JPS6053229A - Disc brake equipped with parking brake mechanism - Google Patents

Abstract

PURPOSE:To prevent a drag without increasing the clearance in a screw part by making possible a relative rotation between a key brake and a push rod. CONSTITUTION:A favorably formed hole capable of rotating within a certain width is formed on. The middle part of a key plate 15 so that a push rod 8 may engagine with said hole can axially slide through the key plate 15. Thus, when deflections of pads 19, 19' and a caliper 1 begin to be rostored at the time of releasing hydraulic pressure and in a moment a push rod 8 is pressed on a sleeve 4, a key 15 and a push rod 8 relatively rotate, and the axial positions of the push rod 18 and the sleeve 4 are changed. At and this time, as the restoring displacement of the bads 19, 19' and caliper 1 can be absorbed, a drag can be prevented without increasing the clearance of a screw part.

Description

DETAILED DESCRIPTION OF THE INVENTION A) Field of Industrial Application This invention relates to a disc brake with a parking brake mechanism incorporating a pad wear compensation mechanism.

2. Description of the Related Art Disc brakes incorporating a parking brake mechanism, so-called built-in type disc brakes with a parking brake mechanism, have been known for a long time.

FIG. 1 shows an example of the prior art, and this disc brake has a piston 3 inside a cylinder 2 provided in a caliper 1.
A tapered surface is formed on the inner surface of the piston 3, and the sleeve 4 is pressed into the piston 3 by the ring 7, so that the piston 8 and the tapered surface of the sleeve 4 are brought into close contact with each other.

The sleeve 41C is provided with a multi-start thread (female thread) with a large lead, and a bushing rod 8 having a similar male thread is threadedly engaged with the sleeve 4. The rear end of the bushing rod 8 faces the camshaft 9 inserted into the caliper l in a direction perpendicular to the rear end of the bushing rod 8, and the recess lO provided in the bushing rod 8 and the cam surface 11 of the camshaft 9 are connected to each other. A strut 12 is sandwiched between them.

The above-mentioned camshaft 9 is rotatably supported by a needle bearing +31C in which the portion through which the strut 12 passes is open, and one end of the camshaft 9 is coupled to an operating lever 14.

The central portion VtC of the bushing rod 8 is connected to the key plate 1.
5 is fixed in a non-rotatable but slidable manner and held in the key brake.

In addition, in FIG. 1, 19 and 19' are brake pads, 20 is a piston seal, and 21 is an O-ring.

Next, the operation will be explained. In the disc brake, when the parking brake lever is operated, force is transmitted to the operating lever 14 via the cable, rotating the camshaft 9 connected to the operating lever 14, and pushing the bushing rod 8 via the strut 12. The bushing rod 8 presses the sleeve 4 through its threaded portion, and the sleeve 4 presses the piston 3 with its tapered surface.

The brake pad 19 is attached to the disc 21 by the piston 3.
The opposing pads 19' are attracted by this reaction, and a braking force is generated by sandwiching the disc between these two pads.

The pad is returned to its original position, the pad pressing force is released, and the braking force is released.

In addition, in order to prevent the pedal stroke and parking brake operation stroke during hydraulic pressure operation from increasing even if the pads 19 and 19' wear out, a function is provided to move the position of the piston 3 according to the pad wear, that is, a pad wear compensation function. Motsu. This is because when the pads +9 and 19' wear out and the gap between the disk and the pad increases, the piston 31d moves in the direction of pressing the pad by applying hydraulic pressure, and at this time the sleeve 5 rotates. By,
The relative position of the sleeve 5 with respect to the bushing rod 8 changes, and the position of the piston 3 when hydraulic pressure is released changes, thereby keeping the pad clear runne constant. As mentioned above, the sleeve 4 and bushing rod 8 are threadedly engaged, but it is necessary to provide a large clearance in the axial direction of the threads.
Practically speaking, about 0.4 to 0.5 am is required. The reason for this is that the pad and caliper are deflected by the hydraulic load, and the sleeve rotates by the amount of deflection, changing the piston position.
This is because when the hydraulic pressure is released from this state, the pad or caliper cannot return to its original state, and the pad remains in a state where the Dinuk is held between them, that is, drag occurs.

c) The problem to be solved by the present invention is that increasing the clearance between the screw retaining portions of the sleeve 4 and the bushing rod 8 causes the screw to become numb, which is not desirable from the viewpoint of strength. Therefore, it is preferable to prevent dragging while keeping the clearance of the threaded portion small.

5- One way is to increase the rigidity of the pad and the pad, but this increases the stiffness and weight, which poses problems.

2) Means for Solving the Problems In order to solve the problems described in 2 above, the present invention has a structure that allows relative rotation by a certain width between the key plate 15 and the bushing rod 8. By doing this,
Drag can be prevented without increasing the clearance of the threaded part.

The reason for this will be explained below.

Relative rotation of the bushing rod 8 with respect to the key plate 15 also means rotation with respect to the sleeve 4, and means movement of the relative positions of the sleeve 4 and the bushing rod 8 in the axial direction.

Therefore, when the pad and caliper are about to return to their original position when the hydraulic pressure is released, the bushing rod 8 is pressed against the sleeve 4 and rotates within the permissible range of relative rotation between the key brake +5 and the bushing rod 8. According to
The axial positions of the bushing rod 8 and sleeve 4 change,
Since the restoring displacement of the pad and caliper is absorbed, it is possible to prevent the occurrence of dragging that would cause the head to close.

E) Embodiment The present invention is applied to, for example, the conventional disc brake with parking brake mechanism shown in FIG.
FIG. 2 shows a conventional example of the part according to the present invention, and FIG. 3 shows an example of the present invention.

A hole of any desired shape is formed in the center of the key plate 15 into which the bushing rod 8 can be inserted, and the bushing rod 8 can slide in the axial direction with respect to the key plate 15 and can rotate by a certain width. By providing two planes parallel to the insertion portion, it is possible to slide on the key plate and rotate by a certain width.

(f) Effect Since the present invention has the above-described structure, it is possible to prevent drag without intentionally increasing the axial clearance of the sleeve and bushing rod engaging threaded portion, and without increasing the rigidity of the pad or caliper unnecessarily. It is possible to provide a disc brake with a parking brake mechanism that can hold down the parking brake to a small value.

[Brief explanation of drawings]

FIG. 1 is an overall cross-sectional view of a conventional example, FIG. 2 is a cross-sectional view of a portion according to the present invention of a conventional example, and FIG. 3 is a cross-sectional view of an embodiment of a portion according to the present invention. 1... Caliper, 2... Cylinder, 8... Piston, 4... Sleeve, 8... Bush rod, 15...
・Key plate.

Claims (1)

[Claims] +11 The brake pad has a sleeve that is secured to the piston for operating the brake pad, and a bushing rod that is threadedly engaged with the sleeve and adjusts pad wear together with the sleeve. A disc brake with a parking brake mechanism characterized by a structure that allows relative rotation by a width of .