JPH1016760A - Braking device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a car braking device that is good in responsiveness, and also simple in structure, high in reliability as well as to prevent any pulsation of hydraulic pressure. SOLUTION: This braking device is equipped with a liquid chamber 2 whose one end is interconnected to the side of a wheel liquid chamber 3 and the other end is interconnected to the side of a brake liquid supplying part 4, a screw 5 being set up in this liquid chamber 2 and installed with a spiral surface 5d in and around a shank 5c, and an electric motor 6 being connected to this screw 5, respectively and in this constitution, this car braking device controls the hydraulic pressure in the wheel cylinder 3 by rotating the screw 5 by drive of the motor 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake system for a vehicle, and more particularly to a hydraulic pressure generating mechanism in a hydraulic brake.

[0002]

2. Description of the Related Art A brake system for a vehicle basically supplies a hydraulic pressure generated in a master cylinder by an operation of a brake pedal to a wheel cylinder, and drives a brake pad or a brake shoe to generate a braking force. It has become.

In an actual vehicle, a servo mechanism that assists the depressing force of a brake pedal by an exhaust pressure, a vacuum, or an electrically operated pump is employed.

[0004] Among them, the electric pump requires a motor and a speed reducer connected to the motor, and a structure in which the rotation of the speed reducer is converted into a piston motion by a ball screw to operate a hydraulic piston. Has been adopted. A desired braking force can be obtained by changing a voltage or the like applied to the motor.

[0005]

However, in the above-described apparatus using a motor, there is an inconvenience that responsiveness is lacking because the motor must be reversely rotated when shifting from the pressurized state to the released state. Also, since the number of mechanical parts increases,
There is a problem that the weight and dimensions tend to increase.

Therefore, a plunger type pump which can be relatively downsized is used at present, but the structure is complicated because a relief valve is required, and pulsation is generated in the brake fluid pressure, which is not preferable.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned conventional problems, and has a good responsiveness, a simple structure, a high reliability, and a vehicle brake which is free from hydraulic pressure pulsation. It is to provide a device.

[0008]

SUMMARY OF THE INVENTION The present invention is a vehicular braking system, and is configured as follows to solve the above-mentioned technical problem.

More specifically, a fluid chamber 2 having one end communicating with the wheel fluid chamber 3 and the other end communicating with the brake fluid supply unit 4 is provided around a shaft 5c disposed in the fluid chamber 2. A screw 5 having a spiral surface 5d and an electric motor 6 connected to the screw 5 are provided, and the screw 5 is rotated by the driving of the electric motor 6 to control the hydraulic pressure in the wheel cylinder 3. Features.

Hereinafter, important components of the present invention will be further described. [Liquid chamber 2] The liquid chamber 2 preferably has a cylindrical shape, and is desirably provided integrally with the brake caliper 1. The liquid chamber 2 and the brake caliper 1 do not need to be in the same housing, and may be separately integrated.

In the case of a disc brake, the brake caliper 1 is a frame formed so as to straddle a disc rotor. However, the present invention is not necessarily applicable to anything other than the disc brake system, and therefore, the brake caliper 1 is a concept including a general housing of hydraulic equipment around the wheel cylinder. [Wheel Cylinder 3] In the case of a disc brake, a piston that directly presses a brake pad is fitted into the wheel cylinder 3 in the case of a disc brake. [Brake fluid supply unit 4] The brake fluid supply unit 4 is for storing brake fluid, and may be a so-called reservoir. [Screw 5] Screw 5 is a rotatable shaft 5
The spiral surface 5d is formed one or more times around c, and preferably has about three or four steps, but is appropriately set according to the required pressure, required pressure characteristics, and the like. [Electric Motor 6] As the electric motor 6, a DC or AC servo or a general DC motor is preferable, and it is desirable that the rotating part has a light mass, a relatively high rotation can be obtained, and the response is excellent.

Incidentally, the screw 5 is established even in the following cases. The specific element is that the spiral surface 5d of the screw 5 has a variable pitch, that is, the pitch of the spiral surface 5d is different between the one end side and the other end side of the screw 5, and the screw 5 The pitch of the end facing the cylinder 3 is smaller (rougher) than the pitch of the end facing the brake fluid supply unit 4.

An electro-rheological fluid 7 whose viscosity changes by applying a voltage to the liquid chamber 2 is filled, and an electrode 8 is arranged in the liquid chamber 2 to apply an arbitrary voltage to the electrode. Power supply 9 can be connected. [Electro-Rheological Fluid 7] The viscosity of the electro-rheological fluid 7 changes depending on the applied voltage. For example, when the voltage is not applied, the viscosity is low and the flow is easy, and when the voltage is applied, the viscosity is high and the flow is difficult to flow. Has properties. Examples of such an electrorheological fluid 7 include an electrically insulating oil such as silicone oil and transformer oil, a polystyrene-based ion exchange resin, a crosslinked polyacrylate, cellulose,
A so-called Winslow fluid in which solid particles such as hydroxides of polyvalent metals and potassium titanates are dispersed can be exemplified. [Electrode 8] The electrode 8 applies a voltage to the electrorheological fluid 7. For example, a positive electrode and a negative electrode may be provided at both ends of the liquid chamber 2, or an inner wall of the liquid chamber 2 may be provided. The positive pole and the screw 5 may be a negative pole. [Power supply unit 9] The power supply unit 9 is for applying a DC voltage to the electrode 8. Examples of the voltage control method include a resistance type and a high frequency chopper.

The operation of the above configuration will be described. When a brake is required, the electric motor 6 is operated to rotate the screw 5. Then, the screw 5 generates an axial flow, supplies the brake fluid from the brake fluid supply unit 4 direction to the wheel cylinder 3 as pressure oil, and increases the fluid pressure in the wheel cylinder 3. The degree of this rise is determined by the number of rotations of the screw 5 per predetermined time,
The fluid pressure (braking force) intended by the driver is obtained.

As described above, the braking force is obtained by the rotation of the screw 5, but when the braking force is released, when the rotation of the screw 5 is stopped, the brake fluid flows between the spiral surfaces around the screw 5 (in the groove). Then, the brake fluid is returned from the high-pressure wheel cylinder 3 to the low-pressure brake fluid supply unit 4 and the brake is released.

In this case, when the helical surface 5d of the screw 5 has a variable pitch, it is possible to optimize the change in hydraulic pressure. That is, the cross-sectional area between the spiral surfaces in the axial direction of the screw 5 (trough cross-sectional area) is determined by the brake fluid supply unit 4.
By gradually changing from small to large from the side (suction side) to the wheel cylinder 3 side (discharge side), the law of flow continuity (the flow velocity is inversely proportional to the cross-sectional area of the flow tube,
The flow velocity of the brake fluid changes from fast to slow because the flow velocity decreases on the side with the larger cross-sectional area. Therefore, according to Bernoulli's theorem (the sum of pressure energy, velocity energy, and potential energy is constant for each cross section), velocity energy is converted to pressure energy, pressure changes from small to large, and the pressure rise capacity of the device Can be improved.

The liquid chamber 2 is filled with an electrorheological fluid 7 so that an arbitrary voltage can be applied to the electrorheological fluid 7. It can be set arbitrarily by changing the viscosity of the brake fluid with the output of the section 9. That is, the wheel cylinder 3
When it is desired to obtain a high pressure, the viscosity may be increased by applying a predetermined voltage to the brake fluid (the electrorheological fluid 7) in addition to the rotation speed of the screw 5. To steepen the pressure gradient at the time of pressure reduction, the application of the voltage to the brake fluid may be stopped (or reduced) to lower the viscosity. As described above, by using the electrorheological fluid 7 as the brake fluid (working fluid), the pressure control capability in the wheel cylinder 3 can be increased, and the responsiveness of the brake can be further improved.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a vehicle braking system according to the present invention will be described in more detail with reference to the embodiments shown in FIGS. Embodiment 1 Embodiment 1 will be described with reference to FIG.
A brake caliper 1 serving as a housing of the brake mechanism is for a disc brake, and a wheel cylinder 3 is provided in the brake caliper 1. The brake piston 10 is fitted in the wheel cylinder 3. An O-ring 11 is provided on the inner wall of the wheel cylinder 3 so that the brake piston 10 and the wheel cylinder 3 are fluid-tight.

The brake piston 10 is for pressing a brake pad 12a. The brake pad 12a, together with a brake pad 12b provided at the end of the brake caliper 1, sandwiches a disk rotor 13. I have. And brake piston 1
When 0 moves in the arrow F direction, the brake pads 12a,
12b acts so as to clamp the disk rotor 13 and brake its rotation.

A cylinder-shaped liquid chamber 2 is provided inside the brake caliper 1. One end of the liquid chamber 2 communicates with the wheel cylinder 3 via a liquid passage 15, and the other end of the liquid chamber 2 is connected to a brake fluid supply unit provided on the upper portion of the brake caliper 1 via a liquid passage 17. (Reservoir) 4. And the liquid chamber 2
Inside, a screw 5 is pivotally supported with a very small clearance with respect to the inner wall of the liquid chamber 2. In this screw 5, a screw 5e having a spiral surface 5d is wound around a shaft 5c. One end of the shaft 5 a located at the center of the screw 5 is supported by a ball bearing 14. Further, the other end of the shaft 5a is pivotally supported by the brake caliper 1.

The shaft 5a is connected to an electric motor 6 via a coupler 5b. Thereby, the electric motor 6
Is transmitted to the screw 5.
The rotation of the electric motor 6 is controlled by a controller 19.

The fluid chamber 2, the wheel cylinder 3, and the brake fluid supply unit 4 are filled with brake fluid. The operation of the above configuration will be described. When a brake is required, the electric motor 6 is operated by an instruction signal from the controller 19 to rotate the screw 5. Then, the screw 5 generates an axial flow in the direction indicated by the arrow F, sucks the brake fluid from the reservoir 4 via the fluid passage 17, and supplies the pressurized fluid from the fluid chamber 2 to the wheel cylinder 3 via the fluid passage 15. The hydraulic pressure in the wheel cylinder 3 is increased, and the brake piston 10 is pressed in the direction of arrow F. As a result, the brake pads 12a and 12b pinch the disk rotor 13 to brake its rotation, and the brake is activated.

The pressing force of the brake pads 12a and 12b against the disk rotor 13 is determined by the number of rotations of the screw 5 per unit time, and the controller 19 outputs an output so as to obtain the fluid pressure (braking force) intended by the driver. Control.

On the other hand, when releasing the brake, when the rotation of the screw 5 is stopped, the brake fluid returns to the brake fluid supply unit 4 on the low pressure side through the space between the spiral surfaces 5d of the screw 5 (in the groove). Since the hydraulic pressure in the wheel cylinder 3 decreases, the brake pads 12a and 12b separate from the disk rotor 13 and the brake is released.

As described above, since the electric motor 6 does not rotate in the reverse direction, the responsiveness of the brake is extremely good. Further, since the device does not require a valve, the structure is simplified, and the size and weight can be reduced. When releasing the brake,
It goes without saying that the electric motor 6 may be rotated in the reverse direction to rotate the screw 5 in the reverse direction.

Further, since the pump operation for supplying the brake fluid to the wheel cylinder 3 is all performed by the rotation of the screw 5, no pulsation occurs. [Embodiment 2] Embodiment 2 of the present invention will be described with reference to FIG. In this embodiment, the pitch of the helical surface 5d is different between one end and the other end of the screw 5, and the pitch of the end facing the wheel cylinder 3 is the end facing the brake fluid supply unit 4. Less than pitch (coarse)
Let me do it.

The reason why the thread 5e of the screw 5 is made to have a variable pitch is to improve the pressure increasing ability on the wheel cylinder 3 side. That is, the screw 5 faces the wheel cylinder 3 side by making the pitch of the spiral surface 5d on the end side facing the wheel cylinder 3 side larger than the pitch on the end side facing the brake fluid supply unit 4 side. This means that the thread 5e on the end side has a relatively large cross-sectional area of the valley.

For this reason, the screw 5 in the liquid chamber 2
On the end side facing the wheel cylinder 3 side, the flow velocity becomes slower due to the law of flow continuity (the flow velocity becomes slower on the side having a larger cross-sectional area), and velocity energy is converted to pressure energy from Bernoulli's theorem. It will be. Therefore, in the liquid chamber 2, the pressure increases in the brake fluid supply direction, and the pressure on the wheel cylinder 3 side can be more efficiently increased.

Other configurations and operations are the same as those of the first embodiment.
Therefore, the same portions are denoted by the same reference numerals and description thereof will be omitted. Third Embodiment A third embodiment of the present invention will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the third embodiment, the brake fluid filled in the fluid chamber 2, the wheel cylinder 3, and the brake fluid supply unit 4 is changed to an electrorheological fluid 7 whose viscosity changes when a voltage is applied.

Further, an electrode 8a to which one end of a power supply unit 9 is connected is arranged in the liquid chamber 2, and the other end of the power supply unit 9 is connected to a screw 5 to form an electrode 8b. The electrodes 8a and 8b are insulated from other metal parts by an insulator (not shown).

As described above, the voltage supplied from the power supply unit 9 is applied to the electrorheological fluid 7, so that the viscosity of the electrorheological fluid 7 can be changed at a high speed. The output voltage of the power supply unit 9 is controlled by a controller 19. The controller 19 controls the electric motor 6 based on signals from a brake pedal 20 and a pressure sensor 21 provided in communication with the wheel cylinder 3.

The reason why the electrorheological fluid 7 is used is that a high wheel cylinder pressure can be obtained by a high viscosity obtained by applying a voltage. In order to obtain a high wheel cylinder pressure, the rotation of the screw 5 may be increased or a highly viscous brake fluid may be used. However, the rotation of the screw 5 has a limit, and a simply highly viscous brake fluid is always used. In this case, although the rate of increase in hydraulic pressure at the time of starting the brake is improved, there is a problem in that the brake fluid pressure is not easily reduced due to the high viscosity at the time of release.

In the third embodiment, to solve this,
When the brake is activated, a voltage is applied from the power supply unit 9 to the electrorheological fluid (brake fluid) 7 to increase the viscosity and assist in increasing the pressure. On the other hand, when the brake is released, the application of the voltage to the electrorheological fluid 7 is stopped to reduce the viscosity. The pressure is reduced to facilitate the pressure release.

The controller 19 includes the pressure sensor 2
The pressure in the wheel cylinder 3 is detected based on the signal from 1 and the viscosity of the brake fluid 7 can be changed so as to be a pressure corresponding to the operation amount of the brake pedal 20. That is, when it is desired to control the pressure in the wheel cylinder 3 to a higher pressure, the controller 19 outputs an instruction signal to the power supply unit 9 so as to increase the voltage applied to the electrorheological fluid 7, and receives a signal from the pressure sensor 21. Control is performed such that the voltage applied to the electrorheological fluid 7 is stopped or reduced when the internal pressure of the wheel cylinder 3 reaches a predetermined pressure.

As described above, since the degree of the fluid pressure change between when the brake pressure is applied and when the brake pressure is released can be arbitrarily set, a strong braking force can be obtained, and the brake can be released more smoothly. Therefore, the present invention can be applied to an antilock brake system and a traction brake system that precisely increase and decrease the brake pressure in a short time, and can greatly contribute to vehicle stability.

[0037]

According to the vehicle brake system of the present invention, the brake fluid pressure is controlled by the rotation of the screw, so that the responsiveness is very good and fine brake control is possible. Moreover, it is possible to provide a highly reliable vehicle braking device having a simple structure. Further, compared to a reciprocating pump, there is no pulsation of hydraulic pressure, so that the brake feeling is excellent.

Further, when the spiral surface of the screw has a variable pitch, it is possible to optimize the fluid pressure change from the brake fluid supply unit side to the wheel cylinder side, thereby improving the pressure increasing capability of the wheel cylinder pressure. An apparatus can be provided.

Further, in the case of using an electrorheological fluid as the brake fluid, it is possible to obtain a device capable of obtaining a stronger brake fluid pressure while maintaining a good response to the application of the brake fluid. Fine control is also possible.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a vehicle braking device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a vehicle braking device according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a vehicle braking device according to a third embodiment of the present invention.

[Explanation of symbols]

 1. Brake caliper 2. Liquid chamber 3. Wheel cylinder 4. Brake liquid supply unit (reservoir) 5. Screw 5a Shaft 5b Coupler 5c Shaft 5d Spiral surface 5e Screw 6. Electric motor 7. Electro-rheological fluid (brake fluid) 8, 8a, 8b Electrode 9. Power supply unit 10. Brake piston 12a, 12b Brake pad 13. Disc rotor 19. Controller 20 Brake pedal 21 Pressure sensor

Claims (3)

[Claims] A fluid chamber having one end communicating with the wheel cylinder and the other end communicating with the brake fluid supply unit; and a screw provided in the fluid chamber and having a helical surface around a shaft. An electric motor connected to the screw, wherein the electric motor drives the screw to rotate the screw to control the hydraulic pressure in the wheel cylinder. 2. A pitch of a spiral surface of one end of the screw is different from a pitch of a spiral surface of the other end thereof, and a pitch of an end facing the wheel cylinder is larger than a pitch of an end facing the brake fluid supply unit. 2. The method as claimed in claim 1, wherein the number is reduced.
The vehicle braking device according to claim 1. 3. The liquid chamber is filled with an electrorheological fluid whose viscosity changes by applying a voltage, and an electrode is disposed in the liquid chamber, and a power supply for applying a predetermined voltage is connected to the electrode. The vehicle braking device according to claim 1, wherein: