JPH09221019A - Anti-lock braking device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anti-lock braking system of facile improvement in driving stability on a down slope road as restraining a driver from feeling a free running. SOLUTION: An anti-lock system equipped with a decompression means (step 10 and the like) for controlling decompression of a a wheel cylinder is equipped with a detecting means (step 3) for detecting that a vehicle is runing on a down slope road and a decompression restraining means (step 4) for restaining by the decompression control means the decompression degree with respect to the wheel cylinder provided on a rear wheel when the detecting means detects that the vehicle is running on the down slope road.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antilock brake system (hereinafter referred to as ABS), and more particularly to control of ABS on a downhill road.

[0002]

2. Description of the Related Art ABS is a brake system that improves the steering stability of a vehicle by controlling the hydraulic pressure of all wheel cylinders provided on each wheel so that the wheels do not lock when the vehicle is braked. . That is, when the vehicle is braked, it is determined based on the wheel acceleration or the like whether or not the wheel enters the lock tendency, and when it is determined that the wheel enters the lock tendency, the hydraulic pressure of the wheel cylinder is reduced to prevent the wheel from being locked. It is a thing.

When ABS control is performed on a downhill road, the hydraulic pressure of the wheel cylinder is reduced and the wheel speed increases, which may give the driver a feeling of idling.

Therefore, in order to solve such a problem, there has been proposed a technique for prohibiting ABS control on a downhill road. That is, as disclosed in Japanese Patent Publication No. 6-503525, the determination of descending slope is made based on vehicle deceleration, wheel acceleration, etc., and ABS control for all wheels is prohibited.

[0005]

However, if the ABS control is prohibited on the downhill road, each wheel tends to lock when the vehicle is suddenly braked. Therefore, a feeling of idling is given to the driver due to the ABS control. Although it is possible to suppress the application, it may be difficult to improve the steering stability.

An object of the present invention is to provide an ABS which can easily improve the steering stability while suppressing the feeling of idling given to a driver on a downhill road.

[0007]

An antilock brake system according to a first aspect of the present invention is an antilock brake system including pressure reducing control means for controlling pressure reduction of a wheel cylinder, and detects that a vehicle is traveling on a downhill road. And a detection means that suppresses the degree of pressure reduction by the pressure reduction control means only to the wheel cylinders provided on the non-steered wheels when the vehicle detects that the vehicle is traveling on a downhill road. It is characterized by including a reduced pressure suppressing means.

According to the anti-lock brake system of the present invention, when the detection means detects that the vehicle is traveling on a downhill road, the pressure reduction control means applies the pressure reduction control means to the rear wheels. Since the degree of decompression of the wheel cylinders provided is suppressed, ABS control for the rear wheels is less likely to be performed, and the feeling of idling given to the driver can be suppressed. On the other hand, since the degree of pressure reduction is not suppressed for the wheel cylinders provided for the steered wheels, the ABS for the steered wheels is not controlled.
Control is done as usual. Therefore, it is easy to improve steering stability.

An antilock brake system according to a second aspect of the present invention is an antilock brake system including pressure reducing control means for controlling pressure reduction of a wheel cylinder, and detecting means for detecting that the vehicle is traveling on a downhill road. And a pressure reduction suppressing means for suppressing the degree of pressure reduction of the wheel cylinder by the pressure reduction control means when the detection means detects that the vehicle is traveling on a downhill road. It is characterized in that the degree of suppression of pressure reduction for the wheel cylinders provided for the wheels is made smaller than the degree of suppression of pressure reduction for the wheel cylinders provided for non-steering.

According to the second aspect of the anti-lock brake system, the degree of pressure reduction to the wheel cylinders provided at the rear wheels and the front wheels is suppressed by the pressure reduction suppressing means, so that the ABS control for each wheel is performed. This is less likely to be done, and the feeling of idling can be suppressed more than in the antilock brake system according to the first aspect. Moreover, since the degree of pressure reduction suppression for the front wheels by the pressure reduction suppression means is made smaller than the degree of pressure reduction suppression for the rear wheels, steering stability is not impaired.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 shows an A according to an embodiment of the present invention.
It is a system configuration diagram of a BS. In FIG.
0 indicates an ABS computer.
The S computer 10 includes a front right wheel 12, a front left wheel 14, a rear right wheel 16, and a rear left wheel 18, each of which includes a front right speed sensor 20, a front left speed sensor 22, and a rear right speed sensor 24.
The wheel speed signal V _W output from each of the rear left speed sensor 26 is input.

Reference numeral 28 denotes a G sensor, which is capable of detecting acceleration and deceleration, and outputs a positive value when acceleration is detected. It is input to the ABS computer 10. On the other hand, when the deceleration is detected, a negative value is output and input to the ABS computer 10. This G sensor is supposed to output a detection value below a predetermined frequency.

Further, the reference numeral 30 indicates a brake pedal, and the brake fluid pressure generated by the master cylinder 32 in accordance with the depression amount of the brake pedal 30 is applied to each wheel 12 via the ABS actuator 34.
It is transmitted to the front right wheel cylinder 36, the front left wheel cylinder 38, the rear right wheel cylinder 40, and the rear left wheel cylinder 42 which are provided in 14, 16, and 18, respectively.

Reference numeral 82 is an ABS warning lamp. ABS computer 10
It has a function of self-determining whether or not there is an abnormality in the BS. When it is determined that an abnormality has occurred, the ABS warning lamp 82 is turned on based on the output signal of the ABS computer 10.

The ABS computer 10 is an ABS computer.
ABS control is performed by outputting a control signal to the actuator 34 and controlling the hydraulic pressure of each wheel cylinder 36, 38, 40 and 42 provided on each wheel 12, 14, 16 and 18.

FIG. 2 shows an embodiment A of the present invention.
It is a figure which shows the hydraulic pressure path and control system of BS. As shown in this figure, the ABS hydraulic line is based on the X piping system. That is, the master cylinder 32 is provided with first and second independent pressurizing chambers, and hydraulic pressure is generated in each of the two pressurizing chambers in response to the driver's depression of the brake pedal 30. To be

The front left wheel cylinder 38 is connected to the first pressurizing chamber of the master cylinder 32 via a front left holding solenoid valve 44, and the rear right wheel cylinder 40 is connected to a rear right holding solenoid valve 46. The front left wheel cylinder 38 and the rear right wheel cylinder 40 are connected to the reservoir 52 via the front left pressure reducing solenoid valve 48 and the rear right pressure reducing solenoid valve 50, respectively, to form a first brake system. .

On the other hand, the rear left wheel cylinder 4 is provided in the second pressurizing chamber via a rear left holding solenoid valve 60.
2, the front right wheel cylinder 36 is connected via a front right holding solenoid valve 62, and the rear left wheel cylinder 42 and the front right wheel cylinder 3 are connected to each other.
6 is connected to a reservoir 70 via a rear left pressure reducing solenoid valve 64 and a front right pressure reducing solenoid valve 66, respectively, to form a second brake system.

Each holding solenoid valve 44, 4
6, 60, 62 and respective pressure reducing solenoid valves 48, 5
In response to a control signal from the ABS computer 10, 0, 64, and 66 turn on / off the current to the coil provided in each solenoid valve, and operate the plunger by the attraction force or spring force generated in this coil. As a result, the port provided in each solenoid valve is opened and closed to switch the hydraulic passage to the pressure reducing mode, the holding mode, the pressure increasing mode, and the like.

First, the first brake system will be described. The hydraulic pressure paths connected to the above-mentioned first pressurizing chamber are respectively connected to the orifice 44a of the front left holding solenoid valve 44 and the orifice 46a of the rear right holding solenoid valve 46. Further, the port 44b of the front left holding solenoid valve 44 and the front left wheel cylinder 38 are connected by a hydraulic passage, and the port 46b of the rear right holding solenoid valve 46 and the rear right wheel cylinder 40 are dual. It is connected by a hydraulic passage via a P valve 80.

Here, the dual P valve 80 has a brake fluid on the rear right wheel cylinder 40 side and the master cylinder 32 when the hydraulic pressure of the master cylinder 32 reaches a predetermined constant value (folding hydraulic pressure). This hydraulic pressure control valve separates the brake fluid on the side of the vehicle and the hydraulic pressure on the rear right wheel cylinder 40 side to a small ratio compared to the increase of hydraulic pressure on the side of the master cylinder 32.

Further, the check valve 44c of the front left holding solenoid valve 44 blocks the inflow of brake fluid from the outside to the inside of the front left holding solenoid valve 44, and the front left holding solenoid valve 44.
A valve that allows the outflow of brake fluid from the inside to the outside, the first pressure chamber and the orifice 44a.
It is connected in the middle of the hydraulic path connecting to and. Further, the check valve 46c of the rear right holding solenoid valve 46 blocks the inflow of brake fluid from the outside to the inside of the rear right holding solenoid valve 46, and prevents the brake fluid from flowing from the inside to the outside of the rear right holding solenoid valve 46. It is a valve that allows outflow, and is connected in the middle of the hydraulic passage that connects the first pressurizing chamber and the orifice 46a.

The port 48a of the front left depressurizing solenoid valve 48 is connected in the middle of the hydraulic passage connecting the port 44b of the front left holding solenoid valve 44 and the front left wheel cylinder 38, and is used for rear right depressurizing. The port 50a of the solenoid valve 50 is connected in the middle of a hydraulic pressure passage that connects the port 46b of the rear right holding solenoid valve 46 and the rear right wheel cylinder 40.

Further, the orifice 48b of the front left depressurizing solenoid valve 48 and the orifice 50b of the rear right depressurizing solenoid valve 50 are connected to the reservoir 52 via a hydraulic pressure passage. Here, the reservoir 52 accommodates the brake fluid that is circulated from the front left pressure reducing solenoid valve 48 and the rear right pressure reducing solenoid valve 50 via the hydraulic pressure passage. The reservoir 52 is connected to the pressurizing chamber of the master cylinder 32 by a hydraulic pressure passage via a check valve 54, a pump 56 and a check valve 58.

Next, the second brake system will be described. The above-described second pressurizing chamber of the master cylinder 32 and the front right wheel cylinder 36 are connected via a front right holding solenoid valve 62, and the second pressurizing chamber of the master cylinder 32 and the rear left wheel cylinder 42 are connected. Are connected via a rear left holding solenoid valve 60.

Further, the front right wheel cylinder 36,
The rear left wheel cylinder 42 is connected to the reservoir 70 via a front right pressure reducing solenoid valve 66 and a rear left pressure reducing solenoid valve 64, respectively. Further, the reservoir 70 includes a check valve 72 and a pump 74.
Also, it is connected to the second pressurizing chamber via a check valve 78. The detailed configuration of the second brake system is the same as that of the first brake system, and thus detailed description thereof is omitted.

FIG. 3 shows an A according to the embodiment of the present invention.
It is a block diagram which shows the structure of a BS computer. The ABS computer includes a central processing unit (CPU) 10a, and the CPU 10a includes
A read-only memory (ROM) 10b for storing a program for ABS control, a reference slip amount ΔVr used for ABS control, a correction coefficient k for correcting the reference slip amount, and the like via the bus line 10f, and each speed described above. Output signals from the sensors 20, 22, 24, 26 and the G sensor 28, a flag FABS indicating whether or not ABS control is performed
Random access memory (RAM) 10c for storing (ABS control is executed when FABS = 1, ABS control is not executed when FABS = 0) and the like, each of the speed sensors 20 and 2 described above.
Input section 10d including a multiplexer or the like for selectively outputting the output signals from 2, 24, 26 and G sensor 28 to CPU 10a, and an output section for outputting a control signal to ABS actuator 34 and ABS warning lamp 82. 10e is connected.

The CPU 10a receives the output signals from the speed sensors 20, 22, 24, 26 and the G sensor 28 via the input unit 10d, and outputs the output unit 10e based on a program for ABS control. A control signal is output to the ABS actuator 34 via the.

Next, referring to FIG. 2, the flow of the brake fluid in the hydraulic pressure passage in each of the braking modes, that is, the normal braking mode, the pressure reducing mode, the holding mode and the pressure increasing mode will be described. In the hydraulic path, the first brake system has two systems, a front left wheel system and a rear right wheel system, and the second brake system has two systems, a front right wheel system and a rear left wheel system. However, since the operation is the same in both cases, the front left wheel system will be described as an example.

First, in the normal brake mode, A
Since no control signal is input from the BS computer 10 to the ABS actuator 34, the port 44b of the front left holding solenoid valve 44 is opened and the port 44a of the front left pressure reducing solenoid valve 48 is closed. Therefore, when the hydraulic pressure in the master cylinder 32 increases due to the depression of the brake pedal 30,
The brake fluid includes an orifice 44a and a port 44.
b, sent by the route of the wheel cylinder 38. In this case, since the pump 56 has the check valve 58, the brake fluid is not sent.

When the brake pedal 30 is released,
The brake fluid of the front left wheel cylinder 38 is the port 44b of the front left holding solenoid valve 44.
And to the master cylinder 32 via both the path through the orifice 44a and the path through the front left wheel cylinder 38 and the check valve 44c.

Next, in the depressurization mode, the orifice 44a of the front left holding solenoid valve 44 is closed and the orifice 48b of the front left depressurizing solenoid valve 48 is opened by the control signal from the ABS computer 10. It becomes a state. Therefore, the brake fluid of the front left wheel cylinder 38 flows through the path of the port 48a of the front left pressure reducing solenoid valve 48, the orifice 48b, and the reservoir 52, and the hydraulic pressure of the front left wheel cylinder 38 is reduced.

During the ABS control,
Since the ABS computer 10 always outputs an operation signal to the pump motor 82 (see FIG. 3), the reservoir 52
The brake fluid collected in the above is pumped out by the pump 56 and returned to the master cylinder 32.

Next, in the holding mode, when the hydraulic pressure in the front left wheel cylinder 38 is reduced or increased to the required hydraulic pressure, the orifice of the front left holding solenoid valve 44 is generated by a control signal from the ABS computer 10. 44a and the orifice 48b of the front left pressure reducing solenoid valve 48 are closed at the same time. As a result, the front left wheel cylinder 38 is blocked from both the master cylinder 32 side and reservoir 52 side paths, and the hydraulic pressure of the front left wheel cylinder 38 is maintained.

Next, in the pressure increasing mode, the orifice 44a of the front left holding solenoid valve 44 is opened and the orifice 48b of the front left pressure reducing solenoid valve 48 is closed by the control signal from the ABS computer 10. It will be in a state of being. Therefore, in the same state as in the normal brake mode, the brake fluid of the master cylinder 32 is sent to the front left wheel cylinder 38, and the hydraulic pressure of this wheel cylinder 38 is increased.
At this time, if the brake fluid remains in the reservoir 52, it is pumped up by the pump 56 and sent to the front left wheel cylinder 38.

The control of the speed of increasing the hydraulic pressure is performed by alternately repeating this pressure increasing mode and the above-mentioned holding mode.

Next, according to the flow chart of the ABS control of FIG. 4 and the conceptual diagram of the ABS control of FIG. 5, the case where the driver suddenly brakes by depressing the brake pedal 30 hard is taken as an example, and the present invention is carried out. The ABS control according to this mode will be described. Although FIG. 4 illustrates the ABS control of the rear wheels, the following description will be given taking the rear right wheel 16 as an example.

First, the wheel speed V _W of the rear right wheel 16, the acceleration / deceleration G, the estimated vehicle speed V _SO and the reference slip amount ΔV _r are read (step 1). That is, the RAM 10c
From the rear right speed sensor 24, the wheel speed V _W stored and stored based on the output signal of the rear right speed sensor 24, the acceleration / deceleration G stored and calculated based on the output signal of the G sensor 28, and the speed sensors 20, 22, 24, The estimated vehicle body speed V _SO calculated and stored on the basis of the output signal of No. 26 is read, and the reference slip amount ΔV _r is read from the ROM 10b.
Read.

Next, the wheel acceleration dV _W / dt, ΔV (=
Estimated vehicle speed V _SO -wheel speed V _W is calculated (step 2).

Next, it is judged whether or not the output value of the G sensor 28 is smaller than a predetermined value (negative value) (step 3). That is, the G sensor 28 outputs a positive value when detecting the acceleration and outputs a negative value when detecting the deceleration, so that when the vehicle is traveling on a downhill road. Outputs a negative value. However, even when the brake operation is performed on a flat road, the G sensor 28
Since a negative value is output, in order to distinguish it from this, a predetermined value is set to a value having a relatively large absolute value.

In the process of step 3, if it is determined that the output value of the G sensor 28 is smaller than the predetermined value, that is, if the vehicle is traveling on a downhill road, the process proceeds to step 4. In step 4, the reference slip amount ΔV _r read in the process of step 1 is set to the ROM
The correction coefficient k read from 10b is multiplied to correct the reference slip amount ΔV _r . In this case, the correction coefficient k is 1
Since this is a larger positive value, the reference slip amount ΔV _r
When the correction is performed, it becomes difficult to perform the ABS control.

On the other hand, in the processing of step 3 described above,
If it is determined that the output value of the G sensor 28 is larger than the predetermined value, that is, if the vehicle is not traveling on a downhill road, or if the process of step 4 is completed, the process proceeds to step 5.

In step 5, the wheel acceleration d
It is determined whether V _W / dt has become equal to or less than the predetermined value G1, that is, whether the wheels have entered the lock tendency.

In this process, the wheel acceleration dV _W / d
When it is determined that t is not equal to or less than the predetermined value G1, that is, the wheels are not in the lock tendency, the process proceeds to step 11. Immediately after the driver has applied the sudden braking, that is, before the time t1 in FIG. 5, the wheel acceleration dV _W still remains.
Since / dt is not smaller than G1, it is determined that the wheel acceleration dV _W / dt <= G1 is not satisfied, and the routine proceeds to step 11.

In step 11, it is determined whether FABS = 1. Immediately after the driver has applied the sudden braking, FABS = 1 is not yet satisfied and FABS = 0 is satisfied. Therefore, the routine proceeds to step 18 and the brake mode is maintained. That is, immediately after the driver suddenly brakes, the wheels are not in the lock tendency, so the normal brake mode is maintained, and the hydraulic pressure of the rear right wheel cylinder 40 is controlled according to the processing in the normal brake mode described above. Done. By carrying out this processing, the processing routine of this time is ended, the routine returns to step 1, and the wheel speed V _W of the rear right wheel 16, the estimated vehicle body speed V _SO and the reference slip amount ΔV _r are read again, and thereafter. Continue processing.

In the processing of step 5 described above, when it is determined that the wheel acceleration dV _W / dt <= G1, that is, when it is determined that the wheel has entered the lock tendency due to the sudden braking by the driver. , Go to step 6,
It is determined whether FABS = 0. When FABS = 0 is determined in this process, the wheel acceleration is G1.
The slip amount ΔV _sn at the time of is calculated in the process of step 2 of this processing routine ΔV (= estimated vehicle speed V _SO
-Processing for setting the value of the wheel speed V _W (step 7).

On the other hand, when FABS = 1 is determined in step 6, since the process of ΔV _sn = ΔV has already been performed in the previous process routine, the process proceeds to step 8.

In the process of step 8, it is determined that ΔV (= estimated vehicle body speed V _SO -wheel speed V _W )> ΔV _sn + ΔV _r . That is, when the current time is before t2 shown in FIG. 5, since ΔV is smaller than ΔV _sn + ΔV _{r, the routine} proceeds to step 18, and the current brake mode is maintained. In this case, although the wheels are in the tendency to lock, the normal brake mode is maintained because the ABS control is not required. The process of step 8 is performed by the flag FA for performing the ABS control.
When it is determined whether or not BS is set to 1, it is determined in the above-described step 3 that the output value of the G sensor 28 is smaller than a predetermined value, that is, the vehicle is traveling on a downhill road. In step 4, the reference slip amount ΔV
_Since correction is performed to increase the value of _r , A
It becomes difficult to perform BS control.

When the normal brake mode is maintained in the process of step 18 described above, the hydraulic pressure of the rear right wheel cylinder 40 is controlled according to the process in the normal brake mode. As a result, the processing routine of this time is ended, the process returns to step 1, and the subsequent processing is continued.

In the process of step 8, ΔV>
When it is determined that ΔV _sn + ΔV _r , that is, when the time shown in FIG. 5 is between t2 and t3, the process proceeds to step 9, and FABS = 1 is set, and then the process proceeds to step 10. .

In step 10, the brake mode is set to the pressure reducing mode, and the processing for reducing the hydraulic pressure of the rear right wheel cylinder 40 is performed according to the processing in the pressure reducing mode described above. As a result, the processing routine of this time is ended, and the process returns to step 1.

In the process of step 5 described above, it is determined that the wheel acceleration dV _W / dt <= G1, and when FABS = 1 is determined in the process of step 11, the process proceeds to step 12, and the wheel acceleration dV is determined. _W / dt>
Judge G2. Here, even when the hydraulic pressure of the right wheel cylinder 40 is reduced by the process in the pressure reducing mode and the wheel acceleration dV _W / dt is recovered,
When the wheel acceleration dV _W / dt has not recovered to G2, it is judged that the recovery of the wheel speed is insufficient, and the routine proceeds to step 18, where the current brake mode is maintained. That is, in accordance with the above-described processing in the pressure reducing mode, the processing for reducing the hydraulic pressure of the rear right wheel cylinder 40 is continued, the current processing routine is terminated, and the process returns to step 1.

In the processing of step 12 described above, the wheels
Acceleration dV_WIf / dt> G2, the wheels are
It is determined that the speed has recovered, and the process proceeds to step 13.
In this step 13, ΔV <= ΔV_sn+ △ V_r
Judgment is made and it is judged that this condition is not met,
That is, when it is determined that the wheel speed has not recovered sufficiently,
If so, the process proceeds to step 19 to perform the processing in the holding mode.
Do. Here, in FIG. 5, between times t3 and t4.
Then, in step 13, ΔV <= ΔV _sn+ △ V
_rSince it is judged that the conditions of
19 and follow the processing in the hold mode described above.
YA Perform processing to maintain the hydraulic pressure of the right wheel cylinder 40.
U. This completes the current processing routine and
Return to Top 1.

In the process of step 13 described above, ΔV
When it is determined that the condition of <= ΔV _sn + ΔV _r is satisfied, that is, when the wheel speed is sufficiently recovered, the process proceeds to step 14 and the process in the pulse pressure increasing mode is performed. Do.

Next, at step 15, it is judged whether or not the pulse pressure is increased a predetermined number of times in the pulse pressure increasing mode. If it is determined that the pulse pressure increase has not been performed the predetermined number of times, step 18 is performed.
Then, the process in this mode is continued while maintaining the pulse pressure increasing mode.

On the other hand, if it is determined in step 15 that the pulse pressure has been increased a predetermined number of times, step 1
In 6, the FABS = 0 is set, the normal brake mode is returned to (step 17), and the brake control in the normal brake mode is performed.

In the above description, the rear right wheel 16 is described as an example, but the same control is performed for the rear left wheel 18. Further, the front right wheel 12 and the front left wheel 14 are controlled by the processing except steps 3 and 4 of the flowchart shown in FIG.

Therefore, in this ABS, the rear wheel is compared with the front wheel because the reference slip amount ΔV _r , which is a reference for whether or not the ABS control is performed only for the rear wheel, is increased. It becomes difficult to enter ABS control. That is, the degree of reduction of the hydraulic pressure of the wheel cylinder is not suppressed for the front wheels, and the degree of reduction of the hydraulic pressure of the wheel cylinder is suppressed for the rear wheels. Therefore, when sudden braking is applied on a downhill road, ABS control for the rear wheels becomes difficult to perform, and the vehicle tends to lock, which does not give the driver a feeling of idle running, while the front wheels do not have ABS. Since the control is performed, the steering stability can be ensured.

In the above-described embodiment, the degree of reduction of the hydraulic pressure of the wheel cylinder is suppressed only for the rear wheels, but the degree of reduction of the hydraulic pressure of the wheel cylinder is suppressed for the front wheels and the rear wheels. You may In this case, as the correction coefficient k for correcting the value of the reference slip amount ΔV _r , it is necessary to use the correction coefficient k _F for the front wheels and the correction coefficient k _R for the rear wheels (1 <k _F <k _R ). There is. In this way, by using the correction coefficient k _F for the front wheels and the correction coefficient k _R for the rear wheels, the degree of suppression of the pressure reduction of the wheel cylinders provided on the front wheels can be reduced by the pressure reduction of the wheel cylinders provided on the rear wheels. Can be made smaller than the degree of suppression of.

Therefore, since it becomes difficult to carry out the ABS control for the rear wheels, there is a tendency to lock and the driver is less likely to feel idle. Further, although it becomes difficult to perform the ABS control on the front wheels as well, since the correction coefficient k _F for the front wheels is smaller than the correction coefficient k _R for the rear wheels, the driver feels that the vehicle is idling. It is also possible to secure the steering stability while reducing the application of

Further, the value of the front wheel correction coefficient k _F for correcting the value of the reference slip amount ΔV _r may be smaller than 1. In this case, since the front wheels are likely to enter the ABS control, the front wheels are hard to lock, and the steering stability can be reliably ensured.

Further, in the above-described embodiment, the suppression of the degree of pressure reduction of the wheel cylinder is controlled by the reference slip amount ΔV.
This is done by correcting the value of _r (making the ABS start standard stricter), but not limited to this, when the brake mode becomes the pressure reducing mode, the wheel cylinders for the rear wheels are depressurized only by pulse depressurization. , The pressure reduction of the wheel cylinders for the front wheels in the normal pressure reduction mode, that is, the pulse pressure reduction is first performed and then the pressure reduction state is maintained (compared to the pressure reduction gradient of the wheel cylinders for the front wheels, the wheels for the rear wheels). The degree of suppression of decompression of the wheel cylinders provided on the front wheels is also reduced by reducing the decompression gradient of the cylinders. It can be smaller than.

Further, for example, the value of G2 in step 12 of FIG. 4 is reduced, or (ΔV _sn + Δ in step 13)
It is also possible to suppress the degree of pressure reduction of the wheel cylinders by reducing the condition for ending the ABS pressure reduction mode by reducing the value of V _r ).

Further, the degree of decompression of the wheel cylinder may be suppressed by correcting the value of the corresponding wheel speed V _w to the high speed side.

Further, the above ABS start criterion is made strict, the pressure reduction gradient of the wheel cylinder is made gentle, the condition for ending the pressure reduction mode of ABS is loosened, and the value of the wheel speed V _w is corrected to the high speed side. The degree of decompression of the wheel cylinder may be suppressed by any combination of the above.

The correction coefficient k for correcting the reference slip amount ΔV _r may be variable depending on the value of the acceleration / deceleration value G. That is, by increasing the value of the correction coefficient k as the value of the acceleration / deceleration value G increases, it is possible to suppress the feeling of idling depending on the downhill angle.

Further, in the case of a four-wheel steering vehicle or the like, since all the wheels are steered wheels, it is desirable to reduce the degree of pressure reduction of the front wheels. By doing this,
Since the ground contact load of the front wheels is larger than the ground contact load of the rear wheels due to the traveling on the downhill road and the braking operation, it is possible to further secure the lateral force and further improve the steering stability. In addition, when the maximum allowable steering angle is different between the front wheels and the rear wheels, it is desirable to reduce the suppression of the degree of pressure reduction for the wheel having the larger maximum allowable steering angle. By doing so, the lateral force can be secured by the wheel on the side that requires more lateral force, and the steering stability can be further improved.

[0069]

According to the present invention, on a downhill road,
When the BS control is performed, since the degree of reduction of the hydraulic pressure of the wheel cylinders is suppressed only for the rear wheels,
It is possible to suppress the feeling of idling of the driver by the ABS control, and the lateral force of the front wheels (steering wheels) is secured, so that the operation stability can be improved.

Further, the degree of pressure reduction of the hydraulic pressure of the wheel cylinders for the front wheels and the rear wheels is suppressed, and the degree of pressure reduction of the wheel cylinders provided for the front wheels is set to the level of the pressure reduction of the wheel cylinders provided for the rear wheels. If it is smaller than the degree of suppression, the possibility of giving the driver a feeling of idling can be further reduced, and the lateral force for the front wheels (steering wheels) is ensured, so operational stability is ensured. Can be improved.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an ABS according to an embodiment of the present invention.

FIG. 2 is a diagram showing an ABS hydraulic pressure passage and a control system according to an embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of an ABS computer according to an embodiment of the present invention.

FIG. 4 is a flowchart of ABS control according to the embodiment of the present invention.

FIG. 5 is a conceptual diagram of ABS control according to the embodiment of the present invention.

[Explanation of symbols]

10 ... ABS computer, 12 ... front right wheel, 14
Front left wheel, 16 Rear right wheel, 18 Rear left wheel, 2
0 ... front right speed sensor, 22 ... front left speed sensor, 24 ... rear right speed sensor, 26 ... rear left speed sensor, 28 ... G sensor, 30 ... brake pedal, 32 ... master cylinder, 34 ... ABS actuator, 36 ... Front right wheel cylinder, 38 ... Front left wheel cylinder, 40 ... Rear right wheel cylinder, 42 ... Rear left wheel cylinder, 44 ... Front left holding solenoid valve, 46 ... Rear right holding solenoid valve, 48 ... Front left decompression Solenoid valve, 50 ... Rear right pressure reducing solenoid valve, 52, 70
… Reservoir, 60… Solenoid valve for holding left rear, 6
2 ... front right holding solenoid valve, 64 ... rear left pressure reducing solenoid valve, 66 ... front right pressure reducing solenoid valve

Claims (2)

[Claims] 1. An antilock brake system including pressure reducing control means for controlling the pressure reduction of a wheel cylinder, wherein the detecting means detects that the vehicle is traveling on a downhill road, and the detecting means allows the vehicle to drive downhill roads. When it is detected that the vehicle is traveling, a pressure reduction suppressing unit that suppresses the degree of pressure reduction to only the wheel cylinders provided on the non-steered wheels by the pressure reduction control unit, and an antilock brake characterized by the following: system. 2. An antilock brake system comprising pressure reducing control means for controlling pressure reduction of a wheel cylinder, wherein the detecting means detects that the vehicle is traveling on a downhill road, and the detecting means allows the vehicle to drive downhill roads. When it is detected that the vehicle is traveling, a pressure reduction control unit that controls the degree of pressure reduction of the wheel cylinder by the pressure reduction control unit is provided, and the pressure reduction control unit controls the pressure reduction of the wheel cylinder provided on the steered wheels. An anti-lock brake system characterized in that the degree of suppression is made smaller than the degree of suppression of pressure reduction for a wheel cylinder that is provided in a non-steering manner.