Disc brake caliper

Abstract

A disc brake (10) of the type including a pivoting lever having eccentric journals which act on a pair of tappets is disclosed. The tappets are adjusted in length by rotation, and each tappet has a tappet gear (22). A centrally located intermediate gear (24) is provided between the tappet gears to form a gear train, synchronizing the rotation of the two tappets and therefore ensuring that they remain the same length. The centrally located intermediate gear (24) includes a socket (26) for receiving a centrally located adjuster. The adjuster may be installed and removed from the disc brake through an aperture at the rear of the brake caliper, without any substantial disassembly of the brake and without de-synchronizing the tappets or even interrupting the gear train between the tappets.

Claims

1. A brake caliper, including a brake caliper housing and a brake application unit disposed within the caliper housing, the application unit comprising a pivoting lever, first and second tappets for transmitting force from the pivoting lever to a brake pad, the tappets each being formed in two threaded tappet sections and being adjustable in length by means of rotating one tappet section relative to the other tappet section, and a gear train including first and second respective tappet gears for synchronising rotational movement of the first and second tappets, an intermediate coupling gear disposed substantially centrally between the first and second tappet gears as part of the gear train, the coupling gear including means for removably receiving an output shaft of a substantially centrally disposed adjuster and for transmitting rotation from the adjuster to the first and second tappet gears, and the brake caliper housing being provided with an aperture in a rear wall, for allowing removal and replacement of the adjuster; in which a plug is provided for closing the aperture in the rear wall of the caliper housing, and in which the plug includes a bearing formation for supporting a rotatable shaft of the adjuster.

2. A brake caliper as claimed in claim 1, in which the adjuster can be removed without desynchronizing the tappets.

3. A disc brake for a vehicle, including a brake caliper as claimed in claim 1, a brake disc, and a brake pad.

4. A brake caliper as claimed in claim 1, in which the pivoting lever includes an eccentric journal.

5. A brake caliper as claimed in claim 4, in which the pivoting lever includes an eccentric journal associated with each tappet.

6. A brake caliper as claimed in claim 4, in which the eccentric journals are disposed substantially axially in-line with the tappets.

7. A brake caliper as claimed in claim 6, in which the eccentric journals act directly on the tappets.

8. A brake caliper as claimed in claim 1, in which the pivoting lever is substantially wishbone-shaped.

9. A brake caliper as claimed in claim 8, in which the arms of the wishbone-shaped pivoting lever are sufficiently widely spaced to allow an adjuster to be introduced into the intermediate coupling, between the arms of the pivoting lever.

10. A brake caliper as claimed in claim 1, in which the intermediate coupling gear includes a socket.

11. The brake caliper as claimed in claim 10, in which the socket includes interior splines for receiving a cogwheel on an output shaft of an adjuster.

12. A brake caliper as claimed in claim 1, in which the brake caliper housing is formed as a front piece and a rear piece.

13. A brake caliper as claimed in claim 1, in which an opening is provided in the front side of the rear piece of the housing for allowing assembly of the application unit.

14. A brake caliper as claimed in claim 13, in which the opening is closed by a cover plate.

15. A brake caliper as claimed in claim 14, in which hollow sleeves extend rearwardly from the cover plate, within which the tappets may slide.

16. A brake caliper as claimed in claim 1, in combination with a replaceable adjuster.

Description

DESCRIPTION OF THE DRAWINGS

(1) In order to provide a better understanding of the present invention, a preferred embodiment will now be described, by way of example only, with reference to the drawings, in which:

(2) FIG. 1 shows a perspective view of a brake caliper including the application unit of the invention, the rear part of the housing being cut away to show the application unit which includes a pivoting lever;

(3) FIG. 2 shows the application unit of FIG. 1, without the pivoting lever;

(4) FIG. 3 shows a perspective cut-away view of an intermediate coupling, which forms part of the application unit of FIG. 1;

(5) FIG. 4 shows a cross-section through the brake caliper of FIG. 1;

(6) FIG. 5 shows a cross-section through the brake caliper, as in FIG. 4, but showing an adjuster and plug installed; and

(7) FIG. 6 is a rear plan view of the brake caliper of FIG. 1, without the housing cut away.

DESCRIPTION OF THE PREFERRED EMBODIMENT

(8) Referring firstly to FIG. 1, a brake caliper is shown generally at 10. In this embodiment, the caliper housing is formed in two parts, with a front section 11 and a rear section (13). The rear section is cut away in FIG. 1 to reveal a brake application unit 12 which is housed within the rear section (13). The rear section (13) of the brake caliper has an opening in its front surface, which is closed by a cover plate 36. It will be understood that alternative embodiments of the invention may include single-piece brake housings.

(9) As best seen in FIGS. 4 and 5, the cover plate 36 includes rearward protrusions which form hollow cylinders 40, extending into the rear section 13 of the housing. A pair of tappets 18 slide within the cylinders 40. It is the tappets (18) which push onto the brake lining, and in turn the brake pad. Each tappet 18 is formed as a front tappet section 32 and a rear tappet section 34. The rear tappet section 34 is rotatable within the front tappet section 32, and there is a screw thread between the sections 32, 34. In this way, each tappet 18 may be adjusted in length by rotating the rear tappet section 34, and holding the front tappet section 32 against rotation. Each front tappet section 32 is held to its associated hollow cylinder 40 by a locking ring 38. Therefore, rotating the rear tappet sections changes the overall length of the tappets.

(10) The purpose of the application unit 12 is to transmit force from an actuating cylinder of a braking system (typically this is a hydraulic or pneumatic system) to the tappets and then to the brake lining and brake pad.

(11) The application unit 12 includes an operating shaft 14 which is in the form of a wishbone-shaped pivoting lever, and has at one end 14a a bearing surface which in use is pushed by an actuating cylinder, and at the other end 15b a pair of eccentric journals 16 which in use amplify the force from the actuating cylinder and transfer it to tappets (18).

(12) FIG. 2 shows the same view as FIG. 1, but without the pivoting lever 14. The adjustment and synchronization mechanism can therefore be clearly seen in this Figure. Tappet gears 22 are provided on the rear end of each tappet. Rotating these gears rotates one tappet section 34 with respect to the other tappet section 32, therefore changing the length of the tappet 18. The threads of both tappets are of the same pitch, so that for a given rotation the front tappet sections advance the same distance. A gear train is provided between the tappet gears 22, which in this embodiment comprises a single intermediate gear 24, which is formed integrally as part of an intermediate coupling 26. It will be understood that the intermediate gear may be in an alternative form, for example it may be in two pieces.

(13) The intermediate coupling 26 is more clearly shown in the cutaway view of FIG. 3, and is generally in the form of an elongate socket with the intermediate gear 24 extending from and surrounding an edge of the open end of the socket. A portion of the socket is provided with splines 30, which run along the interior surface of the socket, substantially parallel to its longitudinal axis.

(14) An apertured plate 28 is provided between the tappets 18 and the tappet gears 22. The plate 28 has three substantially circular apertures, and the tappet gears 22 connect to the tappets 28 through the outer two of the three apertures. The central aperture of the three is sized to receive the intermediate coupling 26. The plate 28 provides a bearing surface for the tappet gears 22 and the gear train, which in this embodiment is just the intermediate gear 24 of the intermediate coupling 26.

(15) Return springs 20 are provided surrounding the cylinders 40, between the cover plate 36 and the apertured plate 28. The return springs 20 urge the apertured plate 28 away from the cover plate 36, and hence force the tappets 18 rearwardly into the brake housing. When the brake is applied, the actuating cylinder pushes the bearing surface 14a of the pivoting lever 14 forwards, towards the disc. The lever 14 pivots, and the eccentric journals 16 rotate in seats which formed into the interior of the rear hosing section 13 of the caliper, and push on both tappets 18 together. Tappet bearings 48 are provided between the journals 16 and tappet gears 22 and are in the form of cylinders, the longitudinal axes of which are perpendicular to the tappets 18. The bearings 48 can slide or roll on the flat surface of the tappet gears 22, so that the bearings 48 remain substantially horizontal as the tappets 18 rotate to keep the brake adjusted. The tappets 18, as well as the gear train 22, 26 and apertured plate 28, all move forwards against the springs 20, pushing the brake pad against the brake disc. When the brake is released, the springs 20 return the tappets 18, gear train 22, 26 and apertured plate 28 to their rearward rest position.

(16) The overall arrangement of the tappets and associated gear train is shown in FIG. 4 and FIG. 5. FIG. 4 shows a cross section through the brake caliper 10 with no adjuster fitted, and FIG. 5 shows the same cross section with an adjuster 42 fitted. The adjuster is of a design which will be familiar to the person skilled in the art. In this embodiment a simple mechanical adjuster is shown, including a one-way sprag clutch and an over-torque clutch. An operating pin 44 (seen in FIG. 1) on one of the eccentric journals 16 of the pivoting lever 14 engages with a toothed wheel of the adjuster. The pin can move to a certain degree with respect to the journal, for example, 1 mm of freedom may be provided. This defines the running clearance of the brake. If the journal moves further than that, the operating pin 44 turns the toothed wheel through a few degrees. This rotation is transmitted to the intermediate coupling 26, via the one-way clutch and over-torque clutch of the adjuster 42. In this way, the tappets 18 are extended slightly with each application of the brake. The one-way clutch means that the tappets 18 will only ever be lengthened, never shortened, on brake application, and the over-torque clutch prevents over-adjustment during very heavy braking, when the brake pads, caliper housing and other brake components may exhibit elastic behaviour.

(17) The adjuster 42 can easily be removed from the application unit 12, without disturbing the synchronization between the tappets 18. If the adjuster 42 is removed, the intermediate coupling 26 remains in place, so that the gear train is not interrupted. FIG. 6 shows a rear view of the brake caliper 10, including the rear section 13 of the housing. The rear housing section 13 has an aperture 44 in its rear face, which allows the adjuster to be completely withdrawn without any disassembly of the brake. A plug 50 is provided to hold the adjuster in place and to close the aperture in the rear wall of the caliper. The plug can be removed to release the adjuster 42 and remove it from the brake, and includes a bearing formation for receiving and supporting the back end of the adjuster 42.

(18) The plug may be a press fit, screw fit, or any other type of plug.

(19) The adjuster can be removed from the brake without any substantial disassembly, and without de-synchronizing the tappets. This is particularly surprising bearing in mind that this is a disc brake which is assembled through an opening in the caliper on this disc side, and provides for a significant advantage. For example, it may be desirable to supply brakes without an installed adjuster 42, so that the OEM customer has a choice of adjuster, depending on specific requirements. For example, electric adjusters may be provided as an option on particular vehicles, and vehicles with simple mechanical adjusters can be upgraded to use electric adjusters without disassembly of the brake. Electric adjusters allow for active clearance control, and can provide for better overall braking performance.

(20) In the brake application unit described, the eccentric journals on the pivoting lever operate directly on the tappets, ensuring that brake application is even and is fully perpendicular to the brake disc. The central position of the adjuster allows for this, and the intermediate coupling allows the central adjuster to be easily replaced. A further advantage of the central adjuster is that the tappets are rotated (and therefore extended) by substantially equal amounts. In any side adjuster design, backlash in the gear train will lead to slight differences in length between the tappets, resulting in uneven brake application.

(21) The embodiments described above are provided by way of example only, and various changes and modifications will be apparent to persons skilled in the art without departing from the scope of the present invention as defined by the appended claims.