JPH0891199A - Wheel brake pressure controller - Google Patents

Abstract

PURPOSE: To improve braking performance, directional stability, and steering performance of a vehicle by providing a conversion mode selecting means, which automatically switches the choice of a conversion mode which gives a pressure adjusting means the instruction with regard to the generation of a first pressure adjusting command and a second pressure adjusting command, corresponding to the condition of the vehicle. CONSTITUTION: When an independent pressure adjusting command to a left, front wheel is 'Increase the pressure', while an independent pressure adjusting command to a right, front wheel is 'Hold', if a first conversion mode (H) is designated against the first independent pressure adjusting command, 'Increase the pressure' is outputted as the first pressure adjusting command CPFO. When an independent pressure adjusting command to a left rear wheel is 'Reduce the pressure', while an independent pressure adjusting command to the right, rear wheel is 'Hold', if the second conversion mode (L) is designated against the second independent pressure adjusting command, 'Reduce the pressure' is outputted as a pressure adjusting command CPRO. Conversion mode selecting means 311, 312, 313 automatically switch the choice between the first conversion mode (H) and the second conversion mode (L) in the pressure adjusting command conversion means, correspond ing to the condition of the vehicle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for controlling a brake hydraulic pressure applied to a wheel brake, and more particularly to a wheel slip rate or a road surface friction coefficient μ during braking by a driver.
The wheel brake pressure is reduced so as to prevent the wheel rotation from completely stopping (wheel lock) even if the vehicle body is moving, and then the braking distance becomes as short as possible. The present invention relates to a wheel brake pressure control device suitable for anti-skid control in which the pressure is increased as described above, and the pressure reduction and increase are repeated as necessary.

[0002]

2. Description of the Related Art In general, a brake master cylinder applies a brake pressure (first pressure) corresponding to the pushing pressure of a brake pedal operated by a driver. However, if the brake pressure is excessively large, the wheels may be locked, and skid may occur, which may deteriorate the running stability of the vehicle and may increase the braking distance. The so-called ABS device (anti-skid brake system) automatically prevents such a problem.

Generally, in an ABS device, the moving speed (reference speed) of the vehicle body is estimated and calculated from the rotation speeds of a plurality of wheels, and the slip ratio of the wheel or the friction coefficient μ of the road surface is calculated from the reference speed and the rotation speed of the wheels. Alternatively, it is estimated that the wheel brake pressure (wheel braking force) is reduced (decreased) so that the wheel rotation is prevented from completely stopping (wheel locking) even if the vehicle body is moving, and then the braking distance is reduced. The pressure is increased (increased) so that is as short as possible.

In the wheel braking force control as described above, it is most desirable to control each of the four wheels independently. However, if the braking force of the four wheels can be controlled independently, the structure of the piping of the braking system must be complicated, and the number of components such as solenoid valves used for pressure adjustment also increases. The cost of the braking system is inevitably high.

Generally, in order to ensure safety against failure, the brake system piping of an automobile is separated into at least two systems. For example, in a system called X pipe, a brake cylinder for the right front wheel and a brake cylinder for the left rear wheel are commonly connected to the first pipe, and a brake cylinder for the left front wheel and a brake cylinder for the right rear wheel are connected. Are commonly connected to the second pipe, and braking pressures are applied to the first pipe and the second pipe from independent pressure sources (usually master cylinders). Also, in the system called front and rear piping,
The brake cylinder for the right front wheel and the brake cylinder for the left front wheel are commonly connected to the first pipe, and the brake cylinder for the right rear wheel is also connected.
The brake cylinder and the brake cylinder of the left rear wheel are commonly connected to the second pipe, and braking pressure is applied to the first pipe and the second pipe from independent pressure sources.

Conventionally, therefore, most of the control for determining the braking force is carried out by the four wheels independently, but since the two systems of piping are used as they are, the actual braking force control of the actuator is independent of only the two systems. May be carried out in. That is, the braking force control of the four wheels is converted into the braking force control of two systems for control. In this conversion, if there is a difference in the braking force of the two wheels connected to the common pipe, the braking force of the higher priority is determined as the braking force of the pipe.

An X piping system is disclosed in, for example, Japanese Patent Laid-Open No. 63-
It is disclosed in Japanese Patent No. 291756. In this case, when converting the braking force of the four wheels independently into two systems, the control that prioritizes the left front wheel and the right rear wheel, or the right front wheel and the left rear wheel, whichever has the smaller braking force, and the front wheel side. Prioritized control includes braking force distribution at that time, presence / absence of lock tendency of rear wheels, front wheel speed,
It is switched according to the size of the rear wheel speed.

[0008]

Regarding the X piping system, it has been considered to convert the braking force control of the four wheels into the braking force control of two systems as described above. Adjusts the braking forces of the four-wheel actuators independently, and does not convert the four-wheel independent braking force control into two-system braking force control in order to reduce the device cost. Further, in the case of the front and rear piping system, there is no technique for ensuring the directional stability and the steerability of the vehicle by only controlling the braking force of two systems. Note that the X piping system and the front and rear piping systems have different combinations of wheels that can independently control the braking force, so the control of the X piping system cannot be adopted in the front and rear piping systems. However, for the front and rear piping system, there is a demand for a device that can suppress the cost increase of the device and can maintain the braking performance, directional stability, and steering performance of the vehicle.

Therefore, according to the present invention, a wheel brake having two independent pipe systems in which the pipes leading to the left and right front wheel brake cylinders are commonly connected and the pipes leading to the left and right rear wheel brake cylinders are commonly connected. An object of the present invention is to improve braking performance, directional stability and steering performance of a vehicle in a pressure control device.

[0010]

In order to solve the above problems, in the present invention, a means (52) for braking the rotation of the left front wheel of the vehicle and a means (51) for braking the rotation of the right front wheel of the vehicle.
A front pipe (31) for commonly connecting and, a rear side for commonly connecting a means (54) for braking rotation of the left rear wheel and a means (53) for braking rotation of the right rear wheel of the vehicle. Pipe (32), first pressure adjusting means (33, 34) for adjusting the first pressure applied to the front pipe, and second pressure adjusting for adjusting the second pressure applied to the rear pipe. Means (37,
38), a wheel brake pressure control device having: a state detecting means including means for detecting a rotational speed of at least each of four wheels of the left front wheel, right front wheel, left rear wheel and right rear wheel of the vehicle. (41-44): Independent pressure control commands (CPFL, CP) for each of the four wheels, the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel, based on the information detected by the state detection means.
Pressure regulation command generating means (7) for generating FR, CPRL, CPRR)
4FL, 74FR, 74RL, 74RR); of the four independent pressure regulation commands generated by the pressure regulation command generation means, based on the first set of independent pressure regulation commands (CPFL, CPFR) for the left front wheel and the right front wheel, The first pressure adjustment command (CP
F0) and a second pressure regulation command (CPR0) for the second pressure based on a second set of independent pressure regulation commands (CPRL, CPRR) for the left rear wheel and the right rear wheel. Pressure command converting means (63, 76, 84); and a first conversion mode for giving priority to a command on the pressure increasing side in each set, with respect to the independent pressure adjusting commands of the first and second sets. (H) or the second conversion mode (L) which gives priority to the command on the pressure reduction side is instructed to the pressure control command conversion means, and
Depending on the state of the vehicle at that time, the selection of the conversion mode instructing the pressure adjustment command converting means for each of the generation of the first pressure adjustment command and the generation of the second pressure adjustment command is automatically switched. , Conversion mode selection means (311, 312, 31
3); is provided.

According to a second aspect of the present invention, the conversion mode selection means is used when the absolute value of the acceleration (Gy) in the left-right direction of the vehicle body is equal to or greater than a first threshold value (k4), or when the left front wheel is used. When the absolute value of the rotation speed difference (ΔVF) of the right front wheel is equal to or greater than the second threshold value (k6), both the generation of the first pressure regulation command and the generation of the second pressure regulation command are performed. The first
Select the conversion mode of.

According to the third aspect of the present invention, the conversion mode selection means detects the steering angle (θf), further obtains a differential value (dθf) of the steering angle, and the absolute value of the steering angle is the third value. Is equal to or greater than the threshold value (k2) of the steering angle and the absolute value of the differential value of the steering angle is equal to or greater than the fourth threshold value (k3), the first pressure adjustment command is generated and the second pressure adjustment command is generated. Control is performed so that the second conversion mode is selected for both generation of the command.

According to a fourth aspect of the present invention, the conversion mode selecting means detects the vehicle body speed (VS0), obtains a differential value (dVS0) of the vehicle body speed, and obtains an absolute value of the differential value of the vehicle body speed. Is greater than or equal to a fifth threshold value (k1), the first conversion mode is used for the generation of the first pressure adjustment command.
Mode and the second conversion mode are alternately and repeatedly selected, and the second conversion mode is selected for the generation of the second pressure adjusting command.

Further, in the invention of claim 5, the conversion mode selecting means generates the first pressure adjusting command when the absolute value of the differential value of the vehicle body speed is equal to or more than a fifth threshold value. On the other hand, the first conversion mode and the second conversion mode are alternately and repeatedly selected, and the time for selecting the first conversion mode and the second conversion mode are selected. The ratio (Rh) with respect to the time to be set is determined according to the detected vehicle body speed (VS0).

In the sixth aspect of the present invention, the conversion mode selecting means continues the first conversion mode for a predetermined time (k5) or more with respect to the generation of the first pressure adjusting command. When selected, the second conversion mode is temporarily forcibly selected (318, 319, 320, 321, 322).

The symbols shown in parentheses above are reference numerals of corresponding elements in the embodiments to be described later, but each component of the present invention is a specific element in the embodiments. It is not limited to only.

[0017]

In the present invention, since the piping for supplying the pressure for braking each wheel is a so-called front-rear piping system, the braking means (52) for the left front wheel and the braking means (51) for the right front wheel are connected to the front piping ( 31) commonly connected to the rear left wheel braking means (5).
4) and the braking means (53) for the right rear wheel are the rear pipe (32).
Since it is commonly connected to the
Only the two systems of the pressure of 1 and the second pressure applied to the rear pipe can be independently adjusted. Then, the brake pressure control such as the anti-skid control is realized by controlling the pressure increase, the pressure decrease, and the hold for the first pressure and the second pressure.

The actual braking pressure can be independently adjusted only in the two systems of the front side pipe and the rear side pipe, but in this embodiment, in order to improve the directional stability and steerability of the vehicle, a pressure adjustment command is given. The generation means (74FL, 74FR, 74RL, 74RR)
Independent pressure regulation commands (CPFL, CPFR, CPRL, CPR) for each of the left front wheel, right front wheel, left rear wheel, and right rear wheel
R) is generated. Then, the pressure adjustment command conversion means (63, 7)
6, 84) of the four independent pressure regulation commands generated by the pressure regulation command generation means, based on the first set of independent pressure regulation commands (CPFL, CPFR) for the left front wheel and the right front wheel. A first pressure regulation command (CPF0) for pressure is generated, and a second set of independent pressure regulation commands (CPRL, C) for the left rear wheel and the right rear wheel is generated.
A second pressure regulation command (CPR0) for the second pressure is generated based on PRR). The first pressure adjustment command adjusts the pressure of the front pipe (first pressure), and the second pressure adjustment command adjusts the pressure of the rear pipe (second pressure).

In the present invention, the pressure adjustment command converting means (63,
76, 84) as a conversion mode when the first pressure regulation command and the second pressure regulation command are generated, a first conversion mode (H) and a second conversion mode (L). ) And are provided. In the first conversion mode (H), the command on the pressure-increasing side in each group is given priority over the independent pressure regulation commands of the first and second groups, and the second conversion mode (H) is given priority. In (L), the command on the pressure reducing side is prioritized.

For example, when the independent pressure regulation command for the left front wheel is "increase" and the independent pressure regulation command for the right front wheel is "hold", the "first pressure regulation command" is set for the first group of independent pressure regulation commands. If "Conversion mode (H)" is specified, "Increase pressure" is set as the first
Output as a pressure control command (CPF0). Further, for example, when the independent pressure regulation command for the left rear wheel is “decompression” and the independent pressure regulation command for the right rear wheel is “hold”, the “second conversion” is performed for the second group of independent pressure regulation commands. If "mode (L)" is designated, "decompression" is output as the second pressure adjustment command (CPR0).

Then, conversion mode selection means (311, 3
12, 313) selects the first conversion mode (H) and the second conversion mode (L) in the pressure adjustment command conversion means.
Automatically switch according to the state of the vehicle at that time.

Each of the four independent pressure regulating commands is set so as to be in an optimum state. However, for example, even if the independent pressure regulation command (CPFL) for the left front wheel and the independent pressure regulation command (CPFR) for the right front wheel are different, the braking means (break cylinder) for the left front wheel and the right front wheel is connected to a common pipe. Therefore, the braking pressures of the left front wheel and the right front wheel cannot be adjusted independently. When the first pressure regulation command (CPF0) is generated in the first conversion mode (H), the optimum pressure regulation is applied to the wheel corresponding to the preferentially selected independent pressure regulation command. However, for a wheel corresponding to an independent pressure regulation command that is not selected, the pressure becomes larger than the optimum state. When the first pressure regulation command (CPF0) is generated in the second conversion mode (L), it is optimal for the wheel corresponding to the preferentially selected independent pressure regulation command. Although the pressure adjustment is performed, the pressure becomes smaller than the optimum state for the wheel corresponding to the independent pressure adjustment command that is not selected.

Therefore, if the first conversion mode (H) is applied to both the generation of the first pressure regulation command (CPF0) and the generation of the second pressure regulation command (CPR0), The wheel braking force of the four wheels as a whole becomes larger than that in the optimum state. If the second conversion mode (L) is applied to both the generation of the first pressure regulation command (CPF0) and the generation of the second pressure regulation command (CPR0), four wheels will be generated. As a whole, the wheel braking force becomes smaller than that in the optimum state, and a problem such as a longer braking distance is likely to occur.

Generation of the first pressure regulation command (CPF0) and second generation
The first conversion mode (H) is applied to one of the generation of the pressure regulation command (CPR0) and the second conversion mode is applied to the other.
Applying mode (L), the braking force across the four wheels approaches the optimum condition, and the desired result is obtained. Also,
In a general automobile, since the engine is installed on the front side of the vehicle body, the weight applied to the front wheels is larger than the weight applied to the rear wheels. In such a weight distribution situation, the first conversion mode (H) is applied to the generation of the first pressure regulation command (CPF0),
It is desirable to apply the second conversion mode (L) to the generation of the second pressure regulation command (CPR0).

However, the first pressure regulation command (CPF0)
Even if the first conversion mode (H) is applied to the generation of the second pressure control command and the second conversion mode (L) is applied to the generation of the second pressure regulation command (CPR0), a problem may occur. There is. For example,
When the first conversion mode (H) is applied to the generation of the first pressure regulation command (CPF0), it is avoided that the wheel corresponding to the unselected independent pressure regulation command is likely to be locked. I can't. If the wheels are locked, the sideslip of the wheels deteriorates the steerability. Therefore, it is necessary to avoid locking the wheels when reliable steering is required. Further, if the wheels are locked for a long time, the locked tires are unevenly worn, which causes a problem in running stability thereafter. Therefore, it is necessary to avoid locking the wheels for a long time.
Further, when the second conversion mode (L) is applied to the generation of the second pressure regulation command (CPR0), when braking is applied in the limit turning state, the independent pressure regulation inside the turning where the load is released Since the command is selected, the braking force on the rear wheels drops extremely.

According to the present invention, the conversion mode selecting means (3
11, 312, 313) are conversion modes for instructing the pressure adjustment command conversion means with respect to each of the generation of the first pressure adjustment command and the generation of the second pressure adjustment command in accordance with the state of the vehicle at that time. Since the selection of the mode is automatically switched, it is possible to control the braking pressure so as to obtain the most preferable result at that time.

According to the second aspect of the present invention, when the absolute value of the acceleration (Gy) in the left-right direction of the vehicle body is equal to or greater than the first threshold value (k4), or the rotational speed difference (ΔVF) between the left front wheel and the right front wheel.
When the absolute value of is greater than or equal to the second threshold value (k6), it is considered that the vehicle is in the critical turning state. In this case, for both the generation of the first pressure regulation command and the generation of the second pressure regulation command,
Since the first conversion mode is selected, the required braking force can be reliably obtained and the braking distance can be prevented from being extended more than necessary.

According to the third aspect of the present invention, the steering angle (θf) and the differential value (dθf) of the steering angle are detected, and the absolute value of the steering angle is not less than the third threshold value (k2), and the steering angle is When the absolute value of the differential value of is greater than or equal to the fourth threshold value (k3), the second pressure control command is generated for both the first pressure control command generation and the second pressure control command generation. Control to select the conversion mode. That is, in this case, since the driver makes a fast steering input, the control is performed with more emphasis on the steerability so as to follow the steering input.

According to the invention of claim 4, the vehicle body speed (VS0)
Is detected, the differential value (dVS0) of the vehicle body speed is obtained, and when the absolute value of the differential value of the vehicle body speed is equal to or greater than the fifth threshold value (k1), the first pressure adjustment command is generated. On the other hand, the first conversion mode and the second conversion mode are alternately and repeatedly selected, and the second conversion mode is selected for the generation of the second pressure adjusting command. select. Since the vehicle body speed is obtained based on the wheel speed, the absolute value of the differential value of the vehicle body speed, that is, when the acceleration in the traveling direction of the vehicle body is very large, especially when the first conversion mode is selected, There is a high possibility that lock will occur in the. However, when the second conversion mode is selected, the wheels are less likely to lock. By alternately selecting the first conversion mode and the second conversion mode, even if the wheel locks, it occurs intermittently, preventing the wheel lock from continuing for a long time. As a result, uneven wear of the tire is prevented.

According to the fifth aspect of the present invention, when the absolute value of the differential value of the vehicle body speed is equal to or greater than the fifth threshold value, the first conversion mode is generated with respect to the generation of the first pressure adjustment command. -And the second conversion mode are alternately and repeatedly selected, and the first
Of the detected vehicle speed (VS) is determined by the ratio (Rh) between the time for selecting the second conversion mode and the time for selecting the second conversion mode.
0). That is, the uneven wear of the tire due to the locking of the wheels becomes more remarkable as the vehicle speed increases, but when the vehicle speed is high, the second conversion mode is used.
By increasing the time for selecting the tire, uneven wear of the tire is effectively prevented. When the vehicle speed is low, even if the tire locks for a long time, uneven wear of the tire is unlikely to occur. Therefore, the time for selecting the first conversion mode may be increased.

In the sixth aspect of the present invention, the first conversion mode has a predetermined time (k) for the generation of the first pressure adjusting command.
5) When the above selections are continued, the second conversion mode is forcibly selected temporarily (318, 319, 32).
0, 321, 322). That is, when the first conversion mode is selected, there is a high possibility that the wheels will be locked. Therefore, if the first conversion mode is continuously selected for a long time, the wheels will be in a locked state. May continue for a long time, causing uneven wear on the locked tire. When the second conversion mode is temporarily selected, the wheel is temporarily unlocked and the wheel rotates to move the surface of the tire in contact with the ground. Since it is dispersed, uneven wear is unlikely to occur.

[0032]

1 shows a wheel brake pressure system according to an embodiment of the present invention, and FIG. 2 shows a wheel brake pressure system to which various solenoid valves and sensors of the wheel brake pressure system are connected. An outline of an electric system for controlling each pressure of the wheel cylinders 51 to 54 will be shown.

Referring first to FIG. 1, the brake pedal 3
When the driver (driver) depresses, the tandem type master cylinder 2 generates front wheel brake fluid pressure 2a and rear wheel brake fluid pressure 2b corresponding to the stepping pressure. In the state shown in FIG. 1, the front wheel brake fluid pressure 2a is supplied to the front wheel side pipe 31 via the electromagnetic switching valve 62, and is connected to the front wheel side pipe 31 in common to the front right wheel (driven wheel) FR. Is applied to the wheel brake 51 of the vehicle and the wheel brake 52 of the front left wheel (driven wheel) FL. The rear brake fluid pressure 2b is regulated by the proportional control valve 6, and further the electromagnetic switching valve 63 is used.
Is supplied to the rear wheel side pipe 32 via the wheel brake and is commonly connected to the rear wheel side pipe 32. The wheel brake 53 of the rear right wheel (driving wheel) RR and the wheel brake of the rear left wheel (driving wheel) RL are connected.
It is applied to the key 54. These brake fluid pressures are hereinafter referred to as the first pressure.

The pump 21 is driven by an electric motor 24, sucks the brake liquid of the reservoir 4 and supplies it to the accumulator 22 through a check valve 25. The high pressure of the accumulator 22 is supplied to the hydro booster 5 and the electromagnetic switching valves 64 and 65. Accumulator 2
The pressure of the break liquid 2 is detected by the pressure sensor 46.
When the pressure of the accumulator 22 falls below the lower limit value, the low pressure switch 47 is closed. Reservoir 4 and Accumulator 2
A relief valve 23 is interposed between the two, and when the pressure of the accumulator 22 reaches the upper limit value, the relief valve 23 causes the brake liquid of the accumulator 22 to fall below the upper limit value. It discharges to the reservoir 4 until it becomes. The electronic control unit 10 shown in FIG.
7 open (pressure exceeds lower limit) / closed (pressure is lower than lower limit) and read pressure detected by pressure sensor 46, and when low pressure switch 47 is closed (pressure is lower than lower limit), electric When the motor 24 is driven and the detected pressure of the pressure sensor 46 reaches a set value lower than the upper limit value, the electric motor 24 is stopped,
The pressure of the accumulator 22 is maintained at a substantially constant pressure (range between the lower limit value and the set value). This accumulator 2
The brake fluid pressure of 2 is hereinafter referred to as the third pressure.

The pressure (third pressure) of the accumulator 22 is applied to the hydro booster 5, and the hydro booster 5
Adjusts the pressure to a pressure proportional to the pushing force of the brake pedal 3 and applies the pressure to the electromagnetic switching valves 64 and 65. This is the booster pressure, which is about 120% of the pressure output from the brake master cylinder 2. This booster pressure is hereinafter referred to as the second pressure.

Accumulator pressure (third pressure) and booster pressure (second pressure) are applied to the electromagnetic switching valves 64 and 65. The electromagnetic switching valve 64 has a booster pressure (second pressure) as shown in FIG. 1 when the electric coil is not energized.
Is applied to the input port of the pressure increasing / decreasing valve unit 334 on the front wheel side, but when the electric coil is energized, the booster pressure (second
Instead of (pressure), accumulator pressure (third pressure) is applied to the input port of the solenoid valve 33 for increasing pressure. The electromagnetic switching valve 65 is
When the electric coil is not energized, the booster pressure (second pressure) is applied to the input port of the rear wheel side pressure increasing / decreasing valve unit 378 as shown in FIG. 1, but when the electric coil is energized. The accumulator pressure (third pressure) is applied to the electromagnetic switching valve 37 instead of the booster pressure (second pressure).

As shown in FIG. 1, the electromagnetic switching valve 62 outputs the output pressure (first pressure) of the brake master cylinder 2 to the front right wheel brake 51 and the front left wheel brake when the electric coil is not energized. When the electric coil is energized, the output port of the pressure increasing / decreasing valve unit 334 on the front wheel side (the output port of the pressure increasing electromagnetic valve 33) is supplied to the front right wheel brake 51 and the front wheel. The left wheel brake 52 is connected.

As shown in FIG. 1, the solenoid operated directional control valve 63 controls the output pressure of the brake master cylinder 2 adjusted by the proportional control valve 6 (first pressure) as shown in FIG. Although applied to the right wheel brake 53 and the rear left wheel brake 54, when the electric coil is energized, the output port of the pressure increasing / decreasing valve unit 378 on the rear wheel side (the output port of the pressure increasing electromagnetic valve 37). ) Is connected to the rear right wheel brake 53 and the rear left wheel brake 54.

The pressure increasing / decreasing valve unit 334 includes an electromagnetic switching valve 6
The pressure-regulated pressure is generated based on the second pressure or the third pressure output by 4 and the pressure is applied to the front right wheel brake 51 and the front left wheel brake 52 via the electromagnetic switching valve 62. Apply. That is, by energizing the electric coil of the pressure increasing solenoid valve 33, the pressure applied to the front right wheel brake 51 and the front left wheel brake 52 is increased, and the pressure reducing solenoid valve 34 is increased.
By energizing the electric coil of, the pressure applied to the front right wheel brake 51 and the front left wheel brake 52 can be reduced.

The pressure increasing / decreasing valve unit 378 includes an electromagnetic switching valve 6
5 produces a regulated pressure on the basis of the second pressure or the third pressure output to the rear right wheel brake 53 and the rear left wheel brake 54 via the electromagnetic switching valve 63. Apply. That is, by energizing the electric coil of the pressure increasing solenoid valve 37, the pressure applied to the rear right wheel brake 53 and the rear left wheel brake 54 is increased, and the pressure reducing solenoid valve 38 is increased.
By energizing the electric coil of, the pressure applied to the rear right wheel brake 53 and the rear left wheel brake 54 can be reduced.

In the brake pressure system shown in FIG. 1, a brake pressure transmission system that applies only the output pressure of the brake master cylinder 2 to the wheel brakes, a brake pressure transmission system during anti-skid control, and Table 1 shows the constituent elements of each of the brake pressure transmission systems during the braking force distribution control for each wheel brake. In Table 1, the elements that make up each transmission system are
The wheel brake is taken as the starting point and extracted in the direction toward the brake pressure source. Further, in Table 1 and the drawings, “anti-skid control” is described as “ABS control”. "ABS" means "anti-skid" in this document.

[0042]

[Table 1]

In each column of "Anti-skid control pressure system" and "Braking force distribution control pressure system" in Table 1, the pressure increase / decrease valve units 334 and 378 are increased / decreased by the electronic control unit 10 (FIG. 2). It That is, when decompression is required,
Intensity solenoid on-off valves 33 and 3 in those units
7 is closed by energizing those electric coils, and the pressure reducing electromagnetic on-off valves 34 and 38 are opened by energizing these electric coils. When pressure increase is required, the pressure increasing electromagnetic on-off valves 33 and 37 are opened. Is opened by de-energizing those electric coils, and the decompression electromagnetic on-off valves 34 and 38 are closed by de-energizing those electric coils. When a hold (maintaining the current pressure as it is) is required, the pressure-increasing electromagnetic on-off valves 33 and 37 are closed by energizing their electric coils, and the pressure-decreasing electromagnetic on-off valves 34 and 38 are electrically connected. The valve is closed by de-energizing the coil.

Referring to FIG. The main body of the electronic control unit 10 is a microcomputer 11, and the main elements of this microcomputer 11 are a CPU 14, a ROM 15, and an RA.
M16 and timer 17. The electronic control unit 10 further includes signal processing circuits 18a to 18m for energizing (energizing) the sensor to generate a detection signal, an electric circuit for supplying the detection signal to the microcomputer 11, that is, an input interface 12, There are motor and solenoid drivers 19a-19i, and an electrical circuit or output interface 13 for providing control signals for the microcomputer 11 to the drivers 19a-19i.

Front right, front left, rear right and rear left wheels 51-
The wheel speed sensors 41 to 44 detect the respective rotation speeds of 54, and the signal processing circuits 18a to 18d generate electric signals representing the wheel speeds (wheel speed signals) and apply them to the input interface 12. The stop switch 45, which is closed while the brake pedal 3 is being depressed, is opened (pedal 3
The signal processing circuit 18e generates an electric signal representing "no depression: off" / closed (pedal 3 depression: on) and gives it to the input interface 12. The pressure sensor 46 detects the hydraulic pressure of the accumulator 22, and the signal processing circuit 18
f generates an electric signal (pressure signal) representing the detected pressure and supplies it to the input interface 12. Accumulator 2
Low pressure switch 47 that closes when the hydraulic pressure of 2 is below the lower limit
Open (pressure above the lower limit: OFF) / closed (below the lower limit:
An electric signal representing "ON" is generated by the signal processing circuit 18g and given to the input interface 12. Output pressure of the hydro booster 5 (1 of the output pressure of the brake master cylinder 2
20%) is closed when the wheel brake is substantially equal to or higher than a predetermined low pressure value at which braking force is generated. Open (without wheel braking: off) / close (with wheel braking: on) the power pressure switch 48.
Is generated by the signal processing circuit 18h and applied to the input interface 12.

A yaw rate sensor YA is used for the vehicle body yaw rate.
Is detected by the signal processing circuit 18i, and the signal processing circuit 18i
An electrical signal representing the rate) is generated and provided to the input interface 12. The rotation angle of the steering wheel is detected by the front wheel steering angle sensor θF, and the signal processing circuit 18j generates an electric signal representing the front wheel steering angle and supplies it to the input interface 12. The steering angle of the rear wheels is detected by the rear wheel steering angle sensor θR, and the signal processing circuit 18k generates an electric signal representing the rear wheel steering angle and gives it to the input interface 12. The signal processing circuit 1 detects the longitudinal acceleration of the vehicle body by the acceleration sensor GX.
8 l generates an electric signal representing the longitudinal acceleration and supplies it to the input interface 12. The acceleration sensor GY detects the lateral acceleration of the vehicle body, and the signal processing circuit 18m generates an electric signal representing the lateral acceleration and applies it to the input interface 12.

FIG. 3 shows an outline of the processing function of the microcomputer 11 shown in FIG. After the engine on the vehicle is started and the electric system on the vehicle is turned on and the voltage of the system is stabilized, the operating voltage is applied to the electronic control unit 10 (step 1 in FIG. 3; hereinafter, referred to as steps in parentheses). The word is omitted and only the step No. and number are described). When the operating voltage is applied, the microcomputer 11 initializes the internal register, the input / output port and the internal timer, and at the same time prepares to start the wheel brake pressure control thereafter, the internal register and the input. Predetermined data is preset in the output port and the internal timer (2). As a result, the microcomputer 11 becomes ready to read the signal input to the input interface 12. Further, the motor driver 19a is instructed to drive the electric motor 24 (pump 21), and the hydraulic pressure control of the accumulator 22 is started.

In parallel with this hydraulic pressure control, the "operation board &
Sensor reading ”(3) to“ braking force distribution control 2 ”(8)
The processing up to, that is, the wheel brake pressure control is repeatedly executed substantially at a predetermined cycle. In the hydraulic pressure control of the accumulator 22, when the pressure detected by the pressure sensor 46 reaches the upper limit value, the electric motor 24 (pump 21) is stopped and the low pressure switch 47 is closed (the hydraulic pressure is below the lower limit value). Then, the electric motor 24 (pump 21) is driven. Also, the timer 17
A timer interrupt request is generated every predetermined period (10 msec in this example). Then, when the timer interrupt request is generated, the microcomputer 11 executes the "timer interrupt" process shown in FIG.

The operation board &
Sensor reading ”(3) to“ braking force distribution control 2 ”(8)
In the "operation board & sensor reading" (3) in the processing up to the wheel brake pressure control (3), first, all the input means (sensors, switches, etc.) connected to the input interface 12 are processed. Read information and determine whether ABS control and braking force distribution control need to be executed, determine whether wheel brake pressure is to be reduced, increased, hold or not, and determine the time to continue these operations, and determine whether to end them. Information to be referred to for the determination of is generated. The main items of the reference information in this embodiment are as follows.

Information Information Source Actual Yaw Rate γ Detected Value by Yaw Rate Sensor YA Wheel Speed VwFR Detected Value by Wheel Speed Sensor 41 Wheel Speed VwFL Detected Value by Wheel Speed Sensor 42 Wheel Speed VwRR By Wheel Speed Sensor 43 Detected value Wheel speed VwRL Detected value by wheel speed sensor 44 Longitudinal acceleration Gx Detected value by longitudinal acceleration sensor GX Lateral acceleration Gy Detected value by lateral acceleration sensor GY Front wheel steering angle θf Detected value by steering angle sensor θF Rear wheel steering angle θr Steering angle Detection value by sensor θR Wheel braking ON / OFF Stop switch 45 ON / OFF Wheel acceleration dVwFR Calculated from past and present detected values by wheel speed sensor 41 Wheel acceleration dVwFL Calculated from past and present detected values by wheel speed sensor 42 Wheel Acceleration dVwRR Calculated from past and present detection values by the wheel speed sensor 43. Wheel acceleration dVwRL Calculated from past and present detection values by the wheel speed sensor 44 Estimated vehicle speed VS0 VwFR to VwRL Calculated based on past estimated vehicle speed Vehicle acceleration dVS0 Calculated based on estimated vehicle speed VS0 and past estimated vehicle speed Target yaw Calculated based on rate γ * θf and VS0 Yaw rate deviation Δγ = γ * -γ.

Judgment from vehicle turning direction DIR γ Wheel slip ratio SwFR Calculated based on VwFR and VS0 Wheel slip ratio SwFL Calculated based on VwFL and VS0 Wheel slip ratio SwRR Calculated based on VwRR and VS0 Wheel slip ratio SwRL VwRL Calculated based on VS0.

When the microcomputer 11 reads and calculates these pieces of information, the stop switch 4
Check open / close of 5 (4).

I. Control when the brake pedal 3 is not depressed: When the stop switch 45 is open (the pedal 3 is not depressed), "ABS release" (5) is executed.

"ABS release" (5): The contents of this process are shown in FIG. Here, first, the content of the register ASF that stores information whether or not the pressure control by the ABS control is started, and the content of the register BDF that stores information whether or not the pressure control by the braking force distribution control is started. Is checked (51, 52). Then, the content of the register ASF is 0
(The pressure regulation by the ABS control is not started),
Update the contents of register ASF to 0 (54)
The process of "BS release" (5) is completed, and the process proceeds to the next "braking force distribution control 1" (6). The content of register ASF is 1 (AB
Even if the pressure regulation by the S control is started), if the content of the register BDF is 1 (the pressure regulation by the braking force distribution control is started), the content of the register ASF is updated to 0. (54) This "ABS release" (5) processing ends. If the content of the register BDF is 0 (the pressure adjustment by the braking force distribution control is not started), the wheel brake pressure system (Fig. 1) is connected to the "foot brake pressure system" shown in Table 1. , Update the contents of the register ASF to 0 (54),
This "ABS release" (5) processing ends. That is, in this "ABS release" (5), since the pedal 3 is not depressed (switch 45 is off), ABS control is substantially unnecessary and is released, but pressure adjustment by the braking force distribution control is started. If so (BDF = 1), the wheel brake pressure system cannot be returned to the "foot brake pressure system", so that the connection switching of the wheel brake pressure system is not performed here.

Next, the microcomputer 11 proceeds to "braking force distribution control 1" (6).

"Braking force distribution control 1" (6): The contents of this processing are shown in FIG. Here, first, "braking force distribution calculation"
Execute (61). In this, first, the spin / drift amount of the vehicle is calculated with reference to the front and rear wheel steering angles θf and θr, the reference speed and the turning direction DIR, and the direction stability of the vehicle is stabilized from the spin / drift amount and the estimated vehicle speed VS0. Whether or not the wheel brake pressure control is required to secure the steering performance and steering performance is determined, and when it is determined that the braking force is required, braking force is applied from the steering angle θf and spin / drift to ensure directional stability and steering performance. Allocation is determined by map search. That is, wheel blur
Independent pressure regulation command (pressure increase / pressure reduction / hold assignment) CPFR to key 51, independent pressure regulation command CPFL to wheel brake 52, independent pressure regulation command CP to wheel brake 53
Independent pressure regulation command CPRL for RR and wheel brake 54
To decide. Further, when the independent pressure control command is pressure increase, the pressure increase speed, that is, the energization duty of the pressure increase valve (33, 37) is searched by map search from the spin / drift amount and the estimated vehicle speed VS0.
When the independent pressure control command is pressure reduction, the pressure reduction speed, that is, the energization duty of the pressure reduction valves (34, 38) is determined.

For any of the wheel brakes, pressure increase,
When it is determined that neither depressurization nor hold is necessary, the slip ratio of each wheel is then referred to and the acceleration slip ratio of each wheel (the wheel speed is higher than the vehicle speed when the pedal 3 is not depressed). If there is an acceleration slip above a predetermined level, the target slip ratio and slip ratio deviation (target slip ratio-actual slip ratio) of each wheel are referenced by referring to the slip ratio and acceleration of each wheel and the estimated vehicle speed.
Is calculated, and whether or not pressure increase, pressure reduction or hold of each wheel brake is required, and if pressure increase or pressure reduction is required, increase / decrease speed (energization duty) is calculated (the above is 61). Content).

In the above braking force distribution calculation, the independent pressure control commands CPFR, CPFL, CPRR, and CPRL for the front right wheel, the front left wheel, the rear right wheel, and the rear left wheel, respectively.
In this embodiment, as shown in FIG. 1, the front right wheel and the front left wheel are connected to the common pipe 31, and the rear right wheel and the rear left wheel are connected to the common pipe 32. So 4
It is actually impossible to adjust the brake pressure independently of each other. Therefore, when any of the independent pressure control commands CPFR, CPFL, CPRR, and CPRL is pressure increase, pressure decrease, or hold, the four-wheel independent control mode is changed to the front and rear two-system independent control mode. A "mode conversion" is performed for conversion (63), and the independent pressure control commands CPFR, CPFL, CPRR, and CPRL are converted to the front wheel pressure control command CPF0 and the rear wheel pressure control command CPR0.
Convert to.

When the front wheel pressure regulation command CPF0 and / or the rear wheel pressure regulation command CPR0 is pressure increase, pressure reduction or hold, a control signal for realizing the braking force distribution and the pressure increase / decrease speed is output. (64). That is, the pressure-increasing valve or the pressure-reducing valve of the pressure-increasing / reducing valve unit (334, 378) connected to the wheel brake determined as the pressure-increasing, depressurizing or holding is energized at the determined energizing duty. In the case of a hold, the pressure increasing valve is continuously energized (energization duty 100%) and the pressure reducing valve is not energized (energization duty 0%). Further, the register BDF is set to 1 indicating that the pressure is being adjusted by the braking force distribution control.
(65). The wheel brake pressure system includes only circuits related to wheel brakes that are determined to increase, decrease, or hold.
Set to the connection of the "braking force distribution control pressure system" shown in Table 1,
The other wheel brakes are "foot brake pressure" connections.

Wheel brake pressure control for ensuring directional stability and steering performance of the vehicle is unnecessary (for all wheels,
If it is determined that neither increase, decrease nor hold is required), the wheel brake pressure system is changed from the connection of the "braking force distribution control pressure system" shown in Table 1 to the connection of the "foot brake pressure system". Switching (65), 0 (no pressure adjustment by braking force distribution control) is written in the register BDF (synonymous with register clear).

Referring again to FIG. 3, while the stop switch 45 is off, the microcomputer 11 reads “sensor” (3)-“stop switch 45 on?”.
(4)-"ABS release"(5)-"Braking force distribution control 1"
(6) -Going around the loop of "Sensor reading" (3). When the stop switch 45 is turned on, the microcomputer 11 proceeds to "ABS control" (7).

II. Control when the brake pedal 3 is depressed: "ABS control" (7): This content is shown in FIGS. Here, first, the content of the register BDF is checked (71), and when the content of the register BDF is 0 (no pressure adjustment by the braking force distribution control), the upper limit of the target range of the wheel slip ratio (deceleration slip ratio because braking is being performed) is performed. 90% value
Set the lower limit value to 80% and calculate the wheel speed upper limit values V _SH and V _SS corresponding to these upper limit values and lower limit values,
The wheel acceleration reference value Gs for determining whether or not pressure reduction is required is set to -3 (deceleration because it is a negative value) (72). However, the content of the register BDF is 1 (the pressure is adjusted by the braking force distribution control).
When, the upper limit of the target range of the wheel slip ratio is 80%
Set the lower limit value to 70% and calculate the wheel speed upper limit values V _SH and V _SS corresponding to these upper limit values and lower limit values,
The wheel acceleration reference value Gs for determining whether or not pressure reduction is required is set to -4 (deceleration because it is a negative value) (73).

Next, regarding the brake 51 of the front right wheel FR, the speed VwFR of the wheel FR is set to the upper and lower limits V _SH and V.
Compared with _SS , and wheel acceleration (negative value is deceleration) dVwFR
Is compared with the acceleration reference value Gs, and the necessity of pressure reduction, pressure increase or hold is determined as follows (74FR). As a result, prior independently adjusting pressure command CPFR is generated for the right wheel; when the VwFR ≦ V _SS and dVwFR ≦ Gs reduced pressure (741,7
42,743), VwFR ≦ V _SS and dVwFR> Gs
Voltage (741, 742, 744), VwFR> V _SS and ASF = 1 (ABS control pressure adjustment is already being executed), pressure increase (741, 745, 74)
6,747), and when VwFR> V _SS and ASF = 0 (ABS control pressure adjustment is not started), no pressure adjustment is required, and when VwFR ≧ V _SH , ABS control pressure adjustment is canceled.

Next, regarding the brake 52 of the front left wheel FL, the speed VwFL of the wheel FL is set to the upper and lower limits V _SH and V.
Compared with _SS , and wheel acceleration (negative value is deceleration) dVwFL
Is compared with the acceleration reference value Gs to determine whether or not pressure reduction, pressure increase or hold is required, as in the case of the front right wheel brake 51, and the result is used as an independent pressure control command CPFL. Yes (74FL). Similarly, for the brake 53 of the rear right wheel RR, the speed VwRR of the rear wheel RR is compared with the upper and lower limit values V _SH and V _SS , and the wheel acceleration (negative value is deceleration) dV.
Comparing wRR with the acceleration reference value Gs, the same as in the case of the front right wheel brake 51 described above, the pressure reduction, pressure increase, or wheel
Whether or not the pressure is necessary is determined, and the result is used as the independent pressure regulation command CPRR (74RR). Similarly, the brake 5 of the rear left wheel RL
4, the speed VwRL of the wheel RL is increased and the lower limit value V _SH is increased.
And V _SS , and wheel acceleration (negative value is deceleration)
By comparing dVwRL with the acceleration reference value Gs, as in the case of the front right wheel brake 51 described above, it is determined whether pressure reduction, pressure increase or hold is necessary, and the result is determined as the independent pressure control command CP.
RL (74RL).

Then, the above-mentioned steps 74FR, 74
If it is determined that the pressure reduction, pressure increase, or hold is required in any of the FL, 74RR, and 74RL processes, a control signal that realizes the determined pressure regulation mode is output (77), and the ABS is selected.
Write 1 to the register ASF indicating that the pressure is being adjusted by the control (79). However, steps 74FR, 74FL, 74R
In R and 74RL, independent pressure control commands CPFR, CPFL, CPRR, and CPRL are generated for each of the four wheels, while actually possible brake pressure adjustment is independent of the two systems for the front and rear wheels. Therefore, in order to convert the 4-wheel independent control mode to the independent control mode of the front and rear two systems,
(76) to perform independent pressure regulation commands CPFR, C
PFL, CPRR, and CPRL are converted into a front wheel pressure regulation command CPF0 and a rear wheel pressure regulation command CPR0.

The wheel brake pressure system is set to the connection of the "ABS control pressure system" shown in Table 1 only for the circuits related to the wheel brakes determined to increase, decrease, or hold, and other wheels. The brake is a "foot brake pressure" connection. The pressure-increasing valve or pressure-reducing valve of the pressure-increasing / reducing valve unit (334, 378) connected to the wheel brake determined to be the pressure-increasing, decompressing or holding the energizing duty corresponding to the determined pressure-adjusting mode. Is energized. In the case of a hold, the pressure increasing valve is continuously energized (energized duty 100%) and the pressure reducing valve is deenergized (energized duty 0%).

Steps 74FR, 74FL, 7 described above
In 4RR and 74RL, independent pressure regulation command CPFR,
If none of CPFL, CPRR, and CPRL requires depressurization, boosting, or holding, ABS
If the control has been started (ASF = 1), it is not necessary and the ABS control is ended, and 0 indicating no pressure adjustment by the ABS control is written in the register ASF (78D), but before that. , During braking force distribution control (BDF =
1) is checked (78B), and if the braking force distribution control is being performed, the wheel brake pressure may be lower (than the master cylinder output pressure) due to the pressure adjustment by the ABS control. In "hydraulic pressure compensation" (78C), the pressure reducing valves 34 and 38 of the pressure increasing / reducing valve units 334 and 378 are closed, the pressure increasing valves 33 and 37 are opened, and a predetermined short time elapses (78C). During this time, the wheel brake pressure rises through the pressure increasing valve. Then, when the predetermined short time has elapsed, 0 is written in the register ASF (78D). This makes AB
The S control is substantially completed, and thereafter the braking force distribution control is in progress (B
Since DF = 1), the wheel brake pressure is adjusted by the braking force distribution control.

When the ABS control is terminated and the braking force distribution control is not in progress (BDF = 0), "hydraulic pressure compensation" is performed.
Do not execute (78C), set "Foot brake pressure system" (78E), and write 0 to register ASF (78C).
C). In this case, the wheel brake pressure system is switched to the "foot brake pressure system" connection shown in Table 1 (78E).

Next, the microcomputer 11 executes "braking force distribution control 2" (8).

"Braking force distribution control 2" (8): This content is shown in FIG. Here, first, the "braking force distribution calculation" is executed (81). The content of this "braking force distribution calculation" is the same as the "braking force distribution calculation" of step 61 described above, so a detailed description thereof is omitted here. As a result of "braking force distribution calculation", independent pressure regulation commands CPFR, CPFL, CPRR,
If either of CPRL and CPRL is pressure increase, pressure decrease or hold, the contents of register ASF are checked (8
3), if it is 1 (during pressure control by ABS control),
In order not to disturb the pressure regulation by the ABS control, the pressure regulation mode determined in the "braking force distribution calculation" (81) is not output. However, when the content of the register ASF is 0 (no pressure regulation by ABS control), "mode conversion" is carried out in order to convert the 4-wheel independent control mode to the independent control modes of the front and rear two systems. After that (84), a control output for realizing the determined pressure regulation mode is output (85). The content of the "braking force distribution output" is the same as the "braking force distribution output" of step 64 described above. When this output is performed, 1 (the pressure is adjusted by the braking force distribution control) is written in the register BDF (86).

When it is determined in the "braking force distribution calculation" (81) that neither increase, decrease, nor hold is necessary, the contents of the registers BDF and ASF are checked (87,
88). When the contents of the registers BDF and ASF are both 0 (no pressure regulation by braking force distribution control & no pressure regulation by ABS control), the wheel brake pressure system is
Switch to "Foot brake pressure system" connection shown in Table 1 (8
9), write 0 to registers ASF and BDF (9
0, 91).

If the content of the register BDF is 1, the pressure adjustment by the braking force distribution control that has already been executed is ended at this stage, but the content of the register ASF is 1 (adjustment by the ABS control). ABS)
It is highly probable that the pressure regulation by the control is induced by the pressure regulation by the braking force distribution control. Therefore, the pressure regulation by the ABS control is also completed. That is, the wheel brake pressure system is shown in Table 1.
Switch to the "foot brake pressure system" connection shown in (8
9), write 0 to registers ASF and BDF (9
0, 91).

The contents of the "mode conversion" executed in steps 63, 76 and 84 described above are shown in FIG. In this embodiment, independent pressure regulation commands CPFR, CPFL, CPRR, and C
"High select mode" is used as a mode for converting PRL into front wheel pressure regulation command CPF0 and rear wheel pressure regulation command CPR0.
There are two types (shown by H) and "row select mode" (shown by L), and this mode is independently determined for each of the front wheel side and the rear wheel side. The determination of this mode H / L will be described later.

The "mode conversion" will be described with reference to FIG. First, the front wheel pressure regulation command CPF0 is determined based on the front wheel independent pressure regulation commands CPFR and CPFL. Step 2
In 01, CPFR and CPFL are compared. If they match, CPFR is adopted as the front wheel pressure regulation command CPF0 (209), but if CPFR and CPFL are different,
Whether the conversion mode on the front wheel side is H or L is identified (202).

When the conversion mode is H, CPFR, CPFL
Among them, the front wheel pressure regulation command CPF0 is determined so as to give priority to the command on the pressure increasing side (203). That is, priority is set in the order of increasing pressure, hold, and decreasing pressure. In the combination of "increase" and "hold", priority is given to "increase", and in the combination of "hold" and "decrease". "Hold" is given priority, and "pressure boost"
In the combination of and "decompression", "increase pressure" is given priority. For example,
When CPFR is "increase" and CPFL is "hold",
Select "increase" of CPFR with high priority and adopt it to front wheel pressure regulation command CPF0.

When the conversion mode is L, CPFR, CPFL
Among them, the front wheel pressure regulation command CPF0 is determined so as to prioritize the pressure reduction side command (204). That is, the order of priority is set in the order of depressurization, hold, and pressure increase. In the combination of "pressure increase" and "hold", "hold" is given priority, and "hold" is given.
In the combination of and "decompression", "reduction" is given priority, and in the combination of "increase" and "decompression", "decompression" is given priority. For example, C
If the PFR is "increase" and the CPFL is "hold", the "hold" of CPFL having a higher priority is selected and adopted as the front wheel pressure regulation command CPF0.

Next, the rear wheel pressure regulation command CPR0 is determined based on the independent control instructions CPRR and CPRL on the rear wheel side. In step 205, CPRR and CPRL are compared. If they match, CPRR is adopted as the front wheel pressure regulation command CPR0 (210), but if CPRR and CPRL are different, it is discriminated whether the rear wheel conversion mode is H or L ( Two
06).

When the conversion mode is H, CPRR, CPRL
Among them, the front wheel pressure regulation command CPR0 is determined so that the command on the pressure increasing side is prioritized (207). That is, priority is set in the order of increasing pressure, hold, and decreasing pressure. In the combination of "increase" and "hold", priority is given to "increase", and in the combination of "hold" and "decrease". "Hold" is given priority, and "pressure boost"
In the combination of and "decompression", "increase pressure" is given priority. For example,
If CPRR is "increase" and CPRL is "hold",
"Increase" of CPR R with higher priority is selected and adopted for rear wheel pressure regulation command CPR0.

When the conversion mode is L, CPRR, CPRL
Among them, the rear wheel pressure regulation command CPR0 is determined so as to give priority to the pressure reduction side command (208). That is, the order of priority is set in the order of depressurization, hold, and pressure increase. In the combination of "pressure increase" and "hold", "hold" is given priority, and "hold" is given.
In the combination of and "decompression", "reduction" is given priority, and in the combination of "increase" and "decompression", "decompression" is given priority. For example, C
When PRR is "increase" and CPRL is "hold", "hold" of CPRL having a higher priority is selected and adopted as the rear wheel pressure regulation command CPR0.

Front wheel pressure regulation command CP generated by the processing of FIG.
The pressure increase / decrease valve unit 334 is adjusted in accordance with F0, and the pressure increase / decrease valve unit 3 is adjusted in accordance with the rear wheel pressure adjustment command CPR0.
A pressure regulation of 78 is carried out. Therefore, as compared with the case where the brake pressure is adjusted independently for the four wheels, one of the front right wheel and the front left wheel and one of the rear right wheel and the rear right wheel can be
The pressure will deviate slightly from the optimum state. And
If the brake pressure is excessively high, the wheels are likely to be locked, and if the brake pressure is excessively low, the braking distance is extended.
In order to minimize the adverse effect of such a defect on driving, the mode H / L in the above "mode conversion" is used.
It is necessary to switch the selection of (1) according to the running state and driving state of the vehicle at that time. This switching is executed by the "timer interrupt" process shown in FIG.

The "timer interrupt" process will be described with reference to FIG. In this embodiment, the running state and driving state of the vehicle at that time are classified into the following four types.

State A: The absolute value of the acceleration dVS0 of the estimated vehicle speed is larger than the threshold value k1 when neither the state B nor the state C is satisfied. State B: When not the state C, the absolute value of the front wheel steering angle θf is larger than the threshold value k2. Large, differential value (angular velocity) of the front wheel steering angle d
State C: Absolute value of θf is larger than threshold value k3 State C: Absolute value of lateral acceleration Gy is larger than threshold value k4 State D: State other than A, B, and C (normal state) Above “state C” If, then the process goes through step 301 to step 311. Further, in the “state B”, the process proceeds to step 313 through steps 301-303-304. In the case of "state A", steps 301-303-
(304) -305-306- (308)-(309)
Through -310, proceed to step 312 or 313.
Furthermore, in the "state D", step 301-30
3- (304) -305 and proceed to step 312. In step 311, H (high select) is set in the mode of the front wheels, and H is also set in the mode of the rear wheels. At step 312, H is set in the front wheel mode and L (low select) is set in the rear wheel mode. In step 313, L is set in the front wheel mode and L is also set in the rear wheel mode.

In the "state D", it is desirable that the front wheel mode is H and the rear wheel mode is L. That is, if both the front wheel side and the rear wheel side are set to H, the braking force (break pressure) of the four wheels as a whole becomes excessive compared to the optimum state, and the front wheel side and the rear wheel side are If you set both modes to L,
Although the braking force of the four wheels as a whole is too small compared to the optimal state, if one of the front wheel side and the rear wheel side is set to H and the other mode is set to L, the four wheels are set. The total braking force approaches the optimum state. In addition, when the weight distribution on the front side is larger than that on the rear side of the vehicle, as in a car in which an engine is installed on the front side of the vehicle and driven by the rear wheels, the braking force on the front wheel side rather than the rear wheel side It is better to increase the distribution, and if the rear wheel locks earlier than the front wheel, spin tends to occur, so in order to prevent the rear wheel from locking, the front wheel mode is set to H and the rear wheel side It is good to set the mode to L.

However, in the "state C", the lateral turning acceleration Gy is in a limit turning state in which the lateral acceleration is large, and in particular, the rear wheels are
Since the command of the wheel on the inside of the turning where the load is removed is low-selected, the braking force is extremely reduced. Therefore, in order to shorten the braking distance, both the front wheel side and rear wheel side modes are set to H.
To

In the "state B", the driver is actually operating the steering wheel at high speed. Therefore, it is necessary to make the vehicle turnable in accordance with the operation. When the wheels are locked, side slippage occurs and steering performance deteriorates. Therefore, in this case, in order to prevent the wheels from being locked, it is desirable that both the front wheel side mode and the rear wheel side mode be L.

Further, in the above-mentioned "state A", there is a very high possibility that the wheels actually lock. When the wheels are locked for a long time, only the same part of the tire is worn due to friction with the ground, resulting in uneven wear of the tire. When uneven wear occurs, the running stability after that deteriorates significantly. In order to prevent uneven wear of the tires, the wheels may be controlled so as to be unlocked from time to time. That is, when the mode is H, there is a high possibility that the wheels will be locked,
When the mode is L, the lock is hard to occur, so the mode is
By alternately assigning H and L to the mode, that is, periodically, the wheels are unlocked when the mode is L, and uneven wear of the tire is prevented.

In the process shown in FIG. 10, when the state becomes "state A" from another state, the process proceeds to step 309. Here, first, the estimated vehicle speed VS0 is substituted into a predetermined function f () as a parameter to calculate it, and as a result, Rh is obtained. The function f () is defined as shown in FIG. 12 in this embodiment. Rh is the ratio (Th / T0) between the control cycle T0 for mode switching and the time Th for allocating the mode H. Counters CNT and CNH are used to identify the times T0 and Th, respectively. The numerical value NT (constant) corresponding to the time T0 is stored in the counter CNT, and the numerical value NH corresponding to the time Th is stored in the counter CNH. This numerical value NH is calculated from the ratios Rh and NT.

The counter CNT keeps counting until it reaches 0.
It is decremented (-1) every time step 315 is executed (every 10 msec), and the counter CNH is decremented every time step 317 is executed until it becomes zero. FIG. 13 shows an example of changes in the contents of the counters CNT and CNH. Then, when the counter CNH is not 0 (the period Th in the cycle T0), step 312 is executed, and when the counter CNH is 0 (the period after Th in the cycle T0), step 313 is executed. . That is, the mode on the rear wheel side is always L, but the mode on the front wheel side is set to H during the period Th in the cycle T0, and is set to L during the period after Th in the cycle T0. Is set to. That is, H and L are alternately set in the mode on the front wheel side, and the switching is repeated in the cycle of T0. Further, the ratio of the mode H period and the mode L period changes according to the estimated vehicle speed VS0.

The ratio Th is updated (309) immediately after the state becomes “state A” from another state and when the counter CNT becomes 0 (every time T0 elapses).

When the mode on the front wheel side is H, as shown in FIG.
Every time the processing of 0 is executed, the counter CN0 is incremented (318, 319). When the mode on the front wheel side is L, the counter CN0 is cleared. Then, when the value of the counter CN0 becomes larger than the predetermined threshold value k5, L is set in the mode on the front wheel side, and the counter CN0 is set.
Clear 0 (321, 322). Therefore, if the mode of the front wheels is H for a predetermined time (corresponding to k5) or more, the execution of step 322 temporarily sets the mode of the front wheels to L. When step 322 is executed, the state where the mode on the front wheel side is L is maintained for a predetermined time. This control is executed to prevent uneven wear of the tire, as in the case of the "state A", and the "state A", "state B", "state C", and "state D" are performed. It works in both cases.

In the above embodiment, the lateral acceleration G is detected in step 305 in order to detect the limit turning state.
Although y is referred to, the limit turning state can be detected by another method. In the modified embodiment shown in FIG. 11, in step 301B, the limit turning state is determined by comparing the absolute value of ΔVF, which is the deviation between the front right wheel speed VwFR and the front left wheel speed VwFL, with a threshold value k6. It is detecting. In this way, the lateral acceleration sensor becomes unnecessary.

In the embodiment shown in FIG. 10, the steps 318 to 322 (measures against uneven wear of the tire) are carried out only on the front wheel side, but the same processing is carried out on the rear wheel side. You may.

Next, one modified embodiment will be described. FIG. 14 shows the brake hydraulic circuit of this embodiment. It should be noted that, in FIG. 14, the same components as those in the above-described embodiment are designated by the same reference numerals. In this embodiment, since the comparatively simple ABS control utilizing only the output pressure of the brake master cylinder is executed, the structure of the hydraulic circuit is greatly simplified as compared with FIG.

In FIG. 14, reference numeral 71 is a tandem type master cylinder, 72 is a vacuum type booster, and 73 is a master cylinder reservoir. Also, 134a, 136
a is a normally open solenoid valve, 134b and 136b are normally closed solenoid valves, 132a and 132b are reservoirs for reducing braking pressure,
P1 and P2 are pumps, CV1, CV2, CV3 and CV4
Is a check valve.

The hydraulic pressure that appears at one output port of the master cylinder when the brake pedal 3 is depressed is the solenoid valve 13
Front right wheel brake 51 and front left wheel brake 5 through 4a
2 is applied. In the ABS control, the solenoid valve 134
By energizing the electric coil of a, the solenoid valve 134a
Is closed, and the increase of the hydraulic pressure applied to the front right wheel brake 51 and the front left wheel brake 52 is stopped. In addition, the solenoid valve 134
By energizing the electric coil of the solenoid valve 134b while energizing the electric coil of a, the solenoid valve 134b is opened and the hydraulic pressure is released to the reservoir 132a.
Also, the hydraulic pressure applied to the front left wheel brake 52 is reduced. That is, the front right wheel brake 51 and the front left wheel brake 52
It is possible to increase, decrease, and hold the hydraulic pressure applied to the. The brake liquid (oil) accumulated in the reservoir 132a is
It is returned to the flow path on the master cylinder 71 side by the pump P1. The pump P1 is driven by the electric motor 24B. Similarly, the hydraulic pressure that appears in the other output port of the master cylinder when the brake pedal 3 is depressed passes through the proportioning valve 6 and the solenoid valve 136a to the rear right wheel brake 53 and the rear left wheel brake 54. Is applied. AB
In the S control, by energizing the electric coil of the solenoid valve 136a, the solenoid valve 136a is closed and the rear right wheel brake is operated.
The increase of the hydraulic pressure applied to the key 53 and the rear left wheel brake 54 stops. Further, by energizing the electric coil of the solenoid valve 136b while energizing the electric coil of the solenoid valve 136a, the solenoid valve 136b is opened and the hydraulic pressure is released to the reservoir 132b. Therefore, the rear right wheel brake 53 and the rear left wheel 53b. Break 5
The hydraulic pressure applied to 4 is reduced. That is, the rear right wheel blur
It is possible to increase, decrease, and hold the hydraulic pressure applied to the key 53 and the rear left wheel brake 54. Reservoir 132
The brake liquid accumulated in b is propelled by the pump P2.
It is returned to the flow path on the side of the switching valve 6. Pump P
2 is driven by the same electric motor 24B as P1.

The electronic control unit 140 for controlling the hydraulic circuit shown in FIG. 14 has substantially the same structure as the electronic control unit 10 shown in FIG. Although not shown, the same various sensors as in FIG. 2 are connected to the input of the electronic control unit 140, and the solenoid valves 134a, 134b, and
The motors 24B are connected to 136a and 136b. The contents of the processing executed by the electronic control unit 140 are shown in FIG.
However, the "braking force distribution control 1" at step 6 and the "braking force distribution control 2" at step 8 shown in FIG. 3 are omitted. Solenoid valves 134a, 134b, 136a and 1
36b is controlled by the solenoid valves 33, 34, 3 of FIG. 1, respectively.
This is the same as the control of 7 and 38.

In the embodiment shown in FIG. 1, a vacuum booster may be used instead of the hydro booster.

[0098]

As described above, according to the present invention, the conversion mode selecting means (311, 312, 313) generates the first pressure adjusting command and the second pressure adjusting command according to the state of the vehicle at that time. Since the selection (H / L) of the conversion mode instructing the pressure adjustment command conversion means is automatically switched for each generation of the pressure adjustment command, the braking pressure is adjusted so that the most preferable result can be obtained at that time. It is possible to control.

In the second aspect of the invention, the first conversion mode is selected for both the generation of the first pressure regulation command and the generation of the second pressure regulation command in the limit turning state. Therefore, the required braking force can be reliably obtained, and the braking distance can be prevented from being extended more than necessary.

According to the third aspect of the invention, when the driver performs a relatively fast steering operation, the second pressure control command is generated in response to both the first pressure control command generation and the second pressure control command generation. Since the control is performed so as to select the conversion mode, the wheels are reliably prevented from being locked and good steering performance is obtained.

According to the fourth aspect of the present invention, when there is a high possibility that the wheels will be locked, the first conversion mode and the second conversion mode are used to generate the first pressure adjustment command. Since the second conversion mode is selected for the generation of the second pressure adjusting command, even if the wheel is locked, it occurs intermittently. The wheels are prevented from being locked for a long time and uneven wear of the tire is prevented.

According to the fifth aspect of the present invention, when there is a high possibility that the wheels will be locked, the first conversion mode and the second conversion mode are used to generate the first pressure adjustment command. Alternately and repeatedly, the ratio (Rh) between the time for selecting the first conversion mode and the time for selecting the second conversion mode is determined according to the detected vehicle speed (VS0). Therefore, uneven wear of the tire can be prevented more effectively.

According to the sixth aspect of the invention, when the first conversion mode is continuously selected for a predetermined time (k5) or more (when there is a high possibility that the wheels will be locked), the first conversion mode is temporarily set. Since the conversion mode of 2 is selected, the occurrence of uneven wear of the tire can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing a hydraulic circuit of a brake control system according to an embodiment.

FIG. 2 is a block diagram showing an electric circuit for controlling the hydraulic circuit of FIG.

FIG. 3 is a flowchart showing the operation of the CPU 14 of FIG.
It is

FIG. 4 is a flowchart showing the contents of step 5 in FIG.
It is

5 is a flowchart showing the contents of step 6 of FIG.
It is

FIG. 6 is a flowchart showing a part of the contents of step 7 in FIG.
It is a chart.

FIG. 7 is a flow chart showing the rest of the contents of step 7 of FIG.
It is a chart.

FIG. 8 is a flowchart showing the contents of step 8 of FIG.
It is

FIG. 9 is a flowchart showing a subroutine of steps 63, 76 and 84.

10 is a flowchart showing a timer interrupt process of the CPU 14 of FIG.

11 is a flow chart showing a modified example of FIG.

FIG. 12 is a graph showing the relationship between VS0 and Rh.

FIG. 13 shows changes and values of counters CNT and CNH.
It is a time chart showing a change in mode.

FIG. 14 is a block diagram showing a hydraulic circuit of a brake control system of a modified example.

[Explanation of symbols]

2: Brake master cylinder 3: Brake
Key pedal 4: Break liquid reservoir 5: Hydro booster 6: Proportional control valve 10: Electronic control device 11: Micro computer 12: Input interface 13: Output interface 14: CP
U 15: ROM 16: RA
M 17: Timer 18a-1
8m: Signal processing circuit 19a to 19i: Motor driver and solenoid driver 20: High pressure source 21: Pump 22: Accumulator 23: Relief valve 24: Electric motor 25: Check valve 31: Front wheel side pipe 32: Rear wheel side piping 33, 37: solenoid valve for increasing pressure 34, 3
8: Pressure reducing solenoid valve 334, 378: Pressure increasing / decreasing valve unit 41-44: Wheel speed sensor 45: Stop switch 46: Pressure sensor 47: Low pressure switch 48: Power pressure switch YA: Yo
Rate sensor θF: Front wheel steering angle sensor θR: Rear wheel steering angle sensor GX: Front / rear acceleration sensor GY: Lateral acceleration sensor 51 to 54: Wheel brakes 62 to 6
5: Solenoid switching valve 71: Tandem type master cylinder 72: Vacuum type booster 73: Master cylinder reservoir 134a, 136a: Normally open type solenoid valve 134b, 136b: Normally closed type solenoid valve 132a , 132b: Reservoir for reducing braking pressure P1, P2: Pump CV1, CV2, CV3, CV4: Check valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shin Sugiura Shingo, Asahi-cho, 2-chome, Kariya city, Aichi Prefecture Aisin Seiki Co., Ltd. (72) Inventor Noriyama Yamazaki 2-chome, Asahi-cho, Kariya city, Aichi prefecture Address Aisin Seiki Co., Ltd. (72) Inventor Akio Sakai 2-chome, Asahi-cho, Kariya City, Aichi Aisin Seiki Co., Ltd.

Claims (6)

[Claims] 1. A front pipe for commonly connecting a means for braking rotation of a left front wheel and a means for braking rotation of a right front wheel of a vehicle, a means for braking rotation of a left rear wheel of the vehicle, and a right side. A rear pipe for commonly connecting a means for braking the rotation of the rear wheel, a first pressure adjusting device for adjusting the first pressure applied to the front pipe, and a second pipe for applying the rear pipe. In a wheel brake pressure control device having a second pressure adjusting means for adjusting the pressure: at least the rotational speed of each of the four wheels of the left front wheel, right front wheel, left rear wheel and right rear wheel of the vehicle State detecting means including means for detecting; a pressure adjusting command for generating an independent pressure adjusting command for each of the four wheels of the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel based on the information detected by the state detecting means. Generating means: Four independent pressure regulating fingers generated by the pressure regulating command generating means In the command, a first pressure regulation command for the first pressure is generated based on a first pressure regulation command for the left front wheel and the right front wheel, and a second pressure regulation command for the left rear wheel and the right rear wheel is generated. A pressure regulation command converting means for generating a second pressure regulation command for the second pressure based on the pressure regulation command; and for each of the first and second sets of independent pressure regulation commands Instructing the pressure adjustment command conversion means to select either the first conversion mode which gives priority to the command on the pressure increasing side or the second conversion mode which gives priority to the command on the pressure reducing side. At the same time, depending on the state of the vehicle at that time, the selection of the conversion mode for instructing the pressure adjustment command conversion means with respect to each of the generation of the first pressure adjustment command and the generation of the second pressure adjustment command is automatically performed. A wheel brake pressure control device, characterized in that a conversion mode selecting means for switching to the above is provided. 2. The conversion mode selecting means, when the absolute value of the acceleration in the left-right direction of the vehicle body is greater than or equal to a first threshold value, or the absolute value of the rotational speed difference between the left front wheel and the right front wheel is the second. If the threshold value is equal to or more than the threshold value, the first conversion mode is selected for both the generation of the first pressure regulation command and the generation of the second pressure regulation command. A wheel brake pressure control device as described. 3. The conversion mode selecting means detects a steering angle, further obtains a differential value of the steering angle, the absolute value of the steering angle is equal to or larger than a third threshold value, and the differential of the steering angle is further obtained. When the absolute value of the value is greater than or equal to the fourth threshold value, the second conversion mode is set for both the generation of the first pressure regulation command and the generation of the second pressure regulation command. The wheel brake pressure control device according to claim 1, which is selected. 4. The conversion mode selecting means detects a vehicle body speed, further obtains a differential value of the vehicle body speed, and when the absolute value of the differential value of the vehicle body speed is not less than a fifth threshold value. Is the first conversion mode for the generation of the first pressure adjustment command.
2. The wheel according to claim 1, wherein the mode and the second conversion mode are alternately and repeatedly selected, and the second conversion mode is selected for the generation of the second pressure adjusting command. Brake pressure control device. 5. The conversion mode selecting means, when the absolute value of the differential value of the vehicle body speed is greater than or equal to a fifth threshold value, in response to the generation of the first pressure adjustment command, the conversion mode selecting means The first conversion mode and the second conversion mode are alternately and repeatedly selected, and the time for selecting the first conversion mode and the second conversion mode are selected.
5. The wheel brake pressure control device according to claim 4, wherein the ratio of the time to select the vehicle speed is determined according to the detected vehicle speed. 6. The conversion mode selecting means temporarily, when the first conversion mode is continuously selected for a predetermined time or longer in response to the generation of the first pressure adjusting command, The wheel brake pressure control device according to claim 1, claim 2, claim 3, or claim 4 forcibly selecting the second conversion mode.