HIGH PRESSURE PUMP

Abstract

A high pressure pump including a pump body, a pump housing within which at least part of the pump body is located, a gallery defined between the pump body and the pump housing, the pump body having a pump outlet which communicates with the gallery, and the pump housing having an outlet port which communicates with the gallery, and a filler located within the gallery, the filler being located at least in the part of the gallery most remote from the pump outlet.

Description

This invention relates to a high pressure pump, and in particular to a high pressure pump for use in the supply of oil to a generator.

EP1486675 describes an electrical generator for use in aerospace applications. In order to provide lubrication for the bearings of the generator, and to provide cooling for the generator, a high pressure oil pump is provided. The high pressure pump takes the form of a two stage pump including a first stage in the form of a centrifugal pump whereby oil is drawn from a reservoir and delivered to a second stage in the form of a gerotor pump. The gerotor pump delivers oil under high pressure to a manifold of the generator from which it is supplied for the aforementioned cooling and lubrication purposes.

In practice, the second stage may comprise two gerotor pumps arranged in series with one another so as to raise the oil pressure still further.

The pump includes a pump body located within a pump housing. The pump body and/or housing are shaped so as to define, therebetween, an annular gallery with which the outlet of the second stage communicates, the annular gallery communicating with an outlet port provided in the pump housing and from which the oil is delivered under high pressure to the manifold.

The nature of a gerotor pump is such that pressure pulses develop at the outlet thereof. It has been found that erosion occurs in the part of the annular gallery furthest from the outlet of the second stage of the pump. This erosion can result in damage to the pump body and/or the pump housing, and/or to seals located therebetween at this point, resulting in the escape of oil therefrom. As a result, the rate of delivery of oil by the pump, and the pressure at which the oil is delivered may reduce. Reductions in the rate of oil delivery or pressure at which the oil is delivered may result in insufficient cooling of the generator and/or in insufficient lubrication of the bearings thereof. Clearly, this is undesirable as damage to the generator may occur. Furthermore, as the generator will typically incorporate sensors to detect the oil pressure and the temperature of the generator, and a control system which controls the operation of the generator using the outputs of such sensors, the control system may cause the generator to be shut down as a result of insufficient oil being delivered.

It is an object of the invention to provide a high pressure pump in which at least some of the disadvantages set out hereinbefore are overcome or are of reduce effect.

According to the present invention there is provided a high pressure pump comprising a pump body, a pump housing within which at least part of the pump body is located, a gallery defined between the pump body and the pump housing, the pump body having a pump outlet which communicates with the gallery, and the pump housing having an outlet port which communicates with the gallery, and a filler located within the gallery, the filler being located at least in the part of the gallery most remote from the pump outlet.

The gallery is conveniently of annular form. The filler preferably extends about at least half of the circumferential length of the gallery. Conveniently, it extends about at least three quarters of the gallery. The cross-sectional shape of the filler conveniently conforms with that of the gallery. Consequently, the filler substantially fills at least the part of the gallery furthest from the pump outlet.

The filler is conveniently of an elastomeric material. For example, it may be of moulded fluorocarbon form. The filler preferably forms an interference fit in the gallery.

Locator means are preferably provided to resist movement of the filler within the gallery. The locator means may comprises locator pins provided in the gallery and arranged to abut the ends of the filler to resist movement of the filler. The filler may incorporate an integral projection adapted to be received within a corresponding recess formed in the pump body and/or pump housing to resist movement of the filler.

Adjacent the gallery, the pump body and pump housing are preferably sealed to one another, for example by the use of o-ring seals.

The high pressure pump conveniently incorporates at least one gerotor pump.

It is thought that in the known high pressure pump, the erosion and wear which occurs results from cavitation erosion caused by pressure spikes or ripples being transmitted from the pump outlet around the gallery in both directions. By providing the filler, the contact with and/or the quantity of oil within the part of the gallery most remote from the pump outlet and so most susceptible to such cavitation erosion is reduced, and as a consequence, the occurrence of such erosion is reduced. Furthermore, by the use of an elastomeric material for the filler, it may be possible to partially absorb the pressure spikes and so reduce the occurrence of cavitation erosion.

The invention will further be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a sectional view illustrating a high pressure pump in accordance with an embodiment of the invention;

FIG. 2 is a diagram illustrating part of the pump of FIG. 1;

FIG. 3 is a perspective view illustrating part of the pump of FIG. 1;

FIG. 4 is a view illustrating another part of the pump; and

FIG. 5 is a view illustrating a modification.

Referring firstly to FIGS. 1 and 2, a high pressure pump is illustrated, the pump being intended for use in the supply of oil to a generator for lubrication and cooling purposes. Whilst described in connection with a pump for such use, it will be appreciated that the invention is not restricted in this regard and may be used in other applications.

The pump comprises a pump body 10 of generally stepped cylindrical shape and through which a drive shaft 12 extends. The drive shaft 12 carries, at one end thereof, the rotor 14 of a centrifugal pump 16, operation of the centrifugal pump 16 serving to draw oil from a sump (not shown) along an inlet pipe 18, delivering the oil to a sump 20 located within a pump housing 22. The pump body 10 is located, at least in part, within the pump housing 22 and is secured thereto against movement, in use.

The pump body 10 houses a gerotor type pump 24 having a pump inlet 25 communicating, in use, with the sump 20, and a pump outlet 26, the gerotor type pump 24 serving to deliver oil supplied thereto, from the sump 20, to the pump outlet 26 at high pressure.

The pump body 10 defines, on its outer periphery, and annular recess 28 which, together with the pump housing 22, forms an annular gallery 30. As shown in FIG. 2, the pump outlet 26 communicates with the annular gallery 30, thus the output from the gerotor pump 24 is supplied to the annular gallery 30.

As shown in FIG. 1, the pump housing 22 includes an outlet port 32 which communicates, via an outlet passage 34, with the annular gallery 30. Accordingly, operation of the gerotor pump serves to deliver oil at high pressure to the outlet port 32 from where it may be delivered via a manifold or the like, if desired, to an associated electrical generator for lubrication and/or cooling purposes.

The pump outlet 26 is substantially aligned with the point at which the outlet passage 34 opens into the annular gallery 30, in use.

Adjacent the annular gallery 30, the pump body 10 is provided with annular grooves in which o-ring seals 36, 38 are provided, the o-ring seals bearing against the pump housing 22 to form seals therewith and so resist the escape of oil from the annular gallery 30 either back towards the sump 20 or out of the pump and into the interior of the generator in an uncontrolled manner.

A gerotor pump produces pressure ripples or spikes at its outlet, in use. As mentioned hereinbefore, it has been found that increased levels of wear are experienced in the part of the annular gallery 30 furthest from the pump outlet 26. This wear can result in damage to the pump housing and/or body with which the seals engage and/or in damage to the o-ring seals 36, 38 at or close to this location, reducing the effectiveness of the seals. The damage to the seals or sealing effect can result in the escape of oil from the pump, or in the return of oil to the sump 20, reducing the rate at which oil is delivered to the outlet port 32 and/or the pressure at which oil is delivered. This can give rise to increased wear and/or overheating of the generator, or may result in the generator being switched off by its associated controller as a result of insufficient oil pressure being detected. It is thought that the increased levels of wear arising at the part of the annular gallery most remote from the pump outlet 26 are caused by cavitation erosion. It is thought that the pressure ripples or spikes are transmitted in both directions around the annular gallery from the pump outlet 26, and so the pressure fluctuations experienced at the point furthest from the pump outlet 26 are significantly greater than those experienced elsewhere. The range of pressures experienced at this location are approximately twice those experienced elsewhere. Cavitation erosion is thus thought to be most significant at the point most remote from the pump outlet 26, and this is thought to be the cause of the accelerated wear at this location.

In accordance with this embodiment of the invention, as shown in FIGS. 1 and 3, a filler element 40 is located within the annular gallery 30. The filler element 40 cannot extend about the entire circumference of the annular gallery 30 as this would prevent or restrict the flow of oil between the pump outlet 26 and the outlet passage 34. Rather, therefore, the filler element 40 extends around only part of the circumferential length of the gallery 30. The part of the gallery 30 in which the filler element 40 is located includes the part thereof furthest from the pump outlet 26. However, the filler element 40 is conveniently long enough that it extends about at least half of the circumferential length of the annular gallery 30. Preferably, it extends about considerably more of the annular gallery 30 than this. By way of example, in the illustrated embodiment, the filler element 40 extends around about three quarters of the annular gallery 30.

The dimensions of the filler element 40 are conveniently such that the filler element 40 substantially fills the relevant parts of the annular gallery 30, leaving little if any space available to accommodate oil. Preferably the filler element 40 is an interference fit within the annular gallery 30.

It is thought that by substantially filling the relevant parts of the annular gallery 30 with the filler element 40, contact between the pressurised oil and the housing 22, and/or the transmission of pressure ripples or spikes to the part of the annular gallery 30 most remote from the pump outlet 26, is reduced or avoided, thus the occurrence of cavitation erosion at that location is avoided or significantly reduced. By avoiding such cavitation erosion, damage in the region of the o-ring seals 36, 38 and the parts providing support therefore is reduced and so the output of the pump is maintained.

The filler element 40 is preferably of an elastomeric material. As a result, not only does the filler element 40 serves to reduce the passage of oil to the part of the annular gallery 30 most remote from the pump outlet 26, but also compression and subsequent relaxation of the elastomeric material may serve to partially absorb the pressure spikes, further reducing the impact of cavitation erosion at the part of the annular gallery 30 most remote from the pump outlet 26. By way of example, the filler element 40 may be of moulded fluorocarbon form.

As the filler element 40 does not extend around the entirety of the annular gallery 30, it is important for it to be held against movement relative to the pump housing 22 and/or pump body 10 in order to ensure that the filler element 40 does not block the pump outlet 26 or outlet passage 34. In some circumstances, this may be achieved simply by virtue of the frictional forces experienced between the filler element 40 and the walls defining the annular gallery 30. However, it is desirable to provide location means serving to positively resist movement of the filler element 40.

As shown in FIG. 3, the location means may comprise a projection or boss 42 integrally formed with the filler element 40 and arranged to be received within a corresponding recess 44 formed in the pump housing 22, as shown in FIG. 4.

Alternatively, the boss 42 may be located and arranged to be received within a corresponding recess formed in the pump body 10. In each case, the boss 42 and recess 44 together serve to resist movement of the filler element 40.

An alternative location means is shown in FIG. 5. In this arrangement, locating pins 46 are fitted to the pump housing 22 or pump body 10, within the part forming the annular gallery 30, the pins 46 being arranged to abut the ends of the filler element 40, and so resist movement thereof.

It will be appreciated that these two forms of location means could be used in combination with one another, if desired.

Regardless as to the type of location means used, resisting movement of the filler element 40 ensures that the pump outlet 26 and outlet passage 34 remain unobscured and in communication with one another.

It is thought that the invention may be applied to a number of known pump designs, and may be retrofitted to existing pumps as well as incorporated into new pumps. Modifications to existing pump components to allow the incorporation of the invention are minimal.

Whilst specific embodiments of the invention are described herein, it will be appreciated that a wide range of modifications and alterations may be made thereto without departing from the scope of the invention.

Claims

1-15. (canceled)

16. A high pressure pump comprising: a pump body;a pump housing within which at least part of the pump body is located;a gallery defined between the pump body and the pump housing, the pump body having a pump outlet which communicates with the gallery, and the pump housing having an outlet port which communicates with the gallery; anda filler located within the gallery, the filler being located at least in the part of the gallery most remote from the pump outlet.

17. The pump of claim 16, wherein the gallery is of annular form.

18. The pump of claim 17, wherein the filler extends about at least half of the circumferential length of the gallery.

19. The pump of claim 18, wherein the filler extends about at least three quarters of the gallery.

20. The pump of claim 16, wherein a cross-sectional shape of the filler conforms with that of the gallery.

21. The pump of claim 16, wherein the filler substantially fills at least part of the gallery furthest from the pump outlet.

22. The pump of claim 16, wherein the filler is of an elastomeric material.

23. The pump of claim 16, wherein the filler is of molded fluorocarbon form.

24. The pump of claim 16, wherein the filler forms an interference fit in the gallery.

25. The pump of claim 16, further comprising locator means to resist movement of the filler within the gallery.

26. The pump of claim 25, wherein the locator means comprises locator pins provided in the gallery and arranged to abut ends of the filler to resist movement of the filler.

27. The pump of claim 16, wherein the filler incorporates an integral projection configured to be received within a corresponding recess formed in the pump body and/or pump housing to resist movement of the filler.

28. The pump of claim 16, wherein adjacent the gallery, the pump body and pump housing are sealed to one another.

29. The pump of claim 28, wherein adjacent the gallery, the pump body and pump housing are sealed to one another by o-ring seals.

30. The pump of claim 16, further comprising at least one gerotor pump.