JP4837411B2 - BBW brake system - Google Patents

Description

  The present invention brakes a wheel with an actuator that operates with an electric signal according to a driver's brake operation in a normal state, and brakes the wheel with a brake hydraulic pressure generated by a master cylinder that operates with a driver's brake operation in an abnormal state. The present invention relates to a brake device.

In the following Patent Document 1, the communication between the master cylinder 14 that generates brake fluid pressure and the wheel cylinders 22FL, 22FR, 22RL, and 22RR that brake the wheel when the driver depresses the brake pedal 12 in a normal state is described as an electromagnetic on-off valve 24A. , 24B, the brake fluid pressure generated by the oil pump 36 is supplied to the wheel cylinders 22FL, 22FR, 22RL, 22RR via the electromagnetic on-off valves 50FL, 50FR, 50RL, 50RR; 60FL, 60FR, 60RL, 60RR. Braking is performed, and the electromagnetic on-off valves 24A and 24B are opened in the event of an abnormality, and the brake fluid pressure generated by the master cylinder 14 is supplied directly to the wheel cylinders 22FL, 22FR, 22RL, and 22RR to perform braking. (Brake-by-wire) type brake device opened It is.
JP-A-2005-219661

  By the way, the conventional BBW brake device has a large deceleration on the vehicle because the braking force of the front wheels and the braking force of the rear wheels when the brake fluid pressure is supplied from the master cylinder 14 at the time of abnormality are set to be the same. If this occurs, the rear wheel may lock before the front wheel and disturb the vehicle behavior. To prevent this, if the front wheel cylinder is made larger than the rear wheel cylinder and the front wheel braking force is increased, the braking force of the rear wheel is reduced in the region where the deceleration of the vehicle is relatively small during normal operation. In order to obtain an ideal braking force distribution characteristic that is greater than the braking force, the brake fluid pressure generated by the oil pump 36 is greatly reduced by the electromagnetic on-off valves 50FL and 50FR; There is a problem that the efficiency of the system is significantly reduced.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a BBW brake device capable of obtaining an appropriate braking force distribution between the front and rear wheels during normal and abnormal conditions.

In order to achieve the above object, according to the first aspect of the present invention, a front wheel actuator that generates a brake fluid pressure for a front wheel, a rear wheel actuator that generates a brake fluid pressure for a rear wheel, and a driver Control means for controlling the operation of the two actuators according to the operation of the brake operator by means of, a master cylinder for generating brake fluid pressure according to the operation of the brake operator by the driver, and a wheel cylinder for the front wheels for braking the front wheels And a rear wheel wheel cylinder that brakes the rear wheel, and a solenoid valve that shuts off communication between the master cylinder and the wheel cylinders when both the actuators are normal and communicates when the actuators are abnormal, and generates the master cylinder. When the two cylinders are operated with the brake fluid pressure, the vehicle deceleration is 0.8G. Kino as braking force distribution of front and rear wheels becomes an ideal distribution, the diameter of the rear wheel brake disk is made smaller than the diameter of the front wheel brake discs, the ratio of the braking force generated by the both wheel cylinders A BBW brake device is proposed, which is characterized in that

  According to the second aspect of the present invention, in addition to the configuration of the first aspect, the thickness of the brake disc for the rear wheel is made larger than the thickness of the brake disc for the front wheel. Is proposed.

  The brake pedal 11 of the embodiment corresponds to the brake operator of the present invention, the pedal force cutoff valve 18 of the embodiment corresponds to the electromagnetic valve of the present invention, and the motor cylinders 19F and 19R of the embodiment are of the present invention. The electronic control unit U of the embodiment corresponds to the control means of the present invention.

According to the configuration of the first aspect, when the front and rear wheel actuators are normal, the brake fluid generated by the front and rear wheel actuators with the solenoid valve closed and the communication between the master cylinder and the front and rear wheel wheel cylinders blocked. By operating the front and rear wheel cylinders independently with pressure, the front and rear wheels can be braked with an ideal braking force distribution. On the other hand, when the front and rear wheel actuators are abnormal, the front and rear wheel cylinders are operated with the same brake fluid pressure generated by the master cylinder with the solenoid valve opened and the master cylinder and front and rear wheel cylinders communicating with each other. In that case, the diameter of the brake disc on the rear wheel is made smaller than the diameter of the brake disc on the front wheel so that the braking force distribution on the front and rear wheels becomes an ideal distribution when the vehicle deceleration is 0.8G. By setting the ratio of the braking force generated by the both wheel cylinders, it is possible to prevent the rear wheels from locking first and maintain stable vehicle behavior even at a high deceleration of 0.8G. .

  According to the second aspect of the present invention, since the thickness of the brake disc on the rear wheel is made larger than the thickness of the brake disc on the front wheel, the brake on the rear wheel is larger than that on the front wheel so that an ideal braking force distribution can be obtained by the BBW during normal operation. Even if the hydraulic pressure is generated and the amount of heat generated by the brake disc on the rear wheel is increased, the heat release from the brake disc on the rear wheel can be effectively performed to suppress the occurrence of the fade phenomenon.

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

  1 to 5 show an embodiment of the present invention. FIG. 1 is a hydraulic system diagram at the time of normal operation of the BBW brake device. FIG. 2 is a hydraulic system diagram at the time of abnormality corresponding to FIG. 3 is a block diagram of the control system, FIG. 4 is a diagram showing the structure of the disc brake device, and FIG. 5 is a diagram showing braking force distribution characteristics of the front wheels and the rear wheels.

  As shown in FIG. 1, the tandem master cylinder 10 includes first and second output ports 12 a and 12 b that output brake fluid pressure in accordance with a pedaling force that a driver steps on the brake pedal 11. The output port 12a is connected to the disc brake devices 13 and 14 for the left front wheel and the right rear wheel, for example, and the second output port 12b is connected to the disc brake device for the right front wheel and the left rear wheel, for example. In FIG. 1, only one brake system connected to the first output port 12a is shown, and the other brake system connected to the second output port 12b is not shown, but the structure of one and the other brake system is Substantially the same. Hereinafter, one brake system connected to the first output port 12a will be described.

  The first output port 12a of the master cylinder 10 and the wheel cylinder 15 of the disc brake device 13 of the front wheel are connected by liquid passages 17a to 17f, and the liquid passages 17g to 17j branched from the liquid passages 17c and 17d are rear wheels. Are connected to the wheel cylinder 16 of the disc brake device 14.

  A pedal force shut-off valve 18 which is a normally open electromagnetic valve is disposed between the liquid passages 17b and 17c, and a front motor cylinder 19F is disposed between the liquid passages 17d and 17e. The motor cylinder 19F includes a cylinder 20 disposed between the liquid passages 17d and 17e, and a piston 21 that is slidably fitted to the cylinder 20 is driven by an electric motor 22 via a speed reduction mechanism 23. Thus, the brake fluid pressure can be generated in the fluid chamber 24 formed on the front surface of the piston 21.

  Similarly, a rear wheel motor cylinder 19R is disposed between the liquid passages 17h and 17i. The motor cylinder 19R includes a cylinder 20 disposed between the liquid passages 17h and 17i, and a piston 21 that is slidably fitted to the cylinder 20 is driven by an electric motor 22 via a speed reduction mechanism 23. Thus, the brake fluid pressure can be generated in the fluid chamber 24 formed on the front surface of the piston 21.

  A stroke simulator 25 connected to the downstream end of the liquid passages 17k to 17n branched from the liquid passages 17a and 17b is a cylinder 26 slidably fitted with a piston 28 biased by a spring 27. A liquid chamber 29 formed on the side opposite to the spring 27 of the piston 28 communicates with the liquid path 17n. A reaction force permission valve 30 that is a normally closed electromagnetic valve is disposed between the liquid passages 17m and 17n. Further, liquid passages 17o and 17p branched from between the liquid passages 17g and 17h communicate with the reservoir 31 of the master cylinder 10, and an atmospheric valve 32 which is a normally closed electromagnetic valve is disposed between the liquid passages 17o and 17p. .

  As shown in FIG. 3, the master cylinder 10 is generated in the electronic control unit U that controls the operation of the pedal force cutoff valve 18, the reaction force permission valve 30, the atmospheric valve 32, and the electric motors 22 and 22 of the motor cylinders 19F and 19R. A hydraulic pressure sensor Sa for detecting the brake hydraulic pressure, a hydraulic pressure sensor Sb for detecting the brake hydraulic pressure transmitted to the disc brake device 13 for the front wheel, and a brake hydraulic pressure transmitted to the disc brake device 14 for the rear wheel. A fluid pressure sensor Sc to be detected is connected.

  As shown in FIG. 4, the wheel cylinders 15 and 16 of the disc brake device 13 for the front wheels and the disc brake device 14 for the rear wheels include a brake caliper 33 that is floatingly supported by the vehicle body so as to be movable left and right, and a brake disc that rotates together with the wheels. A pair of brake pads 35, 35 supported so as to be able to approach and separate from each other so as to sandwich 34, and a piston 37 slidably fitted into a cylinder hole 36 formed in the brake caliper 33, And a liquid chamber 38 formed on the back of the piston 37.

  In the present embodiment, the thickness T of the brake disc 34 of the disc brake device 14 for the rear wheel is set to be greater than the thickness T of the brake disc 34 of the disc brake device 13 for the front wheel.

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

  In the normal state shown in FIG. 1, the pedal force shut-off valve 18, the reaction force permission valve 30 and the atmospheric valve 32 are energized by a command from the electronic control unit U, the pedal force shut-off valve 18 is closed, and the master cylinder 10 and disc brake The communication between the devices 13 and 14 is cut off, the reaction force permission valve 30 is opened, the master cylinder 10 and the stroke simulator 25 are communicated, and the atmospheric valve 32 is opened. In this state, when the driver depresses the brake pedal 11 and the master cylinder 10 generates brake fluid pressure, the fluid pressure sensor Sa detects the brake fluid pressure in the fluid passage 17k closed by the pedal force shut-off valve 18. The electronic control unit U operates the front and rear wheel motor cylinders 19F and 19R so as to cause the fluid passages 17f and 17j to generate a fluid pressure corresponding to the brake fluid pressure detected by the fluid pressure sensor Sa.

  As a result, the driving force of the electric motor 22 of the front wheel motor cylinder 19F is transmitted to the piston 21 via the speed reduction mechanism 23, and the brake fluid pressure generated in the fluid chamber 24 of the cylinder 20 is transferred to the disc via the fluid passages 17e and 17f. The front wheel is braked by being transmitted to the wheel cylinder 15 of the brake device 13. At this time, the brake fluid pressure of the fluid passage 17f is detected by the fluid pressure sensor Sb, and the brake fluid pressure of the electric motor 22 is adjusted so that the brake fluid pressure becomes a value corresponding to the brake fluid pressure detected by the fluid pressure sensor Sa of the fluid passage 17k. The operation is feedback controlled.

  Similarly, the driving force of the electric motor 22 of the motor cylinder 19R for the rear wheel is transmitted to the piston 21 via the speed reduction mechanism 23, and the brake fluid pressure generated in the fluid chamber 24 of the cylinder 20 is transmitted via the fluid passages 17i and 17j. The rear wheel is braked by being transmitted to the wheel cylinder 16 of the disc brake device 14. At this time, the brake fluid pressure in the fluid passage 17j is detected by the fluid pressure sensor Sc, and the electric motor 22 is adjusted so that the brake fluid pressure becomes a value corresponding to the brake fluid pressure detected by the fluid pressure sensor Sa in the fluid passage 17k. The operation is feedback controlled.

  When the piston 21 in the cylinder 20 is slightly advanced by the electric motor 22, the communication between the liquid chamber 24 and the liquid path 17d (or the liquid path 17h) is cut off, so that the brake hydraulic pressure generated by the cylinder 20 is reduced. There is no risk of escape to the reservoir 31 via the atmospheric valve 32 provided between 17o and 17p.

  By the way, in the normal state described above, the pedal force shut-off valve 18 is kept closed unless an abnormal state such as a power failure occurs. Conventionally, the brake pads of the disc brake devices 13 and 14 are worn and the cylinders are worn. Even if the volume of the fluid passages 17e and 17f or the fluid passages 17i and 17j between the discs 20 and 20 and the disc brake devices 13 and 14 is increased, the corresponding brake fluid cannot be replenished from the reservoir 31, and the wheel cylinder There is a possibility that a problem that the drag of 15, 16 cannot be reduced occurs.

  However, when the pistons 21 and 21 are retracted in the cylinders 20 and 20, the fluid chambers 24 and 24 communicate with the reservoir 31 through the open air valve 32, and therefore, due to wear of the brake pads of the disc brake devices 13 and 14. Insufficient brake fluid can be replenished from the reservoir 31, and dragging of the wheel cylinders 15 and 16 when the braking force is released can be reduced.

  Further, when the driver depresses the brake pedal 11 and the master cylinder 10 generates the brake fluid pressure at the normal time, the brake fluid pressure is transmitted to the fluid chamber 29 of the stroke simulator 25 and the piston 28 resists the elastic force of the spring 27. Thus, a reaction force against the depression of the brake pedal 11 can be generated. As a result, although the disc brake devices 13 and 14 are actually operated by the driving force of the electric motors 22 and 22, the disc brake devices 13 and 14 are operated by the driver's stepping force. The operation feeling can be obtained.

  On the other hand, when the power supply is lost due to battery disconnection or the like, the pedal force shut-off valve 18 is opened as shown in FIG. 2 so that the master cylinder 10 and the disc brake devices 13 and 14 communicate with each other. The valve 30 is closed and communication between the master cylinder 10 and the stroke simulator 25 is cut off. The air valve 32 is closed and communication between the master cylinder 10 and the reservoir 31 is cut off. As a result, the brake fluid pressure generated by the master cylinder 10 when the driver depresses the brake pedal 11 is transmitted to the wheel cylinder 15 of the disc brake device 13 of the front wheel via the opened pedal force cutoff valve 18 and the motor cylinder 19F. Further, it is transmitted to the wheel cylinder 16 of the disc brake device 14 of the rear wheel via the opened pedal force cutoff valve 18 and the motor cylinder 19R, and the front wheel and the rear wheel are braked.

  At the same time, since the communication between the stroke simulator 25 and the master cylinder 10 is blocked by closing the reaction force permission valve 30, the stroke simulator 25 stops its function. As a result, it is possible to prevent the stroke of the brake pedal 11 from increasing unnecessarily and giving the driver an uncomfortable feeling, and the brake hydraulic pressure generated by the master cylinder 10 is not absorbed by the stroke simulator 25 and the wheel. It is transmitted to the cylinders 15 and 16, and the braking force can be generated with high responsiveness.

  Thus, even if the power supply fails and the pedal force cutoff valve 18, the reaction force permission valve 30, the atmospheric valve 32, and the motor cylinders 19F and 19R become inoperable, the driver steps on the brake pedal 11 and the master cylinder 10 moves. The generated brake fluid pressure can operate the front and rear wheel cylinders 15 and 16 without any trouble, thereby braking the front and rear wheels in an abnormal state and stopping the vehicle more safely.

  By the way, in the normal state described above, the brake fluid pressure is supplied from the front wheel motor cylinder 19F to the wheel cylinder 15 of the front wheel disc brake device 13, and the rear wheel motor cylinder is supplied to the wheel cylinder 16 of the rear wheel disc brake device 14. Since the brake fluid pressure is supplied from 19R, the braking force of the front wheels and the rear wheels can be independently controlled. Therefore, as shown in FIG. 5, the braking force distribution of the front wheels and the rear wheels in the normal state can be set to the ideal braking force distribution.

  The ideal braking force distribution is the distribution of the braking force of the front and rear wheels that can obtain the most efficient braking characteristics by simultaneously locking the front and rear wheels as the braking force increases. The braking force of the front wheels exceeds the braking force of the front wheels, and the braking force of the front wheels exceeds the braking force of the rear wheels during sudden deceleration at which locking is likely to occur. This is because the vehicle behavior may be disturbed if the rear wheel locks first during sudden deceleration.

  It is easy to obtain an ideal braking force distribution at normal times when the braking force of the front and rear wheels can be individually controlled. However, at the time of abnormal braking of the front and rear wheels by the common brake fluid pressure generated by the master cylinder 10, the front and rear wheels are controlled. The power cannot be individually controlled, and the braking force of the front and rear wheels is increased while maintaining a certain ratio in accordance with an increase in the depression force of the brake pedal. The ratio of the braking force of the front and rear wheels is determined by the ratio between the braking capability of the front wheel disc brake device 13 and the braking capability of the rear wheel disc brake device 14 when the same brake fluid pressure is supplied. For example, it can be set by the diameter of the brake disc 34. That is, when the same brake fluid pressure is supplied to the same wheel cylinder, a larger braking force can be obtained with a larger brake disc diameter.

  As described above, in order to obtain the ideal braking force distribution of the front and rear wheels in the normal state, the wheel cylinder 16 of the disc brake device 14 for the rear wheel is not enlarged to increase the braking capability, but the motor cylinder 19R for the rear wheel is used. Since the brake hydraulic pressure supplied to the wheel cylinder 16 of the disc brake device 14 for the rear wheel is increased, the rear wheel is increased by the enlarged wheel cylinder 16 in the event of an abnormality in which braking is performed with the brake hydraulic pressure generated by the master cylinder 10. It is possible to prevent the braking force of the wheels from being increased more than necessary and to disturb the vehicle behavior by locking the rear wheels before the front wheels.

  That is, in the present embodiment, the distribution of the braking force of the front wheels and the braking force of the rear wheels when 0.8 G (G is gravitational acceleration), which is the maximum vehicle body deceleration that can be expected in a normal road surface condition, is obtained. Since the ratio is set so as to be located on the line of the ideal braking force distribution characteristic of FIG. 5, the braking force distribution characteristic at the time of abnormality shown in FIG. Accordingly, the braking force is distributed between the front wheels and the rear wheels. In this abnormal-time braking force distribution characteristic, the braking force of the front wheels is reduced by making the diameter of the brake disc 34 of the disc brake device 14 of the rear wheel smaller than the diameter of the brake disc 34 of the disc brake device 13 of the front wheel. Since it is set to be higher than the braking force, the stability of the vehicle behavior can be maintained by locking the front wheels before the rear wheels.

  This will be further explained with reference to FIG. 5. When the braking force of the front and rear wheels is set to the abnormal time braking force distribution ratio and the normal system tries to realize the ideal braking force distribution ratio in the normal state, the rear wheel of BFr2 In order to generate the braking force, it is necessary to control the front wheel braking force of BFf3 with the electromagnetic on-off valve to reduce it to BFf1, which causes a problem that the efficiency of the system is remarkably reduced. In order to avoid this, the conventional braking force distribution ratio in which the rear wheel braking force distribution ratio is higher than the abnormal time braking force distribution ratio is adopted, and the front wheel braking force of BFf2 is reduced to BFf1 by the electromagnetic on-off valve. Absent.

  However, if this is done, the braking force of the rear wheels becomes excessive when the braking force distribution ratio of the front and rear wheels is fixed in the event of an abnormality, so the rear wheels may lock before the front wheels and disturb the vehicle behavior. is there. According to the present embodiment, it is possible to prevent the rear wheels from being locked by adopting the abnormal braking force distribution ratio in which the rear wheel braking force distribution ratio is small at the time of abnormality.

  Even if the diameters of the brake discs 34 of the front and rear wheel disc brake devices 13 and 14 are different, the brake hydraulic pressure supplied to the wheel cylinders 15 and 16 of the front and rear wheel disc brake devices 13 and 14 during normal operation is supplied to the motor cylinder 19F. , 19R can be arbitrarily controlled, and there is no problem in obtaining the ideal braking force distribution characteristic at the normal time.

  Further, when the same brake fluid pressure is supplied to the wheel cylinders 15 and 16 of the disc brake devices 13 and 14 for the front and rear wheels, the abnormal braking force distribution characteristic shown in FIG. 5 can be obtained. Then, the brake fluid pressure higher than that of the front wheel cylinder 15 is supplied to the rear wheel cylinder 16 by the motor cylinders 19F and 19R (see the hatched portion in FIG. 5). Therefore, the heat generation amount of the rear wheel brake disc 34 is larger than the heat generation amount of the front wheel brake disc 34, but the thickness T of the rear wheel brake disc 34 is made thicker than the thickness T of the front wheel brake disc 34. Therefore, it is possible to prevent the occurrence of a fade phenomenon by promoting the heat radiation of the brake disc 34 of the rear wheel that generates a large amount of heat.

  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.

Hydraulic system diagram for normal operation of BBW brake system Hydraulic system diagram at the time of abnormality corresponding to FIG. Block diagram of control system Diagram showing the structure of the disc brake device Diagram showing braking force distribution characteristics of front and rear wheels

10 Master cylinder 11 Brake pedal (brake operator)
15 Wheel cylinder 16 Wheel cylinder 18 Tread force shut-off valve (solenoid valve)
19F Motor cylinder (actuator)
19R Motor cylinder (actuator)
34 Brake disc U Electronic control unit (control means)

Claims (2)

A front wheel actuator (19F) for generating front wheel brake fluid pressure;
A rear wheel actuator (19R) for generating rear wheel brake fluid pressure;
Control means (U) for controlling the operation of both actuators (19F, 19R) in accordance with the operation of the brake operator (11) by the driver;
A master cylinder (10) that generates a brake fluid pressure in response to an operation of the brake operator (11) by the driver;
A front wheel wheel cylinder (15) for braking the front wheel;
A rear wheel wheel cylinder (16) for braking the rear wheel;
An electromagnetic valve (18) that shuts off communication between the master cylinder (10) and the wheel cylinders (15, 16) when both the actuators (19F, 19R) are normal, and allows communication between them when abnormal.
With
The braking force distribution between the front wheels and the rear wheels when the vehicle deceleration is 0.8G is ideal when the two cylinders (15, 16) are operated with the brake fluid pressure generated by the master cylinder (10). By making the diameter of the brake disc (34) of the rear wheel smaller than the diameter of the brake disc (34) of the front wheel so as to be distributed, the ratio of the braking force generated by both the wheel cylinders (15, 16) can be increased . A BBW brake device that is set.   2. The BBW brake device according to claim 1, wherein the thickness of the brake disc of the rear wheel is greater than the thickness of the brake disc of the front wheel. 3.

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