Title of Invention: Shear-damped disc brake
Abstract: A sliding caliper disc brake for a motor vehicle having a disc, a carrier (2), a caliper (3) and pads (52). The carrier (2), respectively, provides bearing surfaces (61b, 63b) for the caliper (3) and pads (52) having a non-zero angle (Ab) which opposes rotational movement between the caliper (3) and pads (52) when the disc turns in a direct sense (D). Thus, a resistance to a braking torque generated during braking is dampened by a shear force developed between the caliper (3) and pads (52).
Detailed Description: Part PAC: DETAILED DESCRIPTION OF THE INVENTION
Part PAR: As FIG. 1 shows, the invention applies to a disc brake for a motor vehicle, of the type which comprises, in the known way, a disc 1, a carrier 2, a caliper 3, guide means 41, 42, 43, 44 provided on the carrier 2 and on the caliper 3, and a pair of friction pads which is formed of an inboard pad 51 and an outboard pad 52.
Part PAR_2: For reasons of clarity, the disc is assumed to turn from left to right in all the figures, which means that if FIGS. 1, 2, 5 and 6 are assumed to depict a brake mounted on the left-hand side of a vehicle, then FIGS. 3 and 4 must be considered as depicting a brake mounted on the right-hand side of this vehicle.
Part PAR_3: The disc 1 has an inboard face 11 and an outboard face 12 and is rotated, with a wheel of the vehicle, about a transverse axis X in a direct sense of rotation D when the vehicle is travelling forward.
Part PAR_4: The carrier 2 comprises an upstream branch 21 and a downstream branch 22 which both straddle the disc 1 and which are secured to a common base 23 of the carrier, the latter being fixed to the vehicle facing the inboard face 11 of the disc, for example by means of bolts inserted in orifices 231 and 232.
Part PAR_5: By convention, the downstream branch 22 is here defined as being the one which follows on from the other, known as the "upstream branch 21" in the direct sense of rotation D of the disc.
Part PAR_6: Furthermore, as best shown in FIG. 5, each branch has an inboard housing 211, 221 and an outboard housing 212, 222, the inboard and outboard housings lying one on either side of the disc 1.
Part PAR_7: The caliper 3, which straddles the disc 1 also, is mounted so that it can slide relative to the carrier 2, in a transverse direction T parallel to the transverse axis X.
Part PAR_8: This caliper 3, which acts as a gripper, essentially comprises a jaw 32 pointing towards the outboard face 12 of the disc, and a cylinder 31 lying on the same side as the inboard face 11 of the disc and closed by a piston 311.
Part PAR_9: The guide means 41, 42, 43 and 44 are formed in pairs, each pair comprising a bore and a pin mounted so that it can slide in this bore.
Part PAR_10: In the prior art illustrated in FIG. 1, the guide means 41 and 43 provided on the carrier consist of two pins, the guide means 42 and 44 provided on the caliper 3 then consisting of two bores.
Part PAR_11: The inboard pad 51 is placed, in the transverse direction T, between the piston 311 and the inboard face 11 of the disc, and has an upstream end 511 and a downstream end 512 which are mounted so that they can slide in the respective inboard housings 211, 221 of the upstream and downstream branches 21, 22.
Part PAR_12: Similarly, the outboard pad 52 is placed between the outboard face 12 of the disc and the jaw 32 of the caliper, and has an upstream end 521 and a downstream end 522 which are mounted so that they can slide in respective outboard housings 212, 222 of the upstream and downstream branches 21, 22.
Part PAR_13: Moreover, the inboard and outboard pads 51, 52 carry, between their respective ends, friction linings 510, 520, the lining 510 of the inboard pad facing towards the inboard face 11 of the disc 1, and the lining 520 of the outboard pad facing towards the outboard face 12 of the disc.
Part PAR_14: When pressurized brake fluid is injected into the cylinder 31 and pushes the piston 311 towards the disc 1, this piston presses the pad 51 against the inboard face 11 of the disc, the result of which is that the cylinder 31 is forced away from the disc until the jaw 32 presses the outboard pad 52 onto the outboard face 12 of the disc with an equivalent force.
Part PAR_15: If, during this operation, the vehicle is travelling forwards, the pads 51 and 52 therefore receive from the disc, and via their linings 510 and 520 which rub on the latter, a force which urges them in the direct sense of rotation D and which has to be absorbed by the carrier 2, the purpose of the invention being precisely to propose special means for facilitating this absorption.
Part PAR_16: To this end, the brake of the invention comprises just one pair of guide means, that is to say a single pin 41 sliding in a single bore 42, it being possible for the pin 41 and the bore 42 to be provided on the carrier and on the caliper respectively or vice versa with equal ease, provided that they are placed in the mid-plane of the caliper 3, that is to say in the plane which, in scenarios in which the brake comprises just one single central piston as illustrated, consists of the plane of the line M passing through the axis X of rotation of the disc and through the axis of symmetry of revolution of the piston 311.
Part PAR_17: Furthermore, the downstream branch 22 of the carrier and the jaw 32 of the caliper have first and second respective contact surfaces such as 61a, 62a in FIG. 3, and 61b, 62b in FIG. 4, which when the brake is actuated can come to bear one against the other in a first oblique plane such as P1a in FIG. 3 and P1b in FIG. 4.
Part PAR_18: Also, the downstream branch 22 of the carrier and at least one of the pads, for example the outboard pad 52, have third and fourth respective contact surfaces such as 63a, 64a in FIG. 3, and 63b, 64b in FIG. 4, which when the brake is actuated, can come to bear one on the other in a second oblique plane such as P2a in FIG. 3, and P2b in FIG. 4.
Part PAR_19: Finally, as FIGS. 3 and 4 show, the first and second oblique planes such as P1a and P2a, or P1b and P2b, form a non-zero angle such as Aa or Ab between them, preferably at least equal to 45 degrees.
Part PAR_20: A spring 7, for example fixed to the outboard pad 52 and bearing in notches 321 and 322 of the jaw 32 of the caliper, is preferably designed to exert an elastic torque tending to make the caliper 3 turn in the direct sense of rotation D relative to the outboard pad 52.
Part PAR_21: An examination of FIGS. 3 and 4, which deal with the same brake observed in different phases of braking, allows a better understanding of the invention.
Part PAR_22: As shown in FIG. 3, which corresponds to actuation of the brake with a low braking torque, the caliper is forced, if driven in the direct sense of rotation indicated by the arrow D, to follow a rotational movement in this direct sense D by the bearing of the contact surface 62a on the contact surface 61a, while the outboard pad 52 is forced, if driven in the direct sense D, to follow a rotational movement in the opposite sense to this direct sense D by the bearing of the contact surface 64a on the contact surface 63a.
Part PAR_23: However, as the caliper 3 grips the outboard pad 52, it actually has a pronounced tendency to follow the movements of this pad.
Part PAR_24: This being the case, the natural driving of the caliper 3 by the pad 52 and the opposing effects of the caliper 3 and of the outboard pad 52 bearing on the carrier 2 generate a shear force between the caliper 3 and the pad 52, and this results in easier absorption of the braking torque.
Part PAR_25: Likewise, as shown by FIG. 4 which corresponds to brake actuation with a high braking torque, the caliper is forced, if driven in the direct sense of rotation indicated by the arrow D, to follow a rotational movement in the opposite sense to the direct sense D by the bearing of the contact surface 62b on the contact surface 61b, while the outboard pad 52 is forced, if driven in the direct sense D, to follow a rotational movement in this same direct sense D by the bearing of the contact surface 64b on the contact surface 63b.
Part PAR_26: In the latter case, the natural driving of the caliper 3 by the pad 52 and the opposing effects of the caliper 3 and of the outboard pad 52 bearing on the carrier 2 therefore also generate a shear force between the caliper 3 and the pad 52, and allows better absorption of the braking torque.
Part PAR_27: As it is advantageous to combine the effects obtained by the invention in the case of relatively gentle braking torques and in the case of relatively high braking torques, it may be beneficial, as shown in FIGS. 3 and 4, to contrive for the downstream branch 22 of the caliper to have a pair 61a, 62b of first contact surfaces forming a dihedron P1a, P1b of mutual contact between the downstream branch and the jaw 32, and a pair 63a, 63b of third contact surfaces forming a dihedron P2a, P2b of mutual contact between the downstream branch and the outboard pad 52.
Part PAR_28: This being the case, the jaw 32 of the caliper preferably has, facing the downstream branch 22 of the carrier, a second pair of contact surfaces 62a, 62b each of which is capable of coming to bear on the dihedron P1a, P1b of mutual contact between the downstream branch 22 of the carrier and the jaw 32.
Part PAR_29: Likewise, it is advantageous to contrive for the downstream end 522 of the outboard pad 52 to have, facing the downstream branch 22 of the carrier, a pair of fourth contact surfaces 64a, 64b, each of which is capable of coming to bear on the dihedron P2a, P2b of mutual contact between the downstream branch 22 of the carrier and this outboard pad 52.
Part PAR_30: Brake balance can furthermore be improved by arranging the contact surfaces 61a, 61b of the carrier 2, and 62a, 62b of the jaw 3, exclusively on the outboard part 220 (FIG. 5) of the carrier and on the corresponding outboard part 320 (FIG. 2) of the jaw.
Part PAR_31: The effectiveness of the arrangement proposed may also be enhanced by attaching the upstream end 511, 521 of at least one of the inboard 51 and outboard 52 pads, and preferably of both pads, to the upstream branch 21 of the carrier, for example by means of complementary respective reliefs such as 212a and 521a (FIG. 4).
Part PAR_32: Finally, the effects of the invention may also be enhanced by contriving for the inboard pad 52 itself also to have a pair of contact surfaces capable of coming to bear on the carrier, these surfaces then being symmetric with respect to the disc 1 with the contact surfaces 64a, 64b of the outboard pad 52.


{'bibliographic_information': "{'Patent Number': '062504401', 'Series Code': '9', 'Application Number': '2699885', 'Application Type': '1', 'Art unit': '363', 'Application Filing Date': '19990405', 'Title of Invention': 'Shear-damped disc brake', 'Issue Date': '20010626', 'Number of Claims': '7', 'Exemplary Claim Number(s)': '1', 'Primary Examiner': 'Butler; Douglas C.', 'Number of Drawing Sheets': '3', 'Number of figures': '6'}", 'source_file': './grant/2001/pftaps20010626_wk26.txt', 'source_data': 'USPTO-Grant'}