Patent Publication Number: US-2005132760-A1

Title: Washing machine or dryer with a drive integrated on the tub and drum

Description:
BACKGROUND OF THE INVENTION  
      Field of the Invention  
      The invention concerns a drive configuration containing a drum disposed rotatably in a tub. The tub is connected non-rotatably to a stator and the drum is connected non-rotatably to a rotor of an electric motor and the stator is disposed directly on the tub.  
      A direct drive with a segment-shaped stator is known for example from Published, European Patent Application EP 0 350 429 A2. In that configuration a segment-shaped stator is mounted behind the tub. It acts on a rotor configuration which is also disposed behind the tub and which is rigidly connected to the shaft of the drum. Such a drive requires a great deal of space behind the tub. Ultimately that space has to be saved in terms of the length of the drum. Particularly in the case of an inclinedly disposed tub, as has become usual for comfortably and conveniently loading the machine with laundry, that structure is inappropriate for that reason.  
      In another direct drive disclosed in Published, Non-Prosecuted German Patent Application DE 101 46 134 A1 the permanent magnets of the rotor member are fixed on the rear wall of the drum. The stator with its windings projects into the wet space between the rear wall, the drum and the tub and is rigidly connected to the support spider that carries the ball bearing assemblies for the drum shaft. That structure also results in that the drive increases the length of the tub and thus limits the usable space for the drum.  
     SUMMARY OF THE INVENTION  
      It is accordingly an object of the invention to provide a washing machine or dryer with a drive integrated on the tub and drum which overcomes the above-mentioned disadvantages of the prior art devices of this general type, which provides the largest possible usable space for the drum.  
      With the foregoing and other objects in view there is provided, in accordance with the invention, a drive configuration for a washing machine or a dryer. The drive configuration contains an electric motor having a stator and a rotor. A tub is connected non-rotatably to the stator and the stator is disposed directly on the tub at a periphery of the tub. A drum is disposed rotatably in the tub and is connected non-rotatably to the rotor. The rotor is disposed at a periphery of the drum in opposite relationship to the stator.  
      Preferably stator segments (or the stator) are disposed in the center of the tub or in the proximity thereof, more specifically above and/or beneath the drum. The lateral free space between the tub and the washing machine casing that is required for oscillating movements, caused by unbalance in the drum, is not reduced. In conventional washing machines there is free space above and beneath the drum for the stator of the invention. The weight of the stator segment or segments acts near the center point of the drum. That configuration avoids a tilting moment rearwardly, forwardly or laterally of the resiliently suspended system containing the drum-tub and the machine casing. In the invention of the instant application, it is possible to eliminate the compensating weights that are usual nowadays on the tub.  
      In a preferred embodiment the permanent magnets of the rotor member are fixed directly to the outer periphery of the drum and project into the free space between the outside diameter of the drum and the inside diameter of the tub. They are thus at a spacing, of optimum size, from the center of rotation of the drum. The force for the necessary torque remains small due to the long lever arm involved (spacing of the center of rotation relative to the drum periphery). The air gap between the rotor pole and the stator pole can be increased to between 1 and 2 mm without disadvantages in terms of the electrical data of the motor. Assembly of the rotor magnets becomes particularly simple if, in accordance with the invention, they are fixed on an iron ring and the iron ring is pushed on to the drum. In that case the iron ring serves at the same time as a magnetic return for the rotor poles. It is thus also possible to use non-magnetic drums of plastic material or high-grade steel.  
      The stator poles advantageously project through the outer periphery of the tub into the free space between the drum periphery and the tub casing. They are sealed off in relation to the tub by a simple peripherally extending soft seal. The washing solution flows directly around them and for that reason they have to be protected from corrosion by a thin protective layer. The rise in temperature thereof in the washing operation is transmitted directly to the washing solution.  
      The invention provides a drive configuration in which the rotor can act with a large diameter so that the high level of torque that is necessary with washing machines can be implemented. At the same time the waste heat of the stator winding can contribute to heating the washing solution. The invention further affords the effect that the loading on the tub by the weight of the drive is kept centrally in relation to the suspension device of the system: the tub—machine casing, so that even without compensating weights there are no tilting moments of the tub forwardly, rearwardly or laterally.  
      Other features which are considered as characteristic for the invention are set forth in the appended claims.  
      Although the invention is illustrated and described herein as embodied in a washing machine or dryer with a drive integrated on the tub and drum, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.  
      The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a diagrammatic illustration of a drum washing machine from behind with a rear wall removed, with a segment-shaped stator near a center of a longitudinal extent of a tub, according to the invention;  
       FIG. 2  is a diagrammatic, sectional side view of the drum washing machine shown in  FIG. 1 ;  
       FIG. 3  is a sectional view through the drum-tub system in the region of the drive configuration; and  
       FIG. 4  is a sectional side view of the drive configuration shown in  FIG. 3 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Referring now to the figures of the drawing in detail and first, particularly, to  FIGS. 1 and 2  thereof, there are shown simplified views of a drum washing machine with a drum in a slightly inclined position.  
      The washing machine contains a tub  2  and a drum  3  that are oscillatingly suspended in a washing machine casing  1  with springs  4  and friction dampers (spring legs)  5 . The drum  3  is supported in overhung relationship in the star-shaped support spider  7 , in the usual structure. The support spider  7  is secured in a fixed position on the tub  2 . A stator segment  8  is disposed on the tub  2  near the center of the longitudinal extent thereof and projects through the tub  2  into a free space  6 . Rotor magnets  11  are fixed on an outside diameter of the drum under stator poles  10 .  
      By way of an electronic system the stator poles  10  receive voltages that produce a rotary or traveling field and thus cause rotation of the drum. The drive configuration can preferably be in the form of a synchronous motor or in the form of an electrically switched permanent-magnet motor. It is however also possible in a similar manner to envisage all other kinds of motor.  
       FIGS. 3 and 4  show in detail the structure and the configuration of the drive configuration that is in the form of a synchronous motor or an electrically switched dc motor. In this case the stator with the poles  10  is formed by two six-pole segments  8  that are carried on the tub  2  at the top and the bottom. The two stator segments  8  are sealed in relation to the tub  2  with a peripherally extending seal  13 . They project into the free space  6  between the outside diameter of the drum  3  and the inside diameter of the tub  2 . The poles  10  of the segments  8  carry windings  9 . The poles  10  are magnetically excited with the windings  9  in such a way that a rotary field is produced.  
      The rotor member magnets  11  are in the form of permanent magnets. They are carried stationarily on the drum  3  and are held in position by an iron band  12 . The annular iron band  12  can be pre-fabricated with the magnets  11  carried thereon. It is then pushed over the drum into its intended position. The iron band, besides serving to fix the magnets  11 , also serves for the magnetic return for those magnets. The principle of the drive configuration is shown in  FIGS. 3 and 4 . The configuration of the stator segments  8 , their number of poles, the number of poles of the rotor member segments  11  and the configuration of the magnetic circuits of the poles is in accordance with the laws of electric motor design in accordance with the state of the art.  
      This application claims the priority, under 35 U.S.C. § 119, of German patent applications No. 103 60 323.9, filed Dec. 20, 2003, and No. 10 2004 022 979.1, filed May 10, 2004; the entire disclosure of the prior applications is herewith incorporated by reference.