Variable Displacement Hydraulic Pump

Abstract

A variable-capacity, positive displacement pump having a rotor, pumping vanes or slippers carried by said rotor, a cam ring surrounding said rotor and cooperation therewith to define pumping chambers, a pump body surrounding said cam ring and connected thereto with a pivotal connection whereby the pump body and the cam ring define opposed pressure chambers, and regulator valve means for controlling the pressures distributed to each of said pressure chambers whereby the position of said ring with respect to said rotor may be changed to vary the displacement of the pump.

Description

GENERAL DESCRIPTION OF THE INVENTION

My invention relates generally to positive displacement pumps, and is adapted especially to be used as a pressure source for control systems for automatic power transmission mechanisms, although it is capable also of other uses. One of the other uses may be a power steering pump in a power steering system for automotive vehicles. In the particular embodiment disclosed in this specification, provision is made for adapting the pump for use as an automatic power transmission pump which would be driven by the vehicle engine.

Automatic power transmission mechanismsrequire fluid pressure operated servos, which control the relative motion of planetary gear elements during speed ratio changes. The servos are supplied with pressure from a fluid pressure source, and a valve controlled circuit provides selective pressure distribution from the pressure source to the servos as ratio changes are accomplished.

The circuit pressure maintained in the servos should be adequate to meet changing torque requirements. A high circuit pressure is required when the torque transfer through the driveline is high, but it should be lowered when torque requirements are lower. The pump that supplies circuit pressure to the system should be of sufficient capacity to supply the most extreme pressure requirements. When the vehicle is operating under conditions that do not require maximum torque delivery, the pump is required to bypass its fluid through a pressure regulator valve system since the pump output normally is maintained at a constant value for any given speed regardless of the torque being delivered.

My improved pump structure will make it possible to vary the capacity of the pump so that its fluid delivery is adequate to meet the existing torque requirements for any given set of operating conditions, and need not be designed for operation at maximum fluid delivery when high fluid flow is not required to maintain adequate circuit pressure. I have achieved this variable capacity feature without the necessity for an increase in the size of the pump beyond that size that would be required for a conventional, fixed-displacement pump in a similar operating environment. The invention may be adapted readily to existing fluid circuits for automatic transmissions without the need for modifying the circuitry or adding additional circuit elements.

The variable displacement characteristic is achieved by providing a cam ring that surrounds a pump rotor and by pivotally mounting the cam ring on the associated pump housing so that the eccentricity of the cam ring with respect to the rotor may be changed when changes in fluid displacement are desired. The adjustable cam cooperates with the surrounding housing to define separate pressure zones on its opposed sides. The zones are separated by sealing elements situated between the periphery of the cam ring and the surrounding housing whereby the cam ring is subjected to opposed and balanced pressure forces. Fluid circuitry including an automatic pressure regulator valve is in fluid communication with each of the pressure zones so that the pressure balance or ratio of pressures across cam ring may be controlled.

The regulator valve circuitry includes a valve element having a pressure area that is in fluid communication with one pressure zone on one side of the cam ring. That same regulator valve element causes communication between the other pressure zone and a low pressure part of the system. This low pressure part of the system may be in fluid communication with a hydrokinetic torque converter in the automotive vehicle driveline, or it may be in fluid communication with an exhaust region. In any case, the regulating characteristics of the regulator valve element control the ratio of pressure forces acting on the cam ring. A change in that ratio can be induced by applying a regulating pressure force on the regulator valve element. That regulating force is made proportional to a pressure signal that is related functionally to engine torque. The output pressure established by the pump structure then is related functionally to the same signal. Any excess pump displacement beyond that required to maintain the necessary circuit pressure will be bypassed to the converter or to the exhaust region, as appropriate.

BRIEF DESCRIPTION OF THE FIGURE OF THE DRAWING

FIG. 1 shows a transverse cross-sectional view of a positive displacement pump of variable capacity which includes the improvements of my invention. It is taken along the plane of section line 1--1 of FIG. 2.

FIG. 2 is a longitudinal cross-sectional view taken along the plane of section line 2--2 of FIG. 1.

FIG. 3 shows an alternate pivotal connection between the cam ring and the pump housing which may be used instead of the pivotal connection shown in FIG. 1.

FIG. 4 is a cross-sectional view similar to the cross-sectional view of FIG. 1, although it shows a different pressure regulating valve arrangement in combination with positive displacement pumping elements.

BRIEF DESCRIPTION OF THE INVENTION

In FIG. 1, numeral 10 designates a stationary pump housing. It includes a circular wall 12, which may be bolted to a shoulder formed in a power transmission housing for an automotive vehicle driveline. The wall includes a circular opening 14 which receives a bushing 16 in which is journaled sleeve shaft 18. This sleeve shaft is connected to the impeller of a hydrokinetic torque converter, which in turn is driven by the vehicle engine not shown.

Pump housing 10 includes a circular main bore 20. A circular cam ring 22 is positioned within the bore 20, the diameter of the ring 22 being less than the diameter of the bore 20. The open end of the bore 20 is closed by cover flange 24 secured to stationary support shaft 26. Flange 24 in turn is secured by bolts to the wall 12.

Cam ring 22 is provided with a pivot extension 28 which is received in a registering slot 30 formed in the wall of the bore 20. A sealing pin is situated in a sealing groove 32 formed in the outer periphery of the cam ring 22 at a location displace 180.degree. from the extension 28. The sealing pin is identified by reference character 34. The location of the sealing pin 34 need not be directly opposite the extension 28. Its precise location is chosen to meet the special pressure balancing characteristics required by a particular design.

Rotatably mounted within the ring 22 is a rotor 36 which is provided with a plurality of peripheral notches 38. A slipper element 40 is mounted loosely within each notch 38, and it is biased radially outwardly by a slipper spring 42. The outer surface of the slipper engages the inner surface of the ring 22. The precise curvature of the slipper 40 at the slipper-cam ring interface is chosen so that a wedge of lubricating oil will be developed between the slipper and the cam ring thus providing a fluid bearing seal.

A low pressure port of arcuate shape is provided in the housing 10 as indicated by reference character 44. It communicates with a passage 46 which in turn is in fluid communication with the transmission sump. A fluid pressure outlet port of arcuate shape is provided also in the housing 10 as indicated at 48. It is in fluid communication with the high pressure outlet passage 50, which communicates with a so-called line pressure passage 52 which supplies circuit pressure for the automatic transmission control circuit.

A rotor 36 is eccentrically positioned within the ring 22. It cooperates with the cam ring to define a pumping cavity 54 of crescent shape. The rotor is arranged in general tangential disposition with respect to the inner surface of the cam ring 22, the point of tangency being generally identified by reference character 56.

The space between two adjacent slippers receives oil distributed to it through the port 44. This oil is carried through the crescent shaped pumping chamber and is delivered to the outlet port as the rotor rotates in a counter-clockwise direction as indicated in FIG. 1. The amount of eccentricity determines the shape and size of the pumping chamber 54, which in turn determines the displacement on the pump itself.

A second sealing pin 55 is positioned loosely in a slot 58 formed in the periphery of the ring 22. It is positioned approximately 90.degree. from extension 28. Sealing pin 55 cooperates with the extension 28 to define a pressure cavity 60. Sealing pin 34 cooperates with the extension 28 to define a sealing cavity 62, the arcuate extent of which is approximately twice that of the chamber 60.

Line pressure passage 52 is in communication with branch passage 64, which extends to the pressure chamber 60. A second branch passage 66 communicates with the pressure chamber 62 on the upper side of the cam ring 22. This same passage 66 makes communication with the feed circuit for the hydrokinetic torque converter which includes feed passage 68.

A pressure regulator valve element 70 is slidably positioned in valve chamber 72. Element 70 includes valve lands 74 and 76, the latter controlling distribution of pressure from line pressure passage 52 and low pressure branch passage 66, the former controlling distribution of pressure from line pressure passage 52 to exhaust port 78.

The upper end of land 74 is in fluid communication with the passage 52 and is subjected to the pressure therein thereby normally tending to urge regulator valve element 70 in an outward direction. This pressure force is opposed by pressure boost forces acting in the opposite direction on the valve element 70.

The pressure forces induced on the ring 22 in a downward direction by the pressure on the low pressure side of the regulator valve tends to decrease pump displacement. Pump line pressure, which acts on the lower side of the cam ring, opposes the pressure force acting on the upper side of the cam ring. These forces balance each other and adjust the pump eccentricity to provide the required amount of pump flow. The arcuate space between the sealing pins 55 and 34 communicates with the low pressure port 44 through a cross-over passage 80.

The pump line pressure force is determined in the usual way, and it responds to changes in the driven speed of the transmission mechanism and the torque requirements of the driveline. When the line pressure drops below its scheduled value, the regulator valve element 70 moves in an upward direction thereby diverting flow from the converter circuit and reducing the pressure on the upper side of the ring. The forces above and below the ring thus become unbalanced and the ring moves upwardly thereby increasing the pump flow and restoring the scheduled value. The regulator valve element 70 then moves downwardly thus increasing the pressure acting on the upper side of the ring and moving it down to reduce the pump flow.

Since the forces acting on the cam ring are balanced, the ratio of the forces that maintain that balance depends upon the location of the sealing pins. Additional pressures can be applied also to the ring if this is desired. For example, governor pressure may be used as a control variable in addition to the converter pressure. This would cause converter pressure to be reduced upon an increase in the vehicle speed.

In FIG. 3, I have shown an alternate pivot arrangement between the cam ring and the pump housing. In this instance, the cam ring may be provided with an eyelet extension 82. A pivot pin 84 is received through the eyelet extension 82 and is anchored in cooperating openings formed in the adjacent housing. This arrangement requires, however, the use of an additional seal pin 86 situated in seal recess 88. The location of the pin 86 is adjacent the pilot extension 82. The other elements of the pump of FIG. 3 have been identified by the same reference characters used for corresponding elements of the FIG. 1 construction, although prime notations are added.

In FIG. 4, I have shown an alternate regulator valve circuit for use in a structure similar to that of FIG. 1. In the embodiment of FIG. 4, I have used reference characters that correspond to reference characters used in identifying the elements of the circuit of FIG. 1, although double prime notations have been added. In the FIG. 4 embodiment, the regulator valve includes a modified valve element 90. This includes valve lands 92, 94 and 96 which register with internal valve lands formed in valve chamber 98.

Upon an increase in the pressure boost forces in the embodiment of FIG. 4, communication between line pressure passage 52' and the converter feed circuit is decreased, as is the degree of communication between the line pressure passage 52' and the branch passage 66' extending to the top side of the cam ring. This causes an increase in the displacement of the pump which results, of course, in an increase in the line pressure. The proper pressure balance then is restored to the value that corresponds to the pressure boost forces acting on the valve element 90.

Claims

Having thus described preferred embodiments of my invention, what I claim and desire to secure by U.S. Letters Patent is:

1. A positive displacement fluid pump comprising a pump body, a pump cam ring in said body, a pump rotor rotatably mounted in said cam ring, pumping elements carried by the periphery of said rotor and slidably registering with said cam ring, a pumping chamber defined by said rotor and said cam ring, inlet and outlet fluid ports communicating with said pumping chamber, a pivotal connection between said cam ring and said body, said connection accommodating movement of said cam ring within said body with respect to said rotor whereby eccentricity of said rotor with respect to said cam ring may be varied, a transverse opening in the outer periphery of said cam ring, at least one sealing pin situated between said housing and the cam ring and located in said transverse opening with a loose fit, said cam ring and said housing cooperating to define a pair of pressure chambers therebetween, said sealing pin isolating one pressure chamber with respect to the other, a first fluid connection between said outlet port and one fluid chamber, a second fluid connection between the other pressure chamber and a low pressure region of said system, and pressure regulator valve means in fluid communication with said fluid connections whereby pressure forces acting on said cam ring may be changed thus effecting variations in the fluid displacement of said pump.

2. The combination as set forth in claim 1 wherein said regulator valve means comprises a movable valve element having a pressure area thereon in fluid communication with said outlet port whereby a valve actuating force on said valve element is established, said pressure force tending to urge said valve element in a direction that increases the degree of communication between said fluid connections thereby varying the pressure force balance acting on said cam ring to decrease the displacement of said pump.

3. The combination set forth in claim 2 wherein said pump cam ring includes further a second transverse opening in said cam ring and a second sealing pin therein which is angularly spaced with respect to said one sealing pin and situated between the cam ring and said housing whereby the arcuate extent of said one pressure chamber is less than the arcuate extent of said other pressure chamber.

4. The combination set forth in claim 2 wherein the pivotal connection between said cam ring and said housing comprises innerconnected pivot elements one of which is formed on said housing and the other of which is formed on said cam ring, the pivot axis for said pivotal connection being parallel to the geometric axis of said rotor whereby the center of said cam ring and the center of said rotor substantially correspond to each other at a point midway between the two extreme positions.

5. The combination set forth in claim 1 wherein the pivotal connection between said cam ring and said housing comprises innerconnected pivot elements one of which is formed on said housing and the other of which is formed on said cam ring, the pivot axis for said pivotal connection being parallel to the geometric axis of said rotor whereby the center of said cam ring and the center of said rotor substantially correspond to each other at a point midway between the two extreme positions of said cam ring.

6. The combination set forth in claim 1 wherein said pump cam ring includes further a second transverse opening in said cam ring and a second sealing pin therein which is angularly spaced with respect to said one sealing pin and situated between the cam ring and said housing whereby the arcuate extent of said one pressure chamber is less than the arcuate extent of said other pressure chamber.

7. The combination set forth in claim 6 wherein the pivotal connection between said cam ring and said housing comprises innerconnected pivot elements one of which is formed on said housing and the other of which is formed on said cam ring, the pivot axis for said pivotal connection being parallel to the geometric axis of said rotor whereby the center of said cam ring and the center of said rotor substantially correspond to each other at a point midway between the two extreme positions of said cam ring.

8. The combination set forth in claim 3 wherein the pivotal connection between said cam ring and said housing comprises innerconnected pivot elements one of which is formed on said housing and the other of which is formed on said cam ring, the pivot axis for said pivotal connection being parallel to the geometric axis of said rotor whereby the center of said cam ring and the center of said rotor substantially correspond to each other at a point midway between the two extreme positions of said cam ring.