GB2388017A

GB2388017A - Diffuser plate

Info

Publication number: GB2388017A
Application number: GB0209847A
Authority: GB
Inventors: Siu Chun Tam
Original assignee: Johnson Electric SA
Current assignee: Johnson Electric SA
Priority date: 2002-04-30
Filing date: 2002-04-30
Publication date: 2003-11-05
Also published as: GB0209847D0

Abstract

A diffuser plate 14 for a flow-through vacuum cleaner motor has a plurality of passage openings 47 on one side of the plate adjacent an impeller. The passage openings 47 lead air from the impeller to the other side of the diffuser plate 14 where pathways are defined by channels 50 in the plate 14. The channels 50 define blind passages which direct the air radially inward and circumferentially, and then axially in separate air flows through different parts of the motor for cooling. Part of the air may be directed through the motor housing without having any cooling effect. There is a further claim for a vacuum cleaner motor characterised by the diffuser plate of the invention.

Description

23880 1 7

Diffuser Plate Background of the Invention

This invention relates to vacuum cleaner motors and in particular, to a diffuser plate 5 for a flow through vacuum cleaner motor.

Vacuum cleaners can be divided into two types, dry and wet. A dry vacuum cleaner cannot handle liquids and generally uses a flow through vacuum cleaner motor in which the working air flow of the vacuum cleaner is also used to cool the motor. A 10 wet type vacuum cleaner may be used in applications involving water or other liquids and generally uses a bypass type vacuum cleaner motor in which working air flow does not pass through the motor to cool it. The motor has a separate fan providing cooling air flow for the motor.

15 In the flow through motor, the motor drives a centrifugal impeller which creates the air flow or suction which allows the vacuum cleaner to pick up dust and debris. The air leaves the impeller radially with a high degree of swirl and must be channeled axially and then radially inward and then axially again through the motor itself. This is achieved by use of a diffuser plate which has a generally planar surface backing the 20 impeller and is bolted to a flange of the motor housing. A fan shroud covers the impeller and diffuser plate and is commonly fixed to the flange by crimping. The shroud has an opening which defines the inlet to the impeller. The air exhausts through the motor housing.

25 The diffuser has a number of equally angularly spaced circumferentially located, axially and circumferentially inclined surfaces leading from the planar surface to the flange. These inclined surfaces lead the air into a number of passageways for directing the air generally into the interior of the motor to cool the motor.

30 The diffuser plate typically also supports a bearing for the rotor shaft and the air is directed axially by an enlarged fillet about the bearing retainer. In this manner, the diffuser plate also acts as a fan end bracket for the motor.

In a known design, the passageways are formed by walls on the underside of the 35 diffuser plate. These walls are arranged in a generally symmetrical manner to move the air radially inward towards the bearing filet while trying to straighten the air flow somewhat. However, the walls stop short of the bearing fillet and allow the increased

pressure of the air in this region to push the air through the rotor without any thought as to where cooling is required.

In the past, this has been quite satisfactory due to the large volume of air flowing 5 through the motor and to the relatively large thermal mass of the stator and rotor cores. However, today the desire for more efficient, more powerful and smaller, lighter motors means that the thermal mass of the stator and rotor have been significantly reduced while increasing the power ratings of the motor, requiring particular attention to the cooling of the motor to avoid hot spots which may l O otherwise lead to failure of motor safety tests.

The motors are typically universal motors having wound stators, wound rotors and commutators. These parts produce the heat and need to be cooled. The motor parts themselves are however, a serious impediment to the flow of exhaust air creating a 15 major inefficiency in the operation of the motor. However, without cooling, the motor will overheat. The balance between motor efficiency and cooling has not been addressed in a simple way in the prior art.

Brief Summary of the Invention

20 This problem is addressed by the present invention by providing a diffuser plate which defines separate air flow pathways through the motor which are chosen to provide efficient cooling of the heat generating parts and efficient exhausting of a part of the working air not required for cooling.

25 Accordingly, in a first aspect thereof, the present invention provides a diffuser plate for a through-flow vacuum cleaner motor having an impeller and a housing part having a flange to which the diffuser plate is fastened, the diffuser plate comprising: a plate like body having a thickness, a first side, a second side opposite the first side, a central aperture and a radially outer peripheral edge, the first side being substantially 30 planar and arranged to be disposed adjacent the impeller, the central aperture is stepped, having a shaft portion and a larger bearing retainer portion open to the second side for receiving a shaft bearing of the motor, a number of circumferentially spaced peripheral openings extending axially and circumferentially through the thickness of the body from the first side to the second side, a plurality of channels 35 formed in the second side of the body and extending from the peripheral openings in a generally circumferential and radial direction towards the central aperture, whereby the openings and channels direct air from the first side to the second side in an axial and circumferential direction, whereby the channels direct the air circumferentially

and radially from the periphery towards the central aperture passed the flange and then axially to exhaust through the motor housing part at predetermined locations.

According to a second aspect, the invention also provides a vacuum cleaner motor 5 comprising: a universal motor driving a high speed centrifugal impeller; the universal motor having a wound rotor coupled to the impeller, a wound stator, a housing supporting the stator and having a radially extending flange, a diffuser plate fixed to the flange supporting a bearing for the rotor and directing air flow from the impeller radially inward and axially through the housing; and a fan shroud connected to the 10 flange, extending about the impeller and defining an air inlet for the impeller; wherein the diffuser has a plurality of channels formed in the side facing the flange which connect openings formed in the side facing the impeller whereby air flow generated by the impeller is directed from the impeller, through the openings and along the channels and through the housing, the openings being formed at a peripheral edge of 15 the diffuser and the channels directing the air from the openings radially inward, circumferentially and axially, the channels creating separate air flow paths to cool specific parts of the motor or to exhaust the air through the housing.

Preferably, the channels are arranged to direct air flow through the motor as 20 substantially individual air flows.

Brief Description of the Drawings

Two preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure I is an exploded view of a vacuum cleaner motor assembly according to the present invention; Figure 2 is a side cross-sectional view of the assembly of Figure 1; Figure 3 is a perspective view from below of a diffuser plate being a part of the assembly of Figure 2; Figure 4 is a perspective view of a diffuser plate as shown in Figure 3; and Figure 5 is an underneath sectioned plan view of the assembly of Figure 2; and Figure 6 is a perspective view of an alternate diffuser plate.

( Detailed Description of the Preferred Embodiments

Figure 1 shows a flow through blower assembly or vacuum cleaner motor in an exploded elevational view. The assembly is a high speed centrifugal impeller driven S by a universal motor. Starting from the top as shown, the main parts are a motor housing 11, a rotor 12, a stator 13' a diffuser 14, an impeller 15 and a fan shroud 16.

The assembly while generally well known will be described briefly so as to give a better appreciation of the invention. The housing 11 is generally cylindrical. The 10 upper end is opened by four windows 17 which leave a cross support 18 holding an integral bearing retainer 19 accommodating a bearing for the rotor. Two brush cages 20 are disposed in separate diametrically opposed apertures in the housing 11 at the closed end. Each cage 20 contains a brush and spring (both not shown). The open opposite end of the housing has a radially outwardly extending flange 21.

The rotor 12 has a shaft 22 journalled in bearings 23, 24, the upper bearing 23 being fitted into the beanug retainer 19 of the housing 11. A rotor core 25 of stacked laminations is mounted on the shaft 22 next to a commutator 26. Rotor windings 27 are wound about the rotor core 25 and terminated on the commutator 26. The lower 20 end of the shaft has a screw thread 28.

The stator 13 has a stator core 29, also of stacked laminations of silicon steel. Two stator coils 30 are wound about poles of the stator 29 and insulated therefrom by insulators 31 which also supports terminals 32 onto which the coils are terminated.

25 Two terminals connect, in use, to the power input leads and the other two connect to the brush cages 20 via a jumper (not shown). Two screws 33 fasten the stator core 29 to the housing 11.

lithe diffuser 14 is a plate like body with a definite thickness. This will be describe in 30 detail hereinafter but visible in Figure l are four projections 34 which mate with holes in the flange 21 for correct orientation of the diffuser 14 with respect to the housing 11. Four screws 35 fasten the diffuser to the flange.

The impeller 15 is a single stage impeller of the sheet metal high speed centrifugal 35 type. A seat 36 spaces the impeller from the lower bearing 24 and a lock nut 37 is screwed onto the threaded end of the shaft 22 to nip or clamp the impeller 15 between the seat 36 and the lock nut 37.

s The shroud 16 is a drawn metal part with a cylindrical peripheral wall 38 and a profiled end wall 39. The end wall 39 has a central opening 40 forming the air inlet to the impeller 15. The peripheral wall 38 is pressed over the diffuser 14 and the flange 21 and is crimped to the flange 21 to prevent removal.

s Figure 2 shows the motor assembled in sectional view which more clearly shows the interaction between the various parts. Note in particular that the stator coils 30 extend into the volume or thickness of the diffuser plate 14. It also shows that the diffuser plate has a central aperture 41 which is stepped providing a narrower shaft portion 42 10 and a wider bearing retainer portion 43 in which the lower bearing 24 is fitted.

Figure 3 shows the diffuser plate from below. The diffuser 14 is a substantially circular plate having a thickness. The lower surface 44 is substantially flat although there is a low circular boss or reinforcement 45 about the central aperture. There are 15 four holes 46 for receiving the screws 35. About the peripheral region of the plate, there are a number of (in this case, eight) air channel openings 47 which are in part defined by respective lead-in surfaces 48 which extend both axially and circumferentially to separate the air flow and lead the air to and through the openings 47. Figure 4 shows the diffuser plate 14 viewed from above. As can be seen, the diffuser plate has an upper surface 49 which is also substantially flat from which the projections 34 extend. However, the bearings portion 43 of the central aperture 41 cuts into the center of the plate and there are eight deep and wide charmers 50 cut into the 25 upper surface and extend substantially into the thickness of the plate. As can be seen, the channels SO start at a respective opening 47 and continue in the same circumferential direction while also moving radially inward to guide the air flow towards the center of the motor. However, the channels are not all similar and each terminates at a desired location for directing the air it is channeling. As the stator 15 30 is symmetrical with two staler coils, the eight channels can be described as two sets of four different channels.

The arrangement of the channels is more clearly understood from Figure S which is a sectional view of the motor assembly sectioned through the diffuser plate 14 and 35 looking into the motor housing so that the walls of the channels can be seen in clear relationship to the stator and housing. Here the individual channels have been labeled A to D of each set.

( Channel A extends right up to the bearing portion 43 of the central aperture which has a large fillet radius (shown in Fig. 4) to help direct the air flow axially into the larger air gap between the rotor 12 and the stator 13 between the stator poles. Channel A thus provides cool air flow for the rotor.

Channel B extends right up to the bearing portion of the central aperture as well and is the largest channel. The stator coils 30 extend into this channel and this air flow is mainly to cool the stator coils. The air gap between the stator 13 and rotor 12 above channel B is relatively small as this is the stator pole area.

Channel C is the shortest channel and directs air into the relatively large gap between the motor housing 11 and the stator 13. This air flow is not used for cooling the stator but to provide a lower resistance exhaust air flow path for the working air.

15 Channel D provides some cooling for the stator core directing air into the opposite side of the stator coil 30 from channel B. Some air exhausts between the housing 11 arid the stator core 29 but this flow is minimal due to the presence of stator mounting blocks. 20 An alternative channel design is shown in Figure 6 which is similar to the first embodiment except that channels B and D are joined together to form a continuous channel BD to cool the stator coil 30 which extends into the combined channel. It is thought that by removing the wall between channels B and D that the "D" side of the stator coil 30 will be better cooled. The combined channel BD then has air flow 25 coming in from two openings 47 and the mating of the two air flows helps to drive the combined air flow axially over the stator coils.

The embodiment described above is given by way of example only and various modifications will be apparent to persons skilled in the art without departing from the 30 scope of the invention as defined in the appended claims.

Claims

1. A diffuser plate for a through-flow vacuum cleaner motor having an impeller and a housing part having a flange to which the diffuser plate is fastened, the diffuser 5 plate comprising: a plate like body having a thickness, a first side, a second side opposite the first side, a central aperture and a radially outer peripheral edge, the first side being substantially planar and arranged to be disposed adjacent the impeller, 10 the central aperture is stepped, having a shaft portion and a larger bearing retainer portion open to the second side for receiving a shaft bearing of the motor, a number of circumferentially spaced peripheral openings extending axially and circumferentially through the thickness of the body from the first side to the second side, 15 a plurality of channels formed in the second side of the body and extending from the peripheral openings in a generally circumferential and radial direction towards the central aperture, whereby the openings and channels direct air from the first side to the second side in an axial and circumferential direction, whereby the channels direct the air 20 circumferentially and radially from the periphery towards the central aperture passed the flange and then axially to exhaust through the motor housing part at predetermined locations.

2. A diffuser according to claim 1 wherein 25 the channels are arranged to direct the air flow through the motor housing part as substantially individual air flows.

3. A diffuser according to claim 1 or 2 wherein the channels are arranged to direct cooling air flow over the stator coils, and 30 over the rotor and to direct exhaust air flow between a stator core and the motor housing part.

4. A vacuum cleaner motor comprising: a universal motor driving a high speed centrifugal impeller; 35 the universal motor having a wound rotor coupled to the impeller, a wound stator, a housing supporting the stator and having a radially extending flange, a diffuser plate fixed to the flange supporting a bearing for the rotor and directing air flow from the impeller radially inward and axially through the housing; and

a fan shroud connected to the flange, extending about the impeller and defining an air inlet for the impeller; wherein the diffuser has a plurality of channels formed in the side facing the flange which connect openings formed in the side facing the impeller whereby air flow

5 generated by the impeller is directed from the impeller, through the openings and along the channels and through the housing, the openings being formed at a peripheral edge of the diffuser and the channels directing the air from the openings radially inward, circumferentially and axially.

10 5. A motor according to claim 4 wherein at least one channel directs cooling air flow to the stator coils.

6. A motor according to claim 4 or 5 wherein at least one channel directs cooling air flow towards the rotor.

7. A motor according to claim 4,

S or 6 wherein at least one channel directs air flow to be exhausted through the motor housing without significant cooling of any heat generating part of the motor.

20 8. A motor according to claim 4, S. 6 or 7 wherein the channels create separate air flow paths to cool specific parts of the motor or to exhaust the air through the housing.

9. A vacuum cleaner motor and diffuser plate substantially as hereinbefore 25 described with reference to the accompanying drawings.