JPH0121376B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gap adjusting device having a screw mechanism for adjusting the gap between a brake drum and a brake shoe.

In the case of a gap adjustment device that compensates for an increase in the gap between the brake shoe and the brake drum due to wear of the lining that is integral with the brake shoe, the driver must predetermine that the adjustment device is of a type that can be extended without limit. There is a risk that the lining may be used to the extent that it exceeds the wear limit without realizing it. If the wear limit is exceeded and the brake shoe is continued to be used, the metal surface of the brake shoe will come into contact with the brake drum, causing damage to the wear surface of the brake drum and making it impossible to obtain sufficient braking force. To this end, various proposals have been made in the past in which a rotating member of the gap adjustment member is provided with a stopping means for restricting its extension. However, the existing brake shoes had drawbacks such as requiring replacement of the brake shoe even if there was a large amount of lining remaining.

The present invention solves the above-mentioned drawbacks with a simple structure, and provides a device that stops the operation of the adjusting device before the wear of the lining reaches its limit and allows the driver to sense an increase in the pedal stroke or hand lever stroke. It is something to do.

Examples thereof will be described below with reference to the drawings. FIG. 1 is a plan view of a conventionally known manual gap adjustment type drum brake, in which 1 is a back plate fixed to a non-rotating part of the vehicle body; 2 and 3 are back plates 1;
The brake shoes 2a and 3a are lightly held by the shoe hold mechanisms 4 and 5, and linings 2a and 3a are attached to the outer peripheries of the brake shoes 2 and 3.
Reference numerals 6 and 7 denote a wheel cylinder and an anchor member, which are respectively disposed between the upper and lower adjacent ends of the brake shoes 2 and 3, and are both fixed to the back plate 1. A brake lever 8 has one end pivotally supported near the upper end of the brake shoe 3, and a control cable 9 connected to the other end. An adjustment member 10 that has the function of adjusting the gap between the brake drum (not shown) and the linings 2a and 3a is suspended between the middle part of the brake lever 8 and the brake shoe 2, and when the brake is not in operation, The shoes 2 and 3 are pulled back toward each other by the return springs 11 and 12. The adjustment member 10 is a threaded rod 1
3. A threaded rod 1 consisting of an adjustment nut 14 and a pipe member 15, one of which engages the brake lever 8.
The other threaded portion of the adjusting nut 14 is loosely fitted into the tube member 15, and one end surface of the adjusting nut 14, which is screwed into the threaded portion, is in contact with the open end surface of the tube member 15. The other side of the pipe member 15 has a split groove that is connected to the brake shoe 2.
is engaged with the notch groove 2b. Therefore, the outer diameters of the brake shoes 2 and 3 are such that the brake shoe 2 contacts the bottom of the split groove of the pipe member 15, the brake lever 8 contacts the bottom of the split groove of the threaded rod 13, and the protrusion 8a of the brake lever 8 is determined by the contact with the brake shoe 3.

In the above configuration, when the linings 2a and 3a are worn and the pedal stroke increases, the adjustment nut 14 is rotated from the back side of the back plate 1 with a tool such as a screwdriver, and the threaded portion of the threaded rod 13 is tightened to tighten the threaded part of the threaded rod 13. 15 to protrude from the adjustment member 1.
Although the entire length of the linings 2a and 3a is adjusted by extending it, there is a risk that the wear limit of the linings 2a and 3a will be exceeded because the adjustment can be made without limit.

FIG. 2 shows an embodiment of the adjustment member 20 according to the present invention that eliminates the above-mentioned drawbacks, and 21 is an adjustment bolt that is a rotating member, and the outer periphery of the flange 21a formed in the middle part is provided with uneven adjustment. The teeth 21b are carved, and the screw threads of the screw shafts 21c and 21d on both sides are wound in the same direction.
The thread pitch of c is set larger than the thread pitch of the other threaded shaft 21d. Then, tube members 22 and 23 having internal threads that are screwed into these screw shafts 21c and 21d are respectively fitted, and the tube members 22 and 2
Rotation relative to the brake shoe 2 and the brake lever 8 is prevented by a split groove 22a that engages with the brake shoe 2 and a split groove 23a that engages with the brake lever 8 provided at the outer end of the brake shoe 3. However,
When the adjustment tooth 21b is rotated in the direction in which one screw shaft 21c of the adjustment bolt 21 screws out from one tube member 22, the other screw shaft 21d screws out from the other tube member 23.
However, due to the difference in the thread pitch between the two, the total length of the adjusting member 20, that is, the length between the bottoms of the grooves 22a and 23a of both the tube members 22 and 23 increases. Therefore, if the dimension L from the side surface of the flange 21a of the adjustment bolt 21 to the open end surface of the other tube member 23 is set in advance to a value equivalent to the wear limit of the linings 2a and 3a, the open end surface of the tube member 23 will be aligned with the flange 21a.
When the adjustment bolt 21 comes into contact with the side surface, it becomes impossible to rotate, and the wear limit of the linings 2a and 3a can be easily detected. Further, the structure for stopping the rotation of the adjustment bolt 21 is not limited to the one described above, and it is clear that the tip of the other screw shaft 21d may be brought into contact with the bottom of the hole of the other tube member 23.

Next, an embodiment applied to an automatic gap adjustment type drum brake will be described with reference to FIGS. 3 and 4. FIG. 3 is a plan view of a conventionally known drum brake, in which reference numeral 101 is a back plate fixed to a non-rotating part of the vehicle body, and 102 and 103 are show hold mechanisms 104 and 10 on the back plate 101.
Brake shoe lightly held at 5, 1
02a, 103a are brake shoes 102, 10
106 is a wheel cylinder arranged adjacent to an anchor pin 107 interposed between the upper adjacent ends of the brake shoes 102 and 103, both of which are fixed to the back plate 101. . 110 is an adjustment member that connects the lower adjacent ends of the brake shoes 102 and 103, and also connects the brake drum (not shown) and the lining 1.
It also has the function of adjusting the gap between 02a and 103a. 111 is a spring that holds the adjustment member 110 in a fixed position, and 112 is a pair of return springs that bias the brake shoes 102, 103 to contact the anchor pin 107 when the brakes are not activated. The adjustment member 110 is composed of a threaded rod 113, an adjustment nut 114, and a head 115,
Flange 11 of adjustment nut 114 which is a rotating member
Adjustment teeth are carved on the outer periphery of 4a. The grooves provided on the outer ends of the threaded rod 113 and the head 115 are respectively locked to the brake shoes 102 and 103 to prevent rotation, and the threaded shaft portion of the threaded rod 113 is connected to the inner thread of the adjustment nut 114. and head 11.
The small diameter shaft portion of No. 5 is loosely fitted into the hole of the adjustment nut 114. Reference numeral 116 denotes an adjustment lever whose middle portion is rotatably supported on the brake shoe 103, and one end of the adjustment lever 116 abuts a substantially rigid connection member 117 that swingably locks onto the anchor pin 107. The other end is engaged with the adjusting teeth of the adjusting nut 114. Reference numeral 118 is an overload spring stretched between the adjustment lever 116 and the anchor pin 107, and always biases the adjustment lever 116 counterclockwise in the figure.

The operation of automatic gap adjustment in the above configuration will be explained. Now, when the brake drum (not shown) is rotating in the direction of arrow A, when the brake is applied, the brake shoe 103 separates from the anchor pin 107, and the adjustment lever 116 is also pivotally supported by the brake shoe 103. They move almost as one in a direction away from the anchor pin 107. At this time,
Since the substantial connection length of the connection member 117 does not change, the adjustment lever 116 rotates counterclockwise while in contact with the connection member 117. When the amount of rotation of the adjustment lever 116 is larger than the pitch of the adjustment teeth, the adjustment teeth are rotated to extend the adjustment member 110, thereby reducing the gap between the brake drum (not shown) and the linings 102a and 103a. Adjust to the specified amount. Furthermore, when the frictional force of the brake shoe 103 is transmitted to the brake shoe 102 via the adjustment member 110 and the thrust force of the adjustment member 110 increases, the surface pressure of the threaded portion increases, causing the adjustment nut 114 to tighten. Although the torque for rotation increases rapidly, at this time the overload spring 118 is expanded and the connecting member 117 can be in a free state, so that the self-adjusting component is not damaged. However, since the adjustment device with the above-mentioned configuration continues to adjust without limit, the lining 102
There is a possibility that the wear limit of a and 103a will be exceeded.

FIG. 4 shows an embodiment of an adjusting member 120 according to the present invention, which eliminates the above-mentioned drawbacks. Reference numeral 121 denotes an adjustment nut which is a rotating member, and serrated adjustment teeth 121b are carved on the outer periphery of its flange 121a. Furthermore, although the threads on both sides of the adjustment nut 121 are wound in the same direction, one inner thread 121c
The thread pitch of the inner thread 121d is larger than that of the other inner thread 121d. A screw shaft portion 122 is screwed into both internal screws 121c and 121d.
Adjustment bolts 122, 123 with a, 123a
are fitted into the adjusting bolts 122, 123, respectively, and the split grooves 122b, 123b provided at the outer ends of the adjusting bolts 122, 123 engage with the brake shoes 102, 103, respectively, so that rotation is prevented. However, adjustment lever 1
16, when the adjusting teeth 121b rotate in the direction in which one adjusting bolt 122 is screwed out, the other adjusting bolt 123 is screwed in, but due to the difference in thread pitch between the two, the entire length of the adjusting member 120, that is, both adjusting bolts 122, 123, the length between the bottoms of the grooves 122b and 123b is extended. Therefore, if the dimension l from the bottom of the neck of the other adjusting bolt 123 to the end face of the adjusting nut 121 is set in advance to a value equivalent to the wear limit of the linings 102a and 103a, the lining 10
2a, 103a reach the wear limit, the rotation of the adjustment nut 121 is stopped, and from then on, the pedal stroke gradually increases, so that the brake shoe 10
You can easily tell when it is time to replace the 2,103.

As is clear from the above, according to the present invention, it is possible to obtain an adjusting and stopping means that has a simple structure, is easy to assemble, and is reliable in operation. Further, even if the wear amount of the pair of linings is different from the set amount and there is a large amount of lining remaining, the device can be used continuously by releasing the stop means, which has great effects. It should be noted that the present invention is by no means limited to the above-mentioned embodiments,
For example, it is extremely easy to use a fixed member fixed to a back plate or the like with a female thread to form one non-rotating member.

[Brief explanation of drawings]

1 and 3 are front views of a conventionally known drum brake, and FIGS. 2 and 4 are detailed views of a gap adjusting member according to the present invention. 2, 3, 102, 103...brake shoe, 1
0, 20, 110, 120... Adjustment member, 21... Adjustment bolt which is a rotating member, 22, 23... Pipe member which is a non-rotating member, 121... Adjusting nut which is a rotating member, 122, 123... Non-rotating member. Adjustment bolt is a moving part.

Claims (1)

[Claims] 1. In a drum brake of the type in which the gap between the brake drum and the brake shoe is adjusted by an adjusting member having a screw mechanism, the adjusting member is composed of a rotating member having adjusting teeth and a non-rotating member screwed to both sides of the rotating member. wherein the winding directions of the threads of the pair of threaded joints are the same and the pitches of the threads are different, and when the rotating member abuts one of the non-rotating members, the adjustment member stops expanding. A gap adjustment and stop device for a drum brake, characterized in that: