Patent Application
20060219495
1. Field of the Invention
The present invention relates to the field of inertia brakes and to an inertia brake assembly suitable for use with friction clutches in heavy duty vehicles.
2. Description of the Related Art
An inertia brake is a device used to rapidly slow the rotational speed of a transmission input shaft to facilitate the shifting of gears in the transmission. Without an inertia brake, the time required to shift a transmission would be significantly increased, thereby complicating operation of the transmission in several driving modes.
An inertia brake may include a disc-shaped rotor that is splined to a transmission input shaft and is activated by a master clutch release mechanism when the master clutch is disengaged. In one design, the rotor is positioned between two coil spring-separated plates that include a friction material for engaging the rotor. The release mechanism moves between engaged (near the clutch) and disengaged (nearer the transmission) positions, causing the master clutch to selectively connect and disconnect the transmission input shaft from the engine. Near the end of its disengagement stroke, the release mechanism compresses the inertia brake and forces the plates to contact the rotor. When so moved, rotation of the inertia brake rotor, and consequently the transmission input shaft, is slowed or stopped by virtue of the friction material on the plates contacting and imparting drag on the rotor.
Inertia brakes, while adequate for slowing rotation of a transmission input shaft, may include multiple independent parts that increase the complexity of their installation into a vehicle. Furthermore, the coil springs that separate the plates utilize guide studs that may bind and/or wear over time. Moreover, the use of guide studs may require that the metal plates be heat-treated to improve their durability.
A brake assembly for slowing rotation of a shaft is provided. In an embodiment, the brake assembly includes a first reaction member, a second reaction member attached to and moveably separated from the first reaction member by a resilient strap, and a rotor rotatably driven by and slideably disposed on the shaft. The rotor is retained between the first and second reaction members by the resilient strap. The strap separates the first and second reaction members to allow the rotor to rotate freely and is resiliently compressible to allow the first and second reaction members to selectively and frictionally engage the rotor to slow its rotation. An inertia brake assembly for a transmission input shaft and a vehicle powertrain system that includes a brake assembly according to the present invention are also provided.
The features and inventive aspects of the present invention will become more apparent upon reading the following detailed description, claims, and drawings, of which the following is a brief description:
A schematic illustration of an exemplary vehicle powertrain system is shown in
In the exemplary clutch assembly, a single-disc (shown) or multi-disc friction clutch 14 drivingly connects an engine 16 with a transmission assembly 18 and rotates about an axis 20. A clutch housing 22, sometimes referred to as a bell housing, connects an engine block of engine 16 with a housing of transmission assembly 18. A flywheel 24 is rotatably fixed to a crankshaft 26 of engine 16. A driven disc 28, centered with respect to axis 20, has a splined hub portion 29 that slideably engages a splined input shaft 30 of transmission 18. Driven disc 28 is at least partially sandwiched between flywheel 24 and a pressure plate 34 and includes friction elements 32 that frictionally contact flywheel 24 and pressure plate 34 when clutch 14 is engaged.
In the illustrated clutch assembly, a cover 36 is disposed over pressure plate 34 and is fixed to flywheel 24. A plurality of straps (not shown) circumferentially extend between pressure plate 34 and cover 36. The straps rotatably fix pressure plate 34 to cover 36 while allowing axial displacement of pressure plate 34 relative to cover 36. The straps are adapted to serve as springs, which can be used to bias pressure plate 34 away from flywheel 24.
A diaphragm spring 38 is axially disposed between cover 36 and pressure plate 34. An annular portion 40 of diaphragm spring 38 biases pressure plate 34 toward flywheel 24, clamping driven disc 28 between flywheel 24 and pressure plate 34 to rotatably connect or lock input shaft 30 with flywheel 24 when clutch 10 is in an engaged position. Diaphragm spring 38 has a plurality of radially inwardly extending fingers 42, the inner tips of which are engaged by the axially displaceable release member 12. A pivot ring 44, or other pivot feature such as a bead formed in the cover, is axially disposed between an outer diameter of annular portion 40 and cover 36 to facilitate pivoting or flexing of annular portion 40 relative to cover 36.
Clutch 14 is selectively released or disengaged by axially displacing release member 12 along axis 20 in a direction away from flywheel 24 against the force of diaphragm spring 38. Such displacement is achieved by a vehicle operator depressing the pedal, for example, with the motion of the pedal being transferred via linkage 11 to displace release member 12. As the radially inner tips of fingers 42 are axially displaced away from flywheel 24, fingers 42 bow, causing annular portion 40 to deflect, thereby relieving the clamping load against pressure plate 34, and permitting rotation of input shaft 30 relative to flywheel 24. Annular portion 40 engages a fulcrum 48 of pressure plate 34 proximate to an inner diameter of annular portion 40.
In the illustrated embodiment, clutch housing 22 provides a grounded surface against which an inertia brake 50 may be compressed by the axial movement of release member 12. Release member 12 is moved axially to press against inertia brake 50 when clutch 14 is disengaged and it is desired to slow rotation of transmission input shaft 30 to facilitate a gear ratio change in transmission 18. Alternatively, a portion of transmission 18, such as the transmission housing, may provide the grounded surface against which inertia brake 50 is compressed when clutch 14 is disengaged.
Referring to
In an embodiment, second reaction member 54 is attached to and moveably separated from first reaction member 52 by a plurality of resilient straps 56. Straps 56 may be positioned about a circumferential edge 62 of first and second reaction members 52, 54 to retain rotor 58 therebetween. Straps 56 may non-rotatably fix first reaction member 52 to second reaction member 54 while allowing axial displacement of second reaction member 54 relative to first reaction member 52. In the embodiment shown in
In an embodiment, first and second reaction members 52, 54 are generally annular plates that include a hole 68 for passage of input shaft 30. To secure brake assembly 50 to clutch housing 22, first reaction member 52 may include at least one mounting bracket 70. Mounting bracket 70 includes a hole or aperture 72 that aligns with a corresponding hole or aperture in clutch housing 22 (or a transmission housing as noted above) to cooperatively receive a fastener 74 (see, e.g.,
To facilitate a relatively rapid reduction in speed of rotor 58, a rotor-facing side of first and second reaction members 52, 54 may include a friction material (not shown). The friction material may be adapted to cover substantially all of or only a portion of each reaction member 52, 54. Any suitable friction material may be provided on reaction members 52 and 54, including those materials used in conventional clutch brakes. Since reaction members 52, 54 may be made from a low carbon steel, such as AISI 1008 and AISI 1010 steel, the friction material may be readily bonded to reaction members 52, 54 using known bonding processes. Furthermore, low carbon steel does not require heat-treatment and the manufacturing expense associated therewith.
In an embodiment, rotor 58 is a generally smooth metal disc, which includes an internal spline 82 that secures rotor 58 for rotation with input shaft 30. When so configured, rotor 58 is axially slideable in relation to both input shaft 30 and first and second reaction members 52, 54. Alternatively, rotor 58 may be configured as a torque-limiting rotor.
At least one hole 84 may be provided in rotor 58 to reduce its weight and/or facilitate cooling when frictionally engaged by first and second reaction members 52, 54. If desired, tabs or other features (not shown) may be formed in first and second reaction members 52, 54 to constrain rotor 58 on input shaft 30 and/or more precisely position rotor 58 within brake assembly 50 for installation in clutch housing 22.
Operation of brake assembly 20 will now be described with reference to
When it is desired to rapidly slow rotation of input shaft 30 to facilitate a gear ratio change in transmission 18, clutch 14 is disengaged and release member 12 is moved axial into contact with second reaction member 54. Release member 12 compresses brake assembly 50 against clutch housing 22, causing each of first and second reaction plates 52, 54 to frictionally contact rotor 58 (see, e.g.,
Although brake assembly 50 of the present invention is particularly suited for use as an inertia brake for slowing rotation of a transmission input shaft disposed between a clutch and a transmission of a motor vehicle, brake assembly 50 may be used in other applications requiring the rotational slowing of a shaft.
The present invention has been shown and described with reference to the foregoing embodiments, which are merely illustrative of the best modes for carrying out the invention. It should be understood by those skilled in the art that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention without departing from the spirit and scope of the invention as defined in the following claims. It is intended that the following claims define the scope of the invention and that the method and apparatus within the scope of these claims and their equivalents be covered thereby. This description of the invention should be understood to include all novel and non-obvious combinations of elements described herein, and claims may be presented in this or a later application to any novel and non-obvious combination of these elements. Moreover, the foregoing embodiments are illustrative, and no single feature or element is essential to all possible combinations that may be claimed in this or a later application.
