WO2006064860A1

WO2006064860A1 - Motor with double insulation structure and electric apparatus using the same motor

Info

Publication number: WO2006064860A1
Application number: PCT/JP2005/022993
Authority: WO
Inventors: Yasuo Nanbu; Takanori Amaya
Original assignee: Matsushita Electric Industrial Co., Ltd.
Priority date: 2004-12-15
Filing date: 2005-12-08
Publication date: 2006-06-22
Also published as: TWI382634B; TW200629691A; CN101057383A; CN101057383B; JP2008519577A

Abstract

A motor includes a stator having a stator iron-core and a winding insulated from the stator iron-core, and a rotor having a rotary shaft and a rotor iron-core. The rotor iron-core is equipped with resin insulator at the inside, and coupled to the rotary shaft via the resin insulator.

Description

DESCRIPTION

MOTOR WITH DOUBLE INSULATION STRUCTURE AND

ELECTRICAPPARATUS USING THE SAME MOTOR

Technical Field

The present invention relates to a motor having a double -insulation structure and used as a driving source in electrical apparatuses, which basically use water, such as a washing machine, a dish washer/dryer, and a kitchen garbage processor.

Background Art

Washing machines, pumps of dish washers/dryers, and kitchen garbage processors employ motors as their driving sources. An output shaft of those motors works or possibly works in the water, so that a reliable double insulation or grounding insulation is needed to those motors.

Among the motors mounted to the foregoing merchandise, motors such as toroidal-winding motors have been difficult to employ the grounding insulation, so that they have been obliged to employ the double insulation, i.e. windings are insulated from a stator iron-core by resin as basic insulation, then the iron-core is insulated from a rotary shaft as additional insulation. This conventional double insulation is disclosed in, e.g. Japanese Patent Unexamined Publication No. 2003 - 23742.

Fig. 1OA shows a sectional view illustrating a structure of this conventional motor, and Fig. 1OB shows an enlarged view illustrating an area around the rotary shaft of the motor shown in Fig. 1OA. Winding 104 is wound on stator iron-core 102 insulated by resin 103, thereby forming stator 101. Rotary shaft 113 is provided with grooves smaller than an outer diameter of an output section of shaft 113 at around a section where rotor iron-core 112 is to be fixed, and the grooves are filled with insulating resin 117 to be flush with the outer surface of shaft 113. Rotary shaft 113 is press-fitted into the inside of rotor iron-core 112, the inside is provided with aluminum die cast. Rotor 111 is rotatably supported by bearing 105.

Figs. HA and HB show another conventional example, where similar elements to what are shown in Figs. 1OA and 1OB have the same reference marks and the descriptions thereof are omitted. Rotary shaft 113a is provided with insulating resin 117a at around a section where a rotor iron-core is fixed to shaft 113a, meanwhile shaft 113a is straight and does not have grooves. Shaft 113a is press-fitted into the inside of rotor iron-core 112. The aluminum die cast is buried inside iron-core 112.

Both of the structures discussed above use resin to rotary shafts 113 and 113a for insulating the shafts from rotor iron-core 112, so that the double insulation is completed. However, use of the insulating resin increases a cost of the rotary shafts.

Fig. 12 shows a structure of a tooling die for manufacturing the rotary shaft shown in Fig. 1OB. Rotary shaft 123 is set between upper die 121 and lower die 122, and resin is poured from gate 124 for completing the molding. Fig. 13 shows a structure of a tooling die for manufacturing the rotary shaft shown in Fig. HB. Rotary shaft 133 is set between upper die 131 and lower die 132, and resin is poured from gate 134 for completing the molding.

Individual lengths of the shafts thus need independent tooling dies accordingly, so that a cost of tooling dies becomes expensive. An entire rotary shaft must be set in the tooling die, so that the output shaft has a possibility of being scratched at molding. A clearance between the tooling die and the rotary shaft is requisite, so that if the tooling die is not so precisely made, resin burrs are produced sometimes and removal of the burrs is necessary.

Disclosure of Invention A motor of the present invention comprises the following elements: a stator having a stator iron-core and a winding insulated from the iron-core; and a rotor having a rotary shaft and a rotor iron-core of which inside is equipped with a resin insulator, and the rotor iron-core being coupled to the rotary shaft via the resin insulator.

The foregoing structure allows achieving a motor with double insulation in an extremely simple construction, so that an inexpensive and reliable motor is obtainable.

Brief Description of the Drawings

Fig. 1 shows a sectional view illustrating a structure of a motor in accordance with a first embodiment of the present invention.

Fig. 2 shows an enlarged view of an essential part of the motor. Figs. 3A and 3B schematically show manufacturing steps of the motor in accordance with the first embodiment of the present invention.

Figs. 4A - 41 schematically show creeping distances of the motors in accordance with the first embodiment of the present invention.

Fig. 5 shows a sectional view illustrating a step of assembling a rotor of a motor in accordance with a second embodiment of the present invention. Figs. 6A and 6B show sectional views illustrating an assembling of a rotor of a motor in accordance with a third embodiment of the present invention. Figs. 7A and 7B show sectional views illustrating an assembling of a rotor of a motor in accordance with a fourth embodiment of the present invention.

Fig. 8 shows a sectional view illustrating a structure of an electrical apparatus (washing machine) in accordance with a fifth embodiment of the present invention.

Fig. 9 shows a sectional view illustrating a structure of an electrical apparatus (dish washer) in accordance with the fifth embodiment of the present invention. Fig. 1OA shows a sectional view illustrating a structure of a conventional motor.

Fig. 1OB shows an enlarged view illustrating an essential section of the conventional motor shown in Fig. 1OA.

Fig. HA shows a sectional view illustrating a structure of another conventional motor.

Fig. HB shows an enlarged view illustrating an essential section of the conventional motor shown in Fig. HA.

Figs. 12 and 13 schematically show a tooling die for manufacturing the conventional motor.

Detailed Description of Preferred Embodiments

Embodiments of the present invention are demonstrated hereinafter with reference to the accompanying drawings. Embodiment 1 Fig. 1 shows a sectional view illustrating a structure of a motor in accordance with the first embodiment of the present invention. Fig. 2 shows an enlarged view of a rotor of the motor shown in Fig. 1. Stator 11 is formed of stator iron-core 12 and winding 14 wound on iron-core 12 yet insulated by resin 13 from iron-core 12. Rotor 21 is formed of rotor iron-core 22, and aluminum die cast is buried inside iron-core 22 for forming a conductive bar (not shown) as a secondary conductor. Iron-core 22 has resin insulator 27 on its inside, and iron-core 22 is coupled to rotary shaft 23 via resin insulator 27.

Stator 11 includes bearing 15 which rotatably supports rotary shaft 23. Winding 14 of stator 11 generates rotary magnetic field, which acts on the secondary conductor made of aluminum die cast inside rotor 21, thereby producing electromagnetic induction, which then gives specified torque to rotor 21 for rotating. The foregoing motor is thus defined as an induction motor.

In the motor of the present invention, winding 14 is insulated from stator iron-core 12 by resin 13, namely, the motor is provided with basic insulation. On top of this basic insulation, rotor iron-core 22 is insulated from rotary shaft 23 by resin insulator 27, so that double insulation is achieved. Resin insulator 27 can be made of thermoplastic resin (PBT, PET, PP, PE), or thermosetting resin (unsaturated polyester resin). The thermosetting resin is preferable to the thermoplastic resin because it has better mechanical strength and a higher heatproof temperature.

Thickness "h" of resin insulator 27 shown in Fig. 2 is at least 0.4 mm, which complies with the safety standards such as Electrical Appliance Safety Law in Japan. And higher limit of the thickness "h" can be determined suitable for practical use. To be more specific, an inner diameter of rotor iron-core 22 is φ 10, and rotary shaft 23 is a straight shaft having φ 8. This structure keeps the cost of shaft 23 down, and the thickness "h" of resin insulator 27 becomes lmm.

Providing rotor iron-core 22 with aluminum die cast, in general, tends to reduce the inner diameter of the rotor from the one before the aluminum die cast is provided. Steps "j" are thus disposed at both the ends of the inside of iron-core 22. However, since resin insulator 27 is molded in the inside of the rotor, steps "j" can be eliminated for making the inside straight.

Figs. 3A and 3B show a method of manufacturing the foregoing rotor. In Fig. 3A, rotor iron-core 22 is held by upper die 41, lower die 42 and center core

43. Then insulating resin is poured from gate 44, so that resin insulator 27 rigidly adheres to the inside of iron-core 22. As shown in Fig. 3B, rotary shaft

23 is press-fitted into resin insulator 27, thereby completing rotor 21.

A creeping distance between iron-core 22 and shaft 23 is a critical item from the viewpoint of safety. The creeping distance is expressed by dimension 29 in Fig. 2. Electrical Appliance Safety Law, for instance, stipulates that a motor to be mounted to an apparatus driven by 200V needs at least 2mm creeping distance. And higher limit of the dimension 29 can be determined suitable for practical use. Figs. 4A — 41 specifically illustrate how to find this creeping distance.

Resin insulator 27 either projects along the rotary shaft from an end face of rotor iron-core 22 or does not project. Resin insulator 27 is provided with a recess or a protrusion in the shaft direction for increasing the creeping distance.

Fig. 4A shows a case where resin insulator 27a projects along the rotary shaft from an end face of iron-core 22a, and the creeping distance is expressed with reference mark 29a. Fig. 4B shows a case where resin insulator 27b projects along the rotary shaft from an end face of iron-core 22b, and on top of that, resin insulator 27b includes a protrusion, so that the creeping distance is expressed with 29b. Fig. 4C shows a case where resin insulator 27c projects along the rotary shaft from an end face of iron-core 22c, and on top of that, resin insulator 27c includes a recess, so that the creeping distance is expressed with 29c. Fig. 4D shows a case where resin insulator 27d projects along the rotary shaft from an end face of iron-core 22d, and on top of that, resin insulator 27d includes protrusions and recesses, so that the creeping distance is expressed with 29d.

Fig. 4E shows a case where resin insulator 27e does not project along the rotary shaft from an end face of ironxore 22e, so that the creeping distance is expressed with 29e. In this case, the step section needs a greater height in order to keep a necessary creeping distance. Fig. 4F shows a case where resin insulator 27f does not project along the rotary shaft from an end face of iron-core 22f, and insulator 27f includes a protrusion, so that the creeping distance is expressed with 29f. Fig. 4G shows a case where resin insulator 27g does not project along the rotary shaft from an end face of iron-core 22g, and insulator 27g includes a recess, so that the creeping distance is expressed with 29g. Fig. 4H shows a case where resin insulator 27h does not project along the rotary shaft from an end face of iron-core 22h, and insulator 27h includes protrusions as well as recesses, so that the creeping distance is expressed with 29h. Fig. 41 shows a case where resin insulator 27i does not project along the rotary shaft from an end face of iron-core 22i, so that the creeping distance is expressed with 29i. In this case, a chamfered section needs a greater dimension in order to keep a necessary creeping distance.

Embodiment 2

Fig. 5 shows a sectional view illustrating a step of assembling a rotor in accordance with the second embodiment. Rotor iron-core 22 is provided with aluminum die cast at the inside, and resin insulator 27 is disposed further inside iron-core 22. Rotary shaft 24 has knurled section 24a at a joint with insulator 27. Knurled section 24a is formed by pillar filing or double-cut filing. Rotary shaft 24 is press-fitted into resin insulator 27, so that shaft 24 is tightly held by insulator 27. As a result, rotary shaft 24 is prevented from spinning loosely or slipping off.

Embodiment 3 Figs. 6A and 6B individually illustrate a step of putting a rotor iron-core and a rotary shaft together in accordance with the third embodiment. In Fig. 6A, straight rotary shaft 23 and rotor iron-core 22 which is provided with aluminum die cast are set in a tooling die, then insulating resin is poured thereto, so that resin insulator 28a is formed. In Fig. 6B, rotary shaft 25 includes knurled section 25a which is formed by, e.g. pillar filing or double-cut filing. Iron-core 22 provided with aluminum die cast and rotary shaft 25 are set in a tooling die, then insulating resin is poured thereto, so that resin insulator 28b is formed.

Rotor iron-core 22 is integrated to rotary shaft 23 or 25 with insulating resin, so that the iron-core is insulated from the rotary shaft and yet they are put together rigidly. On top of that, the step of press-fitting the rotary shaft into the resin insulator can be eliminated, although this step is needed in the first and the second embodiments.

Embodiment 4

Figs. 7A and 7B show sectional views of rotors in accordance with the fourth embodiment of the present invention. Those rotors are used in a synchronous induction motor, which is a special version of the motor. This motor is equipped with interior permanent magnets. Fig. 7A shows a step of burying flat permanent magnets into plural slots

32 of rotor iron-core 31. Before or after the plural permanent magnets are buried in slots 32, resin insulator 27 is formed, so that the rotor iron-core is positively insulated from the rotary shaft.

Fig. 7B shows a step of burying arc-shaped permanent magnets into plural slots 34 of rotor iron-core 33. Before or after the plural permanent magnets are buried in slots 34, resin insulator 27 is formed, so that the rotor iron-core is positively insulated from the rotary shaft.

The permanent magnets to be buried can be neodymiuπriron-boron magnets, or ferrite magnets (sintered or plastic magnet).

The rotary shaft can undergo the knurling process as discussed in the second embodiment for strengthening the adhesion of the shaft to the resin insulator. The rotary shaft and the rotor iron-core can be integrally formed as discussed in the third embodiment for eliminating a step onward.

Embodiment 5

Examples of electrical apparatuses in accordance with an embodiment of the present invention are demonstrated hereinafter. Fig. 8 shows a sectional view illustrating a structure of a washing machine employing a motor of the present invention.

In Fig. 8, wash and dryer basket 61 (hereinafter referred to as basket 61) is surrounded by water tub 63, and has pulsator (agitating wing) 62 at its bottom. Water tub 63 is mounted with clutch 65 at its bottom. Driving motor 64 is coupled to clutch 65 via a belt, so that rotating force of motor 64 is conveyed to basket 61 or pulsator 62 via clutch 65. Clutch 65 is switched in order to convey the rotating force of motor 64 to pulsator 62 in washing, or to basket 61 in drying. Water tub 63 is supported by outer frame 66 via suspension 67 so that vibration can be damped. Liquid balancer 68 enclosing liquid is fixed to an upper section of basket 61. Water tub 63 is covered with water guard 69 at its top and is equipped with discharging hose-pipe 71 at its bottom. Hose-pipe 71 is equipped with pump motor 70 at its some midpoint. Pump motor 70 works in discharging so that drainage can be done smooth.

An operation of the foregoing washing machine is demonstrated hereinafter. First, in a step of washing, pour cleansing fluid into water tub 63, and agitate the clothes in basket 61 with pulsator 62 so that the cleansing fluid can permeate the clothes and remove soil of the clothes by rubbing. Next, in a step of rinsing, pour the water in water tub 63, and agitate the clothes with pulsator 62 for rinsing. Finally in a step of spin- drying, convey the rotating force of motor 64 to basket 61 by switching clutch 65 for rotating basket 61, so that the clothes are centrifugally dehydrated. The foregoing steps are sequentially controlled so that the steps of washing, rinsing, and spin-drying can be done automatically.

The water produced in the rinsing step and the spin-drying step is discharged through hose-pipe 71 by pump motor 70.

Employment of the double insulation motor in accordance with the present invention to driving motor 64 and/or pump motor 70 allows motor 64 and/or motor 70 to become excellent in water-resistance and have a more positive grounding structure, so that a highly reliable motor is obtainable. As a result, a washing machine in accordance with this fifth embodiment of the present invention becomes more reliable.

Fig. 9 shows a sectional view illustrating a structure of a dish washer employing a motor of the present invention. In Fig. 9, washing unit 81 opens in front (left side in Fig. 9) and includes washing tub 82 therein. Tub 82 opens upward and can be pulled out from washing unit 81 toward the front generally in the horizontal direction. Inside tub 82, dish-basket 84 is disposed for accommodating tableware 83. Tub 82 can be pulled out from the washing unit 81 to the front along rails provided between unit 81 and tub 82.

Inside tub 82, heater 85 is placed for heating the wash water in tub 82. Tub 82 has wash pump 86 at its lower section, and pump 86 sprays the wash water through nozzles 87 for washing tableware 83. Wash pump 86 is driven by pump motor 80. Water feed valve 88 feeds the running water to washing tub 82, and a discharge pump (not shown) discharges the wash water to the outside of tub 82.

Temperature sensor 89 is formed of a thermistor and mounted on a bottom face of tub 82 for sensing a temperature of the wash water in tub 82. Controller 90 receives a signal from sensor 89 for sensing the temperature of the wash water, and controls the temperature of the wash water as well as a temperature in the spin-drying step. Above washing tub 82, inner lid 91 is disposed inside washing unit 81 and yet rigidly mounted to unit 81, and covers the opening of tub 82 when tub 82 is housed in washing unit 81. Seal-packing 92 is further disposed for sealing up the opening of tub 82.

An operation of the foregoing dish washer is demonstrated hereinafter. A user pulls washing tub 82 in front (toward left in Fig. 9), then places tableware 83 in basket 84, and accommodates tub 82 in washing unit 81. Then the user starts the operation. Controller 90 controls the operations of heater 85, wash pump 86, water feed valve 88, and the discharge pump for the dish washer to wash, rinse, and dry tableware 83.

During the washing operation, the wash water attaches to the inside face of lid 91, so that a pull of tub 82 toward the front drops the wash water attaching to lid 91 on the bottom face of washing unit 81, then the dropped water possibly splashes on pump motor 80, which thus needs to be waterproof.

Use of the double insulation motor of the present invention as pump motor 80 is good for this application because of its excellent waterproof feature. The motor also can provide a more positive grounding structure. As a resu.lt, the dish washer of the present invention becomes more reliable.

Industrial Applicability The motor of the present invention includes a stator having a stator iron-core and a winding insulated from the iron-core, and a rotor having a rotary shaft and a rotor iron-core. The rotor iron-core is provided with resin insulator at its inside, and the rotor iron-core is coupled to the rotary shaft via the resin insulator. This structure allows achieving a double insulation motor in an extremely simple structure, so that an inexpensive and reliable motor is obtainable, and electrical apparatuses employing this motor can be available.

Claims

1. A motor comprising: a stator including a stator iron-core and a winding insulated from the iron-coreJ and a rotor including a rotary shaft and a rotor iron-core, wherein the rotor iron-core is equipped with a resin insulator at inside thereof, and the rotary shaft is coupled to the rotor iron-core via the resin insulator.

2. The motor of claim 1 is an induction motor of which rotor iron-core has a conductive bar made of aluminum die cast.

3. The motor of claim 1, wherein the resin insulator has at least 0.4mm thickness between the rotor iron-core and the rotary shaft.

4. The motor of claim 1, wherein the resin insulator protrudes along the rotary shaft from an end face of the rotor iron-core.

5. The motor of claim 1, wherein the resin insulator has one of a recess and a protrusion along the rotary shaft.

6. The motor of claim 1, wherein the rotor iron-core has a step inward at both end faces.

7. The motor of claim 1, wherein the rotor iron-core has a chamfer inward at both end faces.

8. The motor of claim 1 has at least 2mm creeping distance between the rotor iron-core and the rotor shaft.

9. The motor of claim 1, wherein the rotary shaft has a knurled section.

10. The motor of claim 1, wherein the rotary shaft is press-fitted into the rotor iron-core for coupling.

11. The motor of claim 1, wherein the rotor iron-core is integrally formed with the rotary shaft for coupling.

12. The motor of claim 1, wherein the rotor iron-core has a plurality of slots in which a plurality of permanent magnets are buried.

13. An electrical apparatus employing the motor as defined in any one of claims 1 through 12.