JPH01261524A - Wheel cylinder for brake - Google Patents

Abstract

PURPOSE:To restrain the drag of a brake friction member by causing a piston to stroke so that the brake friction member can be slidably brought into contact with a brake drum, and further causing an auxiliary piston and a piston member to stroke. CONSTITUTION:When a brake liquid is supplied to the inside of a cylinder body 1 at the time of braking, a piston 3 is caused to stroke, and a brake friction member 5 is slidably brought into contact with a brake drum to produce a braking force. An auxiliary piston 2, a piston member 9, and an adjuster screw 13 are also caused to stroke. The shoe clearance is very satisfactorily maintained at a set value. Thus, the operational feeling of the brake is significantly improved, and the drag of the brake friction member can be also satisfactorily restrained.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides a shoe gap automatic jl! ]Relating to a brake wheel cylinder equipped with an adjustment device.

[Conventional technology]

A conventional brake wheel cylinder of this type is disclosed in, for example, Japanese Utility Model Application Publication No. 19831/1983. This wheel cylinder has an automatic adjustment mechanism in which one end of an adjustment member is threadedly coupled to a piston member that slides within the cylinder, and automatically rotates the adjustment member when the movement of the piston member is excessive. The automatic adjustment mechanism includes a drive ring that is reversibly coupled to the adjustment member and coupled to the cylinder by a clutch, a compression spring that biases the clutch engagement of the drive ring, and a compression spring that biases the torsion coupling between the piston member and the adjustment member. It is equipped with a spring, a clutch that suppresses the rotation of the adjustment member, etc.

[Problem to be solved by the invention]

However, such conventional brake wheel cylinders have a structure that automatically adjusts the shoe gap to be set (direct) only when the shoe gap becomes larger than a set value. Specifically, during braking, the piston The adjustment member strokes together with the member, and the drive ring is released from the clutch engagement and rotates with a reversible screw, so that the shoe gap is automatically adjusted when the brake is released. , the shoe gap cannot be returned to the proper set value.For this reason, when the brake drum thermally expands and the shoe gap becomes excessive, over-adjustment remains.
When the brake drum contracts due to cooling, so-called dragging occurs.

1. Means for Solving the Problems] The present invention has been made in view of the above-mentioned conventional technical problems, and consists of a cylinder body, and a cylinder body that is rotatably and slidably fitted into the cylinder body. a piston member whose protrusion abuts against the front end surface of the cylinder body to restrict its return position; and an adjuster which is coaxially screwed into the piston member with an irreversible screw and supports a brake friction member at the front end. A screw, a clutch member provided on the inner periphery of the cylinder body and having a forward-facing clutch surface and a backward-facing clutch surface, and a piston member are engaged with each other by a first reversible screw having the irreversible screw and a reverse screw, and the forward-facing clutch is assembled. an actuating nut that has a clutch surface that faces the surface so as to be capable of connecting and disconnecting and constitutes a first clutch, and that forms an operating gap in the central axis direction with a locking portion of the piston member in a returned state; and the actuating nut and the piston. a first set spring compressed and interposed between the piston member and the first clutch member to bias the frictional connection of the first clutch; and a second reversible screw having a larger lead in the same direction as the first reversible screw on the piston member. an actuating screw that is screwed together and has a clutch surface that connects/disconnectably faces the rearward clutch surface and constitutes a second clutch; This is a brake wheel cylinder equipped with a second set spring that biases the frictional connection of two clutches.

The clutch member is provided in the cylinder body so as to be movable within a predetermined range in the direction of the central axis, and can be biased toward the backward position by an overtravel spring. Insert freely,
A piston member can be rotatably fitted into the auxiliary piston.

Furthermore, an annular engaging protrusion is formed at the front end of the adjuster screw, and the free end of the stopper, one end of which is fixed to the cylinder body, is elastically engaged with the engaging protrusion and rotated into the recess of the adjuster screw. A brake friction member can be received in the two prongs of the movable and coaxially provided receiving member.

[Operation] When brake fluid is supplied into the cylinder body during braking, the piston member (and auxiliary piston) and adjuster screw stroke. If the forward stroke of the piston member during braking is smaller than the operating gap, the piston member strokes within the range of the operating gap to generate the required braking force. At this time, the actuating nut is pulled in accordance with the stroke of the piston member, and the frictional contact of the first clutch is released, so that it idles in the range of the actuating gap by the biasing force of the first set spring. In addition, since the actuating screw cannot rotate when the second clutch is connected, the piston member rotates and strokes forward due to the action of the second reversible screw, strokes the adjuster screw that supports the brake friction member, and unscrews the actuating screw. In this state, braking force is generated. Therefore, the stroke length of the adjuster screw during braking operation is longer than the actual stroke length of the piston member by the amount of screwing. When the brake is released, the resilient force of the shoe return spring causes the piston member (and the auxiliary piston) to return until the protrusion comes into contact with the front end surface of the cylinder body, and the return position is regulated.

At that time, the second set 1-spring is slightly compressed and the second set 1-spring is slightly compressed.
Since the clutch is released, the operating screw idles, and with the first clutch frictionally connected, the piston member is rotated in the opposite direction to the forward stroke by the action of the first reversible screw, and the adjuster screw is screwed. let them in. Therefore, if the forward stroke of the piston member during braking operation is smaller than the operating gap, the amount of threading of the adjuster screw will be larger than that of the screw-out type, and the shoe gap will be adjusted toward the predetermined set screw gap. It will converge.

On the other hand, when the forward stroke of the piston member during braking operation is larger than the operating gap, the piston member moves forward within the range of the operating gap and then moves with the operating nut that locks in the locking portion. It strokes further to generate the required braking force. At this time, as the piston member strokes, the piston member is rotated in one direction by the second reversible screw with the actuation screw that is frictionally connected to the clutch member in the second clutch, and the adjuster screw that supports the brake friction member is rotated in one direction. is screwed out to a large extent, and braking force is generated in this state.

When the brake is released, as the piston member returns, the second
The clutch is released, the actuating screw rotates idly, and the actuating nut returns together with the piston member until the first clutch is frictionally connected. After the first clutch is frictionally connected, the piston member is rotated by the action of the first reversible screw for only a return stroke corresponding to the operating gap, and the adjuster screw is screwed in by a predetermined amount. However, since the lead of the first reversible screw is smaller than the lead of the second reversible screw, the length of the stroke of the actuating nut when it is locked in the locking part is large or small. Depending on the method, the shoe gap becomes the same as the screw type, or smaller or larger than the screw V, and the shoe gap gradually converges toward the set value with each braking operation.

According to the second aspect of the invention, when the brake friction member slides on the brake drum during braking and the axial force of the adjuster screw increases, the second reversible screw can be rotated by the friction force. The overtravel spring is compressed as the piston member strokes, and the adjuster screw moves forward and strokes together with the actuation screw and clutch member, preventing over-adjustment due to elastic deformation of the brake drum, etc., and automatically adjusting the shoe gap. Prevent damage to equipment.

Further, according to the third aspect of the invention, the auxiliary piston slides with respect to the cylinder body, and the piston member only rotates with respect to the auxiliary piston, so that the piston member itself does not rotate or slide. Compared to the case where a side stand is used, the liquid tightness of the piston member and the auxiliary piston can be maintained well for a long period of time.

Furthermore, according to the fourth aspect of the invention, the shoe gap can be manually adjusted. That is, when the tool is engaged with the engagement protrusion of the adjuster screw and the adjuster screw is rotated against the elastic force of the stopper, the adjuster screw is screwed into or out of the piston member.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

1 to 5 show an embodiment in which the present invention is applied to a double-opening type wheel cylinder of a two-leading brake. In the figure, reference numeral 1 denotes a cylinder body, which is fixed to a backing plate (not shown) with bolts. An auxiliary piston 2 and a piston 3 are slidably fitted into the cylinder body 1 in a state where both sides can be opened. The auxiliary piston 2 has a cylindrical shape and is held liquid-tight with respect to the cylinder body 1 with a cup seal 4 interposed therebetween, and an outward flange-shaped protrusion 2a at the front end is attached to one front end surface of the cylinder body l. Due to the contact, the return position is regulated. The piston 3 is maintained liquid-tight with a cup seal 6 interposed therebetween, and the outward flange 6a at the front end contacts the other front end surface of the cylinder body 1 to restrict its return position, and the two-pronged portion 6b at the front end One of the brake friction members 5 is received. 8 is piston 3
This is a dustproof boot that covers between the outward flange portion 6a and the cylinder body l.

The auxiliary piston 2 has a piston member 9 with a liquid seal 10.
The outward flange-shaped protrusion 9a at the front end abuts against the front end surface of the auxiliary piston 2 with a dry bearing 12 interposed therebetween to reduce rotational and sliding friction. contact, and the return position is regulated. The purpose of the auxiliary piston 2 is to eliminate the relative sliding movement of the piston member 9 itself and give only rotation to the piston member 9, thereby reducing the wear and tear of the liquid seal 10. If machining accuracy is improved, auxiliary piston 2
can be omitted, and in that case, the piston member 9 is fitted into the cylinder body 1 so as to be rotatable and slidable.

An adjuster screw 13 coaxially screwed into the piston member 9 by an irreversible screw 7 supports the other brake friction member 14 via a receiving member 15 at its front end. Here, the irreversible screw 7 is the adjuster screw 1.
It is defined as a screw that does not rotate relative to each other due to the axial acting force between the piston member 3 and the piston member 9, and a general single thread screw falls under this category. The receiving member 15, as shown in FIG.
It has a circular shape with a two-pronged portion 15a formed at one end, is rotatably and coaxially provided in the recess 13b of the adjuster screw 13, and receives the brake friction member 14 in the two-pronged portion 15a in a relatively unrotatable manner. . Further, the adjuster screw 13 elastically engages the free end of the stopper 16, one end of which is fixed to the cylinder body l with a screw 18, with the annularly formed engagement protrusion 13a, thereby preventing rotation in the normal state. ing. 1
7 is a dustproof boot that covers between the front end of the adjuster screw 13 and the cylinder body 1.

Reference numeral 19 denotes an annular clutch member provided inside the cylinder body 1 and having a forward-facing clutch surface 20 (see FIG. 5) and a backward-facing clutch surface 21. The clutch member 19 is movable within a predetermined range in the direction of the central axis, with grooves 19a engaging with a plurality of keys 22 press-fitted into the inner circumference of the cylinder body 1. An overtravel spring 24 compressed between the attached snap ring 23 is biased rearward with a predetermined load, and when the brake is released as shown in FIG. The retracted position is regulated by coming into contact with a snap ring 31 that is attached. Note that 19b is a through hole through which brake fluid flows.

A bottomed cylindrical neck portion 25 is provided at the rear end of the piston member 9.
are coaxially formed, an actuating nut 26 shown in FIG. Actuation screw 27
are screwed together with a second reversible screw 29. Here, the reversible screws 28 and 29 are defined as screws that inevitably undergo rotational movement due to forward and reverse relative movement in the axial direction between the piston member 9 and the actuating nut 26 or the actuating screw 27. This applies to strings. In addition, the first reversible screw 28
is a same direction thread with a lead smaller than that of the second reversible screw 29, and the non-reversible screw 7 is configured with a reverse thread than the double reversible threads 28 and 29. For example, the non-reversible screw 7 has a right-hand thread. If it is a hem, both reversible hems 28 and 29 are left-handed.

The actuating nut 26 has a clutch surface 26a formed of a truncated conical surface at its rear end, and is screwed onto the outer periphery of the threaded portion 25 of the piston member 9 with the first reversible screw 28, so that the clutch surface 26a acts as a clutch. Forward clutch surface 20 of member 19
The frictional connection of the first clutch 30 is biased by a first set spring 38 which is compressed and interposed between the actuating nut 26 and the piston member 9, and which constitutes the first clutch 30 and which is compressed and interposed between the actuating nut 26 and the piston member 9. In addition, in the returned state shown in FIG. 1, an operating gap δ in the central axis direction is formed with the radial locking portion 32 fixedly provided at the rear end of the threaded portion 25. In addition, 26b is
35 is a through hole through which brake fluid flows;
This is a bearing for allowing relative rotation of the actuating nut 26 with respect to the piston member 9.

The actuating screw 27 has a cylindrical shape as shown in FIG. 4, and has a clutch surface 27 having a forward-facing truncated conical surface at the rear end.
a is formed on the inner periphery of the threaded portion 25 of the piston member 9.
When screwed together with the reversible screw 29, this clutch surface 27
a faces the rearward clutch surface 21 of the clutch member 19 so as to be connectable and disconnectable, thereby forming a second clutch 33, and a second set spring 34 compressed and interposed between the clutch member 19 side The frictional connection of the clutch 33 is energized. Note that 36 is the clutch member 1 of the actuating screw 27.
This is a bearing for allowing relative rotation on the 9 side.

Next, the effect will be explained.

If brake fluid is supplied into the cylinder body l during braking,
The piston 3 moves to the right in the figure and strokes, bringing the brake friction member 5 into sliding contact with the brake drum to generate braking force, and at the same time, the auxiliary piston 2. The piston member 9 and the adjuster screw 13 move toward the left in the figure and make a stroke.

If the forward stroke of the piston member 9 during braking is smaller than the operating gap δ, the piston member 9 strokes within the range of the operating gap δ and generates the required braking force. At this time, the actuating nut 26 is pulled in accordance with the stroke of the piston member 9, and the frictional connection of the first clutch 30 is released, so that the actuating nut 26 idles within the range of the actuating gap δ due to the biasing force of the first set spring 38. . Furthermore, since the actuating screw 27 is not rotatable due to the connection of the second clutch 33, the piston member 9 rotates and strokes forward with respect to the auxiliary piston 2 due to the action of the second reversible screw 29, and the piston member 9 strokes toward the stopper 16. The engaged and unrotatable adjuster screw 13 is stroked and screwed out, and the brake friction member 14 is brought into sliding contact with the brake drum to generate braking force. Therefore, the stroke length of the adjuster screw 13 during the braking operation is longer than the stroke length of the piston member 9.

When the brake is released, the auxiliary piston 2 and the piston member 9 are moved by the elastic force of the Sony return spring (not shown).
The projection 2a returns integrally until it abuts between the front ends of the cylinder body 1. At that time, the second set spring 34 is slightly compressed and the actuating screw 27 is moved to the second clutch 33.
is released and idles, and since the first clutch 30 is frictionally connected and cannot rotate, the first reversible screw 28 causes the piston member 9 to rotate in the opposite direction to that during the forward stroke. and screw in the adjuster screw 13. Therefore, when the forward stroke of the piston member 9 during braking is smaller than the operating gap δ, the screwing amount of the adjuster screw 13 becomes larger than the screwing out amount, and the shoe gap becomes the predetermined set shoe gap. Expand and converge towards the line (.

On the other hand, when the stroke of the piston member 9 during braking is larger than the operating gap δ, the piston member 9 moves forward within the range of the operating gap δ, and then the actuating nut that is locked in the locking portion 32 is moved. 26 to generate the required braking force. At this time, since the actuating screw 27 is frictionally connected to the clutch member 19 by the second clutch 33 and cannot rotate, the piston member 9 is rotated in one direction by the second reversible screw 29 as the piston member 9 strokes. The adjuster screw 13 that supports the brake friction member 14 is screwed out to a large extent, and in this state, the braking force is stopped.

When the brake is released, as the piston member 9 returns, the second clutch 33 is released and the operating screw 27 idles, and the operating nut 26 returns together with the piston member 9 until the first clutch 30 is connected by I2 friction. . 1st clutch 30
After the frictional connection is made, due to the action of the first reversible screw 28,
The screw 1-neck member 9 is rotated only during the return stroke corresponding to the operating gap δ, and the adjuster screw 13 is screwed in by a predetermined amount.

Therefore, since the lead of the first reversible screw 28 is smaller than the lead of the second reversible screw 29, the adjuster screw 1
The amount of screwing in (3) may be the same as the amount of screwing out, or smaller (or larger) than the amount of screwing out, depending on the length (L) of the forward stroke of the actuating nut 26 when it is locked in the locking part 32. , each time a braking operation is performed, the air gap converges toward the set value.When the air gap between the brake friction member 14 and the brake drum is at the set value,
The forward stroke of the piston member 9 during braking (PS, = δ
+L) is PS, -δXC/B. Here, B is the lead of the first reversible screw 28, and C is the lead of the second reversible screw 29.
is the lead.

Next, during braking, when the brake friction member 14 comes into sliding contact with the brake drum and the axial force of the adjuster screw 13 increases, the second reversible screw 29 cannot rotate due to the friction force, and the piston member 9 The overtravel spring 24 is compressed with the stroke, and the adjuster screw 13 moves forward and strokes together with the actuating screw 27 and the clutch member 19, thereby preventing over-adjustment due to elastic deformation of the brake drum, etc., and providing an automatic shoe gap adjustment device. Prevents shellfish from breaking.

FIG. 6 shows the relationship between the number of braking operations N and the shoe gap (indicated by a solid line X) or the stroke of the piston member 9 (indicated by a broken line Y). Here, the stroke of the piston member 9 is PS, the shoe gap is SC, the lead of the non-reversible screw 7 is A, the leads of the 1.2 reversible screw 28 and 29 are B and C as described above, and , a=C/A, b
=B/A, PS= (a/ (a+1))XSC When PS≦δ, SC= ((b+1)/b)XPS When PS≧δ, it can be expressed as 5C=PS+ (1/b) can.

As can be seen from the figure, for example, when a=7, b=4, and the operating gap δ-0,5, the shoe gap 5C (2,0 and 0.2), which was significantly different from the initially set value, is As the number of operations N increases, it gradually converges to the set value (1,000), and accordingly, the stroke PS of the piston member 9 converges to the predetermined value (0,875).

In addition, when manually adjusting the shoe gap in this brake wheel cylinder, a tool such as a screwdriver inserted through an opening in the backing plate (not shown) is engaged with the engagement protrusion 13a of the adjuster screw 13, and the adjuster This is done by rotating the screw 13 against the elastic force of the stopper 16 and threading it into or out of the piston member 9.

(Effects of the Invention) As understood from the above explanation, according to the present invention, the following effects can be obtained.

(1) When the air gap becomes larger than the set value due to wear of the brake friction member, it is automatically adjusted to become smaller toward the set value. (If it becomes smaller than the set value, it will be automatically adjusted to become larger towards the set value,
Since the shoe gap is very well maintained at the set value, the brake operation feeling is very good, and the dragging of the brake I2 friction member is also well suppressed.

(2) When the control JI is activated, the adjuster screw screws out from the piston member, so the stroke of the piston member (and the auxiliary piston) becomes smaller than the actual shoe gap. As a result, the responsiveness of brake operation is improved, and it is also advantageous for the durability of the sliding friction portion of the screwdriver member (or auxiliary piston).

(3) The piston member can be used as an anchor because its projection comes into contact with the cylinder body and the return position is restricted, and no braking reaction force is applied to the automatic shoe gap adjustment device. Therefore, it is suitable as a wheel cylinder for a two-leading brake.

[Brief explanation of the drawing]

Fig. 1 is a half sectional view showing one embodiment of the present invention, Fig. 2 is a left side view showing the receiving member, Fig. 3 is a right side view showing the actuating nut, and Fig. 4 is the same. FIG. 5 is a left side view showing the clutch member, and FIG. 6 is a diagram showing the relationship between the number of braking operations N and the shoe gap or the stroke of the piston member. 1 Niji cylinder main body, 2: auxiliary piston, 2a: protrusion,
7: Irreversible screw, 9: Piston member, 9a: Projection, 1
3: Adjuster screw, 13a: Engagement protrusion, 13b:
Recess, 14 Nibble friction member, 15: Receiving member, 15
a: Forked part 216: Stop collar, 19: Clutch member, 2
0: Forward clutch surface, 21: Rearward clutch surface, 24
Niopa travel spring, 25: Threaded portion, 26: Operating nut, 26a: Clutch surface, 27: Operating screw,
27a: Clutch surface, 28: First reversible screw, 29: Second
Reversible screw, 30: first clutch, 32: locking portion, 33:
2nd clutch, 34: 2nd set spring, 35.3
6: Bearing, 3rd: 1st set spring, δ: Operating gap. Agent Patent Attorney Former 1) Hiroshi

Claims (4)

[Claims] (1) A cylinder body, a piston member that is rotatably and slidably fitted into the cylinder body, and whose return position is regulated by the protrusion abutting against the front end surface of the cylinder body, and the piston member. An adjuster screw that is coaxially screwed together with an irreversible screw and supports a brake friction member at the front end, a clutch member that is provided on the inner circumference of the cylinder body and has a forward clutch surface and a rearward clutch surface, and a piston member. The irreversible screw is screwed together with a first reversible screw having a reverse thread, and has a clutch surface that faces the forward clutch surface so as to be able to be connected to and disconnected from the clutch surface to form a first clutch, and has a clutch surface that constitutes a first clutch and is connected to the locking portion of the piston member and the center thereof. an actuating nut that forms an axial working gap in the returned state; a first set spring that is compressed and interposed between the actuating nut and the piston member and biases the frictional connection of the first clutch; an actuating screw that is screwed into the piston member by a second reversible screw having a large lead in the same direction as the first reversible screw, and has a clutch surface that faces the rearward-facing clutch surface so as to be capable of being connected to and disconnected from the rearward-facing clutch surface to constitute a second clutch; The second
A brake wheel cylinder comprising: a second set spring that biases frictional connection of a clutch. (2) The brake wheel cylinder according to claim (1), wherein the clutch member is provided in the cylinder body so as to be movable within a predetermined range in the direction of the central axis, and is biased toward a backward position by an overtravel spring. (3) A brake wheel cylinder according to claim (1) or (2), wherein a cylindrical auxiliary piston is slidably fitted into the cylinder body, and a piston member is rotatably fitted into the auxiliary piston. (4) An annular engaging protrusion is formed on the front end of the adjuster screw, and the free end of the stopper, one end of which is fixed to the cylinder body, is elastically engaged with the engaging protrusion and rotated into the recess of the adjuster screw. Claims (1), (1) wherein the brake friction member is received in the two prongs of the receiving member that is movable and coaxially provided.
The brake wheel cylinder described in 2) or (3).