JPH0158374B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drum brake incorporating an automatic shoe gap adjustment device, and is intended to facilitate manual reduction of the outside diameter of the brake shoe.
Conventionally, one end of an adjustment lever that directly or indirectly senses the amount of movement of the brake shoe corresponding to wear of the lining engages with sawtooth adjustment teeth to form a ratchet mechanism, and the adjustment teeth are connected to the Automatic shoe gap adjustment device that automatically rotates the adjustment lever to extend the extensible screw mechanism that supports one end of the brake shoe, thereby maintaining a constant gap between the brake drum and the lining. Various proposals have been made.

In this type of equipment, it is necessary to reduce the outside diameter of the shoe when over-adjustment occurs, when the sliding surface of the drum has grooves and the lining gets stuck in them, or after the drum is installed. When you want to narrow the gap between the shoes more than the automatic gap adjustment, that is, when the drum is normally installed, the outside diameter of the shoe is set smaller than the inside diameter of the drum, and even if the automatic gap adjustment device is operated while the vehicle is stationary, it will not work while the vehicle is running. If the gap was not completely filled, for example, if a control cable, which is a mechanical actuator, was disposed in this state, problems such as an excessive stroke of the hand lever would occur. Therefore, it is generally necessary to perform so-called manual gap adjustment, in which the outside diameter of the shoe is manually expanded to a state where the drum is locked, and then reduced by a predetermined amount.

However, in the case of the above-mentioned manual gap adjustment work, the tool tip must be pressed against the substantially circumferential slope of the serrated adjustment teeth and then rotated in the opposite direction. As a result of the increased operation, the number of man-hours on the brake assembly line increases, and inspection and maintenance work in the market becomes troublesome.

In view of the above-mentioned problems, the present invention facilitates the work of reducing the outside diameter of the shoe by simply changing the shape of the adjusting teeth.

1 and 2 show an example of a conventionally known leading-trailing type brake, in which 1 is a back plate, and 2 and 3 are a pair of T-shaped cross sections movably mounted on the back plate 1. 2a and 3a are linings fixed to the outer peripheries of the shoes 2 and 3, and 4 is the shoe 2 and 3 facing each other.
A wheel cylinder, which is a hydraulic pressure generating device, is inserted between the upper adjacent ends and fixed to the back plate 1; 5 is an anchor member inserted between the lower adjacent ends of the shoes 2 and 3 and fixed to the back plate 1; ,6
is a brake lever, one end of which is rotatably supported by a pin 7 near the upper end of the shoe 3, and a control cable, which is a mechanical actuator (not shown), is connected to the other end. . A strut member 8, which has a function of adjusting the gap between the brake drum (not shown) and the linings 2a and 3a, is stretched between the middle part of the brake lever 6 and the shoe 2. The formed protrusion 6a comes into contact with the shoe 3, and the outer diameter of the shoe 2, 3 is determined at all times. The strut member 8 includes a threaded rod 9, an adjustment nut 10 and a pipe member 1.
1, the threaded rod 9 has one fork portion 9a that engages with the brake lever 6, and the other threaded portion 9b that screws into an adjustment nut 10, and its protruding portion is loosely inserted into the hollow portion of the pipe member 11. It is fitted. One fork portion 11a of the tube member 11 engages with the notch groove 2b of the shoe 2, and the other open end surface engages with the adjustment nut 1.
It is in contact with one side of 0. Reference numeral 12 denotes an adjustment lever pivotally supported by a pin 13 near the upper end of the shoe 2, and is loosely fitted to the pin 13 with a desired gap in the axial and radial directions. FIG. 2 is a view of the adjustment lever 12 seen from the back plate 1 side, and one arm 12a of the lever 12 extends toward the adjustment nut 10, and is bent at an approximately right angle as shown in FIG. The drive tooth 12b at the tip end is a serrated adjustment tooth 1 formed on the outer periphery of the adjustment nut 10.
It is engaged with 0a. The other arm 12c of the adjustment lever 12 extends outward from the fork portion 11a of the tube member 11, and its inner edge 12d is in contact with the outer end surface of the fork portion 11a. Further, a bent portion 12e facing the back plate 1 is formed on the outer edge side of the other arm 12c, and an adjustment spring 14 stretched between the bent portion 12e and the shoe 2 allows the above-mentioned adjustment lever 12 to be attached. The condition is maintained. In other words, the adjustment spring 14 constantly brings the strut member 8 into contact with the brake lever 6, and also applies a biasing force to engage the drive tooth 12b of the adjustment lever 12 with the adjustment tooth 10a of the adjustment nut 10. . 12f is adjustment lever 1
This is a protrusion protruding near the inner edge 12d of the shoe 2, and is in sliding contact with the surface of the shoe 2. 15a and 15b are shoe return springs that separate the shoes 2 and 3 from the brake drum (not shown) when the brake is released;
Reference numerals 16a and 16b are holding mechanisms that lightly press the shoes 2 and 3 onto the back plate 1.
The operation of automatic shoe gap adjustment in the above configuration will be explained.

When wheel cylinder 4 operates, show 2,
3 expands against the shoe return springs 15a, 15b and presses against a rotating brake drum (not shown) to brake it. At this time, the adjustment lever 12
Since rotational force is applied in advance by the adjustment spring 14 to the strut member 8, the strut member 8 follows the movement of the shoe 3 and rotates counterclockwise about the pin 13 as a fulcrum in FIG. If the linings 2a, 3a are worn out and the amount of expansion of the shoes 2, 3 is larger than a predetermined amount, the driving tooth 12b rotates the adjusting nut 10 approximately one pitch in the direction of arrow A in FIG. At least the threaded rod 9 is pulled out from the pipe member 11, thereby increasing the overall length of the strut member 8 and connecting it to the brake drum (not shown) and the linings 2a, 3a.
This allows the gap between the two to be maintained constant at all times.

Strictly speaking, during this adjustment, the adjustment lever 12 is extended by the amount that the strut member 8 is extended.
The amount of rotation of the driving tooth 12b becomes slightly smaller than one pitch of the adjusting tooth 10a, so that it cannot engage the tooth surface of the next new adjusting tooth 10a when the brake is released.

And the brake drum and linings 2a, 3
During normal brake operation after completing the gap adjustment a, the drive tooth 12 of the adjustment lever 12 remains closed until the linings 2a and 3a wear out and engage with the tooth surface of the next new adjustment tooth 10a. always slides back and forth on the sawtooth slope 10b.

Further, the manual adjustment of the shoe gap is performed as follows. When expanding the outer diameter of the shoes 2 and 3, after removing the plug 17 shown in FIG. That's fine. On the other hand, when reducing the outer diameter of the shoes 2 and 3, the adjustment lever 12 and pin 13 shown in FIG.
Push the part of the lever 12 that is closer to the outside of the brake than the imaginary line Y connecting the contact point with the protrusion 12f from the hole drilled in the back plate 1, and move the arm 12a side to the back plate 1 side. After rolling and disengaging the driving tooth 12b from the adjusting tooth 10a, the adjusting nut 10 is rotated in the direction opposite to that when the shoes 2 and 3 are expanded, that is, in the direction of arrow B in FIG. That's a good reason. However, when rotating the adjustment nut 10 in the direction of arrow B when reducing the shoes 2 and 3, the tip of the tool 18 has serrated adjustment teeth 1.
The tip of the tool 18 is in contact with the slope 10b extending substantially in the circumferential direction of the tool 0a, and is in a state where it is extremely slippery.

The present invention is intended to facilitate the work of reducing the outer diameter of the shoes 1 and 2 mentioned above, and will be explained in detail with reference to FIG. 4. That is, an upright surface 10c is formed on the slope 10b of the serrated adjustment tooth 10a, rising outward from an appropriate position, and the upright surface 10c
A suitable protrusion 10d is provided that connects the apex of the sawtooth. In other words, the drive tooth 12 of the adjustment lever 12
b forms the tooth surface side that is rotationally engaged with the protruding portion 10d, and the opposite side forms the depression, thereby forming the upright surface 10.
One step defined by c is provided between the teeth. Therefore, when reversing the adjustment nut 10, it is possible to avoid operational errors by disengaging the drive tooth 12b using the method described above and then engaging the tip of the tool 18 with the upright surface 10c. It is possible to completely eliminate the problem, and the pressing force of the tool 18 against the slope 10b is also completely unnecessary, which further improves the work.

Note that the operation of automatically adjusting the gap between the brake drum and the linings 2a, 3a due to wear of the linings 2a, 3a is the same as the conventional operation described above, so a description thereof will be omitted.

Also, during normal brake operation after the automatic gap adjustment has been completed, the drive tooth 12 of the adjustment lever 12
b simply slides back and forth on the protrusion 12d or on the slope 10b, so there is no fear that the automatic gap adjustment action will be hindered.

As is clear from the above, according to the present invention, the shoe outer diameter can be easily reduced simply by changing the shape of the adjustment teeth without adding any parts, and this has a significant effect. Furthermore, the present invention is by no means limited to the above-mentioned leading-trailing type brake, but can also be used for a dual-servo type brake with serrated adjustment teeth, a two-leading type brake, etc., and the scope of its application is wide. Extensive.

[Brief explanation of drawings]

Figure 1 is a front view of a conventionally known drum brake.
FIG. 2 is a view of the automatic adjustment device section seen from the back, and FIGS. 3 and 4 are enlarged cross-sectional views of FIG. be. 1... Back plate, 2, 3... Brake shoe, 2a, 3a... Lining, 4... Wheel cylinder, 5... Anchor member, 6... Brake lever, 8... Strut member, 9... Screw Rod, 10... Adjustment nut, 10a... Adjustment tooth, 1
0b...Slope, 10c...Elevated surface, 10d...Protrusion, 11...Pipe member, 12...Adjustment lever, 1
2a...One arm, 12b...Drive tooth.

Claims (1)

[Claims] 1. The extendable screw mechanism member supporting one end of the brake shoe is provided with a member having serrated adjustment teeth on the outer peripheral surface, and the brake shoe can be moved in response to wear of the lining. When the amount exceeds the specified amount,
In a brake gap adjustment device that detects this, the adjustment lever rotates the adjustment teeth approximately one pitch, thereby automatically adjusting the gap between the brake drum and the lining. In addition to forming an upright surface that once stands upright toward the upright surface, the tooth surface side with which the adjustment lever rotationally engages with respect to the upright surface is formed as a protruding part to form a step between the teeth, and under normal conditions, the adjustment lever A gap adjustment device for a brake shoe, characterized in that the brake shoe is configured to slide back and forth on a protrusion of an adjustment tooth.