GB2578760A

GB2578760A - Compressor

Info

Publication number: GB2578760A
Application number: GB1818137.0A
Authority: GB
Inventors: Andrew Johnson Mark; Clancy Cathal; Alexander Morley Harry; David Jones Stuart
Original assignee: Dyson Technology Ltd
Current assignee: Dyson Technology Ltd
Priority date: 2018-11-07
Filing date: 2018-11-07
Publication date: 2020-05-27
Anticipated expiration: 2038-11-07
Also published as: WO2020095023A1; GB2578760B; GB201818137D0; CN112969858B; CN112969858A

Abstract

A compressor 10 has a rotor assembly (12, figure 2) having an impeller (22) and a diffuser assembly (16, figure 3) for acting on airflow generated by the impeller. The diffuser assembly comprises a rotatable end plate 50 having a substantially solid form, which reduces potential leakage paths through the end plate. The diffuser assembly may comprise a shaft 20, integrally formed with the end plate. Preferably the end plate is rotatable by a motor 60 or by airflow generated by the impeller. The rotor may include a further shaft to which the impeller is mounted extending from an upstream face (66) of the impeller. The diffuser assembly may comprise a diffuser frame 42, a diffuser casing 44, and a plurality of diffuser blades or vanes 46 extending between the diffuser frame and the diffuser casing. The end plate may be mounted to the diffuser frame via the shaft. The diffuser assembly may comprise first and second bearing(s) and preferably the second a higher speed than the first. The diffuser vanes or blades may be cantilevered. The end plate preferably includes a recess (64) for receiving a portion of the impeller. A vacuum cleaner (100, figure 4) is also claimed.

Description

COMPRESSOR

FIELD OF THE INVENTION

The present invention relates to a compressor, and more particularly, although not exclusively, to a compressor for a vacuum cleaner.

BACKGROUND OF THE INVENTION

Vacuum cleaners typically comprise compressors for generating a suction force to enable dirt and debris to be removed from a surface to be cleaned. Vacuum cleaner compressors operate in a wide range of flow rates due to the need to accommodate different cleaner heads and floor surfaces. Such compressors may have a vaneless diffuser located adjacent the impeller. However, the vaneless diffuser may stall at flow rates that are much lower than the design flow rate, causing a loss of compressor efficiency at minimum flow rate.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a compressor comprising a rotor assembly having an impeller for generating an airflow through the compressor, and a diffuser assembly for acting on the airflow generated by the impeller, wherein the diffuser assembly comprises a rotatable end plate having a substantially solid form.

The compressor according to the first aspect of the present invention may be advantageous principally as the diffuser assembly comprises a rotatable end plate having a substantially solid form. In particular, providing a diffuser assembly having a rotatable end plate may provide a relatively flat efficiency characteristic over a wide operating flow range, whilst also suppressing stall at flow rates that are much lower than the design flow rate. This may inhibit or prevent a loss of compressor efficiency at minimum flow rate.

Furthermore, as the end plate has a substantially solid form, leakage within the is diffuser assembly, for example between a low pressure diffuser assembly inlet and a high pressure diffuser assembly outlet, may be inhibited or prevented, for example compared to an arrangement where a through-hole is formed in the end plate for accommodating a shaft. The substantially solid nature of the end plate may remove the need to use a seal to inhibit or prevent leakage, for example compared to an arrangement where a through-hole is formed in the end plate for accommodating a shaft. The lack of need for a seal may result in an assembly having fewer components, which may result in less expensive and/or easier manufacture. Furthermore, the lack of need for a seal may remove the need to manufacture a seal with relatively small tolerances, and hence the compressor according to the first aspect of the present invention may be more suitable for mass manufacturing techniques with larger tolerances than, for example, a compressor where a seal to prevent leakage is required.

By substantially solid form is meant that the end plate is free from through-holes or the like, for example free of through-holes extending from one side of the end plate to another opposing side of the end plate. This does not preclude the formation of recesses formed in the end plate, for example an upstream and/or downstream face of the end plate, provided that the recesses have a closed end, for example defined by an outer surface of the end plate. This also does not preclude the end plate being hollow, for example having a cavity formed therein, provided that an outer surface defining the end plate is substantially solid, ie substantially free from openings into the cavity. For example, an upstream and/or downstream face of the end plate may comprise a substantially uninterrupted surface.

The end plate may comprise a substantially solid outer surface, for example such that no through-holes extend through the outer surface. The end plate may be free from through-holes extending from one side of an outer surface of the end plate to another opposing side of the outer surface of the end plate.

The end plate may comprise a substantially solid upstream and/or downstream face, for example such that no through-holes extend between an upstream face of the end plate and a downstream face of the endplate, or vice versa.

The end plate may be located substantially adjacent to the impeller. For example, an upstream face of the end plate may be located substantially adjacent to the impeller. An upstream face of the end plate may be located substantially adjacent to a downstream face of the impeller. The end plate may be spaced apart from the impeller, for example such that a clearance is defined between the end plate and the impeller, and the end plate and the impeller are free to rotate. The clearance between the end plate and the impeller may be relatively small, for example sufficient to enable relative rotation but not so large as to encourage undesirable flow conditions. The diffuser assembly may be located downstream of the impeller.

The diffuser assembly may comprise a shaft extending from the end plate. The end plate may be fixedly attached to the shaft, for example such that the end plate and the shaft are rotatable together.

The shaft may be integrally formed with end plate, for example as part of the same moulding process. This may be beneficial as it may result in an assembly having fewer components.

The shaft may comprise a separate component to the end plate. For example the shaft and the end plate may be formed as separate components in separate 30 moulding processes. The end plate may be attached to the shaft by adhesive, or welding, or any other appropriate attachment.

The shaft may be located in a recess formed on the end plate. The recess may have an open end for receiving the shaft, and a closed end such that the shaft is unable to extend through the entirety of the end plate, for example unable to extend from one side of the end plate to another opposing side of the end plate.

The recess may be formed on a downstream face of the end plate.

The shaft may extend from a downstream face of the end plate, for example away from the end plate in a direction of airflow through the compressor in use.

This may be beneficial over, for example, an arrangement where the shaft extends from an upstream face of the end plate, as components for rotating the end plate may be removed from the clearance between the impeller and the end plate. This may enable a tight clearance between the impeller and the end plate, and may provide a more efficient compressor.

The diffuser assembly may comprise a diffuser frame, a diffuser casing, and a plurality of diffuser blades extending between the diffuser frame and the diffuser casing. The end plate may be mounted to the diffuser frame, for example via the shaft. The diffuser assembly may comprise at least one first bearing located between the shaft and the diffuser frame. Thus the shaft, and hence the end plate, may rotate relative to the diffuser frame.

The end plate may be rotatable by a motor, for example a motor separate to a motor which causes rotation of the impeller in use.

The end plate may be rotatable by airflow generated by the impeller in use. For example, rotation of the impeller by a stator core assembly may generate an airflow through the compressor, and the airflow through the compressor may cause rotation of the end plate. This may be beneficial as it may make use of the existing airflow through the compressor to rotate the end plate, and may, for example, be less expensive than an arrangement where a motor is required to cause rotation of the end plate.

The rotor assembly may comprise a further shaft to which the impeller is 5 mounted. The further shaft may comprise a separate component to the shaft. For example the further shaft and the shaft may be formed as separate components in separate manufacturing processes. The end plate may be rotatable relative to the impeller. The further shaft may be mounted to a frame of the compressor, for example by at least one second bearing. The at least 10 one second bearing may comprise a higher speed bearing than the at least one first bearing. The end plate may be rotatable at a different speed to the impeller in use, for example a lower speed than the impeller. This may be beneficial as it may increase the pressure recovery of the diffuser, and may improve the efficiency of the compressor. The end plate may be rotatable at a ratio of less than or equal to 0.5 times the speed of the impeller, for example at a ratio in the region of 0.3 to 0.5 times the speed of the impeller.

The further shaft may extend from an upstream face of the impeller, for example away from the impeller in a direction opposite to a direction of airflow through the compressor in use. The further shaft may extend only from an upstream face of the impeller. This may be beneficial over, for example, an arrangement where the further shaft extends from a downstream face of the impeller, as components for rotating the impeller may be substantially removed from the clearance between the impeller and the end plate. This may enable a tight clearance between the impeller and the end plate, and may provide a more efficient compressor.

The further shaft may extend from an upstream face of the impeller and from a downstream face of the impeller, for example with the further shaft extending 30 from the downstream face of the impeller by no more than 5% of the overall length of the further shaft. This may be beneficial over, for example, an arrangement where the further shaft extends from a downstream face of the impeller, as components for rotating the impeller may be substantially removed from the clearance between the impeller and the end plate. This may enable a fight clearance between the impeller and the end plate, and may provide a more efficient compressor.

The further shaft may comprise a separate component to the impeller. For example the further shaft and the impeller may be formed as separate components in separate manufacturing processes. The impeller may be attached to the further shaft by adhesive, or welding, or any other appropriate attachment.

The further shaft may be located in a recess formed on the impeller, for example in a recess formed on an upstream face of the impeller. The recess may have an open end for receiving the further shaft, and a closed end such that the shaft is unable to extend through the entirety of the impeller. The further shaft may be located within a through-hole formed in the impeller, for example a through-hole that extends from an upstream face of the impeller to a downstream face of the impeller. The further shaft may be located within the through-hole with a press-fit, which may, for example, present a minimal leakage path sufficient to avoid the need for a sealing arrangement.

The diffuser assembly may comprise at least one cantilevered diffuser vane located between the end plate and the diffuser casing of the diffuser assembly.

This may be beneficial as it may provide a compressor with improved pressure recovery. The at least one cantilevered diffuser vane may be attached to the diffuser casing. The at least one cantilevered diffuser vane may comprise an axial diffuser vane, for example a diffuser vane intended to turn airflow from a radial direction to an axial direction.

The compressor may comprise a stator core assembly for causing rotation of the impeller. The stator core assembly may, for example, comprise at least one stator core, and a phase winding wound around the at least one stator core.

The end plate may comprise a recess for receiving at least a portion of the impeller, for example, an upstream face of the end plate may comprise a recess for receiving at least a portion of the impeller. This may be beneficial as it may enable the end plate to be located closer to the impeller, and may enable a more efficient compressor. The end plate may comprise a diameter greater than an outer diameter of the impeller. A recess in an upstream face of the end plate may comprise a greater diameter than an outer diameter of the impeller.

The compressor may comprise a controller for controlling the stator core assembly, for example such that the stator core assembly interacts with a permanent magnet of the rotor assembly to cause rotation of the impeller in use.

According to a further aspect of the present invention there is provided a vacuum cleaner comprising a compressor according to the first aspect of the present invention.

Preferential features of aspects of the present invention may be equally applied to other aspects of the present invention, where appropriate.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand the present invention, and to show more clearly how the invention may be put into effect, the invention will now be described, by way of example, with reference to the following drawings: Figure 1 is a schematic cross-sectional view of a compressor according to the present invention; Figure 2 is a schematic cross-sectional view of a rotor assembly of the compressor of Figure 1; Figure 3 is a schematic cross-sectional view of a diffuser assembly of the compressor of Figure 1; Figure 4 is a schematic perspective view of a vacuum cleaner comprising the compressor of Figure 1; and Figure 5 is a partial schematic cross-sectional view of an alternative diffuser assembly for use in the compressor of Figure 1.

DETAILED DESCRIPTION

A compressor according to the present invention, generally designated 10, is shown schematically in Figure 1.

The compressor 10 comprises a rotor assembly 12, a stator core assembly 14, a diffuser assembly 16, and a frame 18.

The rotor assembly 12 is shown schematically in isolation in Figure 2, and has a shaft 20, an impeller 22, a permanent magnet 24, and a pair of relatively high-speed bearings 26. The shaft 20 is elongate and generally cylindrical in form.

The impeller 22 has a hub 28, and a plurality of blades 30 extending circumferentially about the hub 28. The impeller 22 is a centrifugal impeller, for example an impeller which turns airflow from an axial direction to a radial direction. It is also envisaged that other types of impeller, for example a so-called mixed flow impeller, may be utilised. An upstream face 32 of the impeller 22 has a cylindrical recess 34 within which the shaft 20 is received. The cylindrical recess 34 does not extend through the impeller 22 to a downstream face 36 of the impeller 22, although embodiments are also envisaged where this is the case.

The permanent magnet 24 may be formed of any appropriate magnetic material. The permanent magnet 24 is substantially annular in form, and extends circumferentially about the shaft 20. The pair of relatively high-speed bearings 26 have inner races 38 attached to the shaft 20, and outer races 40 attached to an inner sleeve 74 of the frame 18. Thus the pair of relatively highspeed bearings 26 may act to mount the rotor assembly 12 to the frame 18. As shown in the figures, the pair of relatively high-speed bearings 26 is a pair of ball bearings, although it will be recognised by a person skilled in the art that other suitable bearings may be used.

Details of the stator core assembly 14 are not pertinent to the present invention, and hence will not be discussed here in any great detail, save to say that the stator core assembly 14 may comprise at least one stator core having a phase winding wound about the stator core. Such stator core assemblies will be known to a person skilled in the art. The stator core assembly 14 is attached to the frame 18 such that the stator core assembly 14 opposes the permanent magnet 24 of the rotor assembly 12. In use a controller (not shown) may control supply of voltage to the stator core assembly 14, such that the stator core assembly 14 interacts with the permanent magnet 24 to rotate the shaft 20, thereby causing rotation of the impeller 22 to generate an airflow through the compressor 10.

The diffuser assembly 16 is shown in isolation in Figure 3. The diffuser assembly 16 comprises a diffuser frame 42, a diffuser casing 44, a first plurality of diffuser vanes 46, a second plurality of diffuser vanes 48, and an end plate 50.

The diffuser frame 42 comprises a frame recess 52 which accommodates a drive mechanism for driving rotation of the end plate 50. The drive mechanism comprises a pair of relatively low-speed bearings 56, a shaft 58, and a motor 60. The pair of relatively low-speed bearings 56 have inner races 54 attached to the shaft 58, and outer races 57 attached to the diffuser frame 42. As shown in the figures, the pair of relatively low-speed bearings 56 is a pair of ball bearings, although it will be recognised by a person skilled in the art that other suitable bearings may be used.

The shaft 58 extends from a downstream face 68 of the end plate 50, and in a presently preferred embodiment the shaft 58 is integrally formed with the end plate 50, for example as part of the same moulding process. The shaft 58 is substantially hollow, and receives the motor 60 therein. Although not shown in the figures, a permanent magnet may be attached to the hollow interior of the shaft 56 for interaction with the motor 60, for example. Thus the shaft 56 and motor 60 may resemble an outer-rotor type motor. Alternatively, an output shaft of the motor 60 may be directly attached to the shaft 58, or another portion of the end plate 50, such that rotation of the output shaft of the motor 60 drives rotation of the end plate. The motor 60 may be any conventional motor, as will be appreciated by a person skilled in the art, and is configured to drive rotation of the shaft 58, and hence rotation of the end plate 50.

The diffuser casing 44 is substantially annular in form, such that the diffuser casing 44 extends circumferentially about the diffuser frame 42. The diffuser casing 44 constitutes a downstream portion of the frame 18, and as shown in the figures the diffuser casing 44 is an integral part of the frame 18. It will be appreciated by a person skilled in the art that alternative embodiments are envisaged where, for example, the diffuser assembly 16 is a separate component to the frame 18, and hence the diffuser casing 44 is attached to the frame 18 by appropriate attachment means.

The first plurality of diffuser vanes 46 are axial diffuser vanes, for example diffuser vanes intended to turn airflow from a centrifugal, or radially outward, direction toward an axial direction in use. The first plurality of diffuser vanes 46 are cantilevered, in that one end of each diffuser vane 46 is attached to the diffuser casing 44, whilst another opposing end of each diffuser vane 46 is freely located adjacent to the end plate 50. In such a manner the end plate 50 may still rotate with the provision of the first plurality of diffuser vanes 46. This may provide improved pressure recovery relative to an arrangement where the first plurality of diffuser vanes 46 are not present. The geometry of the first plurality of diffuser vanes 46 may be designed to provide desired operating characteristics, as will be appreciated by a person skilled in the art.

The second plurality of diffuser vanes 48 are axial diffuser vanes, for example diffuser vanes intended to turn airflow from a centrifugal, or radially outward, direction toward an axial direction in use. The second plurality of diffuser vanes 48 have one end fixedly mounted to the diffuser frame 42, and another opposing end fixedly mounted to the diffuser casing 44. Thus the second plurality of diffuser vanes 48 may act to locate the diffuser frame 42 relative to the diffuser casing 44. The second plurality of diffuser vanes 48 are located downstream of the first plurality of diffuser vanes 46.

The end plate 50 is generally disc-shaped, albeit with axially extending edge portions 62. As can be seen from Figure 3, the end plate 50 resembles an end cap for the diffuser frame 42. The end plate 50 comprises a front recess 64 which receives at least a portion of the impeller 22. This enables the end plate 50 to be located closer to the impeller 22, and may enable a more efficient compressor 10.

The outer surfaces of the end plate 50 are substantially solid, in that no through-holes are formed which extend through the end plate 50. In particular, as can be seen from Figure 3, for example, there are no through-holes present in the end plate which extend from an upstream face 66 of the end plate 50 to a downstream face 68 of the end plate 50. Thus there are no potential leakage paths through the end plate 50 for air flowing through the diffuser assembly 16 in use. This may provide improved pressure recovery and a higher efficiency compressor.

to As previously mentioned, the shaft 58 is integrally formed with, and extends from, the downstream face 68 of the end plate 50. Thus rotation of the shaft 58 by the motor 60 causes rotation of the end plate 50. The end plate 50 thus acts as a rotating vaneless diffuser in the region where air exits the impeller 22 in a radial direction. This may provide a relatively flat efficiency characteristic over a wide operating flow range, whilst also suppressing stall at flow rates that are much lower than the design flow rate. This may inhibit or prevent a loss of compressor efficiency at minimum flow rate.

The motor 60 acts to rotate the end plate 50 at a speed which is lower than, albeit an appreciable fraction of, the speed of rotation of the impeller 22.

The frame 18 can be seen in Figure 1. The frame 18 comprises a main body 70, an inner sleeve 72, a shroud portion 74, and the diffuser casing 44. The main body 70 is generally cylindrical, and provides a housing for the rotor assembly 12 and the stator assembly 14. The inner sleeve 72 is mounted to the main body 70 by struts 76, and defines a mounting portion for the pair of relatively high-speed bearings 26. The shroud portion 74 is integrally formed with the main body 70, and is shaped and dimensioned to cover the impeller 22 with a tight clearance. The diffuser casing 44 is integrally formed with the shroud portion 74, and has the form previously discussed. Although a specific form of frame is described herein, it will be recognised by a person skilled in the art that the form of the frame is not essential to the present invention, and that an alternative form of frame may be used, if appropriate.

In use air flows from an inlet (not shown) of the compressor 10, over the stator assembly 14 and through the main body 70 toward the impeller 22. The impeller 22 turns air from an axial direction to a radial direction, and air flows around the shroud portion 74 toward the diffuser assembly 16. As air enters the diffuser assembly 16 air passes the region of the rotating end plate 50, before passing through the first 46 and second 48 pluralities of diffuser blades in I 0 sequence, and exiting the compressor via an exhaust outlet (not shown).

The rotating end plate 50 provides a relatively flat efficiency characteristic over a wide operating flow range, whilst also suppressing stall at flow rates that are much lower than the design flow rate. This may inhibit or prevent a loss of compressor efficiency at minimum flow rate. Furthermore, as the outer surfaces of the end plate 50, particularly the upstream face 66 and downstream face 68, are substantially solid, potential leakage paths for airflow through the diffuser assembly 16 are removed. This may provide a compressor having increased efficiency, for example an improvement in efficiency in the region of 3-5%.

A vacuum cleaner 100 including the compressor 10 is shown schematically in Figure 4. Such a vacuum cleaner may have a relatively flat efficiency characteristic over a wide operating flow range, which may maximise battery run time whilst simultaneously maintaining peak suction power.

An alternative embodiment of a diffuser assembly 80 is shown in Figure 5. The diffuser assembly 80 of Figure 5 differs from the diffuser assembly 16 of Figures 1 and 3 in that a rotatable diffuser wall 82 is attached to the end plate 50 via struts 84. Thus the rotatable diffuser wall 82 rotates with the end plate 50, and the rotatable diffuser wall 82 and end plate 50 define a flow passageway through the diffuser assembly 80. A seal 86 is provided between the rotatable diffuser wall 82 and the diffuser casing 44 to prevent leakage.

Claims

CLAIMS1. A compressor comprising a rotor assembly having an impeller for generating an airflow through the compressor, and a diffuser assembly for acting on the airflow generated by the impeller, wherein the diffuser assembly comprises a rotatable end plate having a solid form.
2. A compressor as claimed in Claim 1, wherein the diffuser assembly comprises a shaft extending from the end plate, and the shaft is integrally I 0 formed with end plate.
3. A compressor as claimed in Claim 2, wherein the shaft extends from a downstream face of the end plate.
4. A compressor as claimed in any preceding claim, wherein the end plate is rotatable by a motor.
5. A compressor as claimed in any of Claims 1 to 3, wherein the end plate is rotatable by airflow generated by the impeller in use.
6. A compressor as claimed in any of Claims 2 to 5, wherein the rotor assembly comprises a further shaft to which the impeller is mounted, and the further shaft extends from an upstream face of the impeller.
7. A compressor as claimed in any of Claims 2 to 6, wherein the diffuser assembly comprises a diffuser frame, a diffuser casing, and a plurality of diffuser blades extending between the diffuser frame and the diffuser casing, the end plate is mounted to the diffuser frame via the shaft, the diffuser assembly comprises at least one first bearing located between the shaft and the diffuser frame, and the further shaft is mounted to a frame of the compressor by at least one second bearing.
8. A compressor as claimed in Claim 7, wherein the at least one second bearing comprises a higher speed bearing than the at least one first bearing.
9. A compressor as claimed in any preceding claim, wherein the diffuser assembly comprises at least one cantilevered diffuser vane located between the end plate and a diffuser casing of the diffuser assembly.
10. A compressor as claimed in any preceding claim, wherein the substantially solid outer surface comprises a recess for receiving at least a portion of the impeller.
11. A vacuum cleaner comprising a compressor according to any preceding claim.