Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Reexamination Certificate
1998-11-30
2001-01-23
Kamen, Noah P. (Department: 3746)
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
C092S071000
Reexamination Certificate
active
06176684
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to variable displacement hydraulic piston units such as pumps, motors, and the like, and more particularly, to a hydraulic piston unit having a displacement control including an electric motor, such as a stepper motor and cam arrangement operable for changing swash plate angle, and a timing control operable using a stepper motor for rotating the swash plate.
BACKGROUND ART
Currently, variable displacement hydraulic piston units, such as pumps, motors and the like, typically utilize a hydraulic or electro-hydraulic system for changing swash plate angle for varying displacement. It is also known to vary timing by changing the angular position of the port plate of a unit using various means, including a stepper motor and gear arrangement.
However, the typical known hydraulic valves utilized for controlling displacement are generally complex and expensive. It is also desirable to have an alternative to changing port plate position for varying timing. Still further, with the trend toward increased electronic control of hydraulic systems, it is desirable to integrate hydraulic piston unit displacement and timing in an electronic format with other electronically controlled functions.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the present invention, a variable displacement hydraulic piston unit with variable timing is disclosed. The piston unit includes a port plate including a flat surface having an axis therethrough and an intake port and an exhaust port at angularly spaced locations around the axis. The piston unit includes a cylinder barrel and structure supporting the cylinder barrel for rotation about the axis relative to the port plate, the cylinder barrel having a first axial end portion in abutment with the surface of the port plate, and an opposite second axial end portion. A plurality of axial piston bores extends through the cylinder barrel between the axial end portions in circumferentially spaced relation around the axis, the bores being positioned to sequentially open into the intake port and the exhaust port during the rotation of the cylinder barrel. The unit includes a plurality of pistons positioned for axial displacement in the respective piston bores in timed relation to the intake port and the exhaust port during the rotation of the cylinder barrel, and a swash plate and structure supporting the swash plate adjacent the second axial end portion of the cylinder barrel for sliding contact with the pistons during the rotation of the cylinder barrel. The structure supporting the swash plate is adapted for allowing tilting of the swash plate relative to the cylinder barrel about a tilt axis orientated crosswise to the first named axis for varying the displacement of the pistons, and is adapted for allowing rotation of the swash plate about the first named axis for varying the timed relation of the displacement of the pistons to the intake port and the exhaust port.
According to a preferred aspect of the invention, the swash plate and the structure supporting the swash plate are jointly rotatable about the first named axis for varying the timed relation of the displacement of the pistons to the intake port and the exhaust port using an electric motor, such as a stepper motor and a drive.
In another aspect of the invention, the structure supporting the swash plate includes an electric motor, such as a stepper motor operable for controllably tilting the swash plate about the tilt axis for varying the displacement of the pistons.
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Burrows J. W.
Caterpillar Inc.
Gimie Mahmoud M
Haverstock Garrett & Roberts
Kamen Noah P.
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