192 clutches and power-stop control – Clutches – Operators
Reexamination Certificate
2000-05-26
2001-12-25
Marmor, Charles A (Department: 3681)
192 clutches and power-stop control
Clutches
Operators
C192S035000
Reexamination Certificate
active
06332522
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
This invention relates to a hydraulic coupling for use with a vehicle drivetrain within a housing containing hydraulic fluid to rotatively couple a pair of rotary members about a rotational axis; for example, a speed sensitive limited slip differential.
b) Background of Related Art
Many types of hydraulic devices have utilized internal gear sets, which are often called gerotors or rotors. Such devices can be used as pumps where shaft work is converted to hydraulic work and as motors where hydraulic work is converted to shaft work. In an internal gear pump or motor, an inner gear having outwardly directed teeth cooperates with an external gear having inwardly directed teeth so that fluid chambers therebetween increase and decrease in volume as the inner and outer gears rotate in a housing. By connecting the inlet and outlet of the device to the proper location along the sides of the gear set, the variable displacement chambers receive and discharge hydraulic fluid so that the device can function as a pump or motor. A shaft or other mechanical device can be connected to either the inner or outer gear depending upon the type of device.
Many of the internal gear pumps and motors of the prior art utilize a housing having a fixed inlet and outlet valve port. In other gerotor pumps and motors, a rotary valve plate or disc is used.
The gerotor pump has previously been utilized to couple rotary members of a vehicle drivetrain, particularly a limited slip differential mechanism. However, prior art gerotor pump devices suffer from inadequate or inefficient control of the torque curve and torque transfer characteristic of the pump device. Conventional check valves and other control valve systems suffer from excessive variability in torque distribution, they are difficult to handle and assemble and they require expensive machining in the differential case. Additionally, the conventional valve systems do not adequately control the torque transmission characteristics for the pump.
The need therefore exists for an improved and efficient control valve system that provides an effective hydraulic flow path.
SUMMARY OF THE INVENTION
The present invention provides an improved control valve for use in controlling rotative coupling of a pair of rotary members of a vehicle drivetrain.
In carrying out the above object, the control valve of this invention includes a valve system through which pressurized hydraulic fluid selectively flows to control the coupling of the pair of rotary members. The instant invention provides a grooved pressure port stack which creates a hydraulic flow path for a gerotor pump and maintains pressure equalization about the gerotor pump. The grooved pressure port stack comprises at least one relatively thin circular plate that provides a pocket to equalize pressure in different areas of the gerotor pump and controls the torque curve of the clutch device.
For this invention, a pressure/torque controlling groove is located in the port plate for a variety of reasons including: the control groove fits well into the stacked valve which is particularly suited to a zero end clearance pump such as described below, the control groove creates an efficient use of space, and the dimensions and cross sectional area of the groove can be changed easily to produce different pressure/torque curves.
In addition, supercharging occurs when the port plate groove connects the pressure and intake apertures (or halves) of the eccentric pump. Supercharging increases the threshold of speed at which harmful cavitation can occur and also reduces the amount of oil that must be drawn into a positive displacement pump.
In the preferred embodiment of this invention, the groove is designed into the port or wear plate that seals one face of a zero end clearance eccentric hydraulic pump. The groove acts as an orifice for oil flow, and the relationship of the pressure and flow through the orifice creates a pressure curve. The pressure drives a clutch pack to create a torque curve that is related to vehicle mobility. The groove can connect the pressure port to the sump of the axle or the intake port of the pump for added benefit of supercharging effects.
The objects, features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.
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patent: 6076646 (2000-06-01), Burns
patent: 6112874 (2000-09-01), Kopp et al.
patent: 6238315 (2001-05-01), Morse et al.
Morse David Marshal
Yoshioka Jun
Dana Corporation
Liniak Berenato Longacre & White
Marmor Charles A
Rodriguez Saul
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