JP3141623B2 - Braking force distribution control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a proportioning valve for suppressing a rise rate of a rear wheel cylinder pressure accompanying an increase in a master cylinder pressure and a bypass valve provided in a pipe for bypassing the proportioning valve. The present invention relates to a braking force distribution control method for appropriately distributing a front wheel braking force and a rear wheel braking force, and more particularly to a method capable of ensuring an appropriate braking force distribution regardless of a driver's depressing operation speed of a brake pedal.

[0002]

2. Description of the Related Art A brake system mounted on a vehicle includes a master cylinder for generating brake fluid pressure in accordance with the amount of depression of a brake pedal, and a wheel cylinder mounted on each wheel of the vehicle. Pressure (brake fluid pressure generated by the master cylinder) is transmitted to each wheel cylinder to apply a braking force to each wheel. In such a brake system, when the master cylinder pressure is distributed to the front wheel cylinder and the rear wheel cylinder with almost the same distribution, when a large braking force is applied to each wheel, the deceleration of the vehicle increases and the rear wheel load increases. And the ground contact of the rear wheels is reduced, the rear wheels are locked first, and the braking stability of the vehicle may be degraded.

[0003] In order to solve the above-mentioned problem, a proportioning valve (PCV) is conventionally incorporated in a brake system, and when the braking force, that is, the master cylinder pressure is small, the master cylinder pressure is directly used as a wheel cylinder for the rear wheels. On the other hand, when the master cylinder pressure becomes equal to or higher than the set pressure, the rate of increase of the rear wheel cylinder pressure (master cylinder pressure transmitted to the wheel cylinder of the rear wheel) accompanying the increase of the master cylinder pressure is reduced. .

Further, until the master cylinder pressure reaches a target pressure higher than the above set pressure, a bypass valve provided in a pipe bypassing the proportioning valve is opened to deactivate the proportioning valve, while the master cylinder pressure is deactivated. When the pressure exceeds a set pressure, a rear wheel braking force control device has been proposed in which a bypass valve is closed and a proportioning valve is used to optimize braking force distribution (Japanese Patent Application No. 3-315660).

Further, there has been proposed an apparatus which permits or prevents the supply of brake fluid pressure from the master cylinder to the wheel cylinder in accordance with the deceleration of the vehicle detected by the deceleration sensor, thereby obtaining an appropriate rear wheel braking force. (Japanese Patent Laid-Open No. 58-
105862). Accordingly, in the above-described rear wheel braking force control device including the proportioning valve and the bypass valve, opening and closing of the bypass valve according to the deceleration of the vehicle may be considered. In this case, when the actual deceleration detected by the acceleration sensor reaches the target deceleration, the bypass valve is switched from the open state to the closed state. If the intended braking force can be generated in each of the front wheel wheel cylinder and the rear wheel wheel cylinder at the time of this bypass valve switching operation, appropriate braking force distribution is realized.

[0006]

However, in the brake system, the transmission of the brake fluid pressure from the master cylinder to the front and rear wheel cylinders is performed via a brake pipe or the like. The brake pipe resistance between the wheel cylinders is greater than the brake pipe resistance between the master cylinder and the front wheel cylinders. Therefore, a change in brake fluid pressure on the rear wheel side with respect to the depression operation of the brake pedal is slower than a change in hydraulic pressure on the front wheel side. The response delay on the rear wheel side becomes more remarkable as the speed of the brake pedal depressing operation increases, and the contribution of the front wheel side brake increases as the brake pedal depressing speed increases.

In the braking force distribution control device of the type described above, which performs the switching operation of the bypass valve according to the result of comparison between the actual deceleration and the target deceleration, the brake pedal is mainly depressed at a high speed. Even when the deceleration increases due to the contribution of the front wheel side brake, when the actual deceleration reaches the target deceleration, the bypass valve is switched and the rear wheel braking force is suppressed by the proportioning valve. At this time, the rear wheel side brake does not significantly contribute to the generation of the braking force, and therefore, the rear wheel braking force has not reached the level to be suppressed. That is, if the switching operation timing of the bypass valve is advanced as the brake pedal operation speed increases, appropriate braking force distribution between the front wheel side and the rear wheel side will be hindered.

On the other hand, when the brake pedal is depressed at a speed much higher than the normal brake operation speed, such as during panic braking, if the distribution of braking force to the rear wheels is increased, the rear There is a possibility that a problem of locking the wheel tip occurs. Therefore, an object of the present invention is to optimize the distribution of the front wheel braking force and the rear wheel braking force by controlling the opening and closing of a bypass valve provided in a pipe bypassing the proportioning valve according to the deceleration of the vehicle, It is an object of the present invention to provide a braking force distribution control method capable of ensuring an appropriate braking force distribution regardless of the speed at which a driver steps on a brake pedal.

[0009]

SUMMARY OF THE INVENTION A braking force distribution control method according to one aspect of the present invention controls opening and closing of a bypass valve provided in a pipe bypassing a proportioning valve, thereby reducing the degree of increase in the master cylinder pressure. a adjusts the rear wheel braking force selectively enable and the function of suppressing proportioning valve to increase the degree of the rear wheel wheel cylinder pressure, to detect the braking deceleration, the detected braking deceleration change rate And the rate of change in braking deceleration increases
As the target deceleration increases as that, the target deceleration is variably set in accordance with the braking deceleration of the rate of change, or opened the bypass valve when the detected braking deceleration reaches the target deceleration
Characterized in that the opening and closing control to switch to Luo closed
And

Preferably, the target deceleration is reduced when the rate of change of the braking deceleration is equal to or greater than a predetermined value. A braking force distribution method according to another aspect of the present invention is to selectively enable a function of a proportioning valve by opening and closing a bypass valve to adjust a rear wheel braking force,
Table By such that the output of the phase of the acceleration sensor is delayed, the acceleration sensor output and the phase-lag compensation, the phase lag compensated acceleration sensor output as to detect the braking deceleration by the acceleration sensor, the braking deceleration of the rate of change increases The bypass valve is open when the braking deceleration reaches the target deceleration .
Characterized in that the opening and closing control to switch to Luo closed
And

Preferably, when the rate of change of the braking deceleration is equal to or greater than a predetermined value, the output of the acceleration sensor is not phase-lag compensated.

[0012]

During braking, a braking deceleration is detected by, for example, an acceleration sensor, and then a rate of change of the braking deceleration with respect to a time axis is obtained. Further, the target deceleration is variably set according to the deceleration change rate. For example, the target deceleration is set so that the target deceleration increases as the rate of change of the braking deceleration increases. Alternatively, the phase delay of the acceleration sensor output is compensated so that the phase of the acceleration sensor output is delayed as the rate of change of the braking deceleration increases.

When the driver depresses the brake pedal, the vehicle continues to run against the braking forces generated by the front and rear wheel cylinders, in other words, the braking reduction detected by the acceleration sensor. The speed is smaller than the target deceleration. In this case, regarding the rear wheel side brake, the bypass valve is opened, the proportioning valve is deactivated, and the master cylinder pressure is directly supplied to the rear wheel cylinder via the bypass valve. Therefore, the rear wheel braking force is not suppressed.

As a result of setting the target deceleration or compensating for the phase lag of the output of the acceleration sensor as described above, if the brake depression speed is high, the switching operation timing of the bypass valve from the open state to the closed state is delayed. Will be.
Therefore, while the contribution of the front wheel side brake is large and the intended rear wheel braking force has not yet been generated, the rear wheel braking force is not suppressed by the switching operation of the bypass valve, that is, the operation of the proportioning valve, Therefore, the optimization of the braking force distribution is not hindered.

Thereafter, while the switching operation of the bypass valve is delayed, the intended rear wheel braking force is generated. After the braking deceleration reaches the target deceleration, the bypass valve is closed, and the supply of brake fluid pressure from the master cylinder pressure to the rear wheel cylinder is performed via the proportioning valve. As a result, the rate of increase of the rear wheel cylinder pressure is reduced, and appropriate braking force distribution after reaching the target deceleration is realized.

Preferably, when the rate of change of the braking deceleration is equal to or greater than a predetermined value, the target deceleration is reduced, or the output of the acceleration sensor is not phase-lag compensated. Thus, for example, in a panic brake region in which the brake operation is performed at a large speed exceeding the practical braking speed, the switching operation of the bypass valve is not delayed, and thus the rear wheel front lock is prevented.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the drawings, a brake system equipped with a braking force distribution control device for performing a method according to a first embodiment of the present invention will be described below. In FIG. 1, a brake system uses a booster 1
2, and the amplified stepping force is transmitted to the tandem master cylinder 13. The master cylinder 13 includes two hydraulic pressure generating units (not shown) for generating a brake hydraulic pressure according to the amount of depression of the brake pedal 11. One of the hydraulic pressure generating units cooperates with an element described later to form an anti-skid brake system (hereinafter referred to as AB).
S) is connected to a wheel cylinder 161 of the left front wheel via a pipe 15 to which an ABS valve 14 constituting the ABS valve 14 is attached.
7 and a proportioning valve (hereinafter referred to as PCV) 182 are connected to a wheel cylinder 164 of the right rear wheel via a pipe 19 to which the component is attached. Similarly, the other hydraulic pressure generating section is connected to the pipe 2 to which the ABS valve 20 is attached.
1 is connected to a wheel cylinder 162 of the right front wheel, and is branched from the middle of the pipe 21 to the ABS valve 22.
And the pipe 23 to which the PCV 181 is attached,
It is connected to the wheel cylinder 163 of the left rear wheel.

The PCVs 181 and 182 are composed of conventionally known proportioning valves. When the master cylinder pressure, that is, the braking force is small, the master cylinder pressure is transmitted to the wheel cylinders of the rear wheels without change, and when the master cylinder pressure exceeds a set pressure. And functions to reduce the rate of increase of the rear wheel cylinder pressure due to the increase of the master cylinder pressure. A bypass pipe 24 is provided between the upstream side and the downstream side of the PCV 181. Similarly, a bypass pipe 25 is provided between the upstream side and the downstream side of the PCV 182. The bypass pipes 24 and 25 are provided with bypass valves 26 and 27, each of which is a normally-closed electromagnetic on-off valve.

The brake system includes a brake switch 30 for detecting whether or not the driver depresses the brake pedal 11, and wheel speeds VFL, VFR, VRL and VRR of the front left wheel, front right wheel, rear left wheel and rear right wheel. Wheel speed sensors 31, 32, 33 and 34 for detecting
The ABS valve 1 includes a vehicle speed sensor 35 for detecting the vehicle speed, a microcomputer and its peripheral circuits.
An ABS controller 36 for driving and controlling 4, 20, 22, and 17 is further provided. The ABS controller 36 calculates a slip ratio for each wheel based on the wheel speed sensor outputs VFL, VFR, VRL, VRR and the vehicle speed sensor output V, and generates an ABS signal a having a signal level corresponding to the calculated slip ratio.
1 to a4 are output to the ABS valves 14, 20, 22, and 17. The ABS signals a1 to a4 are, depending on their signal levels, pressure-increasing signals for injecting brake fluid into the wheel cylinders 161 to 164 or the wheel cylinder 1
It functions as a holding signal for holding the brake fluid stored in 61 to 164 or a pressure reducing signal for removing the brake fluid from the wheel cylinders 161 to 164. When the wheel slip ratio exceeds a predetermined value, a holding signal is transmitted first, and then a pressure reduction signal is transmitted.

The braking system includes a vehicle speed sensor 35 and a front and rear G as an acceleration sensor for detecting a braking deceleration G.
Sensor 38, steering angle sensor 39 for detecting steering wheel angle Hθ, PCVs 181 and 182, and bypass valves 26 and 2
And a controller 37 constituting a braking force distribution control device in cooperation with the control device 7. The controller 37 is composed of a microcomputer and its peripheral circuits, and is configured to bypass the ABS signals a1 to a4 from the ABS controller 36, the vehicle speed sensor output V, the front and rear G sensor output G, the steering angle sensor output Hθ, and the brake switch output b. Valve 26, 2
7 is controlled independently and independently.

The operation of the braking force distribution control device for a brake system having the above configuration will be described below with reference to FIGS. When the ignition key of the vehicle equipped with the brake system is turned on, the controller 37 starts the bypass valve opening / closing control routine of FIGS. 2 and 3. The opening / closing control of the bypass valves 26 and 27 is performed in the same procedure. Hereinafter, the opening / closing control procedure of the left rear wheel bypass valve 26 will be mainly described.

In the bypass valve opening / closing control routine, the controller 37 first determines whether or not the brake switch 30 has been turned on based on the brake switch output b (step S1). If the result of this determination is negative, that is, if the braking operation by the brake system in FIG. 1 has not been performed, the determination in step S1 is performed again. Thereafter, when it is determined in step S1 that the brake switch 30 is turned on to start the braking operation of the brake system, the controller 37 initializes the target longitudinal acceleration (target deceleration) at which the open / close state of the bypass valve 26 should be switched. The value GO is set (step S2). Therefore, for example, the controller 3
Reference numeral 7 reads an initial value GO previously stored in a first memory area of a memory built in the controller and stores it in a second memory area. The initial value GO is set to an appropriate value so that the rear wheel lock is not distributed under normal braking conditions.

Next, the controller 37 reads the front and rear G sensor output G, stores the sensor output data in a memory (step S3), and calculates a differential value GS of the front and rear G sensor output G based on the sensor output data. And store it in the memory (step S4). In calculating the differential value GS representing the rate of change (gradient) of the braking deceleration with respect to the time axis, the controller 37 uses, for example, the difference between the sensor output data in the current control cycle and that in the previous cycle as the differential value GS. Ask. Then, the sensor output data of the current cycle is transferred to a predetermined memory area for calculating a differential value in the next cycle.

In step S5, the controller 37
Determines whether the differential value GS of the front and rear G sensor output is 4 G / sec or more. If the determination result is negative and it is determined that the brake pedal 11 has been depressed at a stepping speed corresponding to a braking speed smaller than the upper limit value 4 G / sec of the practical braking speed region, the controller 37 outputs the front and rear G sensor output G. (Step S6 in FIG. 3).

In the low-pass filter processing, for example,
The controller 37 calculates the sum of N times the low-pass filtered front and back G sensor output data obtained in the previous cycle and the front and back G sensor output data of the current cycle as “N
By dividing by +1 ", the low-pass filtered front and rear G sensor output data of the current cycle are obtained and stored in the memory. By this low-pass filter processing, the front and rear G
The phase delay of the sensor output G is compensated so that the larger the frequency is, the more the phase is delayed (FIG. 4).

In step S7, the controller 37
Performs various corrections on the initial value GO of the target deceleration in order to obtain the target deceleration suitable for the traveling environment. In this embodiment, a horizontal G correction is performed on the initial value GO. Therefore, the controller 37 sequentially reads the longitudinal G sensor output G, the vehicle speed sensor output V, and the steering angle sensor output Hθ, and stores the sensor output data in the memory. And the controller 37
Calculates a calculated lateral acceleration as an estimated value of the lateral acceleration applied to the vehicle body based on the vehicle speed sensor output data V and the steering angle sensor output data Hθ read from the memory, and then corresponds to the calculated value and is not shown. The corrected target deceleration GC for the left rear wheel is obtained by multiplying the correction coefficient obtained from the map by the initial value GO of the target deceleration read from the memory. Various corrections including the horizontal G correction will be described later in detail in the description of the control procedure according to the second embodiment of the present invention.

Next, the controller 37 determines that the braking deceleration GF subjected to the low-pass filter processing is equal to the corrected target deceleration GC
It is determined whether or not this is the case (step S8). Since the braking deceleration is small at the beginning when the brake pedal is depressed, the determination result in step S8 is negative. In this case, the controller 37 sends, for example, a high-level control output to the normally-closed bypass valve 26 to open the bypass valve 26 (step S9), and ends the bypass valve opening / closing control process in the current cycle. As a result, the bypass pipe 24 is opened, and the brake fluid pressure from the master cylinder 13 is reduced by the pipe lines 21, 23, the ABS valve 22, and the PCV 18
It is supplied to a wheel cylinder 163 of the left rear wheel via a bypass pipe 24 provided to bypass 1. As a result, the wheel cylinder 163 generates a larger braking force than when brake fluid pressure is supplied via the PCV 181.

In the next and subsequent cycles, the above-described series of steps S1 to S9 are repeatedly executed, thereby generating a left rear wheel braking force. Right rear wheel bypass valve 2
7, the same opening / closing control as in the case of the left rear wheel bypass valve 26 is executed, whereby a right rear wheel braking force is generated.
Further, the master cylinder pressure is supplied to the front wheel cylinders 161 and 162 to generate a front wheel braking force. As a result, the braking deceleration increases.

In step S8 of the subsequent cycle, when it is determined that the low-pass filtered front and rear G sensor output GF representing the braking deceleration is equal to or higher than the corrected target deceleration GC, the controller 37 sends a low-speed signal to the bypass valve 26. The control output of the level is sent out to close the bypass valve 24 to close the bypass valve 24 (step S10).
In this case, the brake fluid pressure from the master cylinder 13 is supplied to the wheel cylinder 163 via the pipes 21, 23 and the ABS valve 22 and the PCV 181, and the PCV 1
The brake fluid pressure increase rate suppressing function of 81 is performed, and as a result, the rear wheel braking force is suppressed as compared with the case where the brake fluid pressure is supplied via the bypass pipe 24.

Next, the controller 37 determines whether or not the brake switch 30 has been turned off (step S1).
1) If the result of this determination is negative, step S10 is executed again. If it is determined in step S11 of the subsequent cycle that the brake switch 30 has been turned off, the controller 37 opens the bypass valve 26 (step S9). Then, the bypass valve opening / closing control process returns to step S1.

As described in the "Explanation" section above, particularly when the brake pedal depressing operation speed is high and the braking deceleration increases mainly due to the contribution of the front wheel side brake, the intended rear wheel braking force is generally considered. The switching operation of the bypass valves 26 and 27 is performed before the occurrence of. That is, under a normal braking condition in which the change gradient of the braking deceleration is 0 to 4 G / sec, generally, the rear wheel braking force (rear wheel pressure) at the time of the switching operation of the bypass valve has a large deceleration gradient. (See FIG. 5). In other words, the higher the brake depression speed, the earlier the bypass valve switching operation timing. In FIG. 5, the chain line represents the intended rear wheel pressure.

In order to correct the deterioration of the braking force distribution due to the excessively advanced switching operation timing of the bypass valve, in the present embodiment, the low-pass filter processing of the filter characteristics shown in FIG. 4 is performed as described above. As a result of the low-pass filter processing being performed on the front and rear G sensor output G, the timing of the switching operation of the bypass valves 26 and 27 is delayed. Moreover, as the brake depressing speed increases and the braking deceleration gradient increases, the degree of the switching operation timing delay increases. As a result, the braking speed is 0 to 4 G /
Within the normal braking range of seconds, the bypass valves 26, 27
Is switched from the open state to the closed state, the rear wheel pressure (shown by a solid line in FIG. 6) becomes larger than the rear wheel pressure (shown by a broken line in FIG. 6) when the low-pass filter processing is not performed. In other words, the braking speed corresponding to the normal braking range-
The rear wheel pressure characteristic becomes flat, and therefore, appropriate braking force distribution can be achieved regardless of the brake depression speed. In FIG. 6, the dashed line indicates the intended rear wheel pressure, and the dashed two-dotted line indicates an imaginary extension of the solid line.

However, when the normal braking range is exceeded,
If the distribution of the braking force to the rear wheel side is increased, the rear wheel may be locked. If it is determined in step S5 that the differential value GS of the front and rear G sensor output is 4 G / sec or more and out of the normal braking range, the controller 37
Prohibits low-pass filtering of the front and rear G sensor output G. That is, if the determination result in step S5 is affirmative, the controller 37 corrects the initial value GO of the target deceleration in step S12 corresponding to step S6, and then outputs the front-rear G sensor output G representing the braking deceleration. Is greater than or equal to the corrected target deceleration GC (step S13). In accordance with this determination result, the controller 37 opens the bypass valve 26 until the braking deceleration reaches the target deceleration, and closes the bypass valve during one braking operation when the braking deceleration exceeds the target deceleration (step S9).
To S11). As a result, when the brake pedal is depressed at a very high speed beyond the normal braking range, the bypass valve switching operation timing is not delayed by the low-pass filter processing, and the rear wheel pressure at the time of the bypass valve switching operation is reduced. As shown on the right side of FIG. 6, the braking force is greatly reduced as compared with the case of the normal braking condition, whereby the rear wheel tip lock is reliably prevented.

Opening / closing control of the right rear wheel bypass valve 27 is performed in the same manner as the bypass valve 26. In this way, by performing the opening and closing control of the bypass valves 26 and 27 of the left and right rear wheels independently of each other, the braking force of the left and right rear wheels becomes optimal even when the vehicle is turning, for example. Further, the braking deceleration G detected by the front and rear G sensor 38 also reflects the loading situation in the vehicle, and the bypass valve opening / closing control is appropriately performed according to the comparison result between the braking deceleration and the target deceleration, Therefore, it is not necessary to correct the braking deceleration G according to the loading situation. Further, when the braking force distribution control device is operated using the target deceleration GC set to an appropriate value, the bypass valves 26 and 27 are closed so that the bypass valves 26 and 27 are closed before the simultaneous deceleration state of the four wheels occurs. The drive is controlled, thereby preventing the simultaneous deceleration of the four wheels from occurring. Therefore,
An ABS operation delay that is likely to occur when the braking force distribution control device and the ABS are used in combination is prevented.

Hereinafter, a method of controlling a rear wheel braking force according to a second embodiment of the present invention will be described. In order to correct the switching operation timing of the bypass valves 26 and 27 when the braking deceleration gradient increases, the output of the front and rear G sensors is compensated for the phase delay, and the initial value of the target deceleration is corrected by the lateral G in the first embodiment. Thus, the present embodiment is characterized in that the target deceleration is increased and corrected as the braking deceleration gradient increases to correct the bypass valve operation timing, and that the initial value of the target deceleration is variously corrected according to the traveling environment. Are different.

The basic configuration of an apparatus for carrying out the method of this embodiment is the same as that shown in FIG. 1, and a detailed description of the apparatus will be omitted. However, in connection with the differences described above,
The device used in this embodiment includes an outside air temperature sensor 41 and a wiper switch 42 in addition to the brake switch 30 and the sensors 31 to 35, 38, and 39 shown in FIG.

Hereinafter, the control contents of the controller 37 will be described. Referring to FIG. 9, the output of the front and rear G sensor 38 representing the braking deceleration has its high-frequency fluctuation component removed by the low-pass filter unit 81, and then the DC drift component is compensated by the drift correction unit 82. The drift-compensated front and rear G sensor outputs are supplied to the rough road index calculation unit 83, the gradient calculation unit 84, and the bypass valve drive determination unit 88.
The rough road index calculation unit 83 calculates a rough road index indicating the degree of rough road based on the frequency and level of the front and rear G sensor outputs. The gradient calculator 84 corresponds to steps S3 and S4 in FIG. 2, and based on the output of the front and rear G sensor indicating the braking deceleration, the rising gradient (rate of change) of the braking deceleration.
Is calculated.

Referring to FIG. 7, the initial value GO of the target deceleration set by the initial value setting section 61 (corresponding to step S2 in FIG. 2) is used as a pressure controllability correcting section 62 which is a main part of the present embodiment. Supplied to The correction unit 62 includes the controller 37
The pressure controllability correction coefficient KO is calculated in accordance with the map shown in the block 62 stored in the memory of FIG. Correction coefficient KO
Is for correcting the advance of the switching operation timing of the bypass valves 26 and 27 with respect to the intended rear wheel pressure generation timing (rear wheel pressure rise characteristic). For example, the deceleration gradient is 0 G / sec to 4 G / sec. The value gradually increases from the value “1” as it increases to 2 seconds, and 4G
It is set to take a constant value in the deceleration gradient region exceeding / sec. The correction unit 62 includes a gradient calculation unit 84 (FIG. 9).
A correction coefficient KO is calculated in accordance with the braking deceleration gradient data supplied from the vehicle, and the correction coefficient KO is added to the initial value GO of the target deceleration.
An output (GO * KO) is generated by multiplying by O.

The output of the pressure controllability correcting section 62 is supplied to an air temperature correcting section 63. The temperature correction unit 63 includes a block 63
The temperature correction coefficient KT is calculated in accordance with the map shown in FIG.
The correction coefficient KT is for correcting the target deceleration to decrease when there is a possibility of road surface freezing or snow accumulation. The correction coefficient KT takes a value “1” in a region where the outside air temperature is high and a value “1” in a region where the outside air temperature is low. Is set to a value smaller than ". This is because the lower the outside air temperature, the easier the road surface is to slip and the rear wheels are more likely to lock. The temperature correction unit 63 calculates a correction coefficient KT according to the outside air temperature detected by the outside air temperature sensor 41, and outputs an output (G0 * KO * KT) equal to the product of the output of the pressure controllability correction unit 62 and the correction coefficient KT. ).

The sky candidate positive part 64 calculates the sky candidate positive coefficient KW according to the map shown in the block 64. This correction coefficient KW is used to correct the target deceleration in accordance with rainfall or snowfall conditions, and takes a value "1" in a region where the wiper interval is small, and takes a value "1" in a region where the wiper interval is large. Is also set to a small value. The top candidate corrector 64 calculates a correction coefficient KW according to the wiper interval obtained by the interval calculator 66 that inputs the on / off output of the wiper switch 64,
The output (GO * KO * KT * KW) obtained by multiplying the output of the temperature correction unit 63 by the correction coefficient KW is sent to the road surface correction unit 65.

The road surface correction section 65 calculates a road surface correction coefficient KR according to the map shown in the block 65. The correction coefficient KR is for correcting the target deceleration to decrease in accordance with the rough road condition, and is set to take a smaller value as the rough road index increases. This is because the tire contact load fluctuates when traveling on a rough road, and therefore, instantaneous locking is likely to occur with the braking operation. The road surface correction unit 65 calculates a correction coefficient KR according to the rough road index data from the rough road index calculation unit 83 (FIG. 9), and multiplies the output of the sky candidate positive unit 64 by the correction coefficient KR. The braking speed correction unit 7 shown in FIG.
Send to 1.

The braking speed correction unit 71 forms a main part of the present invention, and calculates a braking speed correction coefficient KS according to a map shown in the block 71. The correction coefficient KS is used to set the braking force control characteristic in the panic brake region. In the region where the deceleration gradient is smaller than, for example, 4 (G / sec), the correction coefficient KS takes the value “1”, while 4 (G / It is set to take a value smaller than the value “1” in a region larger than (sec). This is because in the panic brake region, it is necessary to prevent the rear wheel front lock from the viewpoint of emphasizing braking stability. The braking speed correction unit 71 calculates a correction coefficient KS according to the deceleration gradient from the gradient calculation unit 84 (FIG. 9), and is equal to the product of the output of the road surface correction unit 65 (FIG. 7) and the correction coefficient KS. The output (GO * KO * KT * KW * KR * KS) is converted to the vehicle speed correction unit 7.
Send to 2.

The vehicle speed correction unit 72 calculates a vehicle speed correction coefficient KV according to the map shown in the block 72. The correction coefficient KV is used to prevent the stability factor from decreasing due to high-speed running, and is set to take a value "1" until the vehicle speed reaches a predetermined vehicle speed, and to take a value which decreases as the vehicle speed increases in a region exceeding the predetermined vehicle speed. Have been. The correction coefficient KV is determined when the brake switch 30 is turned on, and is maintained during one subsequent braking operation. Vehicle speed correction unit 72
Calculates the vehicle speed correction coefficient KV according to the vehicle speed V from the vehicle speed sensor 35, and outputs an output (GO * KO * KT * KW * KR *) equal to the product of the correction coefficient KV and the output of the braking speed correction unit 71.
KS * KV) is sent to the turning correction unit 75.

The high-frequency fluctuation component of the output of the steering angle sensor 39 is removed by the low-pass filter 73. The low-pass filtered steering angle sensor output δH is calculated by the lateral G calculation unit 7.
4 is supplied. The lateral G calculation unit 74 calculates a calculation formula GYB = GYB = V based on the steering angle sensor output δH and the vehicle speed sensor output V.
The horizontal G is calculated according to (V ² * δH) / {(1 + KV ² ) * L * ρ * 9,8}. Here, the symbol GYB indicates the lateral G, and K, L and ρ indicate the stability factor, the wheel base and the steering gear ratio, respectively.

The turning correction unit 75 calculates a turning correction coefficient KC according to the map shown in the block 75. The correction coefficient KC is “1” on the outer wheel side regardless of the value GYB of the lateral G.
On the other hand, on the inner wheel side, a value that decreases as the lateral G increases in a region exceeding a predetermined lateral G is set. As a result, the target deceleration on the inner wheel side is corrected to decrease,
It is possible to prevent the braking force from being distributed such that the inner wheel is locked first after turning due to the load movement caused by the turning lateral G, thereby improving braking stability.
The turning correction unit 75 calculates a turning correction coefficient KC according to the value GYB of the lateral G input from the lateral G calculating unit 74, and then multiplies the output of the vehicle speed correcting unit 72 by the correction coefficient KC to obtain an output ( GO
* KO * KT * KW * KR * KS * KV * KC) is sent to the ABS operation correcting section 87 shown in FIG. The correction coefficient KC
Is calculated based on the lateral G when the brake switch 30 is turned on, and is maintained during one braking operation.

The ON determining section 85 shown in FIG. 9 determines the ON operation of the brake switch 30 based on the output of the brake switch 30. The bypass circuit opening drive unit 86 opens the bypass circuits 24 and 25 by driving the bypass valves 26 and 27 to open according to the ON operation determination signal from the ON determination unit 85. Preferably, in order to reduce the frequency of opening and closing operation of the bypass valve, the bypass valve is not opened and closed at a predetermined vehicle speed, for example, 6 km / h or less.

The ABS operation correcting section 87 includes an on-discriminating section 85
Output and ABS signal a1 from ABS controller 36
The ABS operation correction coefficient KA is determined based on .about.a4. The correction coefficient KA takes a value "0.1" when the rear wheel ABS operates before the front wheel ABS, and takes a value "1" otherwise. In the present embodiment, the above-described various correction units 62 to
The target deceleration is corrected in 65, 71, 72, and 75 to prevent rear wheel front lock distribution even when braking is performed under various conditions. May be excessive. Therefore, when the rear wheel ABS operates earlier than the front wheel ABS, for example, when traveling on a low μ road, it is determined that the braking force distribution to the rear wheel side is excessive, and
Correct the decrease of the target deceleration. It should be noted that once the ABS operation correction coefficient KA is once set to a small value in order to reduce and correct the target deceleration, it is maintained during one braking. The ABS operation correction unit 87 adds an ABS operation correction coefficient K to the output of the turning correction unit 75.
The output obtained by multiplying A is sent to the bypass valve drive determining unit 88.

The bypass valve drive discriminating unit 88 outputs the drift corrected front and rear G sensor output G to the ABS operation correcting unit 87.
Output (GO * KO * KT * KW * KR * KS * KV * KC * K
A) It is determined whether or not it is the above. The bypass circuit closing drive unit 89 closes the bypass valves 26 and 27 in response to the determination signal sent from the determination unit 88 when the sensor output G is equal to or greater than the output of the correction unit 87, and causes the bypass circuits 24 and 27 to close.
Close 25.

The essential point of the operation of the controller 37 shown in the form of a functional block in FIGS.
4 to 4 (G / sec), the target deceleration is increased and corrected by using the pressure controllability correction coefficient KO that increases as the deceleration gradient increases, and the deceleration exceeding the upper limit 4 (G / sec) of the normal braking range. In the case of a speed gradient, the target deceleration is corrected to be reduced using the braking speed correction coefficient KS that decreases as the deceleration gradient increases.

By increasing and correcting the target deceleration by the correction coefficient KO, an effect similar to the effect of the low-pass filter processing of the front and rear G sensor outputs in the first embodiment can be obtained. That is, the timing of the switching operation of the bypass valves 26 and 27 from the open state to the closed state is determined according to the comparison result between the actual deceleration represented by the front and rear G sensor outputs and the target deceleration. This is because the increase of the value acts on the timing of the bypass valve switching operation in a manner equivalent to delaying the phase of the front and rear G sensor output.

For the same reason, the reduction correction of the target deceleration by the correction coefficient KS has the same effect as the prohibition of the low-pass filter processing in the panic brake region in the first embodiment. Then, by increasing and correcting the target deceleration within the normal braking range, the intended rear wheel braking force can be generated regardless of the brake pedal depressing operation speed,
The braking force distribution between the front wheel side and the rear wheel side becomes appropriate.
Further, by correcting the target deceleration to decrease in the panic brake region, the rear wheel tip lock can be prevented, and the braking stability is improved.

According to the braking force distribution control method of the present invention, the first
The present invention is not limited to the second embodiment, and various modifications are possible. For example, in order to correct the timing of switching the bypass valve, the output of the front and rear G sensor is subjected to a low-pass filter process in the first embodiment, and the target deceleration is corrected to be increased in the second embodiment. At the same time, the target deceleration may be increased and corrected. In general, it may be difficult to arbitrarily set the filter characteristics. On the other hand, it is relatively easy to arbitrarily set the deceleration gradient-target deceleration increase correction amount characteristic, and to combine both. There are benefits.

In order to properly distribute the braking force under various braking conditions, the first embodiment corrects the target deceleration in the lateral G direction,
In the embodiment, the temperature correction or the ABS operation correction is performed on the target deceleration. However, the correction for optimizing the braking force distribution is not limited to this, and various modifications can be made.

[0054]

[0055]

[Effect of the Invention] As described above, according to the brake force distribution control method according to one aspect of the present invention, the braking deceleration of the rate of change is
Since the target deceleration is variably set in accordance with the rate of change of the braking deceleration so that the target deceleration increases as it increases ,
In accordance with the degree of depression of the brake pedal, the timing of the switching operation from the open state to the closed state of the bypass valve for enabling the rear wheel braking force suppression effect by the proportioning valve can be delayed as much as necessary. Therefore,
As long as the contribution of the front wheel side brake is large and the intended rear wheel braking force has not yet been generated, the rear wheel braking force is not suppressed, and therefore, the appropriate distribution of the braking force may be hindered. Absent. Therefore, an appropriate distribution of the braking force can be ensured regardless of the speed at which the driver steps on the brake pedal.

According to a particular aspect of the present invention, wherein the target deceleration is reduced when the deceleration gradient is equal to or greater than a predetermined value, the brake operation is performed at such a large speed that provides a braking speed exceeding a practical braking speed. Is performed, the switching operation of the bypass valve is not delayed, and therefore,
The distribution of the braking force to the rear wheels is not excessively increased, and the rear wheels are prevented from being locked, so that the braking stability is improved.

According to another aspect of the present invention, the output of the acceleration sensor is compensated for the phase delay so that the phase of the output of the acceleration sensor is delayed as the rate of change of the braking deceleration increases. Sometimes the switching operation timing of the bypass valve can be delayed,
Appropriate braking force distribution can be ensured irrespective of the speed at which the driver steps on the brake pedal.

According to a specific embodiment of the present invention in which the phase lag compensation of the output of the acceleration sensor is inhibited when the deceleration gradient is equal to or greater than the predetermined value, in the panic brake region, the switching operation of the bypass valve is not delayed, and accordingly, The braking stability is improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a main part of a brake system equipped with a device for implementing a braking force distribution control method according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing a part of a procedure of a bypass valve opening / closing control executed by a controller of the braking force distribution control device of FIG. 1;

3 is a flowchart showing the rest of the bypass valve opening / closing control procedure, a part of which is shown in FIG.

FIG. 4 is a graph showing frequency-phase characteristics of low-pass filtered and processed front and rear G sensor outputs obtained in step S6 of FIG. 3;

FIG. 5 is a graph showing the relationship between the braking deceleration gradient and the rear wheel pressure at the time of a bypass valve switching operation when the output of the front and rear G sensors is not low-pass filtered.

FIG. 6 is a graph showing the relationship between the braking speed and the rear wheel pressure at the time of the bypass valve switching operation when the output of the front and rear G sensors is low-pass filtered in the normal braking range, while the low-pass filtering is prohibited in the panic braking range. It is a graph shown.

FIG. 7 is a functional block diagram showing a part of a function of a controller provided in an apparatus for implementing a braking force distribution control method according to a second embodiment of the present invention.

FIG. 8 is a functional block diagram showing another function of the controller shown in FIG. 7;

FIG. 9 is a functional block diagram showing functions of the controller different from those shown in FIGS. 7 and 8;

[Explanation of symbols]

 Reference Signs List 11 brake pedal 13 master cylinder 14, 17, 20, 22 ABS valve 161, 162, 163, 164 wheel cylinder 24, 25 bypass pipe 26, 27 bypass valve 30 brake switch 35 vehicle speed sensor 36 ABS controller 37 controller 38 longitudinal acceleration sensor 39 Steering angle sensor 41 Outside temperature sensor 42 Wiper switch 62 Pressure controllability correction unit 71 Braking speed correction unit

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tadao Tanaka 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (56) References JP-A-5-147519 (JP, A) JP 58-1085862 (JP, A) Full-scale 1988-42463 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60T 8/26

Claims (4)

(57) [Claims] 1. By controlling the opening and closing of a bypass valve provided in a pipe that bypasses a proportioning valve,
A braking force distribution control method for selectively enabling a function of the proportioning valve for suppressing a rise in the rear wheel wheel cylinder pressure with respect to a rise in the master cylinder pressure and adjusting a rear wheel braking force. Calculating the rate of change of the detected braking deceleration, and calculating the target deceleration as the rate of change of the braking deceleration increases.
As but increase, before according to the brake deceleration of the rate of change
The serial target deceleration is variably set, the detected braking deceleration is to switch to a closed state from the open state before <br/> Symbol bypass valve reaches the target deceleration
Braking force distribution control method, characterized by switching control to. 2. The braking force distribution control method according to claim 1, wherein the target deceleration is reduced when the rate of change of the braking deceleration is equal to or greater than a predetermined value. 3. By controlling the opening and closing of a bypass valve provided in a pipe bypassing the proportioning valve,
A braking force distribution control method for selectively enabling a function of the proportioning valve for suppressing a rise in the rear wheel wheel cylinder pressure with respect to a rise in the master cylinder pressure and adjusting a rear wheel braking force, comprising the steps of: The speed is detected, and the output of the acceleration sensor is delayed in phase so that the phase of the output of the acceleration sensor is delayed as the rate of change of the braking deceleration increases. The output of the acceleration sensor is represented by the compensated acceleration sensor output. and the braking deceleration reaches the target deceleration of the bypass valve
A braking force distribution control method, wherein opening / closing control is performed so as to switch from an open state to a closed state . 4. The braking force distribution control method according to claim 3, wherein when the rate of change of the braking deceleration is equal to or greater than a predetermined value, the output of the acceleration sensor is not compensated for a phase delay.