JP3250481B2 - Vehicle rear wheel 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 rear wheel braking force control device for a vehicle.

[0002]

2. Description of the Related Art Conventionally, in order to prevent vehicle instability due to excessive braking applied to the rear wheels during braking due to the nature of the braking hydraulic circuit or for some reason, the braking hydraulic pressure on the rear wheel side is limited during braking. The pressure is set so that even if the braking oil pressure on the front wheels increases, the oil pressure on the rear wheels does not exceed the limit pressure.

That is, the master cylinder pressure on the brake pedal side is checked, and if the pressure becomes equal to or higher than the limit pressure, the control circuit for shutting off the supply circuit of the braking oil pressure to the rear wheel side and maintaining the wheel cylinder pressure on the rear wheel side is controlled. Had gone.

[0004]

However, if the braking pressure on the rear wheel is limited as described above, even if the driver depresses the brake pedal so that the master cylinder pressure becomes equal to or higher than the limiting pressure, the rear wheel braking force is not applied. Since the braking force did not increase, the braking performance was insufficient and the braking feeling was reduced.

There is known a system in which a special valve is provided in a braking hydraulic circuit to provide only a hydraulic pressure difference between the front wheel side and the rear wheel side so as to eliminate the above-mentioned limit pressure. Providing a special valve for generating pressure has a problem in that it becomes an obstacle in controlling the brake hydraulic pressure and increases the cost.

[0006] The present invention provides a method for connecting a front wheel and a rear wheel without causing a shortage of braking performance and a reduction in braking feeling without changing a hardware mechanism such as providing a special valve. It is an object of the present invention to provide a rear wheel braking force control device capable of providing a difference for stabilizing the vehicle in the braking force.

[0007]

In the rear wheel braking force control device of the vehicle according to the present invention, the braking operation of the driver is not transmitted to the rear wheel side but detected by the braking operation detecting means. The rear wheel braking force adjusting means increases / decreases the braking force supplied to the rear wheel by the wheel braking force adjusting mechanism in accordance with the time change amount of the braking operation amount. It is reflected in the braking force on the side.

In other words, when the time change of the braking operation amount is on the stepping side, the supply rate of the braking force to the rear wheel by the wheel braking force adjusting mechanism is increased in accordance with the time change if the time change amount is large. If the time change amount is small, the supply rate of the braking force to the rear wheels by the wheel braking force adjustment mechanism is reduced.

Although the braking operation of the driver is directly reflected on the front wheel side, the braking force supply rate is adjusted on the rear wheel side based on the time change of the braking operation amount when the braking operation amount increases. Is done. For this reason, during a period in which the driver is strengthening the braking operation (in a state where the driver is depressed in terms of the brake pedal), the braking operation amount of the driver is directly reflected on the rear wheel side as it is 100% throughout the period. However, there is a period in which only a small amount of braking force is supplied compared to the amount of braking operation by the driver.

[0010] Therefore, the final braking force on the rear wheel side provided by the entire period during which the driver strengthens the braking operation is also smaller than the braking force reached by the front wheel side.
For this reason, the braking force on the rear wheel side is smaller than that on the front wheel side, and the braking force between the front wheel side and the rear wheel side can be changed without changing the hardware mechanism such as providing a special valve. A difference can be provided in the braking force to stabilize the vehicle during braking.

If the amount of time change of the braking operation amount is large, the rate of supply of the braking force to the rear wheel is increased, and if the amount of time change is small, the rate of supply of the braking force to the rear wheel is reduced. . For this reason, a change in the rear wheel braking force can be caused in accordance with the strength of the braking operation by the driver, and the shortage of the braking performance and the deterioration of the braking feeling are not caused.

In particular, in the invention of claim 1 , the rear wheel braking force adjusting means performs the following processing in addition to the above-mentioned processing.
U. In other words, when the time change of the braking operation amount detected by the braking operation detecting means is on the step-back side, if the time change amount is large, the rate of decrease of the braking force on the rear wheel side by the wheel braking force adjustment mechanism is reduced. the larger, the smaller the time variation, it intends line processing to reduce the reduction rate of the braking force at the rear wheel side by the wheel braking force adjustment mechanism.

Accordingly, even when the driver relaxes the braking operation, the braking force on the rear wheel side is reduced according to the degree of the returning of the braking operation, so that the braking feeling is not impaired. According to the second aspect of the present invention, the wheel braking force adjusting mechanism is provided.
As for the increase of the braking force on the rear wheels, a braking force increasing process for appropriately transmitting and shutting off the brake fluid pressure generated by the driver's braking operation to the rear wheels is performed, and the braking force on the rear wheels is reduced. for, it intends <br/> line braking force reduction process for performing an interrupting the discharge from the rear wheel side brake hydraulic pressure appropriately.

In addition , when the time change of the braking operation amount detected by the braking operation detecting means is on the stepping-in side, the rear wheel braking force adjusting means is responsive to the time change if the time change amount is large. The ratio of the transmission period in the braking force increase process is increased, and if the time change amount is small, the ratio of the transmission period in the braking force increase process is reduced. As a result, an effect can be obtained when the driver is strengthening the braking operation.

In the case of the same adjusting mechanism, the rear wheel braking force adjusting means, when the time change of the braking operation amount detected by the braking operation detecting means is on the step-back side, according to this time change. If the amount of time change is large, the ratio of the discharge period in the braking force reduction process may be increased, and if the amount of time change is small, the ratio of the discharge period in the braking force reduction process may be reduced. As a result, the effect obtained when the driver relaxes the braking operation is obtained.

Further, there is provided a braking operation determining means for determining whether or not the driver has performed a braking operation of a predetermined amount or more based on a detection result of the braking operation detecting means, and the rear wheel braking force adjusting means is provided. Alternatively, when the braking operation determining unit detects that the driver is performing a braking operation of a predetermined amount or more, the above-described processing as the rear wheel braking force adjusting unit may be performed. In this manner, when a braking force of a level at which vehicle stability becomes a problem occurs, a difference between the front wheel side braking force and the rear wheel side braking force can be secured, and low braking at which vehicle stability does not become a problem. At times, a necessary braking force at the time of low braking can be secured.

Further, the braking operation detecting means may detect an operation state of the brake pedal as a braking operation. As the operation state of the brake pedal, the value detected by the master pressure sensor may be used as the pressure of the master cylinder that generates the brake fluid pressure by operating the brake pedal, and the depression stroke of the brake pedal may be used.
A value detected by a stroke sensor may be used,
A value detected by a treading force sensor may be used as the treading force of the brake pedal.

[0018] The wheel braking force adjusting mechanism, when braking the vehicle,
It starts when a wheel slip greater than a predetermined value is detected, and also serves as a wheel braking force adjustment mechanism used in a braking force control that adjusts the braking force applied to the wheels to cause the vehicle to perform high deceleration according to the road surface condition. Is also good. In this case, the rear wheel braking force adjusting means functions when the braking force control is not performed. Specifically, the braking force control includes an anti-lock brake system (AB
S), and the wheel braking force adjustment mechanism is, for example, AB
This is a brake hydraulic circuit for S control.

The function of realizing each means of the rear wheel braking force control device in a computer system is provided, for example, as a program activated on the computer system side. In the case of such a program, for example,
Floppy disk, magneto-optical disk, CD-ROM,
It can be used by storing it in a machine-readable storage medium such as a hard disk, loading it into a computer system as needed, and starting it. In addition, ROM
Alternatively, the program may be stored as a machine readable storage medium such as a ROM or a backup RAM, and the ROM or the backup RAM may be incorporated in a computer system and used.

[0020]

FIG. 1 is a block diagram showing a schematic configuration of a vehicle braking force control apparatus to which the above-mentioned invention is applied. Each wheel (left front wheel FL, right front wheel FR, left rear wheel RL, right rear wheel RR) of the vehicle is provided with a hydraulic brake device (hereinafter, wheel cylinder: W) for applying a braking force to each of the wheels FL to RR. / C) 2FL, 2FR, 2RL, 2
RR and wheel speed sensors 4FL, 4FR, 4RL, 4RR for detecting rotation speeds of the wheels FL to RR are provided, respectively.

On the other hand, the torque output from the engine (here, an internal combustion engine) 6 via the transmission 8 and the drive shaft 11 is distributed by the differential gear 10 to each of the left and right rear wheels RL, RR. It has become. Further, the vehicle body (not shown) has a G sensor 14 having both functions of a longitudinal acceleration sensor in the front-rear direction and a lateral acceleration sensor in the left-right direction, a stop switch 36 which is turned on when the brake pedal 32 is operated, and a brake. A master cylinder pressure sensor 38 that detects a brake oil pressure of a master cylinder (hereinafter, also referred to as M / C) 34 that generates a brake oil pressure when the pedal 32 is depressed is also provided. These G sensor 14 and stop switch 3
6 and the detection signals from the master cylinder pressure sensor 38, and the detection signals from the wheel speed sensors 4FL to 4RR, etc., are input to an electronic control unit (ECU) 20.

The ECU 20 controls various actuators in a hydraulic circuit 40 provided in a hydraulic path from the master cylinder 34 to the wheel cylinders 2FL to 2RR of the wheels FL to RR based on these detection signals. ABS control (corresponding to the above-described braking force control) for suppressing slip generated on the wheels FL to RR during vehicle braking, and rear wheels RL,
The rear wheel braking force control for RR is executed.

The ECU 20 has a CPU, ROM, R
It is composed mainly of a microcomputer having an AM and the like. In addition, various processes executed by the ECU 20 such as ABS control and rear wheel braking force control, which will be described later, are stored in the ROM as programs, and are executed as necessary.

Next, the hydraulic circuit 40 will be described. As shown in FIG. 2, the hydraulic circuit 40 supplies the brake oil pumped from the two oil passages of the M / C 34 to the left front wheel FL and the right rear wheel RR, and the right front wheel FR and the left rear wheel RL, respectively. The two hydraulic paths 42 and 44 are provided.

In the hydraulic path 42, the left front wheel F
The route 42FL leading to the wheel cylinder 2FL of the right rear wheel RR and the route 42RR leading to the wheel cylinder 2RR of the right rear wheel RR
And electromagnetic pressure-increasing control valves 46FL and 46RR that can be switched between a pressure-increasing position communicating with the paths 42FL and 42RR and a holding position in which the paths 42FL and 42RR are shut off, respectively, and the inside of each wheel cylinder 2FL and 2RR. Electromagnetic pressure reduction control valves 48FL and 48RR for discharging brake oil are provided.

Similarly, in the hydraulic path 44, a path 44FR reaching the wheel cylinder 2FR of the right front wheel FR
And the route 4 leading to the wheel cylinder 2RL of the left rear wheel RL
4RL includes the routes 44FR and 44RL, respectively.
Pressure-increasing control valves 46FR and 46RL that can be switched between a pressure-increasing position that communicates with a pressure-retaining position and a holding position that shuts off the path.
Electromagnetic decompression control valves 48FR and 48RL for discharging brake oil from the wheel cylinders 2FR and 2RL are provided.

The pressure increase control valves 46FL, 46FR, 4
6RL and 46RR are usually at the pressure increasing position.
The position is switched to the holding position by energization from the CU 20.
Further, the pressure reducing control valves 48FL, 48FR, 48RL, 48
The RR is normally in a shut-off state, and is in a communicating state by energization from the ECU 20, and discharges brake oil in the corresponding wheel cylinders 2FL to 2RR.

On the other hand, in the hydraulic path 42, a master cylinder cut valve (hereinafter, referred to as an SM valve) 50a is provided on the path on the M / C 34 side of the pressure increase control valves 46FL, 46RR to connect / disconnect the path. ing. Then, in parallel with the SM valve 50a, when the oil pressure on the M / C 34 side becomes larger than the oil pressure on the pressure increase control valves 46FL, 46RR, the oil pressure is output from the M / C 34 to the pressure increase control. Relief valve 5 for supplying to valves 46FL and 46RR
4a is connected.

Similarly, in the hydraulic path 44, an SM valve 50b is also provided on a path on the M / C 34 side of the pressure increase control valves 46FR and 46RL to open and close the path. Then, in parallel with the SM valve 50b, M / C3
The relief valve 54b which communicates when the hydraulic pressure on the fourth side becomes higher than the hydraulic pressure on the pressure increase control valves 46FR, 46RL and supplies the pressure oil output from the M / C 34 to the pressure increase control valves 46FR, 46RL is provided. It is connected.

The SM valves 50a and 50b are connected to the power supply OF
At the time of F, the communication state is established, and the state is switched to the cutoff state by energization from the ECU 20. Further, each of the hydraulic paths 42 and 44 has a reservoir 5 for temporarily storing the brake oil discharged from the pressure reducing control valves 48FL to 48RR.
6, 58, and the brake oil is supplied to the SM valve 5
0a and the pressure increase control valves 46FL, 46RR,
Pumps 60 and 62 for pumping pressure to the path between the SM valve 50b and the pressure increase control valves 46FR and 46RL are provided. In addition, accumulators 64 and 66 for suppressing the pulsation of the internal hydraulic pressure are provided in the discharge path of the brake oil from the pumps 60 and 62, respectively.

Each of the hydraulic paths 42 and 44 has an M / C
Reservoir 34 provided above M / C 34 via
8 are provided with oil supply paths 42P, 44P for supplying brake oil directly to the pumps 60, 62. These oil supply paths 42P, 44P communicate with the oil supply paths 42P, 44P.
Reservoir cut valve to shut off (hereinafter referred to as SR valve)
70a and 70b are provided respectively.

The SR valves 70a and 70b are normally in a shut-off state, and are switched to a communication state by energization from the ECU 20. Also, each pump 60, 62
It is driven via the motor 80 when performing ABS control or the like. Next, the ABS control and the rear wheel braking force control performed by the ECU 20 will be described.

When the ABS control and the rear wheel braking force control are not performed, the pressure increasing mode shown in FIG. 7 is set, and all the solenoid valves of the hydraulic circuit 40 are turned off (OFF). FIG. 2 shows the non-control state. Specifically, SM
Valves 50a, 50b = communication position and SR valves 70a, 7
0b is the shut-off position, and furthermore, the pressure increase control valves 46FL-4
6RR = communication position, pressure reduction control valves 48FL to 48RR = cutoff position.

ABS control For example, each wheel FL-
When a slip occurs in the RR, as shown in FIG. 3, the ABS control is started for each of the wheels FL to RR, and the SM valves 50a, 5
0b = communication position (OFF) and SR valves 70a, 70b =
With the shut-off position (OFF), the motor 80 is driven to operate the pumps 60 and 62, and further, the pressure increase control valve 46FL
7 to 46RR and the pressure reduction control valves 48FL to 48RR are turned ON / OFF (energized / deenergized), respectively, so that the brake hydraulic pressure in each of the wheel cylinders 2FL to 2RR in accordance with the slip state of each wheel FL to RR is shown in FIG. Are appropriately switched to two states, ie, a pressure reduction mode and a pulse pressure increase mode.

Specifically, when it is determined that the wheels are in a locking tendency, that is, that the wheels are falling into an excessive slip state due to the deceleration of the wheels, the pressure reducing mode is executed and the pressure increasing control valve 46FL corresponding to the wheels is executed. To block 46RR (O
N) and repeating the communication (ON) and shutoff (OFF) of the pressure reduction control valves 48FL to 48RR to reduce the oil pressure of the corresponding wheel cylinders 2FL to 2RR, thereby preventing the wheels from being locked. At this time, the amount of oil depressurized from the wheel cylinders 2FL to 2RR is reduced by the depressurization control valve 48.
FL-48RR are discharged to the reservoirs 56 and 58, and further driven by the motor 80, the reservoir 5
The brake oil accumulated in 6,58 is returned to the normal brake system.

If it is determined during the ABS control that the tendency to lock the wheels has been eliminated, a pulse pressure increasing mode is executed to increase the pressures of the pressure increasing control valves 46FL to 46RR corresponding to the wheels.
Is repeated (OFF) and shut off (OFF), and the pressure reduction control valves 48FL to 48RR are shut off (OFF) to increase the hydraulic pressure of the corresponding wheel cylinders 2FL to 2RR.

In the ABS control, by such control,
The W / C pressure decreasing mode and the pulse increasing mode are repeated to secure the stability of the vehicle while preventing the wheels from being locked. If the brake pedal 32 is not depressed from the state of the stop switch 36 and the wheels do not tend to lock even if the pressure is sufficiently increased in the pulse pressure increasing mode, the ABS control is stopped and FIG. In other words, when the driver increases the wheel cylinders 2FL to 2RR
Return to the state where the hydraulic pressure of can be adjusted.

Rear Wheel Braking Force Control Next, regarding the processing when the driver performs a braking operation (braking operation), the start determination processing of the rear wheel braking force control in FIG. 4 and the end determination of the rear wheel braking force control in FIG. A description will be given based on a flowchart of the processing. These processes are repeatedly executed.

First, in the rear wheel braking force control start determination processing of FIG. 4, it is determined whether or not the ABS control has been performed (S11).
0). If the ABS control is being performed ("NO" in S110),
The output (S120) by the normal ABS control is performed.
If ABS control is not being performed ("YE" in S110)
S "), and it is determined whether or not the ABS control is permitted (S130). The ABS control permission state means a state in which the stop switch 36 is on and the system can operate normally (for example, a state in which the solenoid of the hydraulic circuit 40 normally drives). The ABS control permission state is repeatedly checked by the ECU 20, and is determined by referring to the check result.

If the ABS control is not permitted (S130)
, “NO”), and the process ends as it is. If the ABS control is permitted ("YES" in S130), it is next determined whether or not the rear wheel braking force control is already being performed (S140). If the rear wheel braking force is being controlled ("YES" in S140), the process ends.

If the rear wheel braking force control is not being performed ("NO" in S140), the pressure (M / C) of the master cylinder 34 is then determined based on the value detected by the master cylinder pressure sensor 38.
(S) is 40 kgf / cm2 or more (S).
150). If M / C pressure <40 kgf / cm2 (S
150 "NO"), front wheels FL, FR and rear wheels RL, RR
Since this is not a braking state in which it is necessary to provide a differential pressure to the brake oil pressure, the process ends as it is.

If M / C pressure ≧ 40 kgf / cm 2 (“YES” in S150), the deceleration Gx in the longitudinal direction of the vehicle is set to 0.75G based on the value detected by the G sensor 14.
It is determined whether or not the vehicle is in a decelerating state by applying a braking force (S160). This is performed for fail-safe purpose. The deceleration of the vehicle is checked to determine whether or not the deceleration is equal to or greater than the value achieved during braking when the road surface is dry.

If Gx <0.75G ("NO" in S160), the process ends. Gx ≧ 0.75
If it is G ("YES" in S160), then a braking state is determined (S170). That is, the amount of time change of the detection value of the master cylinder pressure sensor 38 is checked, and
As shown in FIG. 6, when increasing (+), it is determined that the pedal is in the depressed state, and when it is decreasing (−), it is determined that it is in the depressed state, and the state where neither increase nor decrease or increase is decreased. Is determined as a fixed state.

If it is determined that the vehicle is in the stepping-on state, the rear wheels RL and RR of the hydraulic circuit 40 are switched to the same state as the pulse pressure increasing mode described in the ABS control, and the pressure increasing control valve 46RL. , 46RR, the period T
1, duty (t1 / T1) obtained from FIG. 6 ×
A pulse pressure increase output for outputting a 100% pressure increase pulse as shown in FIG. 8A is executed. As a result, in the wheel cylinders 2RL, 2RR of the rear wheels RL, RR, the brake hydraulic pressure increases at a speed proportional to the duty of the pressure increase pulse.

When it is determined in step S170 that the hydraulic circuit 40 is in the fixed state, the rear wheels RL and RR of the hydraulic circuit 40 are moved to the pressure increasing control valves 46RL and 46RR and the pressure reducing control valves 48RL and 48R.
R together with each other, and as shown in the holding mode of FIG.
/ C pressure is maintained. Therefore, in the fixed state, the hydraulic pressure of both rear wheels RL and RR does not increase or decrease.

When it is determined in step S170 that the vehicle is in the depressed state, the rear wheels RL and RR of the hydraulic circuit 40 are switched to the same state as in the pressure reduction mode described in the ABS control, and the pressure reduction control valve is controlled. 48RL, 48RR
In the cycle T2, the duty (t2
/ T2) × 100% pulse pressure reduction output for outputting a pressure increase pulse as shown in FIG. 8B is executed. As a result, the wheel cylinders 2RL, 2R of both rear wheels RL, RR
At R, the brake oil pressure decreases at a speed proportional to the duty of the pressure reduction pulse.

In this manner, the wheel cylinder 2R on the rear wheels RL and RR at a speed corresponding to the master cylinder pressure fluctuation caused by the driver's operation of the brake pedal 32.
L and 2RR brake hydraulic pressures are adjusted. Note that the state in which the processes of steps S170 to S200 are being executed corresponds to a state in which the rear wheel braking force is being controlled.

Next, the rear wheel braking force control end determination processing of FIG. 5 will be described. First, it is determined whether or not the rear wheel braking force control is being performed (S210). If the rear wheel braking force control is not being performed ("NO" in S210), the process ends. If the rear wheel braking force is being controlled ("YE" in S210)
S "), and it is determined whether the ABS control is being performed (S220). If ABS control is being performed ("Y" in S220)
ES "), a normal ABS output is performed (S230).

If the ABS control is not being performed ("N" in S220)
O "), the master cylinder (M / C) pressure is 30 kgf /
It is determined whether it is less than cm2 (S240). If M
/ C pressure <30 kgf / cm2 ("Y" in S240
ES "), since the brakes of the front wheels FL and FR and the rear wheels RL and RR are out of the braking state in which a differential pressure needs to be provided, the pressure increase of both rear wheels RL and RR shown in FIG. The state of the hydraulic circuit 40 is returned to the same state as the mode (S25
0).

If M / C pressure ≧ 30 kgf / cm 2 (“NO” in S 240), then M / C pressure ≧ 40 kgf
/ Cm2 (S260). Where M
If / C pressure ≧ 40 kgf / cm 2 (“NO” in S260), that is, if 30 kgf / cm 2 ≦ M / C pressure <40 kgf / cm 2, the process is terminated as it is, and the rear wheel braking force control is continued.

If M / C pressure ≧ 40 kgf / cm 2 (“YES” in S260), it is next determined whether or not deceleration Gx in the vehicle longitudinal direction is less than 0.3G (S27).
0). If Gx ≧ 0.3G (“N” in S270
O "), assuming that it is normal, the process is terminated as it is, and the rear wheel braking force control is continued. If Gx <0.3G ("YES" in S270), it is determined that the corresponding deceleration has not occurred in the vehicle despite the existence of a sufficient M / C pressure, and both rear wheels are immediately determined. RL and RR are returned to the normal pressure increase mode (S250), and the process is terminated.

Since the present embodiment is configured as described above, as shown in the timing chart of FIG. 9, when the driver operates the brake pedal 32 to increase or decrease the M / C pressure, First, until the M / C pressure becomes 40 kgf / cm2, the brake hydraulic pressure increases at the same W / C pressure for the front wheels FL, FR and the rear wheels RL, RR.
At 0 kgf / cm2 (time t01 to t02), the rear wheel braking force control process is started, and it is determined that the vehicle is being depressed, and the W / C pressure on the rear wheel side is changed according to the time variation of the M / C pressure. Increase. The M / C pressure is transmitted to the front wheel side as it is. Therefore, the W / C pressure on the rear wheel side increases at a position lower than the W / C pressure on the front wheel side indicated by the solid line, as shown by the one-dot chain line.

When the time variation of the M / C pressure becomes small and it is determined that the M / C pressure is in the fixed state (time t02 to t03), the rear wheel W / W /
C pressure becomes constant. In addition, the driver operates the brake pedal 32
When the M / C pressure decreases and the vehicle returns to the stepped state (time t03 to t04), the W / C pressure on the rear wheel side becomes M / C.
The C pressure decreases in accordance with the time change amount. Thereafter, after the driver performs the operation of completely returning the brake pedal 32 after the fixed state (time t04-05), the depressed state (time t05-06), and the fixed state (time t06-07), the depressed state is entered. (Time t07-t08), it decreases toward M / C pressure = 0.

During this time (time t01 to t08), W /
The C pressure shows a variation similar to the front wheel side W / C pressure at a position lower than the front wheel side W / C pressure. And M / C
When the pressure becomes <30 kgf / cm2 (time t08),
Both the front wheel side and the rear wheel side are in the pressure increase mode, and the front wheel side W /
The C pressure is equal to the rear wheel W / C pressure. Note that during the operation period of the brake pedal 32 shown in FIG. 9, it is assumed that the ABS control is not entered.

Since the present embodiment is configured as described above, the front wheel side W is controlled only by the ECU 20 using the hydraulic circuit 40 used for the ABS control without providing a special valve or the like. A difference that stabilizes the vehicle during braking can be provided between the / C pressure and the rear wheel side W / C pressure.

As shown in FIG. 6, if the time variation of the operation amount of the brake pedal 32 in the depressed state is large, the duty of the pressure increasing pulse is increased to supply the brake hydraulic pressure to the rear wheel side. When the rate of change is small and the time variation of the operation amount of the brake pedal 32 is small, the rate of supply of the brake hydraulic pressure to the rear wheel side is reduced. For this reason, a change in the rear wheel braking force can be caused in accordance with the strength of the braking operation by the driver, and the shortage of the braking performance and the deterioration of the braking feeling are not caused.

Further, the brake pedal 3 in the depressed state is
If the amount of time change of the operation amount is large, the duty of the pressure reduction pulse is increased to increase the discharge rate (decrease rate) of the brake hydraulic pressure from the rear wheel side, and the brake pedal 32
If the amount of time change of the operation amount is small, the discharge rate of the brake hydraulic pressure from the rear wheel side is reduced. As a result, even when the driver relaxes the braking operation, the braking force on the rear wheel side also decreases in accordance with the degree of return of the braking operation, so that the braking feeling is not impaired.

The fact that the driver is operating the brake pedal 32 by a predetermined amount or more is detected at the level of the M / C pressure (in the embodiment, the predetermined amount = 40 kgf / cm 2).
When it is detected that the amount is equal to or more than the predetermined amount, the rear wheel braking force control is started. Therefore, the difference between the braking force on the front wheel side and the braking force on the rear wheel side can be ensured in the case of the braking force in which the vehicle stability is a problem, and the low braking is performed in the case of low braking in which the vehicle stability is not a problem. Sometimes necessary braking force can be secured.

In this embodiment, the hydraulic circuit 40 corresponds to the wheel braking force adjusting mechanism, the master cylinder pressure sensor 38 corresponds to the braking operation detecting means,
S200 corresponds to processing as rear wheel braking force adjustment means,
Step S150 corresponds to processing as braking operation determination means.

[Others] In the above embodiment, the braking operation of the driver is detected by the master cylinder pressure sensor 38 as the braking operation detecting means. Equipped with a stroke sensor that detects the depression stroke,
The operation state of the brake pedal 32 may be detected from a depression stroke detected by a stroke sensor.

Further, instead of the stroke sensor, a depression force sensor for detecting the depression force of the brake pedal 32 may be provided, and the operation state of the brake pedal 32 may be detected from the depression force detected by the depression force sensor.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a configuration of an entire braking force control system of an automobile as an embodiment.

FIG. 2 is a diagram illustrating a configuration of a hydraulic circuit of a braking force control system according to an embodiment.

FIG. 3 is a timing chart illustrating ABS control performed by an ECU as one embodiment.

FIG. 4 is a flowchart of a rear wheel braking force control start determination process executed by an ECU as one embodiment.

FIG. 5 is a flowchart of a rear wheel braking force control termination determination process executed by an ECU as one embodiment.

FIG. 6 is a graph for explaining the relationship between the amount of change in the M / C pressure and the duty on the pressure increase / pressure reduction side.

FIG. 7 is an explanatory diagram of each control mode of braking.

FIG. 8 is an explanatory diagram of a pressure increasing side and a pressure decreasing side duty.

FIG. 9 is a timing chart illustrating an example of a process.

[Explanation of symbols]

FL: Left front wheel FR: Right front wheel RL: Left rear wheel RR: Right rear wheel 2FL, 2FR, 2RL, 2RR: Wheel cylinder (W / C) 4FL, 4FR, 4RL, 4RR: Wheel speed sensor 14: G sensor 20 ... ECU 32 brake pedal 34 master cylinder (M / C) 36 stop switch (STP) 38 master cylinder pressure sensor 40 hydraulic circuit 42, 44 hydraulic path 46FL, 46FR, 46RL, 46RR pressure increase control valve 48FL , 48FR, 48RL, 48RR ... pressure reducing control valve 50a, 50b ... SM valve 54a, 54b ... relief valve 56, 58 ... reservoir 60, 62 ... pump 64, 66 ... accumulator 70a, 70b ... SR
Valve 80: Motor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60T 8/26 B60T 8/58

Claims (9)

(57) [Claims] 1. A rear vehicle which is used in a vehicle having a wheel braking force adjusting mechanism for adjusting, as necessary, an increase and a decrease in a braking force supplied to at least a rear wheel side based on a braking operation. A wheel braking force control device, comprising: a braking operation detecting means for detecting a braking operation of a driver; and a time change when the time change of the braking operation amount detected by the braking operation detecting means is a stepping side. In response to the,
If the time change amount is large, the supply rate of the braking force to the rear wheel by the wheel braking force adjustment mechanism is increased, and if the time change amount is small, the braking force to the rear wheel side by the wheel braking force adjustment mechanism is increased. a wheel braking force adjusting means after reducing the feed rate, Bei give a, the rear wheel braking force adjusting means, the time of braking operation quantity detected by the brake operation detecting means
If the change is on the stepping side, according to the time change,
If the amount of time change is large, the wheel braking force adjusting mechanism
Increase the supply rate of braking force to the rear wheel side
If it is smaller, the wheel braking force adjustment mechanism
The braking force supply rate is reduced, and the time of the braking operation amount detected by the braking operation detecting means is reduced.
When the change is on the return side, according to the time change,
If the amount of time change is large, the wheel braking force adjusting mechanism
Increase the rate of decrease in braking force on the rear wheel side
If smaller, the wheel braking force adjustment mechanism
A rear wheel braking force control device for a vehicle, wherein a reduction rate of a braking force is reduced . 2. At least a rear wheel side based on a braking operation
Increase and decrease of the braking force supplied to
Used for vehicles with a wheel braking force adjustment mechanism that adjusts
A rear wheel braking force control device for a vehicle , comprising: braking operation detecting means for detecting a driver's braking operation; and a time of a braking operation amount detected by the braking operation detecting means.
If the change is on the stepping side, according to the time change,
If the amount of time change is large, the wheel braking force adjusting mechanism
Increase the supply rate of braking force to the rear wheel side
If it is smaller, the wheel braking force adjustment mechanism
Rear wheel braking force adjusting means for reducing the supply rate of the braking force , wherein the wheel braking force adjusting mechanism is configured to control the braking operation of the driver when the braking force on the rear wheel is increased.
Transmission of brake fluid pressure to the rear wheel side
Perform braking force increase processing that appropriately executes shut-off, and
Decrease in the braking force
Braking force reduction processing that appropriately executes discharge and cutoff
The rear wheel braking force adjusting unit is configured to control the time of the braking operation amount detected by the braking operation detecting unit.
If the change is on the stepping side, according to the time change,
If the time change amount is large, the braking force increase process
If you increase the proportion of the transmission period and the amount of time change is small,
Reduce the ratio of the transmission period in the braking force increase process
A rear wheel braking force control device for a vehicle. 3. When the time change of the braking operation amount detected by the braking operation detecting means is on the stepping-back side, the rear wheel braking force adjusting means changes the time change amount in accordance with the time change. 3. The vehicle according to claim 2 , wherein the ratio of the discharge period in the braking force reduction process is increased if the ratio is large, and the ratio of the discharge period in the braking force reduction process is reduced if the amount of time change is small. Wheel braking force control device. 4. A braking operation determining means for determining whether or not a driver has performed a braking operation of a predetermined amount or more based on a detection result of the braking operation detecting means. 2. The control device according to claim 1, wherein the braking operation determining unit performs a process as the rear wheel braking force adjusting unit when it is detected that the driver performs a braking operation of a predetermined amount or more. 4. The rear wheel braking force control device according to any one of claims 1 to 3 , wherein Wherein said brake operation detecting means, wheel braking force control apparatus after the vehicle according to any one of claims 1-4 for detecting a braking operation by detecting an operation state of the brake pedal. 6. A master cylinder pressure sensor for detecting a pressure of a master cylinder which generates a brake fluid pressure by operating the brake pedal, wherein an operation state of the brake pedal in the braking operation detecting means is controlled by the master cylinder pressure sensor. The rear wheel braking force control device according to claim 5 , wherein the detection is performed from the pressure detected by the vehicle. 7. A stroke sensor for detecting a depression stroke of the brake pedal, wherein an operation state of the brake pedal in the braking operation detection means is detected from a depression stroke detected by the stroke sensor. The rear wheel braking force control device according to claim 5 . 8. A depressing force sensor for detecting a depressing force of the brake pedal, wherein an operation state of the brake pedal by the braking operation detecting means is detected from a depressing force detected by the depressing force sensor. The rear wheel braking force control device according to claim 5 . 9. The wheel braking force adjustment mechanism is started when a wheel slip greater than or equal to a predetermined value is detected during braking of the vehicle, and adjusts the braking force applied to the wheels to achieve high deceleration according to road surface conditions. The rear wheel braking force adjustment means functions when the braking force control is not performed, while also functioning as a wheel braking force adjustment mechanism in the braking force control to be generated.
9. The rear wheel braking force control device according to any one of claims 8 to 8 .