JP2003182561A - Brake booster - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a piston fixed to a diaphragm from thrusting a master piston in the axial direction with offset loading. <P>SOLUTION: A booster shell is partitioned into a constant pressure chamber and a variable pressure chamber by holding a diaphragm between a front shell and a rear shell, the diaphragm and a plate superimposed on the diaphragm are fixed to the piston, the front shell and the rear shell are joined together with a tie rod extending in parallel to the axis of the booster shell, and a guide fixed to the plate is slidably fitted to the tie rod to form a sealing portion of the diaphragm which fits the tie rod with air-tightness. When atmospheric air flows into the variable pressure chamber with the operation of a valve mechanism, the diaphragm is moved frontward in accordance with a pressure difference between both chambers and the piston is guided by the guide fitting the tie rod and moved frontward to press an output rod via a reaction mechanism and put the master piston forward, thus generating braking hydraulic pressure. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle brake booster.

[0002]

2. Description of the Related Art An outer peripheral edge of a diaphragm is sandwiched between a front shell and a rear shell which form a booster shell to divide the booster shell into a constant pressure chamber and a variable pressure chamber, and the diaphragm and the diaphragm on the constant pressure chamber side. The polymerized plate is fixed to the outer peripheral surface of the tip portion of the piston, and the outer peripheral surface of the piston is supported in a guide hole formed on the axis of the rear shell via a seal member and guided slidably in the axial direction. The piston is provided with a valve mechanism that connects the variable pressure chamber to the atmosphere and the constant pressure chamber so as to communicate with each other, and moves the diaphragm in the front-rear direction based on the pressure difference between the two chambers from the piston to the output rod via a reaction mechanism. Communicate,
Japanese Patent Laid-Open No. 11-43039 discloses a vehicle brake booster in which the output rod pushes a master piston of a master cylinder in an axial direction.

[0003]

In the above-mentioned conventional apparatus, the piston whose tip is fixed to the diaphragm may be tilted with the guide hole provided in the rear shell as a fulcrum. At this time, since the distance between the guide hole that supports the piston and the point of action at which the output rod abuts the master piston is long, a slight inclination of the piston causes a large radial displacement at the tip of the output rod, causing the piston to move to the output rod. The pressing force that acts on the master piston becomes a large unbalanced load and acts on the master piston. This tendency increases as the distance between the guide hole and the point of action increases and the output load increases as the piston moves forward due to the brake operation, and a large unbalanced load may act on the master piston. .

[0004]

In order to solve the above problems, the structural feature of the invention according to claim 1 is that the outer peripheral edge of a diaphragm is sandwiched between a front shell and a rear shell which constitute a booster shell. The booster shell is divided into a constant pressure chamber and a variable pressure chamber, the diaphragm and a plate superposed on the diaphragm on the constant pressure chamber side are fixed to the piston, and the variable pressure chamber is switched to the atmosphere and the constant pressure chamber on the piston. In the brake booster configured to transmit the movement of the diaphragm in the front-rear direction based on the pressure difference between the two chambers from the piston to the output rod through the reaction mechanism, the valve mechanism is provided outside the piston. The front shell and the rear shell are connected by a tie rod extending parallel to the axis of the booster shell, It is that the formation of the seal portion slidably fitted in the axial direction of the guide which is fixed integrally to the tie rod, is fitted while maintaining the tie rod and hermetically to said diaphragm.

A characteristic feature of the invention according to claim 2 is that, in the brake booster according to claim 1, both ends of the guide have a mouth widening shape.

According to a third aspect of the present invention, in the brake booster according to the first or second aspect, a plurality of tie rods are provided, and one tie rod is slidably fitted with the guide. The tie rods fitted with the guides and the tie rods located on the opposite sides of the axis of the booster shell between the tie rods and the tie rods are fitted with long holes having a long diameter in the radial direction, and the other tie rods are fitted with the plate. This means that the insertion hole formed in was loosely fitted.

[0007]

In the invention according to claim 1 configured as described above, the outer peripheral edge of the diaphragm is sandwiched between the front shell and the rear shell which form the booster shell so that the booster shell serves as a constant pressure chamber. It is divided into a transformer room,
A diaphragm and a plate superposed on the diaphragm on the constant pressure chamber side are fixed to a piston, and a front shell and a rear shell are connected by a tie rod extending parallel to the axis of the booster shell, and a guide integrally fixed to the plate is attached to the tie rod. Is fitted slidably in the axial direction, and a seal part is formed on the diaphragm that fits tightly with the tie rod, and when the atmosphere is introduced into the variable pressure chamber by the operation of the valve mechanism, the variable pressure chamber and the constant pressure chamber are separated. The diaphragm is moved forward based on the pressure difference inside the chamber, and the piston is guided by the fitting of the tie rod and the guide integrally fixed to the plate and moved forward to push the output rod through the reaction mechanism. It moves to move the master piston of the master cylinder forward to generate brake hydraulic pressure. When the negative pressure of the constant pressure chamber is introduced into the variable pressure chamber by the operation of the valve mechanism and the pressure difference between the two chambers disappears, the diaphragm is moved backward by the spring force, and the piston is guided by the fitting of the guide and the tie rod to the rear. Smoothly moves to release the master piston.

As described above, according to the first aspect of the invention, since the guide fixed to the plate is fitted to the tie rod connecting the front shell and the rear shell, the piston is surely guided so as to be slidable in the axial direction. Even if the piston does not tilt and even if it is tilted by a small amount, the distance between the fitting part where the guide fits on the tie rod and the point of action where the output rod contacts the master piston is short, so the displacement of the tip of the output rod Becomes smaller, and the unbalanced load acting on the master piston can be made extremely small. Further, since the tie rod that connects the front shell and the rear shell is also used for guiding the piston, the structure is simplified and a low-cost brake booster can be provided.

In the invention according to claim 2 configured as described above, since the both ends of the guide have a mouth-spreading shape, the guide does not bite the tie rod at the end, and the piston smoothly moves in the axial direction. You can be sure to guide.

In the invention according to claim 3 configured as described above, one of the plurality of tie rods is fitted to the guide, and the tie rod fitted to the guide and the opposite side of the booster shell are sandwiched therebetween. Since the tie rod located at is fitted in the long hole having a long diameter in the radial direction formed in the plate, and the other tie rods are loosely fitted in the insertion holes formed in the plate,
The piston is guided by one tie rod while being prevented from turning, and is guided in the axial direction with high accuracy and reliably without interfering with other tie rods.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a brake booster according to the present invention will be described below with reference to the drawings. As shown in FIG. 1, the booster shell 1 is composed of a front shell 2 and a rear shell 3, and a flexible diaphragm 4 is hermetically sandwiched between the shells 2 and 3 by a bead on the outer peripheral edge of the booster shell 1. The interior of 1 is divided into a constant pressure chamber 5 and a variable pressure chamber 6. A disk-shaped plate 7 is superposed on the diaphragm 4 on the side of the constant pressure chamber 5, and the outer peripheral surface of the tip portion of the piston 8 is airtightly fixed to the diaphragm 4 and the plate 7, and the front side portion of the piston 8 is exposed to the constant pressure chamber 5. is doing. The center portion of the rear shell 3 is bent outward, a cylindrical protruding portion 3a is provided so as to project rearward, and a through hole 3b is formed on the axis. The piston 8 penetrates through the through hole 3b and projects rearward from the projecting portion 3a of the booster shell 1, and a seal member 21 is interposed between the inner peripheral surface of the through hole 3b and the outer peripheral surface of the piston 8 to transform the transformation chamber. 6 is cut off from the atmosphere.
A bellows 23 is fixed between the rear end edge of the piston 8 and the peripheral edge of the through hole 3b, and covers the outer circumference of the piston 8. A negative pressure introducing pipe 9 is attached to the front shell 2, and the constant pressure chamber 5 is connected to the intake manifold of the engine through the negative pressure introducing pipe 9 and is maintained at a negative pressure.

Reference numeral 10 denotes a master cylinder, a tip portion 10a of which penetrates a central hole formed in the front shell 2 and projects in an airtight manner into the constant pressure chamber 5, and a flange portion 10b is in contact with a rear surface of the front shell 2. . The front shell 2 and the rear shell 3 are booster shells 1 composed of both shells.
Is fixed to the master cylinder 10 by being joined by a plurality of, for example, four tie rods 11 extending in parallel with the axis at an approximately intermediate position between the axis and the outer circumference. That is, the tie rod 11
Is attached to the inner surface of the rear shell 3 in the variable pressure chamber 6 in an airtight manner, and the rear end portion that extends through the rear shell 3 and extends rearward is caulked toward the outer surface of the rear shell 3. Is connected to the rear shell 3. Tie rod 11
In the small diameter portion 11b formed at the tip of the small diameter portion 11b, the dish-shaped washer 12 having elasticity fitted in the small diameter portion 11b contacts the shoulder portion of the small diameter portion 11b and the inner surface of the front shell 2 in the constant pressure chamber 5, A seal 13 tightly fitted to the small-diameter portion 11b is pressed against the inner surface of the front shell 2 by a washer 12 to hermetically penetrate the front shell 2 and project forward. The small-diameter portion 11b penetrates a mounting hole 10c formed in the flange portion 10b of the master cylinder 10 and tightens a nut 14 that is screwed into a male screw 11c engraved at the tip of the master cylinder 10. The booster shell 1 is fixed to the master cylinder 10 by sandwiching the flange portion 10b and the flange portion 10b, and the front shell 2 and the rear shell 3 are attracted to each other and coupled.

As shown in FIGS. 1 and 2, each tie rod 11
The sliding holes of the seal portions 4a provided on the diaphragm 4 are slidably fitted to each other while keeping airtightness, and an airtight section between the constant pressure chamber 5 and the variable pressure chamber 6 is maintained. A cylindrical guide 15 is slidably fitted in the front-rear direction on one tie rod 11g that also serves as a guide for the plate 7, and the guide 15 is fitted into a fixing hole formed in the plate 7 to fit the fitting portion. And is fixed to the plate 7 integrally.
Both ends of the guide 15 have a mouth-wide shape that is smoothly curved outward, and prevent the guide 15 from biting the outer peripheral surface of the tie rod 11g. The tie rod 11g also serving as a guide and the tie rod 11 located on the opposite side of the axis of the booster shell 1 are fitted with a long hole 7a formed in the plate 7 and having a long diameter in the radial direction. The plate 7 also serves as a guide. It prevents turning around 11g. The other tie rod 11 is loosely fitted with an insertion hole 7b formed in the plate 7.

Reference numeral 16 denotes a master piston which penetrates the front shell 2 in an airtight manner and is fitted in the master cylinder 10 so as to be slidable in the front-rear direction.
It projects into the constant pressure chamber 5 from a and extends to the vicinity of the front end face of the piston 8. An output rod 17 is interposed between the piston 8 and the master piston 16, and the piston 8 serves as a diaphragm 4 based on the pressure difference between the constant pressure chamber 5 and the variable pressure chamber 6.
Of the forward movement of the output rod 17 to the master piston 16
It is designed to be transmitted via. That is, the master piston 16 is provided with a connecting hole 16a in the axial direction from the rear end face, and the bottom of the connecting hole 16a is formed in a conical shape with a rounded top. The tip of a rod portion 17a projecting forward of the output rod 17 is aligned with the conical bottom portion of the connecting hole 16a and abutted on the rear end of the output rod 17 so as to be relatively bendable in the axial direction. The formed annular projection 17b has an annular groove 8 formed in the piston 8 from the front end surface toward the rear.
It is fitted in a so as to be relatively movable in the axial direction. A return spring 20 is interposed between the front shell 2 and the front end surface of the piston 8 to bias the piston 8 rearward.

A reaction mechanism 2 for generating a pressure difference in both chambers 5 and 6 in accordance with the pedaling force applied to the brake pedal 21 and feeding back the relative movement of the diaphragm 4 and thus the piston 8 with respect to the output rod 17 based on this pressure difference.
2 is a disc-shaped reaction force member 1 formed of an elastic material in a reaction force chamber 17c surrounded by an annular projection 17b of the output rod 17.
8 is stored, and the reaction force member 18 is the annular groove 8 of the piston 8.
It is sandwiched between the reaction force end surface 8b surrounded by a and the bottom surface of the reaction force chamber 17c, and the piston 8 is compressed and deformed according to the force pressing the output rod 17 and the master piston 16. There is. An annular spring body 19 is sandwiched between the return spring 20 and the front end surface of the piston 8, and the spring body 19 abuts against the rear surface of the annular projection 17b portion to form the annular projection 1.
7b is prevented from slipping out of the annular groove 8a.

Reference numeral 24 is a valve mechanism for switching the variable pressure chamber 6 to the atmosphere and the constant pressure chamber 5 for communication, and is incorporated in the piston 8. An annular control valve body 25 is slidably fitted in a valve hole 8c provided in the central portion of the piston 8 in the axial direction. An annular negative pressure valve opening / closing portion 25a provided at the tip of the control valve body 25 is in contact with a negative pressure valve 8d provided in an annular shape at the bottom of the valve hole 8c so as to be able to come into contact with and separate from it. The recess formed inside the negative pressure valve 8d is a passage 8e that is formed in the piston 8 in the radial direction and opens to the outer peripheral surface of the piston 8 in front of the seal 9.
Is connected to the transformer room 6. The piston 8 is provided on the outer peripheral side of the negative pressure valve 8d where it is joined to the negative pressure valve opening / closing portion 25a.
A negative pressure is introduced into the variable pressure chamber 6 when the communication passage 8f opening at the front end face of the negative pressure valve opening / closing part 25a is opened from the negative pressure valve 8d. An atmospheric valve body 26 is movably inserted in the center hole of the control valve body 25 in the front-rear direction, and a tip shaft 26a protruding from the tip of the atmospheric valve body 26 is connected to the negative pressure valve 8d.
Is fitted in a through hole opened from the bottom surface of the recess formed in the inside of the recess and opened to the reaction force end face 8b, and faces the reaction force member 18 with a slight gap. A stop member 27 is inserted into a passage 8e formed in the radial direction of the piston 8 so as to be movable in the front-rear direction by a predetermined amount.
It engages with the annular groove 26b formed in a so as to be relatively movable in the axial direction by a predetermined amount, and connects the atmospheric valve body 26 and the piston 8 so as to be relatively movable in the front-rear direction within a predetermined range. The stop member 27 is provided so as to project radially outward from the outer peripheral surface of the piston 8, and when the piston 8 is moved rearward by the spring force of the return spring 20, the communication hole 3 of the rear shell 3 is formed.
The piston 8 and the atmospheric valve body 26 are restricted from moving rearward by contacting the peripheral edge of b.

The control valve body 25 is provided with an atmosphere valve opening / closing portion 25b at a position rearward of the negative pressure valve opening / closing portion 25a.
When the atmospheric valve opening / closing portion 25b is separated from the atmospheric valve 26c, the atmospheric air enters the center hole of the control valve body 25 and the inside of the negative pressure valve 8d. The gas is introduced into the variable pressure chamber 6 through the formed recess and the passage 8e formed in the piston 8 in the radial direction. Control valve body 2
The rear end of the valve 5 is connected to an annular seal holder 32 by a bellows 25c that allows the control valve element 25 to move in the axial direction. The seal holder 32 is connected to an inlet hole 8g extending from the valve hole 8c to the rear end surface of the piston 8. It is fitted and pressed against the shoulder portion of the valve hole 8c by the compression spring 28. An input rod 29 connected to the brake pedal 21 is connected to the atmosphere valve body 26 inside the atmosphere valve 26c through the inlet hole 8g.
The compression spring 28 is interposed between the rear end surface of the seal holder 32 and a spring bearing 30 that abuts on the shoulder portion of the input rod 29. The front end face of the seal holder 32 and the control valve body 25
A compression spring 31 is interposed between the rear end surface and the rear end face and biases the control valve body 25 forward to bring the negative pressure valve opening / closing portion 25a and the atmospheric valve opening / closing portion 25b into contact with the negative pressure valve 8d and the atmospheric valve 26c, respectively. I am letting you. An air filter 33 through which the input rod 29 penetrates in an airtight manner is fixed to the opening of the inlet hole 8g.

Next, the operation of the brake booster according to the above embodiment will be described. When the brake pedal 21 is stepped on and the atmospheric valve body 26 is advanced through the input rod 29 against the spring force of the compression spring 28 with respect to the piston 8, the atmospheric valve 26c causes the atmospheric valve 26c to become an atmospheric valve of the control valve body 25. Opening / closing part 2
The atmosphere separated from 5b and filtered by the air filter 33 flows into the variable pressure chamber 6 through the passage 8e. The diaphragm 4, the plate 7, and the piston 8 are moved forward due to the pressure difference between the variable pressure chamber 6 and the low pressure chamber 5, and the output rod 17
Is advanced by the piston 8 via the reaction force member 18 of the reaction mechanism 22, the master piston 16 is pushed by the output rod 17, and brake hydraulic pressure according to the pedaling force of the brake pedal 21 is generated in the master cylinder 10. At this time, the guide 15 fixed to the plate 7 is the output rod 1
7 is fitted to the tie rod 11g that also serves as a guide at a position close to the point of contact with the master piston 16, and is smoothly guided in the axial direction.
Does not tilt as the input rod 29 tilts, is guided with high accuracy in the axial direction, and does not press the master piston 16 in the axial direction with an unbalanced load.

The piston 8 elastically deforms the reaction member 18 by an operating force corresponding to the pressure difference between the chambers 5 and 6 acting on the diaphragm 4, and the master piston 16 via the output rod 17
The control valve body 25 is urged forward by the compression springs 28 and 31 and moves forward together with the piston 8 while pushing forward, and moves forward relative to the atmosphere valve body 26. When the piston 8 presses the output rod 17 with power, the atmosphere valve opening / closing portion 25b causes the atmosphere valve 2 to move.
By contacting 6c, the communication between the atmosphere and the variable pressure chamber 6 is cut off, and a desired brake hydraulic pressure is maintained. At this time, the force applied to the brake pedal 21 is applied to the atmosphere valve body 26 via the input rod 29.
The reaction force member 18 is transmitted from the tip end shaft 26a of the vehicle to the reaction force member 18, and the reaction force member 18 is elastically deformed according to the pedaling force, so that the driver can feel the reaction force.

When the brake pedal 21 is released, the atmospheric valve body 26 is moved rearward with respect to the piston 8 by the spring force of the compression spring 28, and the atmospheric valve 26c presses the atmospheric valve opening / closing portion 25b to control the valve body. 25 is a compression spring 31
The negative pressure valve opening / closing portion 25a is separated from the negative pressure valve 8d by being moved rearward relative to the piston 8 against the spring force of. As a result, the negative pressure in the constant pressure chamber 5 is reduced to the communication passage 8f and the passage 8
It is introduced into the variable pressure chamber 6 through e, the pressure difference between the variable pressure chamber 6 and the constant pressure chamber 5 disappears, and the piston 8, the plate 7 and the diaphragm 4 are moved rearward by the spring force of the return spring 20, and the master piston 16 is moved rearward by the spring force of the compression spring 34 for returning to the original position, and the hydraulic pressure in the master cylinder 10 is lost. Atmospheric valve body 2
6 is stopped at the same time when the stop member 27 comes into contact with the peripheral edge of the communication hole 3b of the rear shell 3 and stops, and the piston 8 moves slightly rearward after the stop member 27 stops and comes into contact with the stop member 27 and stops. . As a result, the negative pressure valve 8d comes into contact with the negative pressure opening / closing portion 25a, and the communication between the constant pressure chamber 5 and the variable pressure chamber 6 is cut off. At this time, the guide 15 fixed to the plate 7 fits with the tie rod 11g and is smoothly guided in the axial direction. Therefore, the piston 8 fixed to the plate 7 does not tilt as the input rod 29 tilts, and the piston 8 fixed in the axial direction. Guided with high accuracy and smoothly move backward.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of a brake booster according to the present invention.

FIG. 2 is a partial cross-sectional view taken along the line 2-2 of FIG. 1
... Booster shell, 2 ... Front shell, 3 ...
..Rear shell, 3b ... Through hole, 4 ... Diaphragm, 5 ... Constant pressure chamber, 6 ... Transformer chamber, 7 ... Plate, 8 ... Piston, 8c ... Valve hole, 8d ...
Negative pressure valve, 8e ... passage, 8f ... communication passage, 9 ...
Negative pressure introducing pipe, 10 ... Master cylinder, 11 ... Tie rod, 15 ... Guide, 16 ... Master piston, 17 ... Output rod, 18 ... Reaction force member, 20
... Return spring, 21 ... Brake pedal, 22 ... Reaction mechanism, 24 ... Valve mechanism,
25 ... Control valve body, 25a ... Negative pressure valve opening / closing part, 25
b ... atmosphere valve opening / closing part, 26 ... atmosphere valve body, 26a ...
.... Tip shaft, 26c ... Atmospheric valve, 27 ... Stop member, 28, 31 ... Compression spring, 29 ... Input rod.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tomoo Ogura             2-1, Asahi-cho, Kariya City, Aichi Stock Association             Company Advics F term (reference) 3D048 BB51 CC26 EE02 EE03 EE12                       EE20 EE28

Claims (3)

[Claims] 1. A booster shell is divided between a constant pressure chamber and a variable pressure chamber by sandwiching an outer peripheral edge of a diaphragm between a front shell and a rear shell constituting a booster shell, and the diaphragm and the diaphragm are provided on the constant pressure chamber side. The polymerized plate is fixed to the piston, and the piston is provided with a valve mechanism that connects the variable pressure chamber to the atmosphere and the constant pressure chamber so as to communicate with each other. In the brake booster adapted to be transmitted from the output rod to the output rod via a reaction mechanism, the front shell and the rear shell are coupled by a tie rod extending outside the piston in parallel to the axis of the booster shell, A guide integrally fixed to the plate is fitted onto the tie rod so as to be slidable in the axial direction, and A brake booster, wherein a seal portion is formed on the earflam so as to be fitted to the tie rod in an airtight manner. 2. The brake booster according to claim 1, wherein both ends of the guide have a mouth widening shape. 3. A plurality of the tie rods are provided, the guides are slidably fitted to one tie rod, and the tie rods on which the guides are fitted are located on opposite sides of the axis line of the booster shell. The brake according to claim 1 or 2, wherein a long hole having a long diameter in a radial direction formed in the plate is fitted, and an insertion hole formed in the plate is loosely fitted in another tie rod. Booster.