JPH0511390Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a brake cylinder for a dual-to-leading drum brake.

<Prior art> Fig. 4 shows a conventional brake cylinder a of this type.
An example is shown below.

[Configuration of Conventional Device] A conventional brake cylinder a houses a first piston e and a second piston f in a first cylinder hole c and a second cylinder hole d that are coaxially bored in a body b, By supplying fluid into the fluid chambers A and B formed by communicating between the pistons e and f, the pistons e and f are caused to slide forward, and the pair of pistons e and f that fit into the pistons e and f are moved forward. It has a structure that widens the brake shoe.

Generally, this type of brake cylinder a is configured to be able to automatically adjust the gap between the brake cylinder and the brake drum, which changes as the lining of the brake shoe is worn away.

A conventional automatic gap adjustment mechanism will be briefly explained based on FIG.

That is, the adjusting bolt g is positioned at the axes of the first piston e and the second piston f, and the adjusting bolt g has its upper part connected to the lower half of the first piston e in an irreversible manner (does not rotate due to axial force). At the same time, a substantially nut-shaped drive ring h is attached to the lower peripheral surface of the adjuster bolt g with a predetermined gap in the axial direction so that it can be reversibly rotated (relatively rotated by axial force). A friction clutch is formed between the conical outer peripheral surface of the drive ring h and the conical first clutch surface i at the bottom of the first cylinder hole c.

A spring o is compressed between the upper surface of the drive ring h and the flange of the circumferential surface of the adjusting bolt g, and urges the drive ring h toward the first clutch surface i.

A conical cone j is fixed to the lowest part of the adjuster bolt g, and the conical surface of the cone j is brought into contact with the conical second clutch surface k at the bottom of the first cylinder hole c, thereby creating a friction clutch between both surfaces. , and also regulates the return position of the first piston e.

A locator l and a spring member m surrounding the locator l are housed in the lower axial hole of the cone j and the adjuster bolt g so as to bias both pistons e and f in the direction of separation.

Numeral n denotes an elastic member which is attached around the lower circumferential surface of the cone j, and its outer circumferential portion is in elastic contact with the inner wall of the upper concave portion of the second piston f.

Then, when fluid is supplied into fluid chambers A and B,
The first piston e moves forward together with the adjuster bolt g to expand the diameter of the brake shoe.

At this time, if the lining of the brake shoe is worn out, only the drive ring h rotates while sliding on the first clutch surface i due to the axial force, and retreats from the screwing position on the circumferential surface of the adjuster bolt g. do.

When the brake is released, the first piston e and the adjuster bolt g receive an axial force in the return direction from a shoe return spring (not shown).
retreat as one.

At this time, after the first piston e and adjusting bolt g have retreated by the gap between them and the drive ring h,
The outer peripheral surface of the drive ring h is strongly pressed against the first clutch surface i, increasing its frictional resistance.

On the other hand, the conical surface of the cone j is spaced apart from the second clutch surface k by the amount of rotation of the drive ring h in the axial direction.

Therefore, only the adjusting bolt g is rotated and unscrewed until the conical surface of the cone j comes into contact with the second clutch surface k.

The first
The piston e moves forward to adjust the gap between the brake drum and the brake shoe.

<Problems to be solved by the present invention> Regarding the conventional brake cylinder described above,
There are the following problems.

(a) When automatically adjusting the gap when the conical surface of the cone j separates from the second clutch surface k, as a measure to prevent the adjuster bolt g from inadvertently rotating, a conventional method has been to attach a spring to the locator l as shown in Fig. 5. The friction force of the irreversible threaded engagement between the adjusting bolt g and the first piston e due to the pressing force of the spring member m, and the elastic member n mounted around the lower circumferential surface of the cone j Frictional resistance of the elastic contact part due to the elastic force of (Since the load of the spring member m and the frictional resistance of the elastic member n resist the return force of the shoe return spring, the set value is naturally limited to a small value.) and is given.

However, when large vibrations occur due to brake squeal, sagging phenomenon, etc., it is difficult to reliably prevent the adjustment bolt g from rotating inadvertently, and the reliability of preventing rotation is lacking.

(b) When the brake is not activated, the axial force from the shoe return spring is also acting on the adjuster bolt g, but even in such conditions, if large vibrations are applied to the brake shoe while driving on a rough road, the cone The conical surface of j may separate from the second clutch surface k, and as in (a) above, there is a risk of causing the adjuster bolt g to rotate inadvertently.

(c) If the adjuster bolt g is allowed to rotate inadvertently, the gap between the brake drum and the brake shoe will suddenly increase, causing the pedal to get stuck on the floor of the vehicle during braking or delay in braking. Very dangerous. Further, if the gap between the brake drum and the brake shoe is too clogged, there is a problem in that dragging occurs, leading to premature wear of the brake shoe lining and deterioration of the rubber parts due to temperature rise.

(d) The conventional brake cylinder gap adjustment structure is
Since the adjustment is made by sensing the movement of the piston, which includes the elastic deformation of the brake drum and brake shoe, there is a risk of over-adjustment at high pressures.

In order to prevent this, it is conceivable to set a large gap between the brake drum and the brake shoe when the pressure is low.

However, if this gap is set large, problems arise such as increased pedal stroke and delayed pedal effect.

(E) Since the elastic member n slides every time the brake is applied, its durability is low.

(F) Spring member m, drive ring h, which are small parts;
There are many parts such as the locator l, which makes it difficult to assemble and disassemble.

<Purpose of the present invention> The present invention was created in view of the above problems.
The object of the present invention is to provide a brake cylinder for a drum brake as follows.

(a) A brake cylinder for a drum brake that can reliably prevent accidental rotation of the adjuster bolt and prevent an increase in pedal stroke and drag of the brake shoe, regardless of whether the brake is activated or not.

(b) A brake cylinder for drum brakes that allows the gap between the brake drum and brake shoe to be set small to improve pedal feel.

(c) A brake cylinder for drum brakes that improves the durability of the seal member attached to the adjustment bolt.

(d) A brake cylinder for a drum brake that can reduce the number of parts and facilitate assembly and disassembly.

(E) A brake cylinder for drum brakes that can shorten the overall length of the brake cylinder.

<Structure of the present invention> An embodiment of the present invention applied to a dual-to-leading drum brake will be described with reference to FIGS. 1 and 2.

(a) Overall configuration of drum brake In Figure 2, 10 is a back plate, 1
A pair of brake shoes 1 and 12 are movably mounted on a back plate 10, and have linings 13 and 14 on their outer peripheries.

Numerals 15 and 16 are shoe return springs that draw the brake shoes 11 and 12 inward when the brakes are released, and shoe holding devices 17 and 18 that prevent the brake shoes 11 and 12 from floating up from the back plate 10.

Reference numerals 20 and 21 indicate brake cylinders according to the present invention, which are arranged between the opposing ends of a pair of brake shoes 11 and 12, respectively, rotated 180 degrees with respect to the brake center, and bolted to the back plate 10. etc. to fix it.

In addition, 22 and 23 are the brake shoes 11 and 12, the back plate 10, and the brake cylinders 20 and 2.
A weak spring member stretched between the pistons 1 and 1 has the function of advancing the first piston 40 before the second piston 50.

The point is that the first piston 40 only needs to be provided with a means for moving forward before the second piston.

(b) Brake cylinder The brake cylinders 20 and 21 according to the present invention are:
Since they have the same structure, one brake cylinder 20 will be explained based on FIG. 1.

[Body] Reference numeral 30 denotes a body, which has a first cylinder hole 32 and a second cylinder hole 33 on both sides of the partition wall 31 at the center of its axis, and has a first cylinder hole 32 and a second cylinder hole 33 on both sides of the partition wall 31 at the center of the axis thereof. A bottomed hole 34 is recessed in the center.

The clutch surface 3 is formed on the inclined inner surface of the bottomed hole 34.
6 is formed.

A fluid passage 35 is bored in the partition wall 31 around the bottomed hole 34 in the axial direction thereof, and fluid chambers A and B, which will be described later, are formed.
It communicates between.

A first piston 40 is installed in the first cylinder hole 32,
A second piston 50 is slidably accommodated in the second cylinder hole 33, and fluid chambers A and B are defined between these cylinder holes 32 and 33 and each piston 40 and 50.

[First Piston] The first piston 40 includes a main body 41, a head 42,
It consists of a gear wheel 43 for manual adjustment and an elastic member 45.

The head 42 is substantially integrated with its inclined clutch surface 46 biting into the corresponding clutch surface 47 above the main body 41 under the load of the shoe return springs 15, 16.

A groove for accommodating the brake shoe 11 is provided at the upper end of the head 42.

The elastic member 45 is a member that temporarily fixes the head 42 to the main body 41.

Further, the lower half of the axis of the main body 41 has a bottomed shape,
In addition, a large-diameter stepped hole 48 is formed on the fluid chamber A side.

[Second Piston] A groove 51 for accommodating the brake shoe 12 is provided at the lower end of the second piston 50.

[Nut Member] Reference numeral 60 denotes a cylindrical nut member, which has a reversible female thread 61 on its inner peripheral surface.

The nut member 60 has its uppermost flange portion 6
2 to the stepped surface of the stepped hole 48 so that it cannot rotate relative to the stepped surface of the stepped hole 48,
Moreover, it is pressed and disposed so as to be relatively displaceable in the axial direction.

That is, a coiled spring member 70 is mounted around the shaft portion of the nut member 60, and both ends of the spring member 70 are
It is compressed between the flange portion 62 of the nut member 60 and a retaining ring 80 fixed to the opening side of the stepped hole 48.

In order to restrain the rotation of the nut member 60, one straight portion 71 formed at the end of the spring member 70 is passed through a hole or groove in the flange portion 62, and a blind hole is formed in the hole or groove and in the stepped hole 48. 49, and the other straight portion 72 is tightly fitted into a hole or groove formed in the retaining ring 80.

As another means for restraining the rotation of the nut member 60, a pin is fixed to either the nut member 60 or the main body 41 without forming the straight parts 71, 72 in the spring member 70, and the protruding part of this pin is connected to the other member. It may be fitted into a hole or groove.

[Adjustment bolt] 90 is an adjustment bolt, reversible male thread 91
and a conical clutch surface 93.
It consists of a head 94 having a.

The shaft portion 92 of the adjusting bolt 90 is screwed into the reversible female thread 61 of the nut member 60 with a gap in the axial direction.

Further, a sealing member 95 is provided on the circumferential surface of the head 94 above the clutch surface 93.
is brought into elastic contact with the inner wall of the bottomed hole 34 to form a bottomed cylinder.

The clutch surface 93 is brought into contact with the clutch surface 36 of the bottomed hole 34 to form a friction clutch and to restrict the return position of the first piston 40.

<Operation> Next, the brake operation in the above configuration will be explained.

(a) During braking If fluid is supplied to fluid chamber A now, fluid path 35
It also flows into the fluid chamber B via the .

At this time, when the brake drum is rotating in the direction of arrow C in FIG. The end face is supported by the partition wall 31 and generates braking force.

In addition, when the brake drum is rotating in the opposite direction, the lining 14 is pressed against the brake drum by the advancement of the second piston 50, and the clutch surface 93 of the adjusting bolt 90 of the other brake cylinder 21 is pressed against the bottomed hole 34. It is supported in contact with the clutch surface 36 and generates braking force.

(b) When not braking When the brake is released, the brake shoe 11,
12 etc. returns to almost its original position by the return force of the shew return springs 15 and 16.

(c) Automatic gap adjustment operation When the first piston 40 starts moving forward, the nut member 60 and the spring member 70 follow it together.

At this time, if the lining 13 of one of the brake shoes 11 is worn out, the forward stroke of the first piston 40 will reduce the axial clearance (backlash amount) at the threaded portion of the reversible male thread 91 and the reversible female thread 61. ), adjust bolt 90
The adjusting bolt 90 is rotated along the slope of the reversible internal thread 61 and unscrewed by the fluid pressure acting on the bottomed cylinder due to slipping on the clutch surface 93 of the bolt.

When the fluid pressure reaches a predetermined pressure, the axial force acting on the bottomed cylinder overcomes the spring force of the spring member 70, and the frictional force between the clutch surfaces 36 and 93 increases, making it impossible for the adjustment bolt 90 to rotate. , the spring member 70 is bent and the automatic adjustment action is stopped.

Therefore, the brake drum and brake shoe 11
The clearance adjustment amount is determined by adjusting the adjustment bolt 9 at low pressure.
0 is only the amount of displacement in the axial direction that is unscrewed.

When the brake is released, the first piston 40, nut member 60, etc.
5 and 16, the clutch surface 93 of the adjusting bolt 90 bites into the clutch surface 36 of the bottomed hole 34 to support the axial force.

<Other Modifications> FIG. 3 is a modification of FIG. 1, in which the vertical arrangement of the clutch surface 193 formed below the adjusting bolt 190 and the seal member 95 forming the bottomed cylinder hole is reversed. It is something.

Since the configurations other than those described above are the same as those of the previous embodiment, their explanation will be omitted.

<Effects of the present invention> Since the present invention is as described above, it has the following effects.

(b) Not only when the brake is applied, but even when the brake is not applied, the residual pressure of a fluid pressure generating device installed in the fluid path, such as a master cylinder device, acts on the bottomed cylinder of the adjustment bolt. , it is possible to reliably prevent the adjuster bolt from rotating inadvertently.

Therefore, it is safe without increasing the pedal stroke or causing the brake shoe to drag.

(b) When the frictional force on the clutch surface of the adjusting bolt increases, the adjusting bolt becomes unable to rotate, so the adjustment device does not sense elastic deformation of the brake drum, brake shoe, etc.

Therefore, the gap between the brake drum and the brake shoe can be set small, and the pedal feeling is improved.

(c) Since the adjustment bolt hardly moves in the axial direction, the durability of the seal member attached to the adjustment bolt is improved.

(d) Since the number of parts is small and all adjustment parts are assembled to the piston, assembly and disassembly of the brake cylinder is easy.

(E) Since the partition wall provided between a pair of cylinder holes has an anchor function and a flow path is provided in this partition wall to communicate both cylinder holes, the overall length of the brake cylinder can be shortened, especially for small drum brakes. suitable.

[Brief explanation of the drawing]

Fig. 1: A sectional view of a brake cylinder showing an example of the present invention, Fig. 2: A plan view of a drum brake, Fig. 3: A sectional view of a brake cylinder showing a modification of Fig. 1, Fig. 4: A conventional Cross-sectional view of the brake cylinder, FIG. 5: An enlarged view of the components of a conventional brake cylinder.

Claims (1)

[Claims for Utility Model Registration] A partition wall that slidably accommodates a pair of first and second pistons in first and second cylinder holes bored in a body, and partitions each of these pistons and each cylinder hole. In a brake cylinder of a dual-to-leading type drum brake in which a fluid chamber is formed by a nut member, the nut member is placed in a bottomed hole provided at the bottom side of the axis of the first piston, so that the nut member is non-rotatable but movable in the axial direction. At the same time, the nut member is urged in the forward direction of the first piston by the spring member, and the shaft portion of the adjusting bolt is reversibly screwed into the nut member. is engaged with a clutch surface provided on the first cylinder hole side of the partition wall to form a friction clutch, and this shaft portion is fitted with a shaft portion of the adjusting bolt adjacent to the clutch surface of the head of the adjusting bolt. A brake cylinder in a dual-to-leading type drum brake, wherein a bottomed cylinder is formed with a bottomed hole in a mating partition wall, and a flow path communicating both fluid chambers is provided in a partition wall around the bottomed hole. .