JP2014058228A - Brake system - Google Patents

Abstract

In a brake system including a braking device having a self-servo mechanism, even when a change occurs in an input for generating a braking force in a state where the braking force is generated, the driver feels uncomfortable with the change in the braking force applied to the driver. To provide a brake system that can reduce
SOLUTION: A master cylinder 20, a disc brake device 24 including a self-servo mechanism, and a hydraulic actuator 22 for supplying and discharging brake fluid sent from the master cylinder 20 to the disc brake device 24 to control a braking force. In the case where the disc brake device 24 generates a braking force, the hydraulic pressure in the wheel cylinder 28 is decreased until the hydraulic pressure on the master cylinder 20 side becomes lower than the hydraulic pressure on the wheel cylinder 28 side by a predetermined value. A hydraulic pressure holding mechanism 102 for holding is included.
[Selection] Figure 1

Description

  The present invention relates to a brake system, and more particularly to an improvement of a brake system including a braking device having a self-servo mechanism.

  Conventionally, a disc brake device and a drum brake device are known as a brake device. In any brake device, the hydraulic pressure corresponding to the hydraulic fluid sent from the master cylinder is supplied to the wheel cylinder of the disc brake device or the drum brake device according to the amount of operation of the brake pedal operated by the driver, and is controlled. It is configured to generate power.

  Such a brake device basically generates a hydraulic pressure by a pedaling force by which a driver depresses a brake pedal. Therefore, a large pedaling force is required to generate a sufficient braking force. Therefore, for the purpose of reducing the operation burden on the driver, the brake structure acts to increase its own braking force so that a sufficiently large braking force can be generated even when the pedaling force is small. There is a brake device provided with a self-servo mechanism (see, for example, Patent Document 1).

JP 2004-225902 A

  In the case of a brake device having a self-servo mechanism, the output braking force increases in a quadratic function with respect to the input hydraulic pressure or pedaling force. That is, the greater the amount of depression of the brake pedal, the more suddenly the generated braking force is generated, and a large braking force can be easily obtained.

  By the way, even when the driver keeps stepping on the brake pedal in order to maintain the state of generation of the braking force, the stepped-on state may slightly change due to dispersion of consciousness or fatigue. When a change occurs in the pedal force in a state where the braking force is generated in this way, particularly when a decrease occurs, the brake force may decrease more than the decrease in the pedal force recognized by the driver. As described above, the self-boost effect by the self-servo mechanism is more effective as the input force increases. In other words, even if the amount of decrease in the input value is the same, the braking force is greatly reduced when the input value is large than when the input amount is small. As a result, the braking force may decrease more than the decrease in the pedaling force perceived by the driver, and the driver may feel uncomfortable.

  The present invention has been made in view of such a situation, and an object of the present invention is to generate a braking force in a state where the braking force is generated in a brake system including a braking device having a self-servo mechanism. An object of the present invention is to provide a brake system that can reduce the uncomfortable feeling of a change in braking force applied to a driver even when a change occurs in input.

  In order to solve the above-described problems, a braking system according to an aspect of the present invention includes a master cylinder that generates hydraulic pressure by sending hydraulic fluid by a driver's operation, and a self-servo that generates braking force by a self-boosting effect. A brake means including a mechanism and a fluid path provided between the brake means and the master cylinder, wherein the brake means generates a braking force, and the hydraulic pressure on the master cylinder side Holding means for holding the operating pressure in the braking means until the hydraulic pressure on the means side exceeds a predetermined value.

  According to this aspect, in a state where the braking force is generated, for example, even if the operation is performed such that the depression force of the brake pedal is reduced and the hydraulic pressure is reduced on the master cylinder side to reduce the braking force, the master cylinder side If the difference between the hydraulic pressure and the hydraulic pressure on the braking means side is within a predetermined value, the holding means holds the hydraulic pressure in the braking means. As a result, the braking force in the control means is maintained even when a slight decrease in the pedaling force of the brake pedal occurs. When the hydraulic pressure on the master cylinder side is lower than the hydraulic pressure on the braking means side by a predetermined value, that is, when the driver consciously reduces the braking force, the holding means To quickly reduce the braking force.

  The holding means may be composed of a solenoid valve. According to this aspect, since the opening and closing of the solenoid valve can be controlled in accordance with the hydraulic pressure changes on the master cylinder side and the braking means side, appropriate control can be performed without reacting more sensitively to the hydraulic pressure change on the master cylinder side. The holding and release of the operating pressure in the braking means can be easily controlled so that power can be generated.

  The liquid path between the braking means and the master cylinder includes a pressure reducing liquid path and a pressure increasing liquid path, the pressure reducing liquid path is provided with the holding means, and the pressure increasing liquid path includes An on-off valve may be provided. According to this aspect, control at the time of pressure reduction of the braking means can be facilitated, and the pressure increasing operation can be performed smoothly.

  The fluid path between the braking means and the master cylinder includes a pressure reducing fluid path and a pressure increasing fluid path, and the fluid pressure on the master cylinder side serves as the holding means in the pressure reducing fluid path. A pressure reducing mechanical valve is provided that opens when the fluid pressure on the means side becomes lower than a predetermined value, and the fluid pressure on the master cylinder side has a fluid pressure on the braking means side in the pressure increasing fluid passage. A pressure-increasing mechanical valve that opens when the pressure is higher than the pressure may be provided. According to this aspect, with a simple configuration, it is possible to maintain the operating pressure in the braking means until the hydraulic pressure on the master cylinder side becomes lower than the hydraulic pressure on the braking means side by a predetermined value.

  ADVANTAGE OF THE INVENTION According to this invention, even when the input for generating braking force changes in the state which is generating braking force, the brake system which can reduce the discomfort of the braking force change given to a driver | operator can be provided.

It is a conceptual diagram of the hydraulic circuit of the brake system which concerns on embodiment. It is explanatory drawing explaining an example of the disc brake apparatus which has a self-servo mechanism employable for the brake system which concerns on embodiment. It is a comparative example of the present embodiment, and is an explanatory diagram for explaining a braking force change when the holding unit of the present embodiment is not included. It is explanatory drawing explaining the arrangement structure of the holding means in the brake system which concerns on embodiment. It is explanatory drawing explaining the effect of the brake system which concerns on embodiment. It is explanatory drawing explaining the other structural example of the holding means of the brake system which concerns on embodiment.

Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described in detail with reference to the drawings.
FIG. 1 is a schematic configuration diagram centering on a hydraulic circuit of a brake system according to an embodiment of the present invention (hereinafter referred to as an embodiment). A brake system 10 shown in FIG. 1 is a system having a piping system called “X piping”. For example, hydraulic fluid (also referred to as brake fluid) is applied to a wheel cylinder for a left front wheel and a wheel cylinder for a right rear wheel. A first piping system 12 to be supplied and a second piping system 14 for supplying brake fluid to the wheel cylinder for the right front wheel and the wheel cylinder for the left rear wheel are provided.

  As shown in FIG. 1, the brake system 10 includes a brake pedal 16, a stroke sensor 18, a master cylinder 20, and a hydraulic actuator 22. In the brake system 10 of FIG. 1, as an example of the arrangement of the brake device, a disc brake device 24FL is provided on the left front wheel of the vehicle, a drum brake device 26RR is provided on the right rear wheel, a disc brake device 24FR is provided on the right front wheel, and a drum is provided on the left rear wheel. The brake device 26RL is connected. The all-wheel disc brake device 24 or the all-wheel drum brake device 26 may be used. The disc brake device 24FL includes a wheel cylinder 28FL, the drum brake device 26RR includes a wheel cylinder 28RR, the disc brake device 24FR includes a wheel cylinder 28FR, and the drum brake device 26RL includes a wheel cylinder 28RL. In the following description, the wheel cylinder 28 is simply referred to unless otherwise distinguished. Each wheel cylinder 28 is connected to the hydraulic actuator 22 via a different brake fluid flow path. The brake system 10 includes a brake ECU 30 that functions as a control unit that controls the operation of a control valve and a motor, which will be described later. The hydraulic actuator 22 shown in FIG. 1 is a hydraulic actuator that realizes an antilock brake system (ABS), and has a simple configuration.

  Brake fluid is supplied to each wheel cylinder 28 from the hydraulic actuator 22, and a brake pad or brake shoe is pressed against a brake disc or brake drum that rotates together with each wheel by the hydraulic pressure of the brake fluid. Thereby, a braking force is applied to each wheel.

  When the brake pedal 16 is depressed by the driver, a pedal stroke that is an operation amount of the brake pedal 16 is input to the stroke sensor 18. The stroke sensor 18 transmits a signal representing the input pedal stroke to the brake ECU 30. Although the stroke sensor 18 is used as a sensor for detecting the operation amount of the brake pedal 16, a pedal force sensor for detecting the pedal force of the brake pedal 16 (the force by which the driver steps on the brake pedal 16) It may be a fluid pressure sensor or the like that detects the fluid pressure.

  The master cylinder 20 sends the brake fluid toward the wheel cylinders 28 by operating the brake pedal 16 by the driver. The master cylinder 20 includes a primary chamber 20a, a secondary chamber 20b, a primary piston 20c, a secondary piston 20d, and a spring 20e.

  The master cylinder 20 is a tandem type master cylinder partitioned into a primary chamber 20a and a secondary chamber 20b by a primary piston 20c and a secondary piston 20d. A push rod extending from the brake pedal 16 is connected to the primary piston 20c. The primary piston 20c presses the push rod so as to return the brake pedal 16 to the initial position side when the brake pedal 16 is not depressed due to the elastic force of the spring 20e. The secondary piston 20d also receives the elastic force of the spring 20e and presses the push rod via the primary piston 20c. When the brake pedal 16 is depressed by the driver, the push rod enters the master cylinder 20 and the primary piston 20c and the secondary piston 20d are pressed. Thereby, a master cylinder pressure is generated in the primary chamber 20a and the secondary chamber 20b.

  The primary chamber 20a and the secondary chamber 20b of the master cylinder 20 are connected to a pipeline A and a pipeline B that extend toward the hydraulic actuator 22, respectively. The master cylinder 20 is connected to a reservoir tank 20f that stores brake fluid. The reservoir tank 20f is connected to each of the primary chamber 20a and the secondary chamber 20b via a passage (not shown) when the brake pedal 16 is in the initial position, and supplies brake fluid into the master cylinder 20 or within the master cylinder 20 Of excess brake fluid.

  As described above, the hydraulic actuator 22 includes the first piping system 12 and the second piping system 14, and includes a pipeline C that connects the primary chamber 20 a of the master cylinder 20 to the wheel cylinder 28 FL and the wheel cylinder 28 RR. Moreover, the pipe line D which connects the secondary chamber 20b, the wheel cylinder 28FR, and the wheel cylinder 28RL is provided. One end of the pipe C is connected to the pipe A, and the other end is provided with an individual pipe H1 provided with an ABS holding valve 32FL, an individual pipe H2 provided with an ABS holding valve 32RR, and a pump 34a. Connected to the individual pipe H3. One end of the pipe D is connected to the pipe B, and the other end is provided with an individual pipe H4 provided with an ABS holding valve 32FR, an individual pipe H5 provided with an ABS holding valve 32RL, and a pump 34b. Connected to the individual pipe H6.

  The pipeline A has a master cut valve 36a in the middle. The master cut valve 36a has a solenoid and a spring that are ON / OFF controlled, and the valve closing state is guaranteed by the electromagnetic force generated by the solenoid upon receipt of a specified control current, so that the solenoid is in a non-energized state. It is a normally open electromagnetic control valve that is opened in some cases. The master cut valve 36a that has been opened can cause the brake fluid to flow between the pipe A and the pipe C in both directions. When a prescribed control current is supplied to the solenoid and the master cut valve 36a is closed, the flow of the brake fluid in the pipeline A and the pipeline C is interrupted. Similarly, the pipeline B has a master cut valve 36b in the middle. The master cut valve 36b that is in an open state can cause the brake fluid to flow in both directions between the pipe B and the pipe D. When a prescribed control current is supplied to the solenoid and the master cut valve 36b is closed, the flow of the brake fluid in the pipe B and the pipe D is interrupted.

  A stroke simulator 40 is connected to the pipe line C via a simulator cut valve 38 on the upstream side of the master cut valve 36a. The simulator cut valve 38 has a solenoid and a spring that are ON / OFF controlled, and is a normally closed electromagnetic control valve that is closed when the solenoid is in a non-energized state. When the simulator cut valve 38 is in the closed state, the flow of brake fluid between the pipe C and the stroke simulator 40 is blocked. When the solenoid is energized and the simulator cut valve 38 is opened, the brake fluid can flow in both directions between the pipe C and the stroke simulator 40. The stroke simulator 40 includes a plurality of pistons and springs, and creates a reaction force corresponding to the depression force of the brake pedal 16 by the driver when the simulator cut valve 38 is opened. As the stroke simulator 40, it is preferable to employ one having a multistage spring characteristic in order to improve the feeling of brake operation by the driver.

  The ABS holding valves 32FL, 32RR, 32FR, and 32RL of the individual pipes H1, H2, H4, and H5 have solenoids and springs that are ON / OFF controlled, respectively, and are opened when the solenoids are in a non-energized state. It is a normally open type electromagnetic control valve. The ABS holding valves 32FL, 32RR, 32FR, and 32RL that have been opened can cause the brake fluid to flow in both directions. That is, the brake fluid supplied from the primary chamber 20a can be made to flow toward the wheel cylinders 28FL and 28RR via the pipeline A. Moreover, the brake fluid supplied from the secondary chamber 20b can be flowed toward the wheel cylinders 28FR and 28RL via the pipe line B. Conversely, the brake fluid can be returned from the wheel cylinders 28FL, 28RR to the primary chamber 20a, and the brake fluid can be returned from the wheel cylinders 28FR, 28RL to the secondary chamber 20b.

  When the solenoid is energized and the ABS holding valves 32FL and 32RR are closed, the flow of brake fluid in the primary chamber 20a and the wheel cylinders 28FL and 28RR is blocked. When the solenoid is energized and the ABS holding valves 32FR and 32RL are closed, the flow of brake fluid in the secondary chamber 20b and the wheel cylinders 28FR and 28RL is blocked. Note that check valves 42FL, 42RR, 42FR, and 42RL are provided in parallel with the ABS holding valves 32FL, 32RR, 32FR, and 32RL, respectively. The check valves 42FL and 42RR allow only the flow of brake fluid from the wheel cylinders 28FL and 28RR toward the pipeline A, and prevent the reverse flow. Therefore, when the brake fluid is returned from the wheel cylinder 28FL side or the wheel cylinder 28RR side toward the primary chamber 20a, the check valve 42FL or the check valve 42RR returns to the return flow via the ABS holding valve 32FL or the ABS holding valve 32RR. A return flow path is formed in the same manner as the road, and the brake fluid can be quickly returned to the primary chamber 20a. The check valves 42FR and 42RL allow only the flow of brake fluid from the wheel cylinders 28FR and 28RL toward the pipe B, and prevent the reverse flow. Accordingly, when the brake fluid is returned from the wheel cylinder 28FR side or the wheel cylinder 28RL side toward the secondary chamber 20b, the check valve 42FR or the check valve 42RL returns to the return flow via the ABS holding valve 32FR or the ABS holding valve 32RL. A return flow path is formed in the same manner as the road, and the brake fluid can be quickly returned to the secondary chamber 20b.

  An ABS pressure reducing valve 44FL is provided in parallel with the wheel cylinder 28FL on the side of the wheel cylinder 28FL from the ABS holding valve 32FL and the check valve 42FL in the individual pipe line H1. Further, an ABS pressure reducing valve 44RR is provided in parallel with the wheel cylinder 28RR on the side of the wheel cylinder 28RR from the ABS holding valve 32RR and the check valve 42RR in the individual pipe line H2. An individual pipe H7 connected to the in-flow path reservoir tank 46a is formed on the downstream side of the ABS pressure reducing valves 44FL and 44RR. Similarly, an ABS pressure reducing valve 44FR is provided in parallel with the wheel cylinder 28FR on the side of the wheel cylinder 28FR from the ABS holding valve 32FR and the check valve 42FR in the individual pipe line H4. An ABS pressure reducing valve 44RL is provided in parallel with the wheel cylinder 28RL on the side of the wheel cylinder 28RL from the ABS holding valve 32RL and the check valve 42RL of the individual pipe line H5. An individual pipe H8 connected to the in-flow reservoir tank 46b is formed on the downstream side of the ABS pressure reducing valves 44FR and 44RL.

  ABS pressure-reducing valves 44FL, 44RR, 44FR, and 44RL each have a solenoid and a spring that are ON / OFF controlled, and are normally closed electromagnetic control valves that are closed when the solenoid is in a non-energized state. . When the ABS pressure reducing valves 44FL and 44RR are closed, the flow of brake fluid toward the reservoir tank 46a in the flow path is blocked. When the solenoid is energized and the ABS pressure reducing valves 44FL and 44RR are opened, the brake fluid is allowed to flow to the in-flow path reservoir tank 46a. When the ABS pressure reducing valves 44FR and 44RL are closed, the flow of brake fluid toward the reservoir tank 46b in the flow path is blocked. When the solenoid is energized and the ABS pressure reducing valves 44FR and 44RL are opened, the brake fluid is allowed to flow to the in-flow path reservoir tank 46b. The in-flow reservoir tanks 46a and 46b are tanks for temporarily storing brake fluid returned from the wheel cylinder 28 during ABS control. The individual conduits H3 and H6 are connected to the in-flow passage reservoir tanks 46a and 46b, respectively. The individual pipe H3 is provided with a pump 34a and check valves 48 before and after the pump 34a. The individual pipe H6 is provided with a pump 34b and check valves 48 before and after the pump 34b. The pumps 34a and 34b operate by driving the motor 50, for example, when the brake pedal 16 is not depressed, the pump fluid is pumped from the in-channel reservoir tanks 46a and 46b. That is, when there is no flow of brake fluid from the primary chamber 20a or the secondary chamber 20b toward the wheel cylinders 28FL, 28RR, 28FR, 28RL, etc., the brake fluid is returned to the primary chamber 20a or the secondary chamber 20b. As a result, the necessary storage amount of the brake fluid in the reservoir tank 20f is maintained. The check valve 48 prevents the brake fluid from flowing backward from the master cylinder 20 toward the reservoir tanks 46a, 46b in the flow path.

The operation of the brake system 10 configured as described above will be described.
During normal braking, that is, when the driver requests braking by depressing the brake pedal 16, the primary chamber 20a and the secondary chamber 20b are compressed by the movement of the primary piston 20c and the secondary piston 20d, and the brake fluid is discharged. The brake fluid passes through the open ABS holding valves 32FL, 32RR, 32FR, and 32RL, and is supplied to each of the wheel cylinders 28FL, 28RR, 28FR, and 28RL. As a result, braking force is generated at each wheel to decelerate or stop the vehicle. On the other hand, when the driver loosens or cancels the depression of the brake pedal 16, the primary chamber 20a and secondary chamber 20b side has a lower pressure than the wheel cylinders 28FL, 28RR, 28FR, 28RL side. As a result, the brake fluid returns from the wheel cylinders 28FL, 28RR, 28FR, 28RL to the primary chamber 20a and the secondary chamber 20b through the ABS holding valves 32FL, 32RR, 32FR, 32RL and the check valves 42FL, 42RR, 42FR, 42RL. The braking force is reduced or disappears.

  Further, when any or all of the wheels are locked during traveling, the brake ECU 30 executes ABS control. In this case, since the brake pedal 16 is depressed by the driver, the brake fluid is supplied from the primary chamber 20a and the secondary chamber 20b to the wheel cylinders 28FL, 28RR, 28FR, 28RL as in the case of normal braking, and braking force is generated. ing. However, the wheel cylinder 28 of the locked wheel needs to reduce the braking force in order to release the lock. Therefore, the brake ECU 30 controls the solenoid of the ABS holding valve 32 and the ABS pressure reducing valve 44 corresponding to the wheel cylinder 28 of the locked wheel to adjust the braking force to cancel the locked state. The ABS control is terminated when, for example, the depression of the brake pedal 16 is released, the vehicle speed becomes a predetermined low speed or less, or the wheel lock state becomes a predetermined state or less.

  FIG. 2 shows a schematic structure of an example of a disc brake device 24 having a self-servo function applied to the brake system 10 of the present embodiment. Since the self-servo structure in the drum brake device 26 is well known, description thereof is omitted. FIG. 2A is a schematic cross-sectional view illustrating a schematic configuration of the disc brake devices 24FL and 24FR. FIG. 2B is a cross-sectional view when viewed from the side. Since the basic structures of the disc brake devices 24FL and 24FR are the same, the disc brake device 24 will be described as a representative.

  The disc brake device 24 includes a disc rotor 52. The disk rotor 52 includes a disk-shaped disk portion 54 and a cylindrical drum portion 56 that is integrally provided perpendicular to the periphery of the disk portion 54 and rotates together with the wheels. In the disc brake device 24, the caliper mounting 58 is disposed so as to face the disc rotor 52. The caliper mounting 58 is formed in a substantially U shape in a side view, and an end portion on the inner side of the vehicle is fixed to the vehicle body by a bolt or the like (not shown). Further, the caliper mounting 58 is disposed so as to straddle the disc rotor 52 and reaches the vehicle outer side of the disc rotor 52. Support bolts 60 and 62 are fixed to the central portion of the caliper mounting 58 so as to extend orthogonally toward the disc rotor 52. Note that the fixing positions of the support bolts 60 and 62 are provided at positions shifted radially outward from the rotation center of the disk rotor 52.

  An inner pad 64 is supported on the support bolt 60 located on the vehicle inner side than the disc rotor 52. The inner pad 64 is constituted by a friction material 66 and a back plate 68 fixed integrally to the friction material 66, and the back plate 68 has an axis line of the support bolt 60 (that is, a direction in which the back plate 68 contacts and separates from the disk rotor 52). It is slidable along and is supported rotatably. The friction material 66 of the inner pad 64 is formed in a substantially L shape in a side view, and corresponds to the first friction part 70 corresponding to the disk part 54 of the disk rotor 52 and the drum part 56 of the disk rotor 52. A second friction part 72 is provided. The first friction part 70 faces the vehicle inner side surface of the disk part 54 of the disk rotor 52 in a parallel state, and the second friction part 72 is formed in a fan shape so as to be inward of the disk rotor 52 in the vehicle. It faces the drum portion 56 on the side.

  On the other hand, an outer pad 74 is supported on the support bolt 62 located on the vehicle outer side than the disc rotor 52. The outer pad 74 basically has the same configuration as the inner pad 64, and a back plate 78 is integrally fixed to the friction material 76, and the back plate 78 is slidable and rotatable along the axis of the support bolt 62. It is supported. Further, the friction material 76 of the outer pad 74 is also provided with a first friction portion 80 and a second friction portion 82, and the first friction portion 80 is parallel to the vehicle outer side surface of the disc portion 54 of the disc rotor 52. The second friction portion 82 is formed in a fan shape and is opposed to the drum portion 56 on the outer side of the disc rotor 52 in the vehicle.

  A caliper 84 is disposed around the inner pad 64 and the outer pad 74. The caliper 84 has a bridge portion 86 so as to cover the disk rotor 52 from above, and covers the inner pad 64 and the outer pad 74 from the outside. A pair of arm portions 88 and 90 extend in parallel to the disk rotor 52 at the lower end portion of the caliper 84, and these arm portions 88 and 90 are rotatably supported by support bolts 60 and 62, respectively. In addition, the inner pad 64 and the outer pad 74 are provided with a convex portion 92, and the inner pad 64 and the outer pad 74 are integrally supported by being fitted into a concave portion inside the caliper 84. Thus, the inner pad 64 and the outer pad 74 are supported so as to rotate around the support bolts 60 and 62 (along the rotational direction of the disk rotor 52) together with the caliper 84.

  In the caliper 84, pistons 94 and 96 constituting the wheel cylinder 28 are inserted and arranged so as to be movable. An opening-side annular surface of the piston 94 is opposed to the back plate 68 of the inner pad 64, whereby the back plate 68 can be pressed. Further, the piston 96 has an opening-side annular surface facing the back plate 78 of the outer pad 74, and can thereby press the back plate 78. A fluid chamber 98 is provided between the pistons 94 and 96 and the caliper 84, and a brake hose is connected, and brake fluid is introduced during braking. When the brake fluid is introduced into the liquid chamber 98, the piston 94 is moved in the direction of the disk rotor 52 to press the back plate 68 of the inner pad 64, and the inner pad 64 is pressed against the disk portion 54 of the disk rotor 52. Generate braking torque. Similarly, the piston 96 is moved in the direction of the disc rotor 52 to press the back plate 68 of the outer pad 74, and the outer pad 74 is pressed against the disc portion 54 of the disc rotor 52 to generate a braking torque.

  A return spring 100 is disposed between the caliper 84 and the caliper mounting 58. The return spring 100 is disposed so as to connect the caliper 84 and the caliper mounting 58 and urges the caliper 84 to return to the initial position (neutral position) around the support bolts 60 and 62. The caliper mounting 58 serves as a stopper that defines the maximum rotation position of the caliper 84, the inner pad 64, and the outer pad 74.

  The operation of the disc brake device 24 configured as described above will be described. During non-braking when the brake operation is not performed, the liquid chamber 98 of the caliper 84 is reduced, and the piston 94 and the piston 96 are separated from the disk portion 54 of the disk rotor 52. In this case, a gap is formed between the first friction portion 70 of the friction material 66 of the inner pad 64 and the first friction portion 80 of the friction material 76 of the outer pad 74 and the disk portion 54 of the disk rotor 52. Further, gaps are also formed between the second friction portion 72 of the friction material 66 of the inner pad 64 and the second friction portion 82 of the friction material 76 of the outer pad 74 and the drum portion 56 of the disc rotor 52. Therefore, the disc rotor 52 is not restrained and no braking force is generated.

  On the other hand, at the time of braking, brake fluid is introduced into the fluid chamber 98 of the caliper 84, and the piston 94 and the piston 96 are moved in the direction of the disk portion 54 of the disk rotor 52. When the piston 94 is moved, the back plate 68 of the inner pad 64 is pressed and moved, and the first friction portion 70 of the friction material 66 of the inner pad 64 is brought into pressure contact with the disk portion 54 of the disk rotor 52 and friction is caused therebetween. A force is generated, and a braking torque acts on the disk rotor 52. Further, when the piston 96 is moved, the back plate 78 of the outer pad 74 is pressed and moved, and the first friction part 80 of the friction material 76 of the outer pad 74 is pressed against the disk part 54 of the disk rotor 52 and friction is caused therebetween. A force is generated, and a braking torque acts on the disk rotor 52.

  In this way, when braking torque is generated in the first friction portion 70 of the inner pad 64 and the first friction portion 80 of the outer pad 74, the inner pad 64 and the outer pad 74 are calipered around the support bolts 60 and 62, respectively, by this braking torque. 84 is rotated along the rotation direction of the disk rotor 52 together with 84. Since the support bolts 60 and 62 that rotatably support the inner pad 64 and the outer pad 74 are at positions shifted from the rotation center of the disk rotor 52, the inner pad 64 and the outer pad 74 follow the rotation direction of the disk rotor 52. As the motor rotates, the second friction portions 72 and 82 gradually come into contact with the drum portion 56 of the disc rotor 52, and braking force is applied to the drum portion 56 and the second friction portion 72 and between the drum portion 56 and the second friction portion 82. Will occur. The braking force by the second friction part 72 and the second friction part 82 is generated as the disk rotor 52 rotates, and has a self-servo effect (self-boosting effect) that gradually increases. Therefore, the braking force by the first friction part 70 and the disk part 54 of the inner pad 64 and the first friction part 80 and the disk part 54 of the outer pad 74 is supplemented, and the braking force is greatly improved.

  At the time of releasing the brake when the brake operation or the like is released, the inner pad 64 and the outer pad 74 pressed by the piston 94 and the piston 96 are released. As a result, the first friction part 70 of the inner pad 64 is separated from the disk part 54 and the first friction part 80 of the outer pad 74 is separated from the disk part 54, so that the braking torque is reduced. Therefore, the caliper 84, that is, the inner pad 64 and the outer pad 74 are rotated in the direction in which the second friction portions 72 and 82 are separated from the drum portion 56, respectively, and returned to the initial position by the urging force of the return spring 100.

  As described above, in the case of the disc brake device 24 having the self-servo effect, the self-servo effect is increased as the hydraulic pressure P is increased as shown in FIG. Therefore, it is advantageous in that a large braking force T can be generated even with a small input (stepping force) (see arrow M in FIG. 3). The same applies to the drum brake device 26. By the way, when the braking force is generated, the hydraulic pressure in the wheel cylinder 28 is in a high pressure state. If the driver keeps the depression amount of the brake pedal 16 constant, the hydraulic pressure in the wheel cylinder 28 basically does not change. That is, no change occurs in the braking force. However, in a situation where the driver requests the generation of braking force, if the pedaling force on the brake pedal 16 is weakened for some reason and the hydraulic pressure on the master cylinder 20 side decreases, the decrease in the hydraulic pressure on the master cylinder 20 side is reduced. Immediately, the hydraulic pressure in the wheel cylinder 28 is reduced. At this time, since the disc brake device 24 and the drum brake device 26 are provided with a self-servo mechanism, as shown in FIG. 3, for example, when the hydraulic pressure P on the master cylinder 20 side decreases as shown by the arrow A, the braking force T Decreases rapidly in a quadratic function as in the case of braking (see arrow N in FIG. 3). In other words, the braking force that actually decreases is greater than the decrease in braking force due to the decrease in the amount of depression recognized by the driver, which may give a sense of discomfort.

  Therefore, the present embodiment has a configuration for eliminating this sense of incongruity. Specifically, as shown in FIG. 4, a hydraulic pressure holding mechanism 102 that functions as a delay mechanism that temporarily delays the reduction of the braking force is provided between the master cylinder 20 and the wheel cylinder 28. In FIG. 1, a hydraulic pressure holding mechanism 102 is arranged between each wheel cylinder 28 and the hydraulic actuator 22. When the wheel cylinder 28 generates a braking force, the hydraulic pressure holding mechanism 102 operates in the disc brake device 24 until the hydraulic pressure on the master cylinder 20 side becomes lower than the hydraulic pressure on the wheel cylinder 28 side by a predetermined value. It is configured to hold pressure. In general, the braking device on the front wheel side has a higher braking capability, so the hydraulic pressure holding mechanism 102 may be provided only on the front wheel.

  FIG. 4 shows an example in which the hydraulic pressure holding mechanism 102 is configured by a mechanical valve. In this configuration, the liquid path between the wheel cylinder 28 and the hydraulic actuator 22 is divided into a pressure reducing liquid path 104a and a pressure increasing liquid path 104b. When the wheel cylinder 28 generates a braking force in the pressure reducing fluid passage 104a, the fluid pressure in the wheel cylinder 28 is maintained until the fluid pressure on the master cylinder 20 side becomes lower than the fluid pressure on the wheel cylinder 28 side by a predetermined value. A pressure reducing mechanical valve 106 that functions as a holding means for holding the pressure is provided. The depressurizing mechanical valve 106 is adjusted in biasing strength so that it opens when the hydraulic pressure on the master cylinder 20 side is lower than the hydraulic pressure on the wheel cylinder 28 side by a predetermined value. Further, the pressure increasing fluid passage 104b is provided with a pressure increasing mechanical valve 108 whose urging strength is adjusted so that it opens when the fluid pressure on the master cylinder 20 side is higher than the fluid pressure on the wheel cylinder 28 side. ing.

  For example, as a result of the driver depressing the brake pedal 16 and the brake fluid from the master cylinder 20 being sent out, the hydraulic pressure rises on the upstream side of the hydraulic actuator 22, so the mechanical valve 108 for increasing pressure is opened. The increase in hydraulic pressure on the master cylinder 20 side is reflected on the wheel cylinder 28 as it is, and a braking force is generated. That is, as indicated by an arrow R in FIG. 5, the braking force increasing operation by the driver is sensitively transmitted to the wheel cylinder 28 side, that is, the disc brake device 24 or the drum brake device 26 side, thereby increasing the braking force. Therefore, the self-servo effect is exhibited smoothly.

  On the other hand, even when the driver depresses the brake pedal 16, that is, when braking force is generated, even if the pedaling force on the brake pedal 16 is weakened for some reason and the hydraulic pressure on the master cylinder 20 side decreases, Since the pressure reducing mechanical valve 106 does not open until the hydraulic pressure on the cylinder 20 side becomes lower than the hydraulic pressure on the wheel cylinder 28 side by a predetermined value, the brake pressure is not discharged from the wheel cylinder 28 and the hydraulic pressure is maintained. Is done. That is, as shown in FIG. 5, the braking force T does not change even if the hydraulic pressure P decreases as shown by the arrow α within a predetermined value. When the hydraulic pressure P becomes lower than a predetermined value, the pressure reducing mechanical valve 106 is opened, the brake fluid is discharged from the wheel cylinder 28, and the hydraulic pressure is reduced. That is, the braking force decreases (see arrow S in FIG. 5).

  As described above, the operation of the hydraulic pressure holding mechanism 102 delays the decrease in the hydraulic pressure on the wheel cylinder 28 side even when the hydraulic pressure on the master cylinder 20 side decreases. As a result, even when a pedal force fluctuation (decrease) unintended by the driver occurs, the braking force is maintained without sensitively reacting to the unintended change. Therefore, a sense of discomfort to the driver can be reduced. In the state where the brake pedal 16 is depressed and braking force is generated, the hydraulic pressures on the master cylinder 20 side and the wheel cylinder 28 side are basically the same. Since the hydraulic pressure holding mechanism 102 holds the hydraulic pressure until the hydraulic pressure on the master cylinder 20 side becomes lower than the hydraulic pressure on the wheel cylinder 28 side by a predetermined value, for example, the brake pedal 16 is fully depressed. In this case, the hydraulic pressure on the wheel cylinder 28 side is maintained until the decrease in the hydraulic pressure on the master cylinder 20 side exceeds a predetermined value with reference to the hydraulic pressure on the wheel cylinder 28 side at that time. Similarly, when the brake pedal 16 is depressed moderately to generate a braking force, the hydraulic pressure on the master cylinder 20 side is reduced based on the hydraulic pressure on the wheel cylinder 28 side at that time. The hydraulic pressure on the wheel cylinder 28 side is maintained until a predetermined value is exceeded. Therefore, the above-mentioned uncomfortable feeling can be suppressed without being influenced by the degree of depression of the brake pedal 16.

  FIG. 6 shows an example in which the hydraulic pressure holding mechanism 102 is configured by an electromagnetic valve 110. In this case, it is possible to switch between increasing and decreasing the pressure of the wheel cylinder 28 by controlling the open / close state of the electromagnetic valve 110. Therefore, the flow path connecting the master cylinder 20 side and the wheel cylinder 28 side can be configured as one without being separated as shown in FIG. The solenoid valve 110 is a normally open solenoid control valve that is opened when the solenoid is in a non-energized state, with the valve closed state guaranteed by the electromagnetic force generated by the solenoid upon receiving a specified control current. Can do.

  When the brake pedal 16 is depressed and a braking force is requested by the driver, the solenoid valve 110 is deenergized and opened, and brake fluid flows from the master cylinder 20 side to the wheel cylinder 28 side and enters the wheel cylinder 28. A desired hydraulic pressure is generated and a braking force is generated. On the other hand, when it can be confirmed that the hydraulic pressure of the wheel cylinder 28 has become constant by a signal from a hydraulic pressure sensor (not shown) or the like, or the depression amount of the brake pedal 16 is stabilized by a signal from the stroke sensor 18 or the like. When it is confirmed that the electromagnetic valve 110 is energized, the valve is closed. This state continues until the hydraulic pressure (Pm) on the master cylinder 20 side becomes lower than the hydraulic pressure (Pc) on the wheel cylinder 28 side by a predetermined value. That is, the driver intentionally releases the brake pedal 16 and continues until the hydraulic pressure drop on the master cylinder 20 side exceeds a predetermined value. During this time, the driver does not depend on the hydraulic pressure drop on the master cylinder 20 side. The braking force is maintained. When the decrease in the hydraulic pressure exceeds a predetermined value, that is, when the driver intentionally releases the brake pedal 16, the solenoid valve 110 is deenergized and the wheel cylinder 28 side and the master cylinder 20 side are not energized. The brake fluid can be circulated, the brake fluid is returned to the master cylinder 20 side to reduce the braking force, and the same operation as the configuration of FIG. 4 is realized.

  In the example of FIG. 4, an electromagnetic valve may be used instead of the pressure reducing mechanical valve 106. In this case, the predetermined value serving as a threshold for maintaining the braking force can be changed as appropriate. For example, the predetermined value for holding the hydraulic pressure can be changed according to the amount of depression of the brake pedal 16 at the time of a braking request. As a result, fine adjustment when reducing the braking force is possible, and the brake feeling can be customized. In the case of FIG. 6 as well, the predetermined value can be finely adjusted in the same manner, and the same effect can be obtained.

  In the case of a configuration using a mechanical valve as in the example of FIG. 4, depending on the setting of the urging strength of the valve (predetermined value for holding the hydraulic pressure), interference with the hydraulic control control when performing ABS control or the like You may need to consider the possibility of doing so. On the other hand, when using an electromagnetic valve, when there is a concern about interference with ABS control or the like, the valve can be fully opened by a control signal, so that interference can be suppressed. Also, in the case of a solenoid valve, when the hydraulic pressure on the wheel cylinder 28 side is to be completely removed, the hydraulic pressure can be quickly lost by the valve opening control. Can be resolved.

  In the above-described embodiment, the disc brake device 24 is described as an example of the braking means, but the same effect can be obtained by the same configuration even when the drum brake device 26 is used as the braking means.

  In the configuration shown in FIG. 1, a hydraulic actuator 22 exists between the master cylinder 20 and the disc brake device 24 and drum brake device 26 functioning as braking means, and between the hydraulic actuator 22 and braking means. The example in which the hydraulic pressure holding mechanism 102 exists is described. In another example, a simple configuration in which the hydraulic pressure holding mechanism 102 exists between the master cylinder 20 and the braking means without the hydraulic actuator 22 may be used. Also in this case, as in the above-described embodiment, in a brake system including a braking device having a self-servo mechanism, an input for generating a braking force in a state where the braking force is generated, that is, an input from the master cylinder 20 side. Even if a change occurs in the vehicle, it is possible to obtain an effect that the uncomfortable feeling of the change in the braking force applied to the driver can be reduced.

  In the configuration of FIG. 2, the example in which the hydraulic pressure holding mechanism 102 is provided between the hydraulic actuator 22 and the braking means has been described. However, the hydraulic actuator 22 has the same function as the function of the hydraulic pressure holding mechanism 102. The hydraulic pressure holding mechanism 102 between the hydraulic actuator 22 and the braking means may be substantially omitted. That is, even when the input for generating the braking force in the state where the braking force is generated, that is, when the input from the master cylinder 20 side is changed, the ABS holding valve 32 and the ABS pressure reducing valve 44 are controlled. An operation similar to that performed when the hydraulic pressure holding mechanism 102 operates may be realized. In this case as well, it is possible to obtain an effect that the uncomfortable feeling of the braking force change given to the driver can be reduced as in the above-described embodiment. Conversely, the same effect can be obtained even if the hydraulic pressure holding mechanism 102 has the function of the hydraulic actuator 22.

  As described above, the present invention has been described with reference to the above-described embodiment. However, the present invention is not limited to the above-described embodiment, and the present invention is not limited to the above-described embodiment and may be appropriately combined or replaced with the configurations of the embodiment and the modified examples. It is included in the present invention. Various modifications such as design changes can be added to the embodiments based on the knowledge of those skilled in the art, and embodiments to which such modifications are added can be included in the scope of the present invention.

  DESCRIPTION OF SYMBOLS 10 brake system, 16 brake pedal, 20 master cylinder, 102 hydraulic pressure retention mechanism, 104a pressure reducing fluid path, 106 pressure reducing mechanical valve, 108 pressure increasing mechanical valve, 110 solenoid valve

Claims (4)

A master cylinder that generates hydraulic pressure by sending hydraulic fluid by the operation of the driver;
Braking means including a self-servo mechanism that generates a braking force by a self-boosting effect;
It is provided on a fluid path between the braking means and the master cylinder, and the braking means generates a braking force, and the hydraulic pressure on the master cylinder side is more predetermined than the hydraulic pressure on the braking means side. Holding means for holding the operating pressure in the braking means until the value exceeds a lower value;
A brake system comprising:   The brake system according to claim 1, wherein the holding unit is configured by an electromagnetic valve.   The liquid path between the braking means and the master cylinder includes a pressure reducing liquid path and a pressure increasing liquid path, the pressure reducing liquid path is provided with the holding means, and the pressure increasing liquid path includes The brake system according to claim 1 or 2, wherein an on-off valve is provided.   The fluid path between the braking means and the master cylinder includes a pressure reducing fluid path and a pressure increasing fluid path, and the fluid pressure on the master cylinder side serves as the holding means in the pressure reducing fluid path. A pressure reducing mechanical valve is provided that opens when the fluid pressure on the means side becomes lower than a predetermined value, and the fluid pressure on the master cylinder side has a fluid pressure on the braking means side in the pressure increasing fluid passage. The brake system according to claim 1, further comprising a mechanical valve for pressure increase that opens when the pressure is higher than the pressure.

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