JP3371617B2 - Disc brake - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc brake in which a friction pad is pressed against a disc by a hydraulically actuated piston. More specifically, the present invention relates to a disc brake that prevents the piston from twisting in the cylinder during braking and reduces scratches on the piston and the cylinder and so-called squeal of the brake.

[0002]

2. Description of the Related Art A disc brake for a vehicle is one in which a piston inserted in a cylinder of a caliper is propelled by a hydraulic pressure supplied from a master cylinder, and this force is used to press a friction pad to make sliding contact with the disc. It is common.

In the floating disc brake shown in FIG. 5, the friction pad is pressed by pressing the inner pad 4 against the disc D by the piston 3 and the reaction force of the inner pad 4 slides toward the inner side (the side with the piston) of the caliper 1. The outer pad 5 is pressed against the disc D by the outer claw 1a. Further, each pad is supported by a torque member 6 shown in FIG. 5B so as to be slidable in the disc axial direction, and a torque receiving portion 6a of the torque member 6 receives a braking torque from the pad to stop the rotation of the disc.

On the other hand, in a piston-opposed disc brake, a pair of friction pads are separately pressed by opposed pistons. In this system, the caliper also serves as the torque member, and the friction pad is supported by the pad pin that is laid across the window hole of the caliper so that it can slide in the disc axial direction.
The braking torque from the pad is received by the torque receiving portion formed on the caliper.

In any case, as shown in FIG. 5A, in the case where the pad is pressed by the hydraulically actuated piston, the clearance g for sliding the piston is provided between the piston 3 and the cylinder 2 into which it is inserted. ₁ is provided. The clearance g ₁ is represented by (cylinder diameter d ₁ −piston diameter d ₂ ), and when not braking, the piston seal 7 causes the piston 3 to move.
Are held concentrically with the axial center of the cylinder 2, so that a gap of g _1/2 is created over the entire circumference of the piston.

On the other hand, the pad is also provided with clearances g ₂ and g ₃ (see FIG. 5 (b)) between the pad and the torque receiving portion 6a so as to be interlocked with the axial movement of the piston. In the piston-opposed brake, a clearance g _{3 in} the disc radial direction is secured between the pin hole provided in the pad and the pad pin.

Of the above three clearances,
g _2, g ₃ is the dimensional tolerance of the pad from the preparation surface is a piston, and the defined greater than the cylinder, it is necessary to some extent from the viewpoint of sticking prevention by mud and rust pad.

On the other hand, g ₁ is unlikely to rust the piston sliding surface due to protection by the piston boot 8 of FIG. 5 (a). It is necessary to make it as small as possible.

For the above reasons, the size of each clearance is usually set to g ₁ <g ₂ and g ₁ <g ₃ .

[0010]

The clearances g ₂ and g ₃ described above serve as a movement allowance of the pad during braking. Here, there pad centered during non-braking, the pad movement amount from there to the two directions as the movement begins g _2/2,
g _3/2 to think, but in this way the pad is displaced,
The tip portion of the piston 3 pressed against the pad 4 moves by being dragged by the pad. At this time, the piston 3 is g ₁ /
When it moves two times, it hits the inner wall of the cylinder 2 and is further dragged from here, so that it tilts as shown in FIG.

As a result, the outer circumference of the piston and the inner surface of the cylinder may be damaged, or the contact pressure of the piston seal 7 with respect to the piston may fluctuate to cause liquid leakage. Further, in the state of FIG. 6, the piston 3 is unevenly contacted with the pad 4, so that the surface pressure distribution of the pad becomes non-uniform, which causes uneven wear of the pad and squeaking during braking.

An object of the present invention is to provide a disc brake which is devised to solve these problems.

[0013]

In order to solve the above problems, in the present invention, a shim is provided between a hydraulically operated piston included in a pad pressing mechanism and a friction pad pressed by the piston. The disc tangential clearance g ₄ and the disc radial clearance g ₅ between the shim and the torque receiving surface provided on the torque member or the caliper are provided.
Is the clearance g ₁ between the piston and the cylinder.
Smaller than.

It is to be noted that the shim is provided with an elastic piece which comes into contact with the torque receiving portion and makes the clearance g ₄ zero, and an elastic piece which makes the clearance g ₅ zero, or the elastic piece is attached to the shim. It is extremely preferable to provide only the torque transmitting portion when the disc is rotated in the reverse direction for the reason described later.

[0015]

In the present invention, the size relationship of each clearance is g
_{Since 4} <g ₁ <g ₂ and g ₅ <g ₁ <g ₃ ,
Before the friction pad is dragged by the disc and touches the torque receiving portion, the shim dragged by the pad touches the torque receiving portion and stops. The piston is in contact with the shim and cannot be dragged further if the shim stops. Pad is
Even after the shim stops, it moves until it hits the torque receiving part, but this movement is absorbed by the relative movement with the shim and is not transmitted to the piston. Therefore, the amount of piston displacement during braking = the amount of shim displacement, and the clearances g ₄ and g that allow the displacement of the shim.
_{Since 5} is smaller than g ₁ , the piston will not be twisted in the cylinder.

Incidentally, it is very difficult to make the size of the shim so that the shim fits closely to the torque receiving portion. Further, even if it is possible, this does not guarantee that the shim will move reliably in the disc axial direction.

On the other hand, in the case where the shim is provided with an elastic piece and the elastic piece is elastically brought into contact with the torque receiving portion, elastic deformation of the elastic piece maintains the slidability of the shim and the clearances g ₄ and g ₅ are maintained. Can be zero. This g ₄ , g ₅
The smaller the value, the smaller the amount of piston drag due to the shim, so the addition of an elastic piece further enhances the effect of preventing twisting of the piston.

Further, the elastic piece is elastically deformed when a braking torque is applied, and the shim moves accordingly. Therefore, when the elastic deformation amount becomes larger than the cylinder clearance, the piston is twisted, and this is prevented. In order to achieve this, it is preferable to provide the torque receiving portion only at a portion that transmits the braking torque when the disc rotates in the reverse direction. In this case, the shim displacement due to the deformation of the elastic piece can be prevented, although it is limited when the disc rotates in the normal direction. It

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an outline of an example of the disc brake of the present invention. In this figure, the clearance portion is exaggerated for easy understanding of the contents of the invention. As shown in the figure, the piston 3 inserted into the cylinder 2 of the caliper 1
A shim 9 is interposed between the friction pad and the friction pad (inner pad 4 in the figure) that is pressed by the piston and slid on the disk D. Although such a shim has been conventionally used, the conventional shim has a clearance between the shim and the torque receiving portion of the torque member 6 which is equal to or larger than that of the pad.

In the present invention, the shim 9 and the torque member 6 are provided.
The disc tangential clearance g ₄ with respect to the torque receiving portion 6 a and the disc radial clearance g ₅ are smaller than the clearance g ₁ between the piston 3 and the cylinder 2.

[0021] g ₄ is, but never hurts to it is smaller than g _1/2, non-braking when the disk rotation entrance side and the run-out of the g _4/2, respectively in side clearance is secured, g ₄ /
If 2 <g _1/2 is set, the effect of the invention can be obtained even if it is larger than g _1/2 . As shown in FIG. 4, a plurality of pawls 10 are provided on the back surface of the shim 9, and the pawls 3
If the relative position of the shim 9 and the piston 3 is kept by a method such as locking the inner surface of the shim 9, the shim 9 is returned to the center of the cylinder at the time of depressurization, so that the shim 9 is moved in and out of the disk. can be positioned at a position of the clearance respectively to the side g _4/2 is maintained.

The same applies to the clearance of g ₅ . Each g _5/2 clearance between the two surfaces for restraining the movement of the disk radial direction of the shim 9 is maintained,
g _5/2 <Once you have in such a way that _{g 1/2, g 5 <} g 1 /
It need not be 2.

Further, as shown in FIG. 2, when an engaging portion (torque transmitting portion) of the shim 9 with the torque member 6 is provided with an elastic piece 11 which elastically contacts the torque receiving portion, g ₄ and g ₅ are provided.
It is possible to further reduce the movement of the shim 9 during braking by reducing the clearance of zero.

The elastic piece 11 is shown in FIG.
An example is shown in which the clearance g _{4 in the} tangential direction of the disk is made zero by contacting the torque receiving surface of a. Similarly, the clearance g _{5 in} the disk radial direction in FIG. 1B can be made zero by installing the elastic piece 11.

Since the elastic piece 11 is elastically deformed when a braking torque is applied, it causes a movement allowance of the shim 9.
It is preferable to provide it only on the torque reaching portion when the disc is rotated in the reverse direction. For example, among the elastic pieces of FIG. 2, 11a, 11b, 1
By omitting this for 1c, the torque transmitting portion of the shim 9 at the time of normal rotation of the disk serves as the edge of the shim, and if this edge is brought into direct contact with the torque receiving surface, the shim displacement due to elastic deformation of the elastic piece at the time of normal rotation of the disk will occur. It becomes more preferable because it disappears.

Further, the elastic piece 11 elastically deforms when the distance between the opposed torque receiving surfaces fluctuates to absorb the fluctuation amount, and guarantees the reliable sliding of the shim. Since the sliding resistance that occurs at the piston tries to remain in the push-out position by the piston even after decompression, in order to prevent the pad from being dragged by the disc, the shim 9 is provided to the piston 3 as shown in FIG.
It is preferable that the pad 4 is forcibly pulled back by the piston 3 or the pad 4 is pushed back by a spring as usual.

[0027]

As described above, according to the present invention, a shim having a permissible motion allowance smaller than the clearance between the piston and the cylinder is interposed between the piston and the pad pressed by the piston, and the shim is applied during braking. Since the piston displacement due to dragging occurs within the above-mentioned clearance range, the piston is prevented from being twisted, and scratches on the piston outer circumference and cylinder inner surface due to the twisting, liquid leakage from the cylinder, and uneven pad wear , Squeaking during braking is effectively prevented.

The one in which the elastic piece is provided on the shim to eliminate the clearance between the torque receiving portion and the shim, and the one in which the elastic piece is provided only in the torque transmitting portion at the time of reverse rotation of the disk,
The movement of the shim is further reduced, and the effect of the invention is further enhanced.

[Brief description of drawings]

FIG. 1A is a cross-sectional view showing an outline of a main part of a first embodiment, and FIG. 1B is a front view showing a relationship between clearances of shims, pads and torque members.

FIG. 2 is a perspective view of another example of the shim.

FIG. 3 is a cross-sectional view showing a usage state of the shim of FIG.

FIG. 4 is a sectional view showing an example in which a shim is locked to a piston.

FIG. 5 (a) is a side view sectional view showing an outline of a floating disc brake, and FIG. 5 (b) is a plan view sectional view of the same brake.

FIG. 6 is a view showing a state where the piston is twisted.

[Explanation of symbols] 1 caliper 1a outer claw 2 cylinder 3 piston 4 inner pad 5 outer pad 6 torque member 6a torque receiving portion 7 piston seal 8 piston boot 9 shim 10 locking claw 11 elastic piece g ₁ between piston and cylinder Clearance g ₂ Disc tangential clearance between pad and torque receiving part g ₃ Disc radial clearance between pad and torque receiving part g ₄ Disc tangential clearance between shim and torque receiving part g ₅ Disc between shim and torque receiving part Radial clearance

Claims (3)

(57) [Claims] 1. A press including a hydraulically actuated piston inserted in a cylinder of a caliper, which supports a pair of friction pads opposed to each other with a disk interposed therebetween by a pad pin attached to a torque member or a caliper so as to be slidable in the axial direction of the disk. In the disc brake, the mechanism presses the pair of friction pads against the disc, and the torque receiving portion provided in the torque member or the caliper receives the braking torque from the friction pad, and a shim is provided between the friction pad and the piston. A disc brake, wherein a disc tangential direction clearance g ₄ and a disc radial direction clearance g ₅ between the shim and the torque receiving portion are smaller than a clearance g ₁ between the piston and the cylinder. 2. The disc brake according to claim 1, wherein the shim is provided with an elastic piece that is in contact with the torque receiving portion and that makes the clearance g ₄ zero, and an elastic piece that makes the clearance g ₅ zero. 3. The disc brake according to claim 2, wherein the elastic piece is provided only in a torque transmitting portion of the shim when the disc is reversed.