JP2010187976A - Drum-type washing machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To permit sufficient adjustment of damping force, in a drum-type washing machine wherein a water tub storing a drum is supported in a vibration isolating way by a suspension using a magnetorheological fluid. <P>SOLUTION: A variation in the viscosity of the magnetorheological fluid 45 produced by a magnetic field caused in a magnetic generator 35 occurs in a groove portion 44 communicatively connecting spaces 42 and 43 on both sides in the axial direction of the magnetic circuit generation section 34 in a cylinder 24, and also occurs in gaps 39 and 40 between the outside peripheries of an upper yoke 36 and a lower yoke 37 of the magnetic circuit generation section 34 and the inside periphery of the cylinder 24, and serves to increase the damping force to the vertical vibration of the water tank. Thus the drum-type washing machine permits the damping force to be sufficiently adjusted as compared with a conventional one which adjusts the damping force only by a variation in the viscosity of the magnetorheological fluid which occurs in a magnetorheological fluid channel equivalent to the groove portion 44. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a drum-type washing machine in which a water tub is supported in a vibration-proof manner by a suspension using a magnetorheological fluid.

  2. Description of the Related Art Conventionally, a drum type washing machine includes a drum for storing laundry so as to be rotatable in a horizontal axis shape inside a water tank for storing washing water. In this drum type washing machine, the vibration during operation is reduced by supporting the water tub with a plurality of suspensions on the bottom plate of the outer box. As this type of suspension, a suspension using a magnetorheological fluid (MR fluid) whose viscosity varies depending on the strength of a magnetic field is known (see, for example, Patent Document 1).

  In the above-mentioned Patent Document 1, a piston rod is inserted into a damper tube, and pistons are provided at two axial positions of the piston rod, respectively. A fluid storage chamber is formed. The damper tube is provided with a magnetism generating device at a portion facing the magnetorheological fluid storage chamber, and the magnetoresistive chamber is divided into two chambers in the axial direction by the magnet generator. Each contains a magnetorheological fluid.

  The magnetic generator is formed by providing a coil on an annular iron core, and generates a magnetic field. This magnetism generator forms a magnetorheological fluid flow path with the piston rod. Further, in the drum type washing machine, a damper tube side spring receiving seat is provided at the piston rod protruding side end portion of the damper tube, and a shaft side spring receiving seat is provided at the protruding end portion of the piston rod. A coil spring is interposed between the seats, and thus the water tank is supported in the outer box by a suspension using a magnetorheological fluid.

  When the water tank vibrates in the vertical direction with the structure in which the water tank is supported in this way, the damper tube also reciprocates in the vertical axis direction along with the expansion and contraction of the coil spring. At this time, as the piston relatively reciprocates up and down in the magnetorheological fluid storage chamber in the damper tube, the magnetorheological fluid flows from one side of the two chambers in the axial direction of the magnetorheological fluid storage chamber to the other side. Go back and forth through the magnetic viscous fluid flow path. Here, a damping force is generated by the viscosity of the magnetorheological fluid, and the amplitude of the water tank is attenuated.

  In this situation, when the coil of the magnetism generator is energized, a magnetic field is generated, the magnetic field is applied to the magnetorheological fluid, and the viscosity of the magnetorheological fluid is increased. As a result, the flow resistance when the magnetorheological fluid passes through the magnetorheological fluid flow path increases, so that the damping force increases. That is, the damping force can be adjusted by energizing the coil of the magnetic generator.

JP 2006-57766 A

  Although the damping force can be adjusted by energizing the coil of the magnetism generator in the one described in Patent Document 1, the damping force is adjusted by passing the magnetorheological fluid through the magnetorheological fluid channel. This is only by changing the flow resistance at the time, and the damping force is not sufficiently adjusted (especially increased).

  The present invention has been made in view of the above-described circumstances. Therefore, the object of the present invention is to sufficiently adjust the damping force in the case where the water tank accommodating the drum is supported by vibration isolation by the suspension using the magnetorheological fluid. To provide a drum-type washing machine.

  In order to achieve the above object, in the drum type washing machine of the present invention, in the drum type washing machine having a suspension that supports and dampens the water tank in which the drum is accommodated, the suspension is disposed inside the cylinder and the cylinder. A fixed bearing, a shaft that is supported so as to be reciprocally movable in the axial direction, and a shaft that is fixed to the shaft and is relatively reciprocally movable in the cylinder. A magnetic circuit generator configured to include a magnetic field generator that variably generates a magnetic field, and yokes made of a magnetic material fixed on both sides in the axial direction of the magnetic field generator, and the magnetic circuit generator and the shaft And a groove that communicates the space on both sides in the axial direction of the magnetic circuit generator in the cylinder, and the magnetic circuit generator in the cylinder. Space on both sides in the direction, the groove, a magnetorheological fluid filled in a gap between the outer peripheral surface of the magnetic circuit generator and the inner peripheral surface of the cylinder, and located below the magnetic circuit generator A seal member fixed inside the cylinder and in close contact with the outer periphery of the shaft to prevent leakage of the magnetorheological fluid is provided (invention of claim 1).

  According to the above means, the change in the viscosity of the magnetorheological fluid due to the generation of the magnetic field in the magnetism generator is caused by the groove portion (the channel for the magnetorheological fluid) that communicates the space on both sides in the axial direction of the magnetic circuit generator inside the cylinder. And a gap between the outer peripheral surface of the upper yoke and the lower yoke of the magnetic circuit generating portion and the inner peripheral surface of the cylinder, both of which work to increase the damping force against the vertical vibration of the water tank. Thus, the damping force can be adjusted more sufficiently than that of Patent Document 1 in which the damping force is adjusted only by the change in the viscosity of the magnetorheological fluid generated in the magnetorheological fluid flow path.

The longitudinal cross-sectional view of the state before a driving | operation of the principal part which shows 1st Example of this invention Cross-sectional view along line II-II in FIG. Cross-sectional view along line III-III in FIG. Partial enlarged vertical sectional view for explaining the operation of the main part Longitudinal section of the main part during operation Longitudinal side view of the entire drum type washing machine FIG. 3 equivalent view showing a second embodiment of the present invention. FIG. 1 equivalent view showing a third embodiment of the present invention. FIG. 1 equivalent view showing a fourth embodiment of the present invention. FIG. 3 equivalent view showing a fifth embodiment of the present invention. FIG. 2 equivalent diagram showing a sixth embodiment of the present invention.

A first embodiment (first embodiment) of the present invention will be described below with reference to FIGS.
First, FIG. 6 shows the overall structure of the drum type washing machine, and the outer box 1 is an outer shell. A laundry entrance / exit 2 is formed at a substantially central portion of the front portion (right side in FIG. 6) of the outer box 1, and a door 3 for opening and closing the entrance / exit 2 is provided. In addition, an operation panel 4 is provided at the upper part of the front surface of the outer box 1, and a control device 5 for operation control is provided on the back side (inside the outer box 1).

A water tank 6 is disposed inside the outer box 1. The aquarium 6 has a horizontal cylindrical shape whose axial direction is front and rear (right and left in FIG. 6), and is tilted forward by a pair of left and right (only one shown) suspensions 7 on the bottom plate 1a of the outer box 1. It is elastically supported in the shape. The detailed structure of the suspension 7 will be described later.
A motor 8 is attached to the back of the water tank 6. In this case, the motor 8 is composed of, for example, a DC brushless motor, and is an outer rotor type. A rotating shaft (not shown) attached to the center of the rotor 8a is connected to the inside of the water tank 6 via a bearing bracket 9. Is inserted.

  A drum 10 is disposed inside the water tank 6. This drum 10 also has a horizontal cylindrical shape with the front and rear being axially attached. By attaching it to the tip of the rotating shaft of the motor 8 at the center of the rear part, the drum 10 has a forwardly inclined shape coaxial with the water tank 6. I support it. As a result, the drum 10 is rotated by the motor 8, so that the drum 10 is a rotating tank and the motor 8 functions as a drum driving device that rotates the drum 10.

  A large number of small holes 11 (only a part is shown) are formed in the peripheral side portion (body portion) of the drum 10 over the entire area. Each of the drum 10 and the water tub 6 has openings 12 and 13 on the front surface thereof, and the laundry entrance 2 is connected to the opening 13 of the water tub 6 through an annular bellows 14. . As a result, the laundry entrance / exit 2 is connected to the inside of the drum 10 via the bellows 14, the opening 13 of the water tub 6, and the opening 12 of the drum 10.

  A drain pipe 16 is connected to the rear part of the bottom, which is the lowest part of the water tank 6, via a drain valve 15. A drying unit 17 is disposed above and in front of the back of the water tank 6. The drying unit 17 includes a dehumidifier 18, a blower 19, and a heating device 20, and dehumidifies the air in the water tank 6, and then heats the air to return it to the water tank 6. The laundry is supposed to be dried.

  Here, the detailed structure of the suspension 7 will be described. As shown in FIGS. 6 and 1, the suspension 7 includes a shaft 22 attached to a mounting plate 21 included in the bottom plate 1 a of the outer box 1, and a cylindrical cylinder 24 attached to a mounting plate 23 included in the water tank 6. And is composed. Specifically, a connecting portion 22a is provided at the lower end of the shaft 22, and the connecting portion 22a is fastened to the mounting plate 21 of the bottom plate 1a with a nut 26 via an elastic seat plate 25 such as rubber. 22 is attached to the mounting plate 21.

  On the other hand, a connecting member 27 is provided at the upper end portion of the cylinder 24, and the connecting member 27 is fastened to the mounting plate 23 of the water tank 6 by the nut 29 via the elastic seat plate 28 and the like. 6 and the water tank 6 and the cylinder 24 are configured to vibrate in the vertical direction (axial direction).

  An upper bearing 30 is press-fitted and fixed inside a position slightly below the upper end of the cylinder 24, and the inside of the cylinder 24 between the upper bearing 30 and the connecting member 27 is a cavity 31. , So that air accumulates. On the other hand, a lower bearing 32 is press-fitted and fixed inside the lower end portion of the cylinder 24. The lower bearing 32 and the upper bearing 30 are made of, for example, sintered oil-impregnated metal (so-called bearing alloy), and a seal member 33 is press-fitted and fixed inside the cylinder 24 at a position immediately above the lower bearing 32. Yes.

  On the other hand, the upper portion of the shaft 22 penetrates the lower bearing 32, the seal member 33, and the upper bearing 30 so as to be capable of relatively reciprocating in the axial direction, and the upper end portion reaches the cavity 31, and in this state, The entire shaft 22 is supported by an upper bearing 30 and a lower bearing 32. A seal member 33 is in close contact with the outer peripheral surface of the shaft 22.

  A magnetic circuit generator 34 is provided in advance between the upper bearing 30 and the seal member 33 of the shaft 22. The magnetic circuit generator 34 includes a magnetic field generator 35, and an upper yoke 36 and a lower yoke 37. The magnetic field generator 35 includes a bobbin 35a and a coil 35b wound around the bobbin 35a. Yes. The magnetic field generator 35 has its bobbin 35a fitted on the shaft 22 and fixed to the shaft 22. The gap between the outer peripheral surface of the magnetic field generator 35 and the inner peripheral surface of the cylinder 24 is shown in FIG. As can also be seen, there is a predetermined gap 38 which allows for relative axial movement of the magnetic field generator 35 relative to the cylinder 24.

  The upper yoke 36 is press-fitted to the shaft 22 and fixed to the bobbin 35 a on the upper surface of the magnetic field generator 35, and the lower yoke 37 is also press-fitted to the shaft 22 on the lower surface of the magnetic field generator 35. Then, it is fixed to the bobbin 35a. As shown also in FIG. 3, predetermined gaps 39 and 40 exist between the outer peripheral surfaces of the upper yoke 36 and the lower yoke 37 and the inner peripheral surface of the cylinder 24 (FIG. This makes it possible to move the upper yoke 36 and the lower yoke 37 relative to the cylinder 24 relative to the cylinder 24 along with the magnetic field generator 35.

  When the coil 35b of the magnetic field generator 35 is energized with the above configuration, the magnetic circuit 41 of the shaft 22, the upper yoke 36, the gap 39, the cylinder 24, the gap 40, the lower yoke 37 and the shaft 22 is generated as shown in FIG. Thus, the magnetic circuit generator 34 generates the magnetic circuit 41. Spaces 42 and 43 exist on both sides (up and down) in the axial direction of the magnetic circuit generator 34 in the cylinder 24, respectively.

  A groove 44 is provided between the magnetic circuit generator 34 (magnetic field generator 35, upper yoke 36, lower yoke 37) and the shaft 22. The groove 44 communicates both the spaces 42 and 43. In this case, the shaft 22 is cut and formed in the shaft 22, but may be formed in the magnetic circuit generator 34.

The spaces 42 and 43, the groove 44, and the gaps 39, 38, and 40 are filled with a magnetorheological fluid (MR fluid) 45. The magnetorheological fluid 45 has a viscosity characteristic that changes according to the strength of the magnetic field (magnetic field). For example, the magnetorheological fluid 45 is obtained by dispersing ferromagnetic particles such as iron and carbonyl iron in oil, and is applied with a magnetic field. Then, the apparent viscosity increases because the ferromagnetic particles form chain clusters. The sealing member 33 prevents the leakage of the magnetorheological fluid 45.
The magnetic circuit generator 34 generates a magnetic field (magnetic circuit 41) corresponding to the current value flowing through the coil 35b and controls the viscosity of the magnetorheological fluid 45. The generated magnetic field depends on the current value. It is variable, and the viscosity of the magnetorheological fluid 45 can be variably controlled.

  A shaft-side spring seat 46 is fitted and fixed to the lower portion of the shaft 22. The cylinder side spring receiving seat 47 is fitted and fixed to the lower end portion of the cylinder 24 so as to be reciprocally movable in the axial direction relative to the lower end portion of the cylinder 24. A coil spring 48 composed of a compression coil spring surrounding the shaft 22 and the cylinder-side spring receiving seat 47 is mounted between the spring receiving seats 46 and 47 so that the suspension 7 can be expanded and contracted. And a bottom plate 1a of the outer box 1 so that the water tank 6 is supported on the bottom plate 1a of the outer box 1 in a vibration-proof manner.

Next, the operation of the above configuration will be described.
When the control device 5 starts operation based on the operation of the operation panel 4, the water tank 6 vibrates mainly in the vertical direction as the drum 10 containing the laundry is rotationally driven. In response to the vertical vibration of the water tank 6, in the suspension 7, the cylinder 24 integrally connected to the water tank 6 includes a connecting member 27, an upper bearing 30, a seal member 33, a lower bearing 32, and a cylinder side spring seat. 47, the coil spring 48 is expanded and contracted to vibrate around the shaft 22 in the vertical direction. FIG. 5 shows one state of the suspension 7 during the operation of the washing machine, and the cylinder 24 is lowered with the above components from the state before the operation shown in FIG.

  As described above, when the cylinder 24 vibrates in the vertical direction with the above-described parts, the volume changes so that the volumes of the spaces 42 and 43 are interchanged accordingly. For this reason, the magnetorheological fluid 45 in the spaces 42 and 43 flows through the groove 44. Here, a damping force is generated by the viscosity of the magnetorheological fluid 45, and the amplitude of the water tank 6 is attenuated. Further, since the magnetorheological fluid 45 is also present in the gaps 39, 38 and 40 between the magnetic circuit generator 34 and the cylinder 24, it is also attenuated by the viscosity of the magnetorheological fluid 45 in these gaps 39, 38 and 40. A force is generated and the amplitude of the water tank 6 is attenuated.

  At this time, when the coil 35b of the magnetic field generator 35 is energized, the magnetic circuit 41 described above (see FIG. 3) is generated, whereby magnetic flux passes from the shaft 22 to the upper yoke 36, and from the lower yoke 37 to the shaft. Magnetic flux passes to 22. At that time, a part of the magnetic flux passes through the groove 44 between the magnetic circuit generator 34 and the shaft 22 at a portion corresponding to the upper yoke 36 and the lower yoke 37. Further, the magnetic flux passes from the upper yoke 36 across the gap 39 to the cylinder 24, and the magnetic flux passes from the cylinder 24 across the gap 40 to the lower yoke 37.

  Among these, in the former, when a magnetic flux passes through the groove part 44, a magnetic field is given to the magnetorheological fluid 45 which distribute | circulates the groove part 44 as mentioned above, and the viscosity of the magnetorheological fluid 45 increases. Thereby, the flow resistance when the magnetorheological fluid 45 passes through the groove portion 44 is increased, and the damping force against the vertical vibration of the water tank 6 is increased.

On the other hand, in the latter case, the magnetic flux passes through the gaps 39 and 40, whereby a magnetic field is applied to the magnetorheological fluid 45 existing in the gaps 39 and 40, and the viscosity of the magnetorheological fluid 45 increases. As a result, shear stress is generated on the sliding surfaces of the cylinder 24, the upper yoke 36, and the lower yoke 37, and the frictional resistance is increased. Therefore, the damping force with respect to the vertical vibration of the water tank 6 also increases.
In addition, about control of the damping force with respect to the vertical vibration of the aquarium 6, the displacement of the aquarium 6 at the time of resonance and the transmission of force to the bottom plate 1a can be reduced by increasing the damping force at the start of the resonance of the aquarium 6. By reducing the damping force during high-speed rotation of the drum 10 after passing through resonance, it is possible to reduce the transmission of force to the bottom plate 1a during high-speed dewatering.

  Thus, in the drum type washing machine having the above-described configuration, the change in the viscosity of the magnetorheological fluid 45 caused by causing the magnetism generator 35 to generate a magnetic field is the space on both sides in the axial direction of the magnetic circuit generator 34 inside the cylinder 24. In addition to the grooves 44 formed in communication with the grooves 42 and 43, gaps 39 and 40 are also formed between the outer peripheral surfaces of the upper yoke 36 and the lower yoke 37 of the magnetic circuit generator 34 and the inner peripheral surface of the cylinder 24. When the viscosity of the magnetorheological fluid 45 in the groove 44 changes, the flow resistance when the magnetorheological fluid 45 passes through the groove 44 increases, and the damping force against the vertical vibration of the water tank 6 increases. With the change in the viscosity of the magnetorheological fluid 45 at 39 and 40, the frictional resistance of the sliding surfaces of the cylinder 24, the upper yoke 36, and the lower yoke 37 increases, and the damping force against the vertical vibration of the water tank 6 increases. Thus, in the drum type washing machine having the above-described configuration, the vertical vibration of the water tank 6 is sufficiently higher than that of Patent Document 1 in which the damping force is adjusted only by the change in the viscosity of the magnetorheological fluid generated in the channel for the magnetorheological fluid. The damping force can be adjusted.

7 to 11 show second to sixth examples (second to sixth embodiments) of the present invention, and the same parts as those of the first example are the same as those of the first example. The description will be omitted with reference numerals, and only different parts will be described.
[Second Embodiment]
In the second embodiment shown in FIG. 7, a plurality of groove portions 44 (two in the illustrated example) are provided and may be changed in this way.

[Third embodiment]
In the third embodiment shown in FIG. 8, it is located above the magnetic circuit generator 34, which is the opposite side to the side where the seal member 33 is present (just below the upper bearing 30), and inside the cylinder 24, the inner circumference A sealing member 51 whose surface is in contact with the outer peripheral surface of the shaft 22 and whose outer peripheral surface is in contact with the inner peripheral surface of the cylinder 24 is provided. The sealing member 51 is made of a member that does not allow the magnetorheological fluid 45 to pass through, and reciprocates integrally with the cylinder 24 on the outer periphery of the shaft 22.

  By doing so, the axial seal dimension on the side opposite to the side where the seal member 33 exists can be increased by the upper bearing 30 and the sealing member 51, and particularly from the cavity 31 above the upper bearing 30. By preventing the intrusion of air, it is possible to avoid a decrease in attenuation performance due to the fact that the magnetorheological fluid 45 around the magnetic circuit generator 34 contains air.

[Fourth embodiment]
In the fourth embodiment shown in FIG. 9, a lower bearing 32, which is a bearing on the seal member 33 side, is provided on the magnetic circuit generator 34 side from the seal member 33.

By doing so, the lower bearing 32 can be lubricated by being brought into contact with the magnetorheological fluid 45. In particular, during the dehydration operation, in the high-speed rotation range of the drum 10 after passing through the resonance point, the greater the damping force against the vertical vibration of the water tank 6, the greater the propagation of vibration to the floor. In such a case, although the power supply to the coil 35b of the magnetic field generator 35 is reduced or eliminated to reduce the damping force, the mechanical frictional force is not lost and the damping force is generated. Therefore, if the lower bearing 32 is lubricated with the magnetorheological fluid 45 as in the fourth embodiment, the mechanical frictional force can be reduced, the propagation of vibration to the floor can be reduced, and vibration and noise can be reduced. Can be reduced.
Also in this case, the sealing member 51 in the third embodiment is provided in the same manner as the third embodiment.

[Fifth embodiment]
In the fifth embodiment shown in FIG. 10, gaps 39 and 40 between the outer peripheral surfaces of the upper yoke 36 and the lower yoke 37 and the inner peripheral surface of the cylinder 24 (FIG. 10 shows the gap 39 as a representative). The radial cross-sectional area Sa is made smaller than the radial cross-sectional area Sb of the groove 44 (Sa <Sb).
By doing so, it becomes difficult for the magnetorheological fluid 45 to flow from the groove 44 in the gaps 39 and 40, and the frictional resistance between the outer peripheral surface of the upper yoke 36 and the lower yoke 37 and the inner peripheral surface of the cylinder 24 is increased. Since it can ensure, the damping performance with respect to the vertical vibration of the water tank 6 can be improved.

[Sixth embodiment]
In the sixth embodiment shown in FIG. 11, the radial sectional area Sc of the gap 38 between the outer peripheral surface of the magnetic field generator 35 and the inner peripheral surface of the cylinder 24 is made smaller than the radial sectional area Sb of the groove portion 44. (Sc <Sb).
By doing so, it becomes difficult for the magnetorheological fluid 45 to flow from the groove portion 44 in the gap 38, and accordingly, it becomes difficult for the magnetorheological fluid 45 to flow from the groove portion 44 even in the gaps 39 and 40. Since the high frictional resistance between the outer peripheral surface of 37 and the inner peripheral surface of the cylinder 24 can be ensured, the damping performance against the vertical vibration of the water tank 6 can be improved.

  In addition, the present invention is not limited to the embodiments described above and shown in the drawings, and can be implemented with appropriate modifications without departing from the scope of the invention.

  In the drawings, 6 is a water tank, 7 is a suspension, 10 is a drum, 22 is a shaft, 24 is a cylinder, 30 is an upper bearing, 32 is a lower bearing, 33 is a seal member, 34 is a magnetic circuit generator, and 35 is a magnetic field generator. , 36 is an upper yoke, 37 is a lower yoke, 38 to 40 are gaps, 42 and 43 are spaces, 44 is a groove, 45 is a magnetorheological fluid, 51 is a sealing member, and Sa is an outer peripheral surface of the upper yoke and the lower yoke. The radial sectional area of the gap between the inner peripheral surface of the cylinder, Sb is the radial sectional area of the groove, and Sc is the radial sectional area of the gap between the outer peripheral surface of the magnetic field generator and the inner peripheral surface of the cylinder. Show.

Claims (5)

In a drum-type washing machine having a suspension for vibration-proofing a water tank containing a drum,
The suspension,
A cylinder,
A bearing fixed inside the cylinder;
A shaft supported through the bearing so as to be relatively reciprocally movable in the axial direction;
A magnetic field generator fixed to the shaft and capable of relatively reciprocating in the axial direction inside the cylinder and variably generating a magnetic field, and a magnetic material fixed to both sides in the axial direction of the magnetic field generator A magnetic circuit generator configured to have a yoke;
A groove that is provided between the magnetic circuit generator and the shaft, and communicates the space on both sides in the axial direction of the magnetic circuit generator in the cylinder;
Magnetorheological fluid filled in the space between the axial sides of the magnetic circuit generator inside the cylinder, the groove, and the gap between the outer peripheral surface of the magnetic circuit generator and the inner peripheral surface of the cylinder;
A seal member positioned below the magnetic circuit generator and fixed inside the cylinder and in close contact with the outer peripheral surface of the shaft to prevent leakage of the magnetorheological fluid. Drum-type washing machine.   2. A sealing member located above the magnetic circuit generator and provided inside the cylinder, wherein the inner peripheral surface is in contact with the outer peripheral surface of the shaft and the outer peripheral surface is in contact with the inner peripheral surface of the cylinder. The drum type washing machine as described.   2. The drum type washing machine according to claim 1, wherein the seal member side bearing is provided closer to the magnetic circuit generator than the seal member.   2. The drum type washing machine according to claim 1, wherein a radial sectional area of a gap between an outer peripheral surface of the yoke and an inner peripheral surface of the cylinder is smaller than a radial sectional area of the groove portion.   The drum type washing machine according to claim 1, wherein a radial cross-sectional area of a gap between the outer peripheral surface of the magnetic field generator and the inner peripheral surface of the cylinder is smaller than a radial cross-sectional area of the groove portion.

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