JP2542887B2 - Tandem master cylinder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Purpose of the Invention (1) Field of Industrial Application The present invention relates to a tandem master cylinder used for a vehicle brake or the like.

(2) Conventional Technology Conventionally, as this type of master cylinder, a front piston is slidably fitted in a cylinder hole of a cylinder body through a sleeve, and a rear piston is slidably fitted in the front piston. A space between the front end wall and the front piston is defined as a front hydraulic chamber, and an inside of the front piston and an annular space defined between the outer circumference of the front piston and the inner circumference of the cylinder hole so as to communicate therewith are defined as a rear hydraulic chamber. There is a known one (for example, see Japanese Patent Publication No. 62-33977). In the known one, the front and rear pistons are spaced forward and backward because the rear piston is slidably inserted into the front piston. There is an advantage that axial miniaturization can be achieved as compared with a tandem type master cylinder of a type in which columns are arranged in a row.

(3) Problems to be Solved by the Invention However, in the above-mentioned known device, the volume of the front hydraulic chamber is relatively small, but the volume of the rear hydraulic chamber is relatively large for the following reason. That is, according to the above configuration, in order to always communicate the inner space of the front piston with the rear output port of the cylinder body through the lateral hole of the front piston peripheral wall regardless of the forward movement position of the front piston, Between the outer circumference of the piston and the inner circumference of the cylinder body, it is necessary to specially define an outer annular hydraulic chamber that is long in the axial direction and has a large diameter and a relatively large volume. Since the rear hydraulic chamber is constituted by, the total volume of the rear hydraulic chamber becomes relatively large.

By the way, since some bubbles are generally mixed in the hydraulic oil, when the volume of the rear hydraulic chamber is large as in the conventional one, the amount of hydraulic oil in the rear hydraulic chamber increases and The amount of mixed bubbles also increases, and as a result, when the master cylinder operates, the pressure increase in the rear hydraulic chamber tends to be somewhat delayed.

The present invention has been proposed in view of the above, and it is possible to efficiently increase the pressure in both the hydraulic chambers by reducing the volumes of the rear hydraulic chambers as well as the front hydraulic chambers, and the axial lines of the front and rear pistons. An object of the present invention is to provide the master cylinder in which both pistons can be operated smoothly without accurately matching each other and the accuracy control is facilitated.

B. Configuration of the Invention (1) Means for Solving the Problems In order to achieve the above object, the present invention slidably fits a cylindrical front piston having a rear end surface open to a cylinder hole of a cylinder body. A front hydraulic chamber is defined between the front piston and the cylinder hole front end wall, and the rear piston slidably fitted to the end wall member closing the rear end of the cylinder hole is attached to the front part. A rear hydraulic pressure that is inserted in the piston with a radial clearance and includes a front region in the front piston and a rear region sandwiched between the rear end of the front piston and the facing surface of the end wall member. The cylinder body is provided with a rear output port in the cylinder body that communicates with the rear area of the rear hydraulic chamber.Before supplying hydraulic oil to the front hydraulic chamber between the outer peripheral surface of the front piston and the inner peripheral surface of the cylinder hole. It is characterized in that the front part replenishment oil chamber is defined and the front piston return spring is arranged in the front part replenishment oil chamber. To.

(2) Action The front part replenishing oil chamber, in which the return spring for the front part piston is arranged, is defined on the outer circumference of the front part piston. Not only the volume of the chamber but also the internal volume of the front piston itself, that is, the volume of the front region of the rear hydraulic chamber can be made as small as possible. On the other hand, the rear region of the rear hydraulic chamber is sufficient if it is simply in communication with the rear output port formed in the cylinder body, and therefore, the axial facing interval between the rear end of the front piston and the end wall member at the backward limit is set. It can be packed as much as possible, and the volume of the rear region can be made as small as possible. As a result, the volume is reduced in both the front and rear hydraulic chambers, and the amount of bubbles generated from the hydraulic oil in each hydraulic chamber is reduced.

Although the front end of the rear piston is inserted into the front piston in order to shorten the axial direction of the master cylinder, the insertion is done with radial play, so that the axial lines of the front and rear pistons do not interact with each other. Even if they do not exactly match, no unbalanced load such as twisting acts on the two pistons, and both pistons can be operated smoothly.

(3) Embodiment An embodiment of the present invention will be described below with reference to the drawings. M is a tandem master cylinder for a two-system hydraulic brake of an automobile, the cylinder body 1 of which is a negative cylinder supported by a vehicle body (not shown). The rear end portion is fixed to the front surface of the booster shell 2 of the pressure booster B.

An auxiliary oil sump cylinder 3 is integrally provided on the upper side of the cylinder body 1, and a main oil sump cylinder 4 is connected thereto. The main oil sump 4 has a cap 5 at the upper end and a known oil level sensor 6 supported by the cap 5 inside.

Internal auxiliary oil reservoir cylinder 3 is partitioned into front and rear oil reservoir 8 _1, 8 ₂ by a partition 7, these oil reservoir 8 _1, 8 ₂ is supplemented with hydraulic fluid from the main oil reservoir tube 4, respectively.

The front oil sump 8 ₁ communicates with the cylinder hole 10 of the cylinder body 1 through the front side relief port 12 and the rear side supply port 13 existing at the bottom of the bottom part, and the rear oil sump 8 ₂ opens on the side surface thereof. It communicates with the cylinder hole 10 through the communication hole 11 and the communication hole 9 branched from the communication hole 11.

The cylinder hole 10 includes a first hole 10a having a closed front end, and a first hole 10a.
Second hole 10b and second hole 1 having a diameter larger than that and connected to the rear end
The third hole 10c has a diameter larger than 0b and is connected to the rear end thereof, and the rear end is open. The relief port 12 opens in the rear part of the first hole 10a, and the supply port 13 opens in the front part of the second hole 10b. Further, the through hole 9 in the rear part opens in the middle part of the third hole 10c.

An end wall member 14 is fitted and held in the third hole 10c, and the end wall member 14 is composed of front and rear annular bodies 14 ₁ and 14 ₂ .

The first hole 10a and a second hole 10b, the cylindrical front piston 16 ₁ having an open rear end face is fitted slidably and end wall members 1
A rear piston 16 ₂ is slidably fitted to the 4 and the front outer periphery of the rear piston 16 ₂ is inserted into the front piston 16 ₁ with a clearance s in the radial direction. As a result, the front hydraulic chamber 17 _{1 is located} between the front piston 16 ₁ and the front end walls a and b of the first hole 10 a.
And a rear hydraulic chamber 17 ₂ is defined between the front end wall b of the front piston 16 _{1 and} the end wall member 14. Therefore, the rear hydraulic chamber 17 ₂ is connected to the front portion or 17a in the front piston 16 ₁ .
And a rear region 17b sandwiched between the rear end of the front piston 16 ₁ and the facing surface of the end wall member 14. Rear piston 16 ₂
And the seal member 18 to seal between the end wall member 14 is attached to the rear annular member 14 _{and second} end wall member 14.

Front and rear output ports 19 ₁ and 19 ₂ are formed in the cylinder body 1 so as to communicate with the two brake hydraulic circuits, and the front output port 19 ₁ communicates with the front hydraulic chamber 17 ₁ and the rear output port. 19 ₂ communicates with the rear region 17b of the rear hydraulic chamber 17 ₂ .

The rear end of the rear piston 16 ₂ extends to the rear of the cylinder body 1 and penetrates the front wall of the booster shell 2 to form a negative pressure booster B.
It is connected to the output rod 22 of. In order to prevent the negative pressure inside the rear piston 16 ₂ from leaking through the through hole 23 of the booster shell 2 through which the rear piston 16 ₂ penetrates, a seal member 24 having a lip closely contacted with the outer peripheral surface of the rear piston 16 ₂ is provided in the cylinder body 1 and It is sandwiched between booster shells 2.

A front replenishing oil chamber 26 ₁ communicating with the supply port 13 is defined between the front outer peripheral surface of the flange portion 16a and the inner peripheral surface of the second hole 10b of the front piston 16 ₁ . A seal member 27 that blocks between the front replenishment oil chamber 26 ₁ and the rear region 17b of the rear hydraulic chamber 17 ₂ is mounted on the front piston 16 ₁ between the flange portion 16a and the annular protrusion 16b behind the flange portion 16a. In rear annular member 14 _{and second} end wall member 14, an annular groove 25 is formed in the front seal member 18, the rear replenishing fluid chamber 26 ₂ is defined between the annular groove 25 and the inner peripheral surface and the third hole 10c . A stop bolt 28 having a through hole 9 is screwed to the cylinder body 1 across the communication hole 11,
The tip engages the front inner side surface of the annular groove 25, thereby the rear annular member 14 ₂ is retaining held in the third hole 10c.

A return spring 29 ₁ for urging the front piston 16 ₁ in the backward direction is arranged in the front replenishment oil chamber 26 ₁ . Also rear piston 16 ₂
A bolt 30 projecting in the axial direction by a certain length is screwed to the front end of the, and a hat-shaped spring holding cylinder 31 is slidably connected to the bolt 30 within a certain stroke range. Its spring holding cylinder
Between 31 and rear piston 16 ₂ and thus front piston 1
Return spring 2 that biases the rear piston 16 ₂ in the backward direction in 6 ₁
9 ₂ are provided. In this case, the set load of the spring 29 ₂ return of the rear piston 16 ₂ side back of the front piston 16 ₁ side spring 29
_It is set larger than the set load of ₁ .

The rear piston 16 ₂ is held in a predetermined retreat limit by abutting the annular step portion 32 at the front end thereof to the front annular body 14 ₁ by the elastic force of the return spring 29 ₂ , and the front piston 16 ₁ is returned by the return spring. 29 ₂ of resilient force is maintained at a predetermined backward limit.

In the front piston 16 ₁ , the piston portion 16c that slides in the first hole 10a has a plurality of oil holes 33 that communicate with the front replenishment oil chamber 26 _1.
Is formed. Small diameter part 16d on the front side of piston part 16c
Further, a front one-way seal member 34 ₁ which allows only the flow of hydraulic oil from the oil hole 33 to the front hydraulic chamber 17 ₁ is mounted with its lip closely contacting the inner peripheral surface of the first hole 10 a. The front end of the front one-way seal member 34 ₁ is held by a retainer 35 attached to the front end of the small diameter portion 16d, and is interposed between the front one-way seal member 34 ₁ and the piston portion 16c in the small diameter portion 16d. annular spacer 36 ₁ is mounted. The relief port 12 is located just before the front one-way seal member 34 ₁ at the retreat limit of the front pistons 16 ₁ and 16 ₂ .

In the end wall member 14, the rear annular member 14 a plurality of radial grooves 37 on the front of ₂ is formed, also a plurality of communicating the respective radial grooves 37 and the rear replenishing fluid chamber 26 ₂ to the front side wall of the annular groove 25 An oil hole 38 is formed. Also on the front annular body 14 _1, the radial grooves 3
A concave annular seal mounting portion 39 that opens toward the 7 and the rear piston 16 ₂ and a plurality of oil holes 40 that connect the seal mounting portion 39 and the rear region 17b of the rear hydraulic chamber 17 ₂ are formed. The seal mounting portion 39 is provided with a rear one-way seal member 34 ₂ which allows only the flow of the hydraulic oil from the rear replenishment oil chamber 26 ₂ to the rear region 17b.
The outer peripheral lip is attached so as to be in close contact with the inner peripheral surface of the seal mounting portion 39. The rear one-way sealing member 34 ₂ and the rear annular body 1
4 annular spacer 36 ₂ is mounted on the rear piston 16 ₂ between the _two.

_On the outer peripheral surface of the rear piston 16 ₂ , the piston 16 ₂
An annular recess 41 is formed which faces the seal mounting portion 39 at the retreat limit and is separated from the inner peripheral lip of the rear one-way seal member 34 ₂ and the recess 41 constitutes a part of the relief port of the rear hydraulic chamber 17 _2. To do. The inner peripheral lip of the rear one-way sealing member 34 _2, the recess 41 is in close contact with the rear piston 16 _second outer peripheral surface when migrating to the lip forward.

 Next, the operation of this embodiment will be described.

Now, when the negative pressure booster B is actuated to move the output rod 22 forward, both pistons 16 ₁ and 16 ₂ are pushed by it and move forward while compressing the corresponding return springs 29 ₁ and 29 ₂ . The front one-way sealing member 34 ₁ of the front piston 16 ₁
Moves to the front of relief port 12 and the front piston
16 hydraulic pressure is generated in the front hydraulic chamber 17 ₁ in accordance with the _first advancing force, also when the annular recess 41 of the rear piston 16 ₂ moves forward of the rear one-way sealing member 34 _2, the forward force of the rear piston 16 ₂ hydraulic pressure is generated in the rear pressure chamber 17 ₂ in accordance with the.

Thus, the hydraulic pressures generated in the front and rear hydraulic chambers 17 ₁ and 17 ₂ are output from the corresponding front and rear output ports 19 ₁ and 19 _2, and the hydraulic brakes of the two systems are simultaneously actuated to brake the vehicle. be able to.

In this case, the spring 29 _first return of the front piston 16 ₁ is disposed in the front replenishing fluid chamber 26 _1, the volume of the front hydraulic chamber 17 ₁ is reduced, thereby the front hydraulic chamber 17 ₁ Amount of hydraulic oil,
Therefore, the amount of bubbles can be reduced and the pressure in the hydraulic chamber 17 ₁ can be increased efficiently.

On the other hand, the rear hydraulic chamber 17 ₁ has a front area 17 in the front piston 16 ₁ .
a and the rear region 17b, in this case the front piston 16
_{Due to the fact} that the front replenishment oil chamber 26 ₁ is defined on the outer circumference, it is possible to reduce the diameter of the front piston 16 ₁ to reduce the internal volume thereof, and the rear area 17b is connected to the rear output port 19 ₂ . Since its main purpose is to provide the communication of the rear hydraulic chamber 172, the volume thereof may be small, which reduces the volume of the rear hydraulic chamber 17 ₂ to reduce the amount of hydraulic oil in the rear hydraulic chamber 17 ₂ and thus the amount of bubbles. The pressure in the hydraulic chamber 17 ₂ can be efficiently increased.

If the negative pressure booster B is returned to the inoperative state in order to release the braking, the front and rear pistons 16 ₁ and 16 ₂ will have corresponding return springs 2.
The elastic forces of 9 ₁ and 29 ₂ bring them back to their respective setback limits. When the front hydraulic chamber 17 ₁ is depressurized during the backward movement,
Since the lip of the front one-way seal member 34 ₁ bends toward the front hydraulic chamber 17 ₁ side due to the front-back pressure difference, the hydraulic oil in the front oil reservoir 8 ₁
The oil is supplied to the front hydraulic chamber 17 ₂ through the supply port 13, the front replenishment oil chamber 26 ₁ , the oil hole 33, and the outside of the lip of the front one-way seal member 34 ₁ . If this time is over supply of hydraulic fluid to the front hydraulic chamber 17 ₂ is performed, the excess is the front piston 16
_{When 1} returns to the backward limit, it is returned to the front oil sump 8 ₁ through the relief port 12.

On the other hand, when the rear hydraulic chamber 17 ₂ is depressurized in the retreat process, the outer peripheral lip of the rear one-way seal member 34 ₂ bends toward the rear hydraulic chamber 17 ₂ due to the front-back pressure difference, so that the rear oil sump 8 ₂ hydraulic oil, the communication hole 11, the through hole 9, the rear replenishing fluid chamber 26 _2, oil hole 3
The oil is supplied to the rear hydraulic chamber 17 ₂ through the radial groove 37, the outer peripheral lip of the rear one-way seal member 34 ₂ and the oil hole 40. At this time, when the rear hydraulic chamber 17 ₂ is excessively replenished with hydraulic oil, the excessive amount of oil is applied to the oil hole 40 and the inner peripheral lip of the rear one-way seal member 34 ₂ when the rear piston 16 ₂ returns to the backward limit. The oil is returned to the rear oil sump 8 ₂ through the inner side, the radial groove 37, the oil hole 38, the rear supply oil chamber 26 ₂ , the through hole 9 and the communication hole 11.

C. Effect of the Invention As described above, according to the present invention, a cylindrical front piston having an open rear end surface is slidably fitted in the cylinder hole of the cylinder body, and the front piston and the front end wall of the cylinder hole. A front hydraulic chamber is defined between the rear piston and a rear piston slidably fitted to an end wall member that closes the rear end of the cylinder hole, and a radial play is provided in the front piston. The cylinder body is inserted to define a rear hydraulic chamber including a front region in the front piston and a rear region sandwiched between the front end of the front piston and the facing surface of the end wall member. A rear output port communicating with the rear region of the rear hydraulic chamber is provided, and a front replenishing oil chamber for replenishing the front hydraulic chamber with working oil is defined between the outer peripheral surface of the front piston and the inner peripheral surface of the cylinder hole. Since the return spring of the front piston is installed in the front replenishment oil chamber, the front replenishment oil chamber where the return spring is located In order to reduce the diameter of the front piston in a relationship defined by the outer periphery of the stone, not only the volume of the front hydraulic chamber located in front of the front piston but also the internal volume of the front piston itself, that is, the front portion of the rear hydraulic chamber The volume of the area can be minimized.
On the other hand, the rear region of the rear hydraulic chamber is sufficient if it is simply in communication with the rear output port formed in the cylinder body, and therefore, the axial facing interval between the rear end of the front piston and the end wall member at the backward limit is set. It can be packed as much as possible, and the volume of the rear region can be made as small as possible. As a result, the volume of each of the front and rear hydraulic chambers can be reduced, and the amount of bubbles generated in the hydraulic oil in those hydraulic chambers can be reduced. Therefore, the pressure in the front and rear hydraulic chambers can be increased efficiently. You can

Although the front end of the rear piston is inserted into the front piston in order to shorten the axial direction of the master cylinder, the insertion is done with radial play, so that the axial lines of the front and rear pistons do not interact with each other. Both pistons can be operated smoothly even if they are not exactly matched,
Therefore, it is possible to easily control the accuracy of processing and assembling each piston.

[Brief description of drawings]

The drawing is a vertical sectional front view showing an embodiment of the present invention. a ... front end wall, s ... radial play, 1 ... cylinder body, 10 ... cylinder hole, 14 ... end wall member, 16 ₁ , 16 ₂ ......
Front and rear pistons, 17 ₁ , 17 ₂ ...... Front and rear hydraulic chambers, 17a, 1
7b ...... front, rear area, 19 ₂ ...... rear output port, 26 ₁ ...... front replenishing oil chamber, 29 ₁ ...... return spring

Claims (1)

(57) [Claims] 1. A cylinder hole (10) in a cylinder body (1).
A cylindrical front piston (16 ₁ ) having an open rear end surface is slidably fitted to the front hydraulic chamber between the front piston (16 ₁ ) and the cylinder hole (10) front end wall. (17 ₁₎ fraction forms a,
An end wall member (1) for closing the rear end of the cylinder hole (10)
4) the slidably mated rear piston (16 ₂₎ by inserting at the front piston (16 ₁₎ in the radial direction in the clearance (s), the said front piston (16 ₁ ) Front area (17a)
And the rear end of the front piston (16 ₁ ) and the end wall member (1
Defining a rear pressure chamber (17 ₂₎ comprising a rear region sandwiched between the facing surfaces of 4) and (17b), wherein the cylinder body (1), a rear region of the rear hydraulic chamber (17 ₂₎ (17b ) the rear output port (19 ₂₎ communicating with the provided between said front piston (16 ₁₎ outer peripheral surface and the cylinder bore (10) inner peripheral surface, the hydraulic oil in the front hydraulic chamber (17 ₁₎ defining the front replenishing fluid chamber (26 ₁₎ to be supplied, the the said front replenishing fluid chamber (26 ₁₎ the front piston (1
6 ₁ ) return spring (29 ₁ ) is provided,
Tandem master cylinder.