Patent Application
20130341135
This application claims benefit of Canadian patent application number 2,781,540, filed Jun. 26, 2012, which is herein incorporated by reference.
1. Field of the Invention
The invention relates to backing plates for use in disc brake pads.
2. Description of the Related Art
Modern vehicle brake systems allow for slowing or stopping movement of the vehicle in a controlled manner. A typical automobile or light truck brake system includes a disc brake assembly for each of the front wheels and either a drum brake assembly or a disc brake assembly for each of the rear wheels. The brake assemblies are actuated by hydraulic or pneumatic pressure generated when an operator of the vehicle depresses a brake pedal. The structures of these drum brake assemblies and disc brake assemblies, and their actuators, are well known in the art.
A typical disc brake assembly includes a rotor which is secured to the wheel of the vehicle for rotation therewith. The rotor has a pair of opposed friction plates which are selectively engaged by portions of a caliper assembly. The caliper assembly is slidably supported by pins secured to an anchor plate. This anchor plate is in turn secured to a non-rotatable component of the vehicle, such as the vehicle frame. A pair of brake pads (shoes) are disposed in the caliper assembly on opposite sides of the rotor. These brake pads are operatively connected to one or more hydraulically actuated pistons for movement between a non-braking position, wherein they are spaced apart from the opposed friction plates of the rotor; and a braking position, wherein they are moved into frictional engagement with the opposed friction plates of the rotor. Depressing the brake pedal causes the piston to urge the brake pads from the non-braking position to the braking position, frictionally engaging the friction plates to the rotor and thereby slowing or stopping the rotation of the associated wheel of the vehicle.
The brake caliper is typically a cast solid piece of iron, steel or aluminum. The casting process leaves rounded interior edges. In order to provide corner clearance with these rounded interior edges, the brake pads, themselves planar and angular, are frequently chamfered on one edge where the mounted pad faces the interior corner of the caliper.
The classic chamfer on the backing plate portion of the brake pad is an angled surface on the leading edge of the plate that substantially mirrors (or at least provides complementary geometry with) the rounded angled surface in the interior corners of the caliper. The chamfer and the corner of the caliper, lacking points of potential unwanted contact, thus have clearance from each other. However, such chamfered edges, while elegant, are not easy to produce, particularly on brake backing plates having a rounded or other irregular shaped leading edge.
Further, although routinely manufactured for backing plates, the chamfered angle is not needed for every shape of caliper. Therefore, an extra costly and time-consuming secondary step is often needlessly included. Chamfering has become an ingrained and expected part of the manufacturing process for backing plates.
It would be desirable to provide a simple alternative to the complex chamfer.
According to an aspect of the invention, a brake plate is provided that has a substantially planar metallic body with a first friction facing surface, a second opposing caliper facing surface, and a pair of relatively long edges and a pair of relatively short edges. At least one of the long edges has a step-chamfer. The step-chamfer is preferably proximate to the second caliper facing surface.
Preferably, the step-chamfer has one step. Preferably, the step is substantially L-shaped. Preferably, the step-chamfer extends along the full length of the plate. In one embodiment, the step-chamfered edge is rounded along its length.
Preferably, the plate is an integrally molded brake plate. Preferably, the plate is formed to receive friction material on the first friction facing surface, and the friction material does not contact the step-chamfer.
Preferably, the plate is sized to fit in a brake caliper, such that the step-chamfered edge will sit adjacent to an inside corner or radius of the caliper. Preferably, the step-chamfer is sized to allow clearance for the plate to sit adjacent to the corner or radius of the caliper.
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
A brake plate is provided that has a substantially planar metallic body. The body has a first friction facing surface and a second caliper facing surface, and a pair of relatively long edges and a pair of relatively short edges. At least one of the long edges has a step-chamfer.
As shown in
The angle chamfer is typically made by grinding or mill-cutting the leading edge. Besides being an expensive and time-consuming secondary operation, the angle chamfer can be particularly difficult to produce where the leading edge C is rounded along its length (i.e. where the top of the brake backing plate is arcuate from edge to edge) or has recessed areas or other edge features (as shown in
By contrast, the step-chamfer shown in
Turning to
The shapes and dimensions of brake backing plates vary widely depending on application. The shape shown in the drawings is merely exemplary of one type for certain models of passenger vehicles, but the invention is not limited to this type/application. A backing plate can be thought of as having two long sides—leading edge 130 and trailing edge 140—and two identical short sides (here, both labelled 150). The short sides may have abutments 160 in certain embodiments. (The abutments are exposed mounting extensions that are not covered by friction material and are used for installation and retention of the brake pad in certain caliper designs.) The leading and trailing edges of the backing plate may also have other recesses (e.g. 220), projections (e.g. 180), and other surface features as may be required for particular applications and/or to provide clearance for other mounting or wear sensor hardware, springs, shims, etc.
The step-chamfer 190 is generally provided at the corner of the plate where leading edge 130 meets surface 110. (NB: This is an area not covered by the friction material.) The step-chamfer is preferably substantially L-shaped, having one step. As shown in
Various dimensions are possible. Preferably, the step-chamfer does not extend into the plate more than half the overall thickness of the plate. Preserving a certain minimum plate thickness may be necessary to protect the integrity of the leading edge 130 of the plate which is an exposed contact area.
Various methods of making the step-chamfer are possible (e.g. forming or stamping methods, grinding, cutting, notching, carving, fine-blanking, etc.) and are beyond the scope of the present disclosure. Due to its simplicity, the step-chamfer may be able to be produced at the same time as other features on the plate, without a separate specialized operation.
Turning to
In
The caliper 250 is typically a cast piece/assembly that may be machined in certain areas to remove surface pebbling, irregularities and rough edges, but generally is not machined to any great extent (or at all) in the interior corner areas 290. In order to maintain overall stiffness of the caliper, thicker sections in the corners 290 of the caliper are believed necessary. Maintaining thickness in these areas is believed to be critical in reducing stress fractures and caliper breakage. As an artefact of the casting process, which is uncorrected by machining, the inside “corners” 290 are actually generally arcuate and thus provide a difficult fit for the plate corners. The step-chamfer 190 on the plate allows clearance for the corner 290 regardless of the corner's specific radius and allows considerable leeway for various casting imperfections.
A shim 240 may be provided on the piston-facing surface 110 of the plate 100 to reduce NVH (noise, vibration and harshness) incident in braking. The shim, if provided, will be smaller than the outside dimensions of the plate, thus not ordinarily contacting the chamfered edge or the inside corner of the caliper. However, it is possible that a tab of the shim may extend into and grab onto the step-chamfer as a further gripping surface. The step-chamfer may be provided with particular recesses or other attachment surfaces specifically for this purpose. The geometry of the step-chamfer is easy to modify for such features.
The foregoing description illustrates only certain preferred embodiments of the invention. The invention is not limited to the foregoing examples. That is, persons skilled in the art will appreciate and understand that modifications and variations are, or will be, possible to utilize and carry out the teachings of the invention described herein. The scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest purposive construction consistent with the description as a whole.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2,781,540 | Jun 2012 | CA | national |
