JPH0858558A - Master cylinder - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a master cylinder with good brake feeling. [Structure] A bottomed cylinder body 11 having a first inner peripheral portion 12a and a second inner peripheral portion 12b having a diameter smaller than that at one end, and a bottomed cylinder body 11 for accommodating hydraulic fluid therein. The first pressure chamber 12 and the second pressure chamber 13 are divided, and when the pressure of the first pressure chamber 12 becomes high, the pressure is set to the second pressure chamber.
Piston 15 forming a communication mechanism 26 for supplying to the pressure chamber
Is provided on the first inner peripheral portion 11a side, and the piston 15
Is arranged on the side of the second inner peripheral portion 12b and the first port 18 capable of communicating or blocking between the first pressure chamber 12 and the reservoir tank 17 according to the movement of the second pressure chamber 13 and the hydraulic pressure line. The pressure receiving area of the first pressure chamber 12 is larger than the pressure receiving area of the second pressure chamber 13 by having the second port 19 communicating with the second port 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a master cylinder for applying brake fluid pressure to a wheel cylinder of a vehicle, and more particularly to a portless master cylinder.

[0002]

2. Description of the Related Art As a conventional technique, for example, actual Kaihei 1-1
There is a master cylinder disclosed in Japanese Patent No. 61167.
This master cylinder is inserted into an inner hole of the cylinder body through a seal cup so as to be fluid-tight and slidable in the axial direction, and is constantly connected to a pressure chamber and a reservoir which are in continuous communication with the hydraulic pressure line in the inner hole. A piston having a communication hole that forms a communicating replenishment chamber and that communicates the pressure chamber and the replenishment chamber, a return spring that urges the piston toward a non-operating position, and a valve body that is fitted to one end A spring that biases the valve rod and the valve element that are loosely fitted in the communication hole in the seating direction,
A refill chamber in a master cylinder equipped with a valve mechanism that opens the communication hole when the piston is in the non-operating position, and closes the communication hole when the piston is in the operating position to generate hydraulic pressure in the pressure chamber. The side is formed with a small diameter step, and the cylinder collar that fits liquid-tightly between the small diameter part and the cylinder body inner hole is fixed to the cylinder body, and when the piston is in the non-operating position, the stopper is It comes into contact with the collar.If the valve mechanism and stopper are attached to the piston, and the piston is inserted into the inner hole of the cylinder body, then the cylinder collar is inserted from the inner hole opening and fixed near the inner hole opening end. Of course, this makes it possible to reduce the axial length of the master cylinder without deteriorating the assembling property.

[0003]

In the master cylinder described above, since the pressure receiving area of the pressure chamber that the piston pressurizes is always constant, the moving amount of the piston changes in proportion to the pushing force of the piston. That is, the pressure chamber in the cylinder body is pressurized in proportion to the force pushing the piston.

When the master cylinder is used in a vehicle brake device, when the vehicle is suddenly braked, that is, when the piston is suddenly pushed with a strong force, it is necessary to prevent the vehicle from braking too much and prevent the wheels from locking. There is. In addition, it is necessary to obtain a sufficient braking effect by a light brake operation when traveling at a relatively low speed in an urban area or the like. However, in the above master cylinder, when the brake is suddenly applied, that is, when the piston is suddenly pushed with a strong force, the brake of the vehicle may be too effective and the wheels may be locked.

Therefore, according to the present invention, when the brake pedal is lightly stepped on, the brake works well, and when the pedaling force of the brake pedal is further increased from that point, the brake pedal becomes heavy and the master brake has a short stroke and high rigidity. An object is to provide a cylinder.

[0006]

In order to solve the above problems, a master cylinder according to the present invention has a first inner peripheral portion and a second inner peripheral portion having a diameter smaller than that of the first inner peripheral portion at one end. A bottomed cylinder body for accommodating hydraulic fluid in the inner peripheral portion and the second inner peripheral portion, and a liquid-tight and slidable insertion into the cylinder body,
A first seal cup is provided between the first inner peripheral portion and the second inner cup, a second seal cup is provided between the second inner peripheral portion, and the first pressure chamber is provided between the second seal cup and the first seal cup. Forming a second pressure chamber between the bottom of the inner circumference of the cylinder body and the second seal cup, and the first pressure chamber when the piston is biased toward the bottom of the cylinder body. A valve mechanism for blocking between the second pressure chambers and for communicating between the first pressure chamber and the second pressure chamber when the piston is not biased toward the bottom of the cylinder body, and the first inner circumference. A first port that is arranged in the inner part and switches the communication between the first pressure chamber and the reservoir tank when the piston moves by a predetermined amount and the second tank is connected to the second pressure chamber and the wheel cylinder. The second port that always communicates with the hydraulic line
And a communication mechanism for supplying the hydraulic fluid in the first pressure chamber to the second pressure chamber when the pressure in the pressure chamber becomes higher than a predetermined pressure. Here, regarding the hydraulic pressure pipe line connected from the second port to the wheel cylinder, the second port and the wheel cylinder may be directly connected, or may be connected between the second port and the wheel cylinder via a solenoid valve or the like. You can either

[0007]

In the master cylinder of the present invention, when the piston operates, the valve mechanism blocks the first pressure chamber from the second pressure chamber, and the second pressure chamber is sealed. However, since the reservoir tank and the first pressure chamber communicate with each other until the first seal cup passes through the first port, the piston pressurizes only the second pressure chamber. Thereafter, when the first seal cup passes through the first port by further operating the piston, the first pressure chamber is closed. At this time, when the piston is further operated, the volume of the first pressure chamber is reduced. The hydraulic fluid of the reduced volume enters the second pressure chamber through the communication mechanism and is introduced into the hydraulic pressure conduit from the second port. Here, since the diameter of the first inner peripheral portion is larger than the diameter of the second inner peripheral portion, the area in which the piston receives the hydraulic pressure becomes large when the first seal cup passes through the first port. Therefore, if the piston is pushed so that the amount of movement of the piston is constant, the force received by the piston increases when the seal cup passes through the first port. Significant force must be applied to the piston to introduce the liquid.

[0008]

Embodiments of the master cylinder of the present invention will be described below with reference to the drawings.

In FIG. 1, the master cylinder 10 has a cylinder body 11. The cylinder body 11 has a first inner peripheral portion 11a at one end and also has a first inner peripheral portion 11a.
a second inner peripheral portion 1 which is continuous with a and has a smaller diameter than the first inner peripheral portion 11a.
1b has a first inner peripheral portion 11a and a second inner peripheral portion 11b.
It contains the working fluid. A liquid-tight and slidable fit is inserted into the inner peripheral portion of the cylinder body 11 via a seal cup 14, and the first inner peripheral portion 11a and the second inner peripheral portion 11 are inserted.
The first pressure chamber 12 and the second pressure chamber 13 are formed in b, respectively, and they are formed between the first pressure chamber 12 and the second pressure chamber 13, and when the pressure of the first pressure chamber 12 becomes high, A piston 15 having a communication hole 26 as a communication mechanism for supplying pressure to the second pressure chamber 13, and a return spring 1
6 are accommodated. The seal cup 14 is the first inner peripheral portion 1.
It is composed of a first seal cup 14a mounted on the 1a side and a second seal cup 14b mounted on the second inner peripheral portion 11b side. A first port 18 capable of communicating or blocking between the first pressure chamber 12 and the reservoir tank 17 according to the movement of the piston 15 is arranged in the first inner peripheral portion 11 a of the cylinder body 11, and the first port 18 of the cylinder body 11 is arranged. A second port 19 that constantly connects the second pressure chamber 13 and a wheel cylinder (not shown) is disposed on the inner peripheral portion 11b side.

The left side of the piston 15 in the figure is moved to the right in the figure by a return spring 16 whose one end is locked to the bottom surface of the second inner peripheral portion 11b (in the case of a single master cylinder) or a piston (not shown) (in the case of a tandem master cylinder). And is held in the non-actuated position shown in FIG. As a result, the piston 15 becomes the cylinder body 1.
A first pressure chamber 12 capable of communicating with or blocking the inside of the first inner peripheral portion 11a of the first through the first port 18 and the reservoir tank 17.
And a second pressure chamber 13 communicating with the first pressure chamber 12 through the valve mechanism and communicating with the hydraulic pressure line through the second port 19.

The valve mechanism in this embodiment will be described. The piston 15 has the first pressure chamber 12 and the second
Axial hole 15a and axial hole 15 that communicate with the pressure chamber 13
One end of a has a concave portion 15b that is open, and the other end of the axial hole 15a is open that has a through hole 15c that communicates with the axial hole 15a. The piston 15 has a small diameter portion 15d to which the first seal cup 14a is attached and a second diameter portion 15d.
It is formed in a stepped shape having a large-diameter portion 15e to which the seal cup 14b is attached.

In the valve mechanism, a valve body 20 which can be seated on a seat portion formed on the bottom surface of a recess 15b having one end of the axial hole 15a opened is fitted at one end to urge the valve body 20 in the seating direction. It is composed of a spring 22. Disc 2
A valve rod 21 is provided at the other end of
A retainer 25 is fitted to the tip of the valve 5 so that the valve body 20 does not come off from the recess 15b. Further, the valve rod 21 is movably locked in the axial direction on the bottom surface of the second inner peripheral portion 11b (in the case of a single master cylinder), and the piston 1
When 5 is in the inoperative position, the axial movement of the valve body 20 is restricted so that the valve body 20 does not sit in the recess 15b. This valve mechanism is regulated by the valve rod 21 so that the valve body 20 is not seated in the recess 15b when the piston 15 is in the inoperative position, and at this time, the first pressure chamber 12 and the second pressure chamber 13 are in communication with each other. .

In the valve mechanism as described above, when the piston 15 is in the non-operating position, the valve rod 21 is hooked on the bottom surface of the second pressure chamber 13 to open the axial hole 15a. Moves to the left in the drawing by operating the brake pedal, the valve rod 21
The position restriction of the valve body 20 due to is released, the valve body 20 is urged toward the bottom surface of the recess 15b by the spring force, and the axial hole 15a is closed to generate the hydraulic pressure in the second pressure chamber 13. Let

The operation of this embodiment having the above configuration will be described. A push rod 24 is fitted and inserted into one end of the piston 15, and when the push rod 24 and the piston 15 are pushed and slid to the left in the figure by the operation of a brake pedal (not shown), the valve body 20 is recessed by the spring 22. The first pressure chamber 12 and the second pressure chamber 12 are seated on the bottom surface of 15b.
The communication with the pressure chamber 13 is cut off and the second pressure chamber 1
A hydraulic pressure is generated in 3. However, the first seal cup 14
The reservoir tank 17 is provided before “a” passes through the first port 18.
Since the first pressure chamber 12 and the first pressure chamber 12 communicate with each other, no hydraulic pressure is generated in the first pressure chamber 12, and the piston 15 pressurizes only the hydraulic pressure of the second pressure chamber 13.

After that, when the first seal cup 14a passes through the first port 18 by further depressing the brake pedal, the first pressure chamber 12 is also sealed. Where the first
Since the diameter of the inner peripheral portion 11a is larger than the diameter of the second inner peripheral portion 11b, when the force applied to the piston 15 is constantly increased, the first seal cup 14a passes through the first port 18 and becomes the boundary. The movement amount of 15 is reduced. At this time, the first
Since the volume of the pressure chamber 12 decreases, the hydraulic fluid of the reduced volume enters the second pressure chamber 13 by pushing the second seal cup 14b toward the second pressure chamber 13 side from the communication hole 26, and the second port 19 Is introduced into the hydraulic line.

By returning the brake pedal to its original position, the piston 1 is urged by the urging force of the return spring 16.
When 5 is biased in the opening direction of the cylinder body 11, the volume of the first pressure chamber 12 increases and is sealed until the first seal cup 14a returns from the first port 18 to the opening side of the cylinder body 11. Therefore, of the hydraulic fluid in the second pressure chamber 13 returned from the wheel cylinder, the increased volume of the first pressure chamber is supplied to the first pressure chamber 12 via the communication hole 26. .

In this embodiment, a graph in which the horizontal axis represents the force pushing the piston 15 and the vertical axis represents the pressure applied to the wheel cylinder through the second port 19 is shown. In addition, the stroke amount of the piston 15 in this case is represented by the horizontal axis,
FIG. 3 is a graph in which the vertical axis represents the hydraulic pressure of the wheel cylinder. The dotted lines in the graphs of FIGS. 2 and 3 show the case of the master cylinder in which the pressure receiving area of the piston does not change. Contact point P in the graphs of FIGS. 2 and 3.
The pressure of can be arbitrarily set by changing the length of L in FIG.

From the above, the master cylinder 10 of this embodiment is
In the normal use range, the piston 15 pressurizes only the second pressure chamber 13 and the hydraulic pressure is supplied to the hydraulic pressure conduit. Therefore, for example, when the vehicle is traveling in the city area at a relatively low speed, a light brake is applied. A sufficient braking effect can be obtained by the operation. However, when the first seal cup 14a passes through the first port 18 by suddenly operating the piston 15 with a large force, such as when a sudden braking is applied while the vehicle is operating, the piston 15 also applies the first pressure chamber 12 to it. It will press. The passage of the first seal cup 14a through the first port 18 increases the pressure receiving area of the piston 15, which makes it possible to obtain a high-rigidity brake feeling with a short stroke, which results in a safe brake and a sudden brake. It also helps prevent the wheels from locking.

The valve mechanism of the present invention is not limited to the valve mechanism of this embodiment, and any valve mechanism having an equivalent action may be used. Also,
Although the communication hole is used as the communication mechanism in this embodiment, there is another method such as providing a relief valve between the first pressure chamber and the second pressure chamber. A communication hole that abuts the seal cup is preferable. Also, the second
If the hydraulic chamber is divided into two and the second port is provided for each of the hydraulic chambers and the hydraulic pipe is provided so as to communicate with another wheel cylinder, the tandem master cylinder can also be used.

[0020]

According to the master cylinder of the present invention, the inner circumference of the cylinder body is the first inner circumference and the second inner circumference having a smaller diameter than the first inner circumference, and the first inner circumference and the second inner circumference are respectively formed. By providing the piston that is divided into the first pressure chamber and the second pressure chamber, the piston pressurizes only the second pressure chamber and the hydraulic pressure is supplied to the hydraulic pressure conduit in the normal use range. When the seal cup passes through the first port by the operation of the piston, the piston pressurizes the first pressure chamber. The passage of the first seal cup through the first port increases the pressure receiving area of the piston, so that a highly rigid brake feeling with a short stroke can be obtained, and the brake feels secure. It also helps prevent wheel locking during sudden braking. Further, the master cylinder of the present invention can be used for both the hydraulic brake booster and the negative pressure brake booster, and can be manufactured at low cost because of its simple structure.

[Brief description of drawings]

FIG. 1 is a master cylinder according to an embodiment of the present invention.

FIG. 2 is a graph showing characteristics of a master cylinder of this embodiment.

FIG. 3 is a graph showing the characteristics of the master cylinder of this embodiment.

[Explanation of symbols]

 10 ... Master cylinder 11 ... Cylinder body 12 ... First pressure chamber 13 ... Second pressure chamber 14 ... Seal cup 15 ... Piston 16 ... Return spring 17 ... Reservoir Tank 18 ... First port 19 ... Second port 20 ... Valve element 21 ... Valve rod 22 ... Spring 24 ... Push rod 25 ... Retainer 26 ... Communication hole

Claims (1)

[Claims] 1. A first inner peripheral portion and a second inner peripheral portion having a diameter smaller than that of the first inner peripheral portion at one end, and a working fluid is contained in the first inner peripheral portion and the second inner peripheral portion. A first cylinder cup is inserted between the bottom cylinder body and the cylinder body so as to be liquid-tight and slidable, and has a first seal cup between the bottom cylinder body and the second inner periphery portion. Two seal cups are provided, a first pressure chamber is formed between the second seal cup and the first seal cup, and a second pressure chamber is formed between the bottom portion of the inner circumference of the cylinder body and the second seal cup. For closing the first pressure chamber and the second pressure chamber when the piston is urged in the bottomed direction of the cylinder body, and the piston is in the bottomed direction of the cylinder body. A valve mechanism that communicates between the first pressure chamber and the second pressure chamber when not biased to the first pressure chamber; A first port that is disposed in the inner peripheral portion and that switches from communication between the first pressure chamber and the reservoir tank to communication when the piston moves by a predetermined amount; and a second port that is disposed on the side of the second inner peripheral portion Second for constantly communicating the pressure chamber and the hydraulic pressure line connected to the wheel cylinder
A master cylinder, comprising: a port; and a communication mechanism that supplies the hydraulic fluid in the first pressure chamber to the second pressure chamber when the pressure in the first pressure chamber becomes higher than a predetermined pressure.