JP2009184576A - Brake device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a drag of a brake by lowering a brake fluid pressure of a wheel cylinder when a slave cylinder fails during braking. <P>SOLUTION: The brake fluid pressure is generated by advance driving pistons 38A, 38B of the slave cylinders 23 through a motor 52 acting according an operation amount of a brake pedal 12 by a driver. The wheel cylinders 16, 17 ; 20, 21 are actuated by the brake fluid pressure. The brake device is provided with brake fluid releasing valves 31A, 31B for reducing the brake fluid pressure supplied to the wheel cylinders 16, 17 ; 20, 21. When the pistons 38A, 38B of the slave cylinder 23 do not returned from the advanced position, the brake fluid releasing valves 31A, 31B are opened to reduce the brake fluid pressure of the wheel cylinders 16, 17 ; 20, 21, and therefore the wheel cylinders 16, 17 ; 20, 21 are kept in an operating state, the problem where the drag of the brake occurs is resolved. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  According to the present invention, a brake operation element operated by a driver and a piston slidably fitted to a cylinder body are driven forward by an electric motor to generate a brake fluid pressure corresponding to the operation amount of the brake operation element. The present invention relates to a braking device including a slave cylinder and a wheel cylinder that operates by the brake hydraulic pressure to brake a wheel.

A so-called BBW (brake-by-wire) brake device that converts a driver's braking operation into an electrical signal to operate a slave cylinder and operates a wheel cylinder with the brake fluid pressure generated by the slave cylinder is disclosed in the following patent. It is known from document 1.
JP 2005-343366 A

  By the way, in such a BBW type brake device, even if the slave cylinder breaks down while the slave cylinder generates brake fluid pressure and operates the wheel cylinder, the slave cylinder However, since the brake fluid pressure is maintained, the wheel cylinder continues to generate a braking force, causing a brake drag.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce the brake fluid pressure of the wheel cylinder and prevent the brake from being dragged when a slave cylinder fails during braking.

  In order to achieve the above object, according to the first aspect of the present invention, the brake operating element operated by the driver and the piston slidably fitted to the cylinder body are driven forward by the electric motor. Brake supplied to the wheel cylinder in a brake device comprising: a slave cylinder that generates a brake fluid pressure according to an operation amount of the brake operator; and a wheel cylinder that operates by the brake fluid pressure to brake a wheel. A brake device is provided, comprising brake hydraulic pressure reducing means for reducing the hydraulic pressure, wherein the brake hydraulic pressure reducing means is activated when the piston of the slave cylinder does not return from the forward position. .

  According to the second aspect of the present invention, in addition to the configuration of the first aspect, when the brake operator is returned to the non-operation position, the electric motor of the slave cylinder moves in the direction of decreasing the brake hydraulic pressure. If it does not operate, a brake device is proposed which cuts off the power supply to the electric motor.

  The brake pedal 12 of the embodiment corresponds to the brake operator of the present invention, and the brake fluid pressure release valves 31A and 31B, the reservoir 32, the reservoir 43 and the out valve 44 of the embodiment are reduced in brake fluid pressure of the present invention. Corresponds to the means.

  According to the configuration of the first aspect, the piston of the slave cylinder is driven forward by the electric motor that operates according to the operation amount of the brake operator by the driver to generate the brake fluid pressure, and the wheel cylinder is driven by the brake fluid pressure. In the operation, a brake hydraulic pressure reducing means for reducing the brake hydraulic pressure supplied to the wheel cylinder is provided, and when the piston of the slave cylinder stops returning from the forward position, the brake hydraulic pressure reducing means is operated to Since the brake fluid pressure is reduced, it is possible to eliminate the situation in which the wheel cylinder remains in the operating state and the brake drag occurs.

  According to the second aspect of the present invention, if the electric motor of the slave cylinder does not operate in the direction of reducing the brake fluid pressure when the brake operation element is returned to the non-operation position, the electric current to the electric motor is cut off. It is possible to prevent the electric motor from being burned out and the battery being consumed.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIGS. 1 to 3 show a first embodiment of the present invention. FIG. 1 is a hydraulic circuit diagram of a vehicle brake device in a normal state, and FIG. 2 is a piston corresponding to FIG. FIG. 3 is a flow chart for explaining the action at the time of failure.

  As shown in FIG. 1, the tandem master cylinder 11 includes two first hydraulic pressure chambers 13A and 13B that output brake hydraulic pressure in accordance with the pedaling force of the driver stepping on the brake pedal 12. The first hydraulic chamber 13A is connected to the wheel cylinders 16 and 17 of the disc brake devices 14 and 15 of the left front wheel and the right rear wheel, for example, via the fluid paths Pa, Pb, Pc, Pd, and Pe. The one hydraulic chamber 13B is connected to the wheel cylinders 20 and 21 of the disc brake devices 18 and 19 of the right front wheel and the left rear wheel, for example, via the fluid paths Qa, Qb, Qc, Qd, and Qe.

  A shutoff valve 22A, which is a normally open solenoid valve, is disposed between the fluid paths Pa, Pb, and a shutoff valve 22B, which is a normally open solenoid valve, is disposed between the fluid paths Qa, Qb, and the fluid paths Pb, Qb and the fluid path. A slave cylinder 23 is arranged between Pc and Qc.

  A stroke simulator 26 is connected to the liquid paths Ra and Rb branched from the liquid path Qa via a reaction force permission valve 25 which is a normally closed solenoid valve. The stroke simulator 26 is a cylinder 27 in which a piston 29 urged by a spring 28 is slidably fitted, and a liquid chamber 30 formed on the side opposite to the spring 28 of the piston 29 communicates with a liquid path Rb. .

  The actuator 51 of the slave cylinder 23 includes a drive bevel gear 53 provided on the rotating shaft of the electric motor 52, a driven bevel gear 54 that meshes with the drive bevel gear 53, and a ball screw mechanism 55 that is operated by the driven bevel gear 54. A sleeve 58 is rotatably supported on the actuator housing 56 via a pair of ball bearings 57, 57. An output shaft 59 is coaxially disposed on the inner periphery of the sleeve 58, and a driven bevel gear 54 is provided on the outer periphery thereof. Fixed.

  A pair of pistons 38A and 38B urged in a backward direction by a pair of return springs 37A and 37B are slidably disposed in the cylinder main body 36 of the slave cylinder 23, and a pair of pistons 38A and 38B are paired on the front surface of the pistons 38A and 38B. The second hydraulic chambers 39A and 39B are partitioned. The front end of the output shaft 59 contacts the rear end of the rear piston 38A. One second hydraulic chamber 39A communicates with fluid paths Pb and Pc via ports 40A and 41A, and the other second hydraulic chamber 39B communicates with fluid paths Qb and Qc via ports 40B and 41B.

  Brake fluid pressure release valves 31A and 31B, which are normally closed solenoid valves, are respectively disposed in the fluid passage Pf branched from the fluid passage Pc and the fluid passage Qf branched from the fluid passage Qc. The valves 31A and 31B are connected to a common reservoir 32. The reservoir 32 is a cylinder 33 in which a piston 35 biased by a spring 34 is slidably fitted, and a fluid chamber 36 formed on the side opposite to the spring 34 of the piston 35 is provided with a brake fluid pressure release valve 31A, It communicates with 31B.

  Next, the operation of the embodiment of the present invention having the above configuration will be described.

  When the system functions normally, as shown in FIG. 1, the shut-off valves 22A and 22B made of normally open solenoid valves are excited and closed, and the reaction force permission valve 25 made of normally closed solenoid valves is excited. As a result, the brake fluid pressure release valves 31A and 31B made up of normally-closed solenoid valves are demagnetized and closed. In this state, when the hydraulic pressure sensor Sa provided in the fluid path Qa detects that the driver depresses the brake pedal 12, the actuator 51 of the slave cylinder 23 is activated. That is, when the electric motor 52 is driven in one direction, the output shaft 59 advances through the drive bevel gear 53, the driven bevel gear 54, and the ball screw mechanism 55, so that the pair of pistons 38A and 38B pressed against the output shaft 59 Advance. Immediately after the pistons 38A and 38B start moving forward, the ports 40A and 40B connected to the fluid paths Pb and Qb are closed, so that the brake fluid pressure is generated in the second fluid pressure chambers 39A and 39B. This brake fluid pressure is blocked by the brake fluid pressure release valves 31A and 31B in the closed state and transmitted to the wheel cylinders 16, 17; 20, 21 of the disc brake devices 14, 15; 18, 19 to brake each wheel. To do.

  At this time, the brake fluid pressure generated in the other first fluid pressure chamber 13B of the master cylinder 11 is transmitted to the fluid chamber 30 of the stroke simulator 26 through the opened reaction force permission valve 25, and the piston 29 is transmitted to the spring 28. By moving the brake pedal against this, it is possible to allow the stroke of the brake pedal 12 and generate a pseudo pedal reaction force to eliminate the driver's uncomfortable feeling.

  The brake fluid pressure detected by the slave cylinder 23 detected by the fluid pressure sensor Sb provided in the fluid passage Qc becomes a magnitude corresponding to the brake fluid pressure detected by the master cylinder 11 detected by the fluid pressure sensor Sa provided in the fluid passage Qa. As described above, by controlling the operation of the actuator 51 of the slave cylinder 23, it is possible to cause the disc brake devices 14, 15; 18, 19 to generate a braking force according to the pedaling force input to the brake pedal 12 by the driver.

  When the slave cylinder 23 becomes inoperable due to a power failure or the like, braking is performed by the brake fluid pressure generated by the master cylinder 11 instead of the brake fluid pressure generated by the slave cylinder 23.

  When the power supply fails, the shut-off valves 22A and 22B composed of normally open solenoid valves are automatically opened, and the reaction force permitting valve 25 composed of normally closed solenoid valves is automatically closed and normally closed. The brake hydraulic pressure release valves 31A and 31B made up of type electromagnetic valves are automatically closed. In this state, the brake fluid pressure generated in the first fluid pressure chambers 13A and 13B of the master cylinder 11 is cut off without being absorbed by the stroke simulator 26 and leaking from the brake fluid pressure release valves 31A and 31B. Passing the valves 22A and 22B and the second hydraulic chambers 39A and 39B of the slave cylinder 23, the wheel cylinders 16, 17; 20, 21 of the disc brake devices 14, 15; A braking force can be generated.

  Further, when the pistons 38A and 38B are fixed at the forward position in the normal state described with reference to FIG. 1, that is, when the electric motor 52 of the slave cylinder 23 fails and is fixed unrotatably during braking, the drive bevel gear 53, When the driven bevel gear 54, the ball screw mechanism 55, etc. are fixed, or when the pistons 38A, 38B are fixed to the cylinder body 36, the pistons 38A, 38B do not move backward even if the driver returns the brake pedal 12, so that the wheel cylinder Since the brake fluid pressures 16, 17, 20 and 21 are not released and the brake is dragged, there is a problem that trouble occurs when towing to a repair shop.

  In such a case, as shown in FIG. 2, the brake fluid pressure release valves 31A and 31B are excited and opened to release the brake fluid pressure of the wheel cylinders 16, 17; Therefore, dragging of the brake can be prevented.

  The above operation will be further described based on the flowchart of FIG.

  First, when the brake pedal 12 depressed by the driver in step S1 is returned, it is determined whether or not the electric motor 52 is reversely rotated in the direction in which the pistons 38A and 38B of the slave cylinder 23 are moved backward. On the other hand, if the hydraulic pressure sensor Sb detects a decrease in the brake hydraulic pressure of the wheel cylinders 16, 17; 20, 21 in step S 3, it is determined that the pistons 38 A, 38 B have moved back normally, and nothing is done. If the pressure sensor Sb does not detect the pressure reduction of the brake fluid pressure of the wheel cylinders 16, 17, 20 and 21, it is determined that the pistons 38A and 38B are fixed and do not reverse normally, and the brake fluid pressure release valve 31A is determined in step S4. , 31B is excited to open the brake fluid pressure of the wheel cylinders 16, 17; 20, 21 to the reservoir 32.

  If the electric motor 52 does not reverse in step S2, it is determined that the electric motor 52 has failed, and the power supply is cut off, thereby preventing the electric motor 52 from being burned out and the battery being consumed. If the reason why the electric motor 52 does not reverse is the failure of the control circuit, the electric motor 52 can freely rotate by cutting off the energization, and the electric motor 52 is caused by the reaction force of the brake fluid pressure. To rotate the pistons 38A and 38B backward.

  FIGS. 4 and 5 show a second embodiment of the present invention. FIG. 4 is a hydraulic circuit diagram of the vehicle brake device in a normal state, and FIG. 5 is a piston corresponding to FIG. It is a hydraulic-pressure circuit diagram when doing.

  In the second embodiment, an ABS (anti-lock brake system) device 24 for suppressing wheel lock is added to the brake device of the first embodiment, and the ABS device 24 includes right and left wheels. VSA (Vehicle Stability Assist) function is also provided to improve the steering stability of the vehicle by generating a difference in the braking force.

  Note that the second embodiment does not include the brake fluid pressure release valves 31A and 31B of the first embodiment, and the functions of the out valves 44 are described later.

  The structure of the ABS device 24 disposed between the fluid paths Pc, Qc and the fluid paths Pd, Pe; Qd, Qe is a well-known structure, and the system of the disc brake devices 14, 15 for the left front wheel and the right rear wheel, The same structure is provided for the disc brake devices 18 and 19 for the right front wheel and the left rear wheel. As a representative example, the system of the disc brake devices 14 and 15 for the left front wheel and the right rear wheel will be described. Between the liquid passage Pc and the liquid passages Pd and Pe, in-valves 42 and 42 made up of a pair of normally open solenoid valves are arranged. In addition, out valves 44 and 44, which are normally closed electromagnetic valves, are disposed between the fluid paths Pd and Pe on the downstream side of the in valves 42 and 42 and the reservoir 43. A hydraulic pump 47 sandwiched between a pair of check valves 45 and 46 is disposed between the reservoir 43 and the fluid path Pc. The hydraulic pump 47 is driven by an electric motor 48.

  The ABS device 24 further includes the following configuration in order to exhibit the VSA function. That is, from a normally open solenoid valve capable of arbitrarily controlling the opening degree between the front position where the liquid path Pc branches to the liquid paths Pd and Pe and the front position where the liquid path Qc branches to the liquid paths Qd and Qe. Regulator valves 61 and 61 are arranged. Further, check valves 62 and 62 are arranged in series with the check valves 45 and 45, branch from between the check valves 45 and 45 and the check valves 62 and 62, and upstream of the regulator valves 61 and 61. Suction valves 63 and 63, each of which is a normally closed solenoid valve, are disposed in the liquid paths Pf and Qf connected to the liquid paths Pc and Qc, respectively.

  The normal operation of the brake device of the second embodiment is that the regulator valves 61, 61 and the in-valve 42 are in an open state, and the slave cylinder 23 and the wheel cylinders 16, 17; Therefore, the operation is the same as that of the first embodiment described above.

  Next, the operation at the time of ABS control will be described. When it is detected that the slip ratio of any of the wheels has increased due to the output of the wheel speed sensor Sc ... during braking under normal conditions, the slave cylinder 23 is maintained in an operating state. The ABS device 24 is activated to prevent the wheels from locking.

  That is, when a predetermined wheel tends to be locked, the in-valve 42 connected to the wheel cylinder of the disc brake device of the wheel is closed and the out-valve 44 is opened with the transmission of the brake fluid pressure from the slave cylinder 23 blocked. The wheel does not lock by performing a pressure reducing action to release the brake fluid pressure of the wheel cylinder to the reservoir 43 and a holding action to close the out valve 44 and hold the brake fluid pressure of the wheel cylinder. So as to reduce the braking force.

  As a result, when the wheel speed recovers and the slip ratio decreases, the braking force of the wheel is increased by opening the in-valve 42 and increasing the brake fluid pressure of the wheel cylinder. When the wheel becomes locked again by this pressure increasing action, the pressure reduction, holding, and pressure increasing are executed again, and the maximum braking force can be generated while suppressing the wheel lock by repeating the operation. In the meantime, the brake fluid that has flowed into the reservoir 43 is returned to the upstream fluid paths Pc and Qc by the hydraulic pump 47.

  Next, the operation at the time of VSA control will be described. If the vehicle is oversteering when turning the vehicle, the wheel cylinder of the turning outer wheel is operated to generate a yaw moment that suppresses oversteering. If the vehicle is understeering when turning, the inner wheel of the turning In order to generate a yaw moment that suppresses understeer by operating the wheel cylinder, the braking force of the wheel cylinders of the left and right wheels can be individually controlled.

  That is, when the hydraulic pumps 47 and 47 are operated with the suction valves 63 and 63 opened in FIG. 4, the brake fluid is sucked from the reservoir of the master cylinder 11 through the suction valves 63 and 63. Brake fluid pressure is generated upstream of 42. The brake fluid pressure is regulated to a predetermined level by exciting the regulator valves 61 and 61 and controlling the brake fluid pressure to a predetermined opening degree.

  In this state, the in-valve 42 corresponding to the wheel that does not need to be braked is closed so that the brake fluid pressure is not transmitted to the wheel cylinder, while the in-valve 42 that corresponds to the wheel that needs to be braked is opened. By transmitting the brake fluid pressure to the cylinder, the wheel cylinder can be operated to generate a braking force. Control of increasing / decreasing / holding the brake fluid pressure transmitted to the wheel cylinder is performed by opening and closing the in-valve 42 and the out-valve 44 as in the case of ABS control.

  In this way, by braking only one of the left and right wheels by VSA control, it is possible to generate a yaw moment in an arbitrary direction and improve the steering stability of the vehicle.

  The action when the power supply fails in the second embodiment is the same as that of the first embodiment, and the brake fluid pressure generated by the master cylinder 11 instead of the brake fluid pressure generated by the slave cylinder 23. Braking is performed.

  As in the first embodiment, when a failure occurs in which the pistons 38A and 38B are stuck in the forward position during the operation of the slave cylinder 23 in the normal state shown in FIG. 20 and 21 brake fluid pressures need to be reduced, but in the second embodiment, the brake fluid pressure release valves 31A and 31B of the first embodiment are not provided. Valves 44 ... function as brake fluid pressure release valves 31A, 31B.

  That is, when a failure occurs during the operation of the slave cylinder 23, the out valve 44 in FIG. 5 is opened and the wheel cylinders 16, 17; 20, 21 are communicated with the reservoirs 43, 43. 17; 20, 21 brake fluid pressure can be released to prevent brake dragging. At this time, if at least one of the two out valves 44, 44 of each system is opened, the brake fluid pressure of the wheel cylinders 16, 17; 20, 21 can be released.

  According to the second embodiment, since the out valve 44 of the ABS device 24 is used as the brake hydraulic pressure release valves 31A and 31B, the special brake hydraulic pressure release valves 31A and 31B become unnecessary, and the number of parts is reduced. It can contribute to reduction.

  The embodiments of the present invention have been described above, but various design changes can be made without departing from the scope of the present invention.

  For example, the brake operator is not limited to the brake pedal 12 but may be a brake lever or a signal output means for outputting a brake operation amount signal.

  In the embodiment, the slave cylinder 23 is operated according to the driver's operation of the brake pedal 12, but the slave cylinder 23 may be operated when automatic braking is required.

Hydraulic circuit diagram of normal state of vehicle brake device according to first embodiment Hydraulic circuit diagram when piston corresponding to FIG. Flow chart explaining the action at the time of failure Hydraulic circuit diagram at normal time of vehicle brake device according to second embodiment Hydraulic circuit diagram when piston corresponding to FIG.

Explanation of symbols

12 Brake pedal (brake operator)
16 Wheel cylinder 17 Wheel cylinder 20 Wheel cylinder 21 Wheel cylinder 23 Slave cylinder 31A Brake hydraulic pressure release valve (brake hydraulic pressure reducing means)
31B Brake fluid pressure release valve (brake fluid pressure reducing means)
32 Reservoir (brake fluid pressure reducing means)
36 Cylinder body 38A Piston 38B Piston 43 Reservoir (brake hydraulic pressure reducing means)
44 Out valve (Brake fluid pressure reducing means)
52 Electric motor

Claims (2)

A brake operator (12) operated by the driver;
A slave that generates a brake fluid pressure corresponding to the amount of operation of the brake operator (12) by driving the pistons (38A, 38B) slidably fitted into the cylinder body (36) forward by an electric motor (52). A cylinder (23);
A wheel cylinder (16, 17; 20, 21) that operates by the brake fluid pressure to brake the wheel;
In a brake device comprising:
Brake fluid pressure reducing means (31A, 31B, 32; 43, 44) for reducing the brake fluid pressure supplied to the wheel cylinders (16, 17; 20, 21);
When the piston (38A, 38B) of the slave cylinder (23) does not return from the forward position, the brake fluid pressure reducing means (31A, 31B, 32; 43, 44) is operated. Brake device.   If the electric motor (52) of the slave cylinder (23) does not operate in the pressure reducing direction of the brake hydraulic pressure when the brake operator (12) is returned to the non-operating position, the electric motor (52) The brake device according to claim 1, wherein energization is cut off.

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