GB2026094A - Rotary positive-displacement fluid-machines - Google Patents

Abstract

A sliding-vane pump 10 has a cam ring 16 pivotally mounted on a pin 14 so that its eccentricity relative to a rotor 36 can be varied to regulate the output. The ring is positioned in relation to the rotor by fluid pressure in a chamber 62. The axis of the inner surface 44 of the ring is always located in a lower right-hand quadrant between a line 52 through the pivot axis 54 and the axis 50 of the rotor and a perpendicular line 56 through the axis 50 so as to stabilize the ring. <IMAGE>

Description

SPECIFICATION Variable displacement valve pumps This invention relates to variable-displacement vane pumps.

More particularly, the invention is concerned with variable-displacement vane pumps having a pivoting ring.

Variable-displacement vane pumps have been used previously in automatic transmission control systems, but such prior-art devices have generally been of the sliding-ring type in which the control thereof is maintained by a spring and control pressures in chambers on both sides of a sliding ring.

Prior-art pivoting-ring type variable-displacement vane pumps have not proved satisfactory in overcoming the control instability problem inherent in such pumps without the use of very strong control springs or the use of dual chamber control systems.

By the present invention there is provided a variable-displacement vane pump comprising a housing, inlet and discharge ports formed in the housing, a drive shaft rotatably mounted in the housing, a rotor connected to be driven by the drive shaft and coaxially aligned therewith, a plurality of radially extending vanes slidably disposed in the rotor, pivot means disposed in the housing, a ring member pivotally disposed on the pivot means in the housing and co-operating with the housing to form a displacement control chamber, the ring member having a central axis eccentric to the axis of the rotor, the ring member co-operating with the rotor and the vanes to form a plurality of pumping chambers that in operation are successively connected to the inlet and discharge ports and thereby create an internal pressure force adjacent the discharge port which force is directed to establish a moment continuously in one direction on the ring member about the pivot means, and means for pressurizing the control chamber to establish a controlled moment on the ring member about the pivot means in a direction opposite to the first-mentioned moment, the said controlled moment being operable to control the pivotal position of the ring member to thereby control the displacement of the pump, and the pivotal position of the centre of the ring member being confined to a quadrant defined by a pair of perpendicular lines one of which intersects the axis of the rotor and the other of which intersects the axes of the rotor and the pivot means.

Thereby, it is possible to overcome the inherent instability of variable-displacement vane pumps, inasmch as the net internal reaction force on the pivoting ring can be maintained in a manner such that the resultant moment about the pivot axis is in one direction in opposition to the control pressure, this result being achievable with a variabledisplacement vane pump having a single control chamber and a pivotally controlled ring operated on by a directionally controlled internally generated pressure reaction force, such force being directed to always establish a moment in one direction about the pivot point of the ring in opposition to an externally supplied control pressure.

In the accompanying drawings: Figure 1 is an elevational view of one embodiment of a variable-displacement vane pump in accordance with the present invention, with a pump cover removed; Figure 2 is a section on the line 2-2 of Fig.

1 in the direction of the arrows; and Figure 3 is a diagrammatic representation illustrating reaction forces on the pump ring.

In the drawings, Figs. 1 and 2 show a variable-displacement vane pump, generally designated 10, having a housing 1 2 in which is secured a pivot pin 14. A ring member 1 6 is pivotally mounted on the pin 14, and is slidably supported at 1 8 on a surface 20 formed in the housing 1 2. The ring member 1 6 is urged to the maximum-displacement position shown in solid lines by a compression spring 22 which is disposed in a cylindrical opening 24 formed in the housing 1 2 and abuts a lug 26 formed on the ring 16.

A pump drive shaft 28 is rotatably mounted in the housing 1 2 by way of a needle bearing 30, and has a splined end 32 drivingly connected to internal splines 34 formed on a pump rotor 36. The pump rotor 36 has a plurality of radial slots 38 formed therein, in each of which slots 38 is slidably disposed a vane member 40. The vanes 40 are urged outwardly by a pair of vane control rings 42 and by centrifugal force, towards a cylindrical surface 44 formed on the ring 1 6.

The housing 1 2 has formed therein a pair of kidney-shaped ports 46 and 48 which provide discharge and inlet ports respectively for the pump 10. A plurality of chambers 47 are formed by the vanes 40, rotor 36 and surface 44. The chambers 47 rotate with the rotor 36 and expand and contract during rotation, as is well-known in vane-type pumps.

The inlet port 48 accepts fluid from a reservoir, not shown, and passes the fluid to the chambers 47. The vanes 40 carry the fluid in the chambers 47 from the inlet port 48 to the discharge port 46. As can be seen in Fig. 1, if the pump rotor 36 is rotating in a counterclockwise direction, the chambers 47 are continually expanding, to take in fluid, in the area of the inlet port 48, and are contracting, to discharge fluid, in the area of the discharge port 46.

The drive shaft 28 has a central axis 50 which is intersected by an axis 52 passing through the central axis 54 of the pivot pin 1 4. The central axis 50 is also intersected by an axis 56 which is disposed at right angles to the axis 52. In the position shown by solid lines in Figure 1, the centre of the cylindrical surface 44 is located at 58, and when the pump is moved to the minimum-displacement position shown in phantom lines, the centre of cylindrical surface 44 is located at 60.

The position of the ring 1 6 is established by control pressure in a chamber 62 which extends about the outer circumference of the ring 1 6 from the pivot pin 14 to a seal member 64 disposed in a groove 66 formed in the ring 1 6. The seal member 64 is urged outwardly against the surface 20 of the housing by a resilient backing member 68. Thus, the control fluid is confined to what is essentially a semi-annular-cylindrical chamber.The spring 22 acts in opposition to the control fluid in the chamber 62 such that as the pressure in the control chamber 62 increases, the pump ring 1 6 will be moved clockwise about the pivot pin 1 4. The left face, as seen in Figure 2, of the pump ring 16, rotor 36 and chambers 47 is closed off by a cover 70 which is secured to the housing 1 2 by a plurality of fasteners 72. Leakage from the chambers 47 radially outwardly past the cover 70 is prevented by a seal ring 74 disposed in a groove 76 formed in the ring 1 6 and urged towards the cover by a resilient backing ring 78. Any fluid leakage which occurs in a radially inward direction passes through the bearing 30 and combines with the converter return fluid, not shown.

The fluid pressure in the control chamber 62 is supplied by a regulator valve generally designated 80, which includes a housing 82 having a small-diameter bore 84 at the lefthand end thereof and a large-diameter bore 86 at the right-hand end thereof. A pair of control plugs 88 and 90 are disposed in the bore 86. The plug 88 has a central bore 92 in which is slidably disposed a plug valve 94.

A regulator valve spool 96 is slidably disposed in the bore 84 and in a stepped bore 98 formed in the plug 90. The housing 82 has formed therein a plurality of ports 100, 102, 104,106,108, 110and 112. The ports 100 to 106 are in fluid communication with the bore 84, the port 108 is in fluid communication with the bore 98, the port 110 is in fluid communication with the space between the plugs 88 and 90, and therefore with the right-hand end of the valve spool 96, and the port 11 2 is in fluid communication with the bore 92 and therefore with the right-hand end of the plug valve 94.The valve spool 96 has formed thereon a plurality of spaced equaldiameter lands 114, 116 and 118, and a larger-diameter land 1 20. The land 1 20 serves as a spring weight for a compression spring 1 22 disposed between the plug 90 and land 1 20 to bias the valve spool 96 towards the left, as viewed in Figure 1. The area of the spring 1 22 is open to the reservoir through an opening 1 23. The valve spool 96 also has a large-diameter land 1 24 and a small-diameter land 1 26 which are slidably disposed in the stepped bore 98 of the plug 90. The lands 1 24 and 1 26 can be formed on a separate valve spool, if desired.

The land 114 prevents fluid communication between the ports 100 and 102, the land 11 6 provides controlled fluid communication between the ports 104 and 102, and the valve land 11 8 provides controlled fluid communication between ports 104 and 106 and between port 106 and opening 123. The ports 100 and 104 are interconnected by a line pressure passage 1 28 which is in fluid communication with the discharge port 46 of the pump 10 and therefore subject to the output pressure of the pump 10 to supply pressurized fluid to a conventional transmission and control, not shown. The port 102 is in fluid communication with a conventional torque converter, not shown, and the port 106 is in fluid communication with the through passage 1 30 with the control chamber 62.The ports 108,110 and 112 are connected by way of respective passages to the transmission control system, and receive signals for reverse boost, intermediate boost and T-V boost, respectively. The use of such boost signals is well-known to those skilled in the art of transmission controls. These boost pressures, as is known, assist the spring 1 22 to establish control pressure levels with the passage 1 28 in accordance with the drive range selected and the torque requirement of the vehicle.

The fluid pressure in the passage 1 28 acts on the left-hand end of the land 11 4 to urge the valve spool 96 to the right against the bias of the spring 122 and whatever boost pressure is present. When the fluid pressure in the passage 1 28 is sufficient to move the valve spool 96 to the right, the valve land 11 6 permits fluid flow from the port 104 to the port 102 so that the torque converter is supplied with fluid pressure. Upon further movement of the valve spool 96 to the right, the valve land 11 8 will permit fluid communication between the ports 104 and 106, and therefore will direct fluid pressure to the control chamber 62. The port 106 is opened by the valve land 11 8 when the pump is supplying more fluid than is required by the transmission. Accordingly, at this time, the pump displacement is to be decreased. As the pressure is developed in the control chamber 62, the pump ring 1 6 will pivot about the pin 14 in a clockwise direction against the bias of the spring 22, thereby reducing the eccentricity between the central axis 50 of the rotor 36 and the central axis of the cylindrical surface 44. Thus, the central axis of the cylindrical surface 44 will be moved from the position 58 towards the position 60.When the axis reaches the position 60, minimum pump displacement has been reached, and the fluid supplied at this point is sufficient to satisfy torque converter flow requirements, transmission lubrication requirements and leakage which occurs in the system. If system pressure should decrease, the valve spool 96 moves to the left to connect the port 106, and therefore the chamber 62, to the opening 123, thus relieving the pressure in the chamber 62 so that the spring 22 will move the ring 1 6 counterclockwise to increase pump displacement.

Under most operating conditions, the axis of the cylindrical surface 44 will be at the maximum-displacement position 58 during low-speed conditions and at the minimumdisplacement position 60 during high-speed conditions. As the vanes 40 are rotated from the inlet port 48 to the discharge port 46 and vice versa, a pressure transition takes place within the chambers 47. The pressure transition occurs along a line which passes through the central axis 50 of the rotor 36 and the axis of the cylindrical surface 44. At low speeds this transition line is represented by a line 1 32 in Figure 3, and at high speeds by a line 1 34 in Figure 3. Since the cylindrical surface 44 of the ring is subjected to the internal pressure generated in the chambers 47, the ring is inherently unbalanced during operation.The net resultant reaction force due to the internal pressure generated passes through the central axis of the cylindrical surface 44 normal to the pressure transition line. As shown in Figure 3, the net reaction force on the ring at low speeds is in the direction of an arrow 136, and at high speeds is in the direction of an arrow 1 38. It will be appreciated from Figure 3 that these reaction forces always provide a counterclockwise moment about the axis 54 which is in opposition to the clockwise moment generated by the control pressure in the chamber 62. It should also be noted from Figure 3 that the net reaction force at the central axis of the cylindrical surface 44 is always confined to the lower right-hand quadrant formed by the perpendicular axes 52 and 56.

Prior-art pivoting ring pumps have been designed such that the central axis of the pivoting ring is aligned with the centre of the rotor and the centre of the pivot pin at the mid-position of pump displacement. In such types of pump, the net resultant force must therefore establish a moment about the pivot pin which changes direction as the pump passes through the mid-point of its displacement. Other pivoting-type vane pumps have been designed such that the central axis of the ring passes from the upper right-hand quadrant to the lower right-hand quadrant of the diagram shown at Figure 3, which also results in a reversal of the resultant moment about the pivot pin 1 4.

As will be appreciated from the foregoing discussion, the present invention overcomes the moment reversal which occurs in these prior-art devices, thereby substantially improving the control stability of a pivoting ring-type vane pump.

In the context of an automatic transmission control system, it is possible by the use of such an improved vane pump to provide an increase in the efficiency of the transmission control system, leading to a useful saving in fuel.

Claims (3)

1. A variable-displacement vane pump comprising a housing, inlet and discharge ports formed in the housing, a drive shaft rotatably mounted in the housing, a rotor connected to be driven by the drive shaft and coaxially aligned therewith, a plurality of radially extending vanes slidably disposed in the rotor, pivot means disposed in the housing, a ring member pivotally disposed on the pivot means in the housing and co-operating with the housing to form a displacement control chamber, the ring member having a central axis eccentric to the axis of the rotor, the ring member co-operating with the rotor and the vanes to form a plurality of pumping chambers that in operation are successively connected to the inlet and discharge ports and thereby create an internal pressure force adjacent the discharge port which force is directed to establish a moment continuously in one direction on the ring member about the pivot means, and means for pressurizing the control chamber to establish a controlled moment on the ring member about the pivot means in a direction opposite to the first-mentioned moment, the said controlled moment being operable to control the pivotal position of the ring member to thereby control the displacement of the pump, and the pivotal position of the centre of the ring member being confined to a quadrant defined by a pair of perpendicular lines one of which intersects the axis of the rotor and the other of which intersects the axes of the rotor and the pivot means.

2. A variable-displacement vane pump according to claim 1, in which the pivot means comprises a pivot pin having a longitudinal axis parallel to the longitudinal axis of the rotor and to the central axis of the ring member, and the said one of the pair of perpendicular lines is perpendicular to the longitudinal axis of the rotor and the other is perpendicular to the longitudinal axes of the rotor and of the pivot pin.

3. A variable-displacement vane pump substantially as hereinbefore particularly described and as shown in the accompanying drawing.