GB2401487A

GB2401487A - An electrically driven fluid pump assembly

Info

Publication number: GB2401487A
Application number: GB0310513A
Authority: GB
Inventors: Michael John Werson
Original assignee: Automotive Motion Technology Ltd
Current assignee: Automotive Motion Technology Ltd
Priority date: 2003-05-08
Filing date: 2003-05-08
Publication date: 2004-11-10
Also published as: GB0310513D0

Abstract

An electrically driven fluid pump assembly 10 includes a fluid pump 11 and an electric motor 15, the motor 15 including a stator 16 and a rotor 17, the rotor 17 including an output member 18 which drives a pumping member of the pump 11 to pump the fluid, and the assembly 10 including an electronic control unit 20 for controlling the motor 15, there being a path for pumped fluid from a high pressure fluid region 33 to a low pressure fluid region 34, at least part of the fluid path being through the stator 16 and along one side 27 of a dividing wall 21 which separates the fluid from the electronic control unit 20 which is provided on the other side of the dividing wall 21, to cool the motor 15 and the unit 20, and there being a gap 28 between the stator 16 and the rotor 17, the cooling fluid flowing along the fluid path without being fed into the gap 28.

Description

Title: Improvements in or Relating to Pumps

Description of Invention

This invention relates to an electrically driven fluid pump assembly including a fluid pump and an electric motor, the motor including a stator and a rotor, the rotor including an output member which drives a pumping member of the pump to pump the fluid, and the assembly including an electronic control unit for controlling the motor.

lo It has already been proposed to use the pumped fluid to cool the motor and the electronic control unit, by allowing fluid to flow from a high pressure region, e.g. an output port of the pump, through one or more passages through the stator, into heat exchange with a wall separating the fluid from the electronic control unit, and thence through a gap between the rotor and the Is stator, to a low pressure region, e.g. the inlet port of the pump.

For a low viscosity fluid, such as a water based fluid, providing motor cooling in this way results in only low viscous losses due to the fluid flowing through the gap between the rotor and the stator. However for more viscous fluids, such as for example only, steering fluid for moving an actuator in an automotive application, particularly where such fluids are at relatively low temperatures at which they are their most viscous, viscous losses as the fluid flows through the gap, are unacceptably large. Thus motor cooling where such viscous fluids have been pumped has tended to be achieved in a different way.

According to one aspect of the invention we provide an electrically driven fluid pump assembly including a fluid pump and an electric motor, the motor including a stator and a rotor, the rotor including an output member which drives a pumping member of the pump to pump the fluid, and the assembly including an electronic control unit for controlling the motor, Were being a path for pumped fluid from a high pressure fluid region to a low pressure fluid region, at least part of the fluid path being through the stator and along one side of a dividing wall which separates the fluid from the electronic control unit which is provided on the other side of the dividing wall, to cool the I motor and the unit, and there being a gap between the stator and the rotor, the cooling fluid flowing along the fluid path without being fed into the gap.

Thus in an assembly in accordance with the invention, viscous losses caused by low temperature fluid in the gap between the stator and the motor are reduced as either the gap may be an air gap which is isolated from the pumped fluid, or where the assembly is of the kind in which the motor is immersed in lo fluid with there being stagnant fluid in the gap, the temperature of the stagnant fluid may rapidly rise as viscous losses are dissipated into the fluid in the gap, the warmed fluid thus resulting in reduced viscous losses.

In one embodiment of the invention the fluid path in the assembly from the high pressure fluid region, is first through one or more passages in the stator, then along the one side of the dividing wall, and then through one or more further passages which direct the fluid to the low pressure region. In this example, the passage or passages from the high pressure region to the one side of the dividing wall may extend generally parallel to an axis about which the rotor in use, rotates. The further passage or passages from the one side of the to dividing wall to the low pressure region may also extend generally parallel to the axis.

In another example the fluid flow path in the assembly from the high pressure fluid region is first along the one side of the dividing wall, and then through one or more passages, which may extend generally parallel to the axis about which the rotor rotates, which passage or passages direct the fluid to the low pressure region.

In each case, the fluid may flow generally transversely, e.g. radially, to; the axis along the one side of the dividing wall.

The dividing wall may be an end wall of the motor, located at an axial end of the rotor remote from the fluid pump.

The invention is particularly but not exclusively applicable where the motor is a brushless motor such as a permanent magnet brushless motor, in s which case the electronic control unit may be operable to energise and de- energise poles of the stator to cause the rotor to rotate, preferably within the stator.

According to a second aspect of the invention we provide a motor for use in a pump assembly in accordance with the first aspect of the invention.

lo Embodiments of the invention will now be described with reference to the accompanying drawings in which: FIGURE 1 is an illustrative cross sectional view through part of an assembly in accordance with the invention, FIGURE 2 is a view similar to that of figure 1 but showing an alternative embodiment.

Referring to figure 1 a pump assembly 10 includes a fluid pump 11 which has a pumping member 12, which may be but not exclusively a screw or _ gear pumping member which interacts with one or more outer pumping members to pump fluid from a low pressure source such a reservoir, to a high to pressure port, from where the fluid may be used to operate an actuator e.g. in an automotive application.

The assembly 10 further includes an electric motor 15, the motor 15 including a stator 16 and a rotor 17, the rotor 17 including an output member 18 i.e. a driven shaft in this example, which drives the pumping member of the :5 pump 11 to pump the fluid.

In this example, the motor 15 is a brushless motor in which the rotor 17 includes a plurality of coils 19 or magnets whilst the stator 16 includes a plurality of poles which are sequentially energised and de-energised to cause the rotor 17 to rotate about an axis A. Thus the motor 15 is operated and controlled by an electronic control unit 20 which is incorporated within the! assembly 10 but separated from the motor by a dividing wall 21 which is located adjacent an axial end 22 of the rotor 17 remote from the pump 11 and provides an end wall of the motor 15. The rotor 17 is journalled in front and s rear bearings 24, 25 in this example, and there is a gap 28 between the rotor and the stator 16.

In accordance with the invention there is provided a path for pumped fluid through which the fluid flows to cool the motor 15. The path includes a plurality of passages 30 which extend generally parallel to the axis of rotation A lo of the rotor 17, through the stator 16 to cool the stator, along one side 29 of the dividing wall 21, and then into one or a plurality of further passages 32, which also extend generally parallel to the rotor axis A. The passages 30 are connected to a high pressure fluid region 33. In one example, this region 33 may be the return flow from a hydraulic system, an Is outlet chamber from the pump 11, or a conduit or the like into which high pressure pumped fluid passes from the pump 11.

The further passages 32 are connected to a low pressure fluid region 34 which may be an inlet chamber to the pump 11, a conduit to the inlet chamber, or a reservoir from where fluid is drawn to the pump 11. ! to In each case it is the pumped fluid which flows through the passages 30, along the one side 29 of the dividing wall 21, and thence along the further passages 32, to cool the motor 15. Moreover, by virtue of the electronic control unit 20 being located on the opposite side of the dividing wall 21 to the flowing fluid, the electronic control unit 20 too will be cooled by the pumped fluid.

Is Preferably the electronic control unit 20 is mounted on the dividing wall 21 as indicated in the figures.

It can be seen that there is a closure plate 38 at rear axial end 22 of the rotor 17, spaced from the dividing wall 21 but generally parallel to the dividing i wall 21 so that there is space 39 for fluid flow between the closure plate 38 and the dividing wall 21 through which the fluid may flow generally transversely of the axis A along the one side 29 if the dividing wall 21. The closure plate 38 isolates the rotor 17 and importantly the gap 28 between the rotor 17 and the stator 16, from the fluid path.

In one embodiment, the gap 28 between the rotor 17 and the stator 16 is dry, i.e. is an air gap. Thus the returning fluid from the space 39 does not enter the gap 28, and there are no viscous losses attributable to the cooling fluid in the fluid flow path.

However, in another embodiment, the motor 15 may be of the kind lo which is immersed in fluid in which case the gap 28 may be filled with fluid.

However as the gap 28 is isolated from the fluid flow path by the closure plate 38, the fluid in the gap 28 is stagnant by which we mean that the fluid is not replaced or exchanged with flowing fluid in the flow path. Thus upon initial operation of the motor 15, the stagnant fluid will rapidly become heated as Is energy is dissipated into the stagnant fluid due to viscous losses occurring as the rotor 17 rotates. Thus after initial start-up as the fluid is heated, the viscous losses will reduce to an acceptable level as the viscosity of the fluid in the gap 2 reduces as its temperature increases.

Referring to figure 2, a similar pump assembly 10 to that shown in figure to 1 is shown and accordingly similar parts are labelled with the same references.

In this embodiment, the fluid path for the cooling fluid is first though the space 39 between the closure plate 38 and the dividing wall 21, from a high pressure fluid region 33, e.g. the high pressure return of the pump 11, and then through passages 32 through the stator 16, to a low pressure region 34. In this :5 embodiment, the motor 15 is perhaps cooled less efficiently than the motor 15 in the figure 1 embodiment, but the dividing wall 21, and hence the electronic conko1 unit 20 is cooled more efficiently as the cooling pumped fluid from the high pressure region is first fed in to the space 39 between the closure plate 38 and the dividing wall 21, rather than first passing through passages 30 in the hot stator 16.

In the embodiment shown in figure 2, the motor 15 may be of the kind in which there is an air gap 28 between the stator 16 and rotor 17, or an immersed motor 15 with stagnant fluid in the gap 28.

It will be appreciated that in both the figure 1 and figure 2 arrangements, where there is stagnant fluid in the gap 28, by virtue of the rotational movement of the rotor 17, some fluid may pass into and out of the gap 28, for example to and from a low pressure region such as a reservoir in which the pump assembly lo 10 may be immersed, but pumped fluid from the fluid flow path for cooling, and particularly fluid from the high pressure region 33, will not be fed into the gap 28 and consequently, the fluid in the gap 28 will not be substantially cooled but rather, heated due to heat dissipated by viscous losses, as described above.

Various modifications may be made without departing from the scope of the invention.

For example, although the examples of the invention given relate to pump assemblies 10 with brushless permanent magnet motors 15, the invention may be applied to other kinds of motors, e.g. switched reluctance motors. The application of the invention to any particular kind of pump 11 is only exemplary! to and the invention may be applied to any kind of pump which is driven from an electric motor such as the motors indicated at 15 in the figures.

In the examples shown and described, the rotor 17 is located internally of the stator 16, but in another example may be located exteriorly of the stator 16.

:5 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 i l combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. An electrically driven fluid pump assembly including a fluid pump and an electric motor, the motor including a stator and a rotor, the rotor including an output member which drives a pumping member of the pump to pump the fluid, and the assembly including an electronic control unit for controlling the motor, there being a path for pumped fluid from a high pressure fluid region to a low pressure fluid region, at least part of the fluid path being through the stator and along one side of a dividing wall which separates the fluid from the electronic lo control unit which is provided on the other side of the dividing wall, to cool the motor and the unit, and there being a gap between the stator and the rotor, the cooling fluid flowing along the fluid path without being fed into the gap.

2. An assembly according to claim 1 wherein the gap is an air gap which is isolated from the pumped fluid.

3. An assembly according to claim 1 wherein the motor is immersed in fluid, with there being stagnant fluid in the gap.

4. An assembly according to any one of claims 1 to 3 wherein the fluid path; in the assembly from the high pressure fluid region, is first through one or more passages in the stator, then along the one side of the dividing wall, and then through one or more further passages which direct the fluid to the low pressure region.

5. An assembly according to claim 4 wherein the passage or passages from the high pressure region to the one side of the dividing wall extend generally parallel to an axis about which the rotor in use, rotates. i

6. An assembly according to claim 4 or claim 5 wherein the further passage or passages from the one side of the dividing wall to the low pressure region extend generally parallel to the axis.

7. An assembly according to any one of claims 1 to 3 wherein the fluid flow path in the assembly from the high pressure fluid region is first along the one side of the dividing wall, and then through one or more passages which direct the fluid to the low pressure region. i s

8. An assembly according to claim 7 wherein the passages extend generally parallel to the axis about which the rotor rotates.

9. An assembly according to any one of the preceding claims wherein the fluid flows generally transversely to the axis along the one side of the dividing wall.

10. AN assembly according to any one of the preceding claims wherein the dividing wall is an end wall of the motor, located at an axial end of the rotor remote from the fluid pump.

11. An assembly according to any one of the preceding claims wherein the motor is a brushless motor, the electronic control unit being operable to energise and de-energise poles of the stator to cause the rotor to rotate. 2s

12. An assembly according to any one of the preceding claims wherein the i rotor rotates within the stator.

13. An electrically driven fluid pump assembly substantially as hereinbefore described with reference to and/or as shown in figure 1 or figure 2 of the accompanying drawings.

14. A motor for use in a pump assembly in accordance with any one of the preceding claims.

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