GB1572942A - Disc brakes - Google Patents

Description

(54) IMPROVEMENTS IN DISC BRAKES (71) We, TOKICO LTD. a Japanese body corporate of 6-3, Fujimi 1-Chome, Kawasaki-ku, Kawasaki-shi, Kanagawaken, Japan, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to floating type disc brakes of the type including a mechanical activator having an eccentric cam for converting rotational movement of a brake lever into linear movement of a thrust member.

In disc brakes of the aforementioned type, the eccentric cam should be sufficiently lubricated, for attaining smooth rotational movement thereof in a supporting bore. In conventional disc brakes, constructional elements enclosing the eccentric cam are complexed and no lubricant supplying system is provided.

Thus, lubricant cannot be supplied periodically from the outside, and smooth rotation of the eccentric cam is sometimes disturbed during long periods of usage.

For obtaining smooth rotation of the eccentric cam, it is important, further to lubricate sufficiently, to improve dimensional accuracy and surface finish by grinding the outer periphery of the eccentric cam. Conventionally, the eccentric cam comprises a recess formed in the outer periphery of a cylindrical member having a uniform diameter to receive therein one end of a push rod, thus, the outer periphery of the cylindrical member cannot be ground accurately by using a centerless grinding machine. That is, when centerless grinding operation is effected on the cylindrical member constituting the eccentric cam, a portion of the cylindrical member will be formed to have a crosssection distorted from a true circle.

Therefore, conventional eccentric cams have been finished by using a universal grinding machine having a low operational efficiency as compared with a centerless grinding machine, thus impairing production efficiency of the disc brake and increasing production costs.

According to the present invention a floating type disc brake including a mechanical actuator utilizing an eccentric cam for converting rotational movement of a brake lever into linear movement of a thrust member, wherein the eccentric cam comprises a cylindrical member having axially spaced journal portions and a small diameter portion with the diameter smaller than that of the journal portions, said small diameter portion is formed between the journal portions and has a recess in the outer periphery thereof for receiving one end of a push rod therein.

One embodiment of the present invention will be described with reference to the attached drawings, in which: Figure 1 is a cross-sectional plan view of a disc brake according to the present invention; and Figure 2 is a cross-sectional view taken along line X-X' in Figure 1.

The disc brake shown in Figure 1 comprises a cylinder body 1 secured to a non-rotatable part of a vehicle, and a yoke 2 mounted slidably on the cylinder body 1 in the direction of the axis of a rotatable disc (not shown) or in the vertical direction in the drawing. The yoke 2 is a plate-like member and is received in grooves la formed in the opposite sides of the cylinder body 1. An hydraulic actuator having first and second components in the form of an outer piston 4 and an inner piston 3 slidably received in the cylinder body 1. An adjustor 5 is disposed in the inner piston 3 and engages screw-threadingly with a screw portion 6a formed in the lower end (as viewed in the drawing) of a plunger 6. The upper end portion 6b of the plunger 6 is fitted slidably in a bore 7 formed in the outer piston 4.

A transverse bore 8 is formed on the upper portion of the bore 7 and in the outer piston 4, and an eccentric cam 9 is rotatably received in the bore 8 through a bush 10. A push rod 11 having two semi-spherical ends engages with a recess formed in the upper end 6b of the plunger 6 and with a recess opening 9a formed in the eccentric cam 9. Further in the drawing, shown at 12a and 12b are friction pads associated respectively with the inner piston 3 and the yoke 2.

When the eccentric cam 9 is rotated in the counter-clockwise direction in Figure 1 by operating a brake lever (shown at reference numeral 13 in Figure 2), the friction pads 12a and 12b are pressed against the rotatable disc to effect braking action, and the details of which will be described hereinafter. In Figure 2, the brake lever 13 to which a cable or the like (not shown) is connected is secured to one end of the eccentric cam 9 received in the bore 8. A seal ring 14 preventing ingress of dust, water or the like into the bore 8 is provided on the open end of the bore 8.

Journal portions 9b, 9b are provided on the opposite ends of the eccentric cam 9 and are rotatably supported in the bush 10. A small diameter portion 9c having a diameter smaller than that of the journal portions is formed therebetween, and a recess 9a for receiving one end lla of the push rod 11 therein is formed in the small diameter portion 9c. As shown in Figure 1, the recess 9a is formed such that one end 1 la of the push rod 11 inserted into the recess 9a engages with the eccentric cam 9 at a point offsetting from the center of rotation of the eccentric cam 9, whereby, when the eccentric cam 9 is rotated in the counterclockwise direction in Figure 1 the push rod Il is moved downward in the drawing by the eccentric cam 9. Thus, rotational force on the brake lever 13 is converted by the eccentric cam 9 into thrust force on the push rod 11.

When the push rod 11 is moved downward in Figure 1 by actuating the brake lever 13, the plunger 6 and the inner piston 3 are moved downward and the friction pad 12a is pressed on one surface of the disc. According to reaction induced therefrom, the yoke 2 moves upward in the drawing and the friction pad 12b is applied against the other surface of the disc. Thus, mechanical braking action is effected by rotating the eccentric cam 9.

As described above, the eccentric cam 9 according to the present invention provides a small diameter portion 9c having a diameter smaller than the diameter of the journal portions 9b and 9b, thus, a highly viscous lubricant such as grease or the like can be stored in a space between the small diameter portion 9c and the bore 8 which assures smooth rotation of the eccentric cam during a long period of usage. Further, the recess 9a is formed in the small diameter portion 9c which enables to finish the journal portions 9b and 9b by using a centerless grinding machine, thus, production efficiency of the eccentric cam is improved and production cost of the disc brake can be saved.

The embodiment described heretofore in detail relates to a floating yoke type disc brake having a mechanical and hydraulic actuators and an automatic adjustor, but it will be appreciated that the present invention may be applied to disc brakes of any other types including a mechanical actuator utilizing an eccentric cam.

WHAT WE CLAIM IS: 1. A floating type disc brake including a mechanical actuator utilizing an eccentric cam for converting rotational movement of a brake lever into linear movement of a thrust member, wherein the eccentric cam comprises a cylindrical member having axially spaced journal portions and a small diameter portion with the diameter smaller than that of the journal portions, said small diameter portion is formed between the journal portions and has a recess in the outer periphery thereof for receiving one end of a push rod therein.

2. A disc brake as set forth in Claim 1 wherein the journal portions of the eccentric cam have been finished by centerless grinding operation.

3. A disc brake as claimed in Claim 1 or 2, in which the cam is rotatable about an axis transverse to the line of action of the cam.

4. A disc brake as claimed in Claim 3 in which the cam is journalled in one component of a hydraulic actuator and acts via the push rod and an automatic adjuster on the thrust member which is in the form of a second component of the hydraulic actuator.

5. A disc brake constructed and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. through a bush 10. A push rod 11 having two semi-spherical ends engages with a recess formed in the upper end 6b of the plunger 6 and with a recess opening 9a formed in the eccentric cam 9. Further in the drawing, shown at 12a and 12b are friction pads associated respectively with the inner piston 3 and the yoke 2. When the eccentric cam 9 is rotated in the counter-clockwise direction in Figure 1 by operating a brake lever (shown at reference numeral 13 in Figure 2), the friction pads 12a and 12b are pressed against the rotatable disc to effect braking action, and the details of which will be described hereinafter. In Figure 2, the brake lever 13 to which a cable or the like (not shown) is connected is secured to one end of the eccentric cam 9 received in the bore 8. A seal ring 14 preventing ingress of dust, water or the like into the bore 8 is provided on the open end of the bore 8. Journal portions 9b, 9b are provided on the opposite ends of the eccentric cam 9 and are rotatably supported in the bush 10. A small diameter portion 9c having a diameter smaller than that of the journal portions is formed therebetween, and a recess 9a for receiving one end lla of the push rod 11 therein is formed in the small diameter portion 9c. As shown in Figure 1, the recess 9a is formed such that one end 1 la of the push rod 11 inserted into the recess 9a engages with the eccentric cam 9 at a point offsetting from the center of rotation of the eccentric cam 9, whereby, when the eccentric cam 9 is rotated in the counterclockwise direction in Figure 1 the push rod Il is moved downward in the drawing by the eccentric cam 9. Thus, rotational force on the brake lever 13 is converted by the eccentric cam 9 into thrust force on the push rod 11. When the push rod 11 is moved downward in Figure 1 by actuating the brake lever 13, the plunger 6 and the inner piston 3 are moved downward and the friction pad 12a is pressed on one surface of the disc. According to reaction induced therefrom, the yoke 2 moves upward in the drawing and the friction pad 12b is applied against the other surface of the disc. Thus, mechanical braking action is effected by rotating the eccentric cam 9. As described above, the eccentric cam 9 according to the present invention provides a small diameter portion 9c having a diameter smaller than the diameter of the journal portions 9b and 9b, thus, a highly viscous lubricant such as grease or the like can be stored in a space between the small diameter portion 9c and the bore 8 which assures smooth rotation of the eccentric cam during a long period of usage. Further, the recess 9a is formed in the small diameter portion 9c which enables to finish the journal portions 9b and 9b by using a centerless grinding machine, thus, production efficiency of the eccentric cam is improved and production cost of the disc brake can be saved. The embodiment described heretofore in detail relates to a floating yoke type disc brake having a mechanical and hydraulic actuators and an automatic adjustor, but it will be appreciated that the present invention may be applied to disc brakes of any other types including a mechanical actuator utilizing an eccentric cam. WHAT WE CLAIM IS:

1. A floating type disc brake including a mechanical actuator utilizing an eccentric cam for converting rotational movement of a brake lever into linear movement of a thrust member, wherein the eccentric cam comprises a cylindrical member having axially spaced journal portions and a small diameter portion with the diameter smaller than that of the journal portions, said small diameter portion is formed between the journal portions and has a recess in the outer periphery thereof for receiving one end of a push rod therein.

2. A disc brake as set forth in Claim 1 wherein the journal portions of the eccentric cam have been finished by centerless grinding operation.

3. A disc brake as claimed in Claim 1 or 2, in which the cam is rotatable about an axis transverse to the line of action of the cam.

4. A disc brake as claimed in Claim 3 in which the cam is journalled in one component of a hydraulic actuator and acts via the push rod and an automatic adjuster on the thrust member which is in the form of a second component of the hydraulic actuator.

5. A disc brake constructed and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.