JPH0899617A - Control device for braking force distribution - Google Patents

Abstract

PURPOSE: To adequately control braking force distribution with vibration noise etc., restrained to the utmost with a simple and inexpensive means even at the time of braking during the turning of a vehicle in a control device for braking force distribution for adjusting the braking force of a wheel in the rear of the vehicle. CONSTITUTION: Wheel speeds of respective wheels are detected by a wheel speed detecting means WS, and a liquid pressure control device FV is driven by a driving means AM based on these detected output to adjust that the braking force of a wheel RW in the rear of a vehicle can be approximate to ideal braking force distribution to the braking force of a wheel FW in the front of the vehicle. Also, the turning condition of the vehicle is judged by a turning condition judging means DM to switch a valve device EV to a first or second position according to a judged result. A liquid pressure generation device PG and a liquid pressure control device FV are communicatedly connected directly at the first position, and are connected via a liquid pressure limiting means RV to adequately reduce the brake liquid pressure of a wheel cylinder Wr for a rear wheel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a braking force distribution control device for adjusting a braking force of a wheel behind a vehicle to a predetermined relationship with a braking force of a wheel in front of a vehicle during vehicle braking.

[0002]

2. Description of the Related Art Generally, when a braking operation is performed on a running vehicle, the axial load in the front and rear of the vehicle is different due to the load movement,
The braking force for the wheels in front of the vehicle and the braking force for the wheels on the rear that are necessary for the four wheels to lock at the same time are not in a direct proportional relationship, and are in a relationship called ideal braking force distribution. It also depends on

In this regard, if the braking force applied to the rear wheels exceeds the braking force applied to the front wheels, the directional stability of the vehicle is impaired. Therefore, in order to make the braking force distribution as close as possible to the ideal braking force distribution while keeping it lower than this. A proportional pressure reducing valve, a so-called proportioning valve, is provided between the wheel cylinder and the master cylinder. According to this, the distribution line has a break point, but considering the load difference between the inner and outer wheels when turning, it is necessary to keep the braking force on the rear wheel considerably lower than the braking force on the front wheel.
However, if the brake fluid pressure is always limited via the proportioning valve, the distribution of the braking force to the wheels behind the vehicle is reduced, and a large brake pedal force is required to obtain the predetermined deceleration, and The burden on the braking device for the wheels of the vehicle becomes large.

In order to solve such a problem, JP-A-6-
In JP-A-144174, a switching valve is provided upstream of a hydraulic booster and a hydraulic control valve provided between a master cylinder and a wheel cylinder, and the switching valve is switched and the hydraulic control valve is controlled. Thus, there has been proposed a braking force distribution control device that adjusts the brake fluid pressure of the rear wheel wheel cylinder to a predetermined relationship.

Further, in JP-A-5-147516, a proportioning valve interposed between a master cylinder and a wheel cylinder is opened and closed by bypassing the proportioning valve to transmit a master cylinder pressure to the wheel cylinder. A rear wheel that is provided with a valve, sets the set pressure according to the load of the rear wheel detected by the load detection means, and opens and closes the open / close valve according to the comparison result of the master cylinder pressure detected by the master cylinder pressure detection means and the set pressure. A braking force control device is disclosed.

[0006]

[Patent Document 1] Japanese Patent Application Laid-Open No. 6-144
According to the device described in Japanese Patent No. 174, since the braking force of the rear wheels can be approximated to the ideal braking force distribution, good braking characteristics can be obtained during braking while the vehicle is traveling straight, but when the vehicle is turning. Since the cornering force on the rear wheels is reduced during braking, the stability of the vehicle may be impaired depending on the control characteristics of the hydraulic control valve. On the other hand, JP-A-5-
In the device described in Japanese Patent No. 147516, the proportioning valve is bypassed according to the load on the rear wheel, but a load detecting means for detecting the load on the rear wheel is essential. In order to embody such a load detecting means, not only an expensive sensor such as a rear wheel stroke sensor is required, but also the assembly to a vehicle is complicated and the cost becomes high. Further, in any of the devices, since it is necessary to frequently operate the hydraulic pressure control valve during the braking force distribution control, NVH (a general term for a vehicle vibration noise phenomenon meaning noise, vibration, and harshness) is caused by hydraulic pressure vibration. A problem arises.

Therefore, the present invention relates to a braking force distribution control device for adjusting the braking force of the wheels behind the vehicle. Even during braking while the vehicle is turning, a simple and inexpensive means is used to suppress vibration noise and the like as much as possible. The purpose is to enable appropriate power distribution control.

[0008]

In order to achieve the above object, the braking force distribution control device of the present invention is mounted on a wheel FW in front of a vehicle to apply the braking force as shown in the outline of the configuration of FIG. The front wheel wheel cylinder Wf to be applied and the rear wheel wheel cylinder Wr which is mounted on the rear wheel RW of the vehicle to apply the braking force, and the front and rear wheel wheel cylinders which boost the brake fluid in response to the operation of the brake pedal BP. Wf, W
A hydraulic pressure generator PG for applying a brake hydraulic pressure to each of r
And a hydraulic pressure control device FV interposed between the hydraulic pressure generator PG and at least the rear wheel wheel cylinder Wr to control the brake hydraulic pressure, and wheels FW and R on the front and rear sides of the vehicle.
Wheel speed detecting means WS for detecting each wheel speed of W
And drive means AM for driving the hydraulic pressure control device FV based on the detection output of the wheel speed detecting means WS to adjust the braking force of the wheel RW behind the vehicle in a predetermined relationship with the braking force of the wheel FW ahead of the vehicle. In a braking force distribution control device equipped with
A hydraulic pressure limiting unit RV that limits the output brake hydraulic pressure of the hydraulic pressure generator PG based on a predetermined relationship with the braking force of the wheels FW in front of the vehicle, and a turning state determining unit DM that determines the turning state of the vehicle. According to the determination result of the turning state determination means DM, the first position where the hydraulic pressure generation device PG and the hydraulic pressure control device FV are directly connected and the hydraulic pressure limitation between the hydraulic pressure generation device PG and the hydraulic pressure control device FV is performed. The valve device EV for switching to either one of the second positions connected via the means RV.

The hydraulic pressure limiting means matches the hydraulic pressure on the output side with the hydraulic pressure on the input side until the hydraulic pressure on the input side reaches a predetermined value, and the hydraulic pressure on the input side exceeds the predetermined value. At times, it is preferable to use a proportional pressure reducing valve that suppresses the increase in the hydraulic pressure on the output side to a predetermined ratio to the increase in the hydraulic pressure on the input side. Further, the hydraulic pressure limiting means matches the hydraulic pressure on the output side with the hydraulic pressure on the input side until the hydraulic pressure on the input side reaches a predetermined value, and the hydraulic pressure on the input side exceeds the predetermined value. Also, it may be configured by a hydraulic pressure limiting valve that does not increase the hydraulic pressure on the output side.

The drive means drives the hydraulic pressure control device to apply the hydraulic pressure control device to the rear wheel wheel cylinder when the valve device is switched to either one of the first position and the second position. The brake fluid pressure may be controlled stepwise.

As the turning state determining means, any one of a lateral acceleration sensor, a yaw rate sensor, a steering angle sensor, etc.,
Alternatively, these may be arranged in combination, and the turning state of the vehicle may be determined based on the detection output thereof. However, the vehicle output is detected from the detection output of the wheel speed detection means for the non-driving wheel side wheel among the wheels. It is possible to calculate the wheel speed difference between the wheel located inside and the wheel located outside during turning, and to determine the turning state of the vehicle based on the wheel speed difference. Also, the turning state determination means calculates the speed of the vehicle based on the detection output of the wheel speed detection means, obtains the lateral acceleration of the vehicle from the speed difference of the vehicle and the wheel speed difference, and based on the lateral acceleration, the vehicle It may be configured to determine the turning state of the.

[0012]

In the braking force distribution control device having the above structure, when the brake pedal BP is operated, the hydraulic pressure generator PG is operated.
Brake fluid pressure is supplied to each of the front and rear wheel cylinders Wf and Wr from each other to apply a braking force to each of the wheels FW and RW. The hydraulic pressure generator PG and at least the rear wheel are used. A hydraulic pressure control device F is provided between the cylinder Wr and the cylinder Wr.
V is interposed, and by this hydraulic pressure control device FV,
The brake fluid pressure applied to the rear wheel cylinder Wr is controlled. In this case, the wheel speed detecting means W
The wheel speed of each wheel is detected by S, and the hydraulic pressure control device FV is driven by the drive means AM in accordance with the wheel speed difference based on these detected outputs, and the braking force of the wheel RW on the rear side of the vehicle is adjusted to the front side of the vehicle. The braking force of the wheels FW is adjusted so as to have a predetermined relationship, that is, to approximate the ideal braking force distribution.

Further, the turning state determination means DM determines the turning state of the vehicle, and the valve device E is determined according to the determination result.
V is switched to the first position or the second position. That is, the first
In the position, the hydraulic pressure generator PG and the hydraulic pressure control device FV are directly connected to each other, and in the second position, the hydraulic pressure generator PG and the hydraulic pressure control device FV are hydraulic pressures comprising, for example, a proportional pressure reducing valve according to claim 2. It is connected via the limiting means RV. Thus, the second
In the position, the output brake hydraulic pressure of the hydraulic pressure generator PG is limited by the hydraulic pressure limiting means RV based on a predetermined relationship between the braking force of the vehicle front wheel FW and the braking force of the vehicle rear wheel RW. The brake fluid pressure in the wheel cylinder Wr is appropriately reduced. As a result, a sufficient cornering force is ensured for the rear wheels RW, and the stability of the vehicle is maintained.

According to the drive means AM configured as described in claim 3, when the valve device is switched during the turning operation of the vehicle, the brake fluid pressure applied to the rear wheel wheel cylinder Wr is stepwise. Therefore, it is possible to avoid a situation in which the brake fluid pressure in the rear wheel wheel cylinder Wr changes suddenly and the vehicle behavior changes.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows a brake fluid pressure control device according to an embodiment of the present invention, which is provided with a master cylinder MC and a regulator RG which constitute the fluid pressure generation device of the present invention, and which are operated in response to an operation of a brake pedal BP. Driven. An auxiliary hydraulic pressure source AP is connected to the regulator RG, and these are connected to the low pressure reservoir RS together with the master cylinder MC. The auxiliary hydraulic pressure source AP has a hydraulic pump HP and an accumulator ACC. The hydraulic pump HP is driven by an electric motor (not shown), and the low pressure reservoir R
The brake fluid of S is boosted and output, and this brake fluid is supplied to the accumulator ACC via the check valve CV1.
Accumulated. Thus, the so-called power hydraulic pressure is appropriately supplied from the accumulator ACC to the regulator RG. The electric motor is driven in response to the hydraulic pressure in the accumulator ACC falling below a predetermined lower limit value, and is stopped in response to the hydraulic pressure in the accumulator ACC exceeding a predetermined upper limit value.

The regulator RG receives the output hydraulic pressure of the auxiliary hydraulic pressure source AP, regulates the output hydraulic pressure of the master cylinder MC as a pilot pressure, and adjusts the regulator hydraulic pressure in proportion to the pilot hydraulic pressure. Since it is disclosed in Japanese Patent Publication No. 476664, detailed description will be omitted. The regulator RG of the present embodiment is configured to adjust the control hydraulic pressure to a predetermined ratio with respect to the output brake hydraulic pressure of the master cylinder MC (that is, the pressure proportional to the output brake hydraulic pressure of the master cylinder MC). The regulator RG can be configured separately from the master cylinder MC. Also,
Instead of the regulator RG, a hydraulic booster may be used in the hydraulic pressure generator of the present invention.

On the other hand, wheel cylinders Wfl, Wfr, Wrl, Wrr are mounted on the wheels FL, FR, RL, RR, respectively, and a hydraulic pressure passage connecting the master cylinder MC and each of the wheel cylinders Wfl, Wfr in front of the vehicle. The first valve device EV1 to the sixth valve device EV6 are interposed in the. Further, the seventh valve device EV7 to the tenth valve device EV10 and the proportional pressure reducing valve P are provided in the hydraulic passages connecting the regulator RG and the wheel cylinders Wrl, Wrr on the rear side of the vehicle.
V is installed. These first valve devices EV1 to ninth
The fluid pressure control device according to the present invention is configured by the valve device EV9, and the tenth valve device EV10 corresponds to the valve device of the present invention. In addition, the wheel FL indicates the wheel on the front left side when viewed from the driver's seat, hereinafter the wheel FR indicates the front right side, the wheel RL indicates the rear left side, and the wheel RR indicates the rear right wheel. As is clear from FIG. In the example, the front and rear pipes are divided into a hydraulic control system for the front wheels and a hydraulic control system for the rear wheels.
A so-called X pipe may be used. Further, in this embodiment, the wheels RL, RR on the rear side of the vehicle are drive wheels and the wheels FL, FR on the front side are so-called rear wheel drive related wheels, but they may be front wheel drive.

In the front wheel hydraulic system, the master cylinder M
The first valve device EV1 and the second valve device EV2 are respectively provided in the hydraulic paths that connect C and the wheel cylinders Wfl and Wfr on the front wheel side.
Are installed in the control passage Pfl,
The fifth valve device EV5 and the sixth valve device E are respectively connected via Pfr.
It is connected to V6. The fifth valve device EV5 and the sixth valve device EV6 are further connected to the third valve device EV4 via the fourth valve device EV4.
It is connected to the valve device EV3 and communicates with the regulator RG or the accumulator ACC. The first valve device EV1 and the second valve device EV2 are 3-port / 2-position electromagnetic switching valves, which are in the first position shown in FIG. 1 in a non-operating state, and the wheel cylinders Wfl and Wfr are both connected to the master cylinder MC. However, when the solenoid coil is excited and switched to the second position, the wheel cylinders Wfl and Wfr are both disconnected from the master cylinder MC, and the wheel cylinders Wfl and Wfr are respectively in the fifth position.
It communicates with the valve device EV5 and the sixth valve device EV6.

The third valve device EV3 and the fourth valve device EV4 are also 3-port / 2-position electromagnetic switching valves, and the third valve device EV3
Disconnects the fourth valve device EV4 and the proportional pressure reducing valve PV from the regulator RG in the first position in the non-operating state, and disconnects the fourth valve device EV4 and the proportional pressure reducing valve PV from the regulator RG in the second position in the operating state. Communication with the accumulator ACC. The fourth valve device EV4 communicates the third valve device EV3 with the fifth valve device EV5 and the sixth valve device EV6 in the first position in the non-actuated state, and disconnects these communication in the second position in the actuated state. , The fifth valve device EV5 and the sixth valve device EV6 communicate with the low pressure reservoir RS.

On the other hand, both the fifth valve device EV5 and the sixth valve device EV6 are 2-port / 2-position electromagnetic switching valves, which are in the open position as shown in FIG. Then, the valve is closed and the hydraulic passage is shut off. The check valve CV2 and the throttle passage OR1 are connected in parallel to the fourth valve device EV4 and the fifth valve device EV5, and the check valve C4 is parallel to the fourth valve device EV4 and the sixth valve device EV6. The CV3 and the throttle passage OR2 are connected to each other, the inflow side of the check valve CV2 is connected to the control passage Pfl, and the inflow side of the check valve CV3 is connected to the control passage Pfr.

The throttle passage OR1 is provided with the first valve device EV when the third valve device EV3 is inactive when the brake pedal BP is operated.
When the first, fourth, and fifth valve devices EV4, EV5 are activated, the brake fluid from the regulator RG is provided to gently flow into the wheel cylinder Wfl. Is also the same. Further, the check valve CV2 causes the brake fluid pressure of the wheel cylinder Wfl to quickly follow the decrease in the output fluid pressure of the regulator RG when the brake pedal BP is released when the first valve device EV1 is in the operating state. It is provided for the purpose of allowing the flow of the brake fluid in the direction of the third valve device EV3 and blocking the flow in the opposite direction.
The same applies to the check valve CV3.

Next, the rear wheel side hydraulic system will be described.
The tenth valve device EV10 is arranged in parallel with the third valve device EV3.
And a proportional pressure reducing valve PV are connected. Tenth valve device E
V10 is a 3-port 2-position electromagnetic switching valve, which is in the first position shown in FIG. 2 in a non-actuated state, and directly connects the seventh valve device EV7 and the regulator RG to establish a proportional pressure reducing valve PV and a third valve. The communication with the regulator RG via the device EV3 is cut off. When the tenth valve device EV10 is switched to the operating second position, the seventh valve device EV7 is disconnected from the direct communication with the regulator RG, and is connected to the third valve device EV3 via the proportional pressure reducing valve PV. Third valve device EV3
It is connected to the accumulator ACC or the regulator RG depending on the operation / non-operation of the.

The proportional pressure reducing valve PV constitutes the hydraulic pressure limiting means of the present invention, and the output of the regulator RG is the third valve device EV.
When the hydraulic pressure on the output side (the hydraulic pressure on the tenth valve device EV10 side) rises to a predetermined hydraulic pressure when being supplied to the wheel cylinders Wrl, Wrr for the rear wheels via the third and tenth valve device EV10. Is the hydraulic pressure on the output side (the third valve device E
V3 side hydraulic pressure), but in the process in which the output side hydraulic pressure further rises, the rate of increase of the output side hydraulic pressure is adjusted to be kept small at a predetermined ratio with respect to the increase of the input side hydraulic pressure. And is generally known as a proportioning valve. Alternatively, the hydraulic pressure limiting means may be constituted by a hydraulic pressure limiting valve. This means that the hydraulic pressure on the output side matches the hydraulic pressure on the input side until the hydraulic pressure on the output side rises to a predetermined hydraulic pressure. However, the hydraulic pressure on the output side is not increased even if the hydraulic pressure on the input side is further increased, and is generally known as a limiting valve.

The seventh valve device EV7 is a 3-port / 2-position electromagnetic switching valve and has the same relationship as the fourth valve device EV4 of the front wheel hydraulic system. That is, the first position in the non-actuated first position
0 valve device EV10, 8th valve device EV8 and 9th valve device E
V8 is communicated with, and the communication is cut off in the second position in the operating state, and the eighth valve device EV8 and the ninth valve device EV9 are switched so as to communicate with the low pressure reservoir RS.
The eighth valve device EV8 and the ninth valve device EV9 also include the fifth valve device EV8.
Similar to the valve device EV5 and the sixth valve device EV6, it is a 2-port 2-position electromagnetic on-off valve, which is in the valve open position in the non-operating state, and in the valve operating position the valve is closed and the hydraulic passage is shut off.

Further, the seventh valve device EV7 and the eighth valve device E
The check valve CV4 and the throttle passage OR3 are connected in parallel with V8, and the seventh valve device EV7 and the ninth valve device E are connected.
The check valve CV5 and the throttle passage OR4 are connected in parallel to V9, the inflow side of the check valve CV4 is connected to the wheel cylinder Wrl, and the inflow side of the check valve CV5 is connected to the wheel cylinder Wrr. The throttle passage OR3 (or the throttle passage OR4) is the first when the brake pedal BP is operated.
When the seventh valve device EV7 and the eighth valve device EV8 (or the seventh valve device EV7 and the ninth valve device EV9) are activated while the zero valve device EV10 is in the inoperative state, the regulator R
There is also one provided so that the brake fluid from G gently flows into the wheel cylinder Wrl (or the wheel cylinder Wrr). Further, the check valves CV4 and CV5 are provided for quickly causing the brake fluid pressures of the wheel cylinders Wrl, Wrr to follow the decrease in the output fluid pressure of the regulator RG when the brake pedal BP is released. Thus, the flow of the brake fluid in the direction of the tenth valve device EV10 is allowed and the flow in the reverse direction is blocked.

In the brake fluid pressure control device having the above-described structure, the main operation in response to the control by the first valve device EV1 to the tenth valve device EV10 will be described. Valve devices EV1 to EV1
All the zero valve devices EV10 are in the non-actuated state and are set to the first position shown in FIG. Thus, the brake fluid pressure is supplied from the master cylinder MC to the wheel cylinders Wfl or Wfr via the first valve device EV1 or the second valve device EV2 in accordance with the operation of the brake pedal BP, and the master fluid is supplied from the regulator RG. The regulator hydraulic pressure proportional to the output of the cylinder MC is output, and the tenth valve device EV1
0, the seventh valve device EV7 and the eighth valve device EV8 or the ninth valve device EV9 are supplied to the wheel cylinders Wrl or Wrr. Then, the tenth valve device EV10
Is controlled to be switched to the second position, the output of the regulator RG is depressurized at a predetermined rate via the proportional pressure reducing valve PV and supplied to the wheel cylinders Wrl, Wrr.

In the braking force distribution control for the front and rear wheels, when the brake pedal BP is operated, the seventh valve device EV7 is activated, and the eighth valve device EV8 and the eighth valve device EV8 are operated in accordance with the behaviors of the wheels RL, RR on the rear sides of the vehicle. The 9-valve device EV9 is controlled to open and close,
The hydraulic pressure in the wheel cylinders Wrl, Wrr is lower than the output hydraulic pressure of the regulator RG, and the braking force on the rear wheel side is adjusted to have a predetermined relationship with the braking force on the front wheel side,
The characteristics are controlled so as to approximate the ideal braking force distribution curve. According to the present embodiment, various controls including the anti-skid control described later, including this braking force distribution control, can be performed. However, the electronic control unit ECU described later receives the brake switch BS and the wheels as its control input. Speed sensors WS1 to WS4, lateral acceleration sensor YS and / or front wheel steering angle sensor, longitudinal acceleration sensor, yaw rate sensor (not shown)
, Etc. are supplied.

Next, if any of the wheels tends to lock during braking, the control shifts to anti-skid (ABS) control. For example, when the anti-skid control is performed on the front wheel FL, the first valve device EV1 and the fourth valve device EV4 with the third valve device EV3 kept in the inoperative state.
Is activated and, depending on the locked state of the wheels FL, the fifth
The valve device EV5 is controlled to open and close. As a result, the wheel cylinder Wfl is disconnected from the master cylinder MC, and instead communicates with the regulator RG. At this time,
When the fifth valve device EV5 is in the valve open state, the brake fluid in the wheel cylinder Wfl passes through the first valve device EV1, the fifth valve device EV5 and the fourth valve device EV4 and the low pressure reservoir R.
It flows out to S and the hydraulic pressure in the wheel cylinder Wfl is reduced. At this time, the sixth valve device EV6 is activated to prevent the brake fluid from the regulator RG from being wasted. On the other hand, when the fifth valve device EV5 is closed, the output hydraulic pressure of the regulator RG is supplied to the wheel cylinder Wfl via the third valve device EV3, the throttle passage OR1 and the first valve device EV1, and the hydraulic pressure in the wheel cylinder Wfl is increased. Is gradually increased (slow pressure increase operation). In this way, the pressure reducing operation and the gradual pressure increasing operation are repeated, and an appropriate braking force is applied while preventing the wheels FL from being locked. It should be noted that the wheel FR side is similarly processed. In addition, the wheels FL,
When anti-skid control is performed on both sides of FR, when one wheel, for example, wheel FL side, cannot perform pressure increasing operation on the other wheel FR side, pressure increase request on the wheel FR side is required. Slow boost operation is necessary.

When anti-skid control is performed on the rear wheel RL, the seventh valve device EV7 is activated while the third valve device EV3 and the tenth valve device EV10 remain inoperative. , The seventh valve device EV7 is the tenth
The communication with the valve device EV10 is cut off and the low pressure reservoir RS
Communicate with. In this state, when the eighth valve device EV8 is in the open state, the brake fluid in the wheel cylinder Wrl flows out to the low pressure reservoir RS via the eighth valve device EV8 and the seventh valve device EV7, and the pressure is reduced. At this time, the ninth valve device E
V9 is activated so that the brake fluid from the regulator RG is not wasted. On the other hand, when the eighth valve device EV8 is closed, the regulator RG
Output hydraulic pressure of the tenth valve device EV10 and the throttle passage OR3
Is supplied to the wheel cylinder Wrl via the, and the pressure is gradually increased. The same processing is performed on the wheel RR side. Further, when anti-skid control is performed on both sides of the wheels RL, RR, when one wheel, for example, the wheel RL side is depressurized, the other wheel RR side cannot be boosted. Slow pressure boosting is used to meet the demand. In this way, the slow pressure increasing operation and the pressure reducing operation are repeated according to the opening / closing control of the eighth valve device EV8 (or the ninth valve device EV9).

Next, for example, so-called traction control is performed in order to prevent the wheels RL and RR on the drive wheel side from slipping due to acceleration slip occurring at the time of starting the vehicle. As a part of this, traction control is performed to the wheels RL and RR. Acceleration slip is prevented by applying power. At the time of this traction control, the third valve device EV3, the seventh valve device EV7 and the tenth valve device EV10 are activated, and for example, when the eighth valve device EV8 is closed, the output power hydraulic pressure of the accumulator ACC becomes Third valve device EV3, proportional pressure reducing valve P
V, the tenth valve device EV10 and the throttle passage OR3 are supplied to the wheel cylinder Wrl to apply a braking force to the wheels RL. On the contrary, when the eighth valve device EV8 is opened, the wheel cylinder Wrl communicates with the low pressure reservoir RS via the operating seventh valve device EV7, and the brake fluid in the wheel cylinder Wrl flows out to reduce the pressure. To do. Thus, an appropriate braking force is applied to the wheels RL according to the opening / closing control of the eighth valve device EV8. The wheels RR are also controlled in the same manner.

The first valve device EV1 to the tenth valve device E
V10 is connected to the electronic control unit ECU shown in FIG. 3 to control the operation and non-operation of each. The electric motor (not shown) that drives the hydraulic pump HP is also an electronic control unit ECU.
And is driven and controlled by this. Also, the wheel F
Wheel speed sensors WS1 to W are provided for L, FR, RL, and RR.
S4 is provided, these are connected to the electronic control unit ECU, and the rotational speed of each wheel, that is, the wheel speed signal is input to the electronic control unit ECU. Further, a brake switch BS that is turned on when the brake pedal BP is depressed, a lateral acceleration sensor YS that detects a lateral acceleration of the vehicle, and the like are connected to the electronic control unit ECU.

As shown in FIG. 3, the electronic control unit ECU includes a microcomputer CMP including a processing unit CPU, a memory ROM, a RAM, a timer TMR, an input port IPT and an output port OPT which are connected to each other via a bus. I have it. Wheel speed sensor W
The output signals of S1 to WS4, the brake switch BS, the lateral acceleration sensor YS, etc. are input to the processing unit CPU from the input port IPT via the amplifier circuit AMP, respectively. Further, from the output port OPT, the first valve device EV1 through the first valve device EV1 are connected via the drive circuit ACT.
A control signal is output to the zero valve device EV10. In the microcomputer CMP, the memory ROM stores the program corresponding to the flowcharts shown in FIG. 4 and subsequent figures, the processing unit CPU executes the program while the ignition switch (not shown) is closed, and the memory RAM stores the program. Temporarily stores variable data required for execution of.

In the present embodiment configured as described above, a series of processing such as anti-skid control is performed by the electronic control unit 10, and the seventh valve device EV7 to the tenth valve device EV10 are used as the braking force distribution control. Is controlled. That is, in the microcomputer 11, when the ignition switch (not shown) is closed, execution of the program corresponding to the flowcharts of FIGS. 4 to 7 starts. The above-mentioned traction control is omitted in the following flowcharts.

First, in FIG. 4 showing the main routine,
At step 101, the microcomputer 11 is initialized and various calculated values are cleared. Next step 10
2, the detection signals of the wheel speed sensors WS1 to WS4 are read and the detection signals of the lateral acceleration sensor YS are read, and step 103 is performed based on these signals.
At four wheel speeds VwFR, VwFL, VwRR, V
wRL is calculated. In step 104, the wheel speeds are differentiated and the wheel accelerations DVwFR, D of the wheels are calculated.
VwFL, DVwRR and DVwRL are calculated. An acceleration sensor may be provided and the detection signal thereof may be used. Further, in step 105, the estimated vehicle body speed Vso and the acceleration DVso which is a differential value thereof are calculated based on the wheel speed.
Is calculated. The estimated vehicle body speed Vso is set as a vehicle body speed, for example, on the assumption that the wheel speed during braking is decelerated at a predetermined deceleration, and even one of the four wheels exceeds this value. Sometimes, the value when the vehicle is decelerated again with a predetermined deceleration is set as the vehicle body speed, which is the same as the reference speed used for the conventional anti-skid control.

Next, in step 300, it is determined whether or not the antiskid control start condition is satisfied. If the start condition is satisfied and the antiskid control mode is determined, the antiskid control is performed in step 400. Transition. When it is determined in step 300 that the anti-skid control mode is not in effect, the routine proceeds to step 500, where it is determined whether or not the braking force distribution control mode is in effect. Proceed to. Whether or not the braking force distribution control mode is set is determined based on various conditions of the vehicle in the braking state. For example, when the anti-skid control system is normal, the braking force distribution control system is normal, and the wheels RR and RL behind the vehicle are not in the anti-skid control, the braking force distribution control is performed. When it is determined to be possible, the routine proceeds to step 600, where the braking force distribution control shown in FIG. 5 is performed, and after completion, the routine returns to step 102.

In step 700, it is determined whether a predetermined braking operation has been performed. Specifically, after the brake pedal BP is operated, the wheels FR (F
L) wheel speed VwFR (VwFL) is estimated vehicle speed Vso
When the wheel acceleration DVw of the differential value of the wheel speed falls below a predetermined acceleration (including deceleration) G1, it is determined that “output before control is possible”, and the routine proceeds to step 800 to start pre-control holding control. , Otherwise step 102
Return to. This pre-control holding control is adopted in a conventional anti-skid control device, and is controlled to hold the brake fluid pressure before the braking operation is performed and the anti-skid control is performed. When the pre-control holding control is completed, the process returns to step 102.

The braking force distribution control of the above step 600 comprises the routine shown in FIG. 5. First, at step 601, various constants for setting the starting condition of the braking force distribution control are set. Then, at step 602, the wheel speeds VwFR, VwFL of the wheels FR, FL, RR, RL,
The reference speeds VwsFR, VwsFL, VwsRR, and VwsRL are calculated by predetermined calculation processing based on VwRR and VwRL. This arithmetic processing will be described later with reference to FIG. 7. Further, in step 603, reference speed differences (VwsRR-VwsFR) and (VwsRL-VwsFL) between the front and rear wheels are calculated as DVwsRR and DVwsRL, respectively. And
Proceeding to steps 604 and 605, braking force distribution control of the wheels RR and RL is performed.

FIG. 6 shows a subroutine of the braking force distribution control for the wheels RR in step 604 of FIG. 5, and the braking force distribution control for the wheels RL in step 605 is similarly processed. First, in step 620, it is determined whether or not control is being performed, and if the control flag indicating that braking force distribution control is being executed is not set (“0”), the flow advances to steps 621 to 631 to set. If so (“1”), the process proceeds to steps 632 to 634.

In step 621, it is determined whether or not the braking force distribution control can be started for the wheels RR. The start condition is, for example, that the brake switch BS is in the ON state and the estimated vehicle body speed Vso is equal to or higher than a predetermined speed K1 (for example, 15 km / h). When these conditions are satisfied, it is determined that the control can be started, and step 6
After the in-control flag is set ("1") at 22, the process proceeds to step 623, and if the control start condition is not satisfied, the process returns to the routine of FIG.

By the way, when the braking operation is performed while the vehicle is turning, the load movement from the rear wheel side to the front wheel side occurs as the deceleration of the vehicle increases, so that the cornering force on the front wheel side transiently increases. Cornering force on the rear wheels is reduced. For this reason, an excessive rotational moment may be generated in the vehicle and the stability of the vehicle may be impaired. As described above, when the braking force distribution control is performed, all the wheels are controlled so as to approximate the ideal braking force distribution, but when the vehicle turns at this time, the wheels are positioned outside the turning along with the movement of the left and right loads. The braking force of the rear wheels is controlled as shown by the solid line from the 0 point to a and e along the ideal braking force distribution shown by the two-dot chain line in FIG. 12, and the braking force of the rear wheels located inside the turn is In accordance with the ideal braking force distribution shown by the one-dot chain line in FIG. 12, control is performed as shown by the solid line from point 0 to points b and f. Such a braking characteristic along the ideal braking force distribution is optimal for obtaining the braking force in the straight traveling direction, but since the cornering force on the rear wheel side is reduced, it is not suitable for maintaining the stability of the vehicle. Appropriate. Therefore, when the degree of turning of the vehicle is large, the braking force of the rear wheels is 0 as shown by the broken line in FIG.
It is desirable to control along the characteristic of the proportional pressure reducing valve PV from the point to c and d. By controlling in this way, it is possible to secure sufficient cornering force for the rear wheels and maintain the stability of the vehicle. .

Therefore, when it is determined that the braking force distribution control can be started, the routine proceeds to step 623, where the turning state is determined based on the lateral acceleration Gy detected by the lateral acceleration sensor YS. When it is determined in step 623 that the lateral acceleration Gy is equal to or greater than the predetermined value K2, it is determined that the degree of turning is large, and in step 624, the tenth valve device EV10 is set to the operating state, and the slow pressure increasing operation in the latter stage (Step 63
In 1), the output hydraulic pressure of the regulator RG is supplied to the wheel cylinders Wrl and Wrr via the proportional pressure reducing valve PV. If it is determined that the lateral acceleration Gy is less than the predetermined value K2, then in step 625, the tenth valve device EV10 is left in the inoperative state.

In order to prevent hunting during the switching operation of the tenth valve device EV10, a predetermined value K is set as shown in FIG.
The value of 2 should be set to a different value when the tenth valve device EV10 is switched from the non-actuated state to the actuated state (K2a) and when it is changed from the actuated state to the non-actuated state (K2b) to provide hysteresis. Is desirable.

Next, in step 626, when the respective states in steps 624 and 625 are set, is the setting different from the previous state of the tenth valve device EV10 and the switching operation of the tenth valve device EV10 is involved? It is determined whether or not. The tenth valve device EV10 is in the previous position (first
When switching from the position or the second position), a switching process is performed in step 627 so that the fluid pressure fluctuation is suppressed and the smooth switching operation is performed. In the present embodiment, this switching process is performed by the intermittent control of the eighth valve device EV8 and the ninth valve device EV9 of FIG. 2, and the hydraulic pressures of the wheel cylinders Wrl, Wrr are increased and decreased stepwise. FIG. 10 shows that when the pressure reducing side is switched by the switching operation of the tenth valve device EV10 from the non-operating state to the operating state, the pressure reducing and holding are repeated according to the opening / closing operation of the eighth valve device EV8 (the ninth valve device EV9). It shows the state of being. On the other hand, in FIG. 11, when the pressure increasing side is switched by the switching operation from the operating state to the non-operating state of the tenth valve device EV10, the increase according to the opening / closing operation of the eighth valve device EV8 (the ninth valve device EV9). The state where pressure and holding are repeated is shown.

At step 628, the slip ratio SpRR and the like are calculated based on the reference speed VwsRR and the like,
The control reference values TsRR and DfRR are calculated. The control reference value DfRR is calculated as a change in the reference speed difference DVwsRR, that is, a difference between the previous value and the current value (DVwsRR _(n) -DVwsRR _(n-1) ). The slip rate SpRR is the slip rate ((Vws) of the reference speed VwsRR of the wheel RR on the rear right side of the vehicle with respect to the reference speed VwsFR of the wheel FR on the front right side of the vehicle.
RR-VwsFR) / VwsFR), and the integrated value I
SpRR is calculated, and these functions f (SpRR, DfRR,
The control reference value TsRR is calculated as ISpRR). The control reference value TsRL for the wheel RL is calculated in the same manner.

Specifically, in step 629, the control map shown in FIG. 8 is constructed based on the control reference values TsRR and DfRR, and the control mode is determined according to this control map. In the figure, the vertical axis represents the slip ratio SpRR
And the integrated value ISpRR are added to obtain a control reference value TsRR, the horizontal axis is the control reference value DfRR, and X1 (G)
And Y1 (%) and the intersection of X2 (G) and Y2 (%) and a line parallel to the X axis are divided into two regions P and D. The region P is in the gentle pressure increasing mode and the region D is in the pressure reducing mode, and the period TbRR of the control signal and the control mode (RR) are set in both regions. The cycle Tb
RR is calculated as (TbRR = Kb−Kc · L), where L is the length of a perpendicular line from an arbitrary point on the control map to the line segment connecting X1, Y1 and X2, Y2. , Kb, Kc are constants). Then, based on this control signal, the pressure is reduced or gradually increased in step 630 or 631, respectively. Regarding the control mode, in FIG. 6, only the pressure reducing mode, the slow pressure increasing mode, and the normal pressure increasing mode are used. However, by performing the intermittent control and duty control of each valve device shown in FIG. be able to.

On the other hand, when it is determined in step 620 that the control-in-progress flag is set ("1"), it is determined in step 632 whether the control end condition is satisfied. The termination condition is that the brake switch BS is turned off and the reference acceleration DVso is a predetermined value (-
0.25G), etc., and if any of these conditions is satisfied, it is determined that the control can be ended, the in-control flag is reset (“0”), and normal pressure increasing control is performed in step 634. If the control end condition is not satisfied, the routine proceeds to step 623, where the braking force distribution control is continued.

FIG. 7 shows the calculation processing of the reference speed in step 602 of FIG. In the figure, an example of the wheel RR on the rear right side of the vehicle is shown, but the remaining wheels are similarly processed. From step 103, the wheel speed VwRR of the wheel speed RR is supplied in a predetermined calculation cycle and sequentially stored in the memory. First, at step 651, the current value (n times) VwRR _(n) is set to A. Next, in step 652, a predetermined value α _UP · t is added to the previous value VwRR _(n-1) to make it B. Then step 6
At 53, the predetermined value α _DN · t is subtracted from the previous value to obtain C.

Then, in step 654, the median values of A, B and C are calculated, and this is set as the reference value VwsRR. It should be noted that α _UP is a value that sets an acceleration with respect to the wheel speed VwRR, that is, a limit for the rate of increase of the wheel speed VwRR, for example, 2
G (where G is gravitational acceleration) is set. t is a calculation cycle, and α _DN is a value that sets a deceleration with respect to the wheel speed VwRR, that is, a limit of a reduction rate of the wheel speed VwRR. In the present embodiment, a value (α ₁ ) of a predetermined value to the acceleration DVwRR of the differential value thereof.
Is added (DVwRR + α ₁ ). In a vehicle equipped with an acceleration sensor, α _DN is calculated as (G ₀ + α ₀ ) (where G ₀ is the detection value of the acceleration sensor,
α ₀ is the tilt correction value).

In the above embodiment, either a hydraulic booster or a vacuum booster may be used as the pressure booster for the master cylinder MC, and the output brake hydraulic pressure of the master cylinder equipped with the vacuum booster is divided into two systems. It is also possible to apply to the system of giving.

[0050]

Since the present invention is configured as described above, it has the following effects. That is, in the braking force distribution control device of the present invention, the valve device is driven according to the determination result of the turning state determination means, and the first position for directly connecting the hydraulic pressure generation device and the hydraulic pressure control device to each other, and the hydraulic pressure Since the pressure generating device and the hydraulic pressure control device are switched to either one of the second positions where they are connected via the hydraulic pressure limiting means, vibration noise and the like can be minimized by a simple and inexpensive means. The braking force distribution for the front and rear wheels during braking can be adjusted appropriately while suppressing the braking force.For braking while the vehicle is turning, the hydraulic pressure generating device and the hydraulic pressure control device are connected via the hydraulic pressure limiting means for rear wheels. The brake fluid pressure of the wheel cylinder can be appropriately reduced, and the stability of the vehicle can be maintained.

As the hydraulic pressure limiting means, for example, a proportional pressure reducing valve can be used as described in claim 2, and an inexpensive device can be provided. Further, when the drive means is configured as in claim 3, it is possible to appropriately prevent a change in vehicle behavior due to a change in brake fluid pressure when the valve device is switched while the vehicle is turning. .

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a braking force distribution control device of the present invention.

FIG. 2 is an overall configuration diagram of an embodiment of a braking force distribution control device of the present invention.

FIG. 3 is a block diagram showing a configuration of the electronic control device of FIG.

FIG. 4 is a flowchart showing a process for braking force control in one embodiment of the present invention.

FIG. 5 is a flowchart showing a process for braking force distribution control in one embodiment of the present invention.

FIG. 6 is a flowchart showing a subroutine processing of a braking force distribution control of wheels RR in the embodiment of the present invention.

FIG. 7 is a flowchart showing a process of calculating a reference speed for braking force distribution control according to an embodiment of the present invention.

FIG. 8 is a graph showing a control map used for braking force distribution control of wheels RR in one embodiment of the present invention.

FIG. 9 is a graph showing a relationship between a predetermined value serving as a criterion for switching operation of the tenth valve device and lateral acceleration in one embodiment of the present invention.

FIG. 10 is a graph showing the status of a switching process associated with the switching operation of the tenth valve device in the embodiment of the present invention.

FIG. 11 is a graph showing the status of the switching process accompanying the switching operation of the tenth valve device in the embodiment of the present invention.

FIG. 12 is a graph showing a control situation of braking force distribution in one embodiment of the present invention.

[Explanation of symbols]

 BP brake pedal BS brake switch RS low pressure reservoir MC master cylinder RG regulator HP hydraulic pump, ACC accumulator AP auxiliary hydraulic pressure source EV1 to EV10 valve device CV1 to EV4 check valve OR1 to OR4 throttle passage Pfr, Pfl control passage Wfr, Wfl , Wrr, Wrl Wheel cylinders WS1 to WS4 Wheel speed sensors FR, FL, RR, RL Wheels

(72) Inventor Masanobu Fukami 2-1-1 Asahi-cho, Kariya-shi, Aichi Aisin Seiki Co., Ltd. (72) Inventor Jun Mihara 2-1-1 Asahi-cho, Kariya-shi, Aichi Aisin Seiki Co., Ltd. (72) Inventor Takayuki Ito, 2-1, Asahi-cho, Kariya city, Aichi prefecture, Aisin Seiki Co., Ltd. (72) Inventor, Yoshiharu Nishizawa 2--1, Asahi-machi, Kariya city, Aichi prefecture, Aisin Seiki Co., Ltd. (72) Invention Shingo Sugiura 2-1-1 Asahi-cho, Kariya-shi, Aichi Aisin Seiki Co., Ltd. (72) Inventor Norio Yamazaki 2-1-1 Asahi-cho, Kariya-shi, Aichi Aisin Seiki Co., Ltd. (72) Inventor Akio Sakai Aichi 2-1-1 Asahi-cho, Kariya city, Japan Aisin Seiki Co., Ltd.

Claims (3)

[Claims] 1. A wheel cylinder for a front wheel mounted on a wheel in front of a vehicle to apply a braking force, a wheel cylinder for a rear wheel mounted on a wheel on a rear side of a vehicle to apply a braking force, and a brake fluid in response to an operation of a brake pedal. A brake fluid pressure generator for applying a brake fluid pressure to each of the front and rear wheel cylinders, and the brake provided between the fluid pressure generator and at least the rear wheel cylinder. A hydraulic pressure control device for controlling the hydraulic pressure, a wheel speed detecting means for detecting the wheel speed of each of the vehicle front wheel and the vehicle rear wheel, and driving the hydraulic pressure control device based on the detection output of the wheel speed detecting means. In the braking force distribution control device, the braking force of the wheel behind the vehicle is adjusted to have a predetermined relationship with the braking force of the wheel ahead of the vehicle. A hydraulic pressure limiting means for limiting the hydraulic pressure based on a predetermined relationship with the braking force of the wheel in front of the vehicle, a turning state determining means for determining the turning state of the vehicle, and a determination result of the turning state determining means. A first direct connection between the hydraulic pressure generator and the hydraulic pressure controller
A braking force comprising a position and a valve device for switching to any one of a second position for connecting the hydraulic pressure generating device and the hydraulic pressure control device via the hydraulic pressure limiting means. Distribution control device. 2. The hydraulic pressure limiting means matches the hydraulic pressure on the output side with the hydraulic pressure on the input side until the hydraulic pressure on the input side reaches a predetermined value, and the hydraulic pressure on the input side reaches a predetermined value. 2. The braking force distribution control device according to claim 1, wherein when it exceeds, a proportional pressure reducing valve that suppresses an increase in the hydraulic pressure on the output side by a predetermined ratio to a decrease in the hydraulic pressure on the input side. 3. The drive means includes the valve device for the first device.
When switching to either one of the position and the second position, the hydraulic pressure control device is driven to control the brake hydraulic pressure applied to the rear wheel wheel cylinder stepwise. Item 1. A braking force distribution control device according to item 1.