JP2545954B2 - Brake booster - Google Patents

Description

TECHNICAL FIELD The present invention relates to a brake booster including a constant pressure chamber and a variable pressure chamber inside a shell.

`` Prior art '' A brake booster usually forms a pair of constant pressure chambers and a variable pressure chamber before and after a power piston and a diaphragm in a shell, and these are formed when the brake pedal is released and the non-operating state. A negative pressure is introduced into the constant pressure chamber and the variable pressure chamber.

Then, when the brake pedal is depressed, the negative pressure is introduced into the constant pressure chamber and the atmospheric pressure is introduced into the variable pressure chamber according to the pedaling force of the brake pedal to generate a fluid pressure difference before and after the power piston. The power piston and the push rod interlocked with the power piston are moved forward, and the piston of the master cylinder is moved forward by the forward movement of the push rod to generate brake hydraulic pressure.

By the way, in this type of brake booster, the output can be increased by increasing the effective pressure receiving area of the power piston, but if the diameter of the power piston is increased for that reason, the diameter of the brake booster also increases. Depending on the vehicle, it may not be mounted.

Therefore, conventionally, there has been proposed a tandem brake booster in which two pairs of a constant pressure chamber and a variable pressure chamber are arranged in series in the shell (Japanese Patent Publication No. 44-9770 and Japanese Patent Publication No. 53-2391).
3 and JP-A-60-154952).

According to the tandem brake booster described above, the output can be increased without increasing the diameter even when the brake booster is axially elongated, so that the tandem brake booster is also mounted on a vehicle in which a brake booster having a large diameter cannot be mounted. It becomes possible.

[Problems to be Solved by the Invention] However, when the output of the tandem brake booster is further increased, the diameter cannot be avoided, and the tandem brake booster is configured to have a diameter larger than that of the tandem brake booster. There was a vehicle that could not be mounted because the diameter was too large even if the increase in the number was suppressed.

In order to improve such a drawback, a triple type brake booster in which three pairs of a constant pressure chamber and a variable pressure chamber are arranged in series in the shell may be configured.

That is, a front plate and a rear plate that are arranged and fixed in the shell and divide the inside of the shell into a front chamber, a center chamber, and a rear chamber, and a valve body that is slidably penetrated through the front plate and the rear plate. And a front power piston, a center power piston and a rear power piston which are respectively arranged in the front chamber, the center chamber and the rear chamber and which are connected to the valve body, and each of the front power piston, the center power piston and the rear power piston. A front diaphragm, a center diaphragm, and a rear diaphragm that are stretched on the side surface and divide the front chamber, the center chamber, and the rear chamber into a constant pressure chamber on the front side and a variable pressure chamber on the rear chamber,
A constant pressure passage communicating between the constant pressure chambers formed in the front chamber, the center chamber and the rear chamber, a variable pressure passage communicating between the variable pressure chambers formed in the front chamber, the center chamber and the rear chamber, and the valve body. A valve mechanism that is housed inside and that switches the communication state between the constant pressure passage, the variable pressure passage, and the pressure passage that supplies pressure fluid; and the valve mechanism that communicates with the brake pedal and is moved forward and backward. It suffices to configure a brake booster having an input shaft for switching between.

According to the brake booster having such a configuration, the front pressure piston, the center power piston, and the rear power piston are divided into a constant pressure chamber and a variable pressure chamber, respectively. Therefore, compared with the tandem brake booster, Since the total effective pressure receiving area can be increased without increasing the diameter, and therefore the required large output can be obtained even if the outer diameter of the brake booster is reduced, a brake booster with a large diameter can be used. The possibility of mounting on a vehicle that cannot be mounted can be increased.

However, in the above-described triple type brake booster, pressure fluid is introduced into the variable pressure chamber of the rear chamber via the valve mechanism during its operation, and further, from the variable pressure chamber of the rear chamber via the variable pressure passage formed in the valve body. When the pressure fluid is introduced into the variable pressure chambers of the center chamber and the front chamber, the distance between the front chamber and the rear chamber becomes large and the length of the variable pressure passage formed in the axial direction of the valve body becomes long. .

Therefore, in particular, when the pressure fluid supplied to the variable pressure chamber of the front chamber is released to the variable pressure chamber of the rear chamber through the variable pressure passage, the pressure fluid may not be discharged smoothly, which causes a delay in releasing the brake operation. There was a risk of this.

[Means for Solving the Problem] In view of such circumstances, the present invention adopts the configuration of the triple type brake booster described above, and further, the variable pressure passage is further connected to the variable pressure chamber of the center chamber and the valve. A first variable pressure passage communicating with the mechanism, a second variable pressure passage communicating with the variable pressure chamber of the front chamber and the valve mechanism, and a third variable pressure passage communicating with the variable pressure chamber of the rear chamber with the valve mechanism. In addition, the flow path length of the first variable pressure passage is made shorter than the other variable pressure passages.

[Operation] According to the above configuration, the variable pressure chamber of the center chamber communicates with the valve mechanism at the shortest distance via the first variable pressure passage, and the variable pressure chamber of the center chamber is divided into the variable pressure chamber of the front chamber and the variable pressure chamber of the rear chamber. Since the variable pressure chamber of the room is located in the middle, the passage lengths of the first variable pressure passage and the third variable pressure passage can be distributed almost evenly, and as a result, each variable pressure passage has the shortest path length. Then, the valve mechanism and each variable pressure chamber are brought into communication with each other.

Therefore, when the pressure fluid supplied to each variable pressure chamber is allowed to escape through the variable pressure passages, the pressure fluid in each variable pressure chamber can be quickly discharged, thereby delaying the operation when releasing the brake operation. It can be well prevented.

[Examples] Hereinafter, the present invention will be described with reference to the illustrated examples. In the drawings, a shell 1 of a brake booster includes a stepped cup-shaped front shell 2 and a schematic dish-like shape for sealing an opening of the front shell 2. The stepped cup-shaped front shell 2 is formed by gradually increasing the diameter from the bottom side to the opening side in a stepwise manner.
2A, a medium diameter portion 2B and a large diameter portion 2C are sequentially formed, and a large diameter cylindrical hooking portion 2D is formed on the opening side of the large diameter portion 2C.

A front plate 5 formed in a stepped cup shape is fitted inside the front shell 2, and a front chamber 6 is defined between an end wall surface of the front plate 5 and an end wall surface of the front shell 2. Has formed.

The front plate 5 includes a tubular portion 5A tightly fitted in the middle diameter portion 2B of the front shell 2 and a flange portion 5B formed at the right end of the tubular portion 5A and extending outward in the radial direction. , The flange portion 5B is the middle diameter portion of the front shell 2.
The front plate 5 is positioned with respect to the front shell 2 by being superposed on the position of the step end surface 2a of 2B.

A rear plate 7 formed in a cup shape is further fitted into the front plate 5, and a center room 8 is defined between an end wall surface of the rear plate 7 and an end wall surface of the front plate 5. Has formed. The cup-shaped rear plate 7 is provided with a tubular portion 7A tightly fitted in the large diameter portion 2C of the front shell 2, and a flange extending outward in the radial direction formed on the right end of the tubular portion 7A. The rear plate 7 is positioned with respect to the front shell 2 by superimposing the portion 7B on the stepped end surface 2b formed between the large diameter portion 2C of the front shell and the cylindrical hooking portion 2D.

Further, the rear shell 3 has a flange portion 3A extending radially outward on the outer peripheral portion thereof.
Is fitted into the cylindrical hooking portion 2D of the front shell 2 and overlapped with the flange portion 7B of the rear plate 7 so that the wall surface of the rear shell 3 and the end wall surface of the rear plate 7 are A rear chamber 9 is formed.

Then, in this state, a part of the cylindrical hooking portion 2D is curved inward in the radial direction to form a plurality of engaging claws 2c, whereby the front shell 2, the front plate 5, the rear plate 7, and The rear shells 3 are integrally connected to each other.

Next, a large diameter portion 12A, a medium diameter portion 12B and a small diameter portion 12C are sequentially formed from the front side to the rear side on the outer periphery of the valve body 12 slidably provided on the shaft portion in the shell 1.
The outer peripheral portions of the plates 5 and 7 and the rear shell 3 are passed through through holes formed at the central positions of the shaft portions, and a seal member 13 holds airtightness between the through holes and the valve body 12, respectively. .

A front power piston 14, a center power piston 15 and a rear power piston 16 are arranged in the front chamber 6, the center chamber 8 and the rear chamber 9, respectively, and the power pistons 14 to 16 are arranged in the valve body 12. Front diaphragm 17, center diaphragm 18, and rear diaphragm 19 are connected to the rear side surfaces of the power pistons 14 to 16, respectively, and the constant pressure chambers located inside the chambers 6, 8 and 9 are located on the front side. It is divided into A, C, and E, and transformer rooms B, D, and F located on the rear side.

However, in the axial direction within the shaft portion of the valve body 12,
Constant pressure chamber A of the front chamber 6 and constant pressure chamber C of the center chamber 8
And a constant pressure chamber 21 in the rear chamber 9 and a constant pressure chamber 21 in the rear chamber 9 are formed.

The right end of the constant pressure passage 20 is the large diameter portion of the valve body 12.
An annular groove 1 formed on the end face 12a of the step portion between 12A and the intermediate diameter portion 12B
2b, and the stepped cylindrical portion 15 protruding toward the front side from the shaft portion of the center power piston 15 described above.
a and the small diameter portion at the tip of the stepped cylindrical portion 15a is formed into the annular groove 12
At the same time as fitting on the inner peripheral surface of b, the bottom of the annular groove 12b is abutted and positioned.

Therefore, the constant pressure passage 20 communicates with the annular groove 12b on the outer peripheral side of the stepped tubular portion 15a, and the valve body 12
Is constantly communicated with the constant pressure chamber C of the center chamber 8 through a gap δ formed between the step end surface 12a of the above and the center power piston 15. Incidentally, on the outer peripheral surface of the annular groove 12b,
Reinforcing ribs 12c extending in the axial direction are formed at predetermined intervals.

Further, the inner peripheral bead portion 18a of the center diaphragm 18 is fitted inside the stepped tubular portion 15a to prevent the constant pressure passage 20 from communicating with the variable pressure chamber D by the inner peripheral bead portion 18a. There is. The inner peripheral bead portion 18a prevents the inner peripheral bead portion 18a from falling out of the stepped cylindrical portion 15a by the retainer 22 fitted on the outer periphery of the valve body 12.

The right end of the other constant pressure passage 21 is also configured to be substantially the same as the right end of the constant pressure passage 20. According to this configuration, the axial dimension of the valve body 12 can be shortened.

That is, as is well known in the art, when a radial hole corresponding to the gap δ is opened in the same diameter portion of the valve body 12 and the center power piston 15 is connected to the rear side of the opening of the hole, Since the valve body 12 receives the forward force from the center power piston 15, the valve body on the rear side of the hole needs to have a thickness sufficient to obtain sufficient strength.

On the other hand, according to the above configuration, the gap δ between the step end surface 12a and the center power piston 15 corresponds to a conventional hole, and the rear side of the hole does not require a wall thickness. The axial dimension of the valve body can be shortened. And the center power piston 15 is
Since it is connected to the small diameter part of the valve body on the rear side of the stepped end face 12a, the strength of the connected part can be sufficiently ensured.

Particularly, as in this embodiment, if the center power piston 15 is connected to the valve body 12 in the annular groove 12b formed in the step end surface 12a, the connecting portion and the stroke portion of the seal member 13 overlap each other. Therefore, it can be further shortened.

Next, a conventionally well-known valve mechanism 23 is housed in the valve body 12, and the valve mechanism 23 has a ring-shaped first valve seat 24 formed in the valve body 12 and a ring-shaped first valve seat 24. An annular second valve seat 26 formed at the right end of a valve plunger 25 slidably provided inside the valve body 12, and a valve body seated on both valve seats 24, 26 from the right by a spring 27.
28 and.

The space on the outer peripheral side of the annular seat portion where the first valve seat 24 and the valve body 28 come into contact with each other is controlled by the constant pressure chamber A and the rear chamber 9 of the front chamber 6 via the second constant pressure passage 21 formed in the valve body 12. Of the constant pressure chamber E, and the constant pressure chamber A is communicated with a negative pressure source such as an intake manifold (not shown) via a negative pressure introducing pipe 32 attached to the front shell 2. The negative pressure introduced into the constant pressure chamber A is always introduced into the constant pressure chamber C of the center chamber 8 and the variable pressure chamber E of the rear chamber 9 through the constant pressure passages 20 and 21.

Further, the inner peripheral side of the annular seat portion where the first valve seat 24 and the valve body 28 contact each other, and the outer peripheral side portion of the annular seat portion where the second valve seat 26 and the valve body 28 contact each other, that is, both annular shapes. The space of the intermediate portion of the seat portion is communicated with the variable pressure chamber D of the center chamber 8 through the first variable pressure passage 33 formed in the valve body 12 in the radial direction. The axial second variable pressure passage 34 communicating with the variable pressure chamber B of the front chamber 6 and the variable pressure chamber F of the rear chamber 9
The third variable pressure passage 35 in the axial direction that communicates with the valve mechanism 23 is in communication with each other via the first variable pressure passage 33.

Therefore, the respective variable pressure chambers B, D, F communicate with each other through the three variable pressure passages 33 to 35, and the first variable pressure passage 33 communicating with the central variable pressure chamber D has the shortest path length. Since the variable pressure passages 34 and 35 communicating with the variable pressure chambers B and F on both sides are divided into the left and right with the first variable pressure passage 33 as the center, they are approximately equidistant. In other words, the variable pressure passages 33 to 35 allow the valve mechanism 23 and the variable pressure chambers B, D and F to communicate with each other with the shortest passage length.

As a result, for example, the variable pressure passage that connects the rear side variable pressure chamber F and the valve mechanism 23 is set to the shortest distance, and the variable pressure chamber F, the variable pressure chamber B on the front side, and the variable pressure chamber D at the center are respectively changed by the variable pressure passages. In the case of connection, the passage length between the front-side variable pressure chamber B and the rear-side variable pressure chamber F becomes long, but with the above-mentioned configuration, the passage length is substantially halved. Therefore, it is possible to reduce the flow path resistance.

Further, the space on the inner peripheral side of the annular seat portion where the second valve seat 26 and the valve body 28 are in contact with each other is communicated with the atmosphere via the axial pressure passage 36 and the filter 37.

Next, the right end of the valve plunger 25 slidably provided on the valve body 12 is connected to an input shaft 38 which is interlocked with a brake pedal (not shown), and the left end thereof is formed at the base of the push rod 39. It faces the right end face of the reaction disc 40 housed in the recess 39a. The left end portion of the push rod 39 is slidably projected to the outside from the shaft portion of the front shell 2 through a seal member 41 so as to interlock with the piston of a master cylinder (not shown). Are normally held in the inoperative position shown.

The key member 43 for preventing the valve plunger 25 from falling off the valve body 12 is provided so as to be displaceable in the axial direction of the valve body 12, and both ends thereof are provided.
Of the brake booster and comes into contact with the rear plate 7 when the brake booster is inactive. In this state, the key member 43 restricts the free retreat of the valve plunger 25 with respect to the valve body 12, and causes the flow passage of the valve mechanism 23 to be immediately switched when the brake pedal is depressed and the input shaft 38 is moved leftward, The loss stroke of the input shaft 38 can be reduced.

If the key member 43 is brought into contact with the rear plate 7 inside the shell 1, even if the key member 43 comes into contact with the rear plate 7 and a tapping sound is generated, the key member 43 is transmitted to the outside of the shell 1. It is possible to reduce the tapping sound.

In the above configuration, in the non-actuated state in which the brake pedal is not depressed, the return spring 42 holds the valve body 12 at the rightward retracted end position,
The key member 43 is brought into contact with the rear plate 7 and stopped. The key member 43 advances the valve plunger 25 engaged with the key member 43 relative to the valve body 12, and immediately when the brake pedal is depressed and the input shaft 25 is moved leftward as described above. The flow path of the valve mechanism 23 is switched.

In the non-operating state, the valve body 28 is seated on the second valve seat 26 provided on the valve plunger 25 to close the pressure passage 36 communicating with the atmosphere, and the valve body 28 slightly moves from the first valve seat 24. Since they are separated from each other, the variable pressure passages 33 to 35 communicate with the constant pressure passage 21 and the negative pressure is introduced into all the chambers A to F in the shell 1.

When the brake pedal is depressed from this state and the input shaft 25 is moved leftward, the valve body 28 immediately seats on the first valve seat 24, and the valve body 28 and the second valve seat 26 are separated. The constant pressure passage 21 and the variable pressure passages 33 to 35 are cut off from each other so that the constant pressure chambers A, C and E and the variable pressure chambers B, D and F are cut off from each other, and the variable pressure chambers B, D and F are cut off from each other. Atmosphere is introduced inside.

As a result, the constant pressure chambers A, C, E and the variable pressure chambers B, D,
When a pressure difference occurs between F, the power pistons 14 to 16 and the valve body 12 and the like are integrally moved to the left to move the push rod 39 forward to generate brake fluid pressure in a master cylinder (not shown) to perform brake operation. Let

Further, when the depression force of the brake pedal is released from the brake operating state, the flow path of the valve mechanism 23 is switched, the communication between the variable pressure chambers B, D and F and the atmosphere is interrupted, and the variable pressure chambers B and D are released. , F are communicated with the constant pressure chambers A, C, E, the atmosphere in each of the variable pressure chambers B, D, F escapes to the negative pressure source (not shown) via the constant pressure chamber A.

At this time, since the variable pressure passages 33 to 35 communicate the valve mechanism 23 and the variable pressure chambers B, D, and F with the shortest passage length, the atmosphere in each variable pressure chamber can quickly escape to the outside. Therefore, a delay in deactivating the brake booster can be prevented.

[Advantages of the Invention] As described above, according to the present invention, it is possible to make the valve mechanism and each of the variable pressure chambers communicate with each other by the variable pressure passages having the shortest passage lengths. When letting the supplied pressure fluid escape through each variable passage,
It is possible to quickly discharge the pressure fluid from each of the variable pressure chambers, and thus it is possible to satisfactorily prevent an operation delay when the brake operation is released.

[Brief description of drawings]

 FIG. 1 is a sectional view showing an embodiment of the present invention. 1 ... Shell, 5 ... Front plate 6 ... Front chamber, 7 ... Rear plate 8 ... Center chamber, 9 ... Rear chamber 12 ... Valve body 14 ... Front power piston 15 ... Center power piston 16 ... … Rear power piston 17 …… Front diaphragm 18 …… Center diaphragm 19 …… Rear diaphragm 20 …… First constant pressure passage, 21 …… Second constant pressure passage 23 …… Valve mechanism, 33 …… First variable passage 34 …… 2nd variable pressure passage, 35 ...... 3rd variable pressure passage 36 ...... Pressure passage, 38 ...... Input shaft A, C, E ... Constant pressure chamber, B, D, F ... Variable pressure chamber

Claims (1)

(57) [Claims] 1. A front plate and a rear plate fixed to and fixed in a shell to divide the shell into a front chamber, a center chamber and a rear chamber, and a front plate and a rear plate slidably pierced through the shell. The installed valve body, the front power piston, the center power piston and the rear power piston, which are respectively arranged in the front chamber, the center chamber and the rear chamber and connected to the valve body, and the front power piston, the center power piston and the rear power piston. A front diaphragm, a center diaphragm and a rear diaphragm which are stretched on the respective rear side surfaces and partition the front chamber, the center chamber and the rear chamber into a constant pressure chamber on the front side and a variable pressure chamber on the rear side,
A constant pressure passage communicating between the constant pressure chambers formed in the front chamber, the center chamber and the rear chamber, a variable pressure passage communicating between the variable pressure chambers formed in the front chamber, the center chamber and the rear chamber, and the valve body. A valve mechanism that is housed inside and that switches the communication state between the constant pressure passage, the variable pressure passage, and the pressure passage that supplies pressure fluid, and is moved forward and backward in conjunction with the brake pedal, and the flow passage of the valve mechanism according to the operation. And a second variable pressure passage that connects the variable pressure chamber of the center room with the valve mechanism and a second variable pressure passage that allows the variable pressure chamber of the front room to communicate with the valve mechanism. And a third variable pressure passage communicating the variable pressure chamber of the rear chamber with the valve mechanism, and the flow path length of the first variable pressure passage is set shorter than other variable pressure passages. Brake booster.