JPS5939614B2 - Braking gap automatic adjustment device for mechanical drum brakes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a cam member that penetrates the back plate and is interposed between the free ends of a pair of brake shoes whose base ends are pivotally supported on the back plate, and the cam member is rotated by a brake arm. The present invention relates to an automatic braking gap adjustment device for a mechanical drum brake that performs braking by expanding a brake shoe and pressing it against the inner peripheral surface of a brake drum.

Conventionally, this type of automatic braking gap adjustment device rotates to spread the brake shoes and adjust the cam, which performs braking, by sequentially changing the rotation angle of the cam as the lining wears out, thereby improving the braking between the brake drum and the lining surface. The gap is automatically adjusted.

Therefore, the amount of rotation of the brake arm necessary for sufficient braking increases with the amount of wear on the lining, and the amount of rotation of the cam also increases with the amount of rotation, causing the rotation angle of the cam to exceed the normal range. If this is exceeded, not only will it cause a serious accident due to poor braking or no braking, but the rotation angle of the cam will change due to adjustment even within the normal operating range, so the point of action of the cam will be different during braking, and the braking action of the brake arm will be affected. There were problems such as the corresponding constant braking cannot be changed.

The present invention has been developed in view of the above-mentioned problems, and it rotates a shaft having a tapered cam surface relative to the adjustment gear as the lining wears out, and rotates the shaft in a direction perpendicular to the expanding direction of the brake shoes. As a result, the brake shoe that directly or indirectly contacts the cam surface of the shaft is expanded and adjusted, and when the brake is released, the shaft, which rotates together with the brake arm, is always returned to the initial position of the brake arm. Its purpose is to stabilize the braking action by keeping the rotation angle of the brake arm, that is, the pedal stroke or grip of the brake, constant at all times, and to provide an automatic braking clearance system that solves the above-mentioned problems. To provide a regulating device.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

Reference numeral 1 designates a back plate, and its outer surface has a brake operation wire attachment portion 2, a speedometer cable attachment portion 3, and a groove 4 that engages with a protrusion (not shown) formed on a part of the vehicle body to receive brake torque. has been done.

5.5' is a pair of brake shoes, the base end 5a of which is a pair of brake shoes.

5/a is pivotally supported on the inner surface of the back plate 1 with an anchor pin 6.

7 and 1' are linings fixed to the brake shoes 5 and 5', and 8 is a roughly U-shaped return spring whose middle part is wrapped around the anchor pin 6 and both ends are locked to the brake shoes 5 and 5'. It is.

Reference numeral 9 denotes a cam member inserted between the free ends 5b and 5'b of the brake shoes 5 and 5', the shaft portion 9a of which is rotatably provided on the back plate 1, and a serrated shaft portion that projects outside of the bank plate 1. A brake arm 10 is fixed to 9b with a tightening bolt 11.

A grease reservoir 9e formed on the shaft portion 9a of the cam member 9 is filled with grease, so that the cam member 9 rotates smoothly.

12 is a shaft inserted into the cam member 9, and the shaft portion 12a
Tapered cam surfaces 12c, 12'C are formed on the inner side of the head 12b provided on the brake shoes 5, 5' side, while a leftward threaded portion 1 is formed on the brake arm 10 side.
2d is formed, and this shaft 12 has a head 12b.
is guided by the inner wall 9d of the opening end formed in the housing portion 9C of the cam member 9, and moves in a direction perpendicular to the direction in which the brake shoes 5, 5' are expanded.

13 and 13' on both sides of the shaft head 12b,
Rectangular window portion 1 formed in the housing portion 9c of the cam member 9
4, 14' is a cam collar that is slidable in the direction of expansion of the brake shoes 5, 5', and is attached to the shaft head 12b.
The tapered surfaces 13a, 13'a formed on the inside facing the cam surfaces 12C, 12'C are the cam surfaces 12c, 12'c.
The cam collars 13, 13 are slidably engaged with the cam collars 13, 13
The outer sides 13b and 13'b of ' are the window parts 1 of the housing part 9c.
4, 14' are in contact with the end surfaces 5c, 5'c of the brake shoes 5, 5' inserted into the brake shoes 5, 5'.

Reference numeral 15 denotes an adjustment gear screwed onto the threaded portion 12d of the shaft 12, and has a gear portion 15a formed on the outer periphery so as to be inclined clockwise in FIG.

16 is an adjustment member whose one end is fixed to the brake arm 10 with a screw 17, and the tip claw part 16a is connected to the gear part 15.
a to rotate the adjustment gear 15 in the adjustment direction, while allowing the brake arm 10 to rotate in the braking direction.

Reference numeral 18 denotes an elastic stopper member whose one end is fixed to the back plate 1 with a screw 19, and its tip claw portion 18a engages with the gear portion 15a to allow the adjustment gear 15 to rotate only in the adjustment direction, and to rotate in the non-adjustment direction. The rotation is permitted and regulated to some extent by the elastic deflection of the claw portion 18a itself.

Reference numeral 20 denotes a bearing interposed between the adjust gear 15 and the brake arm 10. This bearing 20 has four spherical parts 21a formed in three places on a cover 21 that is fitted onto the shaft part 15b of the adjust gear 15, and balls 22 are attached to each of the four spherical parts 21a. A convex portion 21b protruding outward corresponding to the rotatably provided concave portion 21a is located on the side surface 10a of the brake arm 10.
The adjustment gear 15 is engaged with four portions 10b formed correspondingly to the four portions 10b, respectively, so that the adjustment gear 15 rotates smoothly.

23 has a brake lever or brake pedal (
(not shown), the other end of which is attached to the tip of the brake arm 10.

Reference numeral 24 denotes a case of the brake operating wire 23, which is attached to the brake operating wire mounting portion 2 with an adjustment bolt 25 and a nut 26.

27 is a brake arm return spring that is wrapped around the brake operation wire 23 and compressed between the brake operation wire attachment part 2 and the tip of the brake arm 10, and the spring force causes the brake arm 10 to return to its initial position after the braking operation. I'm trying to go back.

Next, the operation of this embodiment will be explained.

When braking is performed by operating the brake lever or brake pedal, the brake arm 10 is rotated in the direction of arrow A in FIG. 1 by the brake operation wire 23, and as the brake arm 10 rotates, the cam member 9 The cam collars 13, 13' and the shaft 12, which are engaged with the cam collars 13, 13', and the shaft 12 rotate together in a counterclockwise direction in FIG.
, 13'b of the brake shoes 5, 5'.

5/c, and brake shoes 5 and 5'
The lining 1° 1' expands against the spring 8 and presses against a brake drum (not shown) to perform braking.

At this time, the rotation angle of the brake arm 10 is such that the claw portion 16a of the adjustment member 16 is
This is the range of sliding on the slope of the same tooth of 5a, and the claw part 1
6a is not able to overcome one tooth.

Further, at this time, the rotational force generated in the adjustment gear 15 in the clockwise direction in FIG. 1 is regulated by the stopper member 18, and the adjustment gear 15 does not rotate in the clockwise direction.

When the brake is released, the brake shoes 5, 5' are returned by the return spring 8, and the cam member 9, cam collars 13, 13', and shaft 12 rotate clockwise in FIG. 2 as a unit. and return to the original position.

On the other hand, the brake arm 10 also rotates in the direction of arrow B in FIG. 1 by the brake arm return spring 27 and returns to its initial position.

If the lining 7.7' is worn out by the braking action and a braking gap larger than the set value is created between the inner circumferential surface of the brake drum and the surface of the lining 7.7', the adjustment gear 15 will move at the claw portion 18a of the stopper member 18 during braking. The rotation accompanying the rotation of the brake arm 10 is restricted, and the claw portion 16a of the adjustment member 16 engages the gear portion 15 of the adjustment gear 15.
3 and 4, the shaft 12 is screwed out from the adjustment gear 15 to the right in FIGS.
The brake shoes 5. are pushed by the cam surfaces 12c and 12'c of the brake shoes 5.
Move in the expansion direction of 5' to complete the adjustment.

Then, when the braking operation is released, the brake arm 10, cam member 9, cam collars 13, 13' and shaft 12
are rotated together in a counterclockwise direction in FIG.

At this time, the adjustment gear 15 is also rotated counterclockwise by the claw portion 16a, whereby the claw portion 18a of the stopper member 18 passes over one tooth, allows the adjustment gear 15 to rotate counterclockwise, and engages with the next tooth. However, the locking relationship between the claw portion 16a and the tooth of the adjustment gear 15 that is engaged by passing over one tooth is maintained, and the inner circumferential surface of the brake drum and the lining 7.7 are maintained.
'Adjust the braking gap with the surface.

Therefore, as the lining 7.1' wears out, the pawls 16a of the adjusting member 16 successively merge with the teeth of the gear part 15a of the adjusting gear 15, and the braking gap is automatically adjusted.

Also, when braking, excessive braking force is applied to the brake arm 1.
0, that is, after the brake arm 10 is pressed against the inner surface of the brake drum, the brake arm 10
When an external force is applied that does not deflect the brake drum,
Brake shoes 5, 5 pressed against the inner surface of the brake drum
′ acts on the head 12b of the shaft 12 to push the shaft 12 to the left in FIGS. 3 and 4, causing the shaft 12 to rotate clockwise in FIG. 20, the adjustment gear 15 also rotates clockwise smoothly.

At this time, the rotation of the adjustment gear 15 is controlled by the stopper member 1.
8, the engagement position between the claw portion 18a and the tooth of the gear portion 15a of the adjustment gear 15 is allowed to remain unchanged, and when the excessive braking force disappears, the adjustment gear 15 returns to its original position, and the adjustment is completed. This effectively prevents over-adjustment.

In addition, since the amount of wear of the linings T and 1' is greater on the leading side than on the trailing side, in the above embodiment, the cam surface 12C on the leading side of the shaft head 12b
If the cam surface 12'C is formed to have a steeper slope than the trailing side cam surface 12'C, the leading side brake shoe 5 becomes the training side brake shoe.

It can be adjusted to be wider than 5', and the braking gap on both sides can be kept constant.

Further, in the embodiment, cam collars 13, 1 are provided between the end surfaces 5c, 5'c of the brake shoes 5°5' and the cam surfaces 12c, 12'c of the shaft head 12b.
3', but the end surfaces 5 of the brake shoes 5, 5'
c, 5'c and the cam surface 12c of the shaft head 12b
.

12'C may be brought into direct contact.

Further, the shaft head 12b is formed with a tapered cam surface that is inclined in the opposite direction to that in the above embodiment, and the shaft portion 12a is formed with a rightward threaded portion, and the adjustment gear 15 is rotated in the same manner. Even if the cam member 9 is made to protrude from the housing 9c of the cam member 9, the braking gap can be kept constant as in the previous embodiment.

In addition, in the above embodiment, when the brake is released, the adjustment member 16
Although the adjusting gear 15 was allowed to rotate together with the shaft 12 and returned to its initial position, the pressing force between the threaded portion 12d of the shaft 12 and the adjusting gear 15 was greater than the pressing force of the gear portion 15a of the adjusting gear 15 of the stopper member 18.
If the frictional resistance of the threaded portion is large, it is not necessary to use the adjusting member 16.

As described above, the present invention rotates a shaft having a tapered cam surface with respect to an adjustment gear as the lining wears out, and moves the shaft in a direction perpendicular to the direction in which the brake shoes expand. The brake shoe, which directly or indirectly contacts the cam surface, is expanded and adjusted, and when the brake is released, this shaft, which rotates together with the brake arm, always returns to the initial position of the brake arm. The cam surface of the shaft that comes into direct or indirect contact with the brake can always be in contact at the same position, and the rotation angle of the brake arm is always held constant during braking, and the brake pedal or grip distance is always constant and stable. In addition to obtaining braking, as in the past, the cam angle changes and adjusts as the lining wears, and due to the difference in the cam's application point, stable braking cannot be obtained for a given brake arm braking action. There is no inconvenience.

In addition, since the rotation angle of the cam member and shaft does not increase as the lining wears, unlike in the past, when the rotation angle of the cam exceeds the normal range, braking becomes poor or impossible, causing a serious accident. There is no risk of such.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a front view, FIG. 2 is a rear view, FIG. 3 is a cross-sectional view taken along FIG. 2 i-I, and FIG. 4 is a cross-sectional view taken along FIG. The sectional view, FIG. 5, is an exploded perspective view of the cam member, shaft, and cam collar. 1 is the back plate, 5 and 5' are the brake shoes, 7.1
' is the lining, 9 is the cam member, 12 is the shaft, 1
2b is its head, 12C, 12'C are its cam surfaces, 13
, 13' is the cam collar, 15 is the adjustment gear, 1
5a is the gear part, 16 is the adjusting member, 16a is the claw part, 18 is the stopper member, and 18a is the claw part.

Claims (1)

[Scope of Claims] 1. A cam member penetrating through the back plate is interposed between the ends of a pair of brake shoes whose base ends are pivotally supported on the back plate, and the cam member is rotated by a brake arm,
In a mechanical drum brake that performs braking by expanding a brake shoe and pressing it against the inner peripheral surface of a brake drum, a tapered cam surface is slidably engaged directly or indirectly with the brake shoe, and the cam A shaft that rotates integrally with the member is inserted into the cam member so as to be movable in a direction perpendicular to the expanding direction of the brake shoe, and an adjustment gear is screwed onto the shaft, so that the adjustment gear rotates together with the shaft during braking. A stopper member is provided to regulate the
A mechanical drum brake characterized in that a rotating shaft is screwed out from an adjustment gear to spread the brake shoes when braking, and when the brake is released, the adjustment gear is rotated in the opposite direction together with the shaft to return to the initial position. automatic braking gap adjustment device. 2. Braking of a mechanical drum brake according to claim 1, characterized in that a cam collar that rotates integrally with the cam member is provided between the tapered cam surface of the shaft and the end surface of the brake shoe. Automatic gap adjustment device.