Patent Application
20140374202
The invention concerns a guideway formed by a folded metal sheet and a spring protruding from this guideway, for a disk brake for a motor vehicle, which comprises at least one brake pad mounted sliding axially in a carrier, and disk brakes equipped with such a guideway.
In a vehicle equipped with disk brakes, each wheel to be braked comprises a brake disk integral with the wheel and brake pads integral with the chassis of the vehicle, which come to brake the disk by friction. The brake comprises a caliper with a carrier with a U-shaped branch carrying a brake pad on each side of the brake disk, and each pad is movable perpendicularly to the disk plane when guided by its two ends (lugs) in housings of the arms of the carrier.
During braking, the pads are driven in a direction tangential to the disk, and the lugs come to rest—sometimes suddenly—against the base of their guide housing, causing a clonking noise. To dampen the impact of the lugs in their housing and thus attenuate the noise, a guideway is provided between each lug and its housing, and the damping is obtained by deformation of a spring formed by a leg of the guideway, the shape of which is adapted to the force exerted by the brake pad during its tangential movement.
Motor vehicle disk brakes exist which comprise at least one brake pad which is mounted sliding in relation to a brake disk along an axially oriented slide axis in at least one guideway, between a front braking position in which a friction face of the brake pad or brake block is able to be applied to a face of the disk, and a rear rest position in which the friction face of the brake pad is remote from the face of the disk. A caliper comprises at least one application element for the brake pad which is able to stress the brake pad axially towards its braking position, wherein the guideway is fixed to a fixed carrier and comprises an axially deformable leg, comprising a guide face and a contact zone with the brake pad, and exerting a constant elastic force.
It is known to propose brake disks of the type described above in which each guideway is made from a folded metal sheet which also forms a leaf spring which is fixed to the carrier of an associated caliper, these guideways thus combining a spring function. These disk brakes are quieter than conventional brakes. In fact the guideways and the leaf springs, generally made from a stainless steel sheet, are intended to reduce the vibrations existing between the brake pad and the carrier by allowing a certain freedom of movement of the brake pad in relation to the carrier, and thus allowing a reduction in the coefficient of friction between the pad and the carrier by improved surface states. The brake pads are generally mounted sliding freely in the associated guideways. Control of the coefficient of friction and the forces applied by the leaf spring to the pad also allows control of the sliding forces and guidance of the pad, and hence the characteristics of the disk brake in terms of residual torque and absorption can be managed.
The brake pads are therefore stressed against the disk by an application element of the caliper, and repelled in the opposite direction towards their rest position by the friction of the disk when the application element has returned to its rest position. An example of these guideways amongst others is disclosed in document WO 2001/031223 A1.
However, sometimes the pad rubbing against the disk begins to vibrate, creating an unpleasant noise, despite the spring effect of the guideway.
The object of the present invention is to propose an economic guideway which is able to offer an increased damping capacity in order to reduce the noise from vibration while guaranteeing good sliding of the pad, and a disk brake equipped with such guideways.
To this end, the invention concerns a guideway of the type defined by a body of substantially rectangular, U-shaped cross section in order to move in a housing and continuing into a front support surface which comes to rest against the front surface of a stud and carries two tabs to form lateral stops arising from either side of the stud, and a damper spring formed by a hairpin leg which returns to the front to rest elastically against the side of a pad above a lug, and by an inner front support surface which comes to rest against the inner surface of the arm and receives a face of the pad below the lug, the body having an outer radial surface which comes to rest against an upper face of the housing, followed by a base which comes to rest against the base of the housing, and an inner radial surface equipped with a locking tab to rest and hook against a lower surface of the housing.
The guide element according to the invention is perfectly fixed to the arm of the carrier both by its support on the stud and by its hooking by the locking tab in the housing of the arm. The U-shape of the body of the guide element offers a good guidance contact for the auxiliary or radial spring fitted to each lug of the pad, and not only supports the sensitivity of the braking movement but above all the release of the pad in relation to the disk surface at the end of braking in order to prevent any residual contact, which is the source of friction losses.
To resolve this problem, the object of the invention is a guideway for a disk brake of the type described above comprising elastic damping means on all faces of the guideway liable to be in contact with a carrier, and made from a metal sheet covered with said damping means on just one of its faces, characterized in that the damping face comprises contact zones with the carrier and the guideway, and that said guideway comprises an elastic leg in contact with the pad, and has a bent-over portion such that the damping face lies opposite a support zone on the pad. This bent-over portion of the elastic leg allows the material used as a damping means not to come into contact with the pad, and hence for the coefficient of friction between the pad and the guideway to be substantially constant over all contact zones between the pad and the guideway, the coefficient of friction between the pad and the damping material being generally higher than the coefficient of friction between the pad and the stainless steel sheet.
According to the characteristics of the invention:
The contact zone of the elastic leg of the guideway has a rounded form to improve friction between the pad and said leg.
This rounded form advantageously has a radius of between 0.5 mm and 15 mm, and even more advantageously a radius of between 1 mm and 5 mm.
The elastic damping means are advantageously made from an elastomer material.
The elastic damping means are advantageously made from an elastomer material of a thickness between 0.3 mm and 1 mm.
Another advantageous characteristic is that the guideway is made preferably from a stainless steel sheet.
Another advantageous characteristic is that the metal part of the guideway is preferably made from a stainless steel sheet of thickness between 0.3 mm and 1 mm.
Another advantageous characteristic is that the guideway is fixed to the fixed carrier by elastic fixing means, by the nesting of complementary forms and two tabs located on either side of an elastic blade. These means ensure the positioning and support of the guideway on the carrier.
The object of the invention is also a brake disk of the type described above, equipped with at least one guideway in contact with the carrier, and made from a metal sheet covered by damping means on just one of its faces, characterized in that the damping face of the guideway comprises contact zones with the carrier and the guideway, and that said guideway comprises an elastic leg in contact with the pad and has a bent-over portion such that the damping face lies opposite a support zone on the pad.
Other characteristics and advantages will appear from reading the detailed description below, for understanding of which reference is made to the attached drawings in which:
For economic reasons, these guideways are made by cutting and folding from a metal sheet covered by a damping means on just one face, forming two layers. The face carrying the damping means generally has a higher coefficient of friction than the face of the metal which is not covered. It is therefore important that all parts of the guideway in contact with the pad have the same coefficient of friction, so as to avoid creating a bias of the pad during its sliding in the release phase.
More particularly, the object of the invention is a guideway for a disk brake 1 of a motor vehicle, which comprises at least one brake pad 5 which is mounted sliding in at least one guideway 7 in relation to a brake disk 8 along an axially oriented slide axis, between a front braking position in which a friction face 6 of the brake pad 5 is able to be applied to a face of the disk 8, and a rear rest position in which the friction face of the brake disk is remote from the face of the disk. A caliper 2 comprises at least one application element 4 of the brake pad 5, which is able to stress the brake pad axially towards its braking position, and is of the type in which the guideway 7 is fixed to a fixed carrier 3.
This guideway of the type defined has a body of substantially rectangular, U-shaped cross section in order to move in the housing and continuing into a front support surface which comes to rest against a front surface of a stud 24 of the carrier 3, and carries two tabs 14 and 14b to form lateral stops arising from either side of the stud, and a damper spring 10 formed by a hairpin leg which returns to the front to rest elastically against the side of the pad 5 above the lug 9, and by an inner front support surface which comes to rest against the inner surface of the arm and receives a face of the pad below the lug, the body having an outer radial surface which comes to rest against an upper surface of the housing, followed by a base 16 which comes to rest against a base of the housing, and an inner radial surface equipped with a locking tab 15 to rest and hook against a lower surface of the housing, comprising the elastically deformable leg 10 and a bent-over portion serving as a guide face 11, comprising a contact zone with the brake pad 5 and exerting a constant elastic force F, and comprising elastic damping means 13 on all faces of the guideway liable to be in contact with the carrier 3, and made from a metal sheet covered by said damping means on just one of its faces, characterized in that the damping face comprises contact zones with the carrier 3 and the guideway 7, and that said guideway comprises the elastic leg 10 in contact with the pad, and has a bent-over portion 11 such that the face comprising the damping means 13 lies opposite a support zone on the pad 5.
The bent-over portion 11 forming the contact zone of the elastic leg 10 of the guideway 7 has a rounded form to improve the friction between the pad and said leg, and this rounded form 11 advantageously has a radius of curvature of between 0.5 mm and 15 mm, and further advantageously a radius of between 1 mm and 5 mm.
Effectively, this bent-over portion of the elastic leg allows the material used as a damping means not to come into contact with the pad, and hence the coefficient of friction between the pad and the guideway to be substantially constant over all contact zones between the pad and the guideway.
The damping face comprises elastic damping means which are advantageously made from elastomer material.
According to another embodiment, the guideway 20 is made from metal sheet which is coated, cut and folded, wherein the layers 22, 21, 23 may be made from different materials, for example polytetrafluoro-ethylene/metal/rubber. This allows adjustment of the damping capacities and friction of the guideway as a function of the application on vehicles. Effectively these guideways have an effect on the sliding forces of the pad, and because the coefficient of friction between the guideway and the pad can be increased or reduced, the residual torque of the disk brake can be reduced.
The contact zone 11 of the elastic leg 10 of the guideway 7 has a rounded form in order to improve the friction between the pad and said leg.
This rounded form advantageously has a radius of curvature of between 0.5 mm and 15 mm, and further advantageously a radius of between 1 mm and 5 mm.
Another advantageous characteristic is that the guideway 7 is fixed to the fixed carrier 3 by elastic fixing means 15, by nesting of complementary forms and two tabs 14 and 14b situated on either side of an elastic blade 10.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1103908 | Dec 2011 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2012/075592 | 12/14/2012 | WO | 00 | 5/9/2014 |
