AU772010B2 - Variable displacement pump - Google Patents

Description

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AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name of Applicant: Actual Inventor: Address for Service: Invention Title: Details of Associated Provisional Applications: ANTHONY JAMES GREENAWAY ANTHONY JAMES GREENAWAY HODGKINSON OLD McINNES Patent Trade Mark Attorneys Level 3, 20 Alfred Street MILSONS POINT NSW 2061 Variable Displacement Pump PQ9245 filed 7 August 2000 PR2658 filed 22 January 2001 t a *oo a a o*oo* The following statement is a full description of this invention, including the best method of performing it known to me: IP Australia Documents received on:

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Batch No: TECHNICAL FIELD The present invention relates to a variable displacement pump and more particularly to an internal gear pump with variable displacement.

BACKGROUND

Positive displacement pumps are commonly used in industrial hydraulic systems and in other oil delivery systems. Typically a positive displacement pump delivers to the system, a controlled amount of fluid per stroke, revolution, or cycle. Such a pump is typically referred to as one of fixed or variable displacement. Fixed displacement pumps have a displacement that cannot be changed without replacing certain components. However, it is possible with some fixed displacement pumps to vary the size of the pumping chamber (and the displacement) by using external controls. These pumps are known as variable displacement pumps.

One type of fixed displacement pump is the gerotor pump. The gerotor pump comprises a male rotor with n lobes which is located internally of and meshed with a female annulus having n 1 lobes. These two form a gerotor set which is driven either from the annulus or the rotor and the two turn relative to one another and about parallel axes. A series of chambers is formed between the •.•lobes and each chamber extends between two lines of contact between the rotor and annulus. These lines lie generally on the peaks, or maximum radius portions of the rotor lobes, and move along the annulus as the parts rotate at different speed. Hence the chambers increase in size as they proceed from a position adjacent a plane containing both axes and adjacent the point of full mesh between a male lobe and a female recess between lobes (or vice versa) towards a diametrically opposite position at a place where only the crests (maximum radius portions) of the lobes of both rotor and annulus meet. This travel is the induction stroke and fluid is sucked into the chambers as they follow this path from the inlet port at an axial end of the chambers.

2792C Similarly, as the chambers continue in their travel on the opposite side of said plane returning to the start point, they diminish and expel fluid through an outlet port.

As stated, pumps of the kind mentioned in the foregoing two paragraphs are well known and exist in many variations.

Such gerotor pumps are typically used in fixed displacement applications such as lubrication oil pumps in passenger vehicles. The present invention seeks to provide a internal gear pump which is cheap and compact in a similar manner to the known gerotor pump but which has a variable displacement.

SUMMARY OF THE INVENTION In one aspect the present invention consists of a pump comprising a pump body having an axially disposed cavity; a sleeve having a stepped bore movably mounted within said cavity; an externally lobed primary rotor having n-lobes accommodated within said sleeve; an internally lobed primary annulus member having n 1 lobes rotatably accommodated within said sleeve; the lobes of said primary rotor being in mesh with the lobes of said primary annulus member to radially provide a series of n interlobe working chambers therebetween, said primary rotor and said primary annulus member being rotatable about o o S respective parallel axes so that said working chambers rotate about said axes and continuously alternately increase and decrease in size; an inlet port and an o outlet port being provided to connect said working chambers with outside said pump body, said inlet port being located so that said working chambers move over said inlet port as said working chambers increase in size during one half revolution of said chambers and said outlet port being located so that said o 4 working chambers move over said outlet port as said working chambers decrease in size during a successive half revolution; wherein said primary annulus member within said sleeve is axially movable with respect to said primary rotor, and said pump further comprising an externally lobed secondary rotor having n 1 lobes and projecting in a close fit within the cavity of said primary annulus member, and an internally lobed secondary annulus member 2792C with n lobes into which a portion of said primary rotor projects into in a close fit, and said inlet port and said outlet port are located on a fixed shaft projecting axially through said primary rotor, said fixed shaft having two lines of communication to connect said inlet port and said outlet port with outside of said pump body, and said primary rotor having n spaced apart communication passages each of which extends from the inner bore of said primary rotor to the outer periphery of said primary rotor at a location between two of its lobes, and each said communication passage moves over said inlet port as a corresponding working chamber increases in size during said one half revolution of said chambers, and each said communication passage moves over said outlet port as a corresponding working chamber decreases in size during said successive half revolution of said chambers.

In the preferred embodiment said primary annulus member and said secondary annulus member are rotatably mounted in end to end relationship within said sleeve, and axially restrained therein.

In the preferred embodiment said primary rotor and said secondary rotor are mounted in end to end relationship within said primary annulus member, with said secondary rotor furthest away from said secondary annulus member.

In use, said sleeve, said primary annulus member and said secondary annulus °member are axially movable with respect to said primary rotor and said secondary rotor.

In a preferred arrangement two of said pumps can be connected in series to form a transmission wherein one of said two pumps acts as a motor.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described with reference to drawings in which: Fig. 1 is an exploded perspective view of various components of the pump according to a first embodiment of the present invention.

2792C Fig. 2 is an exploded elevation view of the various components of the pump shown in Fig.l.

Fig. 3 is a perspective view of the primary rotor and primary annulus member of the pump of Figurel that form a gerotor set.

Fig. 4 is a series of seven end views of the gerotor set shown in Fig 3, as the primary rotor rotates internally of the primary annulus member thereby forming a plurality of working chambers.

Figs 5a-5c are cross-sectional schematic elevational views of the various components of Fig 1 in an assembled configuration.

Fig.6 is an end view of a rotor of an alternate embodiment to that shown in Fig 1.

Fig. 7 is a cross sectional elevational view of the rotor shown in Fig. 6 Fig. 8 is an end view of an end plate used in conjunction with the rotor of Fig. 6.

:Fig. 9. is a cross sectional elevational view of the end plate shown in Fig. 8 MODE OF CARRYING OUT INVENTION ***Figures 1 and 2 depict exploded views of the various components of an embodiment of a pump in accordance with the present invention.

:The pump comprises a pump body (not shown) having a cylindrical cavity (not shown) disposed about a longitudinal axis X. A sleeve 1 is mounted within the cylindrical cavity and adapted for slidable axial movement therealong. A primary rotor 2 and a primary annulus member 3 are both housed within sleeve 1. Primary annulus member 3 is rotatably accommodated within sleeve 1.

Primary rotor 2 has four lobes and is to be located internally of and partially meshed with five lobes of primary annulus member 3.

2792C The pump further comprises a secondary rotor 4, a secondary annulus member and a fixed shaft 6. Secondary rotor 4 has five lobes that fit neatly inside the cavity of annulus member 3. Secondary annulus member 5 has an internal cavity with four lobes into which an end of primary rotor 2 fits neatly. Fixed shaft 6 projects axially into rotor 2, and is provided with two lines of fluid communication 7,8 which connect inlet port 9 and outlet port 10 with lines of fluid communication outside the pump body.

In operation, primary rotor 2 and primary annulus member 3 form a "gerotor set" as shown in Figures 3 and 4, in which both turn relative to each other and about respective parallel axes in a conventional manner. This gerotor set can be either driven from primary annulus member 3 or primary rotor 2. A series of working chambers 11 is formed between the lobes of primary rotor 2 and primary annulus member 3 and alternatively decrease and increase in size. As working chambers 11 move over inlet port 9 during one half revolution they increase in size, and as they move over outlet port 10 during a successive half revolution they decrease in size in a conventional "gerotor set" manner.

:'oo Whilst in a conventional "gerotor set" pump the volume of the pumping chamber is fixed, i.e. the axial length of the moving working chambers 11 is fixed, the embodiment of a pump according to the present invention has a pumping .oe.oi S° chamber with a variable axial length. This variability will now be described with reference to Figures 5a-5c. When the components are in an assembled :*:configuration, primary annulus member 3 and secondary annulus member 5 are rotatably mounted in sleeve 1 in an end-to-end relationship. Whilst they are each free to rotate within respective bearings 13 and 14, they are not free to move axially with respect to sleeve 1. Primary rotor 2 and secondary rotor 4 are both located internally of primary annulus member 3, with secondary rotor 4 furthest away from secondary annulus member Pumping chamber 12, is able to have its axial length, along axis X, varied by moving sleeve 1, and therefore primary annulus member 3 and secondary annulus member 5, relative to primary rotor 2 and secondary rotor 4. By varying 2792C the axial length of pumping chamber 12, its volume is varied. For ease of reference and clarity, the actuating means that moves sleeve 1 relative to primary rotor 2 and secondary rotor 4, has been omitted. Such actuating means may be of a mechanical, hydraulic or electrically driven type. Also, in order for the pump to operate primary rotor 2 and secondary rotor 4 must be held together, which is also not shown for ease of reference and clarity. Furthermore the various seals used with such a pump have also been omitted for ease of reference and clarity, however, it should be noted that "lip" seals or similar seals may be used.

When pumping chamber 12 is reduced in volume as shown in fig 5a, the pump is suitable for high rotational speed operation. When pumping chamber 12 is increased in volume as shown in Figure 5c the pump is suitable as a low rotational speed, high volume pump. In normal operation the pump is preferably run at a constant speed, with its output capable of being varied between high pressure and high volume.

Primary rotor 2 has four passages 15, as shown in Fig 1. Each passage *e extends from the inner bore 16 of primary rotor 2 to its outer periphery 17 at a trough between two lobes, to allow oil to move between inlet port 9 and outlet port 10 on fixed shaft 6 and pumping chamber 12. Each passage 15 moves over inlet port 9 as a corresponding working chamber 11 increases in size o during one half revolution of the chambers, and each passage 15 moves over outlet port 10 as a corresponding working chamber 11 decreases in size during the successive half revolution of said chambers.

One application of such a pump is supplying the power needed for vehicle 9power steering. Conventional power steering hydraulic pumps use considerable amounts of energy when the vehicle is being driven at high speeds and the power steering is not being used. In such a system the pump blows off through a relief valve when the vehicle is being driven at high speeds thereby wasting energy. If a pump of the type described earlier was used as power steering hydraulic pump, the chamber size of the pump could be varied with the car speed, so that at low speeds it is pumping a large volume, and at high speeds 2792C the chamber size is reduced to near zero, so that the pump capacity is near zero, thereby minimizing the energy being consumed.

Another application is where two such pumps are connected in series to form a large range vehicle transmission. In this transmission one pump drives the other, ie one of the pumps acts as a motor. If two such pumps are mounted in a single housing, the hydraulic frictional losses are minimised. By orientating them in an end-to-end relationship, the effective displacement of the pump is inversely proportional to that of the one acting as the motor. Increasing the force of the pump increases the force of the motor. This results in an effective squaring of the transmission range. When used as a vehicle transmission the rpm of a driving engine can be set to run at its most efficient or at its maximum power, and the transmission is solely responsible for the torque and speed delivered to the wheels.

In such an arrangement it would be possible to reverse the transmission by swapping port connections between the variable pump and the variable motor, so now the motor is fed from the other side.

The pump of the present invention could be used in a compact transmission for vehicles ranging from motorcycles to large earth moving equipment. It can also be used as variable speed control for hydraulic systems on cranes and bulldozers so that when there is a reduced load on buckets, blades or other hydraulically operated implements they can move at increased speeds.

The pump of the present invention could also function as a locking system as part of the large range vehicle transmission described earlier. In use if secondary rotor 4 and secondary annulus member 5 are brought into contact, then the volume in pumping chamber 12 becomes zero, this means that oil flow ceases. If this is used in the transmission of a vehicle, bringing secondary rotor 4 into contact with secondary annulus member 5, would act as a park brake. A conventional park brake would however still be required, as leaving the vehicle parked for extended periods may result in oil seepage from the pump and result in movement of the vehicle. It should also be noted that if secondary rotor 4 and 2792C secondary annulus member 5 are brought into contact with each other, then some other external gearing is required to ensure that primary rotor 2 and primary annulus member 3 will continue to speed at the correct ratio. If no external gearing is used then a physical limit will have to be introduced so that the primary rotor 2 and primary annulus member 3 are never fully out of mesh so that the pumping volume never becomes zero. Valves would then be needed to provide a "neutral" and/or "lock", which would be a "neutral" and/or "park" when used in the- transmission embodiment.

In the abovementioned embodiment fluid enters and leaves the interior of the pump through inlet port 9 and outlet port 10, respectively. These ports 9,10 are connected to outside of the pump body via two lines of communication 7,8 which run through shaft 6 projecting axially into rotor 2. In an alternative embodiment, as shown in Figs 6-9, the rotor 2 is replaced by annulus 2a and an adjacent end plate 25. In such an arrangement, the fluid enters and leaves the pump body via inlet and outlet ports 26,27 in end plate 25 which communicate with five lines of fluid communication 30 that run through annulus 2a. The end plate 25 has two milled slots 28,29 which fluidally communicate lines 30 with inlet and outlet ports 26,27 as annulus 2a is rotated. Thus as annulus 2a o o rotates, fluid may be directed to flow to and from the working chambers 11 as o: lines 30 are exposed to slots 28,29.

°eame It should be understood that in another not shown embodiment, the end plate may be replaced with a ported ring surrounding annulus 2a. The ring may o o::have inlet and outlet ports on its outer circumferential surface fluidally communicating with ports on inner circumferential surface, which inturn fluidally communicate with ports on the outer surface of annulus 2a, as it rotates. These ports on the outer surface of annulus 2a in turn are in fluid communication with lines of fluid communication 30 in annulus 2a.

It should be understood that where the actuating means by which sleeve 1 is moved relative to primary rotor 2 and secondary rotor 4 is hydraulic, the pump may utilise an "auto ratio changing" system. Such a system will be described without reference to drawings. The system may typically include a bias means 2792C such as a mechanical spring to biasedly urge the pump to the maximum volume (minimum pressure) state. Acting against the bias means is a hydraulic cylinder that is energised from the pump. As the load increases the pressures will also increase thereby causing the hydraulic cylinder to increase the force against the bias means, thereby decreasing the volume of the chamber and taking load off the engine driving the pump. If the load is removed from the pump, then the opposite will occur ie. the bias means will overcome the pressure of the hydraulic cylinder, and therefore put the pump into a higher volume operation.

Whilst some of the applications referred to would involve transmission fluid or hydraulic oil as the fluid being pumped, it should be understood that the pump of the present invention may be used for pumping other fluids such as water.

The term "comprising" as used herein is used in the inclusive sense of "including" or "having" and not in the exclusive sense of "consisting only of'.

0 2792C

Claims (7)

1. A pump comprising a pump body having an axially disposed cavity; a sleeve having a stepped bore movably mounted within said cavity; an externally lobed primary rotor having n-lobes accommodated within said sleeve; an internally lobed primary annulus member having n 1 lobes rotatably accommodated within said sleeve; the lobes of said primary rotor being in mesh with the lobes of said primary annulus member to radially provide a series of n interlobe working chambers therebetween, said primary rotor and said primary annulus member being rotatable about respective parallel axes so that said working chambers rotate about said axes and continuously alternately increase and decrease in size; an inlet port and an outlet port being provided to connect said working chambers with outside said pump body, said inlet port being located so that said working chambers move over said inlet port as said working chambers increase in size during one half revolution of said chambers and said outlet port being located so that said working *chambers move over said outlet port as said working chambers decrease ~in size during a successive half revolution; wherein said primary annulus :member within said sleeve is axially movable with respect to said primary rotor, and said pump further comprising an externally lobed secondary .oo..i rotor having n 1 lobes and projecting in a close fit within the cavity of said primary annulus member, and an internally lobed secondary annulus member with n lobes into which a portion of said primary rotor projects into in a close fit, and said inlet port and said outlet port are located on a fixed shaft projecting axially through said primary rotor, said I° ~fixed shaft having two lines of communication to connect said inlet port and said outlet port with outside of said pump body, and said primary rotor having n spaced apart communication passages each of which extends from the inner bore of said primary rotor to the outer periphery of said primary rotor at a location between two of its lobes, and each said communication passage moves over said inlet port as a corresponding working chamber increases in size during said one half revolution of said 2792C chambers, and each said communication passage moves over said outlet port as a corresponding working chamber decreases in size during said successive half revolution of said chambers.

2. A pump as claimed in claim 1, wherein said primary annulus member and said secondary annulus member are rotatably mounted in end-to- end relationship within said sleeve, and axially restrained therein.

3. A pump as claimed in claim 1 or claim 2, wherein said primary rotor and said secondary rotor are mounted in end to end relationship within said primary annulus member, with said secondary rotor furthest away from said secondary annulus member.

4. A pump as claimed in any one of claims 1 to 3, wherein said sleeve, said primary annulus member and said secondary annulus member are axially movable with respect to said primary rotor and said secondary rotor.

A vehicle transmission comprising two pumps connected in series each of which is of the type claimed in any one of claims 1 to 4, wherein one of said two pumps acts as a motor. ooooo

6. A pump as substantially hereinbefore described and with reference to the accompanying drawings.

7. A vehicle transmission comprising two pumps as substantially hereinbefore described and with reference to the accompanying drawings. Dated this 6th day of August 2001. ANTHONY JAMES GREENAWAY BY: HODGKINSON OLD MclNNES Patent Attorneys for the Applicant 2792C