GB2239066A

GB2239066A - Disc brake

Info

Publication number: GB2239066A
Application number: GB9025218A
Authority: GB
Inventors: Kinzo Kobayashi; Shinichi Nakayama
Original assignee: Tokico Ltd
Current assignee: Tokico Ltd
Priority date: 1989-11-20
Filing date: 1990-11-20
Publication date: 1991-06-19
Also published as: JPH0373733U; GB9025218D0

Abstract

A sliding caliper disc brake for a vehicle, comprising a stop member 11 secured to the caliper and engageable by a projection 10b formed on a brake lever 10 to prevent further rotation of the brake lever in the return direction 'A' under the bias of return spring 13b is characterised in that the return spring includes an extension 13c extending outward and then downward (13d Fig 7) from the end 13a, the downward portion (13d) acting as an abutment for an additional lever projection 10f to prevent further rotation of the lever upon brake application in the direction 'C'. The downward portion (13d) is supported by a projection (1b) formed on the side of the caliper. Portion 10e of the lever is preferably in the form of a cut out to permit assembly of the lever past a flange 11b. <IMAGE>

Description

DISC BRAKE The present invention relates to a disc brake, and more particularly to a disc brake provided with a hand-brake operating mechanism.

Figs. 1 - 3 show in conjunction an example of conventional disc brakes of the type as mentioned above.

Shown at 1 is a caliper slidably supported on a carrier 1B by means of a pair of slide pins 1A. The carrier 1B is fixedly secured to a stationary portion of the vehicle body (not shown) at one side of a disc 8 adapted to rotate with a wheel of the vehicle. A pair of friction pads, inner and outer pads 7a and 7b, respectively, are located on the opposite sides of the disc 8 and supported slidably and axially in relation to the disc 8 by the carrier 1B. The caliper 1 is provided with a cylinder portion 3A and an arm portion 1D extending from the cylinder portion 3A over the disc 8 and the friction pads 7a, 7b. A claw portion 1E extends downward from the remote end of of the arm portion 1D to engage with the reverse surface of the outer pad 7b.

Reference numeral 3 designates a cylinder formed in the cylinder portion 3A of the caliper 1 in which two pistons or inner and outer pistons are disposed in series. The two pistons abut against each other through a gap adjusting member (not shown) disposed therebetween. The piston designated by reference numeral 2 in Fig. 3 is the outer piston.

The inner piston (not shown) is adapted to abut against the inner pad 7a to move it.

The caliper 1 is also provided with a lever guide 4 extending rearwardly from the cylinder portion 3A. The caliper 1 is further provided with a rotatable cam shaft 5 mounted thereon to stand perpendicularly to the axis of the cylinder 3. A connecting rod 6 is disposed between the cam shaft 5 and the outer piston 2 so that the rotating movement of the cam shaft 5 is converted to the axial linear movement of the piston 2 through the connecting rod 6. Shown at 9 is an upper or protruding portion of the cam shaft 5 which protrudes to the outside of the caliper 1 and on which a brake lever 10 is fixedly mounted for rotating the cam shaft 5.

Reference numeral 11 designates a stop for the brake lever 10 fixedly planted in the caliper 1 near the cam shaft 5 to stand upright. The stop 11 comprises a rod portion lla and a flange 11b formed in the middle of the rod portion lla.

The brake lever 10 is provided with a flange contacting portion lOa formed with an arcuate periphery and a projection lOb located adjacent to the flange contacting portion 10a and radially outwardly projecting. The flange llb of the stop 11 is designed to partially overlie the flange contacting portion l0a to prevent the cam shaft 5 and the brake lever 10 from becoming dismounted from the caliper 1. The projection lOb is adapted to abut against the rod portion 11a of the stop 11 below the flange 11b to prevent further rotation of the cam shaft 5 when the brake lever 10 is rotated in the direction designated by arrow A in Fig. 2 by means of a return spring 13 which is to be explained later. The brake lever 10 is provided with a hook lOc to which one end of a cable 12 is connected.The cable 12 extends through a groove 4b formed in an extending end 4a of the lever guide 4 and the other end of the cable is connected to a hand brake lever (not shown) disposed near the driver's seat. A boot 12a is disposed between the hook 1Oc of the brake lever 10 and extending end 4a of the lever guide 4 to shield the cable 12 therebetween.

The coiled return spring 13 fits around the protruding portion 9 of the cam shaft 5 above the brake lever 10.

The return spring 13 constantly biases the brake lever 10 in the direction designated by arrow A with a lower end 13a thereof engaging with the rod portion lla of the stop 11 above the flange llb and with an upper end thereof engaging with a projection 1Od formed on the brake lever 10. As mentioned before, the flange lib of the stop 11 functions to prevent the cam shaft 5 and the brake lever from becoming dismounted from the caliper, and it further advantageously functions to prevent wear of the brake lever 10 and spring 13 since the flange 11b is located between the brake lever 10 and the lower end 13a of the return spring to prevent the two parts from being in direct contact with each other.

In operation, the cable 12 is pulled in the direction designated by arrow B in Fig. 2 when the driver pulls the hand-brake lever, thereby rotating the brake lever 10 in the direction designated by arrow C against the force of the return spring 13. At that time, the cam shaft 5 is also rotated in the same direction to displace the aforementioned two pistons in the axial direction thereof through the connecting rod 6, thereby pressing the inner pad 7a onto one side surface of the disc 8. Simultaneously, the caliper 1 is displaced in the opposite direction to that of the pistons by virtue of the reaction force generated at that time so that the outer pad 7b is pressed onto the opposite side surface of the disc 8. Thus, the disc brake functions as a parking brake.

When the disc brake is operated as a foot brake, a brake pedal may be pressed down so that pressurized oil is supplied between the two pistons from a master cylinder (not shown). The inner piston in the cylinder 3 displaces and presses the inner pad 7a onto the one side surface of the disc 8 while the caliper 1 is displaced in the opposite direction to that of the inner piston in the cylinder 3 by virtue of the reaction force to press the outer pad 7b onto the opposite side surface of the disc 8.

However, the disc brake of the type explained above suffers from the following problem.

When the cable 12 is inadvertently excessively pulled, the brake lever 10 may be also rotated excessively.

The excessive rotation of the brake lever causes the boot 12a to be compressed excessively, thereby damaging the boot 12a.

In order to solve the above problem, one solution may be to form on the brake lever 10 another projection opposed to the aforementioned projection lOb so that the another projection abuts against the stop 11 to prevent excessive rotation of the brake lever 10 in the direction designated by arrow C in Fig. 2. However, for the following reason, this idea cannot be adopted. In the disc brake of the above-mentioned type, it is usual, under the requirement of efficiency in assembly operation, that the stop 11 with the flange llb is first press-fitted in the caliper and, after that, the brake lever 10 is mounted on the cam shaft 5.If the above-mentioned idea were adopted, the brake lever 10 would have to be provided with an avoiding portion or cutout formed between the projection lOb and the another projection for avoiding and allowing the flange 11b to pass therethrough when the brake lever 10 is mounted on the cam shaft 5. In that case, the stop means cannot prevent the brake lever 10 from moving upward to directly engage with the return spring 13. The above-mentioned solution cannot, therefore, be adopted.

Accordingly, an object of the present invention is to provide a disc brake in which excessive rotation of a brake lever can be reliably prevented.

In order to achieve the above-described object, the present invention provides a disc brake for use in the brake system of a vehicle comprising a carrier fixedly secured to a stationary portion of a vehicle body, a caliper slidably supported on the carrier, a pair of friction pads located on the opposite sides of a rotating disc and supported slidably axially of the disc by the carrier, a piston slidably received in a cylinder formed in the caliper, the piston being adapted to abut against one of the pair of friction pads, a cam shaft rotatably mounted on the caliper with an upper portion thereof extending from the caliper, the cam shaft being operable to axially displace the piston, a brake lever fixedly secured to the upper portion of the cam shaft, the brake lever being operable to rotate the cam shaft, a return spring in the form of a coil mounted to surround the upper portion of the cam shaft above the brake lever, one end of the return spring engaging with the brake lever while the other end of the return spring being held in a predetermined position on the caliper so that the return spring biases the brake lever in one direction around the axis of the cam shaft, and a stop member in the shape of a rod fixedly secured to the caliper, the stop member being engageable with a projection formed on the brake lever to prevent further rotation of the brake lever in the one direction, the stop member being provided with a flange formed midway thereof, the flange being disposed between the return spring and the brake lever; characterized in that the return spring further includes an extension extending from the other end in the one direction where the return spring biases the brake lever and further being bent to extend downward and that the brake lever is further provided with another projection for abutting against the extension of the return spring to prevent further rotation of the brake lever in the opposite direction around the axis of the cam shaft.

Fig. 1 is a perspective view showing a conventional disc brake; Fig. 2 is a plan view of the conventional disc brake; Fig. 3 is a sectional view taken along line 3 - 3 in Fig. 2; Fig. 4 is a partial plan view showing a disc brake of a preferred embodiment of the present invention; Fig. 5 is a similar view to Fig. 4 but showing the disc brake in its actuated condition; Fig. 6 is a perspective view of the disc brake shown in Fig. 4; and Fig. 7 is a side view of the disc brake shown in Fig. 4.

Referring to Figs. 4 to 7, a preferred embodiment of the present invention will be explained. The same reference numerals will be given to the same elements as those of the conventional disc brake explained above and detailed explanation thereof will be omitted.

A return spring 13 employed in the present embodiment is similar to the one of the conventional disc brake above explained and in the shape of a coil. The return spring 13 fits around a protruding portion 9 of a cam shaft 5 with an upper end 13b thereof engaging with a projection lOd formed on a brake lever 10 and with an lower end 13a thereof engaging with a stop 11. The stop 11 is provided with a flange 11b formed midway thereof and a head 11c formed at the top thereof. The lower end 13a of the return spring engages with the stop 11 between the flange lib and the head llc.

The return spring is further provided with an extension 13c extending from the lower end 13a in the direction designated by arrow A in Fig. 4 and further bent downward.

The downward end 13d reaches a side la of a caliper 1.

The brake lever 10 is provided with a flange contacting portion 1Oa and a projection lOb which function in the same manner as those of the conventional disc brake explained above.

The brake lever 10 of the present embodiment is further provided with an another projection lOf and an avoiding portion or cutout portion 1Oe formed between the another projection and the flange contacting portion 1Oa.

The cutout 10e enable the brake lever 10 and the cam shaft 5 to be mounted on the caliper 1 after the stop 11 is pressfitted in the caliper 1. When the brake lever 10 is rotated in the direction designated by arrow C in Fig. 4, the projection lOf abuts against the extension 13c of the return spring to prevent further rotation of the brake lever 10.

Namely, the maximum rotational stroke of the brake lever 10 is defined by the distance between the extension 13c and the projection 10f when the brake is not operated (Fig. 4), which distance is designated by reference symbol S in Fig. 4.

Shown at ib is a projection formed on the side la of the caliper 1. When the projection lOf of the brake lever 10 abuts against one side of the downward end portion 13d of the extension 13c, the projection lb of the caliper 1 acts to support the downward end portion 13d on the opposite side thereof.

Operation of the disc brake with the above-explained construction will now be explained.

In the condition where the brake is not actuated, the stop 11 abuts against the projection 10b of the brake lever 10.

When the driver pulls up the hand-brake lever, the cable 12 is pulled in the direction designated by arrow B and the brake lever 10 is, in turn, rotated in the direction designated arrow C against the force of the return spring 13. Simultaneously, the cam shaft 5 is rotated in the same direction to displace the piston in the cylinder, thereby pressing the friction pads onto each side of the disc.

Thus, the disc brake functions as a parking brake. At that time, the projection lOf of the brake lever 10 abuts against the extension 13c of the return spring 13 to prevent any excessive rotation of the brake lever 10, so that the cable 12 is prevented from being excessively pulled. The boot 12a does not, therefore, receive any excessive compressive force and thus keep a long life. Since the extension 13c of the return spring 13 is supported at the opposite ends thereof, namely the lower end 13a and the downward end 13d, by means of the stop 11 and the projection lb, respectively, the extension 13c is prevented from being bent when the projection 10f of the brake lever 10 abuts against the extension 13c.

When the hand-brake lever is released, the brake lever 10 is rotated in the direction designated by arrow A by virtue of the force of the return spring 13 until the projection 10b abuts against the stop 11.

According to the present invention, any excessive rotation of the brake lever 10 is reliably prevented. The present invention does not require any new element to be added to the conventional disc brake, and it is only necessary that the return spring 13 and the brake lever 10 are respectively formed with the extension 13c and the another projection lOf and the cutout lOe. The disc brake can, therefore, be assembled in the same manner as in the case of the conventional disc brake, thereby avoiding any rise in the manner of assembly steps or consequent rise in manufacturing costs.

Claims

We claim:

1. A disc brake for use in the brake system of a vehicle comprising: a carrier fixedly secured to a stationary portion of a vehicle body; a caliper slidably supported on said carrier; a pair of friction pads located on the opposite sides of a rotating disc and supported slidably axially of said disc by the carrier; a piston slidably received in a cylinder formed in said caliper, said piston being adapted to abut against one of said pair of friction pads; a cam shaft rotatably mounted on said caliper with an upper portion thereof extending from said caliper, said cam shaft being operable to axially displace said piston; a brake lever fixedly secured to said upper portion of the cam shaft, said brake lever being operable to rotate said cam shaft;; a return spring in the form of a coil mounted to surround said upper portion of the cam shaft above said brake lever, one end of said return spring engaging with said brake lever while the other end of said return spring being held in a predetermined position on the caliper so that said return spring biases said brake lever in one direction around the axis of said cam shaft; and a stop member in the shape of a rod fixedly secured to said caliper, said stop member being engageable with a projection formed on said brake lever to prevent further rotation of said brake lever in said one direction, said stop member being provided with a flange formed midway thereof, said flange being disposed between said return spring and brake lever; characterized in that said return spring further includes an extension extending from said the other end in said one direction where said return spring biases said brake lever and further being bent to extend downward and that said brake lever is further provided with another projection for abutting against said extension of said return spring to prevent further rotation of said brake lever in the opposite direction around the axis of the cam shaft.

2. A disc brake according to Claim 1, characterized in that said stop member is further provided with a head formed on the top thereof, and that said other end of the return spring abuts against the stop between the flange and the head.

3. A disc brake according to Claim 1, characterized in that said caliper is provided with a projection formed on a side thereof for supporting the downward extending portion of the extension of the return spring when said another projection of the brake lever abuts against the extension.

4. A disc brake substantially as described herein with reference to and as illustrated in Figures 4 to 7 of the accompanying drawings.