WO2003023248A1

WO2003023248A1 - Apparatus for adjusting gap between brake pads and wheel drum in vehicles

Info

Publication number: WO2003023248A1
Application number: PCT/KR2001/001532
Authority: WO
Inventors: Jung-Keun Kong
Original assignee: J/K Enterprise Co., Ltd
Priority date: 2001-09-11
Filing date: 2001-09-11
Publication date: 2003-03-20
Also published as: KR20010090083A

Abstract

An apparatus for adjusting a gab between a wheel drum and brake pads of vehicles, having a pipe for interconnecting a braking power generator (10) for generating oil pressure and a brake unit (20) for selectively pressing a wheel drum according to the oil pressure, includes a cylinder (200) installed to the pipe with inlet and outlet, and a piston assembly (300) installed to the cylinder for reciprocation, the piston assembly separating inner space of the cylinder into inlet and outlet areas, in which the piston assembly advances to transmit the oil pressure as it is when the brake pad is unworn, while, when the brake pad is worn, the piston communicates the inlet and outlet areas to as to replenish the outlet area with oil pressure corresponding to the worn brake pad, make the brake pad approaching the wheel drum and then separates the inlet and outlet areas.

Description

APPARATUS FOR ADJUSTING GAP BETWEEN BRAKD PADS AND

WHEEL DRUM IN VEHICLES

TECHNICAL FIELD

The present invention relates to an apparatus for adjusting a gap between bread pads and a wheel drum in a vehicle, and more particularly to an apparatus which is able to always provide a uniform

frictional brake force by automatically controlling and compensating a gap which may be generated between brake pads and a wheel drum due to the abrasion of the brake pads.

BACKGROUND ART

A brake installed in a vehicle is used for stopping a traveling

vehicle and keeping a stopped vehicle in its stop state. The brake is configured to stop a drum provided in each wheel by generating hydraulic pressure with the use of force generated by manipulation of a driver or auxiliary power.

A brake system generally includes an actuation unit 10, a braking unit 20 and an auxiliary unit. The actuation unit 10 generates a force required for braking by means of manipulation of a driver or auxiliary power, and has several components such as a master cylinder, a booster, an air master and an air chamber.

The braking unit 20 functions for substantially slowing down or stopping a vehicle by use of the force generated in the actuation unit 10. A drum brake and a disk brake can be used as the braking unit 20.

The auxiliary unit has a vacuum pump and an air compressor for obtaining an auxiliary power as well as pipes and valves for transferring the braking force.

To stop a vehicle, the drum brake system brakes a wheel with the use of a frictional force generated by contacting a brake lining to a wheel drum provided in a rotary shaft which rotates by using a power of

an engine. The brake lining is attached to a brake shoe, which is operated by a wheel cylinder.

In addition, the disk brake system stops a wheel by causing a frictional force generated by contacting brake pads to both sides of a

wheel disk provided in the rotary shaft.

The brake lining and the brake pads are made of mixture of an organic binder such as phenol resin, a metallic fiber such as steel and brass, a ceramic, and materials such as friction stabilizer, friction

conditioner and lubricant. In case of a common vehicle, a surface pressure over 5~7 kg/ cm² is exerted to the pads and a high

temperature over 150°C is generated during the operation of brake.

The brake pad gradually wears to have a smaller thickness due to friction with the wheel drum as time goes. If the brake pad wears, the gap between the brake pad and the wheel drum get longer, and as a

result a driver should step a brake pedal deeper. Taking the problem into account, there is proposed a method for mounting a space control device between a pair of brake shoes in order to adjust the gap between the shoes. However, this device is so troublesome to manage because a worker should handle it by his/her hands one by one and the wheel drum should be separated from the wheel for adjusting the gap. In addition, if the brake of a vehicle is

carelessly maintained, the brake gap cannot be controlled, which may cause decrease of a braking force and even a car accident.

DISCLOSURE OF INVENTION

The present invention is designed to solve the problems of the prior art, and an object of the invention is to provide an apparatus for adjusting a gap between a wheel drum and brake pads in a vehicle

which is capable of checking the gap by use of the change of hydraulic pressure and then automatically adjusting the gap when the hydraulic

pressure exceeds a predetermined criterion.

Another object of the present invention is to provide an apparatus capable of automatically adjusting a gap between a wheel drum and

brake pads with no use of separating a wheel from a wheel drum or any

manual manipulation of a user.

In order to accomplish the above object, the present invention

provides a gap adjusting apparatus installed to a pipe which mutually connects an actuation unit having a brake pedal and a master cylinder for pressing brake oil according to the operation of the brake pedal to

generate hydraulic pressure with a braking unit having brake pads for selectively pressing a wheel drum according to the hydraulic pressure generated in the actuation unit for braking, in order to adjust a gap between the wheel drum and the brake pads, wherein the apparatus includes a cylinder member installed to the pipe and having an inflow hole for the brake oil to flow in from the actuation unit and an outflow hole for the brake oil to flowing out to the braking unit; and a piston assembly installed in the cylinder member to be capable of reciprocating according to the hydraulic pressure generated in the actuation unit and separating the inner space of the cylinder member into an inflow space and an outflow space, the piston assembly advancing in the cylinder member when the brake pads are not worn during the braking operation in order to transfer the hydraulic pressure of the inflow space to the outflow space as it is, the piston assembly communicating the

inflow and outflow spaces each other when the brake pads are worn so that the brake oil flows into the outflow space, supplementing the hydraulic pressure corresponding to the wear degree of the brake pads, making the brake pads approach the wheel drum, and then separating

the inflow space and the outflow space again.

Preferably, the piston assembly includes a movable cylinder block capable of reciprocating within the cylinder member; a piston shaft for supporting the movable cylinder block so as to be moved to a yield position; a valve means mounted in the movable cylinder block for keeping the separation of the inflow space and the outflow space when the movable cylinder block moves beyond the yield position but not till an adjustment position, while communicating the inflow and outflow spaces so that the brake oil flows therein when the movable cylinder block moves to the adjustment position; and a cutoff means for

preventing the brake oil from flowing backward from the outflow space to the inflow space.

Also preferably, the valve means includes a yield cylinder block slidably inserted into the movable cylinder block, the piston shaft being inserted into the yield cylinder block to be capable of reciprocating therein; an inflow sealing member having a hollow portion

and fixed and supported to the yield cylinder block; a valve member combined to a head of the movable cylinder block, the valve member having an insert portion fit into the hollow portion of the inflow sealing member, an inflow valve hole being formed on an outer circumference of

the insert portion and communicated forward so as to be opened/ closed

by the inflow sealing member; and an elastic member interposed between the yield cylinder block and the movable cylinder block for elastically biasing the yield cylinder block forward, wherein, when the movable cylinder block reaches to the adjustment position, the yield cylinder block is obstructed not to move forward due to the piston shaft, and the insert portion of the valve member is removed from the hollow portion of the inflow sealing member so as to open the inflow valve hole.

Also preferably, the cutoff means includes a cutoff member combined to the valve member and having an outflow valve hole communicated with the inflow valve hole of the valve member and connected to the outflow space; and a counter-current sealing member combined to an outer circumference of the cutoff member for closing the outflow valve hole.

According to another embodiment of the present invention, there

is provided a gap adjusting apparatus which further includes a passage for communicating the inflow space and the outflow space of the cylinder member; and a valve for opening/ closing the passage.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of preferred

embodiments of the present invention will be more fully described in the following detailed description, taken accompanying drawings. In the

drawings:

FIG. 1 is a schematic view showing a brake system adopting a

brake gap adjusting apparatus according to a preferred embodiment of the present invention;

FIG. 2 is a partially sectioned perspective view showing the brake gap adjusting apparatus according to a preferred embodiment of the

present invention; FIGs. 3a and 3b show various operation states of a piston assembly of the gap adjusting apparatus according to the present

invention;

FIG. 4 is an exploded perspective view showing the piston assembly of the gap adjusting apparatus according to the present invention;

FIGs. 5 to 8 are sectional views respectively showing operation

states of the piston assembly of the gap adjusting apparatus according to the present invention; FIG. 9 is an enlarged sectional view for illustrating operation of

the piston assembly;

FIG. 10 is a sectional view showing a support member adopted in

the piston assembly;

FIG. 1 1 is a sectional view showing a valve member adopted in

the piston assembly; and

FIG. 12 is a sectional view showing a cutoff member adopted in the piston assembly.

BEST MODES FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

A gap adjusting apparatus of the present invention can be applied to both of a drum brake system and a disk brake system. As described in the above section, the drum brake system may adopt the gap adjusting apparatus of the present invention in order to control a gap between the wheel drum and the brake lining mounted to a brake shoe, while the disk brake system may adopt the gap adjusting apparatus of the present invention in order to control a gap between the wheel disk and the brake pads mounted to both sides thereof. In other words, the present invention may be applied to adjust a gap between a rotor member such as a wheel drum, which is combined to a rotary shaft

rotating by use of a power of a vehicle engine, and a friction member such as the brake lining or the bake pads, which is contacted with the rotating rotor member to generate a frictional force. Hereinafter, the

rotor member is commonly named as 'a wheel drum' and the frictional member is commonly called as 'a brake pad' in the following description and the appended claims. Thus, the terms Svheel drum' and 'brake pad' mentioned in the following description and the appended claims

should be understood to include all of the above components, and it should be not interpreted that the terms are limited to the definite embodiments of the accompanying drawings.

FIG. 1 shows a brake system provided with an apparatus for

adjusting a gap between the wheel drum and the brake pads according to the present invention. As shown in FIG. 1 , the brake system includes an actuation unit 10 for generating a power to give a frictional force, a braking unit 20 for slowing down or stopping a vehicle by use of the generated braking force, and a pipe 30 for transferring the power from the actuation unit 10 to the braking unit 20.

The actuation unit 10 also includes a brake pedal 11 for a driver to manipulate with the foot in order to slow down or stop a vehicle, and

a master cylinder 12 connected to the brake pedal 1 1 to generate hydraulic pressure. The master cylinder 12 is communicated with a tank 13 containing brake oil in order to be supplied with the brake oil. In addition, the actuation unit 10 may have an auxiliary power unit

such as a vacuum booster (not shown) connected to the brake pedal 1 1 to increase the braking force generated when a driver steps down the

brake pedal 1 1.

As the braking unit 20, the drum brake system is shown in the figure according to the preferred embodiment of the present invention.

Referring to FIG. 1 , the braking unit 20 includes a wheel drum 21 combined to a rotary shaft of a wheel which is rotated by an engine of a vehicle and brake pads 22 selectively contacted with the wheel drum 21 in order to give a frictional force for slowing down or stopping the

rotation of the wheel drum. To the wheel drum 21 , a tire wheel of the vehicle will be mounted. In addition, the brake pads 22 are preferably attached to a pair of brake shoes 23, which are electrically biased by a restoring spring 24 to approach each other. The brake shoes 23 are also moved to opposite

directions by means of a wheel cylinder 25 provided between them. The wheel cylinder 25 is provided with hydraulic pressure generated in the actuation unit 10 through the pipe 30. Thus, when a driver steps down the brake pedal 1 1 to generate a braking force, the brake shoes 23 and the brake pads 22 attached to the shoes are pressed by the wheel cylinder 25 toward the wheel drum 21 so as to provide a frictional force. To the contrary, when a driver releases the brake pedal 1 1 by taking his/her foot away from the pedal 11 , the brake shoes 23 and the brake pads 22 restore their origin positions due to a restoring force of the restoring spring 24, thus removing the friction force. The gap adjusting apparatus 100 according to the present invention is installed between the actuation unit 10 and the braking unit 20 on the pipe 30 through which hydraulic pressure is transferred. Preferably, since the brake system is provided to each wheel in a vehicle, the gap adjusting apparatus of the present invention may be installed in

all wheels of a vehicle, respectively.

Referring to FIG. 2 showing the gap adjusting apparatus 100 in detail, the apparatus of the present invention includes a cylinder

member 200 and a piston assembly 300 reciprocating in the cylinder

member 200 according to the hydraulic pressure. At both ends of the cylinder member 200, an inflow hole 40 and an outflow hole 50 are respectively formed so that brake oil can be flowed in from the actuation

unit 10 and then flowed out to the braking unit 20, as described later.

Operation states of the piston assembly 300 reciprocating in the cylinder member 200 are well shown in FIGs. 3a and 3b. In the

drawings, FIG. 3a shows a state that the brake does not operate, and FIG. 3b shows a state that a driver steps down the brake pedal 11 to apply hydraulic pressure thereto. The piston assembly separates an inner space of the cylinder member into an inflow space and an outflow space, respectively. While

the brake operates, the piston assembly just moves forward to transfer hydraulic pressure if the brake pads are not worn. But, if the brake pads are worn, the piston assembly makes the inflow and outflow spaces communicated so that the brake oil may be flowed into the outflow space in order to supplement hydraulic pressure corresponding to the wear of the brake pads, accordingly making the worn brake pads approach the wheel drum, and then the piston assembly separates the inflow space from the outflow space again. Relevant description will be

provided later in more detail.

This piston assembly 300 is shown in FIGs. 4 and 5 in more detail. Referring to FIGs. 4 and 5, the piston assembly 300 includes a base member 310, a movable cylinder block 330, a valve unit and a

cutoff unit. The valve unit keeps the separated state of the inflow and outflow spaces if the movable cylinder block does not move to a predetermined point while the brake operates, but makes the inflow and outflow spaces communicated when the movable cylinder block moves to a predetermined point so that the brake oil flows within the spaces. Such a valve unit includes a yield cylinder block 350 slidably mounted in the movable cylinder block 330, a support member 370, a valve

member 380 and an inflow sealing member 320b combined between the support member 370 and the valve member 380.

In addition, the cutoff unit functions for preventing the brake oil from flowing backward from the outflow space to the inflow space, and includes a cutoff member 390 and a counter-current sealing member 320c combined between the valve member 380 and the cutoff member

390.

The base member 310 acts as a base for supporting the movable

cylinder block 330 so that the movable cylinder block 330 may reciprocate within the cylinder member 200. In the bas member 310, there is formed an inflow hole 31 1 communicated with the inside of the cylinder member 200 so that the brake oil may flow in. preferably, the base member 310 has a screw 313 combined with a screw portion

formed in an inner circumference of the inflow hole 40 of the cylinder

member 200.

A piston shaft 360 is combined to the base member 310. Preferably, an end of the piston shaft 360 is screwed to a combination portion 314 of the base member 310. Here, the piston shaft 360 is combined to the base member 310 through the yield cylinder block 350 and the movable cylinder block 330. In other words, there are formed hollow portions in the yield cylinder block 350 and the movable cylinder block 330, and the piston shaft 360 is extended through the hollow portions in order and then combined to the base member 310. At this time, a nail head 361 is formed at the other end of the piston shaft 360. The nail head 361 has a diameter smaller than the inner diameter of the yield cylinder block 350 but larger than a through hole formed at a tail of the yield cylinder block 350. Thus, when reciprocating in the yield cylinder block 350, the piston shaft 360 moves in the range of a

stroke distance in which the nail head 361 is caught in the tail of the yield cylinder block 350.

In addition, since the outer diameter of the yield cylinder block 350 is smaller than the inner diameter of the movable cylinder block

330, the yield cylinder block 350 is inserted into the inner space of the

movable cylinder block 330. Thus, as shown in FIG. 5, with the yield cylinder block 350 being inserted into the movable cylinder block 330, the piston shaft 360 is combined through them to the base member

310.

An elastic member 340 for example a spring is interposed between the yield cylinder block 350 and the movable cylinder block 330. This elastic member 340 elastically biases the yield cylinder block 350 toward a direction to which the yield cylinder block 350 is departed from movable cylinder block 330 (or, a forward direction in the

drawing) . The movable cylinder block 330 is a component which moves in

the cylinder member 200 due to the generation of hydraulic pressure according to the inflow of the brake oil so as to transfer the hydraulic pressure to the braking unit 20. In the movable cylinder block 330, a piston ring 320a is provided for the sealing with the inner wall of the cylinder member 200. For example, the required number of

combination grooves 331 is formed on the outer circumference of the movable cylinder block 330, and the ring-shaped piston rings 320a are preferably combined to the grooves 331. Also preferably, the piston

ring 320a is made of elastic materials such as rubber, and in the present embodiment there are provided four piston rings 320a for the enhancement of sealing, as an example. Due to the sealing of the piston rings 320a, the inner space of the cylinder member 200 is separated into two independent spaces: an area 200A connected to the master cylinder 12 of the actuation unit 10 (see FIG. 1) for receiving

hydraulic pressure; an area 200B connected to the braking unit 20 for applying hydraulic pressure. In the present description, these areas are respectively named as "an inflow space 200A" and "an outflow space

200B". According to the present invention, the brake oil flowed into the cylinder member 200 from the actuation unit 10 flows even to the insides of the movable cylinder block 330 and the yield cylinder block

350. More specifically, a communication hole 332 is formed in the movable cylinder block 330 so that the inside of the movable cylinder

block 330 is communicated with the inflow space 200A, and the yield cylinder block 350 has communication holes 351 and 352 respectively communicated with the inside of the movable cylinder block 330. Shape and number of the communication holes are not limited to the embodiment and the drawings. Thus, the brake oil flowed in the cylinder member passes the communication holes 332, 351 and 352 in order and then flows into even the movable cylinder block 330 and the yield cylinder block 350. A head of the yield cylinder block 350 is combined with the support member 370, which is well shown in the sectional view of FIG.

10. The support member 370 fixes the inflow sealing member 320b to be supported by the yield cylinder block 350. In addition, the support member 370 has a hollow 371 from its head to its tail, so that the

hollow 371 is communicated with the inside of the yield cylinder block 350 when combined with the yield cylinder block 350 as shown in FIG.

5. A function of the hollow 371 is described later. At the head of the support member 370, a hooking protrusion 372 is formed so that the inflow sealing member 320b is combined and supported thereto. The inflow sealing member 320b is a member having a hollow portion made

of elastic materials such as rubber, and combined and fixed to the

support member 370.

The inflow sealing member 320b positioned opposite to the support member 370 is combined with the valve member 380, whose configuration is shown in FIG. 1 1 in detail. The valve member 380 plays a role of adjusting a brake gap by automatically allowing the flow

of brake oil between the inflow space 200A and the outflow space 200B when a gap between the wheel drum 21 and the brake pads 22 is increased due to the wear of the brake pad 22. The valve member 380 has a screw portion 381 combined to the head of the movable cylinder block 330 and an insert portion 382 inserted into the hollow of the inflow sealing member 382. The insert portion 382 has a plurality of inflow valve holes 383 which are communicated forward in connection with a hollow portion 384. The inert portion 382 is fit into the hollow of the inflow sealing member 320b, and moves to a direction which allows the separation from the hollow portion of the inflow sealing

member 320b when the hydraulic pressure increases due to the braking operation of a driver, as described below.

The valve member 380 is also combined with the cutoff member

390. As shown in FIG. 12, the screw portion formed in the inner circumference of the valve member 380 is combined with a screw portion 391 formed in the outer circumference of the cutoff member 390. The cutoff member 390 plays an act of preventing the brake oil from flowing backward after flowing from the inflow space 200A to the outflow space 200B. The cutoff member 390 has a plurality of outflow valve holes 392 communicated with the outflow space 200B on its outer circumference, and these outflow valve holes 392 are communicated backward in connection with a hollow 393. Thus, the inflow valve holes formed in the valve member 380 are mutually connected to the outflow valve holes 392 formed in the cutoff member 390 through the hollows formed in the valve member 380 and the cutoff member 390.

To the outer circumference of the cutoff member 390 on which the outflow valve holes 392 are formed, a counter-current sealing member 320c is combined for preventing the brake oil from flowing

backward, as described later. Preferably, the material of the counter-current sealing member 320c is similar to the inflow sealing

member 320b.

Seeing the operation of the inflow valve holes 383 and the outflow valve holes 382 formed in the valve member 380 and the cutoff member

390, though the sealing members 320b and 320c close the valve holes 383 and 392, the brake oil may overcome the pressure of the sealing

members and flow outside from the valve holes since a high pressure over 200kg/ cm² is applied during the braking operation, but the inflow

of the brake oil from gaps between the members 380 and 390 and the

sealing members 320b and 320c into the valve holes 383 and 392 is prevented. In other words, the valve holes and the sealing members functions like a one-way valve.

At this time, the inflow valve holes 383 and the outflow valve

holes 392 are not formed directly on the outer circumferences of the members 380 and 390, but after forming grooves of a predetermined depth on the outer circumferences of the members, the holes 383 and 392 are formed in the grooves. Since the sealing members 320b and 320c are made of rubber, if the valve holes are formed without the groove, the sealing member may be damaged or perforated due to the

above-mentioned high pressure applied during the braking operation. This may make the cutoff operation unreliable. The inventors have revealed that the grooves decentralize the high pressure and thus prevent the pressure from focusing in a local area, resulting in increase

of durability of the sealing members and improvement of the hydraulic pressure cutoff effects.

As well known from the above configuration, in the gap adjusting apparatus of the present invention, the inflow space 200A and the

outflow space 200B are completely separated in the cylinder member

200 during the normal condition. In other words, the flow of brake oil is prevented owing to the piston ring 320a closely contacted with the inner circumference of the cylinder member 200 and the counter-current sealing member 320c combined to the outer

circumference of the cutoff member 390. Now, the operation of the gap adjusting apparatus constructed as above according to the present invention is described in detail.

Installation of the Gap Adjusting Apparatus Prior to describing the operation of the gap adjusting apparatus according to the present invention, a method for installing this gap adjusting apparatus to a pipe is described in brief. The gap adjusting apparatus of the present invention can be easily installed just to the pipe 30 without separating a tire from the wheel drum 21. In other words, after cutting the pipe 30, the gap adjusting apparatus is

installed so that the inflow hole 40 and the outflow hole 50 of the cylinder member 200 are respectively connected to the actuation unit 10 and the braking unit 20. And then, the insides of the inflow space 200A and the outflow space 200B are filled with brake oil, and at this time the air existing in the spaces can be discharged through air

discharge holes 1 10a and 1 10b (see FIG. 1). Now, the operations of the gap adjusting apparatus installed as above are described in cases, namely when the brake pads are normal and when the brake pads are

worn.

Operation with the Normal Brake Pads

The operation of the brake is now described in case the gap

between the wheel drum 21 and the brake pads 22 is normal in FIG. 1.

If a driver steps down the brake pedal 1 1 for applying pressure in order to slow down or stop a moving vehicle, the master cylinder 12 generates hydraulic pressure. Preferably, this hydraulic pressure may be more increased with the use of an auxiliary power device such as a vacuum booster (not shown). At this time, the brake oil flows through the pipe 30 into the inflow hole 40 of the cylinder member 200 equipped in the gap adjusting apparatus according to the present invention, as shown in FIG. 5. The brake oil flowed into the inflow hole 40 flows into the inflow space 200A of the cylinder member 200 through the inflow holes 31 1 of the base member 310, and the hydraulic pressure is thus applied to the movable cylinder block 330 so that the movable cylinder block 330 moves forward. At this time, since the inflow space 200A and the outflow space 200B in the cylinder member 200 are isolated each other by the piston rings 320a and the counter-current sealing member 320c, the pressure caused by the inflow of the brake oil is entirely exerted to the movable cylinder block 330.

Examining this state more concretely, the yield cylinder block 350

inserted in the movable cylinder block 330 is elastically biased forward due to the elastic member 340 with the valve member 380 and the movable cylinder block 330 being combined each other. Thus, since

the inflow sealing member 320b is also elastically biased forward by the support member 370 combined to the yield cylinder block 350, the

insert portion 382 of the valve member 380 is fit into the hollow portion of the inflow sealing member 320b. In this state, the inflow valve holes 383 formed in the insert portion 382 of the valve member 380 are closed by the inflow sealing member 320b, so the brake oil cannot flow therein. On the while, since the piston shaft 360 is capable of reciprocating within the yield cylinder block 350 without any resistance, both of the movable cylinder block 330 and the yield cylinder block 350 move forward when the brake oil flows in the inflow space 200A according to the operation of the brake pedal.

The movement of the movable cylinder block 330 is well shown in FIG. 6. As shown in FIG. 6, the movable cylinder block 330 advances from its initial position A to a brake yield position B. The distance

between the above two positions is identical to a stroke distance of the piston shaft 360 which is moving within the yield cylinder block 350.

It is defined that the yield position B is a maximum distance to which the movable cylinder block 330 may advance when a driver steps down the brake pedal to the maximum, and the maximum hydraulic pressure

is applied to the braking unit 20 at this position. Hereinafter, the term yield position' is used to have the above meaning without any special definition, even in the appended claims.

According to the present invention, though advancing to the yield

position B, the movable cylinder member 200 does not contact with the

cylinder member 200, and there exists a gap D between them. If the hydraulic pressure increases in the outflow space 200B according to the above process and this increased hydraulic pressure is transferred to the wheel cylinder 25 (see FIG. 1), the brake shoes 23 are pushed to opposite directions due to the operation of the wheel cylinder, so the brake pads 22 attached to the brake shoes 23 are contacted with

the wheel drum 21 to give a frictional force and the wheel is thus

stopped.

Then, if a driver releases the brake pedal 1 1 , the hydraulic pressure in the master cylinder 12 is reduced, thus the pressure in the inflow space 200A decreases, the brake shoes 23 is pulled by means of

the restoring spring 24 of the braking unit 20 so as to make the brake oil flow backward, and thus the movable cylinder block 330 in the cylinder member 200 retreats to return to its initial position.

Example of adjusting a brake gap

As the brake is used more and more, the brake pads 22 of the braking unit 20 are gradually worn and their thickness gradually decreases. In that case, when a driver steps down the brake pedal, it

may happen that the brake pads 22 cannot be contacted with the wheel

drum 21 so sufficient to obtain a sufficient braking force though the movable cylinder block 330 advances to the yield position B of FIG. 6. Accordingly, the yield cylinder block 330 in the cylinder member 200

advances beyond the yield position B up to a position C between the

yield position B and an adjustment position C where the gap adjustment is achieved. This state is well shown in FIG. 7.

To explain the above process in more detail with reference to FIG. 7, if a driver steps down the brake pedal 1 1 stronger to increase the hydraulic pressure in the inflow space 200A with the movable cylinder

block 330 reaching to the yield position B, the movable cylinder block 330 moves forward with overcoming the elastic force of the elastic member 340 since the yield cylinder block 350 is obstructed not to advance due to the piston shaft 360.

At this time, since the valve member 380 combined to the head of the movable cylinder block 330 advances together, the insert portion of the valve member 380 slowly comes off from the hollow portion of the

inflow sealing member 320b. Furthermore, the brake oil flowed in the cylinder member 200 flows through the communication holes 332, 351 and 352 formed in the movable cylinder block 330 and the yield

cylinder block 350 and pushes a rear of the insert portion 382 inserted into the hollow portion of the inflow sealing member 320b through the hollow of the support member 370. However, the insert portion of the valve member 380 is not

completely removed from the inflow sealing member 320b, so the inflow valve hole 383 formed in the insert portion is still closed by the inflow sealing member 320. Thus, the brake oil cannot flow into the inflow

valve hole 383 at this point. If the brake pads 22 are worn and a clearance of the brake pedal

1 1 is more increased, the movable cylinder block 330 at last advances to the adjustment point C. This adjustment point C is defined as a point at which the insert portion of the valve member 380 is removed from the hollow of the inflow sealing member 320b and thus the inflow

valve hole 383 closed by the inflow sealing member 320b is opened. Hereinafter, the term 'adjustment position' will be used in such a

meaning without any special definition, even in the appended claims. The opened inflow valve hole 383 is well shown in FIG. 8, and FIG. 9 shows a partially enlarged view of the hole.

If the inflow valve hole 383 opens, the brake oil in the cylinder

member 200 flows into the inflow valve hole 383, then passes through the hollow portion of the valve member 380 and the hollow portion of the cutoff member 39, and then flows into the outflow space 200B through the outflow valve hole 392 of the cut off member 390, as shown

by the arrows in FIG. 8. As described above, though the counter-current sealing member 320c closes the outflow valve hole 392 of the cutoff member 390, the brake oil applied with a high pressure may overcome the cutoff force to flow out. The brake oil flowed into the

outflow space 200B flows again to the wheel cylinder 25 so as to actuate

the wheel cylinder 25 so that the brake shoes 23 move closer to the

wheel drum 21. Thus, the brake pads 22 advances toward the wheel drum 21 as much as the worn thickness, so the gap between the wheel drum 21 and the brake pads 22 can be maintained to its initial proper state.

As soon as the gap between the wheel drum 21 and the brake pads 22 is adjusted, the hydraulic pressure in the outflow space 200B is decreased to some degree to be in balance with the hydraulic pressure in the inflow space 200A. Then, the movable cylinder block 330 is elastically biased again by the elastic member 340 and retreated

backward. These operations are performed while the driver is still stepping down the brake pedal 1 1.

As a result, the movable cylinder block 330 is retreated and stops at the yield position B, which is initially a balance position. At the

same time, the valve member 380 is inserted into the hollow portion of the first sealing member 320b again, so the inflow valve hole 383 is closed again as it originally was. On the other hand, since the counter-current sealing member 320c prevents the brake oil in the outflow space 200B from flowing into the outflow valve hole 392 of the

cutoff member 390, the communication between the inflow space 200A and the outflow space 200B is shut off again and they are separated again.

If the driver steps down the brake pedal 1 1 once more after the

gap between the wheel drum 21 and the brake pad 22 is adjusted, the

driver need not step down the brake pedal so deep as before the adjustment, and the maximum braking force is exerted when the movable cylinder block 330 reaches to the yield position B. This

ensures the driver to manipulate a brake pedal always by the same clearance. Embodiment of a brake hydraulic pressure releasing unit

According to another embodiment of the present invention, a gap

adjusting apparatus provided with a means for easily releasing the hydraulic pressure exerted in the outflow space 200B. As mentioned above, though the gap between the wheel drum 21 and the brake pads 22 is adjusted, the brake pads 22 should be replaced with new ones when they are entirely worn. When it is required to separate the wheel drum 21 , the brake shoes 23 or the brake pads 22 for the purpose of change of parts or repair of the vehicle, the work can be uneasy due to the narrow space between the wheel drum and the brake pads.

In this case, a hydraulic pressure releasing unit installed to the

gap adjusting apparatus of the present invention can be used. This hydraulic pressure releasing unit includes a passage 120 connecting the inflow space 200A and the outflow space 200B and a valve 130

mounted on the passage.

Thus, when intending to release the hydraulic pressure, a worker manipulates the valve 130 so that the inflow space 200A and the outflow space 200B are communicated with each other. Then, the brake oil in the outflow space 200B which has a relatively high pressure

due to the restoring spring 24 is discharged to the inflow space 200A, so the hydraulic pressure in the outflow space 200B is decreased. Thus,

the hydraulic pressure exerted to the wheel cylinder 25 is released, and the brake shoes 23 and the brake pads 22 are retreated from the wheel drum 21 , which allows easy work to the worker.

In addition, the present invention can be adopted all kinds of vehicles, and the stroke distance of. the movable cylinder block can be easily adjusted. In other words, the stoke distance for a small-sized car is relatively shorter than that of a large-sized car, a washer having a suitable length is selectively combined to the piston shaft in order to adjust the stoke distance of the movable cylinder block. This configuration can be manufactured in much lower costs than the

conventional one which should manufacture a gap adjusting device for each kind of vehicle separately.

INDUSTRIAL APPLICABILITY

According to the brake gap adjusting apparatus of the present

invention, a change of the hydraulic pressure caused by the wear of the

brake pads is automatically sensed, and additional hydraulic pressure is applied corresponding to the wear degree when the hydraulic pressure exceeds a predetermined criterion, thus adjusting the gap between the wheel drum and the brake pads. This is helpful to solve

the conventional troublesomeness that a worker should stop a vehicle and then conduct manual or mechanical works one by one in order to adjust the brake gap.

In addition, since the gap adjusting apparatus of the present

invention can be installed on the pipe between the actuation unit and the braking unit, installation and maintenance are very convenient compared with the conventional one which allows installation just to the wheel portion.

Furthermore, comparing with the conventional adjusting device which is inaccurate since a worker visually checks the gap between the wheel drum and the brake pads and adjust the gap by the hand, the present invention gives much higher accuracy and reliability since the gap is adjusted according to the difference between the hydraulic pressure generated from the brake pedal manipulated by a driver and the hydraulic pressure exerted to the braking unit.

The present invention has been described in detail. However, it

should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and

modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

Claims

What is claimed is:

1. A gap adjusting apparatus installed to a pipe (30) which mutually connects an actuation unit (10) having a brake pedal (1 1) and a master cylinder (12) for pressing brake oil according to the operation of the brake pedal to generate hydraulic pressure with a braking unit (20) having brake pads (22) for selectively pressing a wheel drum (21) according to the hydraulic pressure generated in the actuation unit ( 10) for braking, in order to adjust a gap between the wheel drum and the brake pads, the apparatus comprising: a cylinder member (200) installed to the pipe and having an inflow hole (40) for the brake oil to flow in from the actuation unit and an outflow hole (50) for the brake oil to flowing out to the braking unit; and a piston assembly (300) installed in the cylinder member to be

capable of reciprocating according to the hydraulic pressure generated in the actuation unit and separating the inner space of the cylinder member into an inflow space (200A) and an outflow space (200B), the

piston assembly advancing in the cylinder member when the brake

pads are not worn during the braking operation in order to transfer the hydraulic pressure of the inflow space to the outflow space as it is, the piston assembly communicating the inflow and outflow spaces each

other when the brake pads are worn so that the brake oil flows into the outflow space, supplementing the hydraulic pressure corresponding to

the wear degree of the brake pads, making the brake pads approach the

wheel drum, and then separating the inflow space and the outflow

space again.

2. A gap adjusting apparatus according to claim 1 , wherein

the piston assembly includes:

a movable cylinder block (330) capable of reciprocating within the

cylinder member;

a piston shaft (360) for supporting the movable cylinder block so

as to be moved to a yield position;

a valve means mounted in the movable cylinder block for keeping

the separation of the inflow space (200A) and the outflow space (200B)

when the movable cylinder block moves beyond the yield position but

not till an adjustment position, while communicating the inflow and

outflow spaces so that the brake oil flows therein when the movable

cylinder block moves to the adjustment position; and

a cutoff means for preventing the brake oil from flowing backward

from the outflow space to the inflow space.

3. A gap adjusting apparatus according to claim 2, wherein

the valve means includes:

a yield cylinder block (350) slidably inserted into the movable cylinder block, the piston shaft (360) being inserted into the yield cylinder block to be capable of reciprocating therein; an inflow sealing member (320b) having a hollow portion and fixed and supported to the yield cylinder block; a valve member (380) combined to a head of the movable cylinder block, the valve member having an insert portion (382) fit into the hollow portion of the inflow sealing member, an inflow valve hole being formed on an outer circumference of the insert portion and communicated forward so as to be opened /closed by the inflow sealing

member; and an elastic member (340) interposed between the yield cylinder block and the movable cylinder block for elastically biasing the yield

cylinder block forward, wherein, when the movable cylinder block reaches to the adjustment position, the yield cylinder block is obstructed not to move forward due to the piston shaft, and the insert portion of the valve member is removed from the hollow portion of the inflow sealing

member so as to open the inflow valve hole.

4. A gap adjusting apparatus according to claim 3, further

comprising a support member (370) screwed to the head of the yield cylinder block with having a hooking protrusion combined to the hollow

portion of the inflow sealing member in order to fix and support the inflow sealing member to the yield cylinder block.

5. A gap adjusting apparatus according to claim 4, wherein a

hollow portion is formed thoroughly from a head to a tail of the support

member.

6. A gap adjusting apparatus according to claim 3, wherein

the inflow valve hole is formed within a groove formed on an outer

circumference of the valve member.

7. A gap adjusting apparatus according to claim 3, wherein

communication holes are formed in the movable cylinder block and the

yield cylinder block so that the brake oil flowed in the inflow space of

the cylinder member is capable of flowing thereto.

8. A gap adjusting apparatus according to claim 2, wherein

the cutoff means includes:

a cutoff member (390) combined to the valve member and having

an outflow valve hole communicated with the inflow valve hole of the

valve member and connected to the outflow space; and

a counter-current sealing member (320c) combined to an outer

circumference of the cutoff member for closing the outflow valve hole.

9. A gap adjusting apparatus according to claim 8, wherein

the outflow valve hole is formed within a groove formed on the outer circumference of the cutoff member.

10. A gap adjusting apparatus according to any of claims 1 to 9, further comprising:

a passage (120) for communicating the inflow space and the outflow space of the cylinder member; and a valve (130) for opening/ closing the passage.