JPS59110926A - Two leading type drum brake - Google Patents

Abstract

PURPOSE:To aim at a reduction in the number of parts items as well as an increase in braking force, by constituting an operating shaft member consisting of a cam part and a pin part in a way of setting up it rotatably between both ends of a pair of brake shoes, in case of the above-captioned brake for small vehicles including a motorcycle or the like. CONSTITUTION:With a brake operated, when each of operating shaft members 3 and 3' is rotated, cam parts 3a and 3'a expand the plane surface part of each of toe side end parts 4a and 4'a of brake shoes 4 and 4' to the outside of a brake drum circumference. With this outward expansion, these brake shoes 4 and 4' forcibly presses the inner circumferential surface of a brake drum 1 with each of pin parts 3b and 3'b of the other side operating shaft members 3 and 3' being rotatably engaged with end parts 4b and 4'b at the heel side and thus performs braking a car. With this constitution, each of clearances l and l' between the toe side end parts 4a, 4'a and the heel side end parts 4b, 4'b becomes narrowed, and each of brake linings 5 and 5' also is able to grow long toward these operrating shaft members 3 and 3' whereby a frictional area can be increased in length. Therefore, braking force can be increased despite such a simple constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a two-leading drum brake mainly used in small vehicles such as motorcycles.

A two-leading drum brake, which is a mechanical drum brake generally used for small vehicles, has a pair of brake shoes arranged facing each other on the circumference of the brake plate, and a pair of brake shoes facing each other on the circumference of the brake plate. Anchor pins that pivotally support the respective heel-side ends and brake cams that push the toe-side ends are independently provided at symmetrical positions across the two sides. Therefore, compared to a leading/trailing type drum brake in which the opposing heel side ends of a pair of brake shoes are pivoted to an anchor pin and the toe side ends are in contact with a brake cam, there is only one brake cam and one anchor pin. The structure of many of them is more complex. Moreover, since these brake components are arranged on the circumference of the brake plate, it is necessary to secure mounting space, so the length of the brake shoe is shortened, and as a result, the friction area of the brake lining is reduced. . Furthermore, since the number of parts increases and the weight increases, the manufacturing cost is 75 (bulky and requires a lot of effort to assemble), and this is an obstacle to reducing the size and weight of the device.

This invention was made against the background of the above circumstances, and its purpose is to provide a two-leading type drum brake that secures the friction area of the brake lining, provides greater braking force, and reduces the number of parts. , to provide the keys.

In order to achieve the above object, the two-leading drum brake of the present invention rotatably disposes an actuation shaft member having a cam part and a pin part between both ends of a pair of brake shoes, and each actuation shaft member has a cam part and a pin part. The cam portion of the member abuts the toe end of one brake shoe, and the pin portion rotatably engages the heel end of the other brake shoe.

Hereinafter, the present invention will be explained in detail with reference to an illustrated embodiment.

1 is a brake drum that rotates integrally with the wheel; 2 is a brake plate that is fixed to a non-rotating axle; and a pair of actuating shaft members 3 are located at symmetrical positions on the circumference, sandwiching the center of the brake plate.
, 3' are rotatably provided. This operating shaft member 3
, 3' is the cam portion 3 on the forward rotation direction A side of the brake drum.
a, 3'a't - the opposite side Nihin part 3b,
3'b 't'', and can be rotated by an operating shaft lever (not shown).

A pair of half-moon-shaped brake shoes 4, 4' are arranged so as to face each other and sandwich the operating shaft members 3, 3' from both sides of the brake plate 2P'3VC.
a, 4'a are the flat parts located at the upper left 3a of the actuating shaft members 3, 3'.
*a'a, and the heel side ends 4b, 4'b are rotatably engaged with the pin portions 3'b, 3b of the operating shaft member 3.3' through their recesses. And brake shoe 4°4
The brake linings 5, 5' are fixed to the outer circumferential surface of the pair of actuating shaft members 3.3'', so that the toe side end 4a and heel side end of the pair of actuating shaft members 3.3'' are sandwiched from both sides. 4'b and the distances t and z' between the heel side end 4b and the toe side end 4'a are set short.

This brake lining 5.5' is also the actuating shaft member 3.
, 3' directions, respectively, thereby increasing the friction area and obtaining a thick brake. A return spring 6.6' is stretched between the pair of brake shoes 4.4' and biased toward each other.

In the above device, when the gripping force or pedaling force is transmitted to the brake part via the brake cable or the brake rod to rotate the first actuating shaft member 3, 3', the cam part 3a,
3'a pushes the flat portions of the toe-side ends 4a, 4'a of the pair of brake shoes 4, 4' to the outside of the circumference. As a result, the brake shoes 4, 4' press against the inner circumferential surface of the brake drum 1, using the pin portions 3b, 3'b of the other operating shaft members 3, 3' as fulcrums, respectively.
Perform braking.

At this time, the bottle portions 3b, 3 of the operating shaft members 3, 3'
'b is the heel side end 4b of the brake shoes 4, 4'
, 4'b, the actuating shaft members 3, 3' rotate smoothly without being hindered.

The pair of brake shoes 4, 4' are connected to the operating shaft member 3.
Since the bottle parts 3b and 3'b of 3' serve as fulcrums, the toe side ends 4a and 4'a are connected to the heel side ends 4b and 4.
A brake force is applied to 'b, and this brake torque is received by the bin portions 3b, 3'b.

As described above, this invention has a cam function that presses the brake shoes to the outside of the circumference, and a pin function that serves as a rotational fulcrum of the brake shoes, in the actuating shaft member disposed between both ends of a pair of brake shoes. Therefore, the space on the circumference of the brake plate can be used effectively, and the friction area of the brake lining of the brake shoe can be increased. Also, since the number of parts is reduced, the weight can be reduced.

[Brief explanation of the drawing]

The drawing is a front view showing an embodiment of the two-leading drum brake of the present invention. 1...brake drum, 2...brake plate,
3.3'... Operating shaft member, 3a, 3'a...
Cam part, 3b, 3'b...bin part, 4,4'.
...Brake shoe, 4a, 4'a...Toe side end, 4b, 4'b...Heel side end, 5.5
'・・・Brake lining

Claims (1)

[Claims] A pair of brake shoes are arranged so as to be expandable in the direction of the brake drum with the heel side end as a fulcrum when the toe side end is pushed, and each brake shoe is extended from the toe side end during forward braking. , in a two-leading drum brake in which a braking force is applied to the heel side end, an operating shaft member having a cam part and a pin part is rotatably disposed between both ends of the pair of brake shoes;
The cam portion of each actuating shaft member is in contact with the toe side end of one brake shoe, and the pin portion is rotatably engaged with the heel side end of the other brake shoe. Shaped drum brake.