JPS631635Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a master cylinder with a negative pressure booster for brakes or clutches, which is mounted on a vehicle or the like and whose operation is assisted by negative pressure.

There are various types of master cylinders with negative pressure boosters, but recently a cylinder body with a straight cylinder hole opening at the rear has been developed to minimize the axial length. , an actuating piston whose increased diameter portion is slidably and tightly fitted into the cylinder hole to define a brake fluid pressure generation chamber at the front, and whose rear end protrudes into the negative pressure booster casing; A negative pressure booster has been developed, which has a through hole in which a reduced diameter part rearward of the increased diameter part of the working piston is slidably and tightly fitted, and a guide member fixed to the cylinder body. ing.

In general, in a master cylinder or a tandem master cylinder, an operating piston is slidably and tightly fitted into a straight cylinder hole, but as is well known, this operating piston is fitted with a recess formed at its rear end. At this point, it slides forward under the pressure of the push rod. The actuating piston is formed with at least two diameter-increasing parts spaced apart from each other, which are slidably and tightly fitted into the cylinder bore.
Even if the pushing force from the push rod deviates from the axis of the cylinder hole, it will slide stably along the axis of the cylinder hole.

However, in the above-mentioned master cylinder with a negative pressure booster, there is usually only one push rod, that is, the increased diameter part that tightly fits into the cylinder hole of the operating piston that receives the pushing force of the output shaft of the negative pressure booster. A guide member for guiding the operating piston along the axis of the cylinder hole is required in the boundary area between the negative pressure booster and the master cylinder. Conventionally, for example, in the guide member disclosed in Japanese Unexamined Patent Publication No. 56-2249, the guide member has a cylindrical shape as a whole, and its outer peripheral surface is concentric with the linear cylinder hole at the rear end of the cylinder body. The piston is tightly fitted into a continuously formed hole having a larger diameter than the cylinder hole, and the reduced diameter portion of the actuating piston is slidably and tightly fitted into the center hole. However, in such a guide member, the cylinder hole and the large diameter hole into which the guide member is tightly fitted are precisely concentric, and the outer peripheral surface of the guide member and the center hole are precisely concentric. There is no problem if the concentricity is incorrect, but if any of the concentricity is incorrect, the actuating piston will not be guided smoothly by the guide member and the inner wall of the cylinder hole, and uneven force will be applied to the guide member and the inner wall of the cylinder hole, causing damage to these parts. This may cause wear and unstable operation. Therefore, eliminating such problems requires considerable work efficiency, which reduces productivity accordingly.

Furthermore, in the above-mentioned publication, an axial passage is formed that communicates the supply chamber, that is, the chamber that communicates with the reservoir formed around the rear portion of the increased diameter portion of the piston, and the reservoir. As a means of communication between this passage and the supply chamber, a sealing material with a large outer diameter and a support ring for this purpose are provided, but these are means for increasing the axial length relatively, and the guide of the piston is not sufficient. Even if it can be ensured, it is not used if the amount of intrusion into the negative pressure booster becomes large and the space inside the negative pressure booster is limited.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a master cylinder with a negative pressure booster that improves productivity compared to the conventional one while shortening the length of the entire device. This purpose, according to the present invention, includes a cylinder body having a straight cylinder hole that is open at the rear, a reservoir attached to the body, and an increased diameter portion that is slidably fitted into the cylinder hole. an actuating piston defining a brake fluid pressure generation chamber and having a rear end protruding into the negative pressure booster casing, and a reduced diameter portion rearward of the increased diameter portion of the actuating piston that is slidably fitted into the actuating piston. In the master cylinder with a negative pressure booster, the guide member has a through hole for matching and is fixed to the cylinder body. having a flange portion that abuts, the reduced diameter portion of the actuating piston is slidably fitted and inserted into the center hole of the cylindrical portion, and the outer circumferential surface of the cylindrical portion is fitted into the cylinder hole;
an axial passage formed in the cylinder body along the axial direction thereof and communicating with the reservoir;
A passage connecting a liquid chamber formed between an increased diameter portion of the actuating piston and a cylindrical portion of the guide member is in contact with an outer circumferential surface of the cylindrical portion of the guide portion and a rear end surface of the cylinder body of the flange portion. A master cylinder with a negative pressure booster, characterized in that the guide member is formed on the contacting surface side, and the guide member is fixed to the cylinder body by a cover member that covers a rear end of the cylinder body. It is achieved by doing so.

Hereinafter, a tandem master cylinder with a negative pressure booster according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a partially cutaway side sectional view of a tandem master cylinder with a negative pressure booster according to a first embodiment of the present invention. In addition, in this specification, the front and the back refer to the left side and the right side in a figure, respectively.

In FIG. 1, the tandem master cylinder section is indicated as a whole by 1, and the negative pressure booster section and the reservoir section integrated therewith are indicated as 2 and 3 as a whole, respectively. Negative pressure booster section 2
Since it has a known structure, most of the structure is omitted to simplify the drawing.

In the tandem master cylinder section 1, the cylinder body M has a linear cylinder hole 1a,
An operating piston 4 and an auxiliary piston 5 are slidably and tightly fitted into this cylinder hole 1a. Working piston 4
is slidably and tightly fitted into the cylinder hole 1a with an increased diameter part 4a formed near its front end, and a sealing member 10 is fitted in the reduced diameter part 4b in front of the cylinder hole 1a. It defines a fluid pressure generation chamber. Further, a bolt 7 that engages with a bottom hole of a cup-shaped spring retainer 6 is screwed onto the front end of the operating piston 4, and a spring 8 is connected to the spring retainer 6.
and a spring receiver 9 that is in contact with the front end of the actuating piston 4.

The sub-piston 5 is slidably and tightly fitted into the cylinder hole 1a with a pair of front and rear enlarged diameter parts 5a, and the sealing member 1 is in contact with the reduced diameter parts 5b and 5c, respectively.
1 and 12 are fitted. As a result, the above-described first hydraulic pressure generating chamber is formed between the sealing members 10 and 11, and a second hydraulic pressure generating chamber is formed in front of the sealing member 12. These hydraulic pressure generating chambers are connected to the wheel cylinders through discharge ports formed in the cylinder body M, although not shown. Further, a spring receiver 13 is fitted into the reduced diameter portion 5b of the sub-piston 5,
A spring 14 is connected between this and the front wall of the cylinder body M.
is set up. The spring 14 urges the sub-piston 5 rearward, and the spring 8 urges the working piston 4 and the sub-piston 5 in opposite directions.

A guide member 15 according to the present invention is disposed in contact with the rear end surface of the cylinder body M, and the rear reduced diameter portion 4c of the operating piston 4 slides into the center through hole of the cylindrical portion 15c formed at the center thereof. It is freely and tightly fitted, and the rear end protrudes into the negative pressure chamber in the casing 24 of the negative pressure booster section 2. Further, the outer peripheral surface of the cylindrical portion 15c of the guide member 15 is the cylinder body M.
The cylinder hole 1a is tightly fitted. Therefore, since the outer circumferential surface of the cylindrical portion 15c and the center through hole are concentric, the actuating piston 4 is guided into the cylinder hole 1a by the guide member 15 without eccentricity with respect to the axis of the cylinder hole 1a of the cylinder body M. Ru.

The guide member 15 is in contact with the rear end surface of the cylinder body M at its flange portion 15a, and is fixed to the cylinder body M by a cup-shaped cover member 17 in addition to sealing members 16 and 22 attached thereto. That is, the cover member 17 is
5 and the rear part of the flange part f of the cylinder body M, the bent front edge part 17a of the cover member 17 is engaged with the opening of the casing 24 of the negative pressure booster part 2, and the sealing member 23 The cover member 17 is fixed to the cylinder body M by fixing the casing 24 to the flange portion f of the cylinder body M with bolts (not shown). That is, the guide member 15 is firmly fixed to the cylinder body M.

By fixing the flange part f of the cylinder body M to the casing 24 of the negative pressure booster section 2 with bolts, the tandem master cylinder section 1 and the negative pressure booster section 2 are integrated. As shown in FIG. Since there is no need to increase the axial length of the booster, the axial length of the entire tandem master cylinder with negative pressure booster of this embodiment, that is, the length in the front and back direction, can be made much smaller than before. can. Further, as shown in the drawings and as will be described later, the reservoir portion 3 can also be provided within the length region of the front portion of the tandem master cylinder portion 1 from the flange portion f even in the above configuration.

The sealing member 23 interposed between the cylinder body M, the casing 24 and the cover member 17 has a substantially L-shaped cross section as shown in FIG. When fixed, it is compressed and deformed as shown in FIG. 1, but due to the crushing deformation of the annular protrusions 23a, 23b, and 23c as shown in FIG. ,
That is, a sufficient sealing state between the negative pressure chamber and the cylinder body M can be obtained. Furthermore, the sealing member 1
6, 22, cylinder body M and casing 2
4 and are kept in a sealed state.

The cylinder body M is integrally formed with a boss portion 40 that protrudes upward, and the reservoir portion 3, which will be described later, is fixed to this.
The interior is further divided into two brake fluid storage chambers by a partition wall 41 formed integrally with the cylinder body M. Of these, the front storage chamber communicates with the second hydraulic pressure generation chamber through a return hole 20 formed in the cylinder body M, and also communicates with the secondary piston through a supply hole 21 similarly formed in the cylinder body M. It communicates with a replenishment chamber formed between both the enlarged diameter portions 5a of No.5. On the other hand, the rear storage chamber communicates with the first hydraulic pressure generating chamber through a passage 18 formed in the axial direction of the cylinder body M and extending to the rear end surface, and a return hole 19 formed in the radial direction in communication with the passage 18. are doing. An annular groove 15a is formed on the inner surface of the flange portion 15d of the guide member 15, and an axial groove 15b is formed on the outer peripheral surface of the cylindrical portion 15c in communication with the annular groove 15a. Therefore, the above-mentioned rear brake fluid storage chamber is connected via the passage 18 and the grooves 15a and 15b.
The cylindrical portion 15c of the guide member 15 and the operating piston 4
It communicates with a replenishment chamber formed between the increased diameter portion 4a.

A recess 4d is formed at the rear end of the actuating piston 4, and the output shaft 25 of the negative pressure booster unit 2 is in contact with the bottom of this recess 4d, but the illustrated state shows when the brake is not operating. There is. In order to regulate the return position of the working piston 4, a stopper is required, but this is shown as being provided in the casing 24 of the negative pressure booster section 2 in this embodiment. . Alternatively, the guide member 1
The cylindrical portion 15c of No. 5 may be used as a stopper.

In the reservoir section 3, a buffle member 34 equipped with a seal ring is fitted into the upper opening of a reservoir main body 32 made of a substantially cylindrical synthetic resin, and a cap 31 is further attached through this. The reservoir body 32 has a spring ring 3 at its lower end.
9 is fixed to the boss portion 40 of the cylinder body M in a fluid-tight manner. Near the lower end of the reservoir body 32,
A reed switch holding cylindrical portion 33 is formed integrally with this in the radial direction, into which a reed switch 38 is inserted, and its lead wire is led out.

Further, a filter tube 35 is inserted into the reservoir body 32, and as shown in FIG.
Projection 43 formed on the inner circumferential wall of the reservoir body 32
The reed switch is placed on the reed switch holding cylindrical portion 33 by being engaged with the reed switch so that the reed switch is prevented from rotating. A screen 44 is attached to the filter tube 35, and a float 36 is inserted into the tube portion 42 below the screen 44. A notch similar to the notch 46 shown in FIG. 2 is formed on the peripheral surface of the float 36, and a protrusion similar to the protrusion 43 shown in FIG. 2 formed on the inner peripheral surface of the cylindrical portion 42. float 36 due to engagement with
is prevented from rotating with respect to the cylindrical portion 42, and the cylindrical portion 4
2 is guided in the vertical direction. As shown in the figure, a magnetized permanent magnet 37 is fixed to the bottom of the float 36, and prevents the filter cylinder 35 from rotating relative to the reservoir body 32 and the float 36 from rotating relative to the cylindrical portion 42 as described above. When the amount of liquid stored decreases and the float 36 comes into contact with the reed switch holding cylinder 33 as shown in the figure, the magnetic flux of the permanent magnet 37 effectively acts on the reed switch 38 to ensure that the liquid level alarm device is activated. I am trying to make it work.

The embodiment of the present invention is configured as described above,
Next, this action and effect will be explained.

When using this embodiment, brake fluid is supplied to a predetermined level within the reservoir body 32 of the reservoir section 3. This causes the float 36 to float from the position shown to a predetermined level. When a brake pedal (not shown) is stepped on, an input shaft (not shown) of the negative pressure booster section 2 is driven, and thereby an output shaft 25 is driven by a known structure and operation. That is, the output shaft 25 pushes the actuating piston 4 forward. The actuating piston 4 thus moves forward, and hydraulic pressure is generated in the first hydraulic pressure generating chamber. Due to this hydraulic pressure and the biasing force of the spring 8, the sub-piston 5 also moves forward against the spring force of the spring 14, and hydraulic pressure is also generated in the second hydraulic pressure generating chamber. These hydraulic pressures are supplied to the wheel cylinders through discharge ports (not shown), and the brakes are applied. When the pedal force is released from the brake pedal in order to release the brake, the output shaft 25 moves backward, and at the same time, the operating piston 4 and the sub-piston 5 return to the illustrated positions by the spring force of the springs 8 and 14.

In the above operation, the reduced diameter portion 40 of the working piston 4 is guided by the cylindrical portion 15c of the guide member 15 inside the cylinder hole 1a of the cylinder body M along the axis without eccentricity. Note that the increased diameter portion 4a that fits into the cylinder hole 1a of the actuating piston 4 is the reduced diameter portion 4.
It is assumed that it is formed concentrically with c. As described above, the actuating piston 4 is guided without eccentricity with respect to the axis of the cylinder hole 1a, so that the actuating piston 4 moves back and forth smoothly, which prevents uneven wear from occurring in the increased diameter part 4a and the reduced diameter part 4c. There is no. Further, the processing of the guide member 15 maintains concentricity between the center through hole of the cylindrical portion 15c and the outer circumferential side, so that the outer circumferential side fits into the cylinder hole 1a, and the reduced diameter portion of the actuating piston 4 is inserted into the center through hole. The guide member 15 can be fixed to the cylinder body M by making it contact with the rear end surface of the cylinder body M and fixing the cover member 17 to the casing 24. Compared to the conventional method of forming a hole with a larger diameter in the cylinder body M concentrically with the cylinder hole 1a and fitting the guide member into the hole, the machining is much easier, and moreover, the working piston It is easy to obtain concentricity between the members for moving the cylinder along the axis of the cylinder hole.

FIG. 4 is a side sectional view of the main parts of a tandem master cylinder with a negative pressure booster according to the second embodiment of the present invention. shall be attached.

This embodiment is completely the same as the first embodiment except for the shapes of the guide member and cover member and the omission of the sealing member 22. That is, compared to the guide member 15 of the first embodiment, the guide member 50 of this embodiment has a simpler shape as it does not have a recess for accommodating the sealing member 16.
2 is formed with a recess 52a for accommodating the sealing member 51. The rest of the structure is exactly the same as the first embodiment, and the same functions and effects as described above can be obtained.

Each embodiment of the present invention has been described above, but
Of course, the present invention is not limited to these, and various modifications can be made based on the technical idea of the present invention.

For example, in the above embodiment, the guide members 15, 50
The flange portions 15d, 50d of the cylindrical portions 15c, 5
Although they are formed concentrically as shown in FIG. 0c, they do not necessarily have to be formed concentrically. In this case, the cover member may be appropriately deformed to match the outer shape of the portion other than the flange portion or the cylindrical portion.

Also, the cover members 17 and 52 are omitted and the shapes of the flange portions of the guide members 15 and 50 are changed,
Directly to the cylinder body M or negative pressure booster section 2
It may be fixed to the casing 24 of.

As described above, in the master cylinder with a negative pressure booster of the present invention, the guide member has a cylindrical part in the center and a flange part that comes into contact with the rear end surface of the cylinder body, and the guide member has a flange part that comes into contact with the rear end surface of the cylinder body. slidingly fitting and inserting the reduced diameter portion of the actuating piston;
The outer peripheral surface of the cylindrical portion is fitted into the cylinder hole, and an axial passage is formed in the cylinder body along the axial direction and communicates with the reservoir, an increased diameter portion of the actuating piston, and the cylinder body. A passage communicating with a liquid chamber formed between the cylindrical portion of the guide member and the cylindrical portion of the guide member is formed on the outer circumferential surface of the cylindrical portion of the guide portion and on the side of the flange portion that contacts the rear end surface of the cylinder body, In addition, since the guide member is fixed to the cylinder body by a cover member that covers the rear end of the cylinder body, the device is particularly suitable for the so-called conventional type master cylinder as shown in the above embodiments. While shortening the overall length and reducing the amount of intrusion into the negative pressure booster compared to before, machining to obtain concentricity between the cylinder hole, operating piston, and guide member is easier than before, increasing production efficiency. can be improved.

[Brief explanation of the drawing]

FIG. 1 is a partially broken side sectional view of a tandem master cylinder with a negative pressure booster according to the first embodiment of the present invention, FIG. 2 is a sectional view along the - line in FIG. An enlarged partial cross-sectional view of the sealing member and FIG. 4 are cross-sectional views of essential parts of a tandem master cylinder with a negative pressure booster according to a second embodiment of the present invention. In the figure, 1... tandem master cylinder part, 1a... cylinder hole, 2... negative pressure booster part, 4... working piston, 4a... diameter increasing part, 4
c...Reduced diameter part, 15, 50...Guide member, 15
c, 50c... Cylindrical portion, 17, 52... Cover member.

Claims (1)

[Scope of utility model registration request] A cylinder body having a linear cylinder hole that is open at the rear, a reservoir attached to the body, and an increased diameter portion thereof slidably fitted into the cylinder hole to define a brake fluid pressure generation chamber at the front. and has an actuating piston whose rear end protrudes into the negative pressure booster casing, and a through hole into which a reduced diameter portion rearward of the increased diameter portion of the actuated piston is slidably fitted; In the master cylinder with a negative pressure booster, the guide member has a cylindrical portion in the center and a flange portion that comes into contact with the rear end surface of the cylinder body; The reduced diameter part of the actuating piston is slidably fitted and inserted into the center hole of the cylindrical part, the outer circumferential surface of the cylindrical part is fitted into the cylinder hole, and the reduced diameter part of the actuating piston is fitted and inserted into the center hole of the cylinder body, and the outer circumferential surface of the cylindrical part is fitted into the cylinder hole. An axial passage is formed in the cylindrical part of the guide part and communicates with the fluid chamber formed between the increasing diameter part of the actuating piston and the cylindrical part of the guide part. The guide member is formed on the outer peripheral surface and the side of the flange that contacts the rear end surface of the cylinder body, and the guide member is fixed to the cylinder body by a cover member that covers the rear end of the cylinder body. A master cylinder with a negative pressure booster featuring the following.