GB2406140A

GB2406140A - Roller vane pump whose displacement depends on outlet pressure

Info

Publication number: GB2406140A
Application number: GB0322124A
Authority: GB
Inventors: Brian Eric Knell; Adrian Comillus Shorten; Darren Anthony Lee; Robert Ashburner
Original assignee: Dana Automotive Ltd
Current assignee: Dana Automotive Ltd
Priority date: 2003-09-22
Filing date: 2003-09-22
Publication date: 2005-03-23
Also published as: GB0322124D0

Abstract

A variable displacement roller vane pump 10 includes a carrier 14 which can be rotated in a housing 12, which includes a cam 18 surrounding the carrier 14. The cam 18 can move relative to the carrier 14 about a pivot axis B, and is resiliently biassed in one direction about the pivot axis B to maximise pump displacement. There is a passage 32 in the housing 12 which allows outlet pressure to act on the cam 18 to oppose the resilient bias, such that the pump displacement varies depending on the pump outlet pressure. The pressure may act on an external surface 33 of the cam 18 over an angle of arc in a pressure chamber defined between the cam 18 and an outer housing part 12, the limits of the arc being defined by the pivot 39 and a seal member 36. The seal chamber 35 may decrease in section away from the pressure chamber, so that the seal 36 is urged into the smaller cross section by the fluid pressure in the chamber, to improve sealing. The slots 19 in the carrier 14 may extend at slight angles to radial, to improve sealing between the rollers 22 and the cam 18 at low speeds.

Description

2406 1 40 Title: Variable Displacement Roller Vane Pump

Description of Invention

This invention relates to a roller vane pump and more particularly to a roller vane pump which has a variable displacement.

The invention has particularly but not exclusively been developed for use as an oil lubrication pump for an internal combustion engine.

Fixed displacement roller vane pumps are able reliably to deliver fluid at a high pressure and are used in many applications. However in an internal combustion engine environment, it is desirable to limit the oil pressure to avoid possibly damaging the oil filter which is provided to filter the circulating lubrication oil. Where an oil pump is powered mechanically, for examples directly or via a transmission from the engine, it is common to provide some kind of pressure limiting device, so that excess pressure developed by the pump is not communicated to the oil filter.

Variable displacement roller vane pumps are known, for example from US early publication 2001/0036411 or international application W002/063 170, in which the position of a cam is varied by a motor in response to electrical signals, the position of the cam with respect to a rotating carrier carrying rollers which engage with the cam as the carrier rotates, being changeable to vary the volumes of pumping chambers formed between the cam, the carrier and adjacent pairs of rollers.

However, such proposals which require eleckical conkollers are expensive, and thus in applications where only a low cost unit is required, such as for example for an oil lubrication pump for an internal combustion engine, such prior proposals have not been useable.

: A: e: A. I: e . . e e ee. .e.. e According to a first aspect of the invention we provide a variable displacement roller vane fluid pump which includes a carrier which is rotatable in a housing about an axis of rotation, and the carrier carrying a plurality of rollers which are each received in respective slots which extend inwardly of a periphery of the carrier and permit the rollers to move inwardly and outwardly in use, the housing including a cam surrounding the carrier, pumping chambers being formed between the rollers, the carrier and the cam, the rollers engaging with the cam and moving inwardly and outwardly of their respective slots as the carrier rotates, in response to the position and configuration of the cam, so that the pumping chambers change in volume as the carrier rotates, to effect pumping of the fluid, from an inlet to an outlet of the pump, and wherein the cam is moveable relative to the carrier about a pivot axis which is generally parallel to the axis of rotation of the carrier to vary the displacement of the pump, there being a resilient biasing device to bias the cam in one direction about the pivot axis, and the housing including a passage which communicates with the outlet of the pump and communicates the outlet pressure of the pumped fluid from the outlet to act on the cam to oppose the biasing force of the resilient biasing device so that the pump displacement varies depending upon the pump outlet pressure.

By virtue of the invention, a roller vane pump may be provided for pumping lubrication oil in an internal combustion engine, the displacement and hence the outlet pressure being limited by the position of the cam, which depends upon the pump outlet pressure. Thus the invention provides a low cost solution to providing a roller vane pump with a variable displacement, which can be used such that the outlet pressure can be assured of not exceeding a pressure at which an oil filter of the oil circulation system may be damaged.

Desirably, the carrier is use, driven by a mechanical connection to a prime mover such as an output shaft of an internal combustion engine.

ë. : ë: .. :: :e . . . . . . . . . The inlet may include an inlet port which may lie on one side of a plane which contains the pivot axis, the resilient biasing device acting on the cam at the one side of the plane, whilst the outlet pressure acts on the cam on a second side of the plane opposite to the first side to oppose the biasing force of the resilient biasing device. Desirably the outlet pressure acts on the cam over a substantial angle of arc, in a pressure chamber established between the cam and an outer housing part. The pressure chamber may extend from adjacent the cam pivot through more than 90 , and more preferably through greater than 120 .

The axis of rotation of the carrier may lie on or preferably is close to the plane, and more preferably to the first side of the plane.

Preferably the pump includes a seal which acts between the cam and the outer housing part at a position to the second side of the plane and remote from the pivot axis of the cam, to prevent the higher pressure pumped fluid passing between the cam and the outer housing part to the lower pressure inlet.

Preferably the outer housing part and an external surface of the cam provide between them a seal chamber for the seal, the seal chamber decreasing in cross section towards the pump inlet, and the seal is generally cylindrical, having a cylindrical axis which extends generally parallel to the axis of rotation of the carrier, the seal in use being radially urged by the higher pressure pumped fluid along the decreasing cross section to provide sealing which becomes increasingly efficient as the differential between the outlet and inlet pressures increases.

Preferably the rollers carried by the carrier are generally cylindrical each having a cylindrical axis which is generally parallel with the axis of rotation of the carrier, and the rollers are free to move in their respective slots in response to forces experienced as the carrier rotates. To encourage the rollers to maintain a sealing contact with the cam at low carrier rotational speeds, the slots may extend at slight angles to the radial.

.e . cC e e c ë e as- .e According to a second aspect of the invention we provide an internal combustion engine having a lubrication system incorporating an oil lubrication pump according to the first aspect of the invention.

Embodiments of the invention will now be described with reference to the accompanying drawing which is a diagrammatic illustration of one embodiment of a variable displacement roller vane pump in accordance with the present invention.

Referring to the drawing there is shown an oil lubrication roller vane pump 10 which includes a housing 12 in which a carrier 14 is rotatable about an axis of rotation A. In this example the carrier 14 is connected, e.g. by a splined connection, to a prime mover 15 which is a driven shaft of an internal combustion engine. The housing 12 includes an outer housing part 16, and a cam 18, the cam 18 being movable relative to both the outer housing part 16 and the carrier 14 about a pivot axis B. as explained below, to achieve variance in the displacement of the pump 10.

The carrier 14 includes a plurality of slots 19 which extend inwardly of the carrier 14 from an outer periphery 20 of the carrier, each slot 19 accommodating a cylindrical roller 22 each of which may rotate and may move in its respective slot 19, inwardly and outwardly of the carrier 14, so that as the carrier 14 rotates, the rollers 22 are maintained in contact with an inner cam surface 24 of the cam 18, in response to forces experienced as the carrier 14 rotates. The rollers 22 rotate about their respective cylindrical axes, so that in such a pump 10, there is minimal wear due to the contact between the rollers 22 and the cam 18.

A centre of the cam 18 is offset with respect to the axis of rotation A of the carrier 14, and so as the carrier 14 rotates, pumping chambers 26 are formed between an adjacent pair of rollers 22, the inner cam surface 24 and the carrier 14, the pumping chambers 26 changing in volume as the carrier 14 rotates. The pumping chamber 26 volume is at a minimum immediately prior to an oil inlet ëee e e ë e e .

ë e e e eee e ace cee e e 28, increasing to a maximum at an opposite position. Thus low pressure oil is drawn from the inlet 28 into the pumping chambers 26 as the pumping chamber volumes increase, and higher pressure oil is discharged from the pumping chambers 26 as their volumes decrease, into an outlet.

In the example shown in the drawings, an inlet port is provided at an axial end of the pump 10, below the carrier 14 as drawn, a portion of the inlet port being visable at 28a. The port 28_ may extend arcuately so that oil may be drawn simultaneously into several of the pumping chambers 26 as their volumes increase.

The outlet from the pump 10 also includes a port, at an axial end of the pump 10, part of which can be seen at 29, and which outlet port 29 may extend arcuately so that oil may be discharged simultaneously from several of the pumping chambers 26, and slots 19, as their volumes decrease.

As seen in the drawing, generally through half of the carrier 14 revolution, indicated between the arrows I and It, oil will be drawn into the pump 10, whereas through the other half of the carrier revolution indicated between the arrows O and Of, oil will be discharged.

The maximum pumping chamber 26 volume is governed by the position of the cam 18 about the cam pivot axis B. and it will be appreciated that by moving the cam 14 about the cam pivot axis B. the displacement of the pump 10, and hence the oil pressure developed, may be varied.

In use, as engine speed increases, more oil will be pumped by the pump as the rotational speed of the carrier 14 will increase. To prevent the pressure developed exceeding a pressure at which an oil filter may be damaged, it is desirable to reduce the pump output by adjusting the position of the cam 18 in the outer housing part 16.

In accordance with the invention, a resilient biasing device 30, namely a coil spring, acts between the cam 18 and the outer housing part 16, so as to move the cam 18 about the pivot axis B so as urge the cam 18 such as to äct a c c . . B. maximise the volumes of the pumping chamber 26 as fluid is drawn into the pump 10, so as to maximise the displacement of the pump 10. However, to counter the biasing force of the spring 30, the pressure of pumped fluid from the outlet is communicated via a passage 32 to act on an external surface 33 of the cam 18, in a pressure chamber formed between the outer housing part 16 and the external surface 33 of the cam 18.

The pressure chamber extends from adjacent the pivot axis through about 120 , but preferably at least through 90 , to a seal chamber 35 where a seal 36 is provided, to prevent the higher pressure oil escaping to the low pressure inlet 28.

Thus as the pressure of the discharged oil at the outlet 29 increases, the cam 18 will be urged against the force of the spring 30 so as to reduce the displacement of the pump 10 and thus restrict the pressure of the oil in the lubrication system to below that at which the pressure could damage the oil filter.

Other features of the pump 10 are as follows.

As the rollers 22 only move outwardly into sealing engagement with the internal surface 24 of the cam 18 in response to the forces experienced as the carrier 14 rotates, at slow rotational speeds, there is some tendency for a reliable seal not to be maintained. Thus to assist in maintaining sealing, the slots 19 in which the rollers 22 are received, do not extend inwardly of the carrier 14 exactly radially, but the slots 19 are inclined to the radial, so that the rollers 22 more easily are moved by even weak rotational forces into sealing engagement with the inside surface 24 of the cam 18.

The slots 19 are shaped so that there is a narrow region furthermost inwardly of the carrier 14, so that a space is always preserved between the bottoms of the slots 19 and the rollers, so as not to resist inward roller 22 movement. Desirably, as the slots 19 approach the pump outlet 29, oil discharged axially from the slots 19 as the rollers 22 move inwardly of the act e a a * a b carrier 14, may be communicated to the outlet 29 at one or both of the axial ends ofthe pump 10.

The seal 36 which is provided to prevent the escape of oil from the pressure chamber to which the outlet pressure is communicated via the passage 32, is in this example cylindrical and may be made from metal, or a suitable synthetic material. The cylindrical axis of the seal 36 is generally parallel to the axis of rotation A of the carrier 14. The outer housing part 16 and external surface 20 of the cam 18 provide between them the seal chamber 35 which decreases in cross section towards the pump inlet 28. The seal 36 in use is radially urged by the higher pressure pumped fluid in the pressure chamber, along the decreasing cross section to provide sealing which becomes increasingly efficient as the differential between the outlet and inlet pressures increases.

In this example, the cam 18 is pivoted about axis B on a pivot pin 39 although other pivot arrangements may be employed.

Although in the example of the drawing, the resilient biasing device 30 is a coil spring, any other preferably simple mechanical, resilient biasing device may be provided as appropriate.

In the example shown in the drawing, the cam pivot axis B lies in a plane P1 which defines the extent of the pump inlet 28, which inlet 28 otherwise lies at a side of the plane P1 common to the resilient biasing device 30, and the axis of rotation A of the carrier 14 lies to the one side of the plane P1 too, e.g. in another plane P2. Other geometries are possible. Desirably though the resilient biasing device 30 acts in a direction generally perpendicular to the plane P1.

Although the invention has specifically been described in relation to an oil lubrication pump for an internal combustion engine, the invention may be employed in other applications where a low cost variable displacement pump is required.

eC e..a # a, e e a ee .

e e -. e.ae a The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

see e t e e a t a e tee e e e e. eta mitta a CLAIMS

1. A variable displacement roller vane fluid pump which includes a carrier which is rotatable in a housing about an axis of rotation, and the carrier carrying a plurality of rollers which are each received in respective slots which extend inwardly of a periphery of the carrier and permit the rollers to move inwardly and outwardly in use, the housing including a cam surrounding the carrier, pumping chambers being formed between the rollers, the carrier and the cam, the rollers engaging with the cam and moving inwardly and outwardly of their respective slots as the carrier rotates, in response to the position and - configuration of the cam, so that the pumping chambers change in volume as the carrier rotates, to effect pumping of the fluid, from an inlet to an outlet of the pump, and wherein the cam is moveable relative to the carrier about a pivot axis which is generally parallel to the axis of rotation of the carrier to vary the displacement of the pump, there being a resilient biasing device to bias the cam in one direction about the pivot axis, and the housing including a passage which communicates with the outlet of the pump and communicates the outlet pressure of the pumped fluid from the outlet to act on the cam to oppose the biasing force of the resilient biasing device so that the pump displacement varies depending upon the pump outlet pressure.

2. A pump according to claim 1 wherein the carrier is use, driven by a mechanical connection to a prime mover.

3. A pump according to claim 1 or claim 2 wherein the inlet includes an inlet port which lies on one side of a plane which contains the pivot axis, the resilient biasing device acting on the cam at the one side of the plane, whilst the outlet pressure acts on the cam on a second side of the plane opposite to the first side to oppose the biasing force of the resilient biasing device.

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4. A pump according to claim 3 wherein the outlet pressure acts on the cam over a substantial angle of arc, in a pressure chamber established between the cam and an outer housing part.

5. A pump according to claim 4 wherein the pressure chamber extends from adjacent the cam pivot through more than 90 , and more preferably through greater than 120 .

6. A pump according to any one of claims 3 to 5 wherein the axis of rotation of the carrier lies on or close to the plane.

7. A pump according to claim 6 wherein the axes of rotation of the carrier lies to the first side of the plane.

8. A pump according to any one of claims 3 to 7 wherein the pump includes a seal which acts between the cam and the outer housing part at a position to the second side of the plane and remote from the pivot axis of the cam, to prevent the higher pressure pumped fluid passing between the cam and the outer housing part to the lower pressure inlet.

9. A pump according to claim 8 wherein the outer housing part and an external surface of the cam provide between them a seal chamber for the seal, the seal chamber decreasing in cross section towards the pump inlet, and the seal is generally cylindrical, having a cylindrical axis which extends generally parallel to the axis of rotation of the carrier, the seal in use being radially urged by the higher pressure pumped fluid along the decreasing cross section to .... . . . . . . . . < . . . . . . . . . . . provide sealing which becomes increasingly efficient as the differential between the outlet and inlet pressures increases.

10. A pump according to any one of the preceding claims wherein the rollers carried by the carrier are generally cylindrical each having a cylindrical axis which is generally parallel with the axis of rotation of the carrier, and the rollers are free to move in their respective slots in response to forces experienced as the carrier rotates.

11. A pump according to claim 10 wherein to encourage the rollers to maintain a sealing contact with the cam at low carrier rotational speeds, the slots extend at slight angles to the radial.

12. A variable displacement roller vane pump substantially as hereinbefore described with reference to and/or as shown in the accompanying drawing.

13. An internal combustion engine having a lubrication system incorporating an oil lubrication pump according to any one of the preceding claims.

14. Any novel feature or novel combination of features described herein and/or as shown in the accompanying drawings.