JPH05201321A - Hydraulic brake device - Google Patents

Abstract

PURPOSE:To improve the controllability of a hydraulic brake device in a low mupassage. CONSTITUTION:By the execution of the pedal stroke change control program of a controller 50, if the hydraulic pressure of a master cylinder 14 at the instant when both right and left front wheels get in antiskid control condition is below the first set value, it infers that it is running in a low mu passage, and opens a solenoid valve 90 to make a reservoir 80 and a main liquid passage 26 communicate with each other. Thereby, it follows that brake liquid is accommodated in the liquid chamber 84, too, of a reservoir 80 accompanying the step-in of a brake pedal 10, and the quantity of increase of the master cylinder liquid pressure per unit stroke of the brake pedal 10 becomes small. Accordingly, the control of the liquid pressure of a master cylinder becomes easy, and the controllability of the hydraulic brake device becomes high.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic brake device, and more particularly to improving the operability of a brake operating member.

[0002]

2. Description of the Related Art A hydraulic brake system normally connects a master cylinder that generates hydraulic pressure based on the operation of a brake operating member, a wheel cylinder of a brake that suppresses wheel rotation, and the wheel cylinder and the master cylinder. And a main liquid passage that operates. When the driver operates the brake operating member, a hydraulic pressure is generated in the master cylinder, the hydraulic pressure is transmitted to the wheel cylinder through the main hydraulic passage, and the wheel rotation is suppressed.

As one type of the hydraulic brake device, there is one equipped with a friction coefficient estimating device for estimating the friction coefficient of the road surface. For example, the hydraulic brake device described in Japanese Patent Laid-Open No. 3-74248 includes an anti-skid control device that prevents the slip ratio of the wheels from becoming excessively large because the braking force of the vehicle is too large. This anti-skid control device estimates the friction coefficient from the height of the hydraulic pressure of the wheel cylinder (master cylinder) or the magnitude of the vehicle deceleration at the start of the anti-skid control. Further, in the traction control device that prevents the slip ratio from becoming excessive due to the excessive driving force of the vehicle, the friction coefficient of the road surface can be estimated from the magnitude of the vehicle acceleration at the start of the traction control. Furthermore, the friction coefficient of the road surface can be estimated from the magnitude of the side slip of the vehicle body with respect to the steering angle and the vehicle body speed when the vehicle turns.

On the other hand, it is generally preferred that the operating stroke of the brake operating member is short. If the stroke is short, the first fill can be completed by a slight operation of the brake operation member, and the feeling of rigidity can be obtained because the gradient of the increase in the braking force accompanying the increase in the operation amount is large, and a good operation feeling can be obtained. This is because it can be obtained.

[0005]

However, if the operating stroke of the brake operating member is short, the change in the braking force per unit stroke becomes large. Therefore, when braking is performed while traveling on a road surface having a low friction coefficient such as a snow-covered road, a slight change in the amount of operation of the brake operation member by the driver causes a considerable change in the brake operating force, which reduces the deceleration. There was a problem that it was difficult to control accurately or smoothly. Although the above-mentioned publication describes a hydraulic brake device equipped with a road surface friction coefficient estimating device, changing the operation stroke of the brake operating member in accordance with the road surface estimated friction coefficient has not been performed so far. Of.

A device for changing the operation stroke of the brake operating member to a desired length is disclosed in, for example, Japanese Patent Laid-Open No. 63-63.
There is one disclosed in Japanese Patent Publication No. 20256, but in this brake device, a driver operates a select switch to select a desired stroke length,
The stroke is changed, and the operation stroke is not automatically changed according to the friction coefficient of the road surface.

In view of the above circumstances, the present invention ensures a desired deceleration by automatically increasing the operation stroke of the brake operating member while traveling on a road surface having a low friction coefficient such as a snow-covered road. It is an object of the present invention to obtain a hydraulic brake device having high controllability.

[0008]

The gist of the present invention is to provide a hydraulic brake system including the master cylinder, the wheel cylinder, the main fluid passage, and the friction coefficient estimating device, which flows out from the master cylinder by operating a brake operating member. By storing the brake fluid to be stored, the stored fluid pressure increases as the stored fluid amount increases, and by changing the storage state of the brake fluid by the reservoir according to the friction coefficient of the road surface estimated by the friction coefficient estimation means, In the state where the friction coefficient of the road surface is low, the reservoir control means for extending the operation stroke of the brake operation member is provided when the friction coefficient is high.

The reservoir control means is, for example, a valve that can be switched between an open state that allows communication between the reservoir and the main fluid passage and a closed state that blocks the main liquid passage, and an estimated friction coefficient calculated by the friction coefficient estimation device in advance. A valve control means may be included which opens the valve when the value is lower than a set value and connects the reservoir to the main liquid passage when the value is lower than the set value, and closes the valve when the value is higher.

[0010]

In the hydraulic brake device configured as described above, the friction coefficient estimating means estimates the friction coefficient of the road surface on which the vehicle is currently traveling, and based on the estimation result, the reservoir controlling means causes the reservoir to operate. Change the storage condition of the brake fluid. If the reservoir contains a large amount of brake fluid, the portion of the brake fluid discharged from the master cylinder that is supplied to the wheel cylinders in response to the operation of the brake operating member will be reduced, so the unit operation of the brake operating member will be reduced. The amount of increase in the wheel cylinder pressure per stroke becomes small, and as a result, the operation stroke of the brake operation member becomes long.

For example, when the reservoir control means includes the valve and the valve control means, the valve is normally closed, and the brake fluid discharged from the master cylinder by the operation of the brake operating member is the wheel as it is. Supplied to the cylinder. However, if the estimated friction coefficient obtained by the friction coefficient estimating means becomes lower than the set value, the valve control means determines that the road surface on which the vehicle is traveling is a low friction coefficient road, and the valve is opened. Therefore, when the brake operating member is subsequently operated, the brake fluid flowing out of the master cylinder also flows into the reservoir, so that the amount of increase in the master cylinder (wheel cylinder) hydraulic pressure per unit stroke is small, and the operating stroke of the brake operating member is reduced. Will be longer than usual. It should be noted that the reservoir hydraulic pressure is increased as the amount of stored liquid is increased, and the master cylinder hydraulic pressure is also increased accordingly.

[0012]

As described above, in the present invention, if the estimated friction coefficient of the road surface becomes low while the vehicle is traveling, the operation stroke of the brake operating member automatically becomes long, and the desired deceleration is surely obtained. In addition, the deceleration change caused by the fluctuation of the stepped position is reduced, and the controllability is improved. Further, in the present invention, since the driver does not need to change the operation stroke by himself,
The maneuverability of the vehicle is improved.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. In FIG. 1, 10 is a brake pedal as a brake operating member. The brake pedal 10 is connected to a master cylinder 14 via a hydraulic booster 12. The master cylinder 14 has two pressurizing chambers 16, 1.
It is a tandem type equipped with 8 and generates a pressure of a height corresponding to the pedaling force of the brake pedal 10 in each pressurizing chamber 16 and 18, respectively. In the pressurizing chamber 16, the hydraulic circuit of the front wheel system is
Further, the hydraulic circuit of the rear wheel system is connected to the pressurizing chamber 18 independently of each other, but in FIG.
Only the 0 line is shown. A wheel cylinder 22 that operates the brakes of the front wheels 20 is connected to the master cylinder 14 by a main fluid passage 26.

An electromagnetic direction switching valve 28 and an electromagnetic control valve 30 are provided in series in the middle of the main liquid passage 26 so that the front wheels 20 are anti-skid controlled. The electromagnetic directional control valve 28 is connected to the hydraulic booster 1 via the liquid passage 32.
It is connected to the second power pressure chamber 34 and is always in the first state where the wheel cylinder 22 communicates with the pressure chamber 16, but is switched to the second state where it communicates with the power pressure chamber 34 by the excitation of the solenoid 36. .. The solenoid control valve 30 causes the solenoid 38 to be excited and demagnetized to move the wheel cylinder 22.
To a reservoir 40 to reduce the brake fluid pressure, a pressure increasing position to communicate with the power pressure chamber 34 via the electromagnetic directional switching valve 28 to increase the pressure, and a holding position to shut off from both. ..

The switching of the electromagnetic directional control valve 28 and the electromagnetic control valve 30 is performed by the control device 50. Although not shown, the controller 50 includes a CPU, ROM, RA
The main component is a microcomputer having an M and an input / output interface. When the wheel speed of the front wheels 20 detected by the wheel speed sensor 52 is sent to the control device 50, the slip ratio in the control device 50,
The vehicle speed and the like are calculated, and based on the calculation result, the solenoids 36, 38 are energized / excited via the drive circuits 54, 56.
When the demagnetization is performed, the electromagnetic directional control valve 28 and the electromagnetic control valve 3
By switching 0, the slip ratio of the front wheels 20 is kept in an appropriate range. Note that anti-skid control is similarly performed for the other front wheel and the left and right rear wheels.

An accumulator 59 is connected to the power pressure chamber 34 of the hydraulic booster 12 via a control valve 57 and a liquid passage 58. The accumulator 59 has a pump 4 driven by a motor 60 and a reservoir 4
The brake fluid in 0 is supplied. The hydraulic pressure of the accumulator 59 is based on the output signal of the hydraulic pressure sensor 64.
0 command signal causes the motor 60 to pass through the drive circuit 65.
It is designed to be kept within a certain range by being stopped. Reference numeral 66 is a check valve for preventing the backflow of the brake fluid stored in the accumulator 59 to the pump 62, and 68 is a relief valve for preventing the hydraulic pressure of the accumulator 59 from becoming abnormally high. Also, 70
Is a pressure switch for detecting an abnormal pressure accumulation in the accumulator 59, and when an abnormality occurs, the alarm lamp 72 is turned on to notify the driver of the abnormality.

A branch pipe 76 is branched from the main liquid passage 26 between the pressurizing chamber 16 and the electromagnetic directional control valve 28.
The reservoir 80 is connected to this. A fluid chamber 8 for accommodating brake fluid by a piston 82 in the reservoir 80
4 are formed. Inner wall of reservoir 80 and piston 8
A spring 86 is disposed between the piston 82 and the valve 2 to urge the piston 82 in the direction in which the volume of the liquid chamber 84 decreases. Since the urging force of the spring 86 increases as the amount of stored liquid in the liquid chamber 84 increases, the stored liquid pressure increases. When the stored fluid pressure reaches a certain value, the piston 82 moves to the reservoir 80.
It comes into contact with the shoulder surface 88 formed on the inner wall of the valve to prevent further inflow of brake fluid.

In addition, an electromagnetic opening / closing valve 9 is provided in the middle of the branch pipe 76.
0 is provided. The electromagnetic on-off valve 90 is a spherical valve element 92.
As shown in FIG. 1, the valve element 92 is always seated on the valve seat 94 by the urging force of the spring 102 and is in the closed state, and the brake from the main fluid passage 26 to the fluid chamber 84 of the reservoir 80 is provided. The flow of liquid is blocked. Even in this state, the flow of the brake fluid from the fluid chamber 84 to the main fluid passage 26 is not hindered. On the other hand, when the solenoid 98 is excited via the drive circuit 96 by the output signal of the control device 50, the valve opening member 100 moves against the urging force of the spring 104 to separate the valve element 92 from the valve seat 94. Therefore, the main liquid passage 2
6 and the reservoir 80 communicate with each other.

Further, a fluid pressure sensor 108 is provided in the main fluid passage 26 between the pressurizing chamber 16 and the branch pipe 76. The hydraulic pressure sensor 108 is connected to the control device 50, detects the height of the hydraulic pressure of the master cylinder 14, and sends it to the control device 50.

The electromagnetic opening / closing valve 90 is an electromagnetic directional control valve 2
8, the electromagnetic control valve 30, the motor 60 and the like are controlled by the control device 50. Therefore, in the ROM of the control device 50, the pedal stroke change control program represented by the flowchart of FIG. It is stored together with various control programs including an anti-skid control program.

In the hydraulic brake device constructed as described above, when the vehicle travels on a road surface (hereinafter referred to as medium-high μ road) where the estimated friction coefficient is not so low, such as a gravel road or an asphalt road, the pedal is used. The stroke is set to be short, and the increase amount of the master cylinder hydraulic pressure per unit stroke is increased as shown by the broken line in FIG. Therefore, the brake pedal 10 is operated while traveling on the medium and high μ roads.
When is depressed, the first fill is completed promptly, and the driver is provided with an appropriate sense of rigidity as the brake pedal 10 is depressed. On the other hand, when the vehicle has a small estimated friction coefficient such as a snow-covered road (hereinafter, low μ
In the case of traveling on a road (referred to as a road), the increase amount of the master cylinder hydraulic pressure per unit stroke is reduced as shown by the solid line in FIG. Hereinafter, the stroke changing control of the brake pedal 10 will be described with reference to the flowchart of FIG.

While the vehicle is traveling, the program of FIG. 2 is repeatedly executed at regular intervals. First, in step S1 (hereinafter, simply referred to as S1; the same applies to other steps), it is determined whether or not anti-skid control has been started for both left and right front wheels. In the anti-skid control program, anti-skid control is started for each of the left and right front wheels, and it is determined whether or not the anti-skid control flags for them have been turned from OFF to ON. When the anti-skid control is not performed on at least one of the left and right front wheels, the determination result is NO, and the hydraulic pressure of the master cylinder 14 is detected in S2. Liquid pressure sensor 1 in main liquid passage 26
A signal corresponding to the height of the master cylinder hydraulic pressure detected by 08 is taken into the control device 50. Then, in S3, it is determined whether or not the detected hydraulic pressure is equal to or higher than the second set value. The second set value is set to a value slightly higher than the hydraulic pressure at which the anti-skid control is started on the low μ road. If the hydraulic pressure of the master cylinder 14 is smaller than the second set value, the determination result in S3 is NO. And
The execution of one program ends.

On the other hand, if the hydraulic pressure in the master cylinder 14 is greater than or equal to the second set value, the determination result in S3 is YES, and it is determined in S4 whether or not the anti-skid control is being performed. If anti-skid control is being performed on both the left and right front wheels, the result of the determination is YES, and the execution of the program ends. Further, if the anti-skid control is not performed on at least one of the left and right front wheels, the determination result is NO, and the solenoid opening / closing valve 90 is kept closed in S5. Even if the hydraulic pressure of the master cylinder 14 rises above the second set value, the fact that the anti-skid control is not performed on at least one of the front wheels means that the road surface on which the vehicle is currently traveling is not a low μ road. Is.

On the other hand, if the anti-skid control is started for both the left and right front wheels, that is, if the anti-skid control is started for one front wheel while the anti-skid control is started for the other front wheel, S1 Is YES, and the hydraulic pressure of the master cylinder 14 is detected in S6. Then, in S7,
It is determined whether the hydraulic pressure of the master cylinder 14 at the time of starting the anti-skid control is equal to or lower than a predetermined first set value. The first set value is set to a value slightly smaller than the hydraulic pressure at the start of the anti-skid control on the low μ road.
The first set value is set to a value lower than the second set value, and a constant difference is provided between the two set values. If the detected hydraulic pressure of the master cylinder 14 is higher than the first set value, it means that the vehicle is traveling on a medium-high μ road where the estimated friction coefficient is not so low, and the determination result is NO, and the program is executed once. Execution ends.

On the other hand, if the hydraulic pressure in the master cylinder 14 is less than or equal to the first set value, it means that the anti-skid control is started with the master cylinder hydraulic pressure low, and the road surface on which the vehicle is traveling is on a low μ road. That is, the determination result in S7 is YES, and the solenoid excitation command signal is issued in S8. As a result, an exciting current is supplied to the solenoid 98 via the drive circuit 96, the electromagnetic opening / closing valve 90 is opened, and the main liquid passage 26 and the reservoir 80 are brought into communication with each other. When the reservoir 80 is set in the communicating state, the brake fluid flows into the reservoir 80, so that the hydraulic pressure of the master cylinder 14 decreases, but if the anti-skid control is still required, the control is continued. If the master cylinder hydraulic pressure becomes too low, the driver may increase the hydraulic pressure in the wheel cylinders 22 etc. by stepping on the brake pedal. In any case, the electromagnetic on-off valve 90 that has been once opened is kept open.

Therefore, when the brake pedal 10 is next stepped on, the brake fluid flowing out of the pressurizing chamber 16 also flows into the fluid chamber 84 of the reservoir 80 via the electromagnetic opening / closing valve 90, so that the wheel cylinder 22 per unit stroke.
The amount of brake fluid supplied to the cylinder is reduced, that is, the amount of increase in master cylinder hydraulic pressure per unit stroke is smaller than that during traveling on a medium-high μ road. That is, since the pedal stroke becomes long, a slight error in the depression position is absorbed, a desired deceleration can be reliably obtained, the controllability is improved, and proper control on a low μ road becomes possible. .. Frequent antiskid control is also avoided.

Moreover, as the stroke of the brake pedal 10 increases, the amount of liquid stored in the liquid chamber 84 increases, and the hydraulic pressure stored in the reservoir 80 increases, so that the hydraulic pressure of the wheel cylinder 22 reliably increases. Further, when the brake pedal 10 is strongly depressed, the piston 82 comes into contact with the shoulder surface 88 and the inflow of the brake fluid into the fluid chamber 84 is stopped.
After that, all the brake fluid supplied from the master cylinder 14 will flow into the wheel cylinder 22, and the amount of increase in the master cylinder fluid pressure per unit stroke will be large, and a large braking force can be obtained.

If the previous determination result of S1 is YES, the next determination result of S1 will be NO even if the left and right front wheels are under anti-skid control, and the hydraulic pressure of the master cylinder 14 will be detected in S2. Is done. Then, in S3, it is determined whether or not the detected hydraulic pressure is equal to or higher than the second set value. If the determination result in S3 is NO, that is, if the hydraulic pressure in the master cylinder 14 is smaller than the second set value,
Execution of the program ends as it is, but if the hydraulic pressure in the master cylinder 14 is equal to or higher than the second set value, the determination result is Y.
In ES, it is determined in S4 whether or not the anti-skid control is being performed. Then, if the determination result of S4 is YES, the execution of the program ends. Even if the hydraulic pressure in the master cylinder 14 is high, if anti-skid control is performed, it cannot be determined whether the friction coefficient of the road surface is high or low.

On the other hand, if the determination result in S4 is NO, that is, if the anti-skid control is not performed even if the brake pedal 10 is strongly depressed and the hydraulic pressure of the master cylinder 14 becomes high, the friction coefficient of the road surface is high. Therefore, in S5, a command signal to close the electromagnetic on-off valve 90 is output, the solenoid 98 is demagnetized, the valve opening member 100 is retracted to the original position, and the electromagnetic on-off valve 90 is closed. Therefore, the inflow of the brake fluid from the main fluid passage 26 to the reservoir 80 is blocked, and the brake fluid is entirely supplied to the wheel cylinders 22. Therefore, the pedal stroke is shortened again, and the brake pedal 10 is slightly depressed to perform braking. It can be carried out.

In the present embodiment, S1 to S4 and S6, S of the pedal stroke change control program described above are used.
The portion that executes 7 constitutes the friction coefficient estimating means for estimating the friction coefficient of the road surface, and the portion that executes S5 and S8 constitutes the valve control means that controls the electromagnetic opening / closing valve 90. The friction coefficient estimating means and the valve control means constitute reservoir control means.

It is also possible to use the reservoir 120 shown in FIG. 4 in place of the reservoir 80 of this embodiment. The main body 122 of the reservoir 120 is made of a tubular rubber elastic body, and one end is closed with a metal cap 124 to have a bottom, thereby forming a liquid chamber 126 in the main body 122. Further, one end of a communication pipe 128 is inserted into the other end of the main body 122, and the main body 12 is fixed by the fastener 130.
The escape from 2 is prevented. The other end of the communication pipe 128 is connected to the port of the electromagnetic opening / closing valve 90, and the electromagnetic opening / closing valve 90 is opened to allow the brake fluid in the main fluid passage 26 to flow into the fluid chamber 126. Liquid chamber 126
Since the main body 122 expands and the stored liquid pressure increases as the stored liquid amount increases, the hydraulic pressure in the wheel cylinder 22 can be increased as the brake pedal 10 is depressed.

In the above-described embodiment, the friction coefficient of the road surface is estimated when the left and right front wheels are in the anti-skid control state. If the friction coefficient is estimated when the skid control state is entered, the pedal stroke can be changed on the straddle road. Further, the program may be appropriately changed depending on the case such as executing the above control when three of the four wheels are in the anti-skid control state or when all four wheels are in the anti-skid control state. It is possible.

Further, a plurality of sets of solenoid valves and reservoirs may be provided, or a plurality of reservoirs 142 (two in the figure) may be connected to one solenoid valve 140 as shown in FIG. It is possible. In the example shown in FIG. 5, the solenoid valve 140 has a first open state that allows communication with the main liquid passages of both reservoirs 142, a second open state that allows communication of only one reservoir 142, and both reservoirs 142. It is switched to a closed state in which the liquid passage is shut off. Therefore, if the solenoid valve 140 is controlled so that the first set value is set in three stages and the low μ road is in the first open state, the medium μ road is in the second open state, and the high μ road is in the closed state, the braking is performed. The number of reservoirs that allow the inflow of the liquid, that is, the storable amount of the brake liquid in the reservoir changes, and the pedal stroke can be changed in a plurality of stages according to the estimated friction coefficient.

It is also possible to change the pedal stroke steplessly, that is, continuously according to the estimated friction coefficient. One example thereof is shown in FIG. In FIG. 6, a liquid chamber 164 containing a brake fluid is formed in the reservoir 160 by a piston 162, and the liquid chamber 164 is in constant communication with the main liquid passage 166. Piston 1
Reference numeral 62 is connected to one end of a lever 172 via a piston rod 170 by a pin 174. A tension coil spring 180 is arranged between the other end of the lever 172 and a retainer 178 fixed to a vehicle body side member 176. ing.
The intermediate portion of the lever 172 is engaged with a roller 188 rotatably held by the slider 186. Therefore, the lever 172 rotates about the engagement point A between the roller 188 and the lever 172 as a fulcrum, and the piston 162 is biased by the tension coil spring 180 in the direction in which the volume of the liquid chamber 164 decreases. As the amount of the stored liquid in the liquid chamber 164 increases, the biasing force of the spring 180 increases, and the stored liquid pressure increases.

The slider 186 is movably supported in a direction orthogonal to the piston rod 170 by a holding member 192 fixed to the vehicle body side member 176, and is rotatably and axially movable by the holding member 192. It is screwed onto the screw member 194. Screw member 194
Is connected to the output shaft of the pulse motor 196, and the pulse motor 196 is rotated by a predetermined amount based on a command from the control device similar to the above-described embodiment, so that the slider 1
86 is moved along the holding member 192, which changes the position of the engagement point A. As the engagement point A moves away from the pin 174, the urging force of the spring 180 becomes smaller and the piston 162 moves more easily. As the engagement point A approaches the pin 174, it becomes harder to move and the liquid pressure stored in the liquid chamber 164 increases. ..

If the estimated friction coefficient of the running road surface becomes high, the engagement point A between the roller 188 and the connecting member 172 is driven by driving the pulse motor 196 based on the command signal from the controller.
Is brought closer to the pin 174, and the increase amount of the master cylinder pressure per unit stroke of the brake pedal 10 is increased. Further, when the estimated friction coefficient becomes low, the pulse motor 196 is driven in the reverse direction and the engagement point A is moved away from the pin 174, so that the increase amount of the master cylinder hydraulic pressure per unit stroke is reduced. In the present embodiment, by continuously changing the position of the engagement point A, the pedal stroke required to generate the master cylinder hydraulic pressure of the same height is continuously changed according to the estimated friction coefficient of the road surface. It can be done.

In order to estimate the road surface friction coefficient, it is possible to detect the vehicle body deceleration and estimate the road surface friction coefficient based on the magnitude of the vehicle body deceleration and whether or not the anti-skid control is being performed. That is, if the vehicle body deceleration is large but anti-skid control is not performed, the road is high μ, and if the deceleration is small, anti-skid control is performed.
It is presumed to be a road. As an apparatus for estimating the friction coefficient of the road surface from the vehicle deceleration in this way, for example, in addition to the above-mentioned JP-A-3-74248, JP-A-2-310160.
JP-A-3-246156, JP-A-3-24615
The device described in Japanese Patent Publication No. 7 can be applied.

In addition, the pedal stroke is changed by estimating the friction coefficient at the time of traction control and turning of the vehicle.
The present invention can be implemented in various modified and improved modes based on the knowledge of those skilled in the art.

[Brief description of drawings]

FIG. 1 is a system diagram schematically showing a main part of a hydraulic brake device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a pedal stroke switching control program stored in a ROM of the control device for the hydraulic brake device.

FIG. 3 shows changes in pedal stroke and pedaling force of the above device,
6 is a graph showing a comparison between traveling on a medium-high μ road and traveling on a low μ road.

FIG. 4 is a front sectional view showing a reservoir of a hydraulic brake device according to another embodiment of the present invention.

FIG. 5 is a system diagram showing an electromagnetic valve and a reservoir of a hydraulic brake device according to another embodiment of the present invention.

FIG. 6 is a front view (partial cross section) showing the vicinity of a reservoir of a hydraulic brake device according to another embodiment of the present invention.

[Explanation of symbols]

 10 Brake Pedal 14 Master Cylinder 20 Front Wheel 22 Wheel Cylinder 26 Main Fluid Passage 28 Electromagnetic Directional Change Valve 30 Electromagnetic Control Valve 50 Control Device 52 Wheel Speed Sensor 80 Reservoir 90 Electromagnetic On-off Valve 108 Hydraulic Pressure Sensor 120 Reservoir 140 Solenoid Valve 142 Reservoir 160 Reservoir 166 Main liquid passage

Claims (1)

[Claims] 1. A master cylinder that generates hydraulic pressure based on an operation of a brake operating member, a wheel cylinder of a brake that suppresses rotation of wheels, a main fluid passage that connects the wheel cylinder and the master cylinder, and a road surface. And a friction coefficient estimating means for estimating the friction coefficient of the brake fluid, which stores the brake fluid flowing out from the master cylinder by the operation of the brake operating member, and the stored fluid pressure increases as the stored fluid amount increases. By changing the storage state of the brake fluid in the reservoir according to the coefficient of friction of the reservoir and the road surface estimated by the friction coefficient estimating means, the operation stroke of the brake operating member in the state where the friction coefficient of the road surface is low is higher than that in the state where the friction coefficient is high. And a reservoir control means for lengthening the hydraulic brake device.