GB1577421A

GB1577421A - Disc brakes

Info

Publication number: GB1577421A
Application number: GB1773377A
Authority: GB
Original assignee: Tokico Ltd
Current assignee: Tokico Ltd
Priority date: 1976-04-30
Filing date: 1977-04-28
Publication date: 1980-10-22
Also published as: JPS52146690U; BR7702765A; JPS5748999Y2

Description

(54) IMPROVEMENTS RELATING TO DISC BRAKES (71) We, TOKICO LTD., a Japanese body corporate of 6-3, Fujimi l-chome, Kawasakiku, Kawasaki-shi, Kanagawa-ken, 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 disc brakes, and particularly, to improvements in pad springs which are biassing friction pads of the disc brakes.

Usually, friction pads of the disc brakes are biassed radially by one or more pad springs for enabling smooth sliding movement of friction pads in axial direction in applying brake thus preventing rattling noise caused by vibrations.

An aim of the present invention is to provide a disc brake having a pad spring which is simple in construction, easy in manufacture, and easy in assembling.

According to the present invention there is provided a disc brake comprising two guide pins mounted on a caliper main body for supporting and guiding a fixed pad and a movable pad, each pad comprising a friction pad and backing plate therefor, pad actuating means being arranged to move the movable pad slidably on the guide pins toward one surface of a rotatable disc when applying the brake, with the fixed pad being immobile with respect to the guide pins, a pad spring being disposed between the guide pins and the pads, wherein the pad spring comprises a main body portion with one end portion thereof engaging with the Iperiphery of the fixed pad and the other end portion thereof engaging with the periphery of the movahle pad, two arm portions projecting from the main body portion to abut on the undersides of the guide pins respectively and thereby urge the main body portion of the spring against the pads.

and a projection formed on the one end portion of the main body portion to extend between the face of the fixed pad backing plate remote from the fixed friction pad and the adjacent portion of the caliper so that the fixed pad backing plate lies between the projection and said two arm portions thereby to locate the pad spring relative to the fixed pad.

The present invention will now be further described by way of example, with reference to the accompanying drawings, in which: Figure 1 is a partially broken top plan view of one embodiment of a disc brake constructed according to the present invention; Figure 2 is a cross-sectional view taken along line II-II in Figure 1; Figure 3 is a plan view of the pad spring used in the disc brake of Figure 1; Figure 4 is an end view of the pad spring of Figure 3 as seen along line IV in Figure 3; and Figure 5 is a side view of the pad spring of Figure 4 as seen along line V in Figure 3.

The disc brake illustrated in Figures 1 and 2 comprises a main body 1 of a caliper formed of the two members la and ib. A cylinder 3 slidably recieving a piston 3 is formed in one of the caliper members la, and the piston 3 is adapted to project from the cylinder 2 to urge a friction pad 6 against one surface of a rotatable disc (not shown) when oil under pressure is supplied in the cylinder 2. A cavity 4 extending in the upper and lower side directions in Figure 2 is formed in the main body 1, and the cylinder 2 opens into the cavity 4.

Pad retaining pins or guide pins for guiding movement of friction pads (described in detail hereunder) extend between the caliper members la and lb across the cavity 4. The pins 5 extend through openings (not shown) formed in backing plates of the pads according to the usual technique.

The pad assembly the friction pad of which is applied against the rotatable disc directly by the piston 3 is referred to as a movable pad, and is slidably supported on the pins 5. The other pad assembly, is referred to as the fixed pad 7, lies opposite to the movable pad 6 and is also supported on the pins 5 but is fixedly mounted on the main body 1 by means of stoppers 8, 8 such as cotter pins inserted respectively in small holes formed in each of the pins 5.

The stoppers 8, 8 control the positions of the fixed pad 7 and also prevent the pins 5, 5 -from escaping from the main body 1.

The bracket pins 9 are mounted on the left and right sides (in Figure 1) of the main body 1 to connect and secure the caliper members la and lb with one another. The pins 9 extend through respective cavities (only one of which is shown in Figure 1 by reference numeral 10) which open in the lower side of the caliper 1 in Figure 2. The pins 9 are slidably fitted in a bracket 11 in the region of the cavity 10. The bracket 11 is secured to a non-rotatable part (notshown) of a vehicle. In applying the brake, the friction pad 6 is pressed directly by the piston 3 against one surface of the rotatable disc and reaction force moves the caliper with respect to the bracket 11 to apply the fixed pad 7 against the other surface of the disc A A pad spring 12 constituting an essential portion of the present invention will now be described in detail with reference to Figures 3 to 5.

The pad spring 12 is formed of a sheet like resilient-member and includes a main body portion 13 and two arm portions 14, 15 which are disposed on a generally central portion of the main body portion 13 in the lengthwise direction thereof and projecting therefrom in opposite directions perpendicular to said lengthwise direction. One side portion 131 (the upper side in Figure 3) of the main body portion 13 with respect to the arm portions 14, 15 is, as shown in Figure 5, bent downward to form a downward projecting portion 16. The other side portion 1311 of the main body portion is, as shown in Figure 5, bent downwards in the same general direction as the projecting portion 16 though at an obtuse angle to the main body portion. The arm portions 14 and 15 are, as shown in Figure 4, bent downward in the same general direction as the projecting portion 16 and the other side portion 1311, and the free end portions thereof are bent upwardly to form acute shapes having radii nearly equal to the radii of the pins 5.

A- mark 17 is disposed on the upper surface of the main body portion 13 to indicate a condition for effecting replacement of friction pads.

In assembling the pad spring 12 having a construction as described above, the main body portion 13 is located on the upper side (in Figure 2) of the pads 6 and 7, the projecting portion 16 is inserted between the rear surface of the backing plate of the fixed pad 7 and the body member 1b to locate the main body portion 13, and the arm portions 14, 15 are bent resiliently and abut on the underside of the pins 5 respectively. (Practically, one of the arm portions 14 or 15 is positioned downward of corresponding pin 5 with the other pin 5 removed, thereafter, the main body portion 13 is pressed downward in Figure 2 so that the other arm portion 15 or 14 is moved to a position downward of the pin which has been removed, then the pin is inserted to hold the pad spring 12 in its position).

Thus, one side portion 131 of the main body portidn 13 will abut the upper side (in Figure 2) of the fixed pad 7 resiliently and the other side portion 131l of the pad spring 12 will abut the upper side (in Figure 2) of the movable pad 6 resiliently. Thereby, the upper main surface of the main body portion will lie in a substantially flat plane with a resilient force stored in the main body portion 13.

The resilient force acts to restore the main body portion 13 to its initial form, but upward movement of the main body portion 13 is prevented by engagement of the arm portions 14, 15 with the pins 5. Thus, the resilient force acts on the friction pads 6, 7 to urge them downward relative to the pins 5. In the illustrated embodiment, the arm portions 14, 15 are located adjacent to the fixed pad 7 and the said other side portion 1311 is bent downward with an obtuse angle form, as shown in Figure 5. Thus, it is possible to divide the resilient force of the pad spring 12 evenly between the fixed pad 7 and the movable pad 6 irrespective of the positions or distances of the fixed pad 7 and the movable pad 6 with respect to the positions of the arm portions 14, 15 engaging with the pins 5.

The operation of the disc brake according to the present invention will now be decribed.

When oil under pressure is supplied into the cylinder 2 to act on the rear surface of the piston 3, the piston 3 is forced out from the cylinder 2 whereby the movable pad 6 is applied against one surface of the disc.

The movement of the pad 6 is restrained by the disc, and the main body 1 of the caliper thus slides relative to the bracket 11 when further oil is supplied to the cylinder 2. so that the fixed pad 7 abuts against the other surface of the disc, whereby the braking action is effected. During the above described operation, the pad spring 12 acts to press the pads 6 and 7 downwards in Figure 2 i.e.

in the direction normal to the direction of the brake applying movement of the pads 6 and 7, and the caliper main body ], and the pad pins 5 and the fixed pad 7. do not move relative to the pad spring 12, though the pad spring 12 does move slidably relative to the movable pad 6, the lower surface (as seen in Figure 2) of the other side portion 131l of the main body portion 13 being slidingly engaged with the upper end (as seen in Figure 2) of the movable pad 6.

When the brake is released by releasing oil from cylinder 2, the fixed pad 7 separates from the disc, the main body 1 of the caliper moving in the backwards direction i.e. to the left, in Figure 2 and the movable pad 6 slidingly moves along the lower surface of the main body portion 13 of the spring pad 12.

When wear has occurred in the friction pads, the movable pad 6 will aproach the arm portions 14, 15 in the brake released position. However, the resilient force of the pad spring 12 acting on the movable pad 6 is maintained, in accordance with the present invention, substantially constant. This resilient force is maintained substantially constant due to the fact that the pad spring 12 is located fixedly relative to the caliper main body 1, the pad pins 5 and the fixed pad 7, and the other end portion 131l urging the movable pad 6 is formed to incline downward in the direction toward the piston 3.

When wear of the friction pads exceeds an allowable limit, it is necessary to replace the friction pads. According to the present invention, it is easy to detect the pad replacement time by utilizing the mark 17 applied on the upper surface of the pad spring 12, namely, the pad replacement time can be indicated by determining the location of the mark 17 such that the movable pad 6 will align the mark 17 when the movable pad 6 has been worn by the maximum allowable limit. (In the embodiment, the displacement of the movable pad 6 measured from the initial position will indicate the sum of wear of the friction pads).

The disc brake heretofore described is of a so-called floating caliper type or of a type wherein a fixed pad or a pad secured to caliper main body is applied on the rotatable disc with the caliper main body being displaced by reaction force, but it will be noticed that the present invention may be applied to the disc brakes of the type comprising a main body secured to a nonrotatable part of a vehicle, two pistons disposed in the main body, a movable pad actuated by one of the pistons, a displaceable member called a yoke which is displaceable relative to the main body, and fixed pad secured to the yoke. The yoke in the latter case corresponds to the caliper main body 1 in the presently illustrated embodiment.

WHAT WE CLAIM IS:- 1. A disc brake comprising two guide pins mounted on a caliper main body for supporting and guiding a fixed pad and a movable pad, each pad comprising a friction pad and backing plate therefor, pad actuating means being arranged to move the movable pad slidably on the guide pins toward one surface of a rotatable disc when applying the brake, with the fixed pad being immobile with respect to the guide pins, a pad spring being disposed between the guide pins and the pads, wherein the pad spring comprises a main body portion with one end portion thereof engaging with the periphery of the fixed pad and the other end portion thereof engaging with the periphery of the movable pad, two arm portions projecting from the main body portion to abut on the undersides of the guide pins respectively and thereby urge the main body portion of the spring against the pads, and a projection formed on the one end portion of the main body portion to extend between the face of the fixed pad backing plate remote from the fixed friction pad and the adjacent portion of the caliper so that the fixed pad backing plate lies between the projection and said two arm portions thereby to locate the pad spring relative to the fixed pad.

2. A disc brake as claimed in claim 1, in which said main body portion of the pad spring has a form of a generally flat plate and is bent perpendicular with respect to the plane of the flat plate at a position adjacent to said one end thereof to form said projection.

3. A disc brake as claimed in claim 2, in which said other end portion of the main body portion of the pad spring is bent by a small angle with respect to the plane of the flat plate so that resilient force of the pad spring transmitted to the movable pad is substantially constant irrespective to axial position of the movable pad with respect to the pad spring.

4. A disc brake as claimed in claim 2 in which said projection engages with said remote face of the fixed pad to locate the pad spring with respect to the fixed pad.

5. A disc brake as claimed in claim 1, in which a mark for indicating pad replacement time is provided on the upper surface of the main body portion of the pad spring.

6. A disc brake constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. from cylinder 2, the fixed pad 7 separates from the disc, the main body 1 of the caliper moving in the backwards direction i.e. to the left, in Figure 2 and the movable pad 6 slidingly moves along the lower surface of the main body portion 13 of the spring pad 12. When wear has occurred in the friction pads, the movable pad 6 will aproach the arm portions 14, 15 in the brake released position. However, the resilient force of the pad spring 12 acting on the movable pad 6 is maintained, in accordance with the present invention, substantially constant. This resilient force is maintained substantially constant due to the fact that the pad spring 12 is located fixedly relative to the caliper main body 1, the pad pins 5 and the fixed pad 7, and the other end portion 131l urging the movable pad 6 is formed to incline downward in the direction toward the piston 3. When wear of the friction pads exceeds an allowable limit, it is necessary to replace the friction pads. According to the present invention, it is easy to detect the pad replacement time by utilizing the mark 17 applied on the upper surface of the pad spring 12, namely, the pad replacement time can be indicated by determining the location of the mark 17 such that the movable pad 6 will align the mark 17 when the movable pad 6 has been worn by the maximum allowable limit. (In the embodiment, the displacement of the movable pad 6 measured from the initial position will indicate the sum of wear of the friction pads). The disc brake heretofore described is of a so-called floating caliper type or of a type wherein a fixed pad or a pad secured to caliper main body is applied on the rotatable disc with the caliper main body being displaced by reaction force, but it will be noticed that the present invention may be applied to the disc brakes of the type comprising a main body secured to a nonrotatable part of a vehicle, two pistons disposed in the main body, a movable pad actuated by one of the pistons, a displaceable member called a yoke which is displaceable relative to the main body, and fixed pad secured to the yoke. The yoke in the latter case corresponds to the caliper main body 1 in the presently illustrated embodiment. WHAT WE CLAIM IS:-

1. A disc brake comprising two guide pins mounted on a caliper main body for supporting and guiding a fixed pad and a movable pad, each pad comprising a friction pad and backing plate therefor, pad actuating means being arranged to move the movable pad slidably on the guide pins toward one surface of a rotatable disc when applying the brake, with the fixed pad being immobile with respect to the guide pins, a pad spring being disposed between the guide pins and the pads, wherein the pad spring comprises a main body portion with one end portion thereof engaging with the periphery of the fixed pad and the other end portion thereof engaging with the periphery of the movable pad, two arm portions projecting from the main body portion to abut on the undersides of the guide pins respectively and thereby urge the main body portion of the spring against the pads, and a projection formed on the one end portion of the main body portion to extend between the face of the fixed pad backing plate remote from the fixed friction pad and the adjacent portion of the caliper so that the fixed pad backing plate lies between the projection and said two arm portions thereby to locate the pad spring relative to the fixed pad.