressure increasing hydraulic pressure is increased. The switching valves 12 to 15 open.

When the pressure reducing mode is switched to the pressure increasing mode or the holding mode in this way, the brake fluid continues to flow back to the master cylinder 3 side by the suction operation of the suction pumps 54 and 55, so that the reservoirs 4 and 5 are filled. The brake fluid is sucked into the return conduits 33 and 34.

The pressure increasing fluid pressure switching valves 12 to 15, the pressure reducing fluid pressure switching valves 16 to 19 and the suction pumps 54 and 55.
Operates according to a command from the antilock braking force control circuit 60. In addition, the anti-lock braking force control circuit 60,
A vehicle speed sensor 61 that detects the traveling speed of the vehicle, an acceleration sensor 62 that detects the acceleration of the vehicle, wheel speed sensors 63 to 66 that detect the wheel speed of each wheel, and the brake pedal 1
A brake switch 67 that switches from OFF to ON when is depressed is connected.

It is not necessary to provide the vehicle speed sensor 61 independently, and instead of providing the vehicle speed sensor 61, the vehicle body speed may be estimated from the wheel speed of each wheel detected by the wheel speed sensors 63 to 66. good. Therefore, the antilock braking force control circuit 60, when the brake switch 67 is turned on, based on the signals output from the vehicle speed sensor 61, the acceleration sensor 62, and the wheel speed sensors 63 to 66, the pressure increasing hydraulic pressure switching valve 12 described above. To 15 and the fluid pressure switching valve 16 for reducing pressure
The switching pressures of 19 to 19 are adjusted to adjust the brake pressure to each wheel so that each wheel does not lock while the vehicle is traveling.

When turning, the load acting on each wheel fluctuates inside and outside the cornering. Generally, the lateral acceleration reduces the load on the inside turning wheel and increases the load on the outside turning wheel. Therefore, if the same braking force is applied to each wheel during turning braking, the turning inside wheel may lock before the turning outside wheel, and the traveling state of the vehicle may become unstable.

Further, when the road surface friction coefficient (μ _a ) on which the wheels on the outside of the turn travel is smaller than the road surface friction coefficient (μ _b ) on which the wheels on the inside of the turn travel (μ _a <μ _b ) is a straddling road, during turning braking. If the same braking force is applied to each wheel,
A moment in the turning direction is generated and oversteer occurs,
This may result in unstable running conditions.

ROM of antilock braking force control circuit 60
In (not shown), a braking force control program is stored which controls the braking force applied to each wheel so that the wheels have the same slip ratio during turning braking. Then, the braking force control mode can be classified into three patterns of a pressure increasing mode, a holding mode, and a pressure reducing mode.

First, in the pressure increasing mode, the pressure increasing fluid pressure switching valves 12 to 15 and the pressure reducing fluid pressure switching valves 16 to 19 are not controlled, and the brake pressure from the master cylinder 3 is in the open state. It is directly supplied to the wheel cylinders 6 to 9 via the pressure switching valves 12 to 15. Further, in the holding mode, the solenoids 12b to 15b of the pressure increasing hydraulic pressure switching valves 12 to 15 are excited to switch the valve bodies 12a to 15a to the closed position.
As a result, the brake pressure to the wheel cylinders 6-9 is maintained.

In the pressure reducing mode, the braking force is weakened by controlling the pressure increasing hydraulic pressure switching valves 12 to 15 and the pressure reducing hydraulic pressure switching valves 16 to 19. That is, the solenoids 12b to 15b of the pressure increasing hydraulic pressure switching valves 12 to 15 are excited immediately before the wheels are locked, the valve bodies 12a to 15a are switched to the closed positions, and the pressure reducing hydraulic pressure switching valves 16 to 19 are changed. Solenoid 16
b to 19b are excited and the valve bodies 16a to 19a are switched to the valve opening positions, and the brake pressure to each wheel cylinder 6 to 9 is released to the reservoirs 4 and 5 to reduce the brake pressure.

Next, the braking force control processing executed by the antilock braking force control circuit 60 will be described with reference to FIG. In FIG. 2, when the driver depresses the brake pedal 1 to perform a braking operation, the brake switch 67 is turned on. Therefore, when the brake switch 67 is turned on in step S1 (hereinafter “step” is omitted), S
2, the lateral acceleration Gy detected by the acceleration sensor 62 and the wheel speed V _{WI of} each wheel detected by the wheel speed sensors 63 to 66 ( _I = FL, FR, RL, RR).
And the vehicle speed V _B detected by the vehicle speed sensor 61.
Read.

The vehicle body speed V _B may be calculated in a known manner by using the wheel speed V _WI of each wheel. Further, in S1, when the brake switch 67 is off, it is not necessary to perform the braking force control, and therefore the series of braking force control processes is ended without performing the following processes.

In the next step S3, it is checked whether or not the lateral acceleration Gy is positive, and the lateral acceleration Gy is checked.
Is positive (Gy> 0), it is determined that the traveling road is curving to the right, the process proceeds to S4, and the left wheel is set to the outer wheel side. However, the lateral acceleration Gy is positive (G
If y> 0), the process proceeds to S5, where the lateral acceleration G
Check if y is negative (Gy <0).

In S5, when the lateral acceleration Gy is negative (Gy <0), it is determined that the traveling road is curved to the left, the process proceeds to S6, and the right wheel is set to the outer wheel side. To do. However, in S5, the lateral acceleration G
When y is not negative, Gy = 0, and the vehicle is traveling straight. Therefore, since it is not necessary to individually control the braking force of the left and right wheels, the process proceeds to S7, and the normal antilock braking force control is performed.

In the next S8, the target turning inner wheel speed V _WI
* Is calculated from the following equation (1). V _WI * = {(V _B −d · Gy / 2V _B ) / (V _B + d · Gy / 2V _B )} · V _WO (1) where V _B is vehicle speed, Gy is lateral acceleration, and V _WO Is the outside wheel speed of turning and d is the tread. Therefore, the target turning inner wheel speed V _WI * is calculated as an optimum value according to the vehicle body speed V _B , the lateral acceleration Gy, and the turning outer wheel speed V _WO .

At the next step S9, the wheel speed sensors 63 to 66 are
Wheel speed V on the inside of turning detected by _WIIs expressed by equation (1)
Desired target turning inner wheel speed V_WI* Is less than
Check whether. In this S9, the wheel on the inside of the turn
Speed V_WIIs the target turning inside wheel speed V_WI* If less than
Is the wheel speed V inside the turn._WIIs slow, so proceed to S10
The brake pressure of the inner ring is reduced. That is, the hydraulic pressure for boosting
Of the switching valves 12 to 15, the switching valve on the inner ring side is closed, and
Open the inner ring side switching valve among the pressure reducing hydraulic pressure switching valves 16-19.
Let me speak.

However, in S9, if the inside turning wheel speed V _WI is not smaller than the target inside turning wheel speed V _WI *, the routine proceeds to S11, where the inside turning wheel speed V _WI is _{below the} target inside turning wheel speed V _WI *. Check if it is big. Accordingly, in S11, when the turning inner wheel speed V _WI is larger than the target turning inner wheel speed V _WI * Since wheel speed V _WI inner side of the turning is faster proceeds to S12, thereby boosted the inner ring of the brake pressure. That is, the pressure increasing hydraulic pressure switching valves 12 to 1
The switching valve on the inner ring side of 5 is opened, and the switching valve on the inner ring side of the depressurizing hydraulic pressure switching valves 16 to 19 is closed.

Further, in S11, the wheel speed V on the inside of the turn is determined.
_{When WI} is not greater than the target turning inner wheel speed V _WI *, V _WI = V _WI *, so the process proceeds to S13, and the inner wheel brake pressure is held. That is, the pressure increasing hydraulic pressure switching valve 12 to
The switching valve on the inner ring side of 15 is closed, and the switching valve on the inner ring side of the pressure-reducing hydraulic pressure switching valves 16 to 19 is also closed.

[0073] In this way the turning inner wheel speed V _WI and the vehicle speed V _B, the lateral acceleration Gy, the pressure-increasing fluid pressure switching so as to be equal to the target turning inner wheel speed V _WI * corresponding to the turning outer wheel speed V _WO Valves 12-15 and depressurizing hydraulic pressure switching valve 16-
The opening / closing control of 19 is performed to switch the brake pressure to the inner wheel side to any one of increased pressure, maintained pressure, and reduced pressure, and the braking force is controlled so that the turning inner wheel and the turning outer wheel have the same slip ratio.

Therefore, by controlling the brake pressure so that the slip ratios of the respective wheels are the same, it is possible to cancel the yaw moment that tends to occur during turning braking and improve the running stability during turning braking. The braking performance can be further improved and the braking distance can be shortened.

Here, the derivation of the equation (1) will be described. When the left wheel is the inner wheel and the right wheel is the outer wheel, the vehicle body speed V _B and the wheel speed of each wheel during traveling of the vehicle are as shown in FIGS. 3 and 4. Then, the front inner wheel speed V _wfi
If the rear inner wheel speed V _wri is considered separately, it can be expressed as the following equation.

_Front inner wheel speed V _wfi = (V _B −d · Gy / 2 V _B ) / (V _B + d · Gy / 2 V _B ) · V _wf (2) Rear inner wheel speed V _wri = (V _{B -d · Gy / 2V B) /} (V B + d · Gy / 2V B) · V wr ... (3) (2) (3) controls the brake pressure to stand.

Here, when the side slip angle is β and the turning yaw rate is Sy, Sy = (V _B / cos β)  (1 / R) = (V _B ² / R cos β)  (1 / V _B ) = {( V _B / cos β) ² / R} · cos β · 1 / V _B = Gy / V _B (4) Next, when the rotation yaw rate of the vehicle is Sz, Sz = (V _BfO −V _BfI ) / d = ( V _BrO −V _BrI ) / d (5) Here, when the sideslip angle β is zero and the turning yaw rate Sy is equal to the rotation yaw rate Sz (Sy = Sz), (V _BfO −V _BfI ) / d = Gy / V _B (V _BrO −V _BrI ) / d = Gy / V _B (6) Further, from (V _BfO + V _BfI ) / 2 = V _B , V _BfO = V _B + d · Gy / 2V _B (7) V _BfI = V _B −d · Gy / 2V _B (8) Also, here , ( _B BOO _cos δ−V _wfO ) / V _BfO cos δ = (V _BfI cos δ−V _wfI ) / V _BfI (9) However, δ is the front tire angle.

V _wfI = (V _BfI / V _BfO ) · V _wfO (10) Substituting the above equations (7) and (8) into this equation (10), the front inner wheel speed V _wfi = (V _B −d _{· Gy / 2V B) / (} V B + d · Gy / 2V B) · V wf ... (2) the rear inner wheel speed _{V wri = (V B -d ·} Gy / 2V B) / (V B + d · Gy / 2V _B ) · V _wr (3), and the above equations (2) and (3) are obtained.

Next, the braking force control processing of the second embodiment executed by the antilock braking force control circuit 60 will be described with reference to FIG. Since the entire structure of the braking force control device is the same as that of the first embodiment, the description thereof will be omitted. In FIG. 5, the processing of S21 to S27 is similar to that of S1 to S7 of FIG. In the present embodiment, it does not read the vehicle speed V _B at S22.

At S28, the target turning inner wheel speed V _WI *
Is calculated from the following equation (11). V _WI * = V _WI = (V _WO ² −2dGy) ^1/2 (11) where Gy is lateral acceleration and V _WO is the wheel speed outside the turning. Therefore, the target turning inside wheel speed V _WI * is calculated as an optimum value according to the lateral acceleration Gy and the turning outside wheel speed V _WO .

Since the processing of S29 to S33 is the same as that of S9 to S13 of FIG. 2 described above, the description thereof will be omitted. Thus, the turning inner wheel speed V _WI is equal to the lateral acceleration G.
y, the pressure increasing hydraulic pressure switching valves 12 to 15 and the pressure reducing hydraulic pressure switching valves 16 to 19 are controlled so as to be equal to the target turning inside wheel speed V _WI * determined according to the turning outside wheel speed V _WO. As a result, the braking pressure to the inner wheel side is switched to one of increased pressure, maintained pressure, and reduced pressure, and the braking force is controlled so that the turning inner wheel and the turning outer wheel have the same slip ratio.

Therefore, by controlling the brake pressure so that the slip ratios of the respective wheels are the same, the control of the respective wheels is controlled so that the slip ratio deviation between the inner wheel side and the outer wheel side during turning braking becomes zero. The power can be controlled to lock the inner wheel side and the outer wheel side at the same time during turning braking. Therefore, the yaw moment that tends to occur during turning braking can be canceled to improve the running stability during turning braking.
The braking performance can be further improved and the braking distance can be shortened.

Here, the derivation of the equation (11) will be described. The above equation (11) can be expressed as follows. V _WO ² −V _WI ² = 2dGy (12) Then, when the left and right front wheels are considered, the front-side inner-outer wheel speed difference is as follows. V _WO- V _WI = (1-S _fO ) V _BfO · cos δ- (1-S _fI ) V _BfI · cos δ = (V _BfO −V _BfI ) · cos δ− (S _fO · V _BfO −S _fI · V _BfI ) · Cos δ (13) Here, considering the control in which the slip amount difference (S _fO · V _BfO −S _fI · V _BfI ) of the front left and right wheels in the second term on the right side of the equation (13) is zero, _WO −V _WI = (V _BfO −V _BfI ) · cos δ (14), further cos δ≈1, and V _WfO −V _WfI = dGy / V _B (15) from the above equation (6). Here, if V _B = (V _WfO + V _WfI ) / 2, then V _WfO ² −V _WfI ² = 2dGy (16) similar to the equation (12) is obtained. Similarly to the above, the following equation is also applied to the rear wheel side.

V _WrO ² −V _WrI ² = 2dGy (17) Next, referring to FIG. 6, the anti-lock braking force control circuit 60
The braking force control processing of the third embodiment executed by the above will be described. Since the entire structure of the braking force control device is the same as that of the first embodiment, the description thereof will be omitted.

In FIG. 6, when the brake switch 67 is turned on in S41, the process proceeds to S42 and the wheel speed sensor 63
Wheel speed V _WI ( _I = F) of each wheel detected by
L, FR, RL, RR) is read. Incidentally, in S41, when the brake switch 67 is off, it is not necessary to perform the braking force control, so the series of braking force control processes is ended without performing the following processes.

In the next S43, it is checked whether the left wheel speed VWL is faster than the right wheel speed VWR, and the left wheel speed VWL is faster than the right wheel speed VWR (VWL>
During VWR), it is determined that the traveling road is curved to the right, and the process proceeds to S44, where the left wheel is set to the outer wheel side. However, when the left wheel speed VWL is not faster than the right wheel speed VWR, the process proceeds to S45, and it is checked whether the left wheel speed VWL is slower than the right wheel speed VWR (VWL <VWR).

In S45, when the left wheel speed VWL is slower than the right wheel speed VWR (VWL <VWR), it is determined that the traveling road is curved to the left, the process proceeds to S46, and the right wheel is moved to the outer wheel side. Set to. However, in S45, when the left wheel speed VWL is not slower than the right wheel speed VWR, VWL = VWR, and the vehicle is traveling straight. Therefore, since it is not necessary to individually control the braking force of the left and right wheels, the process proceeds to S47 and the normal antilock braking force control is performed.

At the next step S48, it is checked whether the wheel speed difference between the inner wheel and the outer wheel is a value larger than a predetermined value K (V _WO ² -V _WI ² > K). In S48, when the wheel speed difference between the inner and outer rings is less than the predetermined value ^{_{K (V WO 2 -V WI 2}} ≦ K) Since the wheel speed difference between the inner and outer rings is small, control of the inner and outer rings It is not necessary to control the power individually, and a series of braking force control processing is ended.

[0089] However, in S48, the wheel speed difference is the predetermined value K greater than the inner ring and the outer ring (V _WO ² -V _WI ^2>
If it is K), the process proceeds to S49. In the next S49, the target turning inner wheel speed V _WI * is calculated from the following equation (18). V _WI * = (V _WO ² −K) ^1/2 (18) where V _WO is a wheel speed on the outside of the turn, and K is a coefficient determined by the vehicle speed.

Since the processing of S50 to S54 is the same as that of S9 to S13 of FIG. 2 described above, its explanation is omitted. In this way, the inside turning wheel speed V _WI is obtained based on the outside turning wheel speed V _WO and the target inside turning wheel speed V _{WI is obtained.}
The pressure-increasing hydraulic pressure switching valves 12 to 15 and the pressure-decreasing hydraulic pressure switching valves 16 to 19 are controlled to be equal to *, and the brake pressure to the inner wheel side is switched to either pressure-increasing, holding, or pressure-decreasing and turning The braking force is controlled so that the inner wheel and the turning outer wheel have the same slip ratio.

Therefore, by controlling the brake pressure so that the slip ratios of the respective wheels are the same, the control of the respective wheels is controlled so that the deviation of the slip ratio between the inner wheel side and the outer wheel side during turning braking becomes zero. The power can be controlled to lock the inner wheel side and the outer wheel side at the same time during turning braking. Therefore, the yaw moment that tends to occur during turning braking can be canceled to improve the running stability during turning braking.
The braking performance can be further improved and the braking distance can be shortened.

Moreover, in this embodiment, since the target turning inner wheel speed V _WI * can be obtained regardless of the lateral acceleration Gy, it can be applied as a backup control when the acceleration sensor 62 fails. Here, the derivation of the equation (18) will be described.

In this embodiment, the brake pressure on the inner wheel side is controlled so that V _WO ² -V _WI ² = K. for that reason,
Considering the left and right wheels of the front wheels, _setting V _wfo ² −V _wfi ² = K results in V _wfo −V _wfi = K / 2V _B , and further (d · Gy / V _B ) − (S _fO・ V _BfO −S _fI・ V _BfI )
= K / 2V _B, and therefore the slip amount difference can be expressed by the following equation.

(D · Gy−K / 2) / V _B = S _fO · V _BfO −S _fI · V _BfI (19) That is, when the lateral acceleration is Gy> K / 2d, the slip amount of the outer wheel is (D ・ Gy-K / 2) /
The inner and outer wheels are controlled to lock at the same time by increasing V _B.

Further, for the rear wheels as well, the brake pressure on the inner wheel side is controlled in the same manner as the equation (19). Next, referring to FIG. 7, the fourth step executed by the antilock braking force control circuit 60 will be described.
The braking force control process of the embodiment will be described.

In FIG. 7, when the brake switch 67 is off in S71 and there is no braking, the routine proceeds to S72. In addition, in S71, when braking with the brake switch 67 being ON, S
Proceeding to 67, normal antilock braking force control is performed. The following processing of S62 to S67 is performed by S1 to S7 of FIG.
Since it is similar to the above, the description thereof is omitted.

At S68, the target turning outer wheel speed V _WO *
Is calculated from the following equation (1). V _WO * = {(V _B −d · Gy / 2V _B ) / (V _B + d · Gy / 2V _B )} · V _WI (20) where V _B is vehicle speed, Gy is lateral acceleration, and V _WI Is the inside wheel speed of turning and d is the tread. Therefore, the target turning inner wheel speed V _WI * is calculated as an optimum value according to the vehicle body speed V _B , the lateral acceleration Gy, and the turning inner wheel speed V _WI .

In the next S69, the wheel speed sensors 63-66.
It is checked whether or not the turning outside wheel speed V _WO detected by the formula (20) is smaller than the target turning outside wheel speed V _WO * obtained by the equation (20). In this step S69, if the outside turning wheel speed V _WO is smaller than the target outside turning wheel speed V _WO *, the outside turning wheel speed V _WO is slow, so S70.
To reduce the brake pressure on the outer wheels. That is, the switching valve on the outer ring side of the pressure increasing hydraulic pressure switching valves 12 to 15 is closed,
Further, among the pressure-reducing hydraulic pressure switching valves 16 to 19, the switching valve on the outer ring side is opened.

However, in S69, if the turning outside wheel speed V _WO is not smaller than the target turning outside wheel speed V _WO *, the process proceeds to S71, in which the turning outside wheel speed V _WO exceeds the target turning outside wheel speed V _WO *. Check if it is big. Accordingly, in S71, when the turning outer wheel speed V _WO is larger than the target locus outer wheel speed V _WO * Since wheel speed V _WO of the turning outer faster proceeds to S72, thereby boosted brake pressure of the outer ring. That is, since the turning is not braking, the rotational speeds of the pumps 54 and 55 are increased, and the switching valve on the outer wheel side of the pressure increasing hydraulic pressure switching valves 12 to 15 is opened.
Further, among the pressure reducing hydraulic pressure switching valves 16 to 19, the switching valve on the outer ring side is closed. As a result, the brake pressure of the outer wheel is increased, and the braking force is controlled so that the turning outer wheel and the turning inner wheel have the same slip ratio.

Further, in S71, the wheel speed V on the outside of the turn is determined.
_{When WO} is not greater than the target turning outer wheel speed V _WO *, V _WO = V _WO *, so the routine proceeds to S73, where the brake pressure of the outer wheel is held. That is, the pressure increasing hydraulic pressure switching valve 12 to
The switching valve on the outer ring side of 15 is closed, and the switching valve on the outer ring side of the pressure-reducing hydraulic pressure switching valves 16 to 19 is also closed.

As described above, during non-braking of the turning, the turning outer wheel speed V _WO is made equal to the target turning outer wheel speed V _WO * corresponding to the vehicle body speed V _B , the lateral acceleration Gy, and the turning inner wheel speed V _WI. Further, the pressure increasing hydraulic pressure switching valves 12 to 15 and the pressure reducing hydraulic pressure switching valves 16 to 19 are controlled to be opened and closed, and the brake pressure to the outer wheel side is switched to either pressure increasing, holding, or pressure reducing so that the turning outer wheel and the turning inner wheel are connected. The braking force is controlled so that the slip ratio becomes the same.

That is, as described above, when the vehicle is not turning, the target turning outside wheel speed V _WO * for generating the anti-spin moment is generated based on the vehicle body speed V _B , the lateral acceleration Gy, and the turning inside wheel speed V _WI. Calculate and calculate turning outside wheel speed V _WO
By applying a braking force to the outer wheels so that the target turning outer wheel speed is V _WO *, it is possible to generate an optimum anti-spin moment during non-braking of the turning and maintain traveling stability.

Therefore, during non-turning braking, the brake pressure to the outer wheels is increased and the brake pressure is controlled so that the slip ratio of each wheel becomes the same, so that the yaw moment during non-turning braking is controlled. It is possible to cancel and improve the running stability when turning is not braking. Note that the above formula (20) can be derived in the same manner as in the case of the above-described first embodiment, and therefore its explanation is omitted here.

Next, the braking force control processing of the fifth embodiment executed by the antilock braking force control circuit 60 will be described with reference to FIG. In FIG. 8, the processing of S81 to S87 is similar to that of S61 to S67 of FIG.

At S88, the target turning outer wheel speed V _WO *.
Is calculated from the following equation (21). V _WO * = (V _WI ² + 2dGy) ^1/2 (21) Then, the processes of S29 to S33 are the same as S6 of FIG. 7 described above.
Since it is the same as 9 to S73, its description is omitted.

[0106] Thus, turning non-braking, the turning outer wheel speed V _WO lateral acceleration Gy, the target turning outer wheel speed V _WO * becomes equal manner intensifying fluid pressure corresponding to the turning inner wheel speed V _WI Switching valves 12 to 15 and pressure reducing hydraulic pressure switching valve 16 to
The opening / closing control of 19 is performed to switch the brake pressure to the outer wheel side to any one of pressure increase, holding, and pressure reduction, and the braking force is controlled so that the turning outer wheel and the turning inner wheel have the same slip ratio.

Therefore, during non-turning braking, the brake pressure on the outer wheel side is increased and the brake pressure is controlled so that the slip ratio of each wheel becomes the same, so that the inner wheel side and the outer wheel during non-turning braking are controlled. By controlling the braking force of each wheel so that the deviation of the slip ratio from the side becomes zero, the inner wheel side and the outer wheel side at the time of turning braking can be locked at the same time. Therefore, the yaw moment during turning non-braking can be canceled to improve running stability during turning braking.

Since the above equation (21) can be derived in the same manner as in the case of the second embodiment described above, its explanation is omitted here. Next, a braking force control process of the sixth embodiment executed by the antilock braking force control circuit 60 will be described with reference to FIG.

In FIG. 9, the brake switch 67 is executed in S101.
When is off and there is no braking, the process proceeds to S102. Also, S10
In No. 1, when the brake switch 67 is on and the vehicle is braking, the routine proceeds to S107, where normal antilock braking force control is performed. The processing of the next S102 to S108 is the same as that shown in FIG.
Since it is the same as S42 to S48, description thereof will be omitted.

In the next step S109, the target turning outer wheel speed V _WO * is calculated from the following equation (22). V _WO * = (V _WI ² −K) ^1/2 (22) where V _WI is a wheel speed on the inside of the turn and K is a coefficient determined by the vehicle speed.

Since the processing of S110 to S114 is similar to that of S89 to S93 of FIG. 8 described above, its explanation is omitted. Thus, turning the non-braking, the turning outer wheel speed V _WO is turning inside wheel speed V _WI target turning outer wheel speed V corresponding to _WO * becomes equal manner intensifying fluid pressure switching valve 12
˜15 and the depressurizing hydraulic pressure switching valves 16 to 19 are controlled to be opened / closed so that the brake pressure to the outer wheel side is switched to any one of pressure increasing, holding and depressurizing so that the outer turning wheel and the inner turning wheel have the same slip ratio. The braking force is controlled.

Therefore, during non-turning braking, the brake pressure to the outer wheels is increased to control the brake pressure so that the slip ratios of the respective wheels are the same. By controlling the braking force of each wheel so that the deviation of the slip ratio from the outer wheel side becomes zero, it is possible to simultaneously lock the inner wheel side and the outer wheel side during turning braking. Therefore,
The yaw moment that tends to occur during turning braking can be canceled to improve running stability during turning braking, braking performance can be further improved, and the braking distance can be shortened.

Moreover, in this embodiment, since the target turning outer wheel speed V _WO * can be obtained regardless of the lateral acceleration Gy, it can be applied as a backup control when the acceleration sensor 62 fails. Next, the braking force control processing of the seventh embodiment executed by the antilock braking force control circuit 60 will be described with reference to FIG.

The processing shown in FIG. 10 is executed when the vehicle speed becomes equal to or higher than a predetermined value during non-braking or at predetermined time intervals. In the figure, in S121, the lateral acceleration Gy detected by the acceleration sensor 62 and the wheel speed V _WI ( _I = FL, FR, R of each wheel detected by the wheel speed sensors 63 to 66).
L, RR) are read.

At the next step S122, the wheel speed sensors 63 to 6 are
The abnormality determination of 6 is performed. That is, among the wheel speeds of the wheels detected by the wheel speed sensors 63 to 66, when one wheel speed is an abnormally large value or an abnormally small value as compared with the other wheel speeds, the wheel speed is It is determined that the sensors 63 to 66 have an abnormality. In that case, since the braking force control cannot be performed for each wheel, the process proceeds to S123, the braking force control during turning is stopped, and the control is stopped and the wheel speed sensors 63 to 66 indicate that there is an abnormality (Fig. (Not shown).

Further, in S122, the wheel speed sensor 63
When ~ 66 is normal, the routine proceeds to S124, where the theoretical estimated lateral acceleration Gy * is calculated from the wheel speed V _WI . In S124, the following equation is calculated. ^{_{Gy * = (V wo 2 -V}} WI 2) / 2d ... (23) In the next S125, the lateral acceleration Gy (measured value) detected by the acceleration sensor 62, the estimated obtained from the above equation the lateral acceleration Gy * The allowable range (± α) of is compared. Then, in S126, Gy> Gy * + α or Gy <
If it is not Gy * -α, the measured value by the acceleration sensor 62 is within the allowable range (± α) of the estimated lateral acceleration Gy *, so the routine proceeds to S127, where it is determined that the acceleration sensor 62 is normal.

In this case, the process proceeds to S128 and the above-mentioned FIG.
Alternatively, the processing of the flowchart shown in FIG. 5 is executed to control the brake pressure on the inner wheel side during turning braking so as to reduce the braking pressure so that each wheel has the same slip ratio. However, in S126, when Gy> Gy * + α or Gy <Gy * -α, the measured value by the acceleration sensor 62 is out of the allowable range (± α) of the estimated lateral acceleration Gy *. Advance, acceleration sensor 62
It is determined that there is an abnormality. Then, the acceleration sensor 6
A display (not shown) indicates that 2 is abnormal.

Then, the procedure proceeds to S128 and the above-mentioned FIG.
The processing of the flowchart shown is executed. That is, the acceleration
The wheel speed without using the lateral acceleration detected by the sensor 62.
Degree V _WIThe brake pressure on the inner wheel side during turning braking is reduced based on
Control so that each wheel has the same slip ratio
To control the braking force.

Accordingly, the acceleration sensor 62 normally accelerates laterally.
When the degree can be measured, the wheel speed V _WIAnd lateral acceleration Gy
The braking force control is performed based on the
If the measured value is abnormal, the wheel speed V_WIBased on
Power control can be performed. Therefore, the wheel speed sensor
When there is an abnormality in 63 to 66 or the acceleration sensor 62,
Control the braking force without using these measured values.
The wheel speed sensor 63-
66 or the abnormal value detected by the acceleration sensor 62.
The braking force control is prevented based on
Driving stability is improved and braking during turning braking
The reliability of force control can be further enhanced.

Here, the derivation of the above equation (23) will be described. When the vehicle is traveling in a steady circular turn at the speed V _B , the lateral acceleration Gy satisfies the following relational expression between the vehicle body speed V _B and the yaw rate γ. Gy = V _B γ (24) Further, the following formula is established under non-braking and under general traveling conditions except for extremely low speed.

Γ = (V _wo −V _WI ) / d (25) Further, it can be approximated as V _B = (V _wo + V _WI ) / 2 (26). Then, the above (24) (25) (26)
Therefore, Gy = V _B γ = {(V _wo + V _WI ) / 2} {(V _wo −V _WI ) / d} = (V _wo ² −V _WI ² ) / 2d Thus, the above (23) The formula is obtained.

Next, the braking force control processing of the eighth embodiment executed by the antilock braking force control circuit 60 will be described with reference to FIGS. 11 to 13. In the eighth embodiment, when the road surface on which the vehicle turns is a so-called straddling road (the road surface on which the wheels on the outside of the turn travel are lower than the inside of the turn), the inner wheel on the rear side is a high μ road. Therefore, the braking force distribution control is not performed, and since the rear outer wheel is on the low μ road, the braking force distribution control is performed. In that case, the braking force distribution control is performed first on the rear outer wheel, so that the yaw rate is promoted by the difference in braking force between the rear left and right wheels.

Further, when the front outer wheel is used as a reference to control the braking force of other wheels while traveling on the above-mentioned straddle road, the front outer wheel travels on a low μ road and the rear inner wheel is high. Since the vehicle runs on the μ road, it is more difficult to control the braking force of each wheel than when the inner wheel and the outer wheel travel on the same μ road.

Therefore, in this embodiment, it is determined whether or not the vehicle is traveling on the crossing road, and when the vehicle is traveling on the crossing road, the braking force of other wheels is controlled with the front inner wheel as a reference. In addition, the yaw rate is suppressed by controlling the brake pressure so that the braking force becomes low.

Since steps S141 to S147 in FIG. 11 are the same as steps S1 to S7 in FIG. 2, the description thereof will be omitted here. In the next 148, the target front inner wheel speed V _WFI * is calculated from the following equation (27). V _WFI * = {(V _B −d · Gy / 2V _B ) / (V _B + d · Gy / 2V _B )} ・ V _WFO (27) where V _B is vehicle speed, Gy is lateral acceleration, and V _WFO Is the front outer wheel speed, and d is the tread. Therefore, the target front inner wheel speed V _WFI * is the vehicle body speed V _B and the lateral acceleration G.
y, an optimum value is calculated according to the front outer wheel speed V _WFO .

Then, in S149, the target rear outer wheel speed V _WRO * and the target rear inner wheel speed V _WRI * are calculated. In this case, the target rear outer wheel speed V _WRO * becomes the same as the front outer wheel speed V _WFO , and the target rear inner wheel speed V _WRI.
* Is the same as the target front inner wheel speed V _WFI * determined by the above equation (27).

In the next S150, the rear inner wheel speed V _WRI
And the difference ΔV between the target rear inner wheel speed V _WRI * is calculated.
Then, the procedure proceeds to S151, where the difference ΔV (= V _WRI −V _WRI) between the rear inner wheel speed V _WRI and the target rear inner wheel speed V _WRI *.
Check if *) is positive. This S151
Then, the rear inner wheel speed V _WRI and the target rear inner wheel speed V _WRI
Whether or not the traveling road surface is a so-called crossing road is determined based on the difference ΔV from _WRI *. When it is not a crossing road, the inner wheel side and the rear wheel side are the same μ, so normal braking force control is performed. When the road is a straddle road, reduce the brake pressure to each wheel to a low μ.
The brake pressure is controlled according to the road.

Therefore, in S151, ΔV ≦ 0
If it is, it is determined that the road surface μ on the inner wheel side and the road surface μ on the outer wheel side are the same or the inner wheel side is a low μ road, and the process proceeds to S152, where the braking force control is performed so that each wheel reaches the target wheel speed. . However, if ΔV> 0 in S151, the routine proceeds to S153, where it is checked whether the target rear outer wheel speed V _WRO * is greater than the rear outer wheel speed V _WRO . If V _WRO *> V _WRO in S153, the _flow advances to S154 to set flags F1 = 1 and F2 = 0 (pressure reduction mode).

In S153, V _WRO * _{≤V WRO}
If it is, the process proceeds to S155, and the target rear outer wheel speed V
Check if _WRO * is less than rear outer wheel speed V _WRO . If V _WRO * <V _WRO in S155, the process proceeds to S156, and flags F1 = 0 and F2 = 0.
Set to (pressure increase mode).

However, if V _WRO * <V _WRO is not satisfied in S155, the flow proceeds to S157, where flags F1 = 0 and F2 = 1.
Set to (hold mode). In this way, the flag F of the rear outer wheel is determined based on the rear outer wheel speed V _WRO according to the road surface μ.
1 and F2 are set. In the next S158, the above S15
4, flags F1 and F2 set in S156 and S157
It is checked whether or not the flag F1 = 1. If the flag F1 is not 1 in S158, S159
Then, it is checked whether the target rear inner wheel speed V _WRI * is larger than the rear inner wheel speed V _WRI . If S1
In 59, when V _WRI *> V _WRI , S160
Then, the flag F1 = 1 (pressure reduction mode) is set.

In S159, V _WRI *> V _WRI
If not, the process proceeds to S161 to check whether the flag F2 = 1 is set. If the flag F2 = 1 is not set in S161, S
Proceed to 162. In this S162, it is checked whether the target rear inner wheel speed V _WRI * is lower than the rear inner wheel speed V _WRI . If, in S162, V _WRI * <V
_If it is not _WRI , the process proceeds to S163, and the flag F2 = 1 (hold mode) is set. Thus, the rear inner wheel speed V
The flag of the rear inner ring is set according to _WRI .

Then, in the next S164, the flags F1,
It is checked whether the flag F1 = 1 in F2. When one of the rear inner wheel and the rear outer wheel has the flag F1 = 1 in S164, the process proceeds to S165, in which the brake pressure of the left and right rear wheels is reduced. However, if the flag F1 is not 1 in S164, the process proceeds to S166 and the flag F2 is set.
Check if = 1. When one of the rear inner wheel and the rear outer wheel has the flag F2 = 1 in S166, the process proceeds to S167, and the brake pressures of the left and right rear wheels are held.

When the flag F2 is not 1 in S166, the process proceeds to S168 and the brake pressure of the left and right rear wheels is increased.
That is, when the flag F1 = 1 is not satisfied, and the flag F2 =
When it is not 1, the brake pressure of the left and right rear wheels is increased, and the yaw rate is suppressed during turning braking. In this way, the rear wheels are controlled to have the same wheel speed, and the moment in the turning direction due to the braking force difference between the turning inner wheel and the turning outer wheel is suppressed.

In the next S169, the front inner wheel speed V
_WFIIs the target front inner wheel speed calculated in S148
V_WFISo that it becomes *, for example, as shown in FIG.
Performs braking force control. Therefore, as described above, turning braking
Time, vehicle speed V_B, Front outer wheel speed V before turning _WFO, Yokoka
The left and right wheels are locked at the same time based on the speed Gy
Target wheel speed V of the inner side wheel_WFI* Is calculated, and further turning control
When moving, the outer wheel speed V before turning_WFOAfter turning based on
Outer wheel target wheel speed V_WRO* Is calculated and the front side of turning
Outer wheel speed V_WFOAfter turning, the inner wheel after turning and after turning
Target wheel speed V of the outer side wheel_WRI*, V_WROCalculate *.
Then, compare each wheel speed with each target wheel speed and
Supply to each wheel so that the wheel speed of the wheel becomes the target wheel speed
Adjust the brake pressure to lock each wheel simultaneously
Thus, the braking force is distributed to each wheel.

Further, at the time of turning, when it is detected that the road surface on which the outer wheel travels has a lower friction road (lower μ road) than the road surface on which the inner wheel travels, the brake pressure to the inner wheel after turning and the outer wheel after turning is detected. In order to control the brake pressure to the inner wheel after turning and the outer wheel after turning by comparing the pressure increasing, holding, pressure reducing commands and selecting the command to make the brake pressure to the lower pressure side, if the outer wheel side is a low μ road, If the brake pressure to the wheels on the outer side of the turning of the rear wheels is first reduced, a moment that promotes turning of the vehicle is generated and oversteer occurs, but in such a case, the rear wheels are controlled to the same wheel speed. It is possible to prevent a moment in the turning direction from being generated due to a braking force difference between the turning inner wheel and the turning outer wheel.

Next, a braking force control system according to a ninth embodiment of the present invention will be described with reference to FIGS. 14 and 15. The braking force control device of this embodiment can be realized by using the system configuration shown in FIG. First mentioned above
The eighth embodiment determines whether or not the braking force control should be executed based on whether or not the lateral acceleration Gy acting on the vehicle exceeds a predetermined threshold value. The braking force control device of the present embodiment is characterized in that the threshold value used for such determination is changed based on the vehicle speed detected by the vehicle speed sensor 61.

FIG. 14 shows an example of a map stored in the antilock braking force control circuit 60 in order to realize the above function. In the map shown in FIG. 14, the vehicle body speed is a predetermined value V _0.
In the following areas, the threshold value for determining the control start is the first threshold value (0.6 G in this embodiment), and in the area where the vehicle body speed exceeds the predetermined value V ₀ , the control start is determined. The threshold value is set to the second threshold value (0.2 G in this embodiment).

In a region where the vehicle body speed is low, it is sufficient to start the braking force control so that stable vehicle behavior can be obtained in such a situation after the vehicle transitions to a turning state with a high lateral acceleration Gy. Further, if the braking force control is executed in response to a slight lateral acceleration Gy in such a low vehicle speed range, unnecessary braking force control is frequently performed, which is complicated. From this point of view, it is appropriate to set the threshold value for determining the start of control to a relatively high value in a region where the vehicle speed is low.

On the other hand, in order to obtain the effect of the braking force control when the vehicle speed is high and an operation involving a temporary and sudden behavior change is performed, such as a high-speed lane change, the vehicle behavior changes. It is necessary to start the braking force control promptly after starting the operation. Therefore, in a region where the vehicle body speed is high, it is appropriate to set the threshold value for determining the start of control to a relatively low value. First threshold value (0.6G) and second threshold value (0.3G) shown in FIG.
Is a value set for the purpose of satisfying such a requirement.

FIG. 15 is a flowchart showing an example of a routine executed by the antilock braking force control circuit 60 so as to switch the threshold value used for determining the starting condition of the braking force distribution control according to the vehicle body speed. When the routine shown in FIG. 15 is started, first, in S180, it is determined whether or not the brake switch 67 is in the on state. If the brake switch 68 is not in the ON state, it is determined that the vehicle is not in the braking state, and the routine of this time is ended without proceeding any further processing. On the other hand, if it is determined that the brake switch 67 is in the ON state, then S18
The process 1 is executed.

At S181, it is judged if the operation of the antilock brake system (hereinafter referred to as ABS) is required. As a result, when it is determined that the operation as the ABS is requested, the ABS control for realizing the operation is executed in S182, and then the routine of this time is ended. On the other hand, if it is determined that the ABS operation is not required, then S
The process of 183 is performed.

At S183, the threshold value Gy ₀ used for determining the starting condition of the braking force distribution control is determined based on the vehicle speed. In this routine, the threshold value Gy ₀ is
It is determined by searching the map shown in FIG. 14 with the vehicle speed detected by the vehicle speed sensor 61. More specifically, Gy ₀ is the 0.6G when the vehicle speed is V ₀ or less, and if the vehicle speed exceeds the V ₀ Gy ₀ is determined to be 0.2 G.

Upon completion of the above processing, next, step S184
In comparison with the threshold Gy ₀ , the acceleration sensor 62
It is determined whether or not the absolute value | Gy | of the lateral acceleration Gy detected by. As a result, when Gy ₀ <| Gy | is not satisfied, it is determined that the lateral acceleration Gy that requires the braking force distribution control is not applied to the vehicle, and this routine is ended. .

On the other hand, when it is determined that Gy ₀ <| Gy | is established, it is determined that the braking force distribution control needs to be executed, and the processing required for the distribution control in S185 (specifically, the above-mentioned figure is executed). 2, S2 to S13 shown in FIG. 2, S22 to S33 shown in FIG. 5, and S42 to S54 shown in FIG.
Processing, the processing of S62 to S73 shown in FIG. 7, the processing of S81 to S93 shown in FIG. 8, and the processing of S102 to S114 shown in FIG.
Processing, or S142 to S16 shown in FIGS.
9) is executed, this routine is ended.

According to the above-described braking force control device, the braking force distribution control is properly executed under the condition that a relatively large lateral acceleration Gy is generated during low speed traveling, and the excellent responsiveness is exhibited during high speed traveling. Based on this, the braking force distribution control is executed. Therefore, according to the braking force control device of the present embodiment, after the vehicle shifts to the turning state, the braking force distribution control can be started at an appropriate timing according to the vehicle body speed.
In the above-described embodiment, the antilock braking force control circuit 60 executes the process of S183 to implement the threshold value changing means.

Next, a braking force control system according to the tenth embodiment of the present invention will be described with reference to FIGS. The braking force control device of this embodiment can be realized by using the system configuration shown in FIG. The braking force control device of the present embodiment is characterized in that a high braking ability can be secured by controlling the braking force of the front wheels and the braking force of the rear wheels to an appropriate distribution ratio. .

FIG. 16 shows the braking force generated by the front wheels of the vehicle (hereinafter referred to as the front braking force) Ff on the horizontal axis, and the braking force generated by the rear wheels of the vehicle on the vertical axis (hereinafter referred to as the rear braking force). (Hereinafter referred to as “Fr”) represents the braking force coordinates representing Fr. FIG.
The straight line indicated by indicates that the friction coefficient μ between the wheel and the road surface is 1.
The front lock limit line in the case of 0 is shown. When the front braking force Ff and the rear braking force Fr are brought into a state where they coincide with a point on the straight line during the braking operation of the vehicle, the front wheels shift to the locked state at that time. The lock of the front wheel is less likely to occur as the load applied to the front wheel is larger. Further, the larger the braking force, the larger the load applied to the front wheels due to the movement of the load.
Therefore, as shown in FIG. 16, the front lock limit line is a straight line rising to the right.

The straight line indicated by in FIG. 16 is the rear lock limit line when μ = 1.0. When the front braking force Ff and the rear braking force Fr are brought into a state where they coincide with a point on the straight line during the braking operation of the vehicle, the rear wheels shift to the locked state at that time. The larger the load applied to the rear wheel, the less likely the rear wheel will be locked. The larger the braking force, the smaller the load applied to the rear wheel due to the load movement. For this reason,
As shown in FIG. 16, the rear lock limit line is a straight line descending to the right.

The straight line shown by in FIG. 16 is the braking force ideal distribution line. When the braking force that matches the coordinate values (Ff, Fr) on the ideal braking force distribution line is exerted on the front wheel and the rear wheel during the braking operation, respectively, the wheel speed V _{Wf of the} front wheel and the wheel speed V _{Wr of the} rear wheel are obtained. Can be matched. The ideal distribution line of the braking force becomes a curve as shown in FIG. 16 due to the influence of the load change caused by the braking force.

The braking ability of the vehicle is better as the sum of the maximum value of the front braking force Ff and the maximum value of the rear braking force Fr is larger. Therefore, in order to obtain a high braking ability in the vehicle, (Ff, F
It is desirable that the distribution ratio of Ff and Fr be controlled so that the locus of r) passes through the intersection Q of the front lock limit line and the rear lock limit line.

On the other hand, when one of the wheels shifts to the locked state, the case where the front wheels are locked prior to the rear wheels is better than the case where the rear wheels are locked prior to the front wheels. The behavior is stable. Therefore, in the sense of increasing the stability at such a limit, (Ff,
Fr) 's locus penetrates the front lock limit line,
It is desirable that the distribution ratio of Ff and Fr be controlled.

A polygonal line shown by in FIG. 16 shows a locus of (Ff, Fr) which can be realized by using a proportioning valve (hereinafter referred to as P valve). The P valve is a pressure reducing valve incorporated in a hydraulic path that communicates with a wheel cylinder arranged on the rear wheel. The P valve supplies the brake hydraulic pressure supplied to the wheel cylinders of the front wheels to the wheel cylinders of the rear wheels as it is until the brake hydraulic pressure reaches a predetermined pressure. When the brake hydraulic pressure exceeds a predetermined pressure, the P valve supplies the brake hydraulic pressure, which is the hydraulic pressure supplied to the wheel cylinders of the front wheels, at a predetermined ratio to the wheel cylinders of the rear wheels. Therefore, the P-valve characteristic has a polygonal line as shown in FIG. The specifications of the P valve are set so that the P valve characteristic intersects with the front lock limit line in the vicinity of an intersection Q between the front lock limit line and the rear lock limit line. By making such a setting, both of the above two requirements are achieved.

However, what can be controlled by the P valve is the ratio between the brake hydraulic pressure supplied to the front wheel cylinder and the brake hydraulic pressure supplied to the rear wheel cylinder. Even if the ratio of the brake hydraulic pressure is the same, if the load balance between the front wheels and the rear wheels changes due to the change in the loading state, the relationship between the front lock limit line and the rear lock limit line and the P valve characteristic changes. To do. Therefore, in a vehicle such as a commercial vehicle in which the load balance between the front and rear wheels changes greatly depending on the loading state, it is difficult to always intersect the P valve characteristic with the front lock limit line near the point Q.

Conventionally, in order to make up for the drawbacks of the P valve, a load sensing proportioning valve (hereinafter referred to as LSPV) has been used in commercial vehicles and the like. The LSPV is a P valve having a function of changing the damping ratio of the brake hydraulic pressure supplied to the wheel cylinders of the rear wheels according to the load of the vehicle. Specifically, when the load is large, the damping ratio of the brake hydraulic pressure is small,
Further, it has a function of changing the damping ratio of the brake hydraulic pressure largely when the load is small. According to LSPV, it is possible to realize the P valve characteristic that intersects with the front lock limit line in the vicinity of the point Q regardless of the loading state of the vehicle. Therefore, according to LSPV, the braking force of the rear wheels can be more effectively exerted as compared with the P valve.

In the system of this embodiment, the wheel speed of each wheel can be controlled by controlling the braking force. Therefore, by controlling the braking force of each wheel, for example, the wheel speed V _{Wf of the} front wheels and the wheel speed V _W of the rear wheels are controlled.
It is also possible to control _{Wr in the} same way. When such a control is executed during the braking operation, the locus of (Ff, Fr) always coincides with the ideal braking force distribution line, and the braking force characteristics similar to those when LSPV is used without using LSPV. Is realized. The braking force control device of the present embodiment is characterized in that it controls the braking force of each wheel to give an ideal braking force distribution ratio to the front and rear wheels without using LSPV or the like.

FIG. 17 shows (Ff, Fr) coordinates for explaining the control characteristics realized by the control device of this embodiment. In the figure, the same diagram as the diagram shown in FIG. 16 is given the same reference numeral, and the description thereof is omitted. As described above, in order to lock the wheels during the braking operation, the front braking force Ff and the rear braking force Fr are
It occurs when a relationship that coincides with a point on the front lock limit line or the rear lock limit line is satisfied. In other words, until these relationships are satisfied, Ff and Fr
However, no matter what process changes, the wheels will not lock.

As described above, if the brake hydraulic pressure guided to the rear wheel wheel cylinder is equal to the brake hydraulic pressure constantly guided to the front wheel wheel cylinder, the rear wheel locks due to the load movement occurring during the braking operation. It becomes easy to do. However, in a region where the rear wheels do not shift to the locked state, it is possible to supply high brake hydraulic pressure to the wheel cylinders of the rear wheels. Further, in order to enhance the braking ability of the vehicle, that is, to obtain a large braking force with respect to the unit brake pedal force, it is appropriate to supply a high brake hydraulic pressure to the wheel cylinders of the rear wheels. From this point of view, in the region where the rear wheels do not shift to the lock state, the brake oil pressure supplied to the wheel cylinders of the rear wheels is not greatly reduced compared to the brake oil pressure supplied to the wheel cylinders of the front wheels. Is desirable.

Therefore, in the present embodiment, V _Wr = _KK between the wheel speed V _Wr of the rear wheels and the wheel speed V _{Wf of the} front wheels.
A control curve _{satisfying the} relationship of V _Wf (K <1) is set, and the braking force of each wheel is controlled so that the control characteristic does not greatly exceed the control curve. When such control is executed and the control characteristics shown in FIG. 17 are realized, a slip ratio equal to or higher than the slip ratio of the front wheels is always applied to the rear wheels, and the braking ability of the rear wheels is effectively made. It can be utilized.

FIG. 18 shows a flow chart of an example of a control routine executed by the antilock braking force control circuit 60 to realize the above function. When the routine shown in FIG. 18 is started, first in S190, the wheel speed sensor 63
The wheel speed of each wheel detected by ~ 66 is read.

Next, in S191, the acceleration sensor 6
The lateral acceleration Gy detected by 2 is read. When
As shown in the above formula (12), the wheel speed of the turning inner wheel
Degree V _WI, The wheel speed of the turning outer wheel V_WO, And lateral acceleration Gy
Is "V_WO ²-V_WI ²= 2d · Gy ”(d;
Red) is established. This relationship is
When the lip ratio is not large, that is, the vehicle is in the braking state
If not, it holds with high accuracy. Therefore, lateral
Acceleration Gy does not necessarily need to be measured and is not applied during braking.
Detected by V_WO, And V_WI ²To “Gy = (V_WO ²−
V_WI ²) / 2d "estimated by substituting into the arithmetic expression
It is also possible to do so.

After the above processing is completed, it is then determined in S192 whether or not the brake switch 67 is in the on state. As a result, when it is determined that the brake switch 67 is not in the ON state, it is determined that the vehicle is not in the braking state and the routine of this time is ended. on the other hand,
When it is determined that the brake switch 67 is in the on state, the absolute value of the lateral acceleration Gy | Gy in S193.
It is determined whether or not | is smaller than a predetermined threshold value α.

When it is determined in S193 that | Gy | <α is established, it is determined that the vehicle is in a straight traveling state, and thereafter, the processing of S194 and thereafter is executed. S1
At 94, the target wheel speeds V _Wrr ^* _, V of the left and right rear wheels are substituted by substituting the wheel speeds V _Wfr, V _Wfl of the left and right front wheels into the following equation.
_Wrl ^* is calculated.

V _Wrr ^* = K · V _Wfr ... (28) V _Wrl ^* = K · V _Wfl ... (29) The constant K used in the above equations (28) and (29).
Is a value smaller than 1, for example, 0.95 to 0.9
9 is used. According to this calculation, the wheel speeds slightly smaller than the wheel speeds V _Wfr, V _Wfl of the left and right front wheels are calculated as the target wheel speeds V _Wrr ^* _, V _Wrl ^* of the left and right rear wheels.

When the calculation of the target wheel speeds V _Wrr ^* _, V _Wrl ^* is completed, next, in S195, the wheel speeds V _Wrr, V _Wrl of the left and right rear wheels are respectively set to the target wheel speeds V _Wrr ^* _,
It is determined whether or not it is smaller than V _{Wr l} ^* . As a result, V
_{Both Wrr} <V _Wrr ^* and V _{Wr l} <V _Wrl ^* are not established, that is, the wheel speeds V _Wrr, V of the left and right rear wheels.
_Wrl are both those target wheel speeds V _Wrr ^* _, V _Wrl ^*
When it is determined that the above is the case, it is determined that it is not necessary to reduce the braking force of the left and right rear wheels, and the current routine is ended without performing the braking force distribution control. in this case,
Brake hydraulic pressure equivalent to that of the front wheel cylinder is introduced into the rear wheel cylinder.

On the other hand, V _Wrr <V _Wrr ^* and V _Wrl <
If at least one of V _Wrl ^* is satisfied, that is,
At least one of the wheel speeds V _{Wrr and} V _Wrl of the left and right rear wheels is
When it is determined that the target wheel speeds V _Wrr ^* _and V _Wrl ^* are smaller than the target wheel speeds, the braking force distribution control is started in S196. In this case, in S197, V _{Wr r}
= V _Wrr ^* and V _Wrl = V _Wrl ^* are both established, the braking force of the left and right rear wheels is controlled.

When the braking force distribution control is started as described above, thereafter, the brake hydraulic pressure of the wheel cylinders of the rear wheels becomes lower than the brake hydraulic pressure of the wheel cylinders of the front wheels. When the above-described braking force distribution control is executed after the vehicle shifts to the braking state, the wheel speed V of the rear wheels is moved by the load movement.
_Although the wheel speeds _{Vfr and VWfl} are _likely to decrease, the rear wheel speeds _{VWrr and VWrl} are properly set to the target wheel speeds _VWrr ^* _{and VWrl} ^* , that is, the front wheel speed V.
It is maintained at a predetermined wheel speed which is slightly smaller than _Wfr, V _Wfl . According to such processing, the braking ability of the rear wheels can be effectively utilized when the braking operation is performed in the straight traveling state.

Next, the case where it is determined in S193 that | Gy | <α is not satisfied will be described. When such a determination is made, it is determined that the vehicle is in a turning state, and then the processing of S198 is executed. The acceleration sensor 62 used in the system of the present embodiment produces a positive output when the vehicle is turning clockwise, while
It produces a negative output when the vehicle is turning counterclockwise. In S198, a process of determining the sign of the lateral acceleration Gy detected based on the output of the acceleration sensor 62 is executed to identify the turning direction of the vehicle.

If it is determined in S198 that Gy ≧ α is satisfied, it is determined that the vehicle is turning clockwise, and first, in S199, the front and rear left wheels are determined as turning outer wheels. Next, in S200, the wheel speed V _{Wfl of the} front inner wheel, that is, the right front wheel is calculated based on the wheel outer speed of the front wheel, that is, the wheel speed V _Wfr of the left front wheel.

Similar to the system of the second embodiment described above, the system of the present embodiment makes the front wheels such that the slip ratios of the front inner wheel and the outer outer wheel become equal when the vehicle is in the braking state. It has a function to control the braking force of. At this time, the wheel speed of the front turning inner wheel is (1)
Target wheel speed V _WI ^* = √ (V _WO ²
-2d · Gy). Therefore, the above-mentioned S2
At 00, the wheel speed V _{Wfr of the} right front wheel is calculated according to the following equation.

V _Wfr = √ (V _Wfl ² −2d · Gy) (30) After the operation of S200 is completed, the above-described S194 is performed.
After the subsequent processing is executed, this routine is ended. In this case, the wheel speed V _Wrr of the right rear wheel, which is the inner turning wheel of the rear wheel, is controlled to the target wheel speed V _Wrr ^* shown in the following equation.

V _Wrr ^* = K · √ (V _Wfl ² −2d · Gy) (31) On the other hand, when it is determined in S198 that Gy ≧ α is not satisfied, the vehicle is rotated counterclockwise. It is judged that the vehicle is turning in the direction. In this case, first, in S201, the front and rear right wheels are determined as the turning outer wheels. Next, in S202, the wheel speed V of the front outer wheel, that is, the right front wheel.
The wheel speed V _{Wfr of the} front inner wheel, that is, the left front wheel is calculated based on _Wfl . At this time, the wheel speed V _Wfr of the left front wheel is calculated by the following equation using the relation of the equation (11).

V _Wfl = √ (V _Wfr ² −2d · Gy) (32) After the operation of S202 is completed, the above-described S194 is performed.
After the subsequent processing is executed, this routine is ended. In this case, the wheel speed V _Wrl of the left rear wheel, which is the inner turning wheel of the rear wheel, is controlled to the target wheel speed V _Wrl ^* expressed by the following equation.

V _Wrl ^* = K · √ (V _Wfr ² −2d · Gy) (33) According to the above processing, when the braking operation is performed during the turning, the turning outer wheel and the turning of the front wheel are performed. The inner wheel can be controlled to the same slip state, and the turning outer wheel and the turning inner wheel of the rear wheel can be controlled to the same slip state, respectively, and can be controlled to be slightly smaller than the slip ratio of the front wheel with respect to the rear wheel. It is possible to give a large slip ratio to. When such braking force distribution is performed, the braking performance of the rear wheels can be effectively utilized while maintaining stable turning behavior of the vehicle.

As described above, according to the system of this embodiment, the braking ability of the rear wheels can be effectively utilized in the straight traveling braking state and the turning braking state. Therefore,
According to the system of the present embodiment, a high braking force can be generated with respect to the unit brake pedal force, and a high braking ability can be realized in the vehicle.

In the above embodiment, the anti-lock braking force control circuit 60 executes the process of S194 to implement the first target wheel speed setting means of the tenth aspect. . Next, with reference to FIG. 19 and FIG. 20 together with FIG. 18, a braking force control device according to an eleventh embodiment of the present invention will be described. The braking force control device of the present embodiment is an embodiment obtained by improving the braking force control device of the tenth embodiment described above.

As described above, in the limit region where the wheels are shifted to the locked state by the braking operation, when the front wheels are shifted to the locked state before the rear wheels, the rear wheels are shifted to the locked state before the front wheels. The vehicle behavior can be maintained more stable than the above. On the other hand, as in the tenth embodiment, if the target wheel speeds V _Wrr ^* _, V _Wrl ^* of the rear wheels are set to be slightly smaller than the wheel speeds V _Wfr, V _Wfl of the front wheels, This causes a situation in which the rear wheels are locked before the front wheels. In this respect, the braking force control device of the tenth embodiment is
Although effective in utilizing the braking force of the rear wheels, it still has a problem in terms of stabilizing the vehicle behavior in the limit region.

The braking force control device of the tenth embodiment has
The problem is that the rear wheels are not likely to be locked.
In the range, the target wheel speed V of the rear wheels_Wrr ^* _,V_Wrl ^*Before
Wheel speed V of the wheel_Wfr,V_WflSet slightly smaller than
And there is a risk that the rear wheels may shift to the locked state.
In the range, the target wheel speed V of the rear wheels_Wrr ^* _,V_Wrl ^*Before
Wheel speed V of the wheel_Wfr,V_WflTo a slightly larger value than
It can be solved by replacing. In this example
The braking force control device uses the target wheel speed V_Wrr ^* _,V
_Wrl ^*It is characterized in that the switching is performed.

FIG. 19 shows an example of the control device of this embodiment.
(Ff, Fr) locus for explaining the control characteristics that appear
Indicates the mark. In addition, in the figure, the diagram shown in FIG.
For the same line drawing as the
Is omitted. The curve shown in FIG. 19 is the wheel speed of the rear wheels.
V_WrAnd the wheel speed V of the front wheels_WfBetween V_Wr= K₂・ V_Wf;
(K₂> (1) to establish the relationship (Ff, Fr)
It is a mark. The curve is drawn below the ideal braking force distribution line
Since it is a curved line, it intersects with the front lock limit line.
It Therefore, the rear wheel speed V_WrAnd the wheel speed V of the front wheels
_WfAnd V_Wr= K₂・ V_Wf; (K₂> 1) satisfy the relationship
If the braking force of the front and rear wheels is controlled as
Can occur on the front wheels before the rear wheels.
Wear.

Therefore, in this embodiment, as shown by the mark in FIG. 19, in the region where there is no possibility that the wheels will be locked, first, the wheel cylinders for the front wheels and the wheel cylinders for the rear wheels are equivalent. (Ff, Fr) is linearly changed by supplying the brake hydraulic pressure of V _wr = K _W between the rear wheel speed V _Wr and the front wheel speed V _Wf.
1 · V _Wf ; (K ₁ <1) so that the relationship (F
f, Fr) along a curve, and further, in the region where the wheel may be locked, the wheel speed V of the rear wheel is changed.
_{Between Wr} and the wheel speed V _Wf of the front wheels, V _Wr = K ₂ · V _Wf ;
So that the relationship of (K ₂ > 1) holds (Ff, Fr)
Is to be changed along a curve.

FIG. 20 is a flow chart showing an example of a subroutine executed by the antilock braking force control circuit 60 to realize the above function. In the present embodiment, the antilock braking force control circuit 60 executes the subroutine shown in FIG. 20 after executing the subroutine shown in FIG. 20 when it is determined in S192 that the brake switch is in the ON state in the routine shown in FIG. The processing from S193 onward shown in FIG.

When the subroutine shown in FIG. 20 is started, first in S210, the average value of the slip ratios of the left and right front wheels (hereinafter referred to as the front wheel slip ratio) Sf is calculated. The slip ratio Sfr of the right front wheel and the slip ratio Sfl of the left front wheel are respectively calculated as follows using the vehicle body speed V _B detected by the vehicle speed sensor 61 and the wheel speeds V _Wfr, V _Wfl of the left and right front wheels. It

[0182] _{Sfr = (V B -V Wfr)} / V B ··· (34) Sfl = (V B -V Wfl) / V B ··· (35) Further, the front wheel slip ratio Sf, these Sfr and Sf
By averaging l, the following equation is calculated.

Sf = (Sfr + Sfl) / 2 (36) The wheel lock occurs when the slip ratio exceeds a predetermined limit slip ratio determined by the tire capacity and the like. Therefore, in a region where the front wheel slip ratio Sf is sufficiently small, it can be determined that there is no possibility that the wheels will shift to the locked state. Then, it can be determined that the larger the front wheel slip ratio Sf, the greater the possibility that the wheels will shift to the locked state.

In this routine, in step S210,
After the wheel slip ratio Sf is calculated, the front wheel slip is calculated in S211.
The lip ratio Sf is a predetermined threshold value S₀Or not
Is determined. As a result, Sf> S₀Is not established
If there is a possibility that the wheels will not be locked,
Then, in S212, K to K₁After (<1) is substituted,
This routine ends. On the other hand, Sf> S₀Is established
If so, the wheels move to the locked state.
It is judged that there is a possibility, and K is transferred to K in S213. ₂(>
After 1) is substituted, the routine of this time is ended.

Thereafter, using K set as described above,
The processing after S193 shown in FIG. 18 is executed. According to this process, the braking ability of the rear wheels is effectively utilized in the area where the rear wheels are unlikely to be locked, and when the wheels are locked, the front wheels are always prior to the rear wheels. A lock can be generated. Therefore, according to the braking force control device of the present embodiment, it is possible to solve the problem of the tenth embodiment and obtain stable vehicle behavior in the vicinity of the limit region in the braking state.

In the above embodiment, the anti-lock braking force control circuit 60 executes the process of S210 so that the slip ratio detecting means according to the eleventh aspect of the present invention causes the slip ratio detecting means K = K set in S213. The above S using K ₂
By executing the processing of 194, the second target wheel speed setting means according to claim 11 again executes the above S211.
The target wheel speed switching means according to the eleventh aspect is realized by executing the processing of.

By the way, in the eleventh embodiment described above, it is decided whether or not the wheels are likely to shift to the locked state based on the front wheel slip ratio Sf.
The present invention is not limited to this, and the same determination may be performed based on the slip ratio of the rear wheels.

Next, a twelfth embodiment of the present invention will be described with reference to FIGS. The braking force control device of this embodiment can be realized by using the system configuration shown in FIG. In the first to fifth examples and the like described above, together with the target wheel speed V _WI ^* is calculated turning inner based on the wheel speed V _WO turning outer, turning inner wheel speed V _WI is a target wheel speed V _WI By controlling the braking force so that it coincides with ^* , the braking force distribution control for the turning outer wheel and the turning inner wheel is realized.

When the vehicle is traveling on a paved road, the wheel speed V _WO of the turning outer wheel is stable. Therefore, if the braking force distribution control is executed as described above, the slip ratio of the turning inner wheel becomes The slip ratio of the outer turning wheel can be accurately matched. However, in a situation where the wheel speed is high frequency and greatly changes, for example, when the vehicle is traveling on a rough road, the wheel speed V _WO of the turning outer wheel fluctuates due to the fluctuation of the wheel speed V _WO of the turning inner wheel. The deviation between _WI and its target wheel speed V _WI ^* may vary greatly.

FIG. 21 shows that the vehicle is running on a rough road.
Target wheel speed V of the calculated turning inner wheel_WI ^*And such a state
Wheel speed V of the turning inner wheel measured under actual conditions_WIDeviation from
= V _WI-V_WI ^*Shows the temporal variation of. As shown in FIG.
In a situation where the deviation ΔV changes drastically at high frequencies,
By executing the braking force distribution control, the slip of the turning inner wheel can be reduced.
It is difficult to match the slip ratio of the turning outer wheel with the slip ratio of the turning outer wheel
Is. Also, in such a situation, the braking force distribution control will continue.
Control causes hunting, which causes braking of the inner wheel during turning.
There can occur situations where forces are improperly controlled. Because of this,
Under such a circumstance, without executing the braking force distribution control,
It is appropriate to generate normal braking force on the turning inner wheel.
It

The braking force control system of the present embodiment has a predetermined time T
_{During the} period ₁ , the number of times that ΔV has changed significantly is counted. If a large number of changes have occurred over a predetermined number of times, it is determined that the wheel speed is unstable, and the braking force distribution control is executed. The feature is that it has a prohibition function.

FIG. 22 is a flow chart showing an example of a control routine executed by the antilock braking force control circuit 60 to realize the above function. In FIG. 22, the same steps as those shown in FIG. 18 are given the same reference numerals in parentheses to simplify the description.

When the routine shown in FIG. 22 is started, first in S220, the wheel speed of each wheel is read. Next, in S221, the lateral acceleration Gy acting on the vehicle is read. Then, in S222,
It is determined whether or not the brake switch 67 is on.

If it is determined in S222 that the brake switch 67 is in the on state, then in S223, determination of the turning inner and outer wheels is performed. As described above, the acceleration sensor 62 outputs different positive and negative signals depending on the turning direction of the vehicle. In this step S223, the turning inner and outer wheels are determined based on the sign of Gy.

At S224, the target wheel speed V of the turning inner wheel is set.
_WI ^*Is calculated. In Step 224, the above-mentioned
As in the case of the second embodiment, the turning outer wheel is added to the above formula (11).
Wheel speed V_WOSubstituting the lateral acceleration Gy
Then, the target wheel speed V of the turning inner wheel _WI ^*Is calculated.

Next, in S225, the deviation ΔV = V _WI − between the wheel speed V _WI of the turning inner wheel and its target wheel speed V _WI ^*.
V _WI ^* is calculated. Further, in S226, it is determined whether or not the number of times ΔV has changed from the state of being equal to or less than the predetermined value K to the state of exceeding the predetermined value K within the time of the past T ₁ is N ₁ or more. During execution of the braking force distribution control, ΔV = V _WI −
The braking force of the turning inner wheel is controlled so that V _WI ^* approaches "0". Therefore, the target wheel speed V _WI ^* is frequent and
As long as it does not change significantly, ΔV does not increase or decrease significantly. When the stable target wheel speed V _WI ^* is obtained, the threshold value K and the predetermined time T ₁ are S2.
26 is not satisfied and the target wheel speed V _WI ^*
Is a value that is experimentally set in advance so that the condition of S226 is satisfied in the case where F fluctuates unduly.

Therefore, when the condition of S226 is satisfied, it can be determined that the braking force distribution control should be prohibited. In this case, S227 is followed by S227
After the braking force distribution control is prohibited in, the routine of this time is ended. On the other hand, when the condition of S226 is not satisfied, it can be determined that the execution of the braking force distribution control should be permitted. In this case, it is determined in S228 whether or not the start condition of the braking force distribution control is satisfied, that is, whether or not ΔV <0 is satisfied.

As a result, ΔV <0 is not established, that is, the wheel speed V _WI of the turning inner wheel is equal to the target wheel speed V _WI.
^When it is determined that it is larger than ^* , it is determined that it is not necessary to control the braking force of the turning inner wheel, and the routine of this time is ended. On the other hand, ΔV <0 holds, that is, the wheel speed V _WI of the turning inner wheel is the target wheel speed V _WI ^*.
If it is determined that it is smaller than, braking force distribution control is started in S229.

In the braking force distribution control, when the vehicle is in the turning braking state, the brake hydraulic pressure supplied to the wheel cylinder on the turning inner wheel side is set to be lower than the brake hydraulic pressure supplied to the turning outer wheel side. It is realized by doing.
Such a brake oil pressure deviation is after the braking operation is started,
This is realized by maintaining the brake path communicating with the wheel cylinder on the outer wheel side of the turning in the pressure increasing mode, and switching the brake path communicating with the wheel cylinder on the inner wheel side of the turning into the holding mode, the pressure increasing mode, and the pressure reducing mode.
At this time, the control of the brake path corresponding to the turning inner wheel is executed so as to gently increase the brake pressure of the wheel cylinder on the turning inner wheel side compared to the brake pressure of the wheel cylinder on the turning outer wheel side. Such a function can be realized by repeating the holding mode and the pressure increasing mode except for a special case. That is, the depressurization mode is executed in the brake route corresponding to the turning inner wheel only when the target wheel speed V _WI ^{* that} is significantly larger than the wheel speed V _WI of the turning inner wheel is set. Therefore, if the pressure reduction mode is frequently executed after the execution of the braking force distribution control is started, the target wheel speed V _WI ^* is significantly changed.
That is, it can be determined that the wheel speed is inappropriately fluctuating.

FIG. 23 is a time chart showing the operating state when the braking force distribution control is started under the condition where the wheel speed is unstable. As shown in FIG. 23 (A), when the braking force distribution control is started at time t ₁ , if the wheel speed is unstable, then as shown in FIG. 23 (B), the pressure increasing mode, and The depressurization mode is frequently executed together with the holding mode. At this time, as shown in FIG. 23C, by counting the number of depressurization modes executed within a predetermined time, it is possible to determine whether or not a stable wheel speed is obtained based on the counted value. it can.

Therefore, in this embodiment, after the execution of the braking force distribution control is started in S229, the number of times the depressurization mode is executed in the past predetermined time T ₂ is the predetermined number N ₂ or more in S230. Is determined. As a result, the number of depressurization modes executed within the time T ₂ is N ₂
When it is determined that the wheel speed is less than the number of times, it is determined that the wheel speed is normally detected, and thereafter, the braking force distribution control is continued in S231, and then this routine is ended. On the other hand, when it is determined that the number of the pressure reducing modes executed within the time T ₂ is N ₂ or more, it is determined that the proper wheel speed is not detected, and thereafter, the determination is made in S232 or more, After the braking force distribution control is ended in S233, the routine of this time is ended.

As described above, according to the braking force control device of the present embodiment, the execution of the braking force distribution control can be surely prohibited under the situation where the wheel speed becomes unstable. Therefore,
According to the braking force control device of this embodiment, when driving on a rough road,
It is possible to avoid the inconvenience that the braking force of the turning inner wheel is improperly controlled.

In the above embodiment, the anti-lock braking force control circuit 60 executes the processing of S226 or S230 so that the wheel speed instability detection means according to claim 12 also operates. By executing the processing of S223, the braking force control prohibiting means according to claim 12 is realized.

By the way, in the above-described embodiment, the predetermined time T
The instability of the wheel speed is detected based on the number of changes in ΔV occurring within ₁ and the number of pressure reduction modes executed within the predetermined time T ₂ , but these are not necessarily used in combination. It is not necessary to detect the instability of the wheel speed based on only one of them.

Further, in the above-described embodiment, when the fluctuation range of ΔV is large, it is determined that the instability of the wheel speed is high, but the present invention is not limited to this, and the wheel is not limited to this. The same determination may be made based on the speed variation itself. Furthermore, in the above-described embodiment, the degree of instability of the wheel speed is determined based on the number of times the pressure reduction mode is executed, but the present invention is not limited to this, and the pressure reduction mode is executed. The determination may be made based on the accumulated time.

Next, a thirteenth embodiment of the present invention will be described with reference to FIGS. 24 to 27. In the braking force control system of the present embodiment, a steering angle sensor for detecting the steering angle δ of the steering wheel and a yaw rate sensor for detecting the yaw rate γ of the vehicle are connected to the antilock braking force control circuit 60 shown in FIG. It can be realized by doing.

When the slip ratio of the turning inner wheel and the slip ratio of the turning outer wheel are controlled to be equal by the braking force distribution control,
The braking force generated by the turning inner wheel is reduced as compared to the case where such control is not executed. The braking force generated in the turning inner wheel acts on the vehicle as a turning moment that rotates the vehicle in the turning direction. Therefore, as the braking force generated by the turning inner wheel increases, the steering characteristic of the vehicle tends to oversteer, while as the braking force generated by the turning inner wheel decreases, the steering characteristic of the vehicle tends to understeer.

Therefore, when the oversteer tendency appears while the vehicle is turning, if the braking force distribution control is executed, the oversteer tendency is canceled and a steering characteristic close to the neutral steer can be obtained. .
On the other hand, when the understeer tendency appears while the vehicle is turning, if the braking force distribution control is executed, the understeer tendency is promoted, and the vehicle becomes even more difficult to turn. Therefore, it is appropriate not to execute the braking force distribution control when the understeer characteristic appears during turning.

Whether or not the steering characteristic of the vehicle during turning is the understeer characteristic is as described below, the magnitude relationship between the actual yaw rate γ and the ideal yaw rate γ ^* , and the actual lateral acceleration Gy and the ideal lateral acceleration Gy ^* . It can be judged based on the size relationship. Where the ideal yaw rate γ
^* Is a yaw rate γ obtained when the vehicle exhibits a neutral steer characteristic, and can be obtained by a known method based on the vehicle body speed and the steering angle δ. Similarly,
The ideal lateral acceleration Gy ^* is the lateral acceleration Gy obtained when the vehicle exhibits a neutral steer characteristic, and can be obtained by a known method based on the vehicle body speed and the steering angle δ.

In FIG. 24, it is determined whether or not the steering characteristic is the understeer characteristic based on the magnitude relationship between the yaw rate γ and the ideal yaw rate γ ^* and the magnitude relationship between the actual lateral acceleration Gy and the ideal lateral acceleration Gy ^*. The figure for demonstrating an example of a method is shown. Characteristic value C ₁ = γ · shown in FIG.
(Γ ^* −γ) is the ideal yaw rate γ ^* and the actual yaw rate γ.
This is a characteristic value obtained by multiplying the deviation between and by the actual yaw rate γ. In the present embodiment, the yaw rate sensor outputs positive and negative signals corresponding to the turning direction. Similarly,
The ideal yaw rate γ ^* is given a different sign corresponding to the turning direction, that is, the direction of the steering angle δ.
On the other hand, the sign of the characteristic value C ₁ does not change depending on the turning direction of the vehicle, and is positive when the actual yaw rate γ is insufficient with respect to the ideal yaw rate γ ^* , and also the ideal yaw rate γ ^* . On the other hand, when the actual yaw rate γ is excessive, it becomes negative.

Further, the characteristic value C ₂ = Gy · shown in FIG.
(Gy ^* -Gy) is a characteristic value obtained by multiplying the deviation between the ideal lateral acceleration Gy ^* and the actual lateral acceleration Gy by the actual lateral acceleration Gy. In this embodiment, the acceleration sensor 62 is
It outputs different positive and negative signals corresponding to the turning direction. Similarly, the ideal lateral acceleration Gy ^* is given a different sign corresponding to the turning direction, that is, corresponding to the direction of the steering angle δ. On the other hand, the sign of the characteristic value C ₂ does not change depending on the turning direction of the vehicle, and is positive when the actual lateral acceleration Gy is insufficient with respect to the ideal lateral acceleration Gy ^* . It becomes negative when the actual lateral acceleration Gy is excessive with respect to Gy ^* .

As described above, the signs of the characteristic values C ₁ and C ₂ represent the turning characteristic of the vehicle and the lateral grip state, respectively. The area 1 shown in FIG. 24 is C ₁ <
It is a region where 0 and C ₂ <0 are satisfied. This condition is satisfied when the vehicle exhibits an oversteer tendency while securing a sufficient corner rigging force. Therefore, the region 1 can be recognized as a region in which the vehicle tends to oversteer, as shown in FIG.

Region 2 shown in FIG. 24 is a region where C ₁ <0 and C ₂ > 0. Such a condition is satisfied when the vehicle exhibits an oversteer tendency in a state where the cornering force is insufficient. Therefore, the area 2 is shown in FIG.
As shown in FIG. 5, it can be recognized as a region where the vehicle shows a spin tendency.

A region 3 shown in FIG. 24 is a region where C ₁ > 0 and C ₂ > 0. This condition is satisfied when the vehicle exhibits an understeer tendency in the state where the cornering force is insufficient. Therefore, the region 3 is shown in FIG.
As shown in FIG. 5, it can be recognized as an area where the vehicle tends to understeer and drift out.

[0215] Furthermore, the area 4 shown in FIG. 24, C _1>
It is a region where 0 and C ₂ > 0 are satisfied. This condition is satisfied when the vehicle exhibits an understeer tendency while securing a sufficient cornering force. Therefore,
As shown in FIG. 25, the area 4 can be recognized as an area formed when the vehicle laterally moves due to disturbance or the like.

As described above, the actual yaw rate γ, the ideal yaw rate γ ^* , the actual lateral acceleration Gy, and the ideal lateral acceleration Gy ^*.
Then, by comparing the magnitude relationships between them, the state of the vehicle at the time of turning can be accurately detected. The braking force control apparatus according to the present embodiment determines whether or not the vehicle has the understeer tendency by such a method, and when the understeer tendency appears, the execution of the braking force distribution control that promotes the tendency is stopped. It is characterized by points.

FIG. 26 is a flow chart showing an example of a control routine executed by the antilock braking force control circuit 60 so as to realize the above function. When the routine shown in FIG. 26 is started, first, in S240, the wheel speed of each wheel, the steering angle δ, the lateral acceleration Gy, and the yaw rate γ are read.

Next, at S241, it is judged if the braking force distribution control is being executed. If the braking force distribution control is not executed, there is no advantage in advancing the subsequent processing, and thus this routine is immediately ended. On the other hand, if it is determined that the braking force distribution control is being executed, S2
At 42, it is determined whether or not an understeer tendency appears by the above method.

As a result, if it is determined that the understeer tendency does not appear, it is determined that there is no harmful effect even if the braking force distribution control is continued, and then this routine is ended. On the other hand, if it is determined that the turning behavior exhibits the understeer tendency, the braking force distribution control is ended in S243. When the braking force distribution control is completed, the brake hydraulic pressure supplied to the wheel cylinders of the turning inner wheel then increases, and the braking force generated by the turning inner wheel increases. Therefore, the turning moment acting on the vehicle increases,
Understeer tendency is suppressed.

As described above, according to the braking force control apparatus of the present embodiment, when an understeer tendency occurs during turning, the execution of the braking force distribution control that promotes the tendency can be stopped. Therefore, according to the braking force control apparatus of the present embodiment, the turning characteristics of the vehicle are not impaired by the execution of the braking force distribution control, and excellent maneuverability can be realized.

By the way, during execution of the braking force distribution control, the brake oil pressure in the wheel cylinder on the turning inner wheel side is supplied from the master cylinder in accordance with the brake oil pressure in the wheel cylinder on the turning outer wheel side, that is, the brake pedal force. The pressure is suppressed to a low pressure compared to the master cylinder pressure. Therefore,
When the wheel cylinder on the turning inner wheel side is connected to the master cylinder after the braking force distribution control is stopped, the brake hydraulic pressure on the turning inner wheel side suddenly increases. In order to maintain stable vehicle behavior during turning, it is preferable to suppress such a sudden increase in brake hydraulic pressure.

Therefore, in the present embodiment, the above S2
If the braking force distribution control is ended in step 43, then, in step S244, the pressure increase hydraulic pressure switching valve that communicates with the wheel cylinder on the turning inner wheel side is duty-controlled for a predetermined time T _1, and then this routine is ended. To be done.

FIG. 27 shows changes in the brake oil pressure P _WI on the turning inner wheel side, which is realized by the braking force control system of the present embodiment.
And changes in the brake hydraulic pressure P _WO on the turning outer wheel side. still,
The change of the brake oil pressures P _WI and P _WO shown in FIG.
_This is realized when the braking operation is started at ₀ , the braking force distribution control is started at time t ₁ , and then the braking force distribution control is ended at time t ₂ .

During the period from time t ₀ to time t ₁ , the braking force distribution control is not executed, so the brake oil pressure P _WI on the turning inner wheel side is increased in the same manner as the brake oil pressure P _WO on the turning outer wheel side. When the braking force distribution control is started at time t ₁ , thereafter, the brake hydraulic pressure P _WO on the turning outer wheel side rises similarly to the master cylinder pressure P _MC , while the brake hydraulic pressure P _WI on the turning inner wheel side changes in stages. Shows a moderate rise. Time t ₂
When the braking force distribution control is completed, the duty control of the pressure increasing hydraulic pressure switching valve is started,
Brake oil pressure P _WI on the turning inner wheel side is master cylinder pressure P _MC
Gradually rises toward.

According to such processing, it is possible to suppress the understeer tendency of the vehicle by ending the braking force distribution control, and it is possible to suppress the behavior change which occurs in the vehicle when the control is ended. The vehicle behavior can always be stably maintained during turning braking.

In the above embodiment, the anti-lock braking force control circuit 60 executes the processing of S242, whereby the steering characteristic detecting means according to claim 14 executes the processing of S243. By doing so, the second braking force control canceling means according to claim 14 is realized.

Next, a fourteenth embodiment of the present invention will be described with reference to FIGS. 28 and 29. The braking force control device of the present embodiment detects the steering angle δ of the steering wheel with the same configuration as the system configuration of the thirteenth embodiment described above, that is, in the antilock braking force control circuit 60 shown in FIG. This can be realized by connecting the steering angle sensor and the yaw rate sensor that detects the yaw rate γ of the vehicle.

The braking force control system of this embodiment is characterized in that the understeer tendency can be suppressed more efficiently than in the thirteenth embodiment described above. This effect is realized by the antilock braking force control circuit 60 executing the routine shown in FIG. 28 instead of the routine shown in FIG. 28, the steps in which the same processing as the steps shown in FIG.
The same reference numerals are given and the description thereof is omitted.

According to the routine shown in FIG. 28, an understeer tendency appears in the vehicle, and after the braking force distribution control is ended in S243, the brake hydraulic pressure on the inside wheel turning side is duty controlled for a predetermined time T ₁ in S250. At the same time, after the brake hydraulic pressure on the outer wheel turning side is maintained, a series of processes is ended.

FIG. 29 shows the case where such processing is executed.
Brake oil pressure P on the inner wheel side of the turning that is realized_WIChange, and
Brake oil pressure P on the turning outer wheel side_WOShows the change of. Incidentally, FIG.
Brake oil pressure P shown in 9_WI, P_WOChanges at time t₀To
Braking operation is started and time t ₁Braking force distribution control started
And then time t₂Braking force distribution control has been completed
Will be realized in case.

Brake oil pressure P on the turning inner wheel side_WI, And
Brake oil pressure P on the supination wheel side_WOAt time t₁~ T₂Period of
The inside is boosted in the same manner as in the case of the 13th embodiment described above.
It Time t₂When the braking force distribution control is completed,
After that, the brake oil pressure P on the turning inner wheel side _WIIs duty boosted
And the master cylinder pressure P_MCIs boosted
Despite this, the brake hydraulic pressure P on the turning outer wheel side_WOAt time t
₂The oil pressure is maintained as it is.

The braking force generated by the turning outer wheel acts on the vehicle as a moment in a direction that hinders the turning of the vehicle, that is, as a moment in a direction that promotes an understeer tendency. Therefore, the brake hydraulic pressure P on the outer wheel turning side
_{When WO} is held after time t ₂ , for a predetermined time T ₁ ,
It is possible to suppress the growth of the moment that tends to promote the understeer tendency. For this reason, according to the braking force control device of the present embodiment, the understeer tendency can be effectively suppressed after the braking force distribution control is ended, together with the increase of the braking force of the turning inner wheel.

Next, a fifteenth embodiment of the present invention will be described with reference to FIGS. 30 and 31. The braking force control device of the present embodiment can be realized by the same configuration as the system configuration of the 13th and 14th embodiments described above. The braking force control device of the present embodiment is characterized in that it can exhibit excellent continuity in the process of shifting to the normal control after the braking force control is completed, as compared with the above-described fourteenth embodiment. are doing. This function is provided by the antilock braking force control circuit 6
0 is realized by executing the routine shown in FIG. 30 instead of the routine shown in FIG. FIG.
0, the same steps as those shown in FIG. 26 are designated by the same reference numerals and the description thereof will be omitted.

[0234] According to the routine shown in FIG. 30, appearing understeer tendency of the vehicle, after the braking force distribution control is finished in S243, in S251, for a predetermined time T _1, the turning inner wheel side brake hydraulic pressure and, After the brake hydraulic pressure of the turning outer wheel is increased by the duty control, a series of processes is ended.

FIG. 31 shows the case where such processing is executed.
Brake oil pressure P on the inner wheel side of the turning that is realized_WIChange, and
Brake oil pressure P on the turning outer wheel side_WOShows the change of. Incidentally, FIG.
Brake oil pressure P shown in 1_WI, P_WOChanges at time t₀To
Braking operation is started and time t ₁Braking force distribution control started
And then time t₂Braking force distribution control has been completed
Will be realized in case.

Brake oil pressure P on the turning inner wheel side_WI, And
Brake oil pressure P on the supination wheel side_WOAt time t₁~ T₂Period of
The inside is boosted in the same manner as in the case of the 14th embodiment described above.
It Time t₂When the braking force distribution control is completed,
After that, the brake oil pressure P on the turning inner wheel side _WIIs duty boosted
And the brake hydraulic pressure P on the outer side of the turning wheel_WOWell, dew
The pressure is gently increased by increasing the tee pressure.

After a lapse of a predetermined time T ₁ after the braking force distribution control is completed, the brake path is returned to the normal state, and the wheel cylinder on the turning inner wheel side and the wheel cylinder on the turning outer wheel side are both mastered. It becomes conductive with the cylinder. In order to obtain excellent continuity in such a transitional period, both the brake oil pressure on the turning inner wheel side and the brake oil pressure on the turning outer wheel side are brought close to the master cylinder pressure P _MC when the time T ₁ elapses. It is necessary. On the other hand, as in the present embodiment, according to the configuration in which the brake hydraulic pressure on the turning inner wheel side and the brake hydraulic pressure on the turning outer wheel side are both duty-increased, it is possible to effectively understeer after the braking force distribution control is completed. While suppressing the tendency, it is possible to realize excellent continuity before and after the state of the brake path is switched. Therefore, according to the braking force control device of the present embodiment, it is possible to obtain the effect that the discomfort at the end of the braking force distribution control can be reduced, as compared with the fourteenth embodiment.

Next, a sixteenth embodiment of the present invention will be described with reference to FIGS. 32 to 34. The braking force control device of this embodiment can be realized by using the system configuration shown in FIG. The braking force control device of the present embodiment executes the braking force distribution control for making the slip ratio of the turning inner wheel and the slip ratio of the turning outer wheel equal. In the braking force distribution control, the target wheel speed V of the inner turning wheel is determined based on the wheel speed V _{WO of the} outer turning wheel, as in the first to fifth embodiments described above.
Calculates the _WI ^*, and the wheel speed V _WI turning inner is achieved by controlling the braking force of the inner turning wheel to match the target wheel speed V _WI ^*.

FIG. 32 is a time chart for explaining the operation when the brake route is normal. FIG.
(A) shows a change in the execution state of the braking force distribution control. As shown in the figure, in the example of FIG. 32, the braking force distribution control is started at time t ₁ . FIG. 32 (B) shows a change state of the control mode realized by the brake path communicating with the wheel cylinder on the turning inner wheel side after the braking force distribution control is started. When the brake path is normal, an appropriate brake hydraulic pressure is introduced to the wheel cylinder on the outer wheel turning side during execution of the braking force distribution control. In the brake path communicating with the wheel cylinder on the turning inner wheel side, the brake hydraulic pressure on the turning inner wheel side is appropriately increased as shown in FIG. 32 (B) in order to make it an appropriate hydraulic pressure corresponding to the brake pressure on the turning outer wheel side. The pressure mode, the holding mode, and the pressure reduction mode are repeated.

FIG. 33 is a time chart for explaining the operation of the system of this embodiment in the case where a failure has occurred in which the brake hydraulic pressure of the wheel cylinder on the turning outer wheel side cannot be increased. FIG. 33A shows a change in the execution state of the braking force distribution control. As shown in the figure, in the example of FIG. 33, the braking force distribution control is started at time t ₁ .

FIG. 33B shows a change state of the control mode realized in the brake path communicating with the wheel cylinder on the turning inner wheel side after the braking force distribution control is started. When a failure occurs in which the brake hydraulic pressure on the turning outer wheel side cannot be increased in the brake path, the brake hydraulic pressure on the turning outer wheel side is not increased during execution of the braking force distribution control. Therefore, in such a situation, the wheel speed V _WO on the turning outer wheel side is not reduced even if the braking operation is performed. Wheel speed V on the turning outer wheel side
_{If the WO} is not decelerated, the target wheel speed V _WI ^{* of the} turning inner wheel calculated based on the wheel speed V _WO is not also decelerated. On the other hand, if the brake path communicating with the wheel cylinder on the turning inner wheel side is normal, the brake hydraulic pressure is guided to the wheel cylinder on the turning inner wheel side during execution of the braking force distribution control. In this case, in the brake path communicating with the wheel cylinder on the turning inner wheel side, the wheel speed V _WI of the turning inner wheel is made to match the target wheel speed V _WI ^* of FIG. 33 (B).
As shown in, the pressure reduction mode is continuously set after the time t ₁ .

As described above, when the braking force distribution control is executed when the brake path communicating with the wheel cylinder on the outer wheel turning side has failed, the brake path communicating with the wheel cylinder on the inner wheel side turning will be normally operated. Even if there is, it may not be possible to increase the brake hydraulic pressure on the turning inner wheel side. Therefore, when one of the left and right wheel braking devices fails, the other braking device must function effectively.
It is desirable to stop the braking force distribution control when such a failure occurs.

As described above, when there is a failure in which the brake hydraulic pressure cannot be increased in the brake path communicating with the wheel cylinder on the turning outer wheel side, after the braking force distribution control is started, the turning inner wheel side is started. The brake path communicating with the wheel cylinder is continuously set to the pressure reducing mode. on the other hand,
When the braking force distribution control is properly executed, the pressure reduction mode is not continuously executed as described above. Therefore, in the system of the present embodiment, after the braking force distribution control is started, if the pressure reduction mode is continued for the predetermined time T _{1 in} the brake path on the turning inner wheel side, the braking force distribution control is stopped. And

FIG. 34 is a flow chart showing an example of a control routine executed by the antilock braking force control circuit 60 to realize the above function. When the routine shown in FIG. 34 is started, first in S260, it is determined whether or not the braking force distribution control is being executed. If it is determined that the braking force distribution control is not being executed, there is no real benefit of advancing the subsequent processing, so the routine of this time is promptly ended. On the other hand, if it is determined that the braking force distribution control is being executed, then the process of S261 is executed.

In S261, the control mode of the brake path communicating with the wheel cylinder on the turning inner wheel side is monitored. In this step S261, it is detected whether the brake path communicating with the wheel cylinder on the turning inner wheel side is in the pressure increasing mode, the holding mode, or the pressure reducing mode.

Next, at S262, it is judged if the duration t of the pressure reducing mode exceeds the predetermined time T ₁ . As a result, when t> T ₁ is not established, it is determined that the braking force distribution control is normally executed, and S263
After the decision to continue the control is made in, the routine of this time is ended. On the other hand, if it is determined in S262 that t> T ₁ is satisfied, it is determined that the braking force distribution control is not normally executed, an abnormality determination is made in the braking path in S264, and then the braking force distribution is determined in S265. After the control is finished, this routine is finished.

According to the above-mentioned processing, when the brake hydraulic pressure on the outer wheel side of the turning cannot be increased due to a failure in the brake path, the brake hydraulic pressure on the inner wheel side of the turning can be reliably increased. Therefore, according to the braking force control device of the present embodiment, it is possible to provide the function of executing the braking force distribution control and the fail-safe against the failure of the brake path.

By the way, the routine shown in FIG. 34 is immediately terminated after S265 when the abnormality of the brake path is determined. However, after S265, the routine of S244 in FIG.
It is also possible to execute the same processing as the above, that is, control for increasing the duty of the brake hydraulic pressure on the turning inner wheel side.
When such a process is added, it is possible to suppress the behavior change occurring in the vehicle before and after the braking force distribution control is ended, and it is possible to obtain good steering stability.

Incidentally, in the above embodiment, the antilock braking force control circuit 60 uses the above S262, S264, S
By executing the processing of 265, the above-mentioned first braking force control stopping means is realized. Next, a seventeenth embodiment of the present invention will be described with reference to FIGS. The braking force control device according to the present embodiment can be realized by a configuration in which the acceleration sensor 62 is removed from the system configuration shown in FIG.

The curve indicated by the alternate long and short dash line in FIG. 35 is the target wheel of the inner turning wheel for making the slip ratio of the inner turning wheel equal to the slip ratio of the outer turning wheel when the wheel speed of the outer turning wheel is V _WO. The velocity V _WI ^* is shown. The target wheel speed V _WI ^* is V _WI ^* = √ (V
_WO ² -2d · Gy). Therefore, FIG.
As shown in 5, its value decreases as Gy increases.

The solid straight line in FIG. 35 indicates that Gy is a predetermined value K / 2d when the wheel speed of the turning outer wheel is V _WO.
In a region exceeding V, the target wheel speed V of the inner turning wheel for giving a larger slip ratio to the outer turning wheel than the inner turning wheel
Indicates _WI ^* . The target wheel speed V _WI ^* is (1)
As shown in the equation 8), it can be expressed as V _WI ^* = √ (V _WO ² −K). Therefore, as shown in FIG. 35, the value is Gy.
It is constant regardless of the value of.

The target wheel speed V _WI indicated by the curve in FIG.
^{In the} braking force distribution control using ^* , the lateral acceleration Gy is used to calculate the target wheel speed V _WI ^* . Therefore, in order to execute such control, it is necessary to accurately detect the lateral acceleration Gy. On the other hand, in the braking force distribution control using the target wheel speed V _WI ^* shown by a straight line in FIG. 35, the lateral acceleration Gy is not used for calculating the target wheel speed V _WI ^* . Therefore, as in the third embodiment described above, the braking force control device that executes such control can be realized without using the lateral acceleration sensor 62.

In the third embodiment described above, V_WO ²-V_WI ²>
In the region where K is satisfied, the wheel speed of the turning inner wheel is set to V_WI ^*=
√ (V_WO ²-K) so that the braking force distribution control
To execute. The slip ratio of the turning inner wheel and the slip of the turning outer wheel
If the rate is the same, V_WO ²-V_WI ²= 2d · Gy
(11) above is established. Therefore, the
Control start condition “V” of the third embodiment_WO ²-V_WI ²> K ”is
“2d · Gy> K”, that is, “Gy> K / 2d”
Can be approximated. Therefore, in the third embodiment described above
Therefore, in the region where Gy> K / 2d holds, the braking force distribution is
Control will be executed.

When the lateral acceleration Gy acting on the vehicle is K / 2d, the target wheel speed V _WI ^* is changed to V _WI ^*.
= √ (V _WO ² −2d · Gy) or V _WI ^* = √ (V _WO ² −K), the same calculation result can be obtained as shown in FIG. 35. . At this point, the target wheel speed V _WI ^* is V _WI ^* = √ (V _WO ² −K)
The following formula is used to obtain the target wheel speed V _WI for equalizing the slip ratio of the turning inner wheel and the turning outer wheel on the assumption that the lateral acceleration Gy acting on the vehicle is always K / 2d. ^This is the same as calculating ^* (V _WI ^* shown by the curve in FIG. 35).

In order to effectively utilize the grip capability of the inner turning wheel and the grip ability of the outer turning wheel during turning, it is appropriate to make the slip ratios of both wheels uniform.
In the sense of satisfying such a requirement, the lateral acceleration Gy is accurately detected using the acceleration sensor 62, and the target wheel speed V _WI ^* of the turning inner wheel is calculated as V _WI ^* = √ (V _WO ² −2d · Gy) It is preferable to seek according to. Therefore, when the braking force distribution control is executed by the method of the third embodiment, a large deviation is not generated between the slip ratio of the inner turning wheel and the slip ratio of the outer turning wheel during the execution of the braking force distribution control. It is necessary.

As described above, the curve indicated by in FIG.
It is a target wheel speed V _WI ^* of the inner turning wheel for making the slip rate of the inner turning wheel equal to the slip rate of the outer turning wheel. Therefore, if the wheel speed V _WI of the turning inner wheel during braking is higher than the target wheel speed V _WI ^* , the slip ratio of the turning inner wheel is smaller than the slip ratio of the turning outer wheel. It has been suppressed. That is, the region (Gy>) where the braking force distribution control is executed according to the third embodiment.
In the region where K / 2d is satisfied), the slip ratio of the turning inner wheel is always smaller than the slip ratio of the turning outer wheel.

[0257] straight line shown by a one-dot chain line in FIG. 36, V _WI
^{When the} braking force distribution control is executed based on the target wheel speed V _WI ^* calculated by the arithmetic expression ^* = √ (V _WO ² -2d · Gy), the pressure reduction realized by the wheel cylinder on the inner wheel side of turning A straight line schematically showing the control amount is shown. Hereinafter, this straight line is referred to as an ideal pressure reduction control line, and the pressure reduction control amount coordinate value of each point on the straight line is referred to as an ideal pressure reduction control amount.

The straight line shown by the solid line in FIG. 36 is V _WI ^* =
When the braking force distribution control is executed based on the target wheel speed V _WI ^* calculated by the arithmetic expression √ (V _WO ² −K),
A straight line schematically showing the pressure reduction control amount realized by the wheel cylinder on the turning inner wheel side is shown. Hereinafter, this straight line will be referred to as an approximate pressure reduction control line, and the pressure reduction control amount coordinate value of each point on the line will be referred to as an approximate pressure reduction control amount.

As described above, V_WI ^*= √ (V_WO ²-K)
Target wheel speed V obtained from_WI ^*Braking force distribution control using
Is executed, in the area of Gy> K / 2d,
The slip ratio of the wheel is small compared to the slip ratio of the turning outer wheel.
Is done. This situation is V_WI ^*= √ (V_WO ²-2d ・ G
target wheel speed V obtained from y)_WI ^*Braking force distribution using
The inner wheel turns faster than if the minute control was executed.
By rolling, i.e. the wheelcillin of the turning inner wheel
It is realized by giving a large amount of decompression control amount to the
It Therefore, the ideal decompression control line and the approximate decompression control line
As shown in FIG. 36, the area between Gy> K / 2d
, The ideal pressure reduction control line is positioned below the approximate pressure reduction control line.
The relationship of placing is established.

As in the third embodiment, V _WI ^* = √ (V _WO
^2- K), when executing the braking force distribution control by using the target wheel speed V _WI ^* determined in order not to cause an unreasonable large difference between the slip ratio of the inner turning wheel and the slip ratio of the outer turning wheel. In the region where Gy> K · 2d holds, it is preferable that the approximate pressure reduction control amount for Gy and the ideal pressure reduction control amount are not greatly separated. In order to satisfy this requirement, it is appropriate to set K / 2d to a large value.

However, in the third embodiment, the region where Gy> K / 2d is established is set as the execution region of the braking force distribution control. Therefore, if K / 2d is set to a large value, the braking force distribution control cannot be started with excellent responsiveness. As described above, the braking force control apparatus according to the third embodiment described above has an advantage that the system can be realized without using the acceleration sensor 62, but it is effective control while ensuring excellent responsiveness. The problem is that it is difficult to perform power distribution control.

The braking force control system of the present embodiment is characterized in that it realizes the pressure reduction control line shown by the solid line in FIG. 37 to solve the problems of the system of the third embodiment. . That is, in this embodiment, the lateral acceleration Gy
The braking force distribution control is executed in a region where exceeds a predetermined value K ₁ . The predetermined value K ₁ is a constant smaller than K / 2d shown in FIG. Therefore, according to the device of the present embodiment, the braking force distribution control can be started with excellent responsiveness as compared with the above-described third embodiment. Further, in this embodiment, the target wheel speed V _WI ^* is V _WI ^* = √ (V _WO
² −2d · K ₂ ) is calculated. Constant K
₂ is a value equivalent to K / 2d shown in 36 above. Therefore, according to the apparatus of the present embodiment, the deviation between the ideal pressure reduction control amount and the pressure reduction control amount can be suppressed to be equal to the deviation between the ideal pressure reduction control amount and the approximate pressure reduction control amount in the third embodiment described above. it can. Therefore, according to the configuration of the present embodiment, it is possible to configure a braking force control device that can realize effective braking force distribution control while ensuring excellent responsiveness without using the acceleration sensor 62.

FIG. 38 shows an anti-virus system for realizing the above function.
One of control routines executed by the lock braking force control circuit 60
3 shows an example flow chart. The routine shown in FIG. 38 is started.
Then, first, in S270, the wheel speed of each wheel is read.
It is included. Next, in S271, the lateral acceleration Gy is estimated.
Is performed. As described above, the lateral acceleration Gy is
Wheel speed V_WOAnd the wheel speed V of the turning inner wheel_WIlAnd using
Gy = (V_WO ²-V_WI ²) / 2d
(See the above equation (12) and S191). In this step
Is the wheel speed V of the left and right front wheels in the above relational expression._Wfr,V_WflTo
The lateral acceleration Gy is calculated by substituting.

In this embodiment, the sign of Gy is positive when the vehicle is turning clockwise and the sign of Gy is negative when the vehicle is turning counterclockwise. the wheel speed V _Wfl the left front wheel to the wheel speed V _WO turning outer wheel side, the wheel speed V _Wfr ² of the right front wheel of the wheel speed V _WI of the turning inner wheel side are respectively substituted. The value of the lateral acceleration Gy estimated in this manner accurately matches the actual lateral acceleration Gy when the vehicle is in the non-decelerated state and the left and right front wheels have the same slip ratio.

When the estimation of the lateral acceleration Gy is completed, next, S
At 272, it is determined whether or not the brake switch 67 is on. As a result, the brake switch 67
If it is determined that is not on, the routine of this time is promptly ended. On the other hand, the brake switch 67
When it is determined that is ON, the process of S273 is executed next.

At S273, the turning inner wheel and the turning outer wheel are specified based on the sign of the estimated value of the lateral acceleration Gy.
In the present embodiment, when Gy> 0 is established, the left front wheel is determined as the outer turning wheel, and when Gy <0 is established, the right front wheel is determined as the outer rotation wheel.

Next, at S274, it is determined whether or not the absolute value | Gy | of the lateral acceleration Gy is larger than the predetermined value K ₁ , that is, the lateral acceleration Gy at which the braking force distribution control should be started for the vehicle. Is determined. as a result,
When it is determined that | Gy |> K ₁ is not established, it is determined that it is not necessary to start the braking force distribution control, and then this routine is immediately ended. On the other hand, | G
If it is determined that y |> K ₁ is established, in S275, V _WI ^* = √ (V _WO ² −2d · K ₂ ); (K ₂ >
The target wheel speed V _WI ^* is calculated according to the calculation formula K ₁ ).

Target wheel speed V_WI ^*When is calculated, next
Then, in S276, the wheel speed V of the turning inner wheel is_WIBut the eyes
Standard wheel speed V_WI ^*It is determined whether it is smaller than.
As a result, V_WI<V_WI ^*If is not satisfied, within the turn
It is judged that it is not necessary to reduce the brake hydraulic pressure on the wheel side,
After that, this routine ends. On the other hand, V_WI<V_WI
^*If it is determined that the
It is judged that the hydraulic pressure needs to be reduced, and it is controlled in S277.
Power distribution control is started. After that, in S278,
Wheel speed of pronation wheel V_WIIs the target wheel speed V_WI ^*And one
After the braking force on the inner wheel side of the turn has been controlled so that
Times routine is ended.

According to the above-mentioned processing, after the vehicle has shifted to the turning braking state, the braking force distribution control can be started with excellent responsiveness, and a large lateral acceleration Gy acts on the vehicle. Even in such a case, an appropriate braking force distribution ratio can be maintained without causing a large deviation between the slip ratio of the turning inner wheel and the slip ratio of the turning outer wheel. As described above, according to the braking force control device of the present embodiment, although the acceleration sensor 62 is not used,
Effective braking force distribution control can be executed.

By the way, as shown in FIG. 37, the pressure reduction control amount realized by the braking force control system of the present embodiment is K ₁
In the region of <Gy ≦ K _2, the value is suppressed to a value smaller than the ideal pressure reduction control amount. In this case, a larger slip ratio is given to the turning inner wheel than the slip ratio of the turning outer wheel, and a state in which the grip ability of the turning inner wheel and the grip ability of the turning outer wheel are not balanced is formed. However, K ₁ <Gy
At the time of turning at a low lateral acceleration where ≦ K ₂ , the grip capacity of the wheels has a sufficient margin, and thus the imbalance of the slip ratio does not pose a problem.

Further, as shown in FIG. 37, the pressure reduction control amount realized by the braking force control apparatus of the present embodiment is K ₂ <G
In the region of y, the value becomes larger than the ideal pressure reduction control amount. In this case, as described above, a larger slip ratio is given to the outer turning wheel than the slip ratio of the inner turning wheel, so that the grip ability of the inner turning wheel and the grip ability of the outer turning wheel are not balanced. However, the imbalance of the slip ratio is effective in increasing the non-turning moment acting on the vehicle. In order to obtain stable turning behavior during high lateral acceleration turning where K ₂ <Gy holds, it is preferable to impart understeer characteristics to the vehicle. In this respect, the braking force control device of the present embodiment, which easily generates a non-turning moment during high lateral acceleration turning, has an excellent effect in obtaining stable vehicle behavior during high lateral acceleration turning. .

In the above embodiment, the anti-lock braking force control circuit 60 executes the process of S270, whereby the outer wheel speed detecting means and the inner wheel speed detecting means according to the sixteenth aspect of the invention are provided. By executing the processing of S271, the lateral acceleration estimating means of claim 16 performs the processing of S274, and by the lateral acceleration determining means of claim 16, the lateral acceleration determining means of the claim 17 performs the processing of S275.
The target turning inside wheel speed calculating means according to claim 16 is realized by executing the processing of claim 16, and the braking force control means according to claim 16 is realized by executing the processing of steps S277 and S278. ing. Further, in the above-mentioned embodiment, the predetermined value K ₁ is the first set value according to claim 16 and the predetermined value K ₂ is the above-mentioned claim 1.
The second set values described in No. 6 correspond to each.

Next, referring to FIG. 39, the eighteenth embodiment of the present invention will be described.
Examples will be described. Braking force control device of the present embodiment
Must be realized using the system configuration shown in Figure 1 above.
Can be. In each of the embodiments described above, the target wheel of the turning inner wheel is
Speed V_WI ^*To V_WI ^*= √ (V _WO ²-2d ・ Gy)
Is V_WI ^*= √ (V_WO ²-K) etc.
(Fig. 5, Fig. 6, Fig. 18, Fig. 22, Fig. 38)
Etc.).

Generally, a computer used for an on-vehicle electronic control unit performs integer type arithmetic. For example,
Data that does not require so much precision is 1-byte data (0
0 to FF), which requires relatively high precision, is processed by integer type arithmetic as 2-byte data (0000 to FFFF).

The above equation for calculating the target wheel speed V _WI ^* includes the squared term of the wheel speed V _WO of the turning outer wheel.
In calculating the target wheel speed V _WI ^* , high accuracy is required for the wheel speed V _WO of the turning outer wheel, so V _WO must be 2-byte data. Therefore, the squared term “V _WO ² ” includes 4-byte data (00000000 to F
FFFFFFF). When processing 4-byte data, a large memory capacity is required and a long operation time is required as compared with the case where all the data is data of 2 bytes or less. For this reason, it is desirable that the arithmetic expression does not include the squared term, assuming the processing by the vehicle-mounted computer.

Further, the calculation of the target wheel speed V _WI ^* includes the calculation of the route. In order to calculate the route by the vehicle-mounted computer, it is necessary to perform a multi-step calculation combining the four arithmetic operations. Therefore, in order to execute an operation including a root operation, a large memory capacity is required as compared with the case where only four arithmetic operations are required, and a long operation time is required, and a long control is required. A program is needed. For this reason, when assuming the processing by the vehicle-mounted computer, it is desirable that the arithmetic expression to be executed is composed of only four arithmetic operations.

From this point of view, the braking force control apparatus of the present embodiment sets the target wheel speed V _WI ^* to a value that does not include the squared term, and
It is characterized in that it is approximately obtained by an arithmetic expression composed of only four arithmetic operations. The approximation method used in this embodiment will be described below.

Target wheel speed V _WI ^* shown in the above equation (11)
The relation of √ (V _WO ² −2d · Gy) can be modified as in the following equation. V _WO ² −V _WI ^{* 2} = 2d · Gy (37) By factoring the left side, the above equation (37) can be transformed into the following equation.

(V _WO −V _WI ^* ) · (V _WO + V _WI ^* ) = 2d · Gy (38) By the way, the vehicle speed V detected by the vehicle speed sensor 61.
_B is the wheel speed V _WO of the turning outer wheel and the wheel speed V _WO of the turning inner wheel
It can be approximated to the average value with _WI . Further, during execution of the braking force distribution control, the wheel speed V _WI of the turning inner wheel is considered to accurately match the target wheel speed V _WI ^* . Therefore, in the above formula (38), (V _WO + V _WI ^* ) is
It can be approximated as (V _WO + V _WI ) = 2 · V _B. According to this approximation method, the above (38) can be expressed by the following equation.

V _WO −V _WI ^* = d · Gy / V _B (39) Therefore, the target wheel speed V _WI ^* is calculated by an arithmetic expression that does not include a square term and that is configured by only four arithmetic operations. , Can be expressed as the following equation. V _WI ^* = V _WO −d · Gy / V _B (40) In the above method, an approximation method in which the wheel speed V _WI of the turning inner wheel and its target wheel speed V _WI ^* are the same It is included. Therefore, for example, in the process in which the wheel speed V _WI changes, a deviation may occur between the two, and the approximation accuracy may deteriorate. However, the target wheel speed V _WI ^* is calculated by the antilock braking force control circuit 60 for several msec.
It is executed every time. In such a short time, since no significant change in the wheel speed V _WI, target wheel speed V _WI ^*, the calculated target wheel speed V _WI ^* The above approximation method, the error is superimposed as a practical problem There is no such thing. For this reason,
According to the braking force control device of the present embodiment, it is possible to realize a small memory capacity and a high processing speed without causing any substantial adverse effects.

The above function is realized by the antilock braking force control circuit 60 executing the routine shown in FIG. Note that, in FIG. 39, the same steps as those shown in FIG. 5 are given the same reference numerals in parentheses, and the description thereof will be omitted or simplified.

When the routine shown in FIG. 39 is started, S
At 280, the output signals of the wheel speed sensors 63 to 66 and the output signal of the acceleration sensor 62 are read. Then S28
At 1, the vehicle speed V _B is read from the vehicle speed sensor 62. Next, in S282, it is determined whether or not Gy> 0 is satisfied. As a result, if Gy> 0 is satisfied, S28
In 3, the left wheel is made the outer wheel, while when Gy> 0 is not satisfied, the right wheel is made the outer wheel in S284.

After the above processing is completed, next, step S285.
In the above, the target wheel speed V _WI ^* is calculated using the above equation (40) ^.
= V _WO- d · Gy / V _B is calculated. This step S2
The calculation of 85 is performed by an arithmetic expression that does not include a square term and is configured by only simple four arithmetic operations.

After the target wheel speed V _WI ^* has been calculated, it is then determined in S286 whether V _WI ^* > V _WI holds. As a result, when V _WI ^* > V _WI holds, the routine for this time is terminated after the processing for reducing the brake hydraulic pressure of the turning inner wheel is executed in S287.
On the other hand, if it is determined in S286 that V _WI ^* > V _WI is not established, it is determined in S288 whether V _WI ^* <V _WI is established. As a result, if V _WI ^* <V _WI is satisfied, the process for increasing the brake hydraulic pressure of the turning inner wheel is executed in S289, and then this routine is ended. Further, when it is determined in S288 that V _WI ^* <V _WI is not established, the routine for this time is ended after the processing for holding the brake hydraulic pressure of the turning inner wheel is executed in S290.

By the way, in the above-mentioned routine,
Although the vehicle speed V _B is detected using the vehicle speed sensor 61, the present invention is not limited to this.
That is, in the field of a vehicle braking force control device, there is known a method of accurately estimating the vehicle body speed based on the detection values of the wheel speed sensors 63 to 66 without using the vehicle speed sensor 61. Antilock braking force control circuit 60, when calculating the estimated vehicle speed VSO using such known techniques, instead of the vehicle speed V _B shown in the above equation (40) using such estimated vehicle speed VSO The braking force distribution control may be executed.

In the above embodiment, the anti-lock braking force control circuit 60 executes the process of S285 to realize the target turning inside wheel speed calculating means.

[0287]

As described above, according to the first aspect, the target wheel speed of the inner wheel at the time of turning is calculated so that the left and right wheels are locked simultaneously based on the vehicle body speed, the wheel speed on the outside of the turning, and the lateral acceleration. , The target wheel speed of the turning inner wheel is calculated according to the vehicle body speed and the lateral acceleration by controlling the braking force of the turning inner wheel so as to reach the target wheel speed obtained by this calculation. The braking force of the wheel on the inside of the turn is controlled so that Therefore, the brake pressure is controlled so that the slip ratios of the respective wheels are the same, so that the running stability at the time of turning braking can be improved and the braking distance that can further improve the braking performance can be shortened.

According to claim 2, when the target turning inner wheel speed is V _WI , the vehicle body speed is V _B , the lateral acceleration is Gy, and the turning outer wheel speed is V _WO , V _WI = { (V _B −d · Gy / 2V _B ) / (V _B + d · G
y / 2V _B )} · V _WO By calculating the target turning inner wheel speed V _WI , the yaw rate of the vehicle rotation and the yaw rate of the revolution match so that the inner wheel side and the outer wheel side at the time of turning braking simultaneously. The braking force of each wheel is controlled so as to lock.

Further, according to claim 3, V _WI = (V _WO ² -2dGy) ^1/2 target turning inner wheel speed V _WI is calculated by the following equation, and the inner wheel side and the outer wheel side during turning braking are calculated. The braking force of each wheel is controlled so that the deviation of the slip ratio becomes zero, and the inner wheel side and the outer wheel side are locked simultaneously during turning braking.

According to the fourth aspect, when it is determined that V _WO ² −V _WI ² > K during turning braking without detecting the lateral acceleration Gy, V _WO ² −V _WI ² = K. The braking force of each wheel is controlled to control the braking force of each wheel so that the deviation of the slip ratio between the inner wheel side and the outer wheel side during turning braking becomes zero. Lock at the same time.

According to the fifth aspect, the target turning outer wheel speed for generating the anti-spin moment is calculated based on the vehicle body speed, the turning inner wheel speed, and the lateral acceleration,
By applying a braking force to the outer wheels so that the wheel speed on the outside of the turning becomes the target wheel speed on the outside of the turning, it is possible to generate an optimum anti-spin moment during non-braking of the turning and maintain the running stability.

According to the sixth aspect of the invention, V
V _WO ² -V _WI ² = K when it is determined that the _WO ² -V _WI ^2> K
By applying the braking force to the wheels on the outside of the turning so as to satisfy the following condition, it is possible to generate the optimum anti-spin moment during the non-braking of the turning without detecting the lateral acceleration Gy and maintain the running stability.

According to the present invention, the estimated lateral acceleration is calculated from the wheel speed, and the lateral acceleration detected by the lateral acceleration detecting means is compared with the estimated lateral acceleration to detect occurrence of abnormality in the lateral acceleration detecting means. Determine the presence or absence. Then, when it is determined that the lateral acceleration detecting means is abnormal, the target wheel speed of the inside wheel at the time of turning is calculated based on the turning outside wheel speed detected by the wheel speed detecting means, and the turning inside wheel speed is the target. By controlling the braking force of the wheel on the inside of the turn so as to reach the target wheel speed calculated by the wheel speed on the inside of the turning means, the running stability during turning braking can be maintained even if the lateral acceleration detecting means fails. .

According to the eighth aspect, at the time of turning braking, the target wheel speed of the front inner wheel is calculated so that the left and right wheels are locked simultaneously based on the vehicle speed, the front outer wheel wheel speed before turning, and the lateral acceleration. During braking, the target wheel speed of the rear-turn outer wheel is calculated based on the front-turn outer wheel wheel speed, and the target wheel speeds of the rear-turn inner wheel and the rear-turn outer wheel are calculated based on the front-turn outer wheel wheel speed. Then, each wheel speed is compared with each target wheel speed, and the brake pressure supplied to the brake mechanism is adjusted so that the wheel speed of each wheel becomes the target wheel speed, so that each wheel locks simultaneously. Apportions braking force to. Further, when it is detected that the road surface on which the outer wheel travels is lower in friction than the road surface on which the inner wheel travels (low μ road) at the time of turning, an increase in brake pressure is applied to the inner wheel after turning and the outer wheel after turning, In order to control the brake pressure to the inner wheel after turning and the outer wheel after turning by comparing the holding and decompressing commands and selecting the command to lower the brake pressure, if the outer wheel side is on a low μ road, the rear wheel If the brake pressure to the wheels on the outside of the turn is first reduced, a moment that promotes turning of the vehicle is generated and oversteer occurs, but in such a case, the rear wheels are controlled to the same wheel speed and It is possible to prevent a moment in the turning direction from being generated due to a difference in braking force between the outer turning wheel and the braking force.

According to the invention of claim 9, the threshold value used for determining the turning state is changed according to the vehicle speed, so that after the vehicle starts to turn, the turning inner wheel is changed at different timing depending on the vehicle speed. The braking force control of can be started. Therefore, according to the braking force control device of the present invention, when a high speed lane change or the like is performed while preventing the braking force control from being unnecessarily executed at the time of turning traveling accompanied by low lateral acceleration. Moreover, the desired braking force control can be executed based on the excellent responsiveness.

According to the tenth aspect of the invention, the target wheel speed of the rear wheels during braking is made smaller than the target wheel speed of the front wheels, so that the braking ability of the rear wheels can be effectively utilized. it can. Therefore, according to the braking force control device of the present invention, in order to prevent the rear wheels from being locked, the target wheel speed of the rear wheels is always set higher than the target wheel speed of the front wheels. A large braking force can be generated.

According to the eleventh aspect of the invention, the target wheel speed of the rear wheels is set to be higher than the target wheel speed of the front wheels under the condition that all the wheels can maintain proper grip states. Therefore, under such a situation, the braking ability of the rear wheels is effectively utilized, and a high braking ability can be realized in the vehicle. Further, under the situation where it is determined that any of the wheels may be in the locked state, the target wheel speed of the rear wheels is made higher than the target wheel speed of the front wheels. For this reason, wheel locking always occurs on the front wheel side prior to the rear wheel. Therefore, according to the braking force control device of the present invention, it is possible to achieve both high braking performance and stable vehicle behavior near the limit.

According to the twelfth aspect of the present invention, the control of the braking force can be prohibited when the wheel speed that is the basis of the calculation of the target wheel speed of the turning inner wheel is unstable.
Therefore, according to the braking force control device of the present invention, it is possible to avoid the inconvenience that the braking force of the turning inner wheel is inappropriately controlled during traveling on a rough road.

According to the thirteenth aspect of the invention, when it is determined that the system is abnormal based on the duration of the control for reducing the braking force of the turning inner wheel,
The control of the braking force can be stopped. Therefore, according to the braking force control device of the present invention, when the system is abnormal,
It is possible to avoid the inconvenience that the braking force of the turning inner wheel is inappropriately controlled.

According to the fourteenth aspect of the invention, when the understeer characteristic is detected in the vehicle, the control of the braking force that promotes the understeer characteristic is stopped. Therefore, according to the braking force control device of the present invention, it is possible to avoid the disadvantage that the understeer characteristic is promoted by controlling the braking force of the turning inner wheel.

According to the fifteenth aspect of the present invention, when the understeer characteristic is detected in the vehicle, the braking force control of the turning inner wheel can be stopped to increase the braking force, and the turning outer wheel can be controlled. The power can be controlled to suppress further increase in the braking force. Therefore, according to the braking force control device of the present invention, by quickly reducing the deviation between the braking force of the turning inner wheel and the braking force of the turning outer wheel, the understeer characteristic of the vehicle can be swiftly and reliably achieved. Can be suppressed.

According to the sixteenth aspect of the present invention, the execution area of the braking force control can be freely set by setting the first set value as the threshold value used for determining whether to execute the braking force control. It is said that. Further, by calculating the target wheel speed of the turning inner wheel on the assumption that the second setting value larger than the first setting value is the lateral acceleration acting on the vehicle, the turning inner wheel of the turning inner wheel is calculated over a wide area. It is possible to realize a braking state in which the slip state and the slip state of the turning outer wheel are not significantly different from each other. As described above, according to the braking force control device of the present invention, the slip ratio of the inner turning wheel and the slip ratio of the outer turning wheel are matched in a free region without providing a mechanism for detecting an accurate lateral acceleration. Control can be performed.

According to the seventeenth aspect of the present invention, the target wheel speed V _WI ^* of the turning inner wheel can be obtained by only the four-law calculation without using complicated calculation rules such as the square calculation and the route calculation. . Therefore, according to the braking force control device of the present invention, it is possible to obtain the target wheel speed V _WI ^* of the turning inner wheel with a small memory capacity, using a simple program, and in a short time.

[Brief description of drawings]

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

FIG. 2 is a flowchart for explaining a braking force control process executed by an antilock braking force control circuit according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a speed relationship of a vehicle body that acts when the vehicle is turning.

FIG. 4 is a diagram showing wheel speeds of respective wheels that act when the vehicle is turning.

FIG. 5 is a flowchart for explaining a braking force control process executed by an antilock braking force control circuit according to the second embodiment of the present invention.

FIG. 6 is a flowchart illustrating a braking force control process executed by an antilock braking force control circuit according to a third embodiment of the present invention.

FIG. 7 is a flowchart for explaining a braking force control process executed by an antilock braking force control circuit according to a fourth embodiment of the present invention.

FIG. 8 is a flowchart illustrating a braking force control process executed by an antilock braking force control circuit according to a fifth embodiment of the present invention.

FIG. 9 is a flowchart illustrating a braking force control process executed by an antilock braking force control circuit according to a sixth embodiment of the present invention.

FIG. 10 is a flowchart illustrating a braking force control process executed by an antilock braking force control circuit according to a seventh embodiment of the present invention.

FIG. 11 is a flowchart illustrating a braking force control process executed by an antilock braking force control circuit according to an eighth embodiment of the present invention.

FIG. 12 is a flowchart for explaining a braking force control process executed subsequent to the process of FIG.

13 is a flowchart for explaining a braking force control process that is executed subsequent to the process of FIG.

FIG. 14 is an example of a map used in a ninth embodiment of this embodiment.

FIG. 15 is a flowchart of an example of a control routine executed in a ninth embodiment of this embodiment.

FIG. 16 is a diagram for explaining a braking force distribution characteristic realized by using a proportioning valve.

FIG. 17 is a diagram for explaining a braking force distribution characteristic realized by the tenth embodiment of the present invention.

FIG. 18 is a flowchart of an example of a control routine executed in the tenth embodiment of the present embodiment.

FIG. 19 is a diagram for explaining a braking force distribution characteristic realized by the eleventh embodiment of the present invention.

FIG. 20 is a flowchart of an example of a control routine executed in the eleventh embodiment of the present invention.

FIG. 21 is a diagram showing how the deviation ΔV between the target wheel speed V _WI ^* and the wheel speed V _WI varies when the wheel speed is unstable.

FIG. 22 is a flowchart of an example of a control routine executed in the twelfth embodiment of the present invention.

FIG. 23 is a time chart for explaining the operation of the twelfth embodiment of the present invention.

FIG. 24 is characteristic value coordinates for explaining a method of detecting a steering characteristic in the thirteenth embodiment of the present invention.

FIG. 25 is a diagram showing a correspondence between each region in the characteristic value coordinates shown in FIG. 24 and a vehicle state.

FIG. 26 is a flowchart of an example of a control routine executed in the thirteenth embodiment of the present invention.

FIG. 27 is a diagram showing a variation state of the brake hydraulic pressure of the turning inner and outer wheels realized by the thirteenth embodiment of the present invention.

FIG. 28 is a flowchart of an example of a control routine executed in the fourteenth embodiment of the present invention.

FIG. 29 is a diagram showing a variation state of the brake hydraulic pressure of the turning inner and outer wheels realized by the fourteenth embodiment of the present invention.

FIG. 30 is a flowchart of an example of a control routine executed in the fifteenth embodiment of the present invention.

FIG. 31 is a diagram showing a variation state of the brake hydraulic pressure of the turning inner and outer wheels realized by the fifteenth embodiment of the present invention.

FIG. 32 is a time chart for explaining the operation of the sixteenth embodiment of the present invention (operation when the brake path is normal).

FIG. 33 is a time chart for explaining the operation of the sixteenth embodiment of the present invention (operation when a failure occurs in the brake path).

FIG. 34 is a flowchart of an example of a control routine executed in the sixteenth embodiment of the present invention.

[Figure 35] relationship between the target wheel speed V _WI ^* and lateral acceleration Gy is calculated on the basis of the lateral acceleration Gy, and the target wheel speed is calculated without using the lateral acceleration Gy V _WI ^* and the lateral acceleration Gy It is a figure which shows the relationship of.

FIG. 36 shows the relationship between the ideal pressure reduction control amount and the lateral acceleration Gy,
It is a figure which shows the relationship between the approximate decompression control amount and the lateral acceleration Gy.

FIG. 37 is a diagram showing the relationship between the pressure reduction control amount and the lateral acceleration Gy realized in the seventeenth embodiment of the present invention.

FIG. 38 is a flowchart of an example of a control routine executed in the seventeenth embodiment of the present invention.

FIG. 39 is a flowchart of an example of a control routine executed in the eighteenth embodiment of the present invention.

[Explanation of symbols]

 1 Brake Pedal 3 Master Cylinder 4, 5 Reservoir 6-9 Wheel Cylinder 10 1st Brake Pipeline 11 2nd Brake Pipeline 12-15 Pressure Increase Hydraulic Pressure Switching Valve 16-19 Pressure Reduction Hydraulic Pressure Changeover Valve 20-27 For Supply Pipe line 28a-28d Supply system line 29-34 Reflux pipe line 54,55 Suction pump 60 Anti-lock braking force control circuit 61 Vehicle speed sensor 62 Acceleration sensor 63-66 Wheel speed sensor 67 Brake switch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Hara, Toyota City, Toyota City, Aichi Prefecture, Toyota Toyota Motor Corporation (72) Inventor, Tadashi Chiba, Toyota City, Toyota City, Aichi Prefecture, Toyota City, Toyota

Claims (17)

[Claims] 1. A vehicle body speed detecting means for detecting a vehicle body speed of a vehicle, a wheel speed detecting means for detecting a speed of each wheel of the vehicle, and a lateral acceleration detecting means for detecting a lateral acceleration acting on the vehicle. A turning state determining unit that determines whether the vehicle is in a turning state, a braking state determining unit that determines whether the vehicle is in a braking state, and a determination that the vehicle is in a turning braking state In this case, based on the vehicle speed, the lateral acceleration, and the wheel speed of the turning outer wheel detected by the wheel speed detecting means,
Target turning inner wheel speed calculating means for calculating the target wheel speed of the turning inner wheel so that the slip state of the turning outer wheel and the slip state of the turning inner wheel are the same, and the wheel speed of the turning inner wheel becomes the target wheel speed. And a braking force control means for controlling the braking force of the turning inner wheel, and a braking force control device. 2. The braking force control device according to claim 1, wherein the target turning inside wheel speed calculation means is a target turning inside wheel speed V _WI , a vehicle body speed is V _B , a lateral acceleration is Gy, and a turning outside wheel speed. Where V _WO is V _WI = {(V _B −d · Gy / 2V _B ) / (V _B + d · G)
y / 2V _B )} · V _WO A braking force control device characterized by calculating a target turning inner wheel speed V _WI . 3. The braking force control device according to claim 1, wherein the target turning inner wheel speed calculation means calculates V _WI = (V _WO ² −2dGy) ^1/2 target turning inner wheel speed V _{WI according} to the following equation. A braking force control device characterized by being calculated. 4. A turning outer wheel speed detecting means for detecting the turning outer wheel speed V _WO, a turning inner wheel speed detecting means for detecting the turning inner wheel speed ^{_{V WI, V WO 2 -V WI}} 2> K (K Is a predetermined value), a non-braking state detecting means for detecting a non-braking state, and V _WO ² -V _WI ² > K during turning braking V _WO
Braking force control device characterized by comprising a braking force control means for controlling the braking force of the turning inner wheel so as to be ² -V _WI ² = K, a. 5. A vehicle body speed detecting means for detecting a vehicle body speed of a vehicle, a wheel speed detecting means for detecting a speed of each wheel of the vehicle, and a lateral acceleration detecting means for detecting a lateral acceleration of the vehicle. Braking detection means for detecting the braking state of the vehicle, vehicle body speed detected by the vehicle body speed detection means, turning inside wheel speed detected by the wheel speed detection means,
Target turning outer wheel speed calculating means for calculating a target turning outer wheel speed for generating an anti-spin moment based on the lateral acceleration detected by the lateral acceleration detecting means; and the turning outer wheel speed having the target turning outer wheel speed. And a braking force control means for applying a braking force to the outer wheels so that the speed becomes a speed. 6. A turning outer wheel speed detecting means for detecting the turning outer wheel speed V _WO, a turning inner wheel speed detecting means for detecting the turning inner wheel speed ^{_{V WI, V WO 2 -V WI}} 2> K (K Is a predetermined value), non-braking state detecting means for detecting a non-braking state, and V _WO ² -V _WI ² > K during non-braking V _WO ²
And a braking force control means for applying a braking force to the wheels on the outside of the turn so that V _WI ² = K. 7. A vehicle body speed detecting means for detecting a vehicle body speed of a vehicle, a wheel speed detecting means for detecting a speed of each wheel of the vehicle, and a lateral acceleration detecting means for detecting a lateral acceleration of the vehicle. Braking detection means for detecting a braking state of the vehicle, lateral acceleration estimation means for calculating an estimated lateral acceleration from wheel speeds detected by the wheel speed detection means, lateral acceleration detected by the lateral acceleration detection means, and Abnormality occurrence determination means for determining whether or not there is an abnormality in the lateral acceleration detection means by comparing with the estimated lateral acceleration; and when the abnormality occurrence determination means determines that the lateral acceleration detection means is abnormal, A target turning inside wheel speed calculating means for calculating a target wheel speed of the inside wheel during turning based on the turning outside wheel speed detected by the wheel speed detecting means; Braking force control device characterized by wheel speed and a braking force control means for controlling the braking force of the turning inner wheel such that it becomes equal to the target wheel speed computed by the target slewing inner wheel speed calculating means. 8. A vehicle speed detecting means for detecting a vehicle speed of a vehicle, a wheel speed detecting means for detecting a speed of each wheel of the vehicle, and a lateral acceleration detecting means for detecting a lateral acceleration acting on the vehicle. A turning braking state determining means for determining whether or not the vehicle is in a turning braking state, a vehicle body speed detected by the vehicle body speed detecting means during braking, and a front outer wheel wheel speed of a turning side detected by the wheel speed detecting means And, based on the lateral acceleration detected by the lateral acceleration detecting means, the target wheel speed of the inner wheel before turning is calculated so that the slip state of the outer wheel before turning and the slip state of the inner wheel before turning become the same. A target turning front inner wheel speed calculating means and a target wheel speed of the rear turning outer wheel based on the front turning outer wheel speed detected by the wheel speed detecting means during braking. A target turning rear side outer wheel speed calculating means, and a target turning rear side inner wheel speed calculating means for calculating a target wheel speed of the turning rear side inner wheel based on the turning front side outer wheel wheel speed detected by the wheel speed detecting means during braking. A brake that compares the wheel speeds detected by the wheel speed detection means with the target wheel speeds and adjusts the brake pressure supplied to the brake mechanism so that the wheel speeds of the wheels become the target wheel speeds. Pressure adjusting means, brake pressure switching means for switching the brake pressure to each wheel among pressure increasing, holding, and pressure reducing according to a command from the brake pressure adjusting means; A crossing road detecting means for detecting that the road is a low friction road (low μ road), and when the crossing road is detected by the crossing road detecting means,
Brake pressure command selecting means for comparing the brake pressure increasing, holding, and decompressing commands to the inner wheel after turning and the outer wheel after turning and selecting a command for making the brake pressure lower side, and the brake pressure command selecting means Switching operation of the brake pressure switching mechanism based on the brake pressure command selected from
A braking force control device, comprising: braking force control means for controlling a brake pressure applied to the inner wheel after turning and the outer wheel after turning. 9. The braking force control device according to claim 1, wherein the turning state determining means includes threshold changing means for changing a threshold used for determining the turning state according to a vehicle body speed. A characteristic braking force control device. 10. The braking force control device according to claim 1, wherein when the vehicle is in a braking state, the target wheel speed of the rear wheels is
A braking force control device comprising: first target wheel speed setting means for setting target wheel speeds of front and rear wheels so as to be smaller than a target wheel speed of front wheels. 11. The braking force control device according to claim 10, wherein slip ratio detecting means for detecting a slip ratio of at least one of the front wheels and the rear wheels, and a target wheel speed of the rear wheels when the vehicle is in a braking state. But,
Second target wheel speed setting means for setting the target wheel speeds of the front and rear wheels so as to be larger than the target wheel speed of the front wheels, and the slip ratio detected by the slip ratio detecting means is below a predetermined value. The target wheel speed set by the first target wheel speed setting means, and the target wheel speed set by the second target wheel speed setting means when the slip ratio exceeds a predetermined value. A braking force control device, comprising: a target wheel speed switching unit that is adopted as a wheel speed. 12. The braking force control device according to claim 1, wherein wheel speed instability detection means for detecting instability of wheel speed, and braking force when the instability of wheel speed exceeds a predetermined value. And a braking force control inhibiting means for inhibiting the control of the braking force control device. 13. The braking force control device according to claim 1, wherein when the braking force of the turning inner wheel is continuously reduced for a predetermined period of time, the control of the braking force of the turning inner wheel is stopped. A braking force control device comprising power control stopping means. 14. The braking force control device according to claim 1, further comprising: steering characteristic detecting means for detecting a steering characteristic of the vehicle; and, when the steering characteristic is understeer, stopping the control of the braking force of the turning inner wheel. 2. A braking force control device comprising: a braking force control stopping unit of 2; 15. The braking force control device according to claim 14, wherein when the control of the braking force of the turning inner wheel is stopped, the control of the turning outer wheel is controlled so that the increase of the braking force of the turning outer wheel becomes gentle. A braking force control device comprising a turning outer wheel braking force control means for controlling power. 16. An outer wheel wheel speed detecting means for detecting a wheel speed of a turning outer wheel, an inner wheel wheel speed detecting means for detecting a wheel speed of a turning inner wheel, and a wheel speed of the turning outer wheel and a wheel speed of the turning inner wheel. Then, the lateral acceleration estimating means for estimating the lateral acceleration acting on the vehicle, and the lateral acceleration estimated by the lateral acceleration estimating means are
And a lateral acceleration acting on the vehicle is a second set value which is larger than the first set value. A target turning inner wheel speed calculating means for calculating a target wheel speed of the turning inner wheel for equalizing the slip state of the turning outer wheel and the slip state of the turning inner wheel based on the wheel speed of the turning outer wheel; and the lateral acceleration estimating means. Braking force control means for controlling the braking force of the turning inner wheel so that the wheel speed of the turning inner wheel becomes the target wheel speed when the lateral acceleration estimated by the above exceeds the first set value. A braking force control device comprising: 17. The braking force control device according to claim 1, wherein the target turning inner wheel speed calculation means sets a target wheel speed V _WI ^* of the turning inner wheel, a wheel speed V _{WO of} the turning outer wheel, and a tread d of the vehicle. , the lateral acceleration Gy, and by using the vehicle speed ^{_{V B, V WI * = V}} WO -d · Gy / V B becomes operational braking force control apparatus characterized by calculating according to equation.