Rotary expansible chamber devices – With mechanical sealing – Seal element between vane and cylinder
Reexamination Certificate
2001-02-15
2003-03-25
Vrablik, John J. (Department: 3748)
Rotary expansible chamber devices
With mechanical sealing
Seal element between vane and cylinder
C418S132000, C418S133000, C418S236000, C418S259000, C418S030000, C417S204000
Reexamination Certificate
active
06537047
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This application relates to hydraulic vane pumps and more particularly to reversible pumps which can be used in either the motor or pump mode.
2. Background Art
The key to the design of a highly efficient hydraulic pump/motor is to optimize the following characteristics:
a) low internal leakage by minimizing the size and number of moving parts, controlling clearances by using precision manufacturing processes, and adding auxiliary seals as required;
b) maintaining minimum operating axial clearances by utilizing pressure compensation to balance clamping and separating forces;
c) low mechanical friction resulting from balancing forces where possible, maximizing rotor and vane rigidity, utilizing rolling element bearings where possible to replace sliding elements, and minimizing sliding velocities which is accomplished by minimizing the size of the physical components;
d) low fluid flow restriction; and
e) maximizing fluid power capacity for a given mass and package size—use of light weight materials where possible.
In addition, many applications require full adjustment of fluid displacement, and even over-center adjustment to facilitate the transition from pumping to motoring and vice versa or to accommodate reverse rotation without redirection of external fluid lines and with or without reversal in direction of fluid flow.
In exploring the field of available fluid power devices used primarily in high pressure applications for industrial, agricultural, and construction industries, it has not been possible to find a design which meets all of the above criteria which would be suitable for an automotive application for regenerative braking and acceleration. Because the energy storage device for the regenerative system is an accumulator with a piston acting on compressed nitrogen, it is not possible to control the operating pressure in and out of the accumulator. Therefore, to modulate braking and acceleration forces, a variable displacement pump/motor is used to accomplish a driver controllable torque level from the near constant pressure regenerative storage device.
Currently, the highest efficiency commercially available variable displacement hydraulic devices are bent shaft and wobble plate axial piston units which are relatively massive and expensive to manufacture. To meet the compact packaging criteria above, it is felt that a new design light weight high efficiency hydraulic vane pump/motor is desirable having high pressure capability.
SUMMARY OF THE INVENTION
This invention is a reversible variable displacement hydraulic dual-pressure compensated roller tipped vane pump and motor featuring a variable depth vane slot with tailored outer ring contour having over-center stroke adjustment. The unique features of the design are listed below:
Balanced pressure compensation in both pump and motor mode by utilizing a pressurized end plate with two compensation areas to apply clamping forces proportional to the two operating pressures (inlet and outlet), thus compensating for the internal separating forces.
Further fine tuning of the pressure balance by adding communication passages between the variable pressure portion of the swept volume and small compensation pistons which adjust the clamping force to the variable separating force based on the angular position of the rotor. With small numbers of vanes, five or seven for example, the separating force varies, and therefore the required clamping force must adjust, by more than 15% based on the position of the vane as it moves through the pressure transition areas.
Ports in each of the end plates communicate with the swept volume of the vanes (outer ports) as they pass through segments
1
and
3
. As a result of the vanes sweeping through the increasing and decreasing radial spaces, fluid flow is generated, which flow if resisted causes a pressure increase. This is the primary flow generating action of the pump, with the resulting flow passing through the outer ports.
There are additional ports (inner ports) which communicate with the inner extremity of the vane slots in all 4 segments. By having individual ports at the inner extremity of the vane slots in segments
1
and
3
, it is possible to use the radial motion of the vanes in the slots as piston pumps to add significantly to the primary pumping action. Therefore, in both segments
1
and
3
, the inner and outer ports are connected to each other. However, in segments
2
and
4
where there are no outer ports, there is maximum pressure unbalance on the vane and there can be minor amounts of radial motion depending on the ring configuration and displacement setting. Here, inner ports are required, fed by shuttle valves which supply the higher of the two pressures from segments
1
and
3
, to insure good vane contact with the outer ring, thus minimizing fluid leakage across the side loaded vane.
The vane slots are stepped to extend into the integral shaft and rotor in the shape of a “T”, with a deep excursion in the center and shallow portions on each side for each of the radial or angled slots between the two end plates. The ‘T’ shape of the vane and slots allows for maximum radial dimension of the vane in the deep excursion area to support the vane in all positions of extension. The shallow portions of the rotor slot add structure to the rotor body, stiffening the rotor and thus decreasing its deflection under the cantilever loading of the vanes as they are side loaded by the pressure differential.
A corresponding inner contour of the vane allows it to clear the stiffened rotor, thus allowing a long vane stroke for a given rotor diameter. This results in increased fluid displacement for a given package size while distributing the load transfer from the integral shaft to the rotor to the vane to the fluid with minimum distortion and stress concentration. In hydraulic devices, both friction losses and fluid leakage increase as the third power of the linear dimension, so that decreases in package size (diameter) have very significant improvements in operating efficiencies.
A hydrodynamically supported roller bearing is located at the tip of each vane parallel to the axis of rotation to minimize friction by building a film of oil to keep the roller supported in its pocket.
Vanes can be spring loaded radially outward to enhance low speed operation when centrifugal force is minimum.
Radial lightening holes can reduce vane mass to decrease speed bias holes are filled with plastic to reduce losses caused by fluid compression in the clearance volume.
Slots can be slanted to minimize radial sliding friction in the preferred direction of rotation as the vanes move radially in and out under load.
Full over-center stroke adjustment of the pivoting outer ring is controlled by a stepping motor and a lead screw or equivalent to accommodate transition from pumping mode to motoring mode without requiring a four way valve to reverse the external pressure connections.
Because the unit has the capability to operate both as a pump and as a motor, and is reversible in direction of rotation, and is variable in displacement, the outer ring which controls vane travel can be adjusted in its position relative to the rotor and housing. The further off center the ring is adjusted from the center of the rotor, the greater the fluid displacement for one revolution of the rotor. By adjusting the ring from one extreme position past center to the opposite extreme position, feed ports are essentially reversed in their function, so that, for a given direction of rotation and a given fluid connection, the unit operation switches from a fluid pump to a fluid motor or vice versa. As an example, port A, connected to a lower pressure source, communicates with an increasing volume inlet segment during pumping mode and a decreasing volume discharge segment during motoring mode.
Likewise, port B, connected to a higher pressure, communicates with a decreasing volume outlet segment during pumping mode and an increasing volume inlet segment during motoring mode. When
Brooks & Kushman P.C.
Vrablik John J.
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