Patent Application
20090101456
The present invention is predicated upon systems and methods for improving brake calipers and rotors and more specifically reduction of vibration and noise generated thereby during operation.
Current disc brake systems commonly include a caliper that temporarily clamps opposing friction pads to an annular braking surface on a rotor thereby applying a braking force. As a result of many brake component structures, cyclic contact occurs between the friction pads and the disc portion of the rotor in a “brake-off” position; that is, the position when the operator is not actuating the brake system such as by depressing a brake pedal. In turn, localized rotor wear causes disc thickness variation (DTV). During subsequent braking, this DTV results in cyclic brake torque variation (BTV), which can cause noise and pulsation in the suspension, steering and brake actuation systems. Such pulsation and noise can be a major cause of customer dissatisfaction resulting in warranty costs and loss of future sales. It would be particularly attractive to reduce the undesirable consequences of DTV. U.S. Pat. No. 6,234,284, which is herein incorporated by reference for all purposes, shows one effort to address DTV.
The present invention meets the above needs by providing an improved brake system, particularly one adapted for inclusion in an automotive vehicle corner module, and methods of manufacturing the same. By way of summary, the present invention is directed to a brake system, and also to its use in a corner module, e.g., one including a knuckle, a hub and bearing, a caliper assembly including a caliper that carries at least two opposing and spread apart friction pads, and a rotor. In general, the present invention contemplates the employment in a brake system of a rotor having a rotational axis and including a hat portion and a disc portion, with the disc portion disposed between the friction pads. At least one of the friction pads and/or the rotor includes a main body portion having a first stiffness and at least one sacrificial portion having a second stiffness that is less stiff than the first stiffness of the main body portion. In a brake-off position, a first running clearance between the friction pads and the rotor of the sacrificial portion will be lower than a second running clearance between the friction pads and the rotor of the main body portion. In a brake-on position, the axial deflection of the sacrificial portion exceeds the axial deflection of the main body portion.
In another aspect, the present invention contemplates a brake pad for a vehicle that includes a friction pad. The friction pad includes a main body portion having a top surface and a first stiffness, and at least one sacrificial portion having a top surface and a second stiffness that is less stiff than the first stiffness of the main body portion. In a brake-on position, the deflection of the at least one sacrificial portion will be greater than the deflection of the main body portion upon at least a portion of the brake pad engaging at least a portion of a rotor having a rotor axis. In a brake-off position, a first running clearance between the at least one sacrificial portion and the rotor will be lower than a second running clearance between the main body portion and the rotor, and wherein over time, during brake operation, the at least one sacrificial portion will wear at a rate such as to generally maintain a differential height between the top surface of the sacrificial portion and the top surface of the main body portion. The main body portion includes a top surface and a bottom surface that are spaced apart to define a first thickness that is generally parallel to the rotor axis and the at least one sacrificial portion includes a top surface and a bottom surface that are spaced apart to define a second thickness that is generally parallel to the rotor axis and is greater than the first thickness.
In another aspect, the present invention provides a method for manufacturing a brake pad comprising the steps of applying a mass of friction pad material to a pressure plate and separating at least a portion of the friction pad, the pressure plate, or both, thereby at least partially separating a main body portion having a first stiffness from at least one spring blade portion having a second stiffness that is less stiff than the first stiffness.
In yet another aspect, any of the aspects of the present invention may be further characterized by one or any combination of the following features: for the friction pad including the at least one sacrificial portion, the friction pad is supported on a pressure plate that includes a main body portion and at least one spring blade portion that supports the at least one sacrificial portion; the main body portion of the pressure plate, the friction pad, or both includes a top surface and a bottom surface that are spaced apart to define a first thickness, and the at least one spring blade portion, the at least one sacrificial portion, or both includes a top surface and a bottom surface that are spaced apart to define a second thickness such that the top surfaces are at a different height relative to one another in the brake-off position; the second thickness of the at least one sacrificial portion is greater than the first thickness of the main body portion of the friction pad so that the top surface of the at least one sacrificial portion engages the rotor prior to the top surface of the main body portion of the friction pad; the second thickness of the pressure plate is less than the first thickness of the pressure plate, and wherein in the brake-off position, the top surface of the at least one spring blade portion of the pressures plate is generally co-planar relative to the top surface of the main body portion of the pressure plate; the first stiffness and the second stiffness are in the direction generally parallel with the rotational axis of the rotor; the spring blade portion is cantilevered and is joined to the main body portion of the pressure plate via a transition portion about which the spring blade portion deflects when the at least one sacrificial portion engages the rotor; the main body portion and at least one of the at least one sacrificial portion or the at least one spring blade portion form at least one gap therebetween; the main body portion of the friction pad and the at least one sacrificial portion of the friction pad are separate from one another; the ratio of the first stiffness and second stiffness is from about 200,000:1 to about 1,000:1, the at least one sacrificial portion contributes on the order of about 5 to about 15% of the total braking pad surface width, or a combination of both; the caliper further includes a piston portion and a finger portion spaced apart and generally opposing one another, the piston portion or the finger portion located generally adjacent to the bottom surface of the main body portion of the pressure plate and substantially free of contact with the at least one spring blade portion; the main body portion and the at least one sacrificial portion are located within the disc portion of the rotor, the main body portion and the at least one sacrificial portion include a top surface and a bottom surface, and an outer surface and an inner surface and wherein at least one of the top surface or the bottom surface of the main body portion, the at least one sacrificial portion, or both is configured to engage at least one of the at least two friction pads; the main body portion and the sacrificial portion are spaced apart with respect to one another so that the outer surface of one is located proximate to the inner surface of the other and wherein at least one of the top surface or the bottom surface of the sacrificial portion is axially deflected with respect to the top surface or the bottom surface of the main body portion; the at least one sacrificial portion is supported by a plurality of fastening members and wherein a portion of the axial deflection occurs between at least two of the plurality of fastening members; for the friction pad including the at least one sacrificial portion, the friction pad is supported on a pressure plate that includes a main body portion having a first thickness and at least one spring blade portion that supports the at least one sacrificial portion, and wherein the spring blade portion of the pressure plate is coined to thin the spring blade portion and thereby define a second thickness for the spring blade portion that is less than the first thickness of the main body portion of the pressure plate so that a bottom surface of the at least one spring blade portion is axially displaced with respect to a bottom surface of the main body portion; further including the step of removing material from the main body portion of the friction pad so as to defines a first thickness that is less than the at least one sacrificial portion of the friction pad having a second thickness; the step of removing material from the friction pad is achieved by engaging the surface of the friction pad with a material removal tool, during which, because of the deflection of the spring blade portion, the resulting amount of material removed from the at least one sacrificial portion is less than in the main body portion of the friction pad so that a height differential results between the upper surface of the friction pad in the main body portion and the at least one sacrificial portion; further including the step of coining the spring blade portion to thin the spring blade portion and thereby define a second thickness for the spring blade portion that is less than the first thickness of the main body portion so that the bottom surface of the at least one spring blade portion is axially displaced with respect to the bottom surface of the main body portion and further to reduce a portion of the gap between the main body portion and the at least one spring blade portion; or any combination thereof.
In a broad sense, the present invention is directed to an improved brake system for overcoming problems associated with disc thickness variation (DTV). In one aspect, the present invention is directed to an improved corner module for an automotive vehicle incorporating the improved brake system. Though fewer or more components may be included in a corner module, it is generally contemplated that a corner module 10 herein will include a steering knuckle 12, a hub 14 and bearing 16, a caliper assembly 18, and a rotor 20. The caliper assembly typically will include at least two opposing and spaced apart brake pads 21, each including a friction pad 22, arranged for clamping engagement with the rotor. The rotor has a rotational axis (shown as RA in
In a brake-off position, a first running clearance between the friction pad and the rotor of the sacrificial portion will be lower than a second running clearance between the friction pad and the rotor of the main body portion. In a brake-on position, (i.e., a position in which the brakes are actuated by a vehicle operator), the deflection of the sacrificial portion exceeds the deflection of the main body portion; the deflection being in a direction generally parallel with the rotational axis of the rotor, and thus is referred to as “axial deflection.”
The caliper assembly typically includes at least two opposing and spaced apart friction pads 22. At least one friction pad 22 includes a main body portion 24 having a first stiffness and at least one sacrificial portion 26 having a second stiffness that is less stiff than the first stiffness of the main body portion. Such friction pad is typically supported by a pressure plate 28 that includes a main body portion 30 and at least one spring blade portion 32, which supports the sacrificial portion. It is contemplated that the spring blade portion may be part of the pressure plate or an additional component.
The spring blade portion may be cantilevered relative to the main body portion. For instance, the spring blade portion 32 may be joined to the main body portion 30 via a transition region 34 about which the spring blade portion deflects when the sacrificial portion engages the rotor. The pressure plate includes a top surface 36 and a bottom surface 38 and the friction member includes a top surface 40 and a bottom surface 42. The bottom surface 42 of the main body portion 24 of the friction pad may be mounted to the top surface 36 of the main body portion 30 of the pressure plate and the bottom surface 42 of the sacrificial portion 26 may be mounted to the top surface 36 of the spring blade portion 32. The top surface 40 of the friction pad is configured for engaging the rotor.
The caliper assembly further includes a piston portion 72 and a finger portion 74 spaced apart and generally opposing one another. Either or both of the piston portion and the finger portion are located generally adjacent to the bottom surface 38 of the main body portion 30 of the pressure plate.
As shown in
In another embodiment as shown in
For the above, instead of or in addition to varying thicknesses, the spring blade portion 32 may be deformed (e.g., upwardly) so the top surface 54 of the spring blade portion is elevated relative to the top surface 50 of the main body portion.
In a brake-on position, the sacrificial portion will generally be the same height as the top surface of the main body portion of the friction pad. In a brake-off position, the top surface of the sacrificial portion will be elevated relative to the top surface of the main body portion of the friction pad. As such, in a brake-off position, the top surface of the sacrificial portion will be elevated (non-coplanar) with respect to the top surface of the main body portion. As shown in
The caliper assembly may further include a gap 70 separating the main body portion from the spring blade portion. These gaps may extend from the leading end, the trailing end, or both as shown in
Referring to
The top and the bottom surfaces of the main body portion and the first sacrificial portion are configured to engage the top surfaces of the friction pads of the caliper assembly. The first sacrificial portion may be further configured to axially deflect the top surface, the bottom surface, or both with respect to the top surface, the bottom surface, or both of the main body portion. As such, in the brake-on position, the top surface of the first sacrificial portion engages a first portion of the friction pad prior to the top surface of the main body portion engaging a second portion of the friction pad. The first sacrificial portion may be supported by a plurality of attachment members 106 such as posts, fasteners, or otherwise. It optionally may be spring biased for urging the sacrificial portion to a height higher than the top surface 88 of the main body portion.
As a result of the deflection during the brake-on position and the engagement of the brake pad with the first sacrificial portion of the rotor face, the surfaces deflected under load will stand proud of the main body portion in the unloaded or brake-off position. The magnitude of the deflection and hence the protrusion of the deflected surface of the first sacrificial portion above the main body portion can be designed to ensure that during brakes-off position only the first sacrificial portion contacts the inboard friction pad and hence only the first sacrificial portion of the rotor is subject to DTV.
The annular sacrificial portion of the rotor may be inside the main body portion so that the effective radius of the sacrificial portion, and hence the BTV, are minimized (
It is contemplated that over time, the sacrificial portion of the friction pad, the rotor, or both will wear at a rate such as to generally maintain a differential height between the sacrificial portion and the main body portion (e.g., top surface of sacrificial portion with respect to the top surface of the main body portion. It is further appreciated that the sacrificial portion may be designed to perform the function of a “brake pad wear indicator” that is typically achieved using an additional stamped part.
As can be appreciated the increased deflection of the sacrificial portion components during braking results in reduced clearance between the friction pad and the rotor components when in a brake-off position. This helps ensure that even as the friction pads and the rotor components wear, the sacrificial portion will be the first to contact the rotor during the brake-off position ensuring that the sacrificial portion alone will be subject to cyclic contact and resulting DTV. Further, because of the role played by the sacrificial portion, it is believed possible to reduce BTV to negligible levels, which help minimize the cause of pulsations detectable by the driver.
In the brake-on position, friction pads, rotor, or each may include several portions that provide the same or different amounts of braking work across the surface of the friction pad that when taken together define a total braking surface width with respect to that specific friction pad or rotor. As such, it is appreciated that the sacrificial portion of the friction pad and/or the rotor contributes on the order of about 3 to about 25%, more specifically about 5 to about 15%, (e.g., about 10%) of the total braking surface width. Furthermore, it is appreciated that the main body portion of the friction pad, the rotor, or both provide about 85 to about 95% of the total braking surface width.
The present invention, also contemplates methods of manufacturing. For example, one method envisions applying a mass of friction pad to a pressure plate and then separating at least a portion of the friction pad, the pressure plate or both, to define a fully or partially separated main body portion having a first stiffness and at least one sacrificial portion having a second stiffness that is less stiff than the first stiffness. It is envisioned also that methods will include a friction pad material removal step that includes removing material from the main body portion of the friction pad to define a thickness or height differential between the friction pad of the main body portion and that of the sacrificial portion. More specifically, removing material (e.g. grinding) from the friction pad may be done by engaging the surface of the friction pad with a material removal tool, during which, because of the deflection of the spring blade portion, the resulting amount of material removed from the friction pad is less than in the main body portion. A height differential thus results between the upper surface of the friction pad in the main body portion and the spring blade portion. The separating step may occur prior to the step of applying the mass of friction pad to the pressure plate or after.
The method also contemplates the possibility of a separate step of attaching (e.g., welding, fastening, bonding, or any combination thereof spring blade portion to the main body portion of the pressure plate.
In one particular respect, the pressure plate herein may be made by a method that includes forming a shaped pressure plate, in which a piece of metal is stamped. The step of making the pressure plate may further comprise a step of coining a portion of the spring blade portion to define a first thickness that is less than the second thickness of the main body portion.
For example, for making a brake pad as shown in
It is appreciated that the removing step may occur prior to or after applying the friction pad to the pressure plate. For example, one approach includes applying the friction pad material to the pressure plate and then slitting it to separate into portions for each. Preferably, the removing step occurs after the friction pad has been mounted to the pressure plate. During this operation, the spring blade portion, including the sacrificial portion deflects so that after grinding the main body portion of the friction pad, the top surface of the sacrificial portion is higher than the top surface of the main body portion. More specifically, after the removing step, the top surface of the main body portion of the friction pad will have a first thickness that is less than the second thickness of the sacrificial portion. An alternative method of achieving the spring blade function may be to rivet an additional steel stamping to the pressure plate and then mount the friction pad.
It will be further appreciated that functions or structures of a plurality of components or steps may be combined into a single component or step, or the functions or structures of one-step or component may be split among plural steps or components. The present invention contemplates all of these combinations. Unless stated otherwise, dimensions and geometries of the various structures depicted herein are not intended to be restrictive of the invention, and other dimensions or geometries are possible. In addition, while a feature of the present invention may have been described in the context of only one of the illustrated embodiments, such feature may be combined with one or more other features of other embodiments, for any given application. It will also be appreciated from the above that the fabrication of the unique structures herein and the operation thereof also constitute methods in accordance with the present invention. The present invention also encompasses intermediate and end products resulting from the practice of the methods herein. The use of “comprising” or “including” also contemplates embodiments that “consist essentially of” or “consist of” the recited feature.
The explanations and illustrations presented herein are intended to acquaint others skilled in the art with the invention, its principles, and its practical application. Those skilled in the art may adapt and apply the invention in its numerous forms, as may be best suited to the requirements of a particular use. Accordingly, the specific embodiments of the present invention as set forth are not intended as being exhaustive or limiting of the invention. The scope of the invention should, therefore, be determined not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. The disclosures of all articles and references, including patent applications and publications, are incorporated by reference for all purposes.
The present invention claims the benefit of the priority of the filing date of U.S. Provisional Application Ser. No. 60/980,884 filed Oct. 18, 2007, which is herein incorporated by reference for all purpose.
| Number | Date | Country | |
|---|---|---|---|
| 60980884 | Oct 2007 | US |
