JPH0412263Y2 - - 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.

Reference numeral 11 is a bucking plate, 12 is a wheel cylinder, and 13 are pistons. Brake shoes 14 and 15 are engaged with each outer end of the piston 13. Reference numeral 16 designates an adjuster lever that is pivotably supported by a pin 14a provided upright on one brake shoe 14, and is engaged with the adjuster gear 17 so as to be able to move 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, the other end of the adjuster screw 17a is screwed into an adjuster nut 20 that locks on the other brake shoe 15, and one end is connected to the other brake shoe 14. Adjuster socket 19 that locks into
The adjuster screw 17a, the adjuster gear 17, the adjuster nut 20, and the 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 plate having a through hole 23a formed in the center and locking holes 23b and 23c formed in both ends. A swing link 23 is pivotally supported in the through hole 23a by a fixing pin 14b provided upright on the web of one brake shoe 14, and is swingably mounted. Further, as an overtravel device, a hook portion at one end of a tension type overtravel spring 24 is hooked into a through hole 25a provided at one end of the fitting 25, and a hook portion at the other end is inserted into a recess at the other end of the fitting 25. 25b and the through hole 16a of the adjuster lever 16 to apply an initial tensile load to the spring 24. One latching hole 2 of the swing link 23
3b, the other end of an upper link 26, which is an operating member connected to an anchor pin 22a whose one end is fixed to the anchor block 22, is hooked, and the other end of the upper link 26 is hooked to the other hooking hole 23c. One end of a lower link 27 connected to the adjuster lever 16 via the lower link 27 is latched.

Each 28 is a coil spring returned to each brake shoe 14, 15, and 29 is a coil spring for both brake shoes 1.
4 and 15 are shoe 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 a drum brake configured as above,
When the brake is applied while the wheel is rotating in the direction of arrow A, the anchor pin 22a and fixed pin 14
b becomes longer, the swinging link 23 is pulled by the upper link 26, rotates around the fixed pin 14b in the direction of arrow B, and the fitting 25 is pulled, pulling the adjuster lever 16 into the pin position. 14a. If the shoe clearance is less than a predetermined value, the adjuster lever 16 will not rotate the adjuster gear 17, and if the shoe clearance exceeds the predetermined value, the rotation angle of the adjuster lever 16 will be large, and normally The shoe gap is automatically adjusted by operating the adjuster gear 17 and screwing out the adjuster screw 17a without extending the tension type overtravel spring 24.

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 expands. In this way, the fixing pin 14
b. Deformation and damage to the swing link 23, fitting 25, adjuster lever 16, etc. are prevented.

(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 portion 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.

A connecting part provided at both ends, interposed between an operating member that connects one end to the bucking plate side of the drum brake and an adjuster lever that is pivotably supported by the brake shoe and that operates an adjuster member. is connected to the operating member and the adjuster lever, and is locked at one end or the other end in a drum brake overtravel device that absorbs the excessive load acting on the adjuster lever via the operating member by extension. a case provided with a section, a coil spring inserted into the case, a fitting through which the coil spring is inserted and a spring seat formed at the other end, and one end of the fitting or the case through which the fitting is inserted. A screw member is formed at the other end of the case and at one end of the fitting, the screw member being screwed into the coil spring such that the amount of threading can be adjusted freely and applying initial compression to the coil spring whose other end is locked to the spring seat. a connecting portion, and the locking portion locks one end of the coil spring so that a screw member screwed into the fitting locks and regulates the amount of expansion of the coil spring. This is an overtravel device for a drum brake comprising a locking portion that locks the spring seat so as to restrict the amount of expansion of the coil spring between the spring seat and the screw member screwed into the case.

(Function) During braking, the operating member is pulled and the fitting is pulled. If the shoe gap is within the normal shoe gap, the adjuster lever is operated, but the adjuster gear is not rotated. If the shoe gap exceeds the regular shoe gap, normally the rotation of the adjuster lever increases, the adjuster gear is rotated, and the adjuster member adjusts the shoe gap.

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 connected to the spring seat of the fitting and the locking part of the case or the fitting. The overtravel device is compressed between the spring seat and the screw member screwed into the case, thereby extending the entire length of the overtravel device. In addition, by screwing in or out the screw member,
Initial pressure can be applied to the coil spring by adjusting the initial compression of the coil spring arbitrarily and steplessly.

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

1 and 2 show a first embodiment in which the present invention is applied to a dual servo brake, and the same reference numerals as in FIG. 4 indicate the same parts.

A plate-shaped swing link 23 with a through hole 23a formed in the center and locking holes 23b and 23c formed in both ends.
The through hole 23a is pivotally supported by a fixing pin 14b vertically provided on the web of one brake shoe 14, and the anchor block 22 is provided with an anchor vertically installed in the one through hole 23b. pin 22a
The other end of the upper link 26 is hooked to the upper link 26, and the other end of the lower link 27 is fixed to the fitting 3 of the overtravel device 1, which will be described later. is hanging. The upper link 26 and the swing link 23 constitute an operating member.

As shown in FIG. 2, the overtravel device 1 has a case 2, a fitting 3, and a compression type coil spring 4. The spring 4 whose other end is locked to the spring seat 3a
is given an initial compression.

The case 2 has a cylindrical shape, and a locking part 2a is formed on the inner peripheral surface of one end by welding and fixing another annular member (or by bending the edge of the case 2 inward), and a locking part 2a is formed on the inner peripheral surface of the other end. A flat plate-shaped arm 2b serving as a connecting portion is inserted and fixed into a U-shaped recess formed at one end of the case 2 to protrude therefrom, and a pin insertion hole 2b is provided at the other end of the arm 2b. ' is provided.

The fitting 3 has a rod shape, a disk-shaped spring seat 3a is fixed to the other end, a male thread 3b is carved in the middle part, and a lower link 27, which is a connecting part, is fixed to one end. . In this embodiment, the lower link 27 is inserted into a hole 3c provided at one end of the fitting 3 and fixed to the fitting 3 by caulking.

When the compression type coil spring 4 is inserted into the case 2, one end of the fitting 3 is inserted through a through hole formed in the spring 4 and the locking part 2a of the case 2, and the locking part 2a and the spring seat are connected. 3a, and an initial pressure is applied by elastically locking the screw member 5 screwed into the male screw 3b to the case 2 or one end surface of the locking portion 2a (see FIG. 2). Thus, the locking portion 2a is formed on the case 2 so as to restrict the amount of expansion of the coil spring 4, and the screw member 5 screwed onto the fitting 3 is attached to the case 2.
One end of the coil spring 4 is locked so as to be locked to one end.

Reference numeral 16 designates an adjuster lever that is rotatably supported by a pin 14a provided upright on the web of one brake shoe 14, and has the same function as the conventional example, and is connected to the arm 2b of the case 2. . Specifically, a pin insertion hole 16a is provided in the adjuster lever 16.
and a pin insertion hole 2 provided in the arm 2b of the case 2.
A pin 6 is inserted into b' and the pin insertion hole 16a, and a split pin 6a is inserted into the pin 6 to connect them.

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 exceeds a predetermined value, the adjuster gear 17 normally operates without compressing the compression type coil spring 4, and the adjuster gear 17a is screwed out, thereby automatically adjusting the shoe clearance. It will be done.

Further, sudden braking is performed, the swing link 23 swings greatly, the fitting 3 is strongly pulled, and at the same time, the axial force of the adjuster screw 17a against the adjuster nut 20 increases, and the screw 17
When rotation of a is impossible, the tensile force exceeds the set initial pressure of the compression type coil spring 4, and the spring 4 is compressed between the spring seat 3a of the fitting and the locking part 2a of the case, The total length of the overtravel device 1 is extended.

The initial pressure of the coil spring 4 can be adjusted steplessly by changing the amount of engagement of the screw member 5 with the male thread 3b of the fitting 3. 5a is
This is a lock nut that prevents the screw member 5 from loosening.

FIG. 3 shows a second embodiment of this invention, in which the same parts as in the first embodiment are given the same reference numerals and their explanation will be omitted.

In this embodiment, a male thread 2d is formed on the inner circumferential surface of one end of the case 2, and the locking portion 2c of the case 2 serves as one end surface of the arm 2b, that is, the bottom surface of the U-shaped recess of the arm 2b. It is formed at the other end of the case 2. This locking portion 2c has a function of locking a spring seat 3a that compresses the coil spring 4, which will be described later, between a screw member 32 screwed into the case 2, and regulating the amount of expansion of the coil spring 4. .

The compression-type coil spring 4 is compressed between the spring seat 3a locked by the locking part 2c and the screw member 32, and is given an arbitrary and stepless initial pressure. That is, when the coil spring 4 is inserted into the case 2, one end of the fitting 3 is inserted into the spring 4 and the through hole 3 of the threaded member 32 having a male thread.
2a, and the screw member 32 is screwed into the female screw 2d of the case 2.

According to this embodiment, when a tensile force exceeding the set initial pressure of the compression-type coil spring 4 is applied between the arm 2b and the lower link 27, which are both connecting parts, the spring 4 springs. Seat 3a and screw member 3
2, and the entire length of the overtravel device 1 is expanded. Therefore, the same effect as in the first embodiment can be obtained.

In addition, after applying initial pressure to the coil spring 4 when manufacturing and assembling the brake, the flange portion 32b of the screw member 32 is pressed against one end surface of the case 2, or the screw member 32 and the case 2 are connected by means such as welding. The screw member 32 can be prevented from loosening by fixing the screw member 32.

Note that the present invention can be similarly applied to a drum brake equipped with an auto-adjuster device in which the operating member (operating wire) is guided by a guide member fixed to the web of the brake shoe 14. be.

(Effect of the invention) As understood from the above explanation, according to the drum brake overtravel device according to the invention, even if the shoe clearance is within or exceeds the regular shoe clearance, During braking, it acts in the same way as the conventional example, and in the case of sudden braking, the compression type coil spring is compressed and the overtravel device acts. In addition, the compression type coil spring having no hook portion is difficult to break, and the durability of the overtravel device is improved, which in turn significantly improves the reliability of the auto-adjuster device.

Furthermore, according to the present invention, the initial pressure of the compression type coil spring can be easily and steplessly set by adjusting the fitting of the screw member or the amount of screwing into the case when manufacturing and assembling the brake.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a dual servo brake according to a first embodiment of the present invention, FIG. 2 is a sectional view taken along line A-A in FIG. 1, and FIG. 3 is a second diagram showing a second embodiment of the present invention.
FIG. 4, which is a sectional view similar to that shown in the figure, shows a dual servo brake to which a conventional drum brake overtravel device is applied. 1... Overtravel device, 2... Case, 2
a, 2c...Locking part, 2b...Arm (connecting part), 3
...Fitzteing, 3a...Spring seat, 3b...
Male thread, 4... Coil spring, 5, 32...
Screw member, 11... Bucking plate, 14...
...Brake shoe, 14a...Pin, 14b...
Fixed pin, 16... Adjuster lever, 21...
Adjuster member, 26... Upper link (operating member), 27... Lower link (connecting portion).

Claims (1)

[Scope of Claim for Utility Model Registration] An operating member that is connected at one end to the bucking plate side of the drum brake and an adjuster lever that is pivotably supported by the brake shoe and that operates an adjuster member. , in an overtravel device for a drum brake in which connecting parts provided at both ends are connected to an operating member and an adjuster lever, and absorb an excessive load acting on the adjuster lever via the operating member by extension. A case having a locking part at one end or the other end,
a coil spring inserted into the case; a fitting through which the coil spring is inserted and a spring seat formed at the other end; a threaded member that applies initial compression to a coil spring whose other end is screwed together and whose other end is locked to the spring seat; and a connecting portion formed at the other end of the case and one end of the fitting; The locking portion is a locking portion that locks one end of the coil spring so that a screw member screwed onto the fitting locks and restricts the amount of expansion of the coil spring, or a locking portion that is screwed onto the case. 1. An overtravel device for a drum brake, comprising a locking portion that locks the spring seat so as to restrict the amount of expansion of the coil spring between the screw member and the screw member.