Piston Roll Back Device

• US 20110233008A1
• Filed: 12/02/2008
• Published: 09/29/2011
• Est. Priority Date: 12/02/2008
• Status: Active Grant

• Current Assignee: Brembo SPA (Nuova Fourb Srl)
• Original Assignee: Freni Brembo S.P.A.
• Inventors: Lenzi, Luca, Crippa, Cristian, Cesani, Paolo
• Granted Patent: US 8,376,101 B2
• Time in Patent Office: Days
• US Class Current: 188/72.3
• CPC Class Codes: F16D 2121/02 Fluid pressure
• CPC Class Codes: F16D 2127/02 Release mechanisms
• CPC Class Codes: F16D 65/18 adapted for drawing members together , e.g. for disc brakes

Abstract

A brake caliper comprising a piston seat (10) wherein a piston (2) slides with its side surface (11) in contact with a radial surface (13) of an elastic member (12). The member further comprising two axial surfaces (15,16) adapted to be affected by a pressurized fluid and being arranged at the piston coming out side facing the pads respectively. The latter surface facing with a portion (17) thereof, a first chamber (18) arranged in the proximity of the piston side surfaces, with another portion (24) thereof, an abutment surface (19) adapted to support said elastic member when it is urged by the pressurized fluid, said abutment surface being radially retracted so as to be farther from the piston side surface than said first chamber and with a further portion (25) thereof, at least one second chamber (20) arranged radially farther from said piston side surface than said abutment surface.

Claims

1. A device (1) for retracting a piston (2) for brake caliper (3), said brake caliper comprising a caliper body (4) located astride a brake disc (5) having a rotational axis (X-X) and opposite friction surfaces (6, 7);

pads (8, 9) which are received in said caliper body so as to be capable of sliding in the axial direction relative to the brake disc in order to act on said opposite friction surfaces, respectively, said caliper body further comprising at least one piston seat (10) adapted to receive the piston (2) provided with a side surface (11) adapted to slide within said piston seat so as to be able to be urged by a brake fluid exiting said seat in order to affect at least one of said pads against said brake disc friction surfaces, in which said device comprises;

at least one elastic member (12) arranged with a first radial surface (13) thereof being in forcible contact against said piston side surface, and with a second radial surface (14) thereof being in forcible contact against the caliper body;

said elastic member comprising a third axial surface (15) at the pressurized fluid side, facing away from said pads and adapted to be affected by the brake fluid;

said elastic member comprising a fourth axial surface (16) at the piston coming out side, facing the pads;

said elastic member with the fourth, surface thereof facing, with a portion (17) thereof, a first chamber (18) arranged in the proximity of the piston side surface, said first chamber being opened towards said piston side surface;

said elastic member with the fourth surface thereof facing, with a portion (24) thereof, an abutment surface (19) adapted to support said elastic member when urged by the pressurized fluid, said abutment surface being radially retracted so as to be farther from the piston side surface than said first chamber;

said elastic member with the fourth surface thereof facing, with a portion (25) thereof, at least one second chamber (20) arranged radially farther from said piston side surface than said abutment surface.

2. The device according to claim 1, wherein a ring (21) is further provided, which is housed in an annular seat (26) and axially sandwiched between said at least one elastic member (12) and the caliper (4) body at the side opposite the elastic member brake fluid,

said ring having an inner radial dimension (R) adapted to leave a clearance (D) between said ring and said piston side surface so as to create said first chamber (18),

said ring comprising a side surface (22) facing said at least one elastic member and adapted to create said abutment surface (19);

said ring having, in the portion thereof farthest from the piston side surface, at least one radial recess (23) axially opened at least at the side facing said at least one elastic member so as to create said at least one second chamber (20).

3. The device according to any preceding claim, wherein said first chamber (18) is annular and so sized as to receive an elastic member (12) predefined portion (100) which is urged by the movement of the piston coming out from the seat thereof of the caliper body, and which allows, when the braking action stops, returning the piston of a predefined stroke adapted to cause the piston desired retraction also following modest braking actions.

4. The device according to any preceding claim, wherein a predefined plurality of second chambers is provided, of a number and dimension adapted to receive portions (101) of the elastic member (12) as the brake fluid reaches a predefined pressure corresponding to a predefined and sensible elastic strain of the caliper (4) body.

5. The device according to any claim 2 to 4, wherein said ring is made of elastic material, for example, PTFE®

, and is Provided with a predefined number of bumps or teeth (27) which allow a sensible elastic strain when a predefined stress exerted thereon is reached which, when the braking action stops, determines an elastic return on the elastic member which drags the piston to the seat thereof in a retraction stroke.

6. The device according to any preceding claim, wherein said elastic member (12) is received in an annular seat (26), said seat comprising a bottom (28) adapted to be in forcible contact with said elastic member, said bottom comprising an inclined portion (29) so as to reduce the annular seat radial dimension at the side opposite the disc, and a cylindrical portion (30) adapted to define part of the second chamber.

7. An annular seat (26) of a caliper (3) for disc brake, said brake caliper comprising a caliper body (4) located astride a brake disc (5) having a rotational axis (X-X) and opposite friction surfaces (6, 7), pads (8, 9) being received in said caliper body so as to be capable of sliding in the axial direction relative to the brake disc in order to act on said opposite friction surfaces, respectively, said caliper body further comprising at least one piston seat (10) adapted to receive the piston (2) provided with a side surface (11) adapted to slide in said piston seat so as to be able to be urged by a brake fluid exiting said seat in order to affect at least one of said pads against said brake disc friction surfaces, wherein said seat is adapted to receive a piston retracting device according to any preceding claim.

8. A caliper comprising a retracting device according to any claim 1 to 6.

9. The caliper according to the preceding claim, wherein a caliper body is provided, having a hub side extended portion adapted to face a disc side facing a vehicle hub, a wheel side extended portion adapted to face the disc side facing a vehicle wheel, and at least two end bridges adapted to connect the ends of said hub side and wheel side extended portions, wherein the hub side and wheel side extended portions, and the at least two end bridges, are manufactured in a single piece.

10. A braking system comprising a caliper as described in any preceding claim.

11. A method for retracting a piston body of a piston provided in a caliper in order to urge at least a pad in the axial direction against a friction surface of a brake disc which faces it, and to exert a braking action, said method comprising the following steps:

providing a device (1) for returning the piston (2) according to any one of the claim 1 to 6;

arranging the elastic member (12) first radial surface (13) in contact with the piston (2) so that it is dragged by the piston movement, thus elastically straining an elastic member portion (100) in the first chamber (18), and pressing said elastic member against the abutment surface (19);

elastically straining a portion (101) far from the elastic member piston, as the brake fluid reaches a predefined pressure, inside the second chamber (20).

12. The method according to claim 11, wherein additional steps are provided as follows:

elastically returning, when the brake fluid action stops, the piston with the elastic member being in pressing contact with the piston side surface, by an amount proportional to the strain of the elastic member arranged in the first chamber (18).

13. The method according to claim 11, wherein additional steps are provided as follows:

returning, if, during the braking action, the pressure exerted on the elastic member has been reached of a predefined value which elastically strains the elastic member in the at least one second chamber having predefined dimensions, when the brake fluid action stops, the piston into the seat thereof by a further stroke via the elastic member due to this elastically strained portion thereof in the at least one second chamber by levering on the abutment surface, thus compensating the approaching of the piston to the disc resulting from the recovery of the caliper body elastic strain.

14. Method for adjusting the retraction amount imposed to a brake caliper piston, comprising the steps of:

providing a brake caliper equipped with a device according to any claim 1 to 6,

varying the dimension of the at least one second chamber so as to accommodate therein the elastic strain of the elastic member when the brake fluid reaches such a pressure which exerts in the brake caliper a predefined sensible elastic strain of the caliper, which moves it away from the disc by increasing the piston stroke.