JPS6135795Y2 - - Google Patents

Description

[Detailed description of the invention] This invention consists of a pair of brake shoes that are slidably supported on a back plate, one end of which is in contact with a wheel cylinder, the other end of which is in contact with an anchor, and the end of a strut is attached to a brake shoe near the wheel cylinder. This device relates to an automatic braking gap adjustment device for drum brakes that adjusts the braking gap by rotating the adjusting nut by rotating the adjusting strut lever and adjusting the braking gap. A support shaft is fixed to the brake lever that expands the brake shoe, and the adjustment lever is inserted through this support shaft and brought into contact with the inner side of the back plate of the support shaft, and the tip claw of the adjustment lever is connected to the adjustment nut. The other end of the torsion spring is engaged with the ratchet teeth of the brake lever, the other end is in contact with the inner side of the back plate of the brake lever, and one end of the torsion spring attached to the support shaft is used as an adjustment lever, and the other end is used as the support shaft. The adjustment lever is urged in the direction of operation of the brake lever by a constant load, and the torsion application point of the adjustment lever is set between the point of contact of the adjustment lever with the brake lever and the point of contact with the support shaft. It is characterized in that it is located between the brake lever and the distal end pawl 15b of the adjustment lever is biased so as to apply a pressing force in the direction of the adjustment nut. This ensures reliable transmission, eliminates any rotational loss of the adjustment lever during adjustment operation, and ensures that adjustment operation is performed reliably.
When the adjustment lever returns after rotating the adjustment nut, by releasing the brake lever, the adjustment lever returns to its initial position due to the urging force of the torsion spring in the non-operating direction of the brake lever. At this time, the pawl of the adjuster lever disengages from the engaged ratchet tooth, slides on the tooth surface, passes over one tooth without reversing the adjuster nut, engages the next ratchet tooth, and adjusts the adjuster. The brake lever can return to its initial position smoothly and reliably, thereby ensuring reliable adjustment operation, and even if excessive rotational force is generated on the brake lever, the rotational force of the brake lever is transmitted to the adjustment lever. First, it is an object of the present invention to provide an automatic braking gap adjustment device for the drum brake, which can prevent damage to the adjustment lever.

An embodiment of the present invention will be described below with reference to the drawings.

Reference numeral 1 denotes a back plate fixed to a stationary portion of the vehicle body, and arcuate brake shoes 2, 2 are provided inside the back plate. The brake shoes 2, 2 have one end of the shoe webs 2a, 2a supported by an anchor 3, the other end abutting against the pistons 5, 5 at both ends of the wheel cylinder 4, and a brake shoe 2 stretched between the two shoe webs 2a, 2a. The return springs 6 and 7 of the book are always biased in the direction toward the book.

8 is a brake lever with one end surface 8a in contact with the trailing side shew web 2a, 9 is a support shaft with a serration portion 9a press-fitted into the brake lever 8, and a roller 11 is inserted through the end of the first strut 10. and is prevented from coming off with a clip 12. The roller 11 and the head 9b of the support shaft 9 are formed to have the same diameter, and slide on the back plate 1 when the brake lever 8 is rotated.

The first strut 10 is loosely inserted into the second strut 13 with a male threaded portion 10a formed on its outer periphery in contact with the shew web 2a on the leading side. Reference numeral 14 designates an adjusting nut having ratchet teeth on its outer periphery, which is screwed into the male threaded portion 10a of the first strut 10 in contact with the open end surface of the second strut 13. When the adjusting nut 14 is rotated, its screw movement causes the second strut to open. The first strut 10 is sent out from the strut 13 and the braking gap can be adjusted.

Reference numeral 15 denotes an adjustment lever rotatably inserted into the small diameter shaft portion 9c of the support shaft 9. The insertion hole 15a abuts on the inside of the back plate of the small diameter shaft 9c, and the distal end claw portion 15b engages with the ratchet of the adjustment nut 14. engaged with the teeth. This adjuster lever 1
5 is bent toward the brake lever 8 side, and a protrusion 15 formed on this upper end 15c
d is in contact with the inner end surface 8b of the back plate of the brake lever 8.

16 is a torsion spring attached to the support shaft 9, and the torsion force of this torsion spring 16 is set smaller than the return spring force of the return springs 6 and 7;
a is locked in a locking groove 15e formed in the upper end 15c of the adjuster lever 15, and the other end 16b is locked in a locking groove 9d formed in the head 9b of the support shaft 9.
As a result, the adjustment lever 15 is moved to the brake lever 8 by the constant load of the torsion spring 16.
is biased in the direction of operation.

The point where the end portion 16a of the torsion spring 16 is locked in the locking groove 15e of the adjustment lever 15 becomes the torsion action point A, and this torsion action point A is the protrusion of the adjustment lever 15 in FIG. 15d and the inner end surface 8b of the back plate of the brake lever 8, and a contact point B where the insertion hole 15a of the adjustment lever 8 and the inner side of the back plate of the small diameter shaft portion 9c of the support shaft 9 abut. and the tip claw 15b of the adjusting lever 15 with respect to the line connecting the contact points B and C so as to apply a pressing force to the tip claw 15b of the adjusting lever 15 in the direction of the adjusting nut 14. It is set offset.

Next, the operation of this embodiment will be explained.

First, when the brake lever 8 is rotated in the direction A in FIG.
3, the brake shoes 2, 2 are expanded to perform braking.

At this time, the adjustment lever 15 is biased by the torsion spring 16 in the non-rotating direction of the brake lever 8, and always contacts the brake lever 8 at the contact point B and the small diameter shaft portion 9c of the support shaft 9 at the contact point C. Since the rotational force of the brake lever 8 is immediately transmitted to the adjustment lever 15,
The brake lever 8 is rotated in the same direction by the torsion force of the torsion spring 16, and the adjuster nut 14 is rotated when the linings 2b, 2b are worn. At this time, the torsion action point A of the adjustment lever 15 is the contact point B with the brake lever 8 and the small diameter shaft portion 9 of the support shaft 9.
The adjustment lever 15 is provided between the contact point C and the contact point C and is offset toward the claw portion 15b side of the adjustment lever 15,
The pressing force of the adjusting nut 14 of the claw portion 15b of the adjusting lever 15 is Pl ₁ /l ₂ .

In addition, P is the torsion force of the torsion spring 16, and _l1 is the contact point B and contact point C in FIG.
The distance between the line L ₁ connecting and the torsion point A, l ₂
is the line connecting contact point B and contact point C in Figure 2.
This is the distance between L ₂ and the tip of the claw portion 15b of the adjustment lever 15.

When the brake lever 8 is released, the adjustment lever 15 is returned to its original position by the biasing force of the torsion spring 16 in the non-actuating direction of the brake lever 8. At this time, the torsion spring 16
Since the torsion force of
Since the sliding resistance is smaller than the sliding resistance between the first and second struts 10 and 13, the pawl portion 15b of the adjusting lever 15 slides on the tooth surface and moves the adjusting nut 14 to the fourth position without reversing the position. By moving in the direction shown in the figure, the adjustment lever 15 passes over one tooth and engages with the next ratchet tooth, and the adjuster lever 15 returns to its original position.

In this case, since the projection 15d formed on the upper end 15c of the adjustment lever 15 is in contact with the inner side of the back plate of the brake lever 8, the distance _l1 between the line _L1 and the torsion application point A is It remains unchanged, and the claw portion 15b is attached to the adjuster nut 14.
The pressing force remains unchanged, and the problem of the teeth returning after being adjusted is more reliably prevented.

Then, by rotating the adjuster nut 14,
The first strut 10 is fed out from the second strut 13, and the braking gap is automatically adjusted by compensating for the amount of wear on the linings 2b, 2b.

In the auto-adjustment performed during braking, if excessive rotational force is further applied to the brake lever 8 due to compressive deformation of the lining, deformation of the entire brake shoe, etc. after the braking gap has become zero, The adjustment lever 15 is always in contact with the brake lever 8 at the contact point B and the small diameter shaft portion 9c of the support shaft 9 at the contact point C, but the inner end surface 8b of the back plate of the brake lever 8 is Escaping away from the protrusion 15d of No. 15,
A gap occurs. The escape load at this time is Pl ₃ /l ₄ . In addition, l ₃ is the distance between the torsion application point A and the contact point C in FIG. 2, and l ₄ is the distance between the tip of the claw part 15b of the adjuster lever 15 and the contact point C in FIG.
is the distance between.

As a result, the rotational force of the brake lever 8 is not transmitted to the adjustment lever 15, so that over-adjustment will not occur and the tip claw portion 15b will not be over-adjusted.
Since no overload is applied to the claw portion 15b, the claw portion 15b will not be damaged.

In the above embodiment, the adjustment lever 15 is provided on the torsion spring 16 side, but the adjustment lever 15 is not limited thereto, and may be provided on the roller 12 side.

As described above, according to the present invention, the adjustment lever is brought into contact with the brake lever and the support shaft by the constant load of the torsion spring, and is urged in the operating direction of the brake lever, so that the rotational force of the brake lever is applied to the adjustment lever. The rotational loss of the adjustment lever during adjustment operation is completely eliminated, and the braking gap can be adjusted reliably, and the insertion hole of the adjustment lever is always in contact with the support shaft due to the torsion spring. Since they are in contact with each other, manufacturing costs can be improved without requiring precise machining accuracy. When the brake lever is released after rotating the adjuster nut, the adjuster lever is rotated toward its initial position by the biasing force of the torsion spring in the deactivation direction of the brake lever. Since the claw portion of the strainer slides on the tooth surface of the ratchet tooth of the adjuster nut and returns to the initial position by passing over one tooth, the adjuster nut can be reliably returned to the normal position without reversing the position. Furthermore, even if excessive rotational force of the brake lever occurs, the inner side of the back plate of the brake lever separates from the adjustment lever and escapes, and the rotational force of the brake lever is not transmitted to the adjustment lever, making the arbor adjustment effective. Since overload is not applied to the claw portion of the adjustment lever, it can be used for a long period of time without being damaged.

In addition, the torsion application point of the adjustment lever is located between the contact point with the brake lever and the contact point with the support shaft, and is offset so as to apply a pressing force in the direction of the adjustment nut to the tip claw of the adjustment lever. This has the effect of minimizing strain at the contact point between the adjustment lever and the torsion spring.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; Fig. 1 is a plan view, Fig. 2 is a front view of the main parts, and Fig. 3 is a
4 is a partially cutaway plan view of the figure, and FIG. 4 is a partially cutaway side view with the lower half of FIG. 2 omitted. 1 is a back plate, 2 and 2 are brake shoes, 8 is a brake lever, 9 is a support shaft, 10 is a first strut, 13 is a second strut, 14 is an adjustment nut, 15 is an adjustment lever, 16
is a torsion spring.

Claims (1)

[Scope of utility model registration request] One end of a pair of brake shoes slidably supported on the back plate is brought into contact with a wheel cylinder, the other end is brought into contact with an anchor, and the end of the strut is brought into contact with the brake shoe near the wheel cylinder, and the adjustment lever is rotated. In a drum brake that adjusts the braking gap by rotating an adjustment nut and extending this strut by motion, a support shaft is fixed to a brake lever that comes into contact with the one brake shoe to widen the brake shoe, and The adjustment lever is inserted through the support shaft and brought into contact with the inner side of the back plate of the support shaft, and the tip claw of the adjustment lever engages with the ratchet teeth of the adjustment nut, and the other end of the adjustment lever engages with the ratchet teeth of the adjustment nut. One end of a torsion spring that abuts the inner side of the back plate and is further inserted into the support shaft is locked to the adjustment lever, and the other end is locked to the support shaft, so that the adjustment lever is loaded with a constant load. biases the brake lever in the operating direction, positions the torsion application point of the adjustment lever between the point of contact of the adjustment lever with the brake lever and the point of contact with the support shaft, and An automatic braking gap adjustment device for a drum brake, characterized in that a tip pawl portion is biased so as to apply a pressing force in the direction of an adjuster nut.