Electric motor for clothes washing machine drive

Abstract: An electric motor (2) for a clothes washing machine including the motor and a drive, the motor having a stator (25) held outboard of a frame carrying bearings (38, 39) in which a shaft (11) rotates, the shaft carrying the rotor (21) outboard of the stator (25), and permanent magnets (17) on an inner face of the rotor. The stator (25) is formed as an annular helical yoke edgewise wound from a strip of magnetic material and having an inner face and an outer face, the strip having pole pieces (8) formed integrally therewith extending from one edge of the strip and the strip being edgewise wound whereby the pole pieces coincide in stacked groups to form a plurality of poles arrange at equally spaced intervals extending radially outwardly from the outer face of the yoke. Energisable stator windings (26) are wound directly on the poles (8) of the stator and are adapted to be energised through an electronic commutation circuit (65, 66) and the rotor (21) is mounted for rotation exteriorly of and relative to the stator, the rotor comprising a backing ring (16) of magnetic material and a series of permanent magnets (17) held at spaced apart intervals on an inner surface of the backing ring (16) and opposing the poles (8) of the stator (25).

Description: This invention relates to clothes washing machines of the type having a cabinet in which an agitator is mounted on a vertical axis and is oscillated back and forth within a perforated spin tub which, in turn, is mounted within a watertight container, the spin tub and the agitator rotating continously in one direction to give a spin action, the cabinet containing an electric motor and driving means for the agitator and spin tub and/or clothes washing machine incorporating such drives. A clothes washing machine of the general type described above is disclosed in USA 2,665,576. In the washing machine of USA 2,665,576 the agitator is fixed to the spin tub. When an agitating action is required the spin tub is rotated back and forth independently of the water tight container. When a spin action is required the spin tub and water tight container are rotated together in one direction. The washing machine of USA 2,665,576 has a float chamber for effecting engagement and/or disengagement of a clutch mechanism which engages a spin tub with the water tight container. The engagement and/or disengagement of the clutch mechanism is dependent on the quantity of water present in the water tight container. The arrangement disclosed in USA 2,665,576 has a disadvantage that the agitator, spin tub and water tight container must all be rotated during the spin action. Also, since the agitator and spin tub are connected together, agitation is not as effective as it would be if the agitator was moving while the spin tub was kept stationary. Another disadvantage with the washing machine disclosed in USA 2,665,576 is that during a spin cycle there must be a hydraulic connection between the water tight container and the spin tub which is less efficient than a direct mechanical connection between the motor and the spin tub. FR 1,340,648 and DE 1,907,719 both disclose clothes washing machines having motors which directly drive the wash drums without the need for belts and pulleys or gearboxes. No control to produce both the desired complex wash motion and a separate spin motion of the wash drum is envisaged. CH 462,765 discloses an electric motor for a washing machine which attempts to solve the difficulties of the conflicting requirements of wash motion and spin motion by integrating two co-linear separate motors, one optimised for wash motion and the other optimised for spin motion. The increased axial length of the motor results in reduced volumetric capacity of the driven wash drum and separate current controllers are required for each section of the motor. It is, therefore an object of the present invention to provide an electric motor for a clothes washing machine of the type described which goes some way towards overcoming the above disadvantages in the prior art. According to the present invention there is provided an electric motor for a clothes washing machine having a stator, a rotor rotatable exteriorly of said stator and a shaft which carries said rotor, a motor frame having a single pair of spaced apart bearings mounted in said frame in a central disposition relative to said frame, said shaft rotatably mounted directly in said bearings; said frame having stator locating means arranged to hold an outer cylindrical surface of said stator concentric with said bearings; at least one bearing of said pair of bearings spaced at a remote position relative to said stator; characterised by electronic commutation equipment for electronically commutating said motor; said stator carrying energisable windings wound directly on poles thereof, said windings adapted to be energised by said electronic commutation equipment; said electronic commutation equipment electronically commutating said motor such that said rotor moves in a washing motion wherein the rotor rotates back and forth, or a spin motion wherein said rotor rotates continuously, so that the electric motor can provide both wash and spin motion; said rotor having a hub which mounts said rotor on said shaft, a backing ring of a magnetic material, a series of permanent magnets spaced apart on an inner surface of said backing ring, a backing ring support rigidly attached to said hub which holds the inner faces of said permament magnets and said backing ring concentric with said shaft and said backing ring and magnets being rotatable exteriorly of said stator windings. To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting. The invention consists in the foregoing and also envisages constructions of which the following gives examples. One preferred form of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional elevation of a clothes washing machine constructed according to the invention, with some parts shown at 45° in plan to other parts, Figure 2 is an enlarged view part in cross-section of a water container, spin tub, agitator, drive and electric motor, and Figures 3 and 4 are respectively a plan view and cross-section of preferred motor frames incorporated in the invention in the preferred form, Figure 5 is a further enlarged view of a seal shaft and bearings being a part of Figure 2, Figure 6 is a part cross-section of an alternative embodiment of the invention, Figure 7 is a part cross-section of a further alternative embodiment of the invention, Figure 8 is a scrap elevation at 45° to the view in Figure 1, and Figure 9 is a rear view of a motor agitator forming part of the invention. Referring to the drawings a clothes washing machine comprises a cabinet 1 of square cross section which has mounted in it an electric motor 2 constructed according to the present invention as will be described further later. A water container 3 is suspended within the cabinet 1 by suspension rods 4 and springs 5 and for example four springs and rods are provided, and the motor and other mechanism are attached to the container 3. The springs are provided in the corners of the square cross-section cabinet 1 accordingly parts of the rod are shown in sectional view in Figure 8 which is at 45° to the other sectional view of Figure 1. By water is meant washing liquid, for example water and detergent. Contained within the water container 3 there is a perforated spin tub 6 and within the spin tub is an agitator 7. An opening lid 9, shown only partially is provided through which clothes may be inserted into the container and within the spin tub 6. The spin tub is partly balanced by upper balancing ring 40 shown only in the rear one side in Figure 1. The springs terminate in hooks 12 which engage in apertures 13 in the container base moulding 29. The agitator 7 is mounted on a hollow drive shaft 11 so as to rotate therewith but is slidable axially thereon. The spin tub 6 is coaxially mounted on the shaft 11 so as to be rotatably and also slidable axially thereon. The motor 2 is constructed as follows. A rotor 15 has a backing ring 16 (Figure 2) and the backing ring is formed from a strip of magnetic material for example a silicon steel alloy and the strip of steel is coiled on edge with adjacent surfaces lightly insulated and touching each other to provide a short hollow cylinder or annular helix. Inside the helix there is provided a series of magnets 17, the backing ring 16 being expanded slightly before being placed over the magnets placed in a mould. The magnets are permanent magnets of a material capable of being magnetised to a high flux value, for example, Neodinium iron made by Magnaquench Inc. and the annulus and the magnets are held in place by a plastics member 18 which has a hub 19, a disc or spoked connector portion 20, and substantially cylindrical element 21, the member being moulded over the backing ring and magnets so as to maintain the inner faces of the magnets 17 concentric with the axis of the hub 16. The stator 25 of the motor has a magnetic core which comprises a strip of magnetic material again preferably a silicon steel alloy or other low hysteresis steel which is preformed to provide spaced apart pole pieces and again this strip is formed by bending on edge to form an annular helix in the form of a hollow cylinder with the poles 8 formed by the stacked pole pieces pointing outwardly. As may be seen in Figure 9 the poles 8 are connected together by a narrow band 14 so that bending on edge is relatively easily effected. To provide insulation for windings on the poles of the core a top insulating moulding 22 is placed on one side of the poles and a bottom insulating moulding 23 placed on the opposite side, meeting at a joint line 24. Windings are placed on the mouldings wound around each pole and such windings 26 are effected on the poles directly. It is preferable that the stator be wound in a three phase star connected mode and the windings are made and connected using known techniques. The stator 25 and the rotor 15 are mounted as will shortly be described. The water container 3 is preferably an injection moulding and the base 29 has motor support columns 30 preferably braced with stiffening webs 31. These webs extend to the outer perimeter of the container 3 and are moulded integrally with the container. The motor 2 includes two bearing frames 32 and 33 which comprise injection mouldings of a die cast metal or plastics material or preferably steel pressings or plastic material. Preferably the frames 32 and 33 are produced from the same mould or set of dies, thus ensuring equality of dimensions between the two frames. The frames are carefully designed and made so that the bearing mouldings 27 and 28 are concentric with locating pins or dimples 34 and corresponding holes 35 at the periphery of the frames and with the external angle 36 in which the inner corner 3 of the stator 25 fits with an interference bit. Stiffening depressions 49 are provided to stiffen the frames and on assembly one frame is assembled rotated 45° relative to the other frame to provide correct matching of holes and dimples. Bearings 38 and 39 fit in the bearing mountings 27 and 28 and the bearings are spaced apart by a spacing tube 40 which encircles the drive shaft 11. The hub 19 is fixed to the shaft 11 by a bolt 41 engaging a nut 41a held in the hollow of the shaft 11 by the shaft 11 being swaged down to provide splines which engage corresponding spline spaces 42 in the hub 19. For transport purposes a further nut 43 holds the assembly supported by suspension rods and fixed to a cabinet member 44. The spin tub 6 comprises a stainless steel perforated hollow cylinder 45 fixed to a plastics extruded base 46, for example, by spinning the lower edge of the cylinder 45 on to the periphery of the plastics base 46. If desired a lower balancing ring 47 is provided and the upper and lower balancing rings each comprise a hollow ring with baffles and liquid container therein and the rings are each closed by an annular disc 48 and 48a respectively. One balancing ring preferably the ring 10 have been found to give reasonable balance while spinning. A plurality of bridges 50 are provided at spaced intervals with gaps between them and the bridges connect the balancing ring 47 (if fitted) to an air chamber in the form of a bell having an open mouth directed downwardly and a tube 52 integral therewith which surrounds the shaft 11. A low friction plastics bearing 53 enables the plastics base 29 and consequently the spin tub 6 to rotate and slide axially on the drive shaft 11. A series of downwardly directed dog clutch teeth 55 (Figure 2) of a high impact duty material, for example a high impact duty plastics material, are carried by a carrier 56 riveted screwed or otherwise fixed to the air chamber 51, for example by screws 57. A ring 60 carries coacting dog clutch teeth 61 also of a high impact duty material and the ring 60 is rotatable by and axially slidable on the drive shaft 11, for example by engagement of splines on the ring 60 with splines on the drive shaft 11. The agitator 7 has a boss 62 with inner splines 63 engaging outer splines 64 on the ring 60 so that rotation of shaft 11 results in rotation of the teeth 61 and the agitator 7, and the boss 62 slides axially on the drive shaft 11 as may be seen by comparing the "up" position of elements on the left hand side of Figures 1 and 2 with the "down" position on the right hand side. The air chamber 51 is designed to provide a flotation or buoyancy force resulting from the entrapment of air in the air tight air chamber 51 when water closes the perimeter of the lower edge of the air chamber 51. In the event that water enters the air chamber 51, for example because of turbulence during agitation, the lower face could be closed off with a disc 54. The buoyancy force is at least sufficient to lift the spin tub 6, and the agitator 7 when a substantially predetermined volume of water is provided in the container 3, and the spin tub and agitator 7 is shown in the "up" position on the left hand side of Figures 1 and 2 and in the "down" position on the right hand side. When the spin tub 6 is in the up position, that is, supported by floatation of the air chamber 51 the teeth 55 and the teeth 61 are disengaged from each other and the agitator may be rotated freely over any desired rotational movement independent of the spin tub 6. When water is absent or substantially absent from the container 3 the spin tub 6 sinks until the teeth 55 and 61 are engaged. The spin tub 6 and agitator will then be rotated as one unit and this rotation will be effected continuously in one direction to spin clothes in the spin tub to a drier condition in the known way. To assist in freeing frictional contact between the axially sliding parts during up and down movement of the spin tub during filling with, and emptying of water, control means are provided controlling motor 2 to give a slow agitating action, that is, forward and reverse rotation over a small arc of movement. At each reversal the dogs will reverse contact and be free of each other for a short time due to clearances as between the dogs and spaces between the dogs. To assist in fixing the spin tub against rotation during agitation, that is, when the agitator is in the up position, the upper edge 67 of the spin tub may contact a frictional surface 68 on the underside of a top member 69 of the container 3. The agitator 7 has external blades 81 thereon which extend from the surface of both column 82 and the upper surface of an upper coned disc 83. There is a space 84 between the disc 83 and the upper surface 85 of the air chamber 51 this space may be divided with radial vanes (not shown) since the purpose of the space arrangement is to provide a centrifugal impeller. Such an impeller may be otherwise provided, for example an independent centrifugal pump could be provided. Outlet openings 86 are provided from the space 84 at or near the outer edge of the disc 83 the outer edge 87 of which is turned downwardly and operates in close proximity to the inner edge of the balance ring 47. As a result of this construction a pumping action is given, pumping water from the centre of column 82, from apertures 88 through space 84 below balance ring 47 to space 86 between the spin tub 6 and the container 3 and lint is restrained in this space before the water re-enters the spin tub through the holes 90. If desired a container may be mounted on the column 82 such container holding a clothes conditioner in the known way. Electronic commutation equipment 65 is provided on an annular printed circuit board in an annular container 66 mounted below the stator 25 and the electronic commutation equipment is preferably enclosed in a compound for protection and heat sinking, and is such as to enable the electric motor 2 to move in a backward and forward motion thus causing the shaft 11 to be oscillated backward and forth resulting in the agitator 7 being also rotated in a back and forth motion to give the well known washing motion. Such electronic commutation equipment is described in New Zealand Patent No 213489/213490 (published on 27 March 1990) and US Patent No 4857814 (published 15 August 1989). The electronic commutation equipment 65 is also arranged to drive the motor continuously to give a spin action, and to drive the spin tub with the agitator, the absence of water from the container 3 results in engagement of teeth 55 and 61 as above described. However, when the agitator is preferably given a slow agitation motion and the container 3 has water in it at least to a predetermined level the flotation force of air in air chamber 51 causes the air chamber spin tub and agitator to rise. The teeth 55 are then raised out of contact with the teeth 61 and the agitator may now move independently of the spin tub and thus may be oscillated back and forth at a desired rate and over any desired angle of rotation to give a washing action without material movement of the spin tub. To provide seals between the drive shaft 11 and the base 29 of the water container, a short cylinder 70 of steel for example (Figure 5) is fixed to the upper frame 32 by a screw 71 and a flange 72 holds the bearing 38 in place. The short cylinder 70 supports a seal 72 against the wall 73 of an aperture in the water container base 29 and a disc 74 holds a further seal 75 against the shaft 11, being reinforced by a backing ring 76. A disc 77 holds a further seal 78 against the shaft 11 reinforced also by a spring 79, the flange 80 sitting within a short cylinder 81 integral with disc. The seal 72, short cylinder 81 disc 74 and seal 75 are integral with each other and the disc 77 seal 78 and flange 80 are integral with each other. Both units are made of Neoprene or other known flexible sealing material. A pump 95 is provided for the purpose of draining the container 3 and the pump 95 is mounted directly about an opening 96 in a lower part of the container 3 and thus a single flexible tube can run from the pump outlet through the back of the cabinet to the user drain connection point. It is to be noted that the bearings 38 and 39 are a slip fit on the drive tube 11 and tightening of the bolt 41 and a cap 91 by a screw 92 clamps both bearings into position. Removal of the rotor securement screw 92 and the bolt 41 can result in the drive tube 11 being removed from above and the motor rotor 16 being removed from below. The motor 2 is removable as a unit after removing also the screws 93 holding the frames 32 and 33 in position. Thus for maintenance purposes this removal can be readily be effected. Furthermore following removal of the securement screw 92, the agitator and agitator hub can be removed and the spin tub assembly then lifted off from above. Thus maintenance is very simple. It is also to be noted that because the spin tub and its contents float during the agitation phase no thrust bearing is required. Also the bearing 53 operates under water and only under low speed condition, that is, the agitator speed relative to the substantially stationary spin tub and therefore the bearing need only be a light duty bearing. An alternative form of interconnection means is provided as follows with reference to Figure 6. The agitator 7 has associated with it a bell 100 both being fixed to the shaft 101 by a bolt 102. The shaft 101 corresponds to the shaft 11 and is driven by an electric motor as above described. Within the bell 100 is a rise and fall member 103 which is a plastics moulding sealably attached by a flexible bellows 105 eg. of neoprene to the outer edge 106 of the plastic member 103 and to the edge of the bell 100. A further flexible bellows 107a is sealably attached to the member 103 and to the hub of the bell 100. The member 103 has prongs or dogs 108 spaced at intervals thereon and such prongs or dogs 108 engage in the spaces between castellations 109 in the bottom of the spin tub 6. A spring (not shown) is provided which exerts a downward force from the hub 108 on the member 103 and the cavity 110 is open to atmosphere through a cross hole or notch 111 in the hub 108 and a series of holes in the shaft or drive tube 101. This arrangement is such that when the container 3 is emptying, the spring moves the member 103 downwardly so that the prongs or dogs 108 engage in the spaces between the castellations and thus the spin tub will move with the agitator and be rotated with that agitator continuously for the purpose of spinning. However, when the container 3 has water in it to a predetermined level the hydrostatic water pressure on the undersurface of the member 103 causes that member to rise against the pressure of the spring air venting through the air holes abovementioned and the prongs or dogs 108 are then raised out of contact with the spin tub and the agitator may now move independently of the spin tub and thus may be oscillated back and forth to give a washing action. In a further alternative arrangement of spin tub to agitator interconnecting means shown in Figure 7 the agitator 7 is combined with a hub 110 fixed by a bolt 111 to a solid splined shaft 112. An air chamber in the form of a bell member 115 is a slidable fit on the shaft 112 and has air entrapment spaces 116 in which air is trapped by rising water in the container 3 when the latter is being filled preparatory to agitation occurring. The bell 115 then acts as a float raising detents or dogs 113 from engagement with castellations 107 as shown on the right hand side of Figure 7 to a disengaged position as shown on the left hand side of Figure 7. At least in the preferred forms the invention provides the following advantages: 1. The electric motor assembly and construction is integrated with the drive system in that a simple shaft and pair of bearings supports the rotor at one end of the agitator and spin tub at the other end advocating the need for separate shafts and bearings for the motor and for the agitator and spin tub drive. 2. The mounting of the stator and the rotor outboard of the lower motor frame enable ready replacement of the stator and/or rotor. 3. The mounting of the electronics in an annular disk associated with the stator of the motor reduces the length of interconnecting wiring and enables a compact factory wired unit to be provided.

Claims: An electric motor (2) for a clothes washing machine having a stator (25), a rotor (15) rotatable exteriorly of said stator and a shaft (11) which carries said rotor, a motor frame (32, 33) having a single pair of spaced apart bearings (38, 39) mounted in said frame (32, 33) in a central disposition relative to said frame (32, 33), said shaft (11) rotatably mounted directly in said bearings (38, 39); said frame (32, 33) having stator locating means (34, 35, 36) arranged to hold an outer cylindrical surface of said stator concentric with said bearings (38, 39); at least one bearing of said pair of bearings (38, 39) spaced at a remote position relative to said stator (25); characterised by electronic commutation equipment (65) for electronically commutating said motor; said stator carrying energisable windings (26) wound directly on poles (8) thereof, said windings adapted to be energised by said electronic commutation equipment (65); said electronic commutation equipment electronically commutating said motor such that said rotor moves in a washing motion wherein the rotor rotates back and forth, or a spin motion wherein said rotor rotates continuously, so that the electric motor can provide both wash and spin motion; said rotor (15) having a hub (19) which mounts said rotor on said shaft (11), a backing ring (16) of a magnetic material, a series of permanent magnets (17) spaced apart on an inner surface of said backing ring (16), a backing ring support (18) rigidly attached to said hub (19) which holds the inner faces of said permament magnets (17) and said backing ring (16) concentric with said shaft (11), and said backing ring (16) and magnets (17) being rotatable exteriorly of said stator windings (26). An electric motor as claimed in claim 1, wherein said stator (25) comprises an annular magnetic core having said poles (8) extending outwardly from the external circumferential surface thereof and spaced apart from each other, said annular core being mounted on said stator locating means (34, 35, 36). An electric motor as claimed in claims 1 or 2, and further comprising insulated mouldings (22, 23) on said poles, said stator windings (26) being wound on said insulated mouldings. An electric motor as claimed in any one of claims 1 to 3 wherein said at least one bearing spaced at a remote position relative to said stator (25) is the bearing opposite the outboard bearing (39) of said single pair of spaced apart bearings (38, 39). An electric motor as claimed in claim 1, wherein said stator (25) is disposed outboard of said frame (32, 33) and with said rotor (15) has a connecting portion (20) between the hub (19) and a rim (21) and said connecting portion (20) being outboard of said stator (25). An electric motor as claimed in claim 1 wherein said stator (25) comprises an annular helix of a magnetic material, said helix having said poles (8) extending outwardly from the circumferential surface of an annulus, said annular helix being mounted on said stator locating means (34, 35, 36). An electric motor as claimed in claim 3, wherein said insulated mouldings comprise a pair of mouldings (22, 23), each said moulding being in the form of an annulus with insulation covering one part of each pole (8), there being a division (24) intermediate of the thickness of each pole (8) between the two mouldings (22, 23). An electric motor for a clothes washing machine as claimed in claim 1 wherein: said stator comprises an annular stator (25) core formed from a strip of magnetic material wound in a helical pattern and having an inner face and an outer face, said strip having pole pieces formed integrally therewith, the pole pieces extending from one edge of said strip and said strip being edgewise wound whereby said pole pieces coincide in stacked groups to form a plurality of poles (8) arranged at equally spaced intervals extending radially outwardly from the outer face of the yoke to oppose the permanent magnets of said exteriorly rotatable rotor; and said energisable stator windings (26) are wound directly on said pole pieces of said stator (25) and adapted to be energized through an electronic commutation circuit (65, 66). An electric motor as claimed in claim 8, wherein the inner face edge of said stator strip opposite the edge thereof from which said pole pieces extend is notched between each adjacent pole (8) so as to reduce the width of said stator strip whereby adjacent poles (8) are connected by a narrow band of strip material (14). An electric motor as claimed in claim 8 or claim 9, and further comprising insulated mouldings (22, 23) on said poles (8), said stator windings being wound on said insulated mouldings (22, 23).

Inventors: BORROWS JOHN GRANT, DUNCAN GERALD DAVID, SHACKLOCK FRANK WHITNEY, SMITH DENNIS EDWARD, THOMAS GRAEME DEWAR, WILLIAMS JOHN JULIAN AUBREY, BORROWS, JOHN GRANT, DUNCAN, GERALD DAVID, SHACKLOCK, FRANK WHITNEY, SMITH, DENNIS EDWARD, THOMAS, GRAEME DEWAR, WILLIAMS, JOHN JULIAN AUBREY
Applicants: FISHER & PAYKEL APPLIANCES LTD, FISHER & PAYKEL APPLIANCES LIMITED
Application year: 1987
Main classification: D06F37
IPC codes: D06F37, H02K29, H02K7