JP2571011Y2 - Shoe gap adjustment limit detection and loss of shoe gap automatic adjustment function detection mechanism - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor for detecting a loss of an adjusting function of a lining gap adjusting mechanism of a drum brake and a lining total wear amount detecting mechanism. Are integrated to improve the simplification and durability of these detection mechanisms and improve the reliability of their operation. This invention is effective mainly when applied to drum brakes of large trucks, but is also effective when applied to drum brakes for various working machines such as medium and small cars, various construction vehicles, and winches. Things.

[0002]

2. Description of the Related Art A conventional mechanism for detecting a limit wear amount of a lining of a drum brake is attached to a shoe gap adjusting mechanism for maintaining a constant gap between a brake surface of a brake drum and a brake lining. -163
376). If the adjustment function of the shoe gap adjustment mechanism is lost, the shoe gap increases, the play becomes large, and the speed and stability of the brake operation are impaired. It is desirable to detect this promptly. It is not preferable to separately provide the mechanism for detecting the loss of the adjustment function of the shoe gap because the cost is increased.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a shoe gap adjustment function using a lining limit wear amount detection mechanism, in other words, a detection mechanism for shoe gap limit adjustment. By being able to detect loss, the simplification of these detection mechanisms,
It is an object of the present invention to improve the durability and reliability.

Prior to the description of the structure of the present invention, an outline of a conventional shoe gap adjusting mechanism as a premise of the present invention will be described with reference to FIGS. 4 and 5. FIG. This conventional example is described in JP-A-54-113768. A pair of left and right pistons 2, 2
1 are fitted and sealed by cup seals 27 and 29.
A nut 6 is fitted to the piston 2, and an adjustment bolt 4 is screwed into the nut 6, and one end of one brake shoe 3 is engaged with a groove 25 at the tip of the adjustment bolt. The other end of the other brake shoe 3a is engaged with the groove 22 at the tip of the other piston 21. Claw wheel 5 of nut 6
The tip of a T-shaped or L-shaped adjusting lever 8 is engaged with the adjusting lever 8. The adjusting lever is rotatably supported on a support shaft 7 of a rod 11, and a pin is attached to a guide plate 1 fixed to the piston 2. 9 are connected. The rod 11 is engaged with the notch 1a of the guide plate 1, and guides the guide plate 1 slidably right and left. The rod 11 is urged rightward by a compression spring 12 in a small cylinder 15, and its step 11a
Are in contact with the small cylinder 15. When the brake fluid pressure is transmitted to the oil chamber 28, the pistons 2 and 21 are pushed right and left, and the brake shoes 3 are frictionally engaged with the inner surface of the brake drum to generate a braking force. At this time, piston 2
At the same time, the guide plate 1 moves to the left, and the adjustment lever 8 rotates counterclockwise around the support shaft 7 against the return spring 19. At this time, if the braking gap between the brake shoe lining and the brake drum is within an appropriate value, the adjusting lever 8 moves only on one tooth of the ratchet wheel 5 and does not rotate the ratchet wheel. When the lining is worn and the braking gap exceeds an appropriate value, the ratchet wheel 5 rotates together with the nut 6 in the direction of arrow X by the counterclockwise rotation of the adjusting lever, and is screwed to the nut 6. The adjusting bolt 4 is pushed to the left to reduce the braking gap. When the piston 2 is pushed to the left so strongly that the brake drum is deformed, the screwing between the nut 6 and the adjusting bolt 4 becomes firm, and the ratchet wheel 5 cannot rotate, and the nut 6 and the adjusting bolt 4 are integrally formed. As a result, the piston is pushed to the left together with the piston 2 to prevent the brake clearance from being excessively adjusted. At this time, since the adjustment lever 8 cannot rotate, the rod 11 is pulled to the left while compressing the compression spring 12. When the brake is released, the pressure in the oil chamber 28 decreases, and the piston 2 is pushed back by the brake shoe 3 returned by the return spring of the drum brake. The adjustment lever 8 is rotated in the direction opposite to the arrow X along the circumference of the ratchet wheel 5 by the return spring 19 to engage with the next tooth of the ratchet wheel 5.
By repeating this operation, the position of the adjusting bolt 4 with respect to the nut 6 gradually moves to the left, and compensates for the increment of the brake shoe gap (brake shoe gap) and keeps it constant. The automatic shoe gap adjusting mechanism is disclosed in Japanese Utility Model Publication No. 57-4266 and Japanese Utility Model Publication No. 57-1227.
It is conventionally well-known as described in Japanese Patent Publication No. 0 and the like. The above is the above-described conventional automatic adjustment mechanism of the shoe gap and the limit adjustment mechanism of the shoe gap.

[0005]

Means taken to solve the problem On the premise of the above-mentioned conventional technology, the means taken to solve the above-mentioned problems are constituted by the following elements (a) to (c). (A) a sensor having two contact arms extending in a direction perpendicular to the brake piston is slidably supported in the same direction as the brake piston by a fixed support portion; The contact arm is opposed to the tip of the piston adjustment bolt 4 (see FIG. 2) via a gap a corresponding to the limit adjustment stroke of the shoe gap, and the other contact arm is slightly larger than the normal piston stroke. b. The nut 6 is opposed to the outer peripheral portion of the ratchet wheel 5 via b. (c) Electrical detection means for detecting the movement of the sensor in the same direction as the brake piston is provided.

[0006]

[Operation] As the wear of the brake lining progresses, the adjustment bolt 4 advances with respect to the piston 2, and the gap a corresponding to the limit adjustment stroke of the shoe gap decreases, and this advance stroke reaches a certain value. Then, the gap a becomes zero, the adjustment of the shoe gap reaches the limit, and the wear of the lining also reaches the limit. At this time, since the tip of the adjustment bolt 4 abuts on one of the contact arms of the sensor, the sensor is pushed forward by the adjustment bolt and moves forward, and the forward movement is detected by the electric detection means. Also, the shoe gap adjustment stroke is set to the gap a.
While smaller, the increment of the shoe gap due to the lining wear is compensated by the shoe gap adjusting device, so that the piston 2 and the nut 6 only reciprocate with a constant stroke, but the connection between the adjusting bolt 4 and the nut If the relative rotation becomes impossible and the shoe gap adjusting function is lost, the strokes of the nut 6 and the piston 2 increase with the subsequent progress of wear of the lining.
When the piston 2 moves forward, the ratchet of the nut 6 comes into contact with the other contact arm of the sensor and pushes it forward. The forward movement of the sensor at this time is detected by the electric detection means in the same manner as described above. Therefore, the loss of the adjusting function of the shoe gap limit adjusting mechanism and the fact that the amount of wear of the lining has reached the limit value can be detected by one sensor and the electrical detecting means for detecting the forward movement of the sensor. . Further, the sensor and the electric detecting means are
The mechanism is simple, and the mechanism is more durable, more stable in operation, and more reliable than with two separate sensors and an electrical sensing mechanism.

[0007]

[Embodiment] Next, an embodiment of the present invention will be described with reference to FIGS. 1, 2 and 3. FIG. The mechanism of the piston 2, the nut 6, the ratchet wheel 5, the adjustment bolt 4 and the like of this embodiment is the same as that of the above-mentioned conventional technology, and the sensor 40 parallel to the adjustment bolt 4 is used.
Are attached to the backing plate B so as to be slidable in the left and right directions (arrow A in FIG. 2). The sensor 40 has two long and short contact arms 41 and 42 extending at right angles to the brake piston, and the left long arm 41 corresponds to the limit adjustment stroke of the shoe gap with respect to the head 4 a of the adjustment bolt 4. The short arm 42 faces the outer peripheral portion of the ratchet wheel 5 via a gap b slightly larger than the normal stroke of the piston. The sensor 4 is provided in the switch box 43 of the switch.
A contact is provided opposite the rightmost contact of 0 and is normally open. When these two contacts come into contact to turn on the switch, an alarm such as a warning lamp 44 is activated. As the lining wears, the adjusting bolt 4 advances by the amount of wear of the lining, and the gap a decreases. When this gap is zero, the sensor 40 is pushed to the left by the adjustment bolt and the switch is closed. If the adjusting function is lost due to foreign matter biting into the threaded portion between the adjusting bolt 4 and the nut 6, the piston 2 and the piston 2,
The stroke of the nut 6 increases. When the gap b becomes zero due to the increase in the stroke, the sensor 40 is pushed to the left by the outer periphery of the ratchet wheel 5, and the switch is closed.
Specifically, the switch may be a simple one such as a non-contact type switch such as a contact type limit switch or a magnetic switch. The contact arm of the sensor does not need to be separate and independent. For example, as shown in FIG. 3, the contact arm 42 may be provided with a “type contact arm 41a”. If the alarm is issued when it can be inferred that the wear has not progressed so much, it is clear that the adjustment function has been lost. It is indistinguishable whether the adjustment function has been lost or the wear limit has been reached.However, it is empirically determined which of the two is based on the mileage of the vehicle after replacing the lining. Yes, there is no problem.

[0008]

[Effect] The above problem of the present invention is new. Therefore, solving this problem itself is an effect unique to the present invention. That is, the loss of the adjustment function of the shoe gap limit adjustment mechanism and the fact that the amount of wear of the lining has reached the limit value can be detected by one sensor and the electrical detection means for detecting the forward movement of the sensor. . In addition, the mechanism is simple because only one sensor and one electrical detection means are required, and the durability, the operation stability, and the reliability of the mechanism are compared with the case of using two separate sensors and the electrical detection mechanism. Can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a front view of a modified example of the sensor of FIG. 1;

FIG. 4 is a sectional view of a conventional example.

FIG. 5 is a plan view of FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Guide plate 1a ... Notch 2, 21 ... Piston 3, 3a ... Brake shoe 4 ... Adjustment bolt 4a ... Head of adjustment bolt 4 5 ... Claw wheel 6. ..Nut 7 ... Support shaft 8 ... Adjustment lever 9 ... Pin 11 ... Rod 11a ... Stepped portion 12 ... Compression spring 15 ... Small cylinder 17 ... Brake cylinder 19 ... Return springs 22,25 ... Grooves 27,29 ... Cup seal 28 ... Oil chamber 40 ... Sensor 41 ... Long contact arm 41a ... Contact arm 42 ... Short contact arm 43 ・ ・ ・ Switch box 44 ・ ・ ・ Warning lamp a, b ・ ・ ・ Gap B ・ ・ ・ Backing plate

Claims (1)

(57) [Scope of request for utility model registration] A sensor having two contact arms extending in a direction perpendicular to the brake piston is slidably supported in the same direction as the brake piston on a support of a fixed member. One of the abutting arms is opposed to the tip of the adjusting bolt of the piston via a gap a corresponding to the limit adjustment stroke of the shoe gap, and the other abutting arm is slightly larger than the normal piston stroke b. A shoe gap adjustment limit detection and a loss of automatic shoe gap adjustment function detection mechanism, wherein an electrical detection means for detecting the movement of the sensor in the same direction as the brake piston is provided in opposition to the outer periphery of the ratchet wheel of the nut.