JPH0354991Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an overtravel device applied to an auto-adjuster device for a drum brake.

(Prior Art) As a drum brake equipped with an auto-adjuster device, there is a dual servo brake shown in FIG.

11 is a bucking plate, 12 is a wheel cylinder, and 13 are pistons, each of which has a brake shoe 14, 15 at its outer end. 16 is pin 1 installed on the brake shoe 14
4a, and is engaged with the adjuster gear 17 so as to be able to feed in only one direction. 18 is a return spring for the adjuster lever 16. The adjuster gear 17 is formed integrally with an adjuster screw 17a, and one end of the adjuster screw 17a is connected to the other brake shaft 1.
5, and the other end is rotatably fitted into an adjuster socket 19 that is locked to one of the brake shoes 14.
Adjustment star screw 17a, adjustment star gear 1
7. The adjuster nut 20 and adjuster socket 19 constitute an adjuster member 21.

Between the anchor block 22 fixed to the bucking plate 11 and the adjuster lever 16, there is a plate-shaped rocking plate having a through hole 23a in the center and locking holes 23b and 23c at both ends. Link 2
3 is pivotally supported in the through hole 23a by a fixing pin 14b standing upright on the web of one brake shoe 14, and is swingably mounted thereon.
4 is hooked into the through hole 25a provided at one end of the fitting 25, and the hook portion at the other end is hooked into the recess 25b at the other end of the fitting 25 and the through hole 16a of the adjuster lever 16. Stop,
An initial tensile load is applied to the spring 24. The other end of the upper link 26, which is connected to an anchor pin 22a whose one end is fixed to the anchor block 22, is hooked to one of the hook holes 23b of the swing link, and the other end of the upper link 26 is hooked to the other hook hole 23c. One end of a lower link 27 is connected to the adjuster lever 16 via a fitting 25, and the other end of the lower link 27 is latched.

Both brake shoes 14 and 1
5 return coil spring, 29 both brake shoes 1
4 and 15 are coil springs that position the adjuster member 21, 30 is a parking lever, and 31 is a strut that transmits the reaction force of the parking lever 30 to one brake shoe 14.

In the drum brake configured as described above, when the brake is applied while the wheel is rotating in the direction of arrow A, the anchor pin 22a and the fixed pin 14b
The relative dimension between the swing link 23 and the upper link 26 becomes longer, and the swing link 23 is pulled by the upper link 26 and rotates around the fixing pin 14b in the direction of arrow B. As a result, the fitting 25 is pulled, and the adjuster lever 16 is moved toward the pin 1.
4a, if the shoe clearance is below a predetermined value, the adjuster lever 16 will not rotate the adjuster gear 17, and if the shoe clearance is greater than the predetermined value, the adjuster lever 16 will not rotate. The rotation angle becomes large, and normally, without extending the tension type overtravel spring 24, the adjuster gear 17 is operated and the adjuster screw 17a is screwed out to automatically adjust the shoe distance.

By the way, in the case of sudden braking, when the axial force of the adjuster screw 17a on the adjuster nut 20 increases and the adjuster lever 16 cannot rotate, the tension type overtravel spring 2
4 is stretched. In this way, the fixing pin 14
b. This prevents deformation and damage to the swing link 23, fitting 25, adjuster lever 16, etc.

(Problems to be Solved by the Invention) In the overtravel device consisting of the fitting 25 and the tension type overtravel spring 24 as described above, the fitting 25 or the adjuster is formed at both ends of the spring 24. The stress on the hook part that engages the lever 16 becomes large, making it impossible to set a high load, and when the spring 24 is incorporated into a large drum brake, the spring 24 may break.

(Means for Solving the Problems) The present invention provides an overtravel device applied to a durable auto-adjuster device of a drum brake, and its configuration is as follows. It is interposed between an operating member whose one end is connected to an anchor pin fixed to the bucking plate of the drum brake, and an adjuster lever that is rotatably supported on the brake shoe and operates the adjuster member, and has both ends. In an overtravel device in which a connecting portion provided on the side is connected to an operating member or an adjuster lever, and the overload applied to the adjuster lever is absorbed by extension, an inward flange portion is provided on one end and an inward flange portion is provided on the other end. A compression-type coil spring is housed in a cylindrical case with a connecting part formed at each side, a spring seat at one end, a stopper locking part at the middle part, and a connecting part at the other end. Insert the fitting into the coil spring, attach the stopper to the stopper locking part, lock it to the inward flange part, and apply initial pressure to the coil spring between the spring seat and the inward flange part. This is an overtravel device for drum brakes.

(Function) Therefore, when the operating member is pulled during control and the fitting is pulled and the shift distance is within the normal shift distance, the adjuster lever is operated, but the adjuster gear is not rotated. do not have. If the show distance exceeds the regular show distance, normally the rotation of the adjuster lever becomes large, the adjuster gear is rotated, and the show distance is adjusted by the adjuster member.

When the operating member is strongly pulled, as in the case of sudden braking, the pressure applied to the compression type coil spring exceeds the initial pressure, and the coil spring is forced into contact with the spring seat of the fitting and the inward flange of the case. The overtravel device is compressed between sections to extend the entire length of the overtravel device.

(Embodiment) An embodiment of the drum brake overtravel device according to the present invention will be described based on the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a dual servo brake, and the same reference numerals as in FIG. 3 indicate the same parts.

A through hole 23a is provided in the center, and latching holes 23 are provided at both ends.
A plate-shaped swinging link 23 having a number b and 23c is pivotally supported in the through hole 23a by a fixing pin 14b standing upright on the web of one brake shoe 14, and is swingably attached to one of the brake shoes 14. In the through hole 23b,
Anchor pin 22a installed on the anchor block
The other end of the upper link 26 is hooked to the upper link 26, and the other end of the lower ring 27 is fixed to the fitting 3 of the overtravel device 1, which will be described later. is hanging. Here, the upper link 26 and the swing link 2
3 constitutes an operating member.

As shown in FIG. 2, the overtravel device 1 consists of a case 2, a fitting 3, and a compression type coil spring 4.

The case 2 has a cylindrical shape, and has an inward flange portion 2a at one end and a flat arm 2b serving as a connecting portion at the other end, and the arm 2b is provided with a pin insertion hole 2b'. be.

The fitting 3 has a rod shape, and the other end has a
A lower link 27 serving as a connecting portion is fixed, a spring seat 3a is formed at one end, and an annular retaining ring groove 3b is formed at an intermediate portion. In this embodiment, the lower link 27 serving as a connecting portion is fixed by inserting the other end of the lower link 27 into a hole 3c provided at one end of the fitting 3 and crimping it.

After the compression type coil spring 4 is inserted into the case 2,
Insert the tip of the fitting 3 into the inward flange part 2.
It is inserted into the through hole formed by a and compressed between the inward flange portion 2a and the spring seat 3a, and an initial pressure is applied by inserting the retaining ring 5 into the retaining ring groove 3b.

Reference numeral 16 denotes an adjuster lever that is rotatably supported by a pin 14a that is provided upright on the web of one brake shoe 14 and has the same function as the conventional one.
It is connected to the arm 2b which is a connecting part of the case. Specifically, the pin insertion hole 1 is provided in the adjuster lever 16.
6a and a pin insertion hole 2 provided on the arm of the case.
A pin 6 is inserted into b' and the pin insertion hole 16a, and a retaining ring 6a is inserted into a retaining ring groove provided in the pin 6 and fixed.

Next, the effect will be explained.

When the brake is applied while the wheel is rotating in the direction of arrow A, if the shoe clearance is less than a predetermined value, the adjuster gear 17 is not rotated as in the conventional example.

When the shoe clearance is above a predetermined value, the adjuster gear 17 is normally operated without compressing the compression type coil spring 4, and the adjuster gear 17a is screwed out to automatically adjust the shoe clearance. .

In addition, in the case of sudden braking, the swing link 23 swings greatly, the fitting 3 is strongly pulled, and the adjuster nut 2 of the adjuster screw 17a
The axial force relative to 0 increases, and the screw 17a
If rotation of the spring is impossible, the tensile force exceeds the set initial pressure of the compression type coil spring, and the spring is compressed between the spring seat 3a of the fitting and the inward flange 2a of the case. Thus, the entire length of the overtravel device 1 is extended.

The initial pressure of the compression type coil spring can be set appropriately by inserting washers of different thickness between the inward flange 2a of the case and the retaining ring 5. It is not limited to.

The present invention is a drum brake assembly having an operating member (operating wire) whose one end is fixed to an anchor pin fixed to a bucking plate and whose middle part is guided by a guide member erected on the brake shoe web. Of course, it can also be used for operating star levers.

(Effect of the invention) As understood from the above explanation, according to the drum brake overtravel device of the present invention, the shoe distance is within or exceeds the regular shoe distance. During normal braking, the brake operates in the same manner as in the past, and in the case of sudden braking, the compression type coil spring is compressed and the overtravel device operates. Moreover, the compression-type coil spring without a hook portion is difficult to break, improving the durability of the overtravel device and, in turn, significantly improving the reliability of the auto-adjuster device.

Furthermore, by interposing a washer of an appropriate thickness between the inward flange of the case and the stopper, the initial pressure of the compression type coil spring can be easily adjusted and set.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a dual servo brake to which a drum brake overtravel device according to an embodiment of the present invention is applied, and FIG. 2 is a diagram showing A-A in FIG.
The line sectional view, FIG. 3, is a diagram showing a dual servo brake to which a conventional drum brake overtravel device is applied. 1... Overtravel device, 2... Case, 2
a... Inward flange portion, 2b... Arm, 3... Fitting, 3a... Spring catch, 3b... Retaining ring groove, 4... Compression type coil spring, 5... Retaining ring (stopper) , 11...bagging plate, 14...
...(one) brake shoe, 14a...pin,
14b... Fixed pin, 16... Adjuster lever, 17... Adjuster gear, 21... Adjuster member, 23... Swing link, 23a... Through hole,
23b, 23c...Latching hole, 26...Upper link, 27...Lower link.

Claims (1)

[Scope of utility model registration request] It is interposed between an operating member whose one end is connected to an anchor pin fixed to the bucking plate of the drum brake, and an adjuster lever that is pivotably supported on the brake shoe and which operates an adjuster member, and has both ends. In an overtravel device in which a connecting portion provided on the side is connected to an operating member or an adjuster lever, and the overload applied to the adjuster lever is absorbed by extension, an inward flange portion is provided on one end and an inward flange portion is provided on the other end. A cylindrical case with connecting parts formed on each side,
A fitting that accommodates a compression type coil spring and has a spring seat at one end, a stopper locking part in the middle, and a connecting part at the other end is inserted into the coil spring and the stopper locks. 1. An overtravel device for a drum brake, characterized in that a stopper is attached to the inward flange, and the coil spring is applied with initial pressure between the spring seat and the inward flange.