GB2436594A

GB2436594A - A variable output pump assembly

Info

Publication number: GB2436594A
Application number: GB0606210A
Authority: GB
Inventors: Stephen Mark Hodge; Kevin Johanson
Original assignee: CONCENTRIC VFP Ltd
Current assignee: CONCENTRIC VFP Ltd
Priority date: 2006-03-28
Filing date: 2006-03-28
Publication date: 2007-10-03
Also published as: GB0606210D0

Abstract

The invention relates to a variable output pump assembly 10. The variable output pump assembly 10 comprises a rack and pinion rotor indexing means 64, 66 and a shuttle valve 74 which senses pressure LPO in the engine gallery or vicinity thereof or at any position in an engine lubrication circuit remote from die (high pressure) pump outlet. The variable output pump assembly 10 is arranged so that when a predetermined pressure is sensed by the sensor 74 the rotor indexing means 64, 66 is actuated, so as to move a first rotor 14 with respect to a second rotor 16. Pressure of the fluid from the pump outlet HPO causes the rotor indexing means 64, 66 to be actuated.

Description

A VARIABLE OUT?TJT PUMP The invention relates to a variable output

pump.

It is known to index a first rotor with respect to a second rotor so as to vary the output from a pump. Typically this is achieved using a rack and pinion arrangement. The pinion is fast with the movable rotor and the rack is meshed to the pinion. The rack is then mounted on a piston rod and the piston rod is movable depending on pressurised fluid supplied to the cylinder housing the piston rod.

Ii. is known to use pressurised fluid from the maximum system pump outlet for indexing. The downside of this method is that the pressure at the pump outlet is not always representative of the needs of the bearings and engine as a whole.

In an attempt to make the pump operation more relevant to the needs of the engine, it is known to sense arid utilise pressurised fluid from the gallery rifle of the IC. engine supplied by the pump. This is an improved method from an engine supply point of view, but means that fluid at a much reduced pressure is used for indexing. This fluid has to overcome the higher internal pump pressure in the rotors. The Applicant recognised that under certain conditions the gallery pressure can be too low to overcome the internal pump loading, with the pump failing to index properly.

it is an aim of the invention to provide an improved means of indexing one rotor with respect to another rotor of a variable output pump assembly.

According to a first aspect of the invention there is provided a variable output pump assembly comprising a pump, rotor indexing means, and a sensor, wherein the sensor is in fluid communication with an engine gallery or vicinity thereof; the sensor is az-ranged to sense pressure at a position in the engine lubrication circuit remote from S the pump outlet, and the rotor indexing means is in communication with the pump outlet, enabling fluid from the pump outlet to cause actuation of the rotor indexing means.

According to a second aspect of the invention there is provided a variable output pump assembly comprising a pump, rotor indexing means, and a sensor, wherein the sensor is in fluid communication with an engine gallery or vicinity thereof, the sensor is arranged to scnse pressure in the engine gallery or vicinity thereof; and the rotor indexing means is in communication with the pump outlet, enabling fluid from the pump outlet to cause actuation of the rotor indexing means.

The assembly is preferably arranged so that when a pressure less than a predetermined pressure is sensed by the sensor, the rotor indexing means is actuated so as to move the first rotor in a first direction with respect to the second rotor.

The assembly is preferably arranged so that whcn a prcssurc greater than a predetermined pressure is sensed by the sensor, thc rotor indexing means is actuated so as to move a first rotor in a second direction with respect to the second rotor.

The sensor preferably comprises a valve assembly which moves at the pre determined pressure.

The valve assembly is preferably arranged so that its movement enables actuation of the rotor indexing means.

Preferably, the assembly is arranged so that when a pressure less than a predetermined pressure is sensed, fluid from the engine gallery does not move the valve assembly, and the pump outlet is in fluid communication with the indexing means allowing movement of the indexing means in a first direction.

Preferably, the assembly is arranged so that when a pressure greater than a predetermined pressure is sensed, fluid ti-om the engine gallery moves the valve assembly. and the pump outlet is in fluid commirnieation with the indexing means allowing movement of the indexing means in a second direction, In one preferred embodiment of the invention, the valve assembly comprises a spool valve.

Preferably, the assembly is arranged so that when a pressure less than a predetermined pressure is sensed, fluid from the engine gallery does not move the spool valve, and the pump outlet is in fluid communication with the indexing means through the spool valve allowing movement of the indexing means in a first direction.

Preferably, the assembly is arranged so that when a pressure greater than a prcdetemined pressure is sensed, fluid from the engine gallery moves the spool valve, and the pump outlet is in fluid communication with the indexing means through the spool valve allowing movement of the indexing means in a second direction.

Preferably. the spool valve also comprises an exhaust fluid outlet.

For a light automotive vehicle, the predetermined pressure which commences indexing may be the gallery pressure at an engine speed corresponding to between 500 and 1000 rpm. For a light automotive vehicle, preferably the gallery pressure at an engine speed corresponding to between 700 and 800 rpm. For a light automotive vehicle, most preferably the gallery pressure at an engine speed corresponding to about 750 rpm.

For a heavy automotive vehicle such as a truck, the predetermined pressure which commences indexing may be the gallery pressure at an engine speed corresponding to between 1000 and 2000 rpm, preferably the gallery pressure at an engine speed corresponding to between 1400 arid 1800 rpm, most preferably the gallery pressure at an engine speed corresponding to about 1600 rpm.

The assembly is preferably arranged so that at a predetermined pressure of between 3 and S bar, the rotor indexing means is actuated, preferaby about 4 bar. )

In one preferred embodiment of the invention, the first rotor is movable rotationally with respect to the second rotor, and the indexing means is arranged to rotate the first rotor with respect to the second rotor According to a third aspect of the invention there is provided a method of indexing a first rotor with respect to a second rotor in a variable output pump, the method comprising the steps of sensing pressure at a position in an engine lubrication circuit remote from the pump outlet, and using the pump outlet pressure of the pump to effect indexing of the first rotor with respect to the second rotor.

According to a fourth aspect of the invention there is provided a method of indexing a first rotor with respect to a second rotor in a variable output pump, the method comprising the steps of sensing the gallery pressure of an engine or in the vicinity of the gallery, and using the pump outlet pressure of the pump to effect indexing of the I $ first rotor with respect to the second rotor.

The method preferably comprises, when a pressure less than a predetermined pressure is sensed by the sensor, actuating the rotor indexing means so as to move the first rotor in a first direction With respect to the second rotor.

The method preferably comprises, when a pressure greater than a predetermined pressure is sensed by the sensor, actuating the rotor indexing means so as to move the first rotor in a second direction with respect to the second rotor.

The predetermined pressure may be the gallery pressure at an engine speed corresponding to between 500 and 1000 rpm, preferably the gallery pressure at an engine speed corresponding to between 700 and 800 rpm. most preferably the gallery pressure at an engine speed corresponding to about 750 rpm.

The method preferably comprises arranging a spool valve to sense the pressure.

The method preferably comprises, when a pressure less than a predetermined pressure is sensed, not moving the spool valve with fluid from the engine gallery, and arranging the pump outlet in fluid communication with the indexing means through the spool valve allowing movement of the indexing means in a first direction.

The method preferably comprises, when a pressure greater than a predetermined pressure is sensed, moving the spool valve with fluid from the engine gallery, and arranging the pump outlet in fluid communication with the indexing means through the spool valve allowing movement of the indexing means in a second direction.

The method of indexing may cotflpnse any steps corresponding to features of the variable output pump assembly of the firsi. aspect of the invention.

With the variable output pump assembly and the method of the invention, the higher pump outlet pressure is always utilised for indexing, but the lower gallery pressurc is sensed by the valve, ensuring the flow from the pump is accurately tailored to the needs of the engine.

The gallery pressure is preferably completely isolated Cram the indexing circuit and plays no role other than to detarmine the point at which indexing, e.g. by the spool valve, operates.

The higher pump pressure however is utiliscd for indexing which ensures sufficient force is available to overcome any internal resistance there may he to indexing.

Ii should be noted that preferably the higher pump pressure is balanced in the spool by virtue of the opposed shoulders and therefore plays no part in determining the movement of the spool.

A variable output pump assembly, and method of indexing, in accordance with the invention will now be described, by way of example only and with reference to the following accompanying drawings in which:-Figure 1 is a cross sectional elevation of a split rotor gcrotor pump which is controllable by the indexing system of the invention, Figure 2 to 6 are schematic representations showing a five lobe rolor engaged in a six lobe annulus of the pump of Figure 1, illustrating five different relative angular positions between the two rotor pan, Figure 7 is a schematic view of a rotor indexing control sYstem for the pump of Figure 1, in a first operative position resulting in no indexing between the rotors, and Figure 8 is a second schematic view of the rotor indexing control system oIF'igure 7, in a second operative position resulting in maximum indexing between the rotors.

Referring to Figure 1, a variable output pump assembly 10 comprises a body or casing 11 and two, axially arranged, rotors 12, 14 located within an annulus 16. Each of' the rotors l2 14 has five lobes and the annulus 16 has six lobes. The rotor split ratio is 50150, i.e. the first rotor is the same width as the second rotor. The second rotor 14 is indexed with respect to the first rotor] 2, as discussed below.

The pump body 11 defines an inlet fluid port IS and an outlet fluid port 20. The two ports are generally symmetrical of the plane P-P which contains axis 40 of the rotor 12 and axis 52 of the annulus 16.

The first rotor 12 is fast with a shaft 22, which in turn is fixed to an input drive gear 24.

The shaft 22 is bushed at 26 in the pump body.

The second (indexed) rotor 14 is arranged to be driven indirectly by the rotor 12, via the annulus lb. That is to say, the input drive gear 24 turns the shaft, the shaft 22 turns the first rotor 12, the first rotor 12 turns the aimulus 16, and the annul us 16 turns the second rotor 14. The second rotor 14 is bushed at 28 on eccentric 30 carried on shall 32. The bushes are preferable hut not essential. The shaft 32 is arranged on axis A. which is concentric with the annulus 16.

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The shaft 32, carrying the second rotor 14, is also fast with a pinion 64. The pinion 64 is meshed with a rack 66, operation of which is described in the Applicant's European Patent No. 0565340, and in detail below, in order to allow rotational indexing of the second rotor 1 4 with respect to the first rotor 12, l0 By way of background, Figures 2 to 6 shows different relative positions of the rotors caused by indexing the second rotor 14 with respect to the first rotor 12.

In particular, Figure 2 shows the zero position in which the two rotor parts U, 14 are phase synchronised, i.e. both rotating about axis 40. The rotor lobe which is symmetrically arranged relative to the plane P-P is fully engaged with an annulus inrerlobe space and the maximum diameter chamber is diametrically opposite, i.e. as indicated by the reference numeral 42. Assuming rotation in the direction of the arrow R in Figure 2, the smallest chamber 44 overlaps one end of the inlet port 18 and the next largest chamber 46 overlaps the other end of the inlet port. Similarly chambers 48, which arc generally opposite to chambers 44 46 overlap the outlet port 20. Figure 1 shows the pump set for maximum pumping activity.

Figure 3 shows the situation when the two rotor parts have been shifted so as to be 45 degrees out of phase. Rotor 12 is still on axis 40 but rotor 14 is on axis 54 which is now spaced from axis 40 and also from axis 52 which is that of the annulus. Each chamber may now be considered to be divided into two axially arranged i.e. end-to-end portions (which necessarily communicate with one another) hut the portion composed of the space radially located between rotor 12 and annulus 16 is as in Figure 1, but that between rotor 14 and the annulus 16 is phase shifted so that effectively over the area of the inlet port it is smaller, but over the area of the outlet port is larger.

Figure 4 shows the phase shift carried on so that the axis of the rotor part 14 is now shown by the reference 54 and is 90 degrees removed from the plane P-P about the point 52. In this position, the minimum volume chamber for rotor 12 has shifted to be wholly located within the inlet port whereas two equal large volume chambers are both substantially aligned with the outlet port.

Figure 5 shows 135 degree phase shift.

Figure 6 shows 180 degree phase shift. In this case, the maximum volume chamber for the rotor 12 is angularly aligned with the minimum volume chambers for the rotor 14 and the total effect is a zero pumping action if the rotor split ratio is 50/50. The roior split ratio can be varied accordingly, and if the rotor split ratio is anything other than 50:50, the flow would be at a minimum.

In accordance with the invention, arid referring to Figure 7, the rack 66 is conveniently integral with a piston rod 68 carried by a piston 70 which is slidably mounted in a cylinder 72. Fluid can be supplied to one side or the other of the piston 70 to effect slidahie movement thereof in the cylinder 72.

The movement of the piston rod 68/rack 66 is effected by a shuffle valve 74.

The variable output pump assembly 10 supplies an I C engine. A low pressure oil source (LPO) from the main lubricant gallery/rifle of the I.C. engine is in fluid communication with the shuttle valve 74, via a pipe 76. [he shuttle valve 74 is arranged to be acted on by the low pressure oil LPO from the main lubricant gallery/rifle. The shuttle valve 74 comprises a spool 78 arranged in a cylindrical housing 79. The spool 78 takes the form of a cylindrical rod havIng first, second and third annular shoulders 86, 88, 90 spaced along the length of the cylindrical rod, and defining cavities between successive pairs of shoulders. The diameter of the shoulders 86, 88, 90 equates to the diameter of the cylindrical housing 79. A straight helical compression spring 80 is arranged between the third shoulder 90 of the spool 78 and one end of the housing 79, thereby restricting movement of the spool 78 and biasing the spool towards the seat 81 at the opposite end of the housing 79.

In use, the spool 78 is arranged such that pressure is communicated Via the pipe 76 and can act upon the spool 78. Since the movement of the spool 78 is resisted by the spring 80, below a certain gallery pressure, for example about four bar, the first shoulder of the spool valve 781s seated against seat 81. The spool 78 is positioned in such a way that the space between the second and third shoulders 88, 90 allows fluid communjcalin between a high pressure oil source (J-JPO) from the pump outlet, and a passage 82 which communicates with a first (left) side of the piston 70, shown in Figure 7. High pressure oil (F1PC)) from the pump outlet flows through radial ports in the spool 78 arid S via the passage 82 to act upon the piston 70, forcing the piston 68 towards a maximum displacement position, thereby displacing the rack 66 and turning the pinion 64, so that the rotor 14 is (eventually) n t indexed, it should be noted that the pressure at the pump outlet is at a maximum, whereas elsewhere in the system the pressure is reduced as a result of the pressure drops that occur at obstacles such as coolers and filters etc. The second shoulder 88 moves to a position in which it closes off port F]. The third shoulder 90 moves to a position in which port E2 is open, allowing exhaust of fluid.The pressure for VOP actuation is measured at the main lubricant gallery/rifle. When the pressure is sufficient to displace the spool 78 against the spring 80, for example about four bar, fluid is allowed to flow from a high pressure oil source (HPO) from the pump 1 5 outlet to the space between the second and third shoulders 88, 90, and to a passage 84 which communicates with a second (right) side of thc piston 70, best shown in Figure 8.

Fluid flows through the line 84 to reverse the direction of movement of' the piston 68.

The piston 68 is forced towards a minimum displacement position, thereby displacing the rack 66 and turning the pinion 64, so that the rotor 14 is (evenmally) fully indexed, The gallery, or rifle, is the preferred position to sense pressure for actuation of the mechanism because of it's close proximity to the bearings, and therefore indicates more accurately the conditions at the bearings themselves. Sensing pressure for actuation anywhere else in the system results in a less accurate assessment of the conditions at the bearings. The first and second shoulders 86, 88 meanwhile move to a position which leaves open port E allowing exhaust of fluid. The third shoulder 90 moves to a position in which port E2 is closed.

By selection of the spring relative to the oil pressure involved, the J)Wflp can be automatically turned between minimum and maximum positions and adjusted to required positions thcrehetween.

LJtiiising internal pump pressure for actuation of the indexing mechanism yields most advantages and maximises power savings.

With this arrangement an accurate measurement of pressure at the bearings can be obtained, whilst the maximum system pressure from within the pump enables the internal pump mechanism to operate efficiently.

1 5 Utilising the higher pump internal pressure also means that the actuating mechanism can be reduced in size, thus resulting in a more compact pump.

The rotor indexing control invention can be applied to other suitable pumps.

Claims

CLAIMS

I. A variable output pump assembly comprising a pump, rotor indexing means, and a sensor, wherein the sensor is in fluid communication with an engine gallery or vicinity thereof, the SOnsor is arranged to sense pressure at a position in the engine lubrication circuit remote from the pump outlet, and the rotor indexing means is in communication with the pump outlet, enabling fluid from the pump outlet to cause actuation of the rotor indexing means.

2. A variable output pump assembly comprising a pump7 rotor indexing means, and a sensor, wherein the sensor is in fluid communication with an engine gallery or vicinity thereof! the sensor is arranged to sense pressure in the engine gallery or vicinity thereof, and the rotor indexing means being in communication with the pump outlet enabling fluid from the pump outlet to cause actuation of the rotor indexing means.

3. A variable output pump assembly according to claim I or 2, wherein the assembly is arranged so that when a pressure less than a predetermined pressure is sensed by the sensor, the rotor indexing means is actuated so as to move the first rotor in a first direction with respect to the second rotor.

4. A variable output pump assembly according to claim 1,2, or 3, wherein the assembly is arranged so that when a pressure greater than a predetermined pressure is sensed by the sensor, the rotor indexing means is actuated so as to move a first rotor in a second direction with respect to the second rotor.

5. A variable output pump assembly according to any preceding claim, wherein the sensor comprises a valve assembly which moves at the pre determined pressure.

6. A variable output pump assembly according to claim 5, wherein valve assembly is arranged so that its movement enables actuation of the rotor indexing means.

7. A variable output pump assembly according to Claim 6, wherein the assembly is arranged so that when a pressure less than a predetermined pressure is sensed, fluid from the engine gallery does not move the valve assembly, and the pump outlet is in fluid communication with the indexing means allowing movement of the indexing means in a first direction.

8. A variable output pump assembly according to Claim 6 or 7, wherein the assei-nbly is arranged so that when a pressure greater than a predetermined pressure is sensed, fluid from the engine gallery moves the valve assembly, and the pump outlet is in fluid communication with the indexing means allowing movemcnt of the indexing means in a second direction.

9. A variable output pump assembly according to any one or in ore of Claims 5 to 8. wherein the valve assembly comprises a spool valve.

10. A variable output pump assembly according to Claim 9, wherein the assembly is arranged so that when a pressure less than a predetermined pressure is sensed, fluid from the engine gallery does not move the spool valve, and the pump outlet is in fluid communication with the indexing means through the spool valve allowing movement of the indexing means in a first direction.

11. A variable output pump assembly according to Claim 9, wherein the assembly is arranged so that when a pressure greater than a predetermined pressure is sensed, fluid from the engine gallery moves the spool valve, and the pump outlet is in fluid communication with the indexing means through the spool valve allowing movement of the indexing means in a second direction.

12. A variable output pump assembly according to Claims 9 to 11, wherein the spool valve also comprises an exhaust fluid outlet.

13. A variable output pump assembly according to any preceding claim, wherein the predetermined pressure is the gallery pressure at art engine speed corresponding to between 500 and 1000 rpm.

14. A variable output pump assembly according to any preceding claim, wherein the predetermined pressure is the gallery pressure at an engine speed corresponding to between 1000 and 2000 rpm.

15. A variable output pump assembly according to any preceding claim, wherein the assembly is arranged so that at a predetermined pressure of between 3 and 5 bar, the rotor indexing means is actuated, prefcraby about 4 bar.

16. A variable output pump assembly according to any preceding claim, wherein the first rotor is movable rotationally with respect to the second rotor, and the indexing means is arranged to rotaie the first rotor with respect to the second rotor 17. A variable output pump assembly substantially as described herein and with reference to the accompanying drawings.

18. A method of indexing a first rotor with respect to a second rotor in a variable output pump, the method comprising the steps of sensing pressure at a position in an engine lubrication circuit remote from the pump outlet, and using the pump outlet pressure of the pump to effect indexing of the first rotor with respect to the second rotor.

19. A method of indexing a first rotor with respect to a second rotor in a variable output pump, the method comprising the steps of sensing the gallery pressure of the engine or in the vicinity of the gallery, and using the pump outlet pressure of the pump to effect indexing of the first rotor with respect to the second rotor.

20. A method of indexing according to claim 18 or 19, wherein the method comprises, when a pressure less than a predetermined pressure is sensed by the sensor, actuating the rotor indexing means so as to move the first rotor in a first direction with respect to the second rotor, 21. A method of indexing according to claim 18719, or 20, wherein the method comprises, when a pressure greater than a predetermined pressure is sensed by the sensor, actuating the rotor indexing means so as to move the first rotor in a second direction with respect to the second rotor.

22. A method of indexing according to one or more of Claims 18 to 21, wherein the method comprises arranging a spool valve to sense the pressure.

23. A method of indexing according to Claim 22, wherein the method comprises, when a pressure less than a predetermined pressure is sensed, not moving the spool valve with fluid from the engine gallery, and alTanging the pump outlet in fluid communication with the indexing means through the spooi valve allowing movement of the indexing means in a first direction.

24. A method of indexing according to Claim 22 or 23, wherein the method comprises, when a pressure greater than a predetermined pressure is sensed, moving the spool valve with Quid from the engine gallery, and arranging the pump outlet in fluid communication with the indexing means through the spool valve allowing movement of the indexing means in a second direction.

25. A method of indexing a first rotor with respect to a second rotor in a variable output pump, substantially as described herein and with refcrcnce to the accompanying drawings.

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