GB2545427A

GB2545427A - A bearing arrangement in an electric supercharger

Info

Publication number: GB2545427A
Application number: GB1522007.2A
Authority: GB
Inventors: Knight Stephen
Original assignee: Valeo Air Management UK Ltd
Current assignee: Valeo Air Management UK Ltd
Priority date: 2015-12-14
Filing date: 2015-12-14
Publication date: 2017-06-21
Anticipated expiration: 2035-12-14
Also published as: GB201522007D0; WO2017102377A1; GB2545427B

Abstract

An electric supercharger 1 comprises an electric motor 2, a compressor wheel 3 rotatable on a drive-shaft arranged to be driven by the electric motor, a first bearing 41 arranged to support the drive shaft at a first axial location; and a second bearing 42 arranged to support the drive shaft at a second axial location, and where the first and second locations are axially spaced apart from each other and are both located upstream of the motor such that the motor is in an overhung configuration. The drive shaft may be supported by the first and second bearings only, and the first and second bearings may be housed in a cartridge so that they may both be simultaneously installed in the supercharger. There may be a position indicator to indicate the rotational position of the drive shaft, and the electric motor may be a switched reluctance motor or a permanent magnet motor. Also claimed is a kit of parts for forming such a supercharger, where the first and second bearings are housed in a cartridge for simultaneous installation.

Description

A BEARING ARRANGEMENT IN AN ELECTRIC SUPERCHARGER FIELD OF THE INVENTION

The present invention relates to the arrangement of bearings in an electric supercharger. More particularly, but not exclusively, the present invention relates to an electric supercharger having first and second bearings located upstream of the electric motor of the supercharger.

BACKGROUND

Electric superchargers are known per se and have been disclosed, for example in WO 2014/096786 and GB2516060. A previously-suggested electric supercharger is shown in Figure 1. The supercharger 100 comprises a switched reluctance motor 101, arranged to rotate a compressor wheel 103 that is fixedly mounted on the drive shaft 105 associated with the motor 101. The supercharger 100 comprises two radial bearings 107a, 107b arranged to support the drive shaft 105. The first bearing 107a is located upstream of the motor (i.e. in front of the motor 101 (but behind the compressor wheel 103). The second bearing 107b is located downstream of the motor (i.e. behind the motor 103). Such an arrangement enables the driveshaft 105 to be supported and for radial loads to be reacted into the supercharger housing 109.

It may be desirable to provide an alternative layout of components in the supercharger. For example, this may be desirable in order to re-shape the supercharger to take into account, or to facilitate, different engine bay packaging layouts .

The supercharger in Figure 1 may also be relatively time consuming to assemble. It may be desirable to provide a way of more efficiently assembling an electric supercharger.

The present invention seeks to reduce or mitigate at least some of the above-mentioned disadvantages.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided an electric supercharger comprising: an electric motor, a compressor wheel rotatable on a drive-shaft arranged to be driven by the electric motor; a first bearing arranged to support the drive shaft at a first axial location; a second bearing arranged to support the drive shaft at a second axial location; wherein the first and second locations are axially spaced apart from each other and are both located upstream of the motor, such that the motor is in an overhung configuration.

Locating both bearings upstream of the motor, such that the motor is in an overhung configuration, enables the internal layout of the supercharger to be re-arranged. For example, the motor may be moved relatively further back in the supercharger. The use of an overhung arrangement may also enable the motor to be a smaller diameter because the diameter of the motor is not necessarily dependent on the size and/or position, of the bearings.

The drive shaft may be supported by only the first and the second bearings. The drive shaft is preferably not supported by any bearings downstream of the motor.

The bearings may be radial bearings for supporting radial loads. Preferably both bearings circumferentially extend around the drive shaft. The bearing may be annular. The drive shaft may pass through the opening in the centre of each of the annular bearings.

The first and second bearings may be housed in a cartridge. The cartridge may be such that both the bearings may be simultaneously installed in the supercharger via installation of the cartridge. Thus, the cartridge may be a unit comprising both bearings. The cartridge may be held in the supercharger by way of a screw-threaded fitting. Having the bearings in a cartridge has been found to be beneficial because it may facilitate relatively straightforward and efficient assembly of the supercharger. The overhung arrangement enables the use of a cartridge because there is no need to have a motor located between the two bearings.

In some embodiments of the invention, the drive shaft may also extend downstream of the motor. The drive shaft may extend further upstream, than it does downstream, of the motor (in other words, the motor is preferably towards the rear of the drive shaft). A position indicator (for example a magnetic ring indicator) may be located on the downstream end of the drive shaft. The position indicator may be for sensing the rotational position of the drive shaft. For example the indicator may be a magnetic ring indicator having magnetic regions of alternating polarity. The supercharger may comprise a sensor for sensing the position indicator. For example the supercharger may comprise a Hall-effect sensor for sensing the regions of alternating polarity of a magnetic ring indicator as the drive shaft rotates.

The motor may comprise a stator. The motor may comprise a rotor. The rotor or stator may comprise a plurality of coils.

The electric motor may be a Switched Reluctance Motor (SRM). The electric motor may be a permanent magnet motor.

The supercharger may comprise a control unit for controlling the motor. The control unit may control current to the motor. For example, the control unit may selectively energise coils of the motor in order to rotate a rotor of the motor.

According to another aspect of the invention, there is provided a kit of parts for forming the supercharger described herein. The kit comprises: an electric motor, a drive-shaft arranged to be driven by the electric motor; a first bearing for supporting the drive shaft at a first axial location; a second bearing for supporting the drive shaft at a second axial location; wherein the first and second bearings are housed in a cartridge such that both the bearings may be simultaneously installed in the supercharger via installation of the cartridge, and wherein the first and second bearings are axially spaced apart from each other such that when the cartridge is installed on the supercharger, the bearings are located upstream of the motor and the motor is in an overhung configuration.

According to another aspect of the invention, there is provided an engine comprising the supercharger according to the first aspect of the invention. The engine is preferably an internal combustion engine. The engine is preferably a relatively small capacity engine. The engine is preferably 4 litres or less, more preferably 3 litres or less, and yet more preferably 2 litres or less. The engine is preferably for an automobile. The automobile may be less than 3.5 tonnes, and more preferably less than 2 tonnes.

It will be appreciated that features described with reference to one aspect of the invention are equally applicable to another aspect, or vice versa.

BRIEF DESCRIPTION OF THE DRAWINGS A example of the invention will now be described with reference to the accompanying drawings, of which:

Figure 1 is a sectional view of a previously-suggested supercharger; and

Figure 2 is a sectional view of a supercharger according to a first embodiment of the invention.

DETAILED DESCRIPTION

Figure 2 is a sectional view of a supercharger 1 according to a first embodiment of the invention. The supercharger 1 is an electric supercharger comprising a compressor wheel 3 driven by a switched reluctance motor (SRM) 2.

The switched reluctance motor (SRM) 2 comprises a multiplicity of stator coils 4 that surround a rotor 5. A control unit 7 comprises switching electronics that are arranged to selectively energise the stator coils 4 in order to rotate the rotor 5. Such features of an SRM per se are well-known and are not discussed further herein. A drive shaft 8 is fixedly coupled to the rotor 5, such that rotation of the rotor 5 causes rotation of the drive shaft 8. The compressor wheel 3 is attached to the upstream end of the drive shaft 8.

In accordance with known superchargers, the supercharger 1 has a volute (not shown) arranged to receive compressed air leaving the compressor wheel 3. An inlet manifold (not shown) then conveys that compressed charge to an engine (not shown).

In contrast to known arrangements, the supercharger 1 of the first embodiment of the invention comprises an aluminium cartridge 9 that houses two radial bearings. A first bearing 41 is located to the rear of the compressor wheel 3, behind a seal 11. The bearing 41 is a radial bearing for supporting radial loads exerted by the drive shaft 8. Accordingly, the bearing 41 is annular and circumferentially extends around the drive-shaft 8. A second bearing 42 is identical to the first bearing except that it is axially spaced apart only a short distance downstream of the first bearing 41.

Since the bearings 41, 42 are in a supercharger, they are also configured to withstand the not insignificant axial loads generated by the compressed gas charge (output from the compressor wheel).

Both the first and the second bearings 41, 42 are located upstream of the SRM 2. There are no bearings supporting the drive shaft downstream of the SRM 2. This means the SRM 2 is in an overhung configuration. By placing the SRM 2 in an overhung configuration, the internal layout of the supercharger 1 may be altered. For example, the SRM 2 can be placed further towards the rear of the supercharger 1 than might otherwise have been possible in the previous arrangement of Figure 1. This may facilitate a more efficient use of space within the supercharger itself and/or within the engine bay in which it is to be installed.

The bearings 41, 42 are located at opposite ends of the cartridge 9. The cartridge 9 is coaxial with the drive shaft 8 and is held in the housing of the supercharger 1 in a screw-threaded fitting 9'. By placing the bearings 41, 42 in a cartridge 9, the supercharger can be efficiently assembled.

The present invention recognises that such a cartridge can be used when the motor is in an overhung configuration because the bearings are both located to the same side of the motor (and can therefore be fitted via a cartridge unit).

The drive shaft 8 primarily extends upstream of the SRM 2. However, a short (unsupported) region does extend downstream too. This downstream end of the drive shaft has a magnetic ring indicator 13 on it for indicating the rotational position of the driveshaft 8. Hall-effect sensors 15 detect this position and feed signals to the control unit 7 that controls the SRM.

Whilst the present invention has been described and illustrated with reference particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. In one embodiment (not shown) the electric supercharger is driven by an electric motor in the form of a permanent magnet motor.

Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims.

Claims

1. An electric supercharger comprising: an electric motor, a compressor wheel rotatable on a drive-shaft arranged to be driven by the electric motor; a first bearing arranged to support the drive shaft at a first axial location; a second bearing arranged to support the drive shaft at a second axial location; wherein the first and second locations are axially spaced apart from each other and are both located upstream of the motor, such that the motor is in an overhung configuration.

2. A supercharger according to claim 1, wherein the drive shaft is supported by only the first and the second bearings.

3. A supercharger according to claim 1, wherein the drive shaft is not supported by any bearings downstream of the motor .

4. A supercharger according to claim 1, wherein the first and second bearings are housed in a cartridge, such that both the bearings may be simultaneously installed in the supercharger via installation of the cartridge.

5. A supercharger according to claim 4, wherein the cartridge is held in the supercharger by way of a screw-threaded fitting.

6. A supercharger according to any preceding claim, wherein the drive shaft extends downstream of the motor and wherein a position indicator is located on the downstream end of the drive shaft for indicating the rotational position of the drive shaft.

7. A supercharger according to any preceding claim, wherein the electric motor is a Switched Reluctance Motor (SRM).

8. A supercharger according to any of claims 1 to 6, wherein the electric motor is a permanent magnet motor.

9. A kit of parts for forming the supercharger according to any preceding claim, the kit comprising: an electric motor, a drive-shaft arranged to be driven by the electric motor; a first bearing for supporting the drive shaft at a first axial location; a second bearing for supporting the drive shaft at a second axial location; wherein the first and second bearings are housed in a cartridge such that both the bearings may be simultaneously installed in the supercharger via installation of the cartridge, and wherein the first and second bearings are axially spaced apart from each other such that when the cartridge is installed on the supercharger, the bearings are located upstream of the motor and the motor is in an overhung configuration.

10. A supercharger as described herein with reference to Figure 2.