192 clutches and power-stop control – Clutches – Automatic
Reexamination Certificate
2000-03-29
2001-11-13
Bonck, Rodney H. (Department: 3681)
192 clutches and power-stop control
Clutches
Automatic
C192S085060, C192S1030FA
Reexamination Certificate
active
06315097
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to hydraulic couplings for use in motor vehicle driveline applications. More specifically, the hydraulic coupling includes a hydraulic pump, a transfer clutch coupled between a pair of rotary members, and a fluid distribution system having a valve control system operable for controlling actuation of the transfer clutch.
Hydraulic couplings are used in a variety of motor vehicle driveline applications for limiting slip and transferring drive torque between a pair of rotary members. In all wheel drive applications, hydraulic couplings have been used to automatically control the transfer of drive torque from a driven member to a non-driven member in response to speed differentiation therebetween. In limited slip applications, such as used in association with a differential in an axle assembly, full-time transfer case, or transaxle, hydraulic couplings have been used to limit slip and bias the torque split between two rotary members. Examples of known hydraulic couplings which are adaptable for such driveline applications include viscous couplings, geared traction units, and passively and electronically-controlled hydraulically-actuated friction clutches generally similar to those shown and described in U.S. Pat. Nos. 5,148,900, 5,358,454, 5,649,459, 5,704,863 and 5,779,013.
In response to increased consumer demand for motor vehicles with traction control systems, hydraulic couplings are currently being used in a variety of driveline applications. Such hydraulic couplings rely on hydromechanics and pressure-sensitive valve elements to passively respond to a limited range of vehicle operating conditions. These hydraulic couplings are susceptible to improvements that enhance their performance, such as a more controlled response to a wider range of vehicle operating conditions. With this in mind, a need exists to develop improved hydraulic couplings that advance the art.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a hydraulic coupling for use in motor vehicle driveline applications for rotatively coupling a pair of rotary members to limit speed differentiation and transfer drive torque therebetween.
The hydraulic coupling according to the invention includes a multi-plate clutch assembly operatively connecting a pair of rotary members, and an actuator assembly for actuating the clutch assembly. The actuator assembly includes a hydraulic pump, a piston disposed in a piston chamber, and a fluid control system for controlling the fluid pressure supplied to the piston chamber by the hydraulic pump to control the clutch engagement force exerted by the piston on the clutch assembly. The fluid control system includes a flow control valve operable for limiting the fluid pressure in the piston chamber. The position of the flow control valve is controlled by a flow control module that monitors and responds to vehicle operating conditions, including fluid temperature in the fluid control system, the difference in rotational velocity between the pair of rotary members, piston chamber pressure, and any other vehicle system information. The flow control module modulates the hydraulic pressure in the piston chamber, which, in turn, controls clutch engagement.
As a further feature of the hydraulic coupling, the fluid control system may draw fluid from a secondary pump or a sump, whereby fluid temperature may be monitored by the flow control module.
As another feature of the hydraulic coupling, the fluid control system may be self-contained, thus not reliant on a supply of fluid from a secondary fluid pump or a sump. The self-contained hydraulic coupling is useful for transfer cases, transaxles, or other drivetrain subsystems that do not include a sump or secondary pump.
As another feature of the hydraulic coupling, the fluid control system may include a temperature-sensitive valve element mounted to the piston for movement in response to and as a function of the temperature, and thus viscosity, of the fluid in the piston chamber. In a first extreme position, the temperature-sensitive valve element blocks flow through a port extending through the piston. In a second extreme position, the temperature-sensitive valve element permits flow through the port to vent the piston chamber and release the clutch assembly. In between the extreme valve positions, the valve element variably restricts flow through the port to accommodate variations in fluid viscosity.
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Bonck Rodney H.
Harness Dickey & Pierce
New Venture Gear Inc.
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