JPH064412B2 - Tandem brake booster - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a tandem type brake booster used in a brake system of an automobile or the like, and particularly to shorten the axial dimension (overall length) to reduce the size. The present invention relates to a tandem type brake booster capable of achieving the above.

(Prior art) In recent years, in response to higher engine speed and higher output, many vehicles use a brake booster that utilizes the negative pressure of the intake pipe of the engine to double the pedal effort of the brake pedal and output it to the master cylinder. The device is installed. Then, when a particularly large output is required, a tandem brake booster is used.

Here, an example of the tandem type brake booster will be described with reference to FIG.
Is the front shell 2, center shell 3 and rear shell 4
The inside of the main body 5 formed by is divided into a front chamber and a rear chamber by a center plate 6, and the front chamber is divided into a front constant pressure chamber 9 and a front variable pressure chamber 10 by a front power piston 8 equipped with a diaphragm 7. The rear chamber is divided into a rear constant pressure chamber 13 and a rear variable pressure chamber 14 by a rear power piston 12 having a diaphragm 11. Further, the front shell 2 is provided with a negative pressure introducing pipe 15 for connecting a negative pressure source such as an intake manifold (not shown) to the front constant pressure chamber 9.

A guide rod 16 extends in the front-rear direction in the main body 5 through the front shell 2, the rear shell 4 and the power pistons 8 and 12. This guide rod 16
When the inside of the main body 5 becomes negative pressure, it has a function of supporting the main body 5 so as not to be deformed, and a function of guiding the forward and backward movements of the power pistons 8 and 12, which are even in the circumferential direction of the main body 5. Are provided at two locations (only one location is shown). The guide rod 16 is fixed to the main body 5 by a flange 16a integrally formed on the front side and a nut 17 screwed on the rear side. Each of the power pistons 8 and 12 and the center plate 6 is formed with escape holes 8a, 12a and 6a through which the guide rod 16 penetrates.

Further, on the outside of the guide rod 16, a bellows-shaped first bellows 18 made of an elastic material such as rubber is provided on one end of the front shell 2 in order to maintain airtightness between the front constant pressure chamber 9 and the front variable pressure chamber 10. Is fixed to the front power piston 8, and the other end is engaged with the relief hole 8a of the front power piston 8. The front pressure change chamber 10 and the rear pressure change chamber 14 are communicated with each other and the rear constant pressure chamber 13 is kept airtight. In order to do so, the bellows-shaped second bellows 19 made of an elastic material such as rubber has one end engaged with the escape hole 6a of the center plate 6 and the other end engaged with the escape hole 12a of the rear power piston 12. It is provided.

Next, the valve mechanism 20 will be described.

The front power piston 8 is attached to a center body 22 to which an output shaft 21 is connected.
Valve body 24 via reaction disc 23
Is slidably fitted to. Further, the rear power piston 12 is attached to the valve body 24. A return spring 25 is interposed between the center body 22 and the front shell 2, and the front power piston 8 is interposed via the center body 22 and the valve body 24.
The rear power piston 12 is always biased rearward.

The valve body 24 has a rear end protruding from the main body 5 to the outside, and the protruding portion is formed in a cylindrical shape. A cylinder portion 24a is formed inside in the axial direction, and a plunger 26 is slidably fitted in the cylinder portion 24a.

Inside the valve body 24, a poppet valve 27 is provided, and its tip is attached to a valve seat 24b formed on the inner circumference of the valve body 24 and a valve seat 26a formed on the rear end of the plunger 26. It is located so that it can be seated. In addition,
The input shaft 28 is connected to the plunger.

Further, the center body 22 is formed with a communication hole 22a for communicating the front constant pressure chamber 9 and the rear constant pressure chamber 13, and the valve body 24 has an inner side of the valve body 24 and the rear constant pressure chamber 13 formed therein.
A passage 24c that communicates with the rear constant pressure chamber 14
4d and are formed.

According to this configuration, since the front constant pressure chamber 9 and the rear constant pressure chamber 13 are communicated with each other by the communication hole 22a of the center body 22 before operation, both chambers 9 and 13 are in a negative pressure state.

When the brake pedal is depressed and the input shaft 28 is moved forward, the plunger 26 moves forward relative to the valve body 24, the valve seat 26a of the plunger 26 and the poppet valve 27 are separated, and the atmosphere passes through the passage 24d. Introduced in the street rear transformer room 14. Further, the atmosphere is also introduced into the front transformer room 10 through between the second bellows 19 and the guide rod 16. As a result, a differential pressure is generated between the front constant pressure chamber 9 and the front variable pressure chamber 10, and between the rear constant pressure chamber 13 and the rear variable pressure chamber 14, and the front power piston 8 and the rear power piston 12 move forward. As a result, the valve body 24 is advanced with a large force, and the thrust is transmitted to the output shaft 21.

When the depression force of the brake pedal is released, the valve body 24 moves forward relative to the plunger 26, the valve seat 24b of the valve body 24 separates from the poppet valve 27, and the valve seat 26a of the plunger 26 moves the poppet valve 27. By sitting on
At the same time as the introduction of air into each transformer room 10 and 14 was cut off,
Since the constant pressure chambers 9 and 13 and the variable pressure chambers 10 and 14 are communicated with each other through the passage 24c of the valve body 24, the differential pressure decreases, and the return spring 25 causes the power pistons 8 and 12 to move to the initial stage. Returned to position.

(Problems to be solved by the invention) By the way, in automobiles and the like, it is desired to reduce the weight of the vehicle body in order to improve fuel efficiency and acceleration performance. There is a strong demand for miniaturization and miniaturization.

And the above-mentioned conventional tandem type brake booster 1
However, miniaturization is desired. However, the radial dimension cannot be reduced because the pressure receiving areas of the power pistons 8 and 12 are uniquely determined by the set output performance.

Therefore, if the total length is shortened, the stop position when the front power piston 8 moves forward is not shown.
It depends on the operation stroke of the master cylinder connected to the front power piston 8, but as shown in FIG. 4, the stop position of the front power piston 8 and the front shell 2 must be kept in proportion to the contraction amount when the first bellows 18 contracts. A gap of a certain size must be set between them, which is a constraint when trying to shorten the total length. Therefore, there is a problem that the tandem brake booster 1 cannot be sufficiently miniaturized and lightened.

The present invention has been made to meet the above-mentioned demand, and an object thereof is to reduce the overall length of the main body of a tandem brake booster.

(Means for Solving the Problems) As means for achieving the above object, in the tandem brake booster, the outside of the guide rod 16 is surrounded to maintain airtightness between the front constant pressure chamber 9 and the front variable pressure chamber 10. An expandable first bellows 30 is provided with one end fixed to the front power piston 8 and the other end fixed to the rear shell 4. Further, the front variable pressure chamber 10 and the rear variable pressure chamber 14 are communicated with each other, and the rear constant pressure is fixed. An expandable second bellows 31 for maintaining airtightness with the chamber 13 is provided by fixing one end to the rear power piston 12 and the other end to the center plate 6 so as to surround the outside of the first bellows 30. It will be.

(Operation) According to this configuration, the first bellows 30 and the second bellows
31 has a double structure, and the first bellows 30 is located behind the front power piston 8, so that the first bellows 30 extends as the front power piston 8 advances. Therefore, the front bellows of the front power piston 8 does not have a shrinkage margin, and accordingly, the front shell 2 can be positioned rearward and the overall length of the main body 5 can be shortened.

(Embodiment) Next, a tandem brake booster 28 according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. In addition,
The same members as those described in the related art are designated by the same reference numerals and the description thereof will be omitted.

The front side of the guide rod 16 is fixed to the front shell 2 by an integrally formed flange 16a, and the rear side of the guide rod 16 is fixed to the rear shell 4 by a nut 29 that is screwed. And front power piston 8 and rear power piston 12
Further, the center plate 6 is formed with escape holes 8a, 12a, 6a through which the guide rod 16 penetrates.

The first bellows 30 has a front power piston 8 at one end.
The guide rod 16 is engaged with and fixed to the escape hole 8a formed at the other end, and the other end is engaged with and fixed to a nut 29 for fixing the guide rod 16 to the rear shell 4. Further, the first bellows 30 is made of an elastic material such as rubber in a bellows shape, and has a flexible structure.

By providing the first bellows 30 in this way, the airtightness between the front constant pressure chamber 9 and the front variable pressure chamber 10 is ensured.

Next, the second bellows 31 is located outside the first bellows 30, one end of which is engaged with the relief hole 6a of the center plate 6 and the other end of which is the relief hole 12a of the rear power piston 12.
It is fixed by engaging with. And the first bellows 30
Similarly to the above, the elastic member such as rubber is formed into a bellows shape and is configured to be expandable and contractible.

With the above configuration, when the input shaft 28 advances by depressing a brake pedal (not shown), the plunger 26 moves forward relative to the valve body 24, and the valve seat 26 of the plunger 26 moves.
The a and the poppet valve 27 are separated from each other, and the atmosphere is introduced into the rear variable pressure chamber 14 through the passage. Further, the atmosphere is introduced into the front transformer room 10 through the space between the first bellows 30 and the second bellows 31. Then, the front power piston 8 and the rear power piston 12 advance due to the differential pressure generated between the front constant pressure chamber 9 and the front variable pressure chamber 10, and between the rear constant pressure chamber 13 and the rear variable pressure chamber 14.

With this, the valve body 24 is advanced with great force,
The thrust is transmitted to the output shaft 21.

Then, when the front power piston 8 advances, the first bellows 30 expands as shown in FIG. 2, and there is no shrinkage margin on the front side of the front power piston 8. Therefore, there is no need to set a gap between the front shell 2 and the front power piston 8 at the time of maximum forward movement, and the front shell 2 is positioned rearward by that amount,
The overall length of the main body 5 can be shortened.

As a result, the tandem brake booster can be downsized in the front-rear direction and can be made lighter by reducing the total length.

In this embodiment, the other end of the first bellows 30 is attached to the nut.
In addition to being fixed to 29, the first bellows 30 maintains the airtightness between the rear transformer chamber 14 and the outside, so that the conventional seal member (31 in FIG. 4) is not required and the number of parts can be reduced. .

(Effect of the invention) As described in detail above, the present invention provides the first bellows and the second bellows in a double structure,
Since the first bellows is located behind the front power piston so that the first bellows expands when the front power piston moves forward, there is a gap between the front shell and the front power piston when moving forward maximally as in the past. There is no need to set a gap in, and the total length of the main body can be shortened accordingly.

Then, by shortening the overall length of the main body, it is possible to reduce the size and weight.

[Brief description of drawings]

FIG. 1 is an overall longitudinal sectional view of a tandem type brake booster according to an embodiment of the present invention, and FIG. 2 shows a state of a bellows at the time of boosting operation of the tandem type brake booster shown in FIG. FIG. 3 is an enlarged vertical cross-sectional view of the main part, FIG. 3 is an overall vertical cross-sectional view showing an example of a conventional tandem brake booster, and FIG. 4 is a boosting operation of the tandem brake booster shown in FIG. FIG. 6 is an enlarged vertical cross-sectional view of a main part showing a state of the bellows at the time. 2 ... Front shell, 3 ... Center shell 4 ... Rear shell, 5 ... Main body 6 ... Center plate, 7, 11 ... Diaphragm 8 ... Front power piston 9 ... Front constant pressure chamber, 10 ... Front transformer chamber 12 ... Rear power piston 13 ... Rear Constant pressure chamber, 14 ... Rear transformer chamber 16 ... Guide rod, 20 ... Valve mechanism 30 ... First bellows, 31 ... Second bellows

Claims (1)

[Claims] 1. A main plate formed by a front shell and a rear shell is divided into a front chamber and a rear chamber by a center plate,
Furthermore, the front chamber is divided into a front constant pressure chamber and a front variable pressure chamber by a front power piston equipped with a diaphragm, and the rear chamber is divided into a rear constant pressure chamber and a rear variable pressure chamber by a rear power piston equipped with a diaphragm. Defined in
A guide rod is extended in the front-rear direction in the main body through the front shell, rear shell and each power piston, and at the same time the atmosphere is introduced into each of the variable pressure chambers by the movement of the input shaft by the valve mechanism, and each power is supplied. In a tandem brake booster that advances a piston along the guide rod to perform a boosting operation, an expandable and retractable first wrapping device that surrounds the outside of the guide rod and maintains airtightness between the front constant pressure chamber and the front variable pressure chamber. One bellows, one end fixed to the front power piston,
The other end is fixedly provided to the rear shell, and further, an expandable telescopic second bellows which connects the front variable pressure chamber and the rear variable pressure chamber and maintains airtightness with the rear constant pressure chamber, and one end thereof is the rear power piston. A tandem brake booster having the other end fixed to the center plate and surrounding the outside of the first bellows.