JP3114581B2 - Braking force control device - Google Patents

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 device which controls braking force of each wheel so that the slip rate of each wheel becomes the same during a braking operation during cornering. Related to the device.

[0002]

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

This type of antilock braking force control system has a pressure-intensifying solenoid valve and a pressure-reducing solenoid valve. It switches 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 is increased or held in the pressure increasing mode or the holding mode, and the wheel is controlled. If the power is increased and the vehicle is running and immediately before the wheels are locked, a pressure reducing mode for reducing the brake pressure is set to operate to prevent the wheels from locking. Then, when the vehicle stops, the opening / closing control of the pressure-increasing solenoid valve and the pressure-reducing solenoid valve is performed so as to adjust the brake pressure to each wheel so that the wheels are not locked simultaneously.

Further, in a vehicle running at a corner, the load on the outer wheels of the vehicle is increased by the lateral acceleration, while the load on the inner wheels is reduced. Therefore, when the driver depresses the brake pedal during turning of the vehicle, if the brake pressure on each wheel is increased equally, the inner wheel locks 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 such that the brake pressure supplied to the inner wheel is smaller than the brake pressure supplied to the outer wheel during turning braking. Was.

[0005] It is conceivable to stabilize the behavior of the vehicle by controlling the braking force of each wheel so that the braking pressure on the inside wheel when turning becomes small when the lateral acceleration becomes a predetermined value or more during turning braking. Have been. As a braking force control device for controlling this kind of braking force, for example, Japanese Patent Laid-Open Publication No.
There is an apparatus as disclosed in JP-A-8059.

In the device disclosed in the above publication, when braking is detected during turning of the vehicle, the pressure-increasing electromagnetic valve of the inner wheel is closed and the pressure-reducing electromagnetic valve of the wheel is opened for a predetermined time to reduce the brake pressure. The braking force of each wheel is controlled so as to decrease. Therefore, at the time of turning braking, an anti-spin moment in the direction opposite to the direction in which the vehicle spins due to a decrease in the brake pressure of the inner wheels is generated, thereby improving running stability during turning braking.

[0007]

However, in the device disclosed in the above-mentioned publication, during turning braking, the brake pressure is increased by closing the pressure-increasing solenoid valve of the inner wheel and opening the pressure-decreasing solenoid valve of the wheel for a certain period of time. Although the anti-spin moment is generated by lowering the inner wheel, there is no description on how much the braking pressure is reduced (or the amount of the braking pressure reduction).

Accordingly, in the apparatus disclosed in the above publication, for example, even if the brake pressure of the inner wheel is reduced during the turning braking, if the brake pressure is not sufficiently reduced, the difference in the braking force between the inner wheel and the outer wheel causes the braking force during the turning braking. Running stability cannot be maintained, and conversely, if the brake pressure is too low, the braking performance of the inner wheels will be reduced, which will increase the braking distance or generate an excessive anti-spin moment on the outer wheels. .

In view of the above problem, the present invention adjusts the brake pressure according to the lateral acceleration generated during turning braking so that the slip ratio of the inner wheel and the outer wheel becomes the same, thereby maintaining running stability during turning braking. The purpose is to:

[0010]

The above object is achieved by the present invention.
As described in, 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 acting on the vehicle, Turning state determining means for determining whether or not the vehicle is in a turning state; braking state determining means for determining whether or not the vehicle is in a braking state; and determining that the vehicle is in a turning braking state. In this case, the slip state of the turning outer wheel and the slip state of the turning inner wheel are the same based on the vehicle speed, the lateral acceleration, and the actual wheel speed of the turning outer wheel detected by the wheel speed detecting means. A target turning inside wheel speed calculating means for calculating a target wheel speed of the turning inner wheel; a braking force control means for controlling a braking force of the turning inner wheel so that the wheel speed of the turning inner wheel becomes the target wheel speed; Braking force control device characterized by comprising

According to the first aspect of the present invention, the target wheel speed of the inner wheel at the time of turning is calculated based on the vehicle speed, the turning outer wheel speed, and the lateral acceleration so that the left and right wheels are locked simultaneously.
By controlling the braking force of the turning inner wheels so that the target wheel speed obtained by this calculation is obtained, the brake pressure is controlled so that the slip ratio of each wheel becomes the same, and the running stability during turning braking is improved. At the same time, the braking distance that can further enhance the braking performance can be shortened.

[0012] The object of the present invention is as described in claim 2.
2. The braking force control device according to claim 1, wherein the target turning inner wheel speed calculating means sets the target turning inner wheel speed to V _WI , the vehicle speed to V _B , the lateral acceleration to Gy, and the turning outer wheel speed to V _WO . In this case, V _WI = ｛(V _B −d · Gy / 2 V _B ) / (V _B + d · G)
y / 2V _B )｝ · V _{WO This} is achieved by a braking force control device that calculates the target turning inside wheel speed V _WI .

According to the second aspect, when the target turning inside wheel speed is V _WI , the vehicle speed is V _B , the lateral acceleration is Gy, and the turning outside 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 rotation of the vehicle and the yaw rate of the revolution are made to coincide with each other so that the inner wheel side and the outer wheel side at the time of turning braking are simultaneously performed. Control the braking force of each wheel to lock.

[0014] The object of the present invention 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 This is also achieved by the control device.

According to the third aspect, V _WI = (V _WO ² -2 dGy) ^1/2 target turning inside wheel speed V _WI is calculated by the following equation to determine 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 during turning braking are locked simultaneously.

The above object is _achieved by a turning outer wheel speed detecting means for detecting a turning outer wheel speed V _WO , a turning inner wheel speed detecting means for detecting a turning inner wheel speed V _WI , ^{_{V WO 2 -V WI 2> K}} (K is a predetermined value) determining means for determining whether a, a non-braking state detecting means for detecting a non-braking state, V _WO ² -V _WI ² during turning braking >
When determined to be K, the slip ratio and turning of the outside wheel
V _WO ² − to reduce the deviation from the slip ratio of the inner wheel to zero
A braking force control device comprising: braking force control means for controlling a braking force of a turning inner wheel so that V _WI ² = K.

According to the fourth aspect, the lateral acceleration Gy is detected.
V during turning braking without_WO ^Two-V _WI ^Two> K
When V_WO ^Two-V_WI ^Two= K
Slip between the inner and outer wheels during turning braking by controlling the braking force
Control the braking force of each wheel so that the deviation of the tapping ratio becomes zero
To lock the inner wheel and outer wheel simultaneously during turning braking.
You.

The above object is achieved by a vehicle 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 direction of the vehicle. Lateral acceleration detecting means for detecting the acceleration of the vehicle, braking detecting means for detecting the braking state of the vehicle, vehicle speed detected by the vehicle speed detecting means, turning inside wheel speed detected by the wheel speed detecting means, a target turning outer wheel speed calculating means for calculating a target turning outer wheel speed for generating anti-spin moment on the basis of the lateral acceleration detected by said lateral acceleration detection means, the turning
Between the slip rate of the outer wheel and the slip rate of the turning inner wheel
Braking force control means for applying a braking force to outer wheels such that the turning outer wheel speed becomes the target turning outer wheel speed in order to reduce the deviation to zero .

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, and the turning outer wheel speed is calculated as the target turning outer wheel speed. By applying a braking force to the outer wheels so as to satisfy the above condition, an optimum anti-spin moment can be generated when the vehicle is not turning and braking can be maintained.

The above object is _achieved by a turning outer wheel speed detecting means for detecting a turning outer wheel speed V _WO , a turning inner wheel speed detecting means for detecting a turning inner wheel speed V _WI , ^{_{V WO 2 -V WI 2> K}} (K is a predetermined value) determining means for determining whether a, a non-braking state detecting means for detecting a non-braking state, V _WO ² during non-braking -V _WI ² > K
Is determined, the slip ratio of the turning outer wheel and the turning
V _WO ² -V order to a deviation between the slip ratio of the side wheels to zero
Braking force control means for applying a braking force to the turning outer wheel such that _WI ² = K.

According to the sixth aspect, V _WO ² -V when braking is not performed
By _WI ^2> for applying braking force of the turning outer wheel such that V _WO ² -V _WI ² = K when it is determined that K, the optimal anti-spin turning during non-braking without detecting the lateral acceleration Gy The running stability can be maintained by generating a moment.

[0022] The above object is attained by the present invention.
The braking force control device according to claim 2 or 3, further comprising:
Lateral acceleration estimating means for calculating an estimated lateral acceleration from the wheel speed detected by the wheel speed detecting means; and lateral acceleration detection by comparing the lateral acceleration detected by the lateral acceleration detecting means with the estimated lateral acceleration. and a abnormality occurrence determination means for determining the presence or absence of abnormality of means, the
Target turning inner wheel speed calculating means, when the lateral acceleration detecting means is determined to be abnormal by the abnormality judging means during turning based on the turning outer wheel speed detected by said wheel speed detection means The target wheel speed of the inner wheel is calculated , and the abnormality occurrence determination means performs the calculation.
If the lateral acceleration detection means is determined to be normal,
The vehicle speed, the lateral acceleration, and the wheel speed detection
Based on the actual wheel speed of the turning outer wheel detected by the
And the slip condition of the turning outer wheel and the slip condition of the turning inner wheel.
Set the target wheel speed of the inner turning wheel so that
A braking force control device set to perform calculation .

According to the seventh aspect, 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 the lateral acceleration detecting means has an abnormality. judge. Then, when it is determined that the lateral acceleration detecting means is abnormal, the target wheel speed of the inner wheel at the time of turning is calculated based on the turning outer wheel speed detected by the wheel speed detecting means, and the turning inner wheel speed becomes the target. By controlling the braking force of the turning inner wheel so that the target wheel speed is calculated by the turning inner wheel speed calculating means, the running stability at the time of turning braking can be maintained even if the lateral acceleration detecting means fails. .

[0024] The above object is as described in claim 8.
Vehicle speed detecting means for detecting the vehicle speed of the vehicle, wheel speed detecting means for detecting the speed of each wheel of the vehicle, lateral acceleration detecting means for detecting a lateral acceleration acting on the vehicle,
Turning braking state determining means for determining whether the vehicle is in a turning braking state, a vehicle speed detected by the vehicle speed detecting means during braking, and a front outer wheel speed detected by the wheel speed detecting means. And calculating a target wheel speed of the inner wheel before turning based on the lateral acceleration detected by the lateral acceleration detecting means so that the slip state of the outer wheel before turning and the slip state of the inner wheel before turning are the same. A target turning front side inner wheel speed calculating means,
The target rear outer wheel speed calculating means for calculating the target wheel speed of the rear outer wheel based on the front outer wheel wheel speed detected by the wheel speed detecting means, and the wheel speed detecting means detecting the wheel speed during braking. A target rear inner wheel speed calculating means for calculating a target wheel speed of the rear inner wheel based on the front outer wheel wheel speed, and a comparison between each wheel speed detected by the wheel speed detecting device and each of the target wheel speeds. 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 applied to each wheel by a command from the brake pressure adjusting means. A brake pressure switching means for switching between pressure increasing, holding, and pressure reducing; and, when turning, a road surface on which an outer wheel runs has a lower friction road (low μ) than a road surface on which an inner wheel runs.
Road) and a command to increase, hold, and reduce the brake pressure applied to the inner wheel after turning and the outer wheel after turning when the step detecting device detects a staggered road. A brake pressure command selecting means for selecting a command to set the brake pressure to a lower pressure side; and a switching operation of the brake pressure switching mechanism based on the brake pressure command selected by the brake pressure command selecting means. This is also achieved by a braking force control device including: a braking force control unit that controls a brake pressure applied to the rear inner wheel and the turning rear outer wheel.

According to the present invention, the target wheel speed of the front inner wheel is calculated based on the vehicle speed, the outer wheel speed before turning, and the lateral acceleration during braking so that the left and right wheels are simultaneously locked. A target wheel speed of the rear outer wheel is calculated based on the front outer wheel speed, and a target main wheel speed of the rear inner wheel and the rear outer wheel is calculated based on the front outer 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. Distribute the braking force to. Further, at the time of turning, when it is detected that the road surface on which the outer wheel runs is a lower friction road (low μ road) than the road surface on which the inner wheel runs, brake pressure increase 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 pressure reducing commands and selecting the command to set the brake pressure to a lower pressure side, when the outer wheel side is a low μ road, the rear wheel If the brake pressure to the outer wheels is reduced first, a moment is generated that promotes the turning of the vehicle and oversteer occurs.In such a case, the rear wheels are controlled to the same wheel speed and the inner wheels are turned. A moment in the turning direction due to a difference in braking force between the turning outer wheel and the braking force is prevented.

According to a ninth aspect of the present invention, in the braking force control device according to the first aspect, the turning state determining means sets a threshold value used for determining the turning state to a vehicle speed. This is also achieved by a braking force control device provided with a threshold changing means that changes in accordance with the threshold value.

In the present invention, the threshold value changing means changes a threshold value used for determining a turning state according to the vehicle speed. Therefore, whether or not the vehicle is in a turning state is determined based on different criteria depending on the vehicle speed.
When the vehicle speed is high, it is desirable that control of the braking force of the turning inner wheel be started immediately after turning is started. On the other hand, when the vehicle 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 the vehicle is in a turning state based on different criteria according to the vehicle speed, the control of the braking force is started at an appropriate timing during both high-speed running and low-speed running.

According to a tenth aspect of the present invention, in the braking force control device according to the first aspect, when the vehicle is in a braking state, the target wheel speed of the rear wheel is set to the target wheel speed of the front wheel. This is also achieved by a braking force control device including first target wheel speed setting means for setting target wheel speeds of 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 speed of the front and rear wheels at the time of braking.
The target wheel speed of the rear wheel is set to be lower than the target wheel speed of the front wheel. 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 capability of the rear wheels is effectively used.

According to another aspect of the present invention, there is provided a braking force control apparatus according to the tenth aspect, wherein a slip ratio detecting means for detecting a slip ratio of at least one of a front wheel and a rear wheel; A 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 is greater than the target wheel speed of the front wheels when the is in a braking state; When the slip rate detected by the slip rate detecting means is equal to or smaller than a predetermined value, the target wheel speed set by the first target wheel speed setting means is set. This is also achieved by a braking force control device including target wheel speed switching means for adopting 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 a slip ratio of at least one of a front wheel and a rear wheel. At the time of braking, if the slip ratio of the wheel exceeds a predetermined value, the wheel shifts to the locked state without maintaining an appropriate grip state. During braking of the vehicle, it is desirable to generate a large braking force on the rear wheels while all the wheels maintain an appropriate grip state. Therefore, in such a situation, the target wheel speed switching means adopts 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 stably maintain the vehicle behavior. In order to shift the front wheel to the locked state prior to the rear wheel, it is necessary to increase the target wheel speed of the rear wheel as compared with the target wheel speed of the front wheel. Therefore, when the slip ratio detected by the slip ratio detection unit exceeds a predetermined value, the target wheel speed switching unit determines that any 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, the above object is achieved by a braking force control apparatus according to the first aspect.
A braking force comprising: wheel speed instability detecting means for detecting wheel speed instability; and braking force control inhibiting means for inhibiting braking force control when the wheel speed instability exceeds a predetermined value. This is also achieved by the control device.

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

[0034] According to a thirteenth aspect of the present invention, in the braking force control device according to the first aspect, when the braking force of the turning inner wheel is continuously reduced for a predetermined time, the turning inner wheel is turned off. This is also achieved by a braking force control device including first braking force control suspension means for suspending the control of the braking force.

In the present invention, the first braking force control suspending means is configured to control the braking force when the control for lowering the braking force is continuously performed 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 unduly long time, it can be determined that an abnormality has occurred in the system. The first braking force control suspending means suspends the control of the braking force when the abnormality occurs.

According to a fourth aspect of the present invention, there is provided a braking force control apparatus according to the first aspect, wherein the steering characteristic detecting means for detecting a steering characteristic of the vehicle, and the steering characteristic is understeer.
The present invention is also achieved by a braking force control device including: a second braking force control suspension means for suspending the control of the braking force of the turning inner wheel.

In the present invention, the steering characteristic detecting means detects a steering characteristic of the vehicle. When the vehicle is turning, if the degree of turning is excessive with respect to the steering angle, the oversteer characteristic is detected. If the degree of turning is insufficient with respect to the steering angle, the understeer characteristic is detected. Is detected. In order to correct the understeer characteristics, it is necessary to apply a larger turning moment to the vehicle. By the way, if the slip condition of the turning inner wheel is equal to the slip condition of the turning outer wheel, a larger braking force is generated on the turning outer wheel side than on the turning inner wheel side due to a load difference applied to the turning inner and outer wheels. I 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, a situation occurs in which the understeer characteristics of the vehicle are promoted. The second braking force control suspending means suspends 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 of the inner and outer wheels turning is reduced, that is, the moment acting on the vehicle in the non-turning direction is reduced, and the understeer characteristics are corrected.

According to the present invention, when the control of the braking force of the turning inner wheel is stopped, the braking force of the turning outer wheel is increased. This is also achieved by a braking force control device including turning outer wheel braking force control means for controlling the braking force of the turning outer wheel so that the braking force becomes gentle.

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 suspending means suspends 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. Thereafter, the steering characteristic of the vehicle changes from the understeer characteristic to the neutral 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 on the turning inner wheel is stopped, the braking force on the turning outer wheel is suppressed by the turning outer wheel braking force control means. Approaching the braking force, the understeer characteristics are quickly eliminated.

The above object is achieved by an outer wheel speed detecting means for detecting a wheel speed of a turning outer wheel, an inner wheel speed detecting means for detecting a wheel speed of a turning inner wheel, and Lateral acceleration estimating means for estimating the lateral acceleration acting on the vehicle based on the wheel speed and the wheel speed of the turning inner wheel; and whether the lateral acceleration estimated by the lateral acceleration estimating means exceeds a first set value. Lateral acceleration determining means for determining whether or not the lateral acceleration acting on the vehicle is a second set value larger than the first set value, based on a wheel speed of the turning outer wheel. A turning inside wheel speed calculating means for calculating a target wheel speed of the turning inner wheel for making the slip state of the turning outer wheel equal to the slip state of the turning inner wheel; and a lateral acceleration estimated by the lateral acceleration estimating means. Braking force control means for controlling the braking force of the turning inner wheel such that the wheel speed of the turning inner wheel becomes the target wheel speed when the degree exceeds the first set value. Is also achieved by

In the present invention, the lateral acceleration estimating means estimates the lateral acceleration acting on the vehicle based on the wheel speed of the turning outer wheel and the wheel speed of the turning inner wheel.
The lateral acceleration determining means determines whether or not the estimated value of the lateral acceleration estimated as described above exceeds a first set value. When the estimated value of the lateral acceleration exceeds the first set value, the braking force control means controls the braking force of the turning inner wheel 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 are obtained under the condition that acceleration equal to the second set value is acting on the vehicle. Is equivalent to Further, in a situation where a small acceleration compared to the second set value or a large acceleration compared to the second set value is acting on the vehicle, the turning inner wheel and the turning outer wheel are The two slip states are controlled so as not to be significantly different. 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. Is done.

The above object is also achieved by a braking force control device according to claim 1, wherein the target turning inside wheel speed calculating means calculates a target wheel speed V _WI ^* of the turning inner wheel. The wheel speed V _{WO of} the turning outer wheel, the tread d of the vehicle, the lateral acceleration Gy, and the vehicle speed V _B
Using also achieved by ^{_{V WI * = V WO -d ·}} Gy / V B becomes operational brake force control apparatus which calculates according to equation.

In the present invention, the target turning inner wheel speed calculating means calculates the target wheel speed V _WI ^* of the turning inner wheel according to a calculation formula of V _WI ^* = V _WO -d · Gy / V _B. The arithmetic expression used in the present invention includes a square operation,
No complicated arithmetic rules such as route arithmetic are used. Therefore, the operation can be executed in a short time without requiring a large amount of memory capacity, without using a complicated program.

[0044]

FIG. 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 depression force of the brake pedal 1 and a boosting action of the vacuum booster 2, and 4, 5 are brake fluids. Reservoirs for replenishing hydraulic fluid to a recirculation system described later, and 6 to 9 are wheel cylinders of a brake mechanism that brakes each wheel by receiving a brake pressure from the master cylinder 3.

The brake pressure generated by the master cylinder 3 when the brake pedal 1 is depressed is connected to the wheel cylinders 6 to 9 via first and second brake pipes 10 and 11. Reference numerals 12 to 15 denote pressure-increasing hydraulic pressure switching valves which are normally open solenoid valves. Normally, the valve elements 12a to 15a are urged to open positions, and brake pressure from the master cylinder 3 is applied to each of the wheel cylinders 6 to 9. To supply. But,
When the solenoids 12b to 15b are excited just before the wheels are locked, the valve bodies 12a to 15
“a” is switched to the valve closing position, and the operation is performed to stop the supply of the brake pressure from the master cylinder 3.

Reference numerals 16 to 19 denote a pressure-reducing hydraulic pressure switching valve composed of a normally-closed solenoid valve. keeping. However, the pressure-reducing hydraulic switching valves 16 to 1
In 9, the solenoids 16 b to 19 b are excited just before the wheels are locked, the valve bodies 16 a to 19 a are switched to the valve-open position, and the brake pressure to the wheel cylinders 6 to 9 is released to the reservoirs 4 and 5 to reduce the brake pressure. Operate to reduce pressure.

The supply lines 20 to 23 communicating with the first and second brake lines 10 and 11 and one end thereof communicates with the pressure-increasing hydraulic switching valves 12 to 15 and the pressure-reducing hydraulic switching valves 16 to 19. The supply pipes 24 to 27, the other ends of which are communicated with the wheel cylinders 6 to 9, respectively, form supply systems 28a to 28d for the respective wheel cylinders 6 to 9.

A recirculation line 2 having one end communicating with the pressure-reducing liquid pressure switching valves 16 to 19 and the other end communicating with the reservoirs 4 and 5.
9 to 32 and the return lines 33 and 34 extending from the reservoirs 4 and 5 to be connected to the first and second brake lines 20 and 21 form return lines 35a and 35b. .

The pressure-increasing hydraulic pressure switching valves 12 to 15 are provided with throttles 3 provided in a flow path communicating with supply-side pipes 20 to 23.
6 to 39, bypass flow paths 40 to 43 bypassing the throttles 36 to 39, and allowing the brake fluid on the wheel cylinders 6 to 9 side to return to the master cylinder 3 side via the bypass flow paths 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.

The pressure-reducing hydraulic pressure switching valves 26 to 29 are throttles for reducing the amount of brake fluid recirculated from the wheel cylinders 6 to 9 to a predetermined amount in a flow path communicating with the downstream recirculation pipes 29 to 32. 50 to 53. Suction pumps 54 and 55 for sucking the brake fluid in the reservoirs 4 and 5 to recirculate the master cylinder 3, and a reverse pump provided upstream of the suction pumps 54 and 55, respectively. Stop valves 56, 57
And check valves 58, 59 disposed downstream of the suction pumps 54, 55.

Each of the suction pumps 54 and 55 is constantly driven by a pump motor (not shown) while the antilock braking force control is being executed. And the suction pump 54,
Reference numeral 55 denotes a suction step when the pump plunger (not shown) moves down, and a discharge step when the pump plunger (not shown) moves up.

In the suction step, the suction pump 5
The check valves 56 and 57 disposed upstream of the suction pumps 54 and 55 are opened, and the check valves 58 59 disposed downstream of the suction pumps 54 and 55 are closed. In the discharge step, the check valves 56, 5 disposed upstream of the suction pumps 54, 55 are provided.
7 is closed, and the check valves 58 and 59 disposed downstream of the suction pumps 54 and 55 are opened.

As described above, the suction pumps 54, 55 are operated in accordance with the operating directions of the pump plungers of the suction pumps 54, 55.
When the check valves 56 and 57 and the check valves 58 and 59 disposed upstream and downstream of the cylinder open and close, the brake fluid is returned to the master cylinder 3. In the brake device having the antilock braking force control system having the above-described configuration, when the brake pedal 1 is depressed, the brake pressure is increased by the master cylinder 3 to enter the pressure increasing mode. In this pressure-increasing mode, the pressure-increasing hydraulic pressure switching valves 12 to 15 are kept in an open state, and the pressure-reducing hydraulic pressure switching valves 16 to 19 are kept in a closed state. Therefore, the increased brake pressure is applied to the first and second brake lines 10 and 11 and the supply line 2.
The wheels are supplied to the wheel cylinders 6 to 9 via supply pipes 0 to 23 and supply pipes 24 to 27, and the wheels are braked.

Then, for example, when the vehicle is braked immediately before the wheels are locked while traveling on a low μ road, the antilock braking force control system switches to the pressure reduction mode or the holding mode. In this pressure-reducing mode, the solenoids 12b of the pressure-increasing hydraulic pressure switching valves 12 to 15 corresponding to the wheels immediately before locking are performed.
~ 15b are excited and switched to the valve closed state,
Solenoids 16b-19 of decompression hydraulic switching valves 16-19
b switches 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 return pipe lines 29 to 32, so that the braking force on the wheels is released and the wheels are prevented from being locked.

In the holding mode, the pressure-increasing hydraulic switching valve 1
2 to 15 and the pressure-reducing hydraulic pressure switching valves 16 to 19 are kept in the closed state, and the brake pressure of the wheel cylinders 6 to 9 is maintained. During such anti-lock braking operation, the suction pumps 54 and 55 are always started to prevent the master cylinder 3 from running out of brake fluid. Therefore, when the decompression mode is set to the decompression mode during the antilock braking operation and the decompression hydraulic pressure switching valves 16 to 19 are opened, the brake fluid from the wheel cylinders 6 to 9 flows out to the recirculation pipelines 29 to 32. Then, the brake fluid in the reflux pipes 29 to 32 is sucked into the reflux pipes 33 and 34 by the suction operation of the suction pumps 54 and 55.

Thereafter, the brake fluid sucked by the suction pumps 54, 55 passes through the check valves 58, 59 and returns to the first and second brake lines 10, 11. However, during the anti-lock braking operation, for example, when the rotation speed of each wheel increases, the mode is switched from the pressure reducing mode to the pressure increasing mode or the holding mode, the pressure reducing hydraulic pressure switching valves 16 to 19 are closed, and the pressure increasing hydraulic pressure is changed. The switching valves 12 to 15 are opened.

When the mode is switched from the pressure-reducing mode to the pressure-increasing mode or the holding mode as described above, the brake fluid is continuously returned to the master cylinder 3 side by the suction operation of the suction pumps 54 and 55, so that the reservoir fluids 4 and 5 are filled. The brake fluid is sucked into the return pipe lines 33 and 34.

The pressure-increasing hydraulic pressure switching valves 12 to 15, the pressure-reducing hydraulic pressure switching valves 16 to 19, and the suction pumps 54 and 55
Is activated by a command from the antilock braking force control circuit 60. The antilock braking force control circuit 60 includes:
A vehicle speed sensor 61 for detecting the traveling speed of the vehicle, an acceleration sensor 62 for detecting the acceleration of the vehicle, wheel speed sensors 63 to 66 for detecting the wheel speed of each wheel, and a brake pedal 1
And a brake switch 67 that switches from off to on when is depressed.

It is not necessary to provide the vehicle speed sensor 61 independently. Instead of providing the vehicle speed sensor 61, the vehicle speed may be estimated from the wheel speed of each wheel detected from the wheel speed sensors 63 to 66. good. Therefore, when the brake switch 67 is turned on, the anti-lock braking force control circuit 60 determines whether or not the pressure-increasing hydraulic pressure switching valve 12 is based on the signals output from the vehicle speed sensor 61, the acceleration sensor 62, and the wheel speed sensors 63 to 66. To 15 and hydraulic pressure switching valve 16 for pressure reduction
The switching control is performed to adjust the brake pressure on each wheel so that each wheel is not locked while the vehicle is running.

Here, during cornering, the load acting on each wheel changes inside and outside the cornering. Generally, the load on the turning inner wheel is reduced by the lateral acceleration, and the load on the turning outer wheel is increased. Therefore, if the same braking force is applied to each wheel during turning braking, the turning inner wheel may be locked before the turning outer wheel, and the running state of the vehicle may become unstable.

When the road surface friction coefficient (μ _a ) on which the turning outer wheel travels is smaller than the road surface friction coefficient (μ _b ) on which the turning inner wheel travels (μ _a <μ _b ), if the braking is performed during the turning braking. When the same braking force is applied to each wheel,
Over-steer occurs due to the moment in the turning direction,
As a result, the running state may become unstable.

ROM of antilock braking force control circuit 60
(Not shown) stores a braking force control program for controlling the braking force applied to each wheel so that each wheel has the same slip ratio during turning braking. The braking force control mode can be classified into three patterns: a pressure increasing mode, a holding mode, and a pressure reducing mode.

First, in the pressure increasing mode, the pressure increasing liquid pressure switching valves 12 to 15 and the pressure decreasing liquid pressure switching valves 16 to 19 are not controlled, and the brake pressure from the master cylinder 3 is increased. The pressure is directly supplied to the wheel cylinders 6 to 9 via the pressure switching valves 12 to 15. In the holding mode, the solenoids 12b to 15b of the pressure-increasing hydraulic pressure switching valves 12 to 15 are excited, and the valve bodies 12a to 15a are switched to the valve closing positions.
Thereby, the brake pressure to the wheel cylinders 6 to 9 is maintained.

Further, in the case of the pressure reducing mode, the braking force is weakened by controlling the pressure increasing liquid pressure switching valves 12 to 15 and the pressure decreasing liquid pressure switching valves 16 to 19. That is, immediately before the wheels are locked, the solenoids 12b to 15b of the pressure-increasing hydraulic pressure switching valves 12 to 15 are excited, the valve bodies 12a to 15a are switched to the valve closing positions, and the pressure-reducing hydraulic pressure switching valves 16 to 19 are switched. Solenoid 16
When the valves b to 19b are excited, the valve bodies 16a to 19a are switched to the valve opening positions, and the brake pressure to the wheel cylinders 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 and performs 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 and 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 speed V _B may be calculated using the wheel speed V _WI of each wheel as is known. Further, in S1, when the brake switch 67 is off, there is no need to perform the braking force control, so that the series of braking force control processing ends without performing the following processing.

In the next S3, it is checked whether or not the lateral acceleration Gy is positive.
Is positive (Gy> 0), it is determined that the traveling road is curved to the right, the process proceeds to S4, and the left wheel is set to the outer wheel. However, when 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).

If the lateral acceleration Gy is negative (Gy <0) in S5, it is determined that the traveling road is curved to the left, and the flow advances to S6 to set the right wheel to the outer wheel side. I 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 forces of the left and right wheels, the process proceeds to S7, and 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 the vehicle speed, Gy is the lateral acceleration, and V _WO Is the turning outer wheel speed, and d is the tread. Therefore, an optimum value for the target turning inside wheel speed V _WI * is calculated according to the vehicle speed V _B , the lateral acceleration Gy, and the turning outside wheel speed V _WO .

In the next S9, the wheel speed sensors 63 to 66
Turning inside wheel speed V _WIIs given by equation (1)
Obtained target turning inside wheel speed V_WI* Smaller
Check if In this S9, the turning inner wheel
Speed V_WIIs the target turning inside wheel speed V_WI* If smaller than
The wheel speed V inside the turn_WIIs slow, so proceed to S10
Only, reduce the brake pressure on the inner wheel. That is, hydraulic pressure for pressure increase
Closing the inner ring side switching valve among the switching valves 12 to 15, and
Open the switching valve on the inner ring side of the pressure reducing switching valves 16 to 19
Let it go.

However, if the turning inside wheel speed V _WI is not smaller than the target turning inside wheel speed V _WI * in S 9, the process proceeds to S 11, where the turning inside wheel speed V _WI becomes smaller than the target turning inside wheel speed V _WI *. Check if it is big. Therefore, in S11, when the turning inside wheel speed _VWI is higher than the target turning inside wheel speed _VWI *, the turning inside wheel speed _VWI is high, so the process proceeds to S12, and the brake pressure of the inner wheel is increased. That is, the pressure-increasing hydraulic pressure switching valves 12-1
5, the switching valve on the inner wheel side is opened, and the switching valve on the inner wheel side among the pressure reducing hydraulic pressure switching valves 16 to 19 is closed.

In step S11, the turning inner wheel speed V
_{If WI} is not greater than the target turning inner wheel speed V _WI *, then V _WI = V _WI *, so the flow proceeds to S13 to maintain the brake pressure of the inner wheel. That is, the pressure-increasing hydraulic pressure switching valves 12 to
The switching valve on the inner wheel side of the valves 15 is closed, and the switching valve on the inner wheel 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 to 15 and hydraulic pressure switching valve 16 for pressure reduction
19 is controlled to open and close, and the brake pressure on the inner wheel side is switched to one of pressure increase, hold, and pressure reduction, and the braking force is controlled so that the turning inner wheel and the turning outer wheel have the same slip ratio.

Accordingly, by controlling the brake pressure so that the slip ratio of each wheel becomes the same, the yaw moment which is likely to be generated at the time of turning braking can be canceled and the running stability at the time of turning braking can be improved. The braking performance can be further improved, and the braking distance can be shortened.

Here, the derivation of the above equation (1) will be described. If the left wheel is the inner ring, the right wheel is an outer ring, the vehicle speed V _B and the wheel speed of each wheel while the vehicle is running is shown in FIGS. And the front inner wheel speed V _wfi
And the rear inner wheel speed V _wri , can be expressed as follows:

_Front inner wheel speed V _wfi = (V _B −d · Gy / 2V _B ) / (V _B + d · Gy / 2V _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) The brake pressure is controlled so that the above (2) and (3) are satisfied.

Here, assuming that 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 / cosβ) 2 / R}} } · cosβ · 1 / V B = Gy / V B ... (4) Next, when the rotation yaw rate of the vehicle and _{Sz, Sz = (V BfO -V} BfI) / d = ( V _BrO −V _BrI ) / d (5) Here, when the side slip 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 ... is (6). Also, 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) Furthermore, where When the slip ratios of the front inner and outer _wheels are equal, ( _{VBfO cos} δ−V _wfO ) / V _BfO cos δ = (V _BfI cos δ−V _wfI ) / V _BfI (9) Here, δ is the front wheel tire angle.

V _wfI = (V _BfI / V _BfO ) · V _wfO (10) By substituting the above equations (7) and (8) into the 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. The overall configuration of the braking force control device is the same as that of the first embodiment, and a description thereof will be omitted. In FIG. 5, the processes in S21 to S27 are the same as those in S1 to S7 in FIG. 2 described above, and a description thereof will be omitted. 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 the lateral acceleration and V _WO is the turning outer wheel speed. Therefore, an optimal value is calculated for the target turning inside wheel speed V _WI * according to the lateral acceleration Gy and the turning outside wheel speed V _WO .

The processing in S29 to S33 is the same as that in S9 to S13 in FIG. 2 described above, and a description thereof will be omitted. Thus, the turning inner wheel speed V _WI is equal to the lateral acceleration G.
y, the opening and closing of the pressure-increasing hydraulic 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 inner wheel speed V _WI * obtained according to the turning outer wheel speed V _WO *. Then, the brake pressure to the inner wheel is switched to any one of increasing, holding, and reducing the pressure, and the braking force is controlled so that the turning inner wheel and the turning outer wheel have the same slip ratio.

Accordingly, by controlling the brake pressure so that the slip ratio of each wheel becomes the same, the control of each wheel 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. By controlling the power, the inner wheel side and the outer wheel side during turning braking can be locked simultaneously. Therefore, the running stability during turning braking can be improved by canceling the yaw moment that tends to occur during turning braking,
The braking performance can be further improved, and the braking distance can be shortened.

Here, the derivation of the above equation (11) will be described. The above equation (11) can be expressed as follows. _{^{V WO 2 -V WI 2 = 2dGy}} ... (12) Then, when considered in front of the left and right wheels, the front inner and outer wheel speed difference is expressed by the following equation. _{V WO -V WI = (1-} S fO) V BfO · cosδ- (1-S fI) V BfI · cosδ = (V BfO -V BfI) · cosδ- (S fO · V BfO -S fI · V BfI ) · cos [delta] ... (13) here, considering the control to zero (13) of the right side slip amount difference of the front left and right wheels of the second term _{(S fO · V BfO -S fI} · V BfI), V _WO− V _WI = (V _BfO −V _BfI ) · cos δ (14), cos δ ≒ 1, and V _WfO −V _WfI = dGy / V _B (15) from the above equation (6). Here, _assuming that V _B = (V _WfO + V _WfI ) / 2, V _WfO ² −V _WfI ² = 2dGy (16) similar to the above equation (12) is obtained. In the same manner as above, the following equation is obtained for the rear wheel side.

V _WrO ² −V _WrI ² = ² dGy (17) Next, referring to FIG. 6, the antilock braking force control circuit 60
A description will be given of the braking force control process of the third embodiment executed by the third embodiment. The overall configuration of the braking force control device is the same as that of the first embodiment, and a description thereof will be omitted.

In FIG. 6, when the brake switch 67 is turned on in S41, the process proceeds to S42, where the wheel speed sensor 63
Wheel speed V _WI ( _I = F)
L, FR, RL, RR). In S41, when the brake switch 67 is turned off, there is no need to perform the braking force control, so that the series of braking force control processing ends without performing the following processing.

In the next S43, it is checked whether the left wheel speed VWL is higher than the right wheel speed VWR, and the left wheel speed VWL is higher than the right wheel speed VWR (VWL>
(VWR), it is determined that the traveling road is curved rightward, and the process proceeds to S44, where the left wheel is set to the outer wheel side. However, if 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 lower than the right wheel speed VWR (VWL <VWR).

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

[0088] In the next S48, the wheel speed difference between the inner ring and the outer ring to check whether or not a predetermined value K greater than the value _{^{(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 There is no need to individually control the power, and a series of braking force control processes ends.

[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 K), the process proceeds to S49. In the next S49, the target turning inner wheel speed V _WI * is calculated by the following equation (18). ^{_{V WI * = (V WO 2}} -K) 1/2 ... (18) However, V _WO turning outer wheel speed, K is a coefficient determined by the vehicle speed.

The processes in S50 to S54 are the same as those in S9 to S13 in FIG. 2 described above, and a description thereof will be omitted. Thus, the turning inner wheel speed V _WI is the target turning inner wheel speed V _WI determined in accordance with the turning outer wheel speed V _WO
The opening / closing of the pressure-increasing hydraulic pressure switching valves 12 to 15 and the pressure-reducing hydraulic pressure switching valves 16 to 19 is controlled so as to be equal to *, and the brake pressure to the inner wheel side is switched to any one of pressure increase, hold, and pressure reduction, 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 ratio of each wheel becomes the same, the control of each wheel is performed so that the deviation of the slip ratio between the inner wheel side and the outer wheel side during turning braking becomes zero. By controlling the power, the inner wheel side and the outer wheel side during turning braking can be locked simultaneously. Therefore, the running stability during turning braking can be improved by canceling the yaw moment that tends to occur during turning braking,
The braking performance can be further improved, and the braking distance can be shortened.

Further, in this embodiment, the target turning inside wheel speed V _WI * can be obtained irrespective of the lateral acceleration Gy, so that it can be applied also as backup control when the acceleration sensor 62 fails. Here, the derivation of the above equation (18) will be described.

[0093] In this embodiment, the pressure reduction control the brake pressure of the inner side so that the _{^{V WO 2 -V WI 2 = K}} . for that reason,
When considering the front left and right wheels, _setting V _wfo ² −V _wfi ² = K results in V _wfo −V _wfi = K / 2V _B , and furthermore, (d · Gy / V _B ) − (S _fO・ V _BfO −S _fI・ V _BfI )
= K / 2V _B , so that 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 ring is set to the value of the inner ring. (D · Gy-K / 2) /
Inner and outer wheels is increased by V _B is controlled to simultaneously locked.

The brake pressure on the inner wheel is also controlled for the rear wheel in the same manner as in the above equation (19). Next, referring to FIG. 7, a fourth control executed by the antilock braking force control circuit 60 will be described.
A braking force control process according to the embodiment will be described.

In FIG. 7, when the brake switch 67 is off at the time of non-braking in S71, the process proceeds to S72. In addition, in S71, during braking when the brake switch 67 is ON, S
Proceeding to 67, normal antilock braking force control is performed. The following processes of S62 to S67 are performed in S1 to S7 of FIG.
Therefore, the description is omitted.

In 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 the vehicle speed, Gy is the lateral acceleration, and V _WI Is a turning inside wheel speed, and d is a tread. Therefore, as the target turning inside wheel speed V _WI *, an optimum value is calculated according to the vehicle body speed V _B , the lateral acceleration Gy, and the turning inside wheel speed V _WI .

In the next S69, the wheel speed sensors 63-66
It is checked whether the turning outer wheel speed V _WO detected by the above is lower than the target turning outer wheel speed V _WO * obtained by the equation (20). In this S69, if the turning outer wheel speed _VWO is smaller than the target turning outer wheel speed _VWO *, the turning outer wheel speed _VWO is slow, and thus S70.
To reduce the brake pressure of the outer wheel. That is, the switching valve on the outer ring side of the pressure increasing hydraulic pressure switching valves 12 to 15 is closed,
The switching valve on the outer ring side among the pressure-reducing hydraulic switching valves 16 to 19 is opened.

However, if the turning outer wheel speed V _WO is not smaller than the target turning outer wheel speed V _WO * in S69, the process proceeds to S71, where the turning outer wheel speed V _WO is lower than the target turning outer wheel speed V _WO *. Check if it is big. Therefore, in S71, when the turning outer wheel speed _VWO is higher than the target turning outer wheel speed _VWO *, the turning outer wheel speed _VWO is high, so the process proceeds to S72, and the brake pressure of the outer wheel is increased. That is, since the rotation is not braking, the rotation speeds of the pumps 54 and 55 are increased, and the switching valve on the outer ring side among the pressure-increasing hydraulic pressure switching valves 12 to 15 is opened.
Further, the switching valve on the outer ring side among the pressure reducing hydraulic pressure switching valves 16 to 19 is closed. As a result, the braking force of the outer wheel is increased, and the braking force is controlled such that the turning outer wheel and the turning inner wheel have the same slip ratio.

In S71, the turning outer wheel speed V
_{When WO} is not greater than the target turning outer wheel speed _VWO *, _VWO = _VWO *, and the process proceeds to S73 to maintain the brake pressure of the outer wheel. That is, the pressure-increasing hydraulic pressure switching valves 12 to
In FIG. 15, the switching valve on the outer ring side is closed, and the switching valve on the outer ring side among the pressure reducing hydraulic pressure switching valves 16 to 19 is also closed.

[0102] Thus, turning non-braking, the turning outer wheel speed V _WO vehicle body speed V _B, the lateral acceleration Gy, to be equal to the target turning outer wheel speed V _WO * corresponding to the turning inner wheel speed V _WI The hydraulic pressure switching valves 12 to 15 for pressure increase and the liquid pressure switching valves 16 to 19 for pressure reduction are controlled to open and close, and the brake pressure to the outer wheel is switched to one of pressure increase, hold, and pressure reduction. Are controlled so as to have the same slip ratio.

That is, when turning is not braked as described above, the target turning outer wheel speed V _WO * for generating an anti-spin moment based on the vehicle body speed V _B , the lateral acceleration Gy, and the turning inner wheel speed V _WI is _calculated . Calculate the turning outer wheel speed V _WO
By applying a braking force to the outer wheels such that the vehicle reaches the target turning outer wheel speed V _WO *, an optimum anti-spin moment can be generated when turning is not braked, thereby maintaining running stability.

Therefore, when turning is not braked, the yaw moment during turning is not braked by increasing the brake pressure to the outer wheel and controlling the brake pressure so that the slip ratio of each wheel becomes the same. It is possible to improve the running stability when the vehicle is not braking by turning. Since the derivation of the above equation (20) can be performed in the same manner as in the case of the above-described first embodiment, the description thereof 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. 8, the processes in S81 to S87 are the same as those in S61 to S67 in FIG.

At S88, the target turning outer wheel speed V _WO *
Is calculated from the following equation (21). V _WO * = (V _WI ² +2 dGy) ^1/2 (21) Then, the processing in S29 to S33 is performed in S6 of FIG.
9 to S73, the 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 decompression hydraulic switching valves 16 to
19 is controlled to open and close, and the brake pressure to the outer wheel is switched to one of pressure increase, hold, 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, when the vehicle is not turning, the brake pressure on the outer wheel is increased to control the brake pressure so that the slip ratio of each wheel becomes the same. 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 during turning braking can be locked simultaneously. Therefore, the running stability at the time of turning braking can be improved by canceling the yaw moment when the turning is not braked.

Since the derivation of the above equation (21) can be performed in the same manner as in the case of the above-described second embodiment, the description is omitted here. Next, a braking force control process of a 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 set in S101.
When the vehicle is not braked and is off, the process proceeds to S102. Also, S10
In step 1, when the brake is in the ON state of the brake switch 67, the process proceeds to step S107, and normal antilock braking force control is performed. The next processing of S102 to S108 is the same as that of FIG.
The description is omitted because it is the same as S42 to S48.

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

The processing in S110 to S114 is the same as that in S89 to S93 in FIG. 8 described above, and a description thereof will be 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 pressure-reducing fluid pressure switching valves 16 to 19 are controlled to open or close to switch the brake pressure to the outer wheel to one of pressure increase, hold, and pressure reduction so that the turning outer wheel and the turning inner wheel have the same slip ratio. The braking force is controlled.

Therefore, when the vehicle is not turning, the brake pressure is controlled to increase the brake pressure on the outer wheels so that the slip ratio of each wheel becomes 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, the inner wheel side and the outer wheel side during turning braking can be locked simultaneously. Therefore,
By canceling the yaw moment that is likely to be generated at the time of turning braking, the running stability at the time of turning braking can be improved, the braking performance can be further improved, and the braking distance can be shortened.

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

The process shown in FIG. 10 is executed when the vehicle speed exceeds 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 of} each wheel detected by the wheel speed sensors 63 to 66 ( _I = FL, FR, R
L, RR).

In the next S122, the wheel speed sensors 63-6
6 is determined. That is, when one of the wheel speeds of the wheels detected by the wheel speed sensors 63 to 66 is an abnormally large value or an abnormally small value compared to the other wheel speeds, the wheel speed is determined. It is determined that the sensors 63 to 66 are abnormal. In this case, since the braking force control cannot be performed for each wheel, the process proceeds to S123, where the braking force control during turning is stopped, and a display indicating that the control has been stopped and that the wheel speed sensors 63 to 66 are abnormal (see FIG. (Not shown).

At S122, the wheel speed sensor 63
When to 66 is normal, the process proceeds to S124, calculates the estimated lateral acceleration Gy * theoretical from the wheel speed V _WI. In S124, the following calculation is performed. 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 and the estimated lateral acceleration Gy * obtained by the above equation Is compared with the allowable range (± α). Then, in S126, Gy> Gy * + α or Gy <
If not Gy * -α, since the value measured by the acceleration sensor 62 is within the allowable range (± α) of the estimated lateral acceleration Gy *, the process proceeds to S127, and it is determined that the acceleration sensor 62 is normal.

In this case, the flow advances to S128, and the processing in 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 to be reduced, and the braking force is controlled so that each wheel has the same slip ratio. However, if Gy> Gy * + α or Gy <Gy * −α in S126, the value measured by the acceleration sensor 62 is out of the allowable range (± α) of the estimated lateral acceleration Gy *. Advance, acceleration sensor 62
Is determined to be abnormal. And the acceleration sensor 6
2 is indicated on a display (not shown).

Subsequently, the flow advances to S128, and as shown in FIG.
The processing of the flowchart shown is executed. That is, the acceleration cell
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 based on
Control so that each wheel has the same slip ratio
To control the braking force.

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

Here, the derivation of the above equation (23) will be described. Vehicle while steady circular turning at a speed V _B, the lateral acceleration Gy is following relationship between vehicle speed V _B and the yaw rate γ is established. Gy = V _B · γ (24) Further, the following expression is satisfied during non-braking and under general running 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). And (24) (25) (26)
_{More, Gy = V B · γ =} {(V wo + V WI) / 2} {(V wo -V WI) / d} = (V wo 2 -V WI 2) / 2d Thus, the (23) An expression 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. In the eighth embodiment, when the road surface on which the vehicle turns and turns is a so-called straddle road (the road surface on which the wheels on the outside of the turn travel is a low μ road than the inside of the turn), the rear inner wheel is a high μ road. Therefore, the braking force distribution control is not performed, and the braking force distribution control is performed because the rear outer wheel is on a low μ road. In this case, since the braking force distribution control is performed first on the rear outer wheel, the yaw rate is promoted by the braking force difference between the rear left and right wheels.

Further, when the vehicle is traveling on a straddle road as described above, if the braking force of the other wheels is to be controlled based on the front outer wheel, the front outer wheel travels on a low μ road, and the rear inner wheel becomes high. Since the vehicle is traveling 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 the present embodiment, it is determined whether or not the vehicle is traveling on a crossroad, and if the vehicle is traveling on a crossroad, the braking force of the other wheels is controlled based on the front inner wheel. In addition, the yaw rate is suppressed by controlling the brake pressure so that the braking force is reduced.

In FIG. 11, steps S141 to S147 are the same as steps S1 to S7 in FIG. 2 described above, and a description thereof will be omitted. In the next 148, the target front inner wheel speed V _WFI * is calculated by 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 the vehicle speed, Gy is the 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 speed V _B and the lateral acceleration G
y, an optimum value corresponding to the front outer wheel speed V _WFO is calculated.

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 * is equal to the front outer wheel speed V _WFO , and the target rear inner wheel speed V _{WRI is obtained.}
* Is the same as the target front inner wheel speed V _WFI * obtained by the above equation (27).

In the next S150, the rear inner wheel speed V _{WRI is determined.}
And the target rear inner wheel speed V _WRI * is calculated.
Then, the process proceeds to S151, where the difference ΔV between the rear inner wheel speed V _WRI and the target rear inner wheel speed V _WRI * (= V _WRI −V _WRI)
Check if *) is positive. This S151
Then, the rear inner wheel speed V _WRI and the target rear inner wheel speed V
_Based on the difference ΔV from _WRI *, it is determined whether or not the traveling road surface is a so-called stride road. When the road surface is not a stride road, the inner wheel side and the rear wheel side have the same μ, so that normal braking force control is performed. When riding on a steep road, reduce the brake pressure to each wheel.
Control the brake pressure according to the road.

Therefore, in step S151, ΔV ≦ 0
When 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, the process proceeds to S152, and braking force control is performed so that each wheel has the target wheel speed. . However, if ΔV> 0 in S151, the process proceeds to S153, and it is checked whether the target rear outer wheel speed V _WRO * is greater than the rear outer wheel speed V _WRO . If it is determined in step S153 that V _WRO *> V _WRO , the flow advances to step S154 to set flags F1 = 1 and F2 = 0 (decompression mode).

In S153, V _WRO * ≦ V _WRO
, The process proceeds to S155, where 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, where the flags F1 = 0 and F2 = 0.
(Pressure increase mode).

However, if it is not V _WRO * <V _WRO in S155, the process proceeds to S157, where the flags F1 = 0 and F2 = 1.
(Hold mode). In this way, the rear outer wheel flag F is determined based on the rear outer wheel speed V _WRO according to the road surface μ.
1, F2 are set. In the next S158, the above S15
4, flags F1 and F2 set in S156 and S157
It is checked whether the flag F1 = 1. If the flag F1 is not 1 in S158, S159
To check whether the target rear inner wheel speed V _WRI * is greater than the rear inner wheel speed V _WRI . If S1
If V _WRI *> V _WRI in 59, S160
To set the flag F1 = 1 (decompression mode).

At S159, V _WRI *> V _WRI
If not, the flow advances to S161 to check whether the flag F2 = 1 has been set. If the flag F2 is not set to 1 in S161, the process proceeds to S161.
Proceed to 162. In S162, it is checked whether the target rear inner wheel speed V _WRI * is lower than the rear inner wheel speed V _WRI . If it is determined in step S162 that V _WRI * <V
_If it is not _WRI , the process proceeds to S163, and the flag F2 is set to 1 (holding mode). Thus, the rear inner wheel speed V
The flag of the rear inner _wheel is set according to _WRI .

Then, in the next S164, the flag F1,
It is checked whether or not the flag F1 = 1 in F2. If one of the rear inner wheel and the rear outer wheel has the flag F1 = 1 in S164, the process proceeds to S165 to reduce the brake pressure of the left and right rear wheels. However, if the flag F1 is not 1 in S164, the process proceeds to S166, and the flag F2
Check if = 1. Then, if 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 pressure of the left and right rear wheels is held.

If the flag F2 is not 1 in S166, the process proceeds to S168, in which the brake pressures of the left and right rear wheels are increased.
That is, when the flag F1 is not 1 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 the turning braking. In this way, the rear wheels are controlled to the same wheel speed, and the turning moment 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_WFI*, For example, as shown in FIG.
Perform braking force control. Therefore, as described above, turning braking
Hour, body speed V_B, Front outer wheel speed V _WFO, Yoko
So that the left and right wheels lock simultaneously based on the speed Gy
Target inner wheel speed V_WFICalculate * and turn
When moving, the outer wheel speed V before turning_WFOTurning side based on
Outer wheel target wheel speed V_WRO* Is calculated and the front side is turned
Outer wheel speed V_WFOBased on the inner wheel after turning and after turning
Target wheel speed V of side outer wheel_WRI*, V_WRO* Is calculated.
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
Each wheel locks simultaneously by adjusting the applied brake pressure
Distribute the braking force to each wheel as follows.

Further, when it is detected that the road surface on which the outer wheel runs is a lower friction road (low μ road) than the road surface on which the inner wheel runs, the brake pressure applied to the inner wheel after turning and the outer wheel after turning is determined. 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 and pressure reducing commands and selecting the command to set the brake pressure to a lower pressure side, when the outer wheel side is a low μ road, If the brake pressure to the wheel outside the turning of the rear wheel is reduced first, a moment is generated to promote turning of the vehicle and oversteer occurs.In such a case, the rear wheel is controlled to the same wheel speed. Generation of a moment in the turning direction due to a difference in braking force between the turning inner wheel and the turning outer wheel can be prevented.

Next, a braking force control device according to a ninth 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 using the system configuration shown in FIG. The first mentioned above
In the eighth to eighth embodiments, it is determined whether or not to perform the braking force control based on whether or not the lateral acceleration Gy acting on the vehicle exceeds a predetermined threshold. The braking force control device of the present embodiment is characterized in that the threshold value used for the 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 to realize the above-mentioned function. In the map shown in FIG. 14, the vehicle speed is a predetermined value V ₀
In the following region, the threshold value for determining the start of control is the first threshold value (0.6 G in this embodiment). In the region where the vehicle 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 as to obtain a stable vehicle behavior under such a condition after the vehicle has shifted to a turning state with a high lateral acceleration Gy. If the braking force control is performed in response to the slight lateral acceleration Gy in such a low vehicle speed region, unnecessary braking force control is frequently performed, which is troublesome. From this viewpoint, 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, when the vehicle speed is fast, such as a high-speed lane change, etc., and an operation involving a temporary and sudden change in the behavior is performed, the vehicle behavior changes in order to obtain the effect of the braking force control. It is necessary to immediately start the braking force control after the start of the braking operation. Therefore, in a region where the vehicle body speed is high, it is appropriate to set the threshold value for determining control start to a relatively low value. The first threshold value (0.6 G) and the second threshold value (0.3 G) shown in FIG.
Is a value set for the purpose of satisfying such a request.

FIG. 15 is a flowchart showing an example of a routine executed by the antilock braking force control circuit 60 to switch the threshold value used for determining the start condition of the braking force distribution control according to the vehicle speed. When the routine shown in FIG. 15 is started, first, in S180, it is determined whether or not the brake switch 67 is on. 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 current routine is terminated without any further processing. On the other hand, if it is determined that the brake switch 67 is in the ON state, then in S18
1 is executed.

At S181, it is determined whether or not an operation as an anti-lock brake system (hereinafter referred to as ABS) is required. As a result, when it is determined that the operation as the ABS is required, in S182, the ABS control for realizing the operation is executed, and then the current routine is ended. On the other hand, if it is determined that the operation as the ABS has not been requested, then S
183 is executed.

[0142] In S183, based on the vehicle speed, the threshold Gy ₀ is determined for use in the determination of the starting condition of the brake force distribution control. In this routine, the threshold value Gy ₀ is
It is determined by searching the map shown in FIG. 14 based on 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.

When the above processing is completed, the process proceeds to S184.
In, in comparison with the threshold value Gy _0, the acceleration sensor 62
It is determined whether or not the absolute value | Gy | of the lateral acceleration Gy detected by the calculation is large. As a result, if Gy ₀ <| Gy | is not satisfied, it is determined that the lateral acceleration Gy that does not require the braking force distribution control is acting on the vehicle, and the current routine is ended. .

On the other hand, if it is determined that Gy ₀ <| Gy | is satisfied, 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-described processing shown in FIG. S2 to S13 shown in FIG. 2, S22 to S33 shown in FIG. 5, S42 to S54 shown in FIG.
, S62 to S73 shown in FIG. 7, S81 to S93 shown in FIG. 8, S102 to S114 shown in FIG.
Or S142 to S16 shown in FIGS.
9), the current routine ends.

According to the above-described braking force control device, the braking force distribution control is properly performed in a situation where a relatively large lateral acceleration Gy occurs during low-speed running. 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 speed.
In the above-described embodiment, the anti-lock braking force control circuit 60 executes the process of S183, thereby realizing the threshold value changing means of the ninth aspect.

Next, a braking force control apparatus according to a tenth 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 using the system configuration shown in FIG. The braking force control device of the present embodiment is characterized in that a high braking capability can be ensured 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 Ff generated by the front wheels of the vehicle (hereinafter referred to as front braking force) on the horizontal axis, and the braking force generated by the rear wheels of the vehicle (hereinafter, rear braking force) on the vertical axis. (Referred to below as Fr). FIG.
The straight line shown in the middle indicates that the friction coefficient μ between the wheel and the road surface is 1.
The front lock limit line when it is 0 is shown. During the braking operation of the vehicle, when the front braking force Ff and the rear braking force Fr become coincident with points on a straight line, the front wheels shift to the locked state at that time. Locking of the front wheel is less likely to occur as the load applied to the front wheel increases. In addition, a larger load is applied to the front wheels due to the load movement as the braking force is larger.
Therefore, the front lock limit line is a straight line ascending to the right as shown in FIG.

The straight line shown in FIG. 16 indicates the rear lock limit line when μ = 1.0. During the braking operation of the vehicle, when the front braking force Ff and the rear braking force Fr are in a state where they coincide with points on a straight line, the rear wheels shift to the locked state at that point. Locking of the rear wheel is less likely to occur as the load applied to the rear wheel increases. The load applied to the rear wheel decreases as the braking force increases, due to the movement of the load. For this reason,
As shown in FIG. 16, the rear lock limit line is a straight line falling to the right.

A straight line shown in FIG. 16 indicates an ideal braking force distribution line. During the braking operation, when the braking force corresponding to the coordinate value (Ff, Fr) on the ideal braking force distribution line is exerted on the front wheel and the rear wheel, 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. Under the influence of the load change accompanying the braking force, the ideal braking force distribution line becomes a curve as shown in FIG.

The greater the sum of the maximum value of the front braking force Ff and the maximum value of the rear braking force Fr, the better the braking capability of the vehicle. Therefore, in order to obtain a high braking ability in the vehicle, (Ff, F
It is desirable to control the distribution ratio between Ff and Fr so that the locus of r) passes through the intersection Q between 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 vehicle in which the front wheels are locked prior to the rear wheels is compared with the vehicle in which the rear wheels are locked prior to the front wheels. Behavior is stable. Therefore, in order to enhance the stability at the time of the limit, (Ff,
As the trajectory of Fr) passes through the front lock limit line,
It is desirable that the distribution ratio between Ff and Fr be controlled.

The broken line shown in FIG. 16 indicates the locus of (Ff, Fr) that can be realized by using a proportioning valve (hereinafter, referred to as a P valve). The P valve is a pressure reducing valve incorporated in a hydraulic path leading to a wheel cylinder disposed on the rear wheel. The P valve supplies the brake oil pressure supplied to the front wheel wheel cylinder to the rear wheel wheel cylinder as it is until the brake oil pressure reaches a predetermined pressure. Then, when the brake oil pressure exceeds a predetermined pressure, the P valve supplies a brake oil pressure, which is obtained by reducing the oil pressure supplied to the front wheel wheel cylinder at a predetermined ratio, to the rear wheel wheel cylinder. Therefore, the P-valve characteristic is a polygonal line as shown in FIG. The specifications of the P-valve are set so that the P-valve characteristic intersects the front lock limit line near the intersection Q between the front lock limit line and the rear lock limit line. By performing such a setting, the two requirements described above are compatible.

However, what can be controlled by the P valve is the ratio between the brake oil pressure supplied to the front wheel wheel cylinder and the brake oil pressure supplied to the rear wheel wheel cylinder. Even if the brake oil pressure ratio is the same, the relationship between the front lock limit line and the rear lock limit line and the P-valve characteristics fluctuates if the load balance fluctuates and the load balance between the front and rear wheels fluctuates. I do. For this reason, in a vehicle such as a commercial vehicle in which the load balance between the front and rear wheels greatly changes depending on the loaded state, it is difficult to always make the P valve characteristic cross the front lock limit line near the point Q.

Conventionally, a load sensing proportioning valve (hereinafter, referred to as LSPV) has been used in commercial vehicles and the like in order to compensate for such a disadvantage of the P valve. The LSPV is a P-valve having a function of changing a damping ratio of a brake oil pressure supplied to a wheel cylinder of a rear wheel according to a load of a vehicle. Specifically, when the loading load is large, the damping ratio of the brake hydraulic pressure is reduced,
In addition, when the load is small, a function is provided for largely changing the damping ratio of the brake hydraulic pressure. According to LSPV, it is possible to realize a P-valve characteristic that intersects the front lock limit line near the point Q regardless of the loaded state of the vehicle. Therefore, according to the LSPV, the braking force of the rear wheels can be more effectively exerted than the P valve.

By the way, in the system of this embodiment, the wheel speed of each wheel can be controlled by controlling the braking force. Accordingly, by controlling the braking force of each wheel, for example, the wheel speed V _{Wf of the} front wheel and the wheel speed V
_Wr can be controlled equivalently. When such control is performed during the braking operation, the trajectory of (Ff, Fr) always coincides with the ideal braking force distribution line, and the same braking force characteristics as when LSPV is used without using LSPV. Is realized. The braking force control device according to the present embodiment is characterized in that an ideal braking force distribution ratio is given to the front and rear wheels without using LSPV or the like by controlling the braking force of each wheel.

FIG. 17 shows (Ff, Fr) coordinates for explaining control characteristics realized in the control device of this embodiment. Note that, in this figure, the same reference numerals as those shown in FIG. 16 denote the same parts, and a description thereof will be omitted. As described above, the locking of the wheels during the braking operation is performed by the front braking force Ff and the rear braking force Fr.
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
No matter what process changes, no locking of the wheels will occur.

As described above, if the brake oil pressure guided to the wheel cylinder of the rear wheel is always equal to the brake oil pressure guided to the wheel cylinder of the front wheel, the rear wheel is locked due to the load movement that occurs during the braking operation. It is 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 oil pressure to the wheel cylinders of the rear wheels. Further, in order to increase the braking capacity of the vehicle, that is, to obtain a large braking force with respect to the unit brake depression force, it is appropriate to supply a high brake oil pressure to the wheel cylinders of the rear wheels. From this viewpoint, in a region where the rear wheel does not shift to the locked state, the brake oil pressure supplied to the wheel cylinder of the rear wheel is not significantly reduced in pressure as compared with the brake oil pressure supplied to the wheel cylinder of the front wheel. It is desirable.

Therefore, in the present embodiment, between the rear wheel speed V _Wr and the front wheel speed V _Wf , V _Wr = K ·
A control curve that satisfies the relationship V _Wf (K <1) is set, and the braking force of each wheel is controlled so that the control characteristics do 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 capability of the rear wheels is effectively increased. It can be used.

FIG. 18 is a flowchart 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. 18 is started, first in S190, the wheel speed sensor 63
The wheel speeds of the respective wheels detected by .about.66 are read.

Next, in S191, the acceleration sensor 6
2, the lateral acceleration Gy detected is read. When
At this time, as shown in the above equation (12), the wheel speed of the turning inner wheel is obtained.
Degree V _WI, The wheel speed V of the turning outer wheel_WO, And lateral acceleration Gy
Contains "V_WO ^Two-V_WI ^Two= 2dGy "(d; vehicle
Red). This relationship is based on the wheel
If the lip rate is not large, that is, the vehicle is in the braking state
If not, it holds with high accuracy. Therefore, beside
The acceleration Gy does not always need to be measured,
V detected at_WO, And V_WI ^TwoTo "Gy = (V_WO ^Two−
V_WI ^Two) / 2d "
It is also possible.

After the above processing is completed, it is next determined in S192 whether or not the brake switch 67 is on. As a result, if 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 current routine ends. on the other hand,
If it is determined that the brake switch 67 is on, in S193, the absolute value | Gy of the lateral acceleration Gy
Is determined whether or not | is smaller than a predetermined threshold value α.

In S193, when it is determined that | Gy | <α is satisfied, it is determined that the vehicle is in a straight-ahead state, and the processes in and after S194 are 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) 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 and} V _Wfl of the front left and right wheels are calculated as the target wheel speeds V _Wrr ^* _and V _Wrl ^* of the left and right rear wheels.

After the calculation of the target wheel speeds V _Wrr ^* _and V _Wrl ^* is completed, in S195, the wheel speeds V _{Wrr and} V _Wrl of the left and right rear wheels are respectively changed to the target wheel speeds V _Wrr ^* _and V _Wrr ^* _.
V _{Wr l} ^* whether the difference is less than or not. As a result, V
_Wrr <V _wrr ^*, and, V _{Wr l} <V _Wrl ^* are both satisfied, i.e., the left and right rear wheel speeds V _Wrr, V
_Wrl is their target wheel speed V _Wrr ^* _, V _Wrl ^*
When it is determined that the above is the case, it is determined that there is no need to reduce the braking force of the left and right rear wheels, and the current routine is terminated without performing the braking force distribution control. in this case,
Brake hydraulic pressure equivalent to that of the front wheel wheel cylinder is guided to the rear wheel wheel cylinder.

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

When the braking force distribution control is started as described above, thereafter, the brake oil pressure of the rear wheel wheel cylinder becomes lower than the brake oil pressure of the front wheel wheel cylinder. When the above-described braking force distribution control is executed after the vehicle has shifted to the braking state, the wheel speed V
_{Although the Wfr and VWfl tend} to decrease, the rear wheel speeds _{VWrr and VWrl} are appropriately set to the target wheel speeds _VWrr ^* _{and VWrl} ^* , that is, the front wheel speed _VWrr ^* .
_The predetermined wheel speed is maintained slightly smaller than _{Wfr and VWfl} . According to this processing, when a braking operation is performed in a straight traveling state, the braking ability of the rear wheels can be effectively used.

Next, the case where it is determined in step 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 process of S198 is executed. The acceleration sensor 62 used in the system of the present embodiment generates a positive output when the vehicle is turning clockwise, while
Generates 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 specify 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 in the clockwise direction. 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 turning inner wheel, ie, the right front wheel, is calculated based on the front turning outer wheel, ie, the left front wheel speed V _Wfr .

Similar to the system of the above-described second embodiment, the system of the present embodiment is configured such that when the vehicle is in a turning braking state, the front wheels are turned so that the slip ratios of the turning inner wheel and the turning outer wheel are equal. It has a function to control the braking force of the vehicle. At this time, the wheel speed of the turning inner wheel of the front wheel is equal to the above (1).
The target wheel speed V _WI ^* = √ (V _WO ²
-2d · Gy). For this reason, the aforementioned S2
At 00, the right front wheel speed V _Wfr 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, the current routine ends. In this case, the wheel speed V _Wrr of the right rear wheel serving as the turning inner wheel of the rear wheel is controlled to the target wheel speed V _Wrr ^* represented by the following equation.

V _Wrr ^* = K · √ (V _Wfl ² −2d · Gy) (31) On the other hand, if it is determined in S198 that Gy ≧ α is not established, the vehicle rotates counterclockwise. It is determined that the vehicle is turning in the direction. In this case, first, in S201, the right and left front wheels are determined as turning outer wheels. Next, at S202, the turning outer wheel of the front wheel, ie, the wheel speed V of the right front wheel.
Based on _Wfl , a wheel speed V _{Wfr of the} front turning inner wheel, that is, the left front wheel is calculated. At this time, the wheel speed V _Wfr of the left front wheel is calculated by the following equation using the relationship of the above 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, the current routine ends. In this case, the wheel speed V _Wrl of the left rear wheel, which is the turning inner wheel of the rear wheel, is controlled to the target wheel speed V _Wrl ^* shown in 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 turn, the front wheel turns with the turning outer wheel. It is possible to control the inner wheel to the same slip state, and to control the rear turning outer wheel and the turning inner wheel to the same slip state, respectively. Can have a large slip ratio. When such braking force distribution is performed, the braking performance of the rear wheels can be effectively utilized while maintaining the turning behavior of the vehicle stably.

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

In the above-described embodiment, the first target wheel speed setting means according to the tenth aspect is realized by the antilock braking force control circuit 60 executing the process of S194. . Next, a braking force control apparatus according to an eleventh embodiment of the present invention will be described with reference to FIGS. The braking force control device of the present embodiment is an embodiment in which the braking force control device of the tenth embodiment is improved.

As described above, in the limit region where the wheels shift to the locked state due to the braking operation, shifting the front wheels to the locked state prior to the rear wheels is preferable when the rear wheels shift to the locked state prior to the front wheels. The vehicle behavior can be more stably maintained as compared with. On the other hand, when the target wheel speeds V _Wrr ^* _and V _Wrl ^* of the rear wheels are set slightly smaller than the wheel speeds V _{Wfr and} V _Wfl of the front wheels as in the tenth embodiment, Prior to the front wheels, the rear wheels shift to the locked state. In this regard, 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 challenge is that there is no possibility that the rear wheel will shift to the locked state.
In the range, the target wheel speed V of the rear wheel_Wrr ^* _,V_Wrl ^*Before
Wheel speed V of the wheel_Wfr,V_WflSet slightly smaller than
And the rear wheel may shift to the locked state.
In the range, the target wheel speed V of the rear wheel_Wrr ^* _,V_Wrl ^*Before
Wheel speed V of the wheel_Wfr,V_WflTo a value slightly larger than
This can be solved by switching. Of this embodiment
The braking force control device calculates the target wheel speed V_Wrr ^* _,V
_Wrl ^*The feature is that the switching is performed.

FIG. 19 shows an example of the control apparatus according to this embodiment.
(Ff, Fr) for explaining the control characteristics to be expressed
Indicates a mark. Incidentally, in the same figure, the diagram shown in FIG.
The same reference numerals are used for the same diagrams as
Is omitted. The curve shown in FIG. 19 is the rear wheel speed.
V_WrAnd the front wheel speed V_WfV during_Wr= K_Two・ V_Wf;
(K_Two> 1) The gauge of (Ff, Fr) that establishes the relationship
It is a trace. The curve is drawn below the ideal braking force distribution line
Crosses the front lock limit line
You. Therefore, the rear wheel speed V_WrAnd the front wheel speed V
_WfAnd V_Wr= K_Two・ V_Wf; (K_Two> 1) full relationship
If the braking forces on the front and rear wheels are controlled as
Can be generated at the front wheels prior to the rear wheels.
Wear.

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

FIG. 20 shows a flowchart of an example of a subroutine executed by the antilock braking force control circuit 60 to realize the above function. In the present embodiment, if it is determined in step S192 that the brake switch is on in the routine shown in FIG. 18, the antilock braking force control circuit 60 executes the subroutine shown in FIG. The processing after S193 shown in FIG.

When the subroutine shown in FIG. 20 is started, first, in S210, an average value (hereinafter, referred to as a front wheel slip rate) Sf of the left and right front wheel slip rates is calculated. The slip ratio Sfr of the right front wheel and the slip ratio Sfl of the left front wheel are calculated using the vehicle 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 as follows. You.

Sfr = (V _B −V _Wfr ) / V _B (34) Sfl = (V _B −V _Wfl ) / V _B (35) Further, the front wheel slip ratio Sf is calculated by using these Sfr and Sf
By averaging l, calculation is performed as in the following equation.

Sf = (Sfr + Sfl) / 2 (36) The locking of the wheel is caused by the slip rate exceeding a predetermined limit slip rate determined by the ability of the tire or the like. Therefore, in a region where the value of the front wheel slip ratio Sf is sufficiently small, it can be determined that there is no possibility that the wheels shift to the locked state. Then, it can be determined that the greater the front wheel slip ratio Sf is, the greater the possibility that the wheel is shifted to the locked state is.

In this routine, in S210, the previous
After the wheel slip ratio Sf has been calculated, in S211 the front wheel slip ratio Sf is calculated.
The lip ratio Sf is a predetermined threshold value S₀Whether or not
Is determined. As a result, Sf> S₀Where is not established
If there is no possibility that the wheels will shift to the locked state
In S212, K is set to K₁After (<1) is substituted,
This routine ends. On the other hand, Sf> S₀Is established
If so, the wheels shift to the locked state
It is determined that there is a possibility, and K is set to K in S213. _Two(>
After substituting 1), the current routine ends.

Thereafter, using K set as described above,
The processing after S193 shown in FIG. 18 is executed. According to this processing, the braking capability of the rear wheel is effectively used in a region where the rear wheel is not likely to be locked afterward, and when the wheel locks, the front wheel must be moved to the front wheel before the rear wheel. Locks 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 a stable vehicle behavior near the limit region in the braking state.

In the above-described 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 can determine the value of K = K set in S213. The above S using K ₂
194. The second target wheel speed setting means according to claim 11 executes the processing in step S211.
By executing the above processing, the target wheel speed switching means according to claim 11 is realized.

In the above-described eleventh embodiment, it is determined whether or not the wheels may 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 made 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 according to the present embodiment can be realized 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 to match ^* , braking force distribution control for the turning outer wheel and the turning inner wheel is realized.

[0189] or when the vehicle is running on a paved road, because the wheel speed V _WO turning outer wheel is stable, executing a braking force distribution control as described above, turning inner slip ratio and , And the slip ratio of the turning outer wheel can be accurately matched. However, for example, such as when the vehicle is traveling on a rough road, the wheel speed at a high frequency, in a situation that varies greatly, due to the wheel speed V _WO turning outer wheel is changed, turning inner wheel speed V The deviation between _WI and its target wheel speed V _WI ^* may fluctuate greatly.

FIG. 21 shows a state where the vehicle is traveling on a rough road.
Calculated target wheel speed V of the turning inner wheel_WI ^*And such a state
Wheel speed V of the turning inner wheel actually measured under the conditions_WIDeviation ΔV from
= V _WI-V_WI ^*FIG. As shown in FIG.
In a situation where the deviation ΔV changes greatly at a high frequency,
By executing the braking force distribution control, the slip of the inner
It is difficult to match the slip rate of the turning outer wheel with the slip rate
It is. In such a situation, the braking force distribution control continues.
If this occurs, hunting will occur in the control and braking of the inner wheel turning
Improperly controlled forces can occur. Because of this,
Under such circumstances, without intentionally executing the braking force distribution control,
It is appropriate to generate a normal braking force on the turning inner wheel.
You.

The braking force control device according to this embodiment operates for a predetermined time T
Between ₁ counts the number of times the ΔV varies significantly, when a significant change beyond a predetermined number of times has occurred, it is determined that the wheel speed is unstable, the execution of the braking force distribution control The feature is that it has a prohibition function.

FIG. 22 is a flowchart showing an example of a control routine executed by the antilock braking force control circuit 60 to realize the above functions. In FIG. 22, steps that are the same as the steps shown in FIG. 18 are given the same reference numerals in parentheses, and description thereof will be simplified.

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. Next, in S222,
It is determined whether or not the brake switch 67 is on.

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

At S224, the target wheel speed V of the turning inner wheel is obtained.
_WI ^*Is calculated. In this step 224, the above-described
As in the case of the second embodiment, the turning outer wheel is
Wheel speed V_WOAnd the lateral acceleration Gy
And the target wheel speed V of the turning inner wheel _WI ^*Is calculated.

Next, at S225, a deviation ΔV = V _WI − between the wheel speed V _WI of the turning inner wheel and the target wheel speed V _WI ^*.
V _WI ^* is calculated. Further, in S226, in the past T ₁ time, [Delta] V is the number of times which is changed to a state exceeding a predetermined value K from the state for a predetermined value K is, whether or not _one or more times N is determined. During the 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 ^* frequently and
As long as there is no significant change, ΔV does not increase or decrease significantly. Above threshold K and, for a predetermined time T _1, when steady target wheel speed V _WI ^* is obtained S2
26 is not satisfied and the target wheel speed V _WI ^*
Is a value experimentally set in advance so that the condition of S226 is satisfied when the value fluctuates improperly.

Thus, when the condition of S226 is satisfied, it can be determined that the braking force distribution control should be prohibited. In this case, after S226, S227
, The braking force distribution control is prohibited, and then the current routine ends. 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 the start condition of the braking force distribution control is satisfied, that is, whether ΔV <0 is satisfied.

As a result, ΔV <0 is not satisfied, that is, the wheel speed V _WI of the turning inner wheel is reduced to the target wheel speed V _WI.
If it is determined to be larger than ^* , it is determined that it is not necessary to control the braking force of the turning inner wheel yet, and the current routine ends. On the other hand, [Delta] V <0 is satisfied, i.e., the wheel speed of the turning inner V _WI its target wheel speed V _WI ^*
If it is determined that the value is smaller than, the 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 oil pressure supplied to the wheel cylinder on the turning inner wheel side is reduced to a lower pressure than the brake oil pressure supplied to the turning outer wheel side. It is realized by doing.
Such a brake oil pressure deviation, after the braking operation is started,
This is realized by maintaining the brake path communicating with the wheel cylinder on the turning outer wheel side in the pressure increasing mode and switching the brake path communicating with the wheel cylinder on the turning inner wheel side 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 in order to gradually increase the brake pressure of the wheel cylinder on the turning inner wheel side as compared with 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 decompression mode is executed in the brake path corresponding to the turning inner wheel only when the target wheel speed V _WI ^{*, which} is significantly higher 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, a large fluctuation occurs in the target wheel speed V _WI ^* .
That is, it can be determined that the wheel speed is unduly varied.

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

[0201] Therefore, in the present embodiment, after the execution of the braking force distribution control in the above S229 is started, in S230, the predetermined number N ₂ or more times the pressure decrease mode is executed during the past predetermined time T ₂ Is determined. As a result, the number of times of the decompression mode executed within the time T ₂ is N ₂
When it is determined that the number of times 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 the current routine is ended. On the other hand, when it is determined that the number of times of the pressure reduction mode executed within the time T ₂ is N ₂ or more, it is determined that an appropriate wheel speed has not been detected, and thereafter, the above determination is made in S232, After the braking force distribution control is terminated in S233, the current routine is terminated.

As described above, according to the braking force control device of the present embodiment, it is possible to reliably prohibit the execution of the braking force distribution control when the wheel speed is unstable. Therefore,
According to the braking force control device of the present embodiment, when traveling on a rough road,
The disadvantage that the braking force of the turning inner wheel is unduly controlled can be avoided.

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 detecting means of the twelfth aspect of the present invention can be used. The braking force control prohibiting means according to the twelfth aspect is realized by executing the process of S223.

By the way, in the above-described embodiment, the predetermined time T
Number of variations of ΔV occurring within _1, and, based on the number of times of pressure reduction mode is performed in a predetermined time T _2, although the detecting the degree of instability of the wheel speeds, which are used always 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 variation width of ΔV is large, it is determined that the instability of the wheel speed is high. However, the present invention is not limited to this. A similar determination may be made based on the speed fluctuation itself. Furthermore, in the above-described embodiment, the degree of instability of the wheel speed is determined based on the number of times the decompression mode is executed. However, the present invention is not limited to this, and the decompression 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. In the braking force control device of this 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. This can be achieved by doing

If the slip ratio of the turning inner wheel and the slip ratio of the turning outer wheel are controlled equivalently by the braking force distribution control,
The braking force generated by the turning inner wheel is reduced as compared to a case where such control is not performed. The braking force generated on the turning inner wheel acts on the vehicle as a turning moment for rotating the vehicle in the turning direction. For this reason, the steering characteristic of the vehicle tends to be oversteer as the braking force generated by the turning inner wheel increases, while the steering characteristic of the vehicle tends to understeer as the braking force generated by the turning inner wheel decreases.

Therefore, if the braking force distribution control is executed when the oversteering tendency appears during the turning of the vehicle, the oversteering tendency is canceled and the steering characteristic close to the neutral steering can be obtained. .
On the other hand, if the braking force distribution control is executed while the vehicle is turning under the tendency of understeering, the understeering tendency is promoted, and the vehicle is more difficult to turn. For this reason, when the understeer characteristic appears during turning, it is appropriate not to execute the braking force distribution control.

As will be described later, whether or not the steering characteristic of the vehicle during the turn is the understeer characteristic is determined by the magnitude relationship between the actual yaw rate γ and the ideal yaw rate γ ^*, and the relationship between the actual lateral acceleration Gy and the ideal lateral acceleration Gy ^* . It can be determined based on the magnitude relationship. Where the ideal yaw rate γ
^* Is the yaw rate γ obtained when the vehicle exhibits the neutral steering characteristic, and can be obtained by a known method based on the vehicle speed and the steering angle δ. Similarly,
The ideal lateral acceleration Gy ^* is a lateral acceleration Gy obtained when the vehicle exhibits neutral steer characteristics, and can be obtained by a known method based on the vehicle body speed and the steering angle δ.

FIG. 24 determines whether the steering characteristic is an 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 ^*. FIG. 2 is a diagram illustrating an example of a technique. The characteristic value C ₁ = γ · shown in FIG.
(Γ ^* −γ) is the ideal yaw rate γ ^* and the actual yaw rate γ
Is a characteristic value obtained by multiplying the deviation from the actual yaw rate γ. In the present embodiment, the yaw rate sensor outputs different positive and negative signals corresponding to the turning direction. Similarly,
Different signs are assigned to the ideal yaw rate γ ^{* according} to the turning direction, that is, according to 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 is changed to the ideal yaw rate γ ^* . On the other hand, when the actual yaw rate γ is excessive, the value becomes negative.

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 the present embodiment, the acceleration sensor 62
Different positive and negative signals are output according to the turning direction. Similarly, different signs are given to the ideal lateral acceleration Gy ^* corresponding to the turning direction, that is, the direction of the steering angle δ. In contrast, the sign of the characteristic value C ₂ is not changed by the turning direction of the vehicle, and positive when the actual lateral acceleration Gy relative to the ideal lateral acceleration Gy ^* is insufficient, also, ideal lateral acceleration If the actual lateral acceleration Gy is excessive with respect to Gy ^* , it becomes negative.

As described above, the signs of the characteristic values C ₁ and C ₂ indicate the turning characteristics of the vehicle and the grip state in the lateral direction, respectively. Region 1 shown in FIG. 24, C ₁ <
0 and C ₂ <0. This condition is satisfied when the vehicle exhibits an oversteer tendency while ensuring a sufficient corner rig force. Therefore, the region 1 can be recognized as a region in which the vehicle has an oversteer tendency, as shown in FIG.

The area 2 shown in FIG. 24 is an area where C ₁ <0 and C ₂ > 0 are satisfied. 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 corresponds to FIG.
As shown in FIG. 5, it can be recognized as a region where the vehicle has a tendency to spin.

A region 3 shown in FIG. 24 is a region where C ₁ > 0 and C ₂ > 0 are satisfied. Such a condition is satisfied when the vehicle exhibits an understeer tendency in a state where the cornering force is insufficient. Therefore, the area 3 corresponds to FIG.
As shown in FIG. 5, the vehicle 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>
0 and an area where C ₂ > 0 holds. Such a condition is satisfied when a sufficient cornering force is secured and the vehicle shows an understeer tendency. Therefore,
The area 4 can be recognized as an area formed when the vehicle moves in the lateral direction due to disturbance or the like, as shown in FIG.

As described above, the actual yaw rate γ, the ideal yaw rate γ ^* , the actual lateral acceleration Gy, and the ideal lateral acceleration Gy ^*
, And comparing these magnitude relations, the state of the vehicle at the time of turning can be detected with high accuracy. The braking force control device of the present embodiment determines whether the vehicle has an understeer tendency by such a method, and if the vehicle has an understeer tendency, stops the execution of the braking force distribution control that promotes the tendency. It is characterized by points.

FIG. 26 shows a flowchart 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. 26 is started, first, in S240, the wheel speed, the steering angle δ, the lateral acceleration Gy, and the yaw rate γ of each wheel are read.

Next, in S241, it is determined whether or not the braking force distribution control is being executed. If the braking force distribution control has not been executed, there is no advantage in proceeding with the subsequent processing, and the current routine is immediately terminated. On the other hand, if it is determined that the braking force distribution control is being executed, the process proceeds to S2
At 42, it is determined whether or not an understeer tendency is present by the above-described method.

As a result, when it is determined that the understeer tendency does not appear, it is determined that there is no adverse effect even if the braking force distribution control is continued, and then the current routine is terminated. On the other hand, when it is determined that the understeering tendency appears in the turning behavior, the braking force distribution control ends in S243. After the braking force distribution control ends, the brake hydraulic pressure supplied to the wheel cylinder of the turning inner wheel increases, and the braking force generated by the turning inner wheel increases. As a result, the turning moment acting on the vehicle increases,
Understeer tendency is suppressed.

As described above, according to the braking force control device of the present embodiment, when an understeering tendency occurs during turning, the execution of the braking force distribution control for promoting the tendency can be stopped. Therefore, according to the braking force control device of the present embodiment, excellent steering performance can be realized without impairing the turning characteristics of the vehicle due to the execution of the braking force distribution control.

During the execution of the braking force distribution control, the brake oil pressure in the wheel cylinder on the turning inner wheel is supplied from the master cylinder in accordance with the brake oil pressure in the wheel cylinder on the turning outer wheel, that is, the brake pedal force. It is suppressed to a lower pressure than 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, a sudden increase in the brake oil pressure on the turning inner wheel side occurs. In order to stably maintain the behavior of the vehicle during turning, it is preferable to suppress such a sharp increase in the brake hydraulic pressure.

For this reason, in the present embodiment, the above S2
If the braking force distribution control is finished at 43, then, in S244, after the pressure-increasing fluid pressure changeover valve communicating with the turning inner wheel side of the wheel cylinder over a predetermined time T ₁ is is duty controlled, the routine is ended Is done.

[0223] Figure 27 is a variation of the brake pressure P _WI turning inner side implemented by braking force control apparatus of the present embodiment,
And shows a change in the turning outer wheel side brake hydraulic pressure P _WO. still,
Changes in brake hydraulic pressures P _WI and P _WO shown in FIG.
₀ braking operation is started, the started braking force distribution control at time t _1, then, the braking force distribution control is realized when it is terminated at time t _2.

[0224] Time t ₀ ~ time t ₁ of the period, the braking force distribution control is not executed, the brake hydraulic pressure P _WI of the turning inner wheel side is boosted in the same manner and the brake hydraulic pressure P _WO turning outer wheel side. The braking force distribution control at the time t ₁ is started, then, while the brake hydraulic pressure P _WO turning outer wheel side is increased similarly to the master cylinder pressure P _MC, brake oil pressure P _WI turning inner side step Shows a moderate gradual rise. Time t ₂
When the braking force distribution control is completed, the duty control of the pressure-increasing hydraulic pressure switching valve is thereafter started.
The brake hydraulic pressure P _WI on the turning inner wheel side is the master cylinder pressure P _MC
Rises slowly towards.

According to this processing, by ending the braking force distribution control, it is possible to suppress the tendency of the vehicle to understeer, and to suppress a change in behavior occurring in the vehicle when the control is ended. In addition, during turning braking, the vehicle behavior can always be stably maintained.

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

Next, a fourteenth embodiment of the present invention will be described with reference to FIGS. The braking force control device of the present embodiment has a configuration similar to the system configuration of the above-described thirteenth embodiment, that is, the anti-lock braking force control circuit 60 shown in FIG. 1 detects the steering angle δ of the steering wheel. This can be realized by connecting a steering angle sensor and a yaw rate sensor that detects the yaw rate γ of the vehicle.

The braking force control apparatus according to the present embodiment is characterized in that the understeer tendency can be more efficiently suppressed than the thirteenth embodiment. Such an effect is realized by the antilock braking force control circuit 60 executing a routine shown in FIG. 28 instead of the routine shown in FIG. In FIG. 28, steps in which the same processing as the step shown in FIG. 26 is executed include:
The same reference numerals are given and the description is omitted.

[0229] According to the routine shown in FIG. 28, appearing understeer tendency of the vehicle, after the braking force distribution control is finished in S243, in S250, for a predetermined time T _1, the turning inner wheel side brake hydraulic pressure duty control Then, after the brake hydraulic pressure on the turning outer wheel side is maintained, a series of processing is terminated.

FIG. 29 shows a case where such processing is executed.
Realized brake hydraulic pressure P on the turning inner wheel side_WIChanges, and
Brake hydraulic pressure P on the turning outer wheel_WOShows the change in FIG.
Brake oil pressure P shown in 9_WI, P_WOChanges at time t₀To
The braking operation is started at time t ₁Braking force distribution control starts
And then at time t_TwoBraking power distribution control is terminated
Is realized in the case.

[0231] Brake oil pressure P on the turning inner wheel side_WI, And whirl
Brake oil pressure P on the outer wheel_WOIs the time t₁~ T_TwoPeriod of
In the middle, the pressure is increased as in the case of the thirteenth embodiment.
You. Time t_TwoWhen the braking force distribution control ends, the
Then, the brake hydraulic pressure P on the turning inner wheel side _WIIs duty boosted
And the master cylinder pressure P_MCIs boosted
Nevertheless, the brake hydraulic pressure P on the turning outer wheel side_WOIs the time t
_TwoIs kept as it is.

The braking force generated by the turning outer wheel acts on the vehicle as a moment in a direction that prevents the vehicle from turning, that is, a moment in a direction that promotes the tendency to understeer. Therefore, the brake hydraulic pressure P on the turning outer wheel side
_WO is, and held the time t ₂ after a predetermined period of time T _1,
The growth of the moment in the direction that promotes the understeer tendency can be suppressed. 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 terminated, in combination with the increase in the braking force of the turning inner wheel.

Next, a fifteenth embodiment of the present invention will be described with reference to FIGS. The braking force control device of the present embodiment can be realized by a configuration similar to the system configuration of the above-described thirteenth and fourteenth embodiments. The braking force control device according to the present embodiment is characterized in that superior continuity can be exhibited in the process of shifting to the normal control after the braking force control is completed, as compared with the fourteenth embodiment described above. 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.
In FIG. 26, steps that are the same as the steps shown in FIG. 26 are given the same reference numerals, and descriptions 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 a case where such processing is executed.
Realized brake hydraulic pressure P on the turning inner wheel side_WIChanges, and
Brake hydraulic pressure P on the turning outer wheel_WOShows the change in FIG.
Brake oil pressure P shown in 1_WI, P_WOChanges at time t₀To
The braking operation is started at time t ₁Braking force distribution control starts
And then at time t_TwoBraking power distribution control is terminated
Is realized in the case.

The brake hydraulic pressure P on the turning inner wheel side_WI, And whirl
Brake oil pressure P on the outer wheel_WOIs the time t₁~ T_TwoPeriod of
In the middle, the pressure is increased as in the case of the fourteenth embodiment described above.
You. Time t_TwoWhen the braking force distribution control ends, the
Then, the brake hydraulic pressure P on the turning inner wheel side _WIIs duty boosted
And the brake hydraulic pressure P on the turning outer wheel side_WOWell, dew
The pressure is gradually increased by the pressure increase.

[0237] After the braking force distribution control is finished, the predetermined time T ₁ is passed, the brake path is restored to normal, the turning inner wheel side of the wheel cylinder, and the wheel cylinder of the turning outer wheel side, both the master It becomes conductive with the cylinder. To obtain good continuity in such transition period, when the time T ₁ is passed, the turning inner wheel side brake hydraulic pressure, and the turning outer wheel side brake hydraulic pressure, kept close to both the master cylinder pressure P _MC It is necessary. On the other hand, 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 as in the present embodiment, the understeer is effectively performed after the braking force distribution control is completed. It is possible to realize excellent continuity before and after the state of the brake path is switched while suppressing the tendency. Therefore, according to the braking force control device of the present embodiment, it is possible to obtain an effect that the feeling of strangeness 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. The braking force control device according to the present embodiment can be realized using the system configuration shown in FIG. The braking force control device according to the present embodiment executes the braking force distribution control for equalizing the slip ratio of the turning inner wheel and the slip ratio of the turning outer wheel. In the braking force distribution control, the target wheel speed V of the turning inner wheel is based on the wheel speed V _WO of the turning outer wheel, as in the first to fifth embodiments described above.
_This is realized by calculating _WI ^* and controlling the braking force of the turning inner wheel so that the wheel speed V _WI of the turning inner wheel matches the target wheel speed V _WI ^* .

FIG. 32 is a time chart for explaining the operation when the brake path 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. 32B 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 oil pressure is guided to the wheel cylinder on the turning outer wheel side during execution of the braking force distribution control. As shown in FIG. 32B, in the brake path communicating with the wheel cylinder on the turning inner wheel side, the brake oil pressure on the turning inner wheel side is appropriately increased as shown in FIG. 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 according to the present embodiment in the case where a failure occurs in which the brake hydraulic pressure of the wheel cylinder on the turning outer wheel 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 by the brake path communicating with the wheel cylinder on the turning inner wheel side after the braking force distribution control is started. If a failure that cannot increase the brake hydraulic pressure on the turning outer wheel side occurs in the brake path, the brake hydraulic pressure on the turning outer wheel side is not increased during the execution of the braking force distribution control. Therefore, under such circumstances, the wheel speed V _WO also the braking operation has been performed the turning outer wheel side is not decelerated. Wheel speed V on the turning outer wheel side
Assuming that _WO is not decelerated, target wheel speed V _WI ^{* of the} turning inner wheel calculated based on wheel speed V _WO is not decelerated. On the other hand, assuming that the brake path communicating with the turning inner wheel-side wheel cylinder is normal, the brake hydraulic pressure is guided to the turning inner wheel-side wheel cylinder 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 equal to the target wheel speed V _WI ^* in FIG.
As shown in FIG. ₇ , after the time t1, the decompression mode is continuously set.

As described above, if the braking force distribution control is executed when the brake path communicating with the wheel cylinder on the turning outer wheel side is faulty, the brake path communicating with the wheel cylinder on the turning inner wheel side is normal. In some cases, 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 brake devices fails, the other brake device must function effectively.
It is desirable to stop the braking force distribution control when such a failure occurs.

As described above, in the case where a failure in which the brake hydraulic pressure cannot be increased occurs 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 The brake path communicating with the wheel cylinder is continuously in the pressure reduction 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 according to the present embodiment, after the braking force distribution control is started, brake path of the turning inner wheel side, if the vacuum mode has been continued for a predetermined time T _1, to cancel the braking force distribution control And

FIG. 34 is a flowchart 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 benefit in proceeding with the subsequent processing, and this routine is immediately terminated. On the other hand, when it is determined that the braking force distribution control is being executed, the process of S261 is executed next.

In S261, the control mode of the brake path communicating with the wheel cylinder on the turning inner wheel side is monitored. In 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.

[0246] Next, in S262, the duration t of the pressure reducing mode, whether exceeds a predetermined time T ₁ is is determined. As a result, when t> T ₁ is not satisfied, it is determined that the braking force distribution control is executed successfully, S263
After the determination to continue the control is made, the current routine ends. On the other hand, in the S262, if t> T ₁ is determined to be satisfied, it is determined that the braking force distribution control is not being executed normally, the abnormality determination of the brake path is made at S264, and then the braking force distribution at S265 After the control is terminated, the current routine is terminated.

According to the above-described processing, in the case where the brake path fails and the brake hydraulic pressure on the turning outer wheel cannot be increased, the brake hydraulic pressure on the turning inner wheel can be reliably increased. Therefore, according to the braking force control device of the present embodiment, the function of executing the braking force distribution control and the fail-safe function against the failure of the brake path can be supported.

By the way, the routine shown in FIG. 34 is terminated immediately after S265 when it is determined that the brake path is abnormal, but after S265, the routine shown in FIG.
The same processing as described above, that is, control for increasing the duty of the brake hydraulic pressure on the turning inner wheel side may be executed.
When such processing is added, a change in behavior occurring in the vehicle before and after the braking force distribution control is completed can be suppressed, and good steering stability can be obtained.

In the above-described embodiment, the anti-lock braking force control circuit 60 performs the processing in S262, S264, S
By executing the process of H.265, the above-described first braking force control suspension means is realized. Next, a seventeenth embodiment of the present invention will be described with reference to FIGS. The braking force control device of the present embodiment can be realized by a configuration excluding the acceleration sensor 62 from the system configuration shown in FIG.

In FIG. 35, a curve indicated by a chain line indicates a target wheel of the turning inner wheel for making the slip rate of the turning inner wheel equal to the slip rate of the turning outer wheel when the wheel speed of the turning outer wheel is _{VWO. Shows the} speed V _WI ^* . The target wheel speed V _WI ^* is calculated as V _WI ^* = √ (V
_WO ² -2d · Gy). Therefore, FIG.
As shown in FIG. 5, the value decreases as Gy increases.

[0251] straight line shown by the solid line in FIG. 35, when the wheel speed of the turning outer wheel is V _WO, Gy predetermined value K / 2d
The target wheel speed V of the turning inner wheel for giving a larger slip ratio to the turning outer wheel in the region exceeding
Indicates _WI ^* . The target wheel speed V _WI ^* is _{calculated as} (1)
As shown in equation 8), it can be expressed as V _WI ^* = √ (V _WO ² −K). Therefore, as shown in FIG.
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 for calculating 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 ^* indicated by a straight line in FIG. 35, the lateral acceleration Gy is not used for calculating the target wheel speed V _WI ^* . For this reason, as in the third embodiment described above, the braking force control device that performs such control can be realized without using the lateral acceleration sensor 62.

In the third embodiment described above, V_WO ^Two-V_WI ^Two>
In the area where K is satisfied, the wheel speed of the inner_WI ^*=
√ (V_WO ^Two-K) so that the braking force distribution control
Execute Slip ratio of turning inner wheel and slip of turning outer wheel
If the rate is the same, V_WO ^Two-V_WI ^Two= 2dGy
(See the above equation (11)). Therefore,
In the third embodiment, the control start condition “V_WO ^Two-V_WI ^Two> K "
“2d · Gy> K”, that is, “Gy> K / 2d”
Can be approximated. Therefore, in the third embodiment described above,
According to this, in the region where Gy> K / 2d is satisfied, the braking force distribution
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 ^*
= √ be determined in accordance with (V _WO ² -2d · Gy) becomes operational expression, be determined in accordance with V _WI ^* = √ becomes (V _WO ² -K) arithmetic expression, the same calculation result as shown in FIG. 35 is obtained . At this point, the target wheel speed V _WI ^{* is given} by V _WI ^* = √ (V _WO ² −K)
The target wheel speed V _WI for making the slip ratio of the turning inner wheel equal to the slip ratio of the turning outer wheel is based on the assumption that the lateral acceleration Gy acting on the vehicle is always K / 2d. ^* (V _WI ^* shown by a curve in FIG. 35) is calculated.

In order to effectively utilize the grip performance of the turning inner wheel and the grip performance of the turning outer wheel during turning, it is appropriate to make the slip ratios of both the wheels uniform.
In the sense of satisfying such a demand, the lateral acceleration Gy is accurately detected by 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 determine in accordance with the following. Therefore, when the braking force distribution control is performed by the method of the third embodiment, a large deviation does not occur between the slip ratio of the turning inner wheel and the slip ratio of the turning outer wheel during the execution of the braking force distribution control. It is necessary.

As described above, the curve shown in FIG.
This is the target wheel speed V _WI ^* of the turning inner wheel for making the slip rate of the turning inner wheel equal to the slip rate of the turning outer wheel. Therefore, assuming that the wheel speed V _WI of the turning inner wheel at the time of braking is higher than the target wheel speed V _WI ^* , the slip ratio of the turning inner wheel becomes smaller than the slip ratio of the turning outer wheel. This means that 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.

In FIG. 36, a straight line indicated by a dashed line indicates V _WI
^{When the} braking force distribution control is executed based on the target wheel speed V _WI ^* calculated by the arithmetic expression of ^* = √ (V _WO ² −2d · Gy), the pressure reduction realized by the wheel cylinder on the turning inner wheel side 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 coordinate values of the pressure reduction control amount at each point on the straight line are referred to as ideal pressure reduction control amounts.

A straight line shown by a solid line in FIG. 36 is V _WI ^* =
制動 When the braking force distribution control is executed based on the target wheel speed V _WI ^* calculated by the equation (V _WO ² −K),
4 shows a straight line schematically representing a pressure reduction control amount realized by a wheel cylinder on the turning inner wheel side. Hereinafter, this straight line is referred to as an approximate pressure reduction control line, and the coordinate values of the pressure reduction control amount at each point on the straight line are referred to as approximate pressure reduction control amounts.

As described above, V_WI ^*= √ (V_WO ^Two-K)
Target wheel speed V obtained from_WI ^*Force distribution control using
Is executed, in the region of Gy> K / 2d,
The wheel slip rate is small compared to the slip rate of the turning outer wheel.
Is done. The situation is V_WI ^*= √ (V_WO ^Two-2dG
target wheel speed V obtained by y)_WI ^*Braking force distribution using
The inner turning wheel rotates at a higher speed than when minute control is executed.
By turning, that is, the wheel inner ring of the turning inner wheel
Is realized by giving a large amount of pressure reduction control
You. Therefore, the ideal pressure reduction control line and the approximate pressure reduction control line
36, a region of Gy> K / 2d as shown in FIG.
The ideal pressure reduction control line is located below the approximate pressure reduction control line.
Is established.

As in the third embodiment, V _WI ^* = √ (V _WO
^When executing the braking force distribution control using the target wheel speed V _WI ^* obtained by ^2- K), an unreasonably large deviation is generated between the slip ratio of the turning inner wheel and the slip ratio of the turning outer wheel. In an area where Gy> K · 2d is satisfied, it is preferable that the approximate reduced pressure control amount for Gy and the ideal reduced pressure control amount are not largely separated from each other. In order to satisfy such requirements, it is appropriate to set K / 2d to a large value.

However, in the third embodiment, the region where Gy> K / 2d is set as the execution region of the braking force distribution control. Therefore, when 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 device according to the third embodiment described above has an advantage that the system can be realized without using the acceleration sensor 62, but has an effective control while securing excellent responsiveness. There is a problem that it is difficult to perform power distribution control.

The braking force control device according to the present embodiment is characterized in that the problem of the device according to the third embodiment is solved by realizing a pressure reduction control line indicated by a solid line in FIG. . That is, in the present embodiment, the lateral acceleration Gy
There in a region exceeding a predetermined value K _1, the braking force distribution control is executed. Predetermined value K ₁ is a small constant compared to K / 2d shown in FIG 36. 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. In the present embodiment, the target wheel speed V _WI ^* is V _WI ^* = √ (V _WO
It is calculated by _² -2d · K ²⁾ comprising an arithmetic expression. 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 capable of realizing effective braking force distribution control while ensuring excellent responsiveness without using the acceleration sensor 62.

FIG. 38 is a diagram showing an example of the anti-aliasing function for realizing the above function.
One of the control routines executed by the lock braking force control circuit 60
4 shows an example flowchart. The routine of FIG. 38 is started.
First, in S270, the wheel speed of each wheel is read.
Be impregnated. Next, in S271, the lateral acceleration Gy is estimated.
Is performed. As described above, the lateral acceleration Gy depends on the turning outer wheel.
Wheel speed V_WOAnd the inner wheel speed V_WIlAnd using
Gy = (V_WO ^Two-V_WI ^Two) / 2d
(Refer to the above equation (12) and S191). In this step
Is the wheel speed V of the left and right front wheels in the above equation._Wfr,V_WflTo
By substituting, the lateral acceleration Gy is calculated.

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. Then, the wheel speed V _Wfl of the left front wheel is substituted for the wheel speed V _WO on the turning outer wheel side, and the wheel speed V _Wfr ² of the right front wheel is substituted for the wheel speed V _WI on the turning inner wheel side. The value of the lateral acceleration Gy estimated in this manner accurately matches the actual lateral acceleration Gy when the vehicle is in a non-deceleration state and the left and right front wheels have the same slip ratio.

When the estimation of the lateral acceleration Gy is completed,
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 in the ON state, the current routine is immediately terminated. On the other hand, the brake switch 67
Is determined to be in the ON state, the process of S273 is executed next.

In 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, the left front wheel is determined to be a turning outer wheel when Gy> 0 is satisfied, and the right front wheel is determined to be a turning outer wheel when Gy <0 is satisfied.

[0267] Next, in S274, the absolute value of the lateral acceleration Gy | Gy | is, whether greater than the predetermined value K _1, that is, the lateral acceleration Gy to start the braking force distribution control with respect to the vehicle It is determined whether or not is acting. as a result,
| Gy | if> K ₁ is determined to be not established, it is determined that there is no need to start the braking force distribution control, then immediately the routine is ended. On the other hand, | G
y |> if K ₁ is determined to be 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 ^*Is calculated, then
In S276, the wheel speed V of the turning inner wheel is determined._WIBut eyes
Marker wheel speed V_WI ^*It is determined whether or not it is smaller than.
As a result, V_WI<V_WI ^*Is not established,
It was determined that there was no need to reduce the wheel side brake oil pressure,
Thereafter, the current routine ends. On the other hand, V_WI<V_WI
^*If it is determined that
It is determined that it is necessary to reduce the hydraulic pressure, and control is
Power distribution control is started. Thereafter, in S278, the rotation
Wheel speed V of the pronation wheel_WIIs the target wheel speed V_WI ^*And one
After the braking force on the turning inner wheel side is controlled so that
Routines are terminated.

According to the above-described processing, after the vehicle shifts 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 device of this embodiment is K ₁
<In the region Gy ≦ K _2, it is suppressed to a small value compared to the ideal pressure reduction control amount. In this case, a large slip ratio is applied to the turning inner wheel as compared with the slip ratio of the turning outer wheel, and a state is formed in which the gripping ability of the turning inner wheel and the gripping ability of the turning outer wheel are not balanced. However, K ₁ <Gy
At the time of low lateral acceleration turning satisfying ≦ K _2, there is sufficient margin in the gripping ability of the wheel, so that 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 device of this embodiment is K ₂ <G
In the y region, the value is larger than the ideal pressure reduction control amount. In this case, as described above, a large slip ratio is provided to the turning outer wheel as compared with the slip ratio of the turning inner wheel, and a state is formed in which the gripping ability of the turning inner wheel and the turning outer wheel are not balanced. However, such imbalance in the slip ratio is effective in increasing the non-turning moment acting on the vehicle. In order to obtain a stable turning behavior when turning at a high lateral acceleration where K ₂ <Gy is satisfied, it is preferable to impart an understeer characteristic to the vehicle. In this regard, the braking force control device according to the present embodiment that easily generates a non-turning moment when turning at high lateral acceleration has an excellent effect in obtaining stable vehicle behavior during turning at high lateral acceleration. .

In the above embodiment, the anti-lock braking force control circuit 60 executes the processing of S270, so that the outer wheel speed detecting means and the inner wheel speed detecting means of the present invention are controlled by the anti-lock braking force control circuit 60. By executing the processing of S271, the lateral acceleration estimating means of claim 16 executes the processing of S274, and thereby the lateral acceleration determining means of claim 16 executes the processing of S275.
By executing the processing of the above, the target turning inner wheel speed calculating means of the present invention is realized, and by executing the processing of S277 and S278, the braking force control means of the present invention is realized. ing. Further, in the above-mentioned embodiment, the first set value predetermined value K ₁ is claim 16, wherein the predetermined value K ₂ is the first aspect
6 respectively correspond to the second set values.

Next, referring to FIG. 39, the eighteenth embodiment of the present invention will be described.
An example will be described. Braking force control device of the present embodiment
Is implemented using the system configuration shown in FIG.
Can be. In each of the above-described embodiments, the target wheel of the turning inner wheel is used.
Speed V_WI ^*And V_WI ^*= √ (V _WO ^Two-2d · Gy)
Is V_WI ^*= √ (V_WO ^Two-K)
(FIG. 5, FIG. 6, FIG. 18, FIG. 22, FIG. 38)
Etc.).

In general, a computer used in an on-vehicle electronic control unit performs an integer type operation. For example,
Data requiring less precision is 1-byte data (0
0 to FF), data requiring relatively high precision is processed as 2-byte data (0000 to FFFF) by an integer type operation.

The above-mentioned equation for calculating the target wheel speed V _WI ^* includes the square 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 needs to be 2-byte data. For this reason, the square term “V _WO ² ” is 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 a case where all data is data of 2 bytes or less. Therefore, assuming that the processing is carried out by a vehicle-mounted computer, it is desirable that the arithmetic expression does not include the square term.

Further, the calculation of the target wheel speed V _WI ^* includes the calculation of the route. In order to perform a route operation using an in-vehicle computer, it is necessary to perform a multi-stage operation combining four arithmetic operations. For this reason, in order to execute the operation including the root operation, a large memory capacity is required as compared with the case where only the four arithmetic operations are required, and a long operation time is required. You need a program. For this reason, assuming that the processing is carried out by a 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 device of this embodiment sets the target wheel speed V _WI ^* without including the square term, and
The feature is that it is approximately determined by an arithmetic expression composed of only four arithmetic operations. Hereinafter, an approximation method used in the present embodiment will be described.

The target wheel speed V _WI ^* shown in the above equation (11)
The relationship of = √ (V _WO ² -2d · Gy) can be modified as in the following equation. The ^{_{V WO 2 -V WI * 2 =}} 2d · Gy ··· (37) left by factoring, the equation (37) can be rewritten as 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 . Also, during execution of the braking force distribution control, it is considered that the wheel speed V _WI of the turning inner wheel accurately matches the target wheel speed V _WI ^* . Therefore, in the above equation (38), (V _WO + V _WI ^* ) is
(V _WO + V _WI ) = 2 · V _B can be approximated. According to such an approximation method, the above (38) can be expressed as the following equation.

V _WO −V _WI ^* = d · Gy / V _B (39) Therefore, the target wheel speed V _WI ^* does not include the square term, and is obtained by an arithmetic expression composed of only four arithmetic operations. , Can be expressed as: V _WI ^* = V _WO −d · Gy / V _B (40) The above method is an approximation method in which the wheel speed V _WI of the turning inner wheel and the target wheel speed V _WI ^* are the same. It is included. Therefore, for example, in a process in which the wheel speed _VWI changes, a deviation may occur between the two and the approximation accuracy may be degraded. However, the target wheel speed V _WI ^* is calculated by the anti-lock braking force control circuit 60 for several milliseconds.
It is executed every time. In such a short time, there is no large change in the wheel speed V _WI and the target wheel speed V _WI ^*, and therefore, an error which is a practical problem is superimposed on the target wheel speed V _WI ^* calculated by the above-described approximation method. Never. For this reason,
According to the braking force control device of the present embodiment, it is possible to realize a small-capacity memory and a high-speed processing without substantial adverse effects.

The above function is realized by the antilock braking force control circuit 60 executing a routine shown in FIG. In FIG. 39, steps that are the same as the steps shown in FIG. 5 are given the same reference numerals in parentheses, and descriptions 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. Next, S28
From the vehicle speed sensor 62 1, it is loaded vehicle speed V _B. Next, in S282, it is determined whether Gy> 0 holds. As a result, if Gy> 0 holds, S28
In S3, if the left wheel is the outer wheel, and if Gy> 0 is not established, the right wheel is the outer wheel in S284.

[0283] After the above processing is completed, the process proceeds to S285.
In the above, the target wheel speed V _WI ^{* is obtained} by using the above equation (40) ^.
= V _WO −d · Gy / V _B is calculated. This step S2
The calculation of 85 is performed by a calculation expression that does not include the square term and is composed of only simple four arithmetic operations.

After the target wheel speed V _WI ^* has been calculated, it is next determined in S 286 whether V _WI ^* > V _WI holds. As a result, when V _WI ^* > V _WI is satisfied, a process for reducing the brake hydraulic pressure of the turning inner wheel is executed in S287, and then the current routine is ended.
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, when V _WI ^* <V _WI is satisfied, a process for increasing the brake oil pressure of the turning inner wheel is executed in S289, and then the current routine is ended. Further, if it is determined in S288 that V _WI ^* <V _WI is not established, a process for maintaining the brake hydraulic pressure of the turning inner wheel is executed in S290, and then the current routine ends.

By the way, in the above-mentioned routine,
While the vehicle body speed V _B is set to be detected with the vehicle speed sensor 61, the present invention is not limited thereto.
That is, in the field of the vehicle braking force control device, a method of estimating the vehicle body speed with high accuracy based on the detection values of the wheel speed sensors 63 to 66 without using the vehicle speed sensor 61 is known. 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-described embodiment, the anti-lock braking force control circuit 60 executes the processing of S285 to implement the target turning inside wheel speed calculating means according to claim 17 of the present invention.

[0287]

As described above, according to the first aspect, the target wheel speed of the inner wheel at the time of turning is calculated based on the vehicle body speed, the turning outer wheel speed, and the lateral acceleration so that the left and right wheels are simultaneously locked. By controlling the braking force of the turning inside wheel to become the target wheel speed obtained by this calculation, the target wheel speed of the turning inside wheel according to the vehicle speed and the lateral acceleration is calculated, and this target wheel speed and The braking force of the inner wheel is controlled so that Therefore, the brake pressure is controlled so that the slip ratio of each wheel becomes the same, so that the running stability at the time of turning braking can be increased, and the braking distance that can further enhance the braking performance can be shortened.

According to the second aspect, when the target turning inside wheel speed is V _WI , the vehicle speed is V _B , the lateral acceleration is Gy, and the turning outside wheel speed is V _WO , V _WI = ｛by the following equation. _{(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 rotation of the vehicle and the yaw rate of the revolution are made to coincide with each other so that the inner wheel side and the outer wheel side at the time of turning braking are simultaneously performed. Control the braking force of each wheel to lock.

According to the third aspect, V _WI = (V _WO ² -2dGy) ^1/2 target turning inside wheel speed V _WI is calculated by the following equation to determine the difference 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 of the slip ratio becomes zero, and the inner wheel side and the outer wheel side during turning braking are locked at the same time.

[0290] Also, according to claim 4, such that V _WO ² -V _WI ² = K when it is determined that V _WO ² -V _WI ^2> K during braking revolution without detecting the lateral acceleration Gy The braking force of each wheel is controlled by controlling the braking force of the turning inner wheel and controlling 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 turning outer wheel speed becomes the target turning outer wheel speed, an optimum anti-spin moment can be generated during turning non-braking to maintain running stability.

[0292] According to the sixth aspect, when turning is not braked, V
When it is determined that _WO ² −V _WI ² > K, V _WO ² −V _WI ² = K
By applying the braking force of the turning outer wheel so as to achieve the optimum anti-spin moment when turning is not braked without detecting the lateral acceleration Gy, the running stability can be maintained.

Further, 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. Determine the presence or absence. Then, when it is determined that the lateral acceleration detecting means is abnormal, the target wheel speed of the inner wheel at the time of turning is calculated based on the turning outer wheel speed detected by the wheel speed detecting means, and the turning inner wheel speed becomes the target. By controlling the braking force of the turning inner wheel so that the target wheel speed is calculated by the turning inner wheel speed calculating means, the running stability at the time of 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 based on the vehicle speed, the front outer wheel speed and the lateral acceleration so that the left and right wheels are simultaneously locked. At the time of braking, the target wheel speed of the rear outer wheel is calculated based on the front outer wheel speed before turning, and the target wheel speed of the rear inner wheel and the rear outer wheel is calculated based on the front outer wheel speed before turning. 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. Distribute the braking force to. Further, at the time of turning, when it is detected that the road surface on which the outer wheel runs is a lower friction road (low μ road) than the road surface on which the inner wheel runs, brake pressure increase 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 pressure reducing commands and selecting the command to set the brake pressure to a lower pressure side, when the outer wheel side is a low μ road, the rear wheel If the brake pressure to the outer wheels is reduced first, a moment is generated that promotes the turning of the vehicle and oversteer occurs.In such a case, the rear wheels are controlled to the same wheel speed and the inner wheels are turned. Generation of a moment in the turning direction due to a difference between the turning outer wheel and the braking force can be prevented.

According to the ninth aspect of the present invention, the threshold value used to determine the turning state is changed according to the vehicle speed, so that after the vehicle starts turning, the turning inner wheels are turned at different timings according to the vehicle speed. Can be started. Therefore, according to the braking force control device according to the present invention, when a high-speed lane change or the like is performed while preventing unnecessary execution of the braking force control when turning with low lateral acceleration is performed. In addition, desired braking force control can be performed based on excellent responsiveness.

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

According to the eleventh aspect of the present invention, the target wheel speed of the rear wheel is set to be higher than the target wheel speed of the front wheel in a situation where all the wheels can maintain an appropriate grip state. Therefore, in such a situation, the braking ability of the rear wheels is effectively used, and a high braking ability can be realized in the vehicle. In a situation where it is determined that any one of the wheels may shift to the locked state, the target wheel speed of the rear wheel is set to be higher than the target wheel speed of the front wheel. For this reason, the lock of the wheel 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 securing a high braking ability and stabilizing the vehicle behavior near the limit.

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

According to the thirteenth aspect, when it is determined that an abnormality has occurred in the system based on the duration of 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,
The disadvantage that the braking force of the turning inner wheel is inappropriately controlled can be avoided.

According to the fourteenth aspect, 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, the disadvantage that the understeer characteristic is promoted by controlling the braking force of the turning inner wheel can be avoided.

According to the fifteenth aspect, when understeer characteristics are detected in the vehicle, the braking force control of the turning inner wheel can be stopped to increase the braking force, and the braking force of the turning outer wheel can be increased. By controlling the power, a further increase in the braking force can be suppressed. Therefore, according to the braking force control device of the present invention, the deviation between the braking force of the turning inner wheel and the braking force of the turning outer wheel is rapidly reduced, so that the understeer characteristics of the vehicle can be quickly and reliably reduced. Can be suppressed.

According to the sixteenth aspect of the present invention, the first set value is a threshold value used for determining whether to execute the braking force control, so that the execution region of the braking force control can be freely set. It has been. Further, by calculating the target wheel speed of the turning inner wheel assuming a second setting value larger than the first setting value as the lateral acceleration acting on the vehicle, the turning inner wheel of the turning inner wheel can be extended 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. As described above, according to the braking force control device of the present invention, the slip ratio of the turning inner wheel and the slip ratio of the turning outer wheel can be matched in a free region without providing a mechanism for detecting an accurate lateral acceleration. Can be executed.

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

[Brief description of the 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 illustrating a braking force control process executed by an antilock braking force control circuit according to a first embodiment of the present invention.

FIG. 3 is a diagram illustrating a speed relationship of a vehicle body acting when the vehicle turns.

FIG. 4 is a diagram showing the wheel speed of each wheel acting when the vehicle is turning.

FIG. 5 is a flowchart illustrating a braking force control process executed by an antilock braking force control circuit according to a 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 illustrating 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 performed 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. 11;

FIG. 13 is a flowchart for describing a braking force control process executed after the process of FIG. 12;

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

FIG. 15 is a flowchart of an example of a control routine executed in a ninth embodiment of the present 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 a tenth embodiment of the present invention.

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

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

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

FIG. 21 is a diagram illustrating a state of a fluctuation occurring in a deviation ΔV between the target wheel speed V _WI ^* and the wheel speed V _WI under a situation where the wheel speed is unstable.

FIG. 22 is a flowchart of an example of a control routine executed in a 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 shows characteristic value coordinates for describing a method for detecting a steering characteristic in the thirteenth embodiment of the present invention.

25 is a diagram showing a correspondence between each area 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 a thirteenth embodiment of the present invention.

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

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

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

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

FIG. 31 is a diagram showing a fluctuation state of brake hydraulic pressure of inner and outer turning wheels realized by a 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 (the operation when a failure has occurred in the brake path).

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

FIG. 35 shows the relationship between the target wheel speed V _WI ^* calculated based on the lateral acceleration Gy and the lateral acceleration Gy, and the relationship between the target wheel speed V _WI ^* and the lateral acceleration Gy calculated without using the lateral acceleration Gy. FIG.

FIG. 36 shows the relationship between the ideal pressure reduction control amount and the lateral acceleration Gy,
FIG. 4 is a diagram illustrating a relationship between an approximate pressure reduction control amount and a lateral acceleration Gy.

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

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Brake pedal 3 Master cylinder 4, 5 Reservoir 6-9 Wheel cylinder 10 First brake line 11 Second brake line 12-15 Pressure increasing switching valve 16-19 Pressure reducing switching valve 20-27 Supply Pipes 28a to 28d Supply lines 29 to 34 Recirculation pipes 54, 55 Suction pump 60 Antilock braking force control circuit 61 Vehicle speed sensor 62 Acceleration sensor 63 to 66 Wheel speed sensor 67 Brake switch

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masahiro Hara 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Tadashi Chiba 1 Toyota Town Toyota City, Aichi Prefecture Toyota Motor Corporation ( 56) References JP-A-4-100766 (JP, A) JP-A-62-125944 (JP, A) JP-A-2-171373 (JP, A) JP-A-1-215657 (JP, A) JP-A-4-135923 (JP, A) JP-A-1-208255 (JP, A) JP-A-61-291261 (JP, A) JP-A-2-70937 (JP, A) JP-A-4-133825 (JP JP-A-6-239216 (JP, A) JP-A-62-227845 (JP, A) JP-A-59-38160 (JP, A) JP-A-2-283555 (JP, A) 7-329757 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B60T 8/58 B60T 8/24

Claims (17)

(57) [Claims] 1. 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, a lateral acceleration detecting means for detecting a lateral acceleration acting on the vehicle, Turning state determining means for determining whether or not the vehicle is in a turning state; braking state determining means for determining whether or not the vehicle is in a braking state; and determining that the vehicle is in a turning braking state. In this case, the slip state of the turning outer wheel and the slip state of the turning inner wheel are the same based on the vehicle speed, the lateral acceleration, and the actual wheel speed of the turning outer wheel detected by the wheel speed detecting means. Target turning inside wheel speed calculating means for calculating a target wheel speed of the turning inner wheel; braking force control means for controlling a braking force of the turning inner wheel so that the wheel speed of the turning inner wheel becomes the target wheel speed; A braking force control device comprising: 2. The braking force control device according to claim 1, wherein the target turning inside wheel speed calculating means includes a target turning inside wheel speed V _WI , a vehicle body speed V _B , a lateral acceleration Gy, a turning outside wheel speed. _Is V _WO , V _WI = ｛(V _B −d · Gy / 2V _B ) / (V _B + d · G)
y / 2V _B )｝ · V _WO A braking force control device that calculates a target turning inside wheel speed V _WI . 3. The braking force control device according to claim 1, wherein the target turning inside wheel speed calculating means calculates V _WI = (V _WO ² -2dGy) ^1/2 target turning inside wheel speed V _WI by the following equation. A braking force control device, which performs a calculation. 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 when it is determined in a determination unit configured to determine whether a predetermined value), and a non-braking state detecting means for detecting a non-braking state, when turning and braking ^{_{V WO 2 -V WI 2> K}} , handed
The slip rate of the outer wheel and the slip rate of the inner wheel
Braking force control device characterized by comprising a braking force control means for controlling the braking force of the turning inner wheel such that ^{_{V WO 2 -V WI 2 = K}} , the order to the deviation to zero. 5. 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, a lateral acceleration detecting means for detecting a lateral acceleration of the vehicle, Braking detecting means for detecting a braking state of the vehicle, a vehicle speed detected by the vehicle speed detecting means, a turning inner wheel speed detected by the wheel speed detecting 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 ; Slip rate
Braking force control means for applying a braking force to outer wheels such that the turning outer wheel speed becomes the target turning outer wheel speed in order to reduce the deviation from zero to zero. . 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 when it is determined in a determination unit configured to determine whether a predetermined value), and a non-braking state detecting means for detecting a non-braking state, the non-braking and ^{_{V WO 2 -V WI 2> K}} , turning
Between the slip rate of the outer wheel and the slip rate of the turning inner wheel
Braking force control device characterized by comprising a braking force control means for applying braking force of the turning outer wheel such that ^{_{V WO 2 -V WI 2 = K}} , the order to the deviation to zero. 7.The braking force control device according to claim 2 or 3.
And further, Wheel speed detected by the wheel speed detecting means
Lateral acceleration estimating means for calculating an estimated lateral acceleration from the degree, and the lateral acceleration detected by the lateral acceleration detecting means
The lateral acceleration is detected by comparing the estimated lateral acceleration.
Abnormality occurrence determination means for determining whether or not abnormality has occurred in the means;To
Have The target turning inside wheel speed calculating means, Abnormal occurrence judgment
Determining that the lateral acceleration detecting means is abnormal by the determining means
Was donein case ofDetected by the wheel speed detecting means
Target vehicle of inner wheel when turning based on turning outer wheel speed
Calculate wheel speedAnd the abnormality occurrence determination means
When the lateral acceleration detecting means is determined to be normal
Is the vehicle speed, the lateral acceleration, and the wheel speed
The actual wheel speed of the turning outer wheel detected by the detecting means
The slip condition of the turning outer wheel and the slip condition of the turning inner wheel are
The target wheel speed of the turning inner wheel is set so that
Is set to calculateA braking force control device, characterized in that: 8. A vehicle speed detector for detecting a vehicle speed of a vehicle, a wheel speed detector for detecting a speed of each wheel of the vehicle, a lateral acceleration detector for detecting a lateral acceleration acting on the vehicle, Turning braking state determining means for determining whether the vehicle is in a turning braking state; and, during braking, a vehicle speed detected by the vehicle speed detecting means, and a front outer wheel speed detected by the wheel speed detecting means. And calculating a target wheel speed of the inner wheel before turning based on the lateral acceleration detected by the lateral acceleration detecting means so that the slip state of the outer wheel before turning and the slip state of the inner wheel before turning are the same. A target turning front inner wheel speed calculating means, and a target wheel speed of the turning rear outer wheel is calculated based on the turning front outer wheel speed detected by the wheel speed detecting means during braking. Target turning rear outer wheel speed calculating means; and, during braking, target turning rear inner wheel speed calculating means for calculating a target wheel speed of the rear inner wheel based on the front turning outer wheel speed detected by the wheel speed detecting means. A brake for comparing each wheel speed detected by the wheel speed detecting means with each of the target wheel speeds, and adjusting a brake pressure supplied to a brake mechanism such that the wheel speed of each wheel becomes the target wheel speed; Pressure adjusting means, brake pressure switching means for switching the brake pressure to each of the wheels to one of pressure increase, hold, and pressure reduction in accordance with a command from the brake pressure adjust means; A stepped road detecting means for detecting that the road is a low friction road (low μ road) from a traveling road surface, and a stepped road detected by the stepped road detecting means.
Brake pressure command selection means for comparing brake pressure increase, hold, and pressure reduction commands to the inner wheel after turning and the outer wheel after turning, and select a command to set the brake pressure to a lower pressure side; Switching the brake pressure switching mechanism based on the brake pressure command selected from
Braking force control means for controlling a brake pressure on the rear inner wheel after turning and the rear outer wheel after turning. 9. The braking force control device according to claim 1, wherein the turning state determining unit includes a threshold value changing unit that changes a threshold value used for determining a turning state according to a vehicle speed. 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 wheel 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 target wheel speeds of front wheels. 11. A braking force control device according to claim 10, wherein: a slip ratio detecting means for detecting a slip ratio of at least one of a front wheel and a rear wheel; and a target wheel speed of a rear wheel when the vehicle is in a braking state. But,
A second target wheel speed setting means for setting a target wheel speed of the front and rear wheels so as to be larger than a target wheel speed of the front wheel; and a slip rate detected by the slip rate detecting means is equal to or less than a predetermined value. In the case, the target wheel speed set by the first target wheel speed setting means is set, and when the slip ratio exceeds a predetermined value, the target wheel speed set by the second target wheel speed setting means is set as the target. And a target wheel speed switching means adopted as the wheel speed. 12. The braking force control device according to claim 1, wherein a wheel speed instability detecting means for detecting a wheel speed instability, and a braking force when the wheel speed instability exceeds a predetermined value. And a braking force control prohibiting means for prohibiting the control of the braking force control. 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 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, wherein a steering characteristic detecting means for detecting a steering characteristic of the vehicle, and wherein the control of the braking force of the turning inner wheel is stopped when the steering characteristic is understeer. 2. A braking force control device, comprising: a braking force control suspending unit. 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 braking force of the turning outer wheel is gradually increased. A braking force control device comprising a turning outer wheel braking force control means for controlling power. 16. An outer wheel speed detecting means for detecting a wheel speed of a turning outer wheel, an inner wheel speed detecting means for detecting a wheel speed of a turning inner wheel, based on a wheel speed of the turning outer wheel and a wheel speed of the turning inner wheel. A lateral acceleration estimating means for estimating a lateral acceleration acting on the vehicle; and a lateral acceleration estimated by the lateral acceleration estimating means,
A lateral acceleration discriminating means for determining whether or not the value exceeds a set value, and assuming that the lateral acceleration acting on the vehicle is a second set value larger than the first set value, Target turning inside 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. When the lateral acceleration estimated by the above exceeds the first set value, 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, A braking force control device comprising: 17. The braking force control device according to claim 1, wherein the target turning inner wheel speed calculating means calculates 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.