Drum-type washing machine

Abstract

 In a drum-type washing machine (1), a lower (25) cushioning member or an upper cushioning member (15) thereof includes a liquid-filled cushion rubber attached to the outer periphery of a supporting shaft (23). This structure exerts a damping force in the directions in which the supporting shaft rotates, or in precession motion, and effectively damps and suppresses whirling vibrations of a water tank (3) unit thereof, at the start of spin-drying operation.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The present invention relates to a drum-type washing machine in which a rotary drum for containing laundry is rotated to perform washing, rinsing, and spin-drying steps.

2. Background art

[0002] Fig. 6 is a sectional view showing a support structure of a water tank unit in a conventional drum-type washing machine 1. With reference to Fig. 6, water tank unit 5 includes rotary drum 2 housed in water tank 3, and rotating shaft 2a of rotary drum 2 is journaled in bearing 6 disposed on the back face of water tank 3. Further, motor 7 for driving the drum is coupled to rotating shaft 2a. Water tank unit 5 is disposed in washing machine body 8 to be angled slightly upward. The weight of the water tank unit is supported by a horizontal pair of vibration-proof dampers 9 fixed to base 14 of washing machine body 8. The water tank unit is resiliently supported by first coil spring 10 and second coil spring 10a stretched to the front face and back face of washing machine body 8, respectively.

[0003] Fig. 7 is a drawing showing a structure of a vibration-proof damper in the conventional drum-type washing machine. With reference to Fig. 7, vibration-proof damper 9 includes oil damper mechanism 11 having a cylinder filled with oil, and coil spring mechanism 12 disposed coaxially with respect to oil damper mechanism 11. Supporting shaft 13 is fixed to the bottom end of oil damper mechanism 11, and coil spring mechanism 12 is disposed along the outer periphery of the supporting shaft. The supporting shaft is fixed to base 14 of washing machine body 8 via cushioning member 15. Second supporting shaft 13a constituting oil damper mechanism 11 is fixed to lower support bracket 16 fixed to a lower portion of water tank 3, via cushioning member 15.

[0004] In the above structure, rotary drum 2 is disposed in water tank unit 5 so that the rotation center axis thereof is in the horizontal direction or a direction inclined therefrom. Thus, in the spin-drying step performed by rotating rotary drum 2, the laundry in rotary drum 2 is biased downward and unbalanced.

[0005] The unbalanced laundry in rotary drum 2 causes large vibrations in water tank unit 5 that houses rotary drum 2. To suppress such vibrations caused by rotation of rotary drum 2, a technique for introducing vibration-proof damper 9 having a large damping coefficient and adding a weight for suppressing vibrations is disclosed in Japanese Patent Unexamined Publication No. 06-327892.

[0006] Another method is disclosed in Japanese Patent Unexamined Publication No. 2005-137643. In this method, water tank unit 5 is supported by vibration-proof dampers 9 from the downward direction in a position closer to the front face than the gravity center position, the upper portion of water tank unit 5 is resiliently urged to the front side by first coil spring 10, and the lower portion of water tank unit 5 is resiliently urged to the back side by second coil spring 10a.

[0007] However, each of the above conventional structures has a large number of components. For instance, the addition of the weight for suppressing vibrations increases the total weight of the drum-type washing machine and thus the labor hour for transportation, which leads to cost increase. A space for stretching the coil spring is also necessary.

[0008] When the vibration of the water tank unit is reduced simply by supporting the water tank unit using vibration-proof damper 9 having a large damping coefficient, the vibration transmissibility to washing machine body 8 in the steady state (at rotational speeds of approximately 800 to 1,200 r/min) of spin-drying operation is increased and thus the vibration of the washing machine body is increased.

[0009] Further, after the rotation for spin-drying is started, water tank unit 5 generates whirling vibrations when the drum rotates at rotational speeds (equal to the resonance frequencies of water tank unit 5) up to approximately 300 r/min, at the start of spin-drying operation. Particularly in such whirling vibrations, conventional vibration-proof damper 9 can damp the simple, vertical vibrations, i.e. oscillations as shown by the arrow A in Fig. 7, made by water tank unit 5. However, when the unbalanced laundry distributed in the front and rear portions in rotary drum 2 causes vibrations imparting rotational motion with respect to the gravity center G, i.e. precession oscillations as shown by the arrow B or C in Fig. 7, sufficient damping effects in the moving directions cannot be obtained. Thus, abnormal vibrations of water tank unit 5 can generate an abnormal sound, or contact of the water tank unit with other members can cause damage.

SUMMARY OF THE INVENTION

[0010] The present invention provides a drum-type washing machine in which vibration transmission to a washing machine body thereof in the steady state of spin-drying operation is suppressed, and whirling vibrations of a water tank unit thereof at the start of the spin-drying operation are effectively reduced without any additional component or weight.

[0011] The drum-type washing machine includes the following elements: the water tank unit that houses a drum for containing laundry so that the drum is rotatable therein, and is resiliently supported in the washing machine body; a motor for rotating the drum; a damper mechanism that resiliently supports the water tank unit thereunder and damps vibrations; a supporting shaft disposed coaxially with respect to the damper mechanism, and a coil spring mechanism disposed around the supporting shaft; a lower cushioning member for fixing the bottom end of the damper mechanism to a base of the washing machine body; and an upper cushioning member for fixing the top end of the damper mechanism to a lower portion of the water tank unit. At least one of the lower cushioning member and the upper cushioning member includes a liquid-filled cushion rubber attached to the outer periphery of the supporting shaft.

[0012] The cushioning member includes a liquid-filled cushion rubber. Thus, this structure can ensure a sufficient damping force in the directions in which the supporting shaft rotates (tilts down), and in precession motion where the damping force of the vibration-proof damper is not easily obtainable, and effectively damp and suppress the whirling vibrations of the water tank unit. Further, this structure can also suppress the vibration transmission to the washing machine body in the steady state of the spin-drying operation where the water tank mostly makes vertical motion, while suppressing the whirling vibrations of the water tank unit at the start of the spin-drying operation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] 

Fig. 1 is a drawing showing a structure of a vibration-proof damper in a drum-type washing machine in accordance with a first exemplary embodiment of the present invention.

Fig. 2 is a drawing showing an operation of the vibration-proof damper in the drum-type washing machine in accordance with the first exemplary embodiment of the present invention.

Fig. 3 is a drawing showing a structure of a vibration-proof damper in a drum-type washing machine in accordance with a second exemplary embodiment of the present invention.

Fig. 4 is a graph showing the relation between dissipation factors and vibration values in the drum-type washing machine in accordance with the second exemplary embodiment of the present invention.

Fig. 5A is a drawing showing a partial structure of a vibration-proof damper in a drum-type washing machine in accordance with a third exemplary embodiment of the present invention.

Fig. 5B is a drawing showing an operation of the vibration-proof damper in the drum-type washing machine in accordance with the third exemplary embodiment of the present invention.

Fig. 6 is a sectional view showing a support structure of a water tank unit in a conventional drum-type washing machine.

Fig. 7 is a drawing showing a structure of a vibration-proof damper in the conventional drum-type washing machine.

DETAILED DESCRIPTION OF THE INVENTION

[0014] A drum-type washing machine of the present invention includes the following elements: i) a drum that has a rotation center axis in substantially a horizontal direction, contains laundry, and makes rotary motion; ii) a water tank unit that houses the drum so that the drum is rotatable therein, and is resiliently supported in a body of the washing machine; iii) a motor for rotating the drum; iv) a damper mechanism that resiliently supports the water tank unit thereunder and damps vibrations; v) a supporting shaft disposed coaxially with respect to the damper mechanism, and a coil spring mechanism disposed around the supporting shaft; vi) a lower cushioning member for fixing the bottom end of the damper mechanism to a base of the washing machine body; and vii) an upper cushioning member for fixing the top end of the damper mechanism to a lower portion of the water tank unit. At least one of the lower cushioning member and the upper cushioning member includes a liquid-filled cushion rubber attached to the outer periphery of the supporting shaft. With this structure, the viscosity of the flowing liquid filled in the rubber can damp whirling of the water tank unit including complex motion at the start of spin-drying operation. Thus, vibrations can be reduced.

[0015] In the drum-type washing machine of the present invention, each of the upper cushioning member and the lower cushioning member is made of a rubber material having vibration damping characteristics in which a dissipation factor of tanδ = 0.7 ± 0.2. The use of such a material allows setting of vibration values at which the whirling of the water tank unit at the start of spin-drying operation does not affect the components thereof, and an allowable vibration limit of the washing machine body. Thus, worsened vibrations of the body and the whirling of the water tank unit can be suppressed at the same time.

[0016] The drum-type washing machine of the present invention further includes a first cushioning member on the inner peripheral side adjacent to the supporting shaft of the vibration-proof damper and a second cushioning member on the outer peripheral side of the first cushioning member. The second cushioning member on the outer peripheral side has a larger dissipation factor or a larger hardness than the first cushioning member on the inner peripheral side. With this structure, the larger dissipation factor on the outer side can work only when the water tank unit is in the directions in which the supporting shaft largely rotates (tilts down), or in precession motion.

[0017] Hereinafter, a description is provided of exemplary embodiments of the present invention, with reference to the accompanying drawings. The present invention is not limited to the exemplary embodiments.

FIRST EMBODIMENT

[0018] Fig. 1 is a drawing showing a structure of a vibration-proof damper in a drum-type washing machine in accordance with the first exemplary embodiment of the present invention. The schematic structure of the drum-type washing machine other than the vibration-proof damper is identical with that of the conventional example shown in Fig. 6.

[0019] With reference to Fig. 1, vibration-proof damper 20 includes oil damper mechanism 21 having a cylinder filled with oil, and coil spring mechanism 22 disposed coaxially with respect to oil damper mechanism 21. Supporting shaft 23 is fixed to the bottom end of oil damper mechanism 21 and coil spring mechanism 22 is disposed along the outer periphery of the supporting shaft. The supporting shaft is fixed to base 14, i.e. the fixed side of washing machine body 8, via liquid-filled lower cushioning member 25. Second supporting shaft 23a constituting oil damper mechanism 21 is fixed to lower support bracket 16, i.e. the oscillation side fixed to a lower portion of water tank 3, via cushioning member 15 made of a rubber material or the like.

[0020] Liquid-filled cushion rubber 26 is made of an elastic body formed into a doughnut shape. Liquid-filled lower cushioning member 25 includes cushion rubber 26, and viscous oil 27 filling a hollow portion thereof.

[0021] A description is provided of the operation of the above structure. At the start of spin-drying operation at rotational speeds up to approximately 300 r/min after the spin-drying step is started, resonance frequencies in six degrees of freedom (along three translational axes and in three rotational directions around respective axes) are generated around the gravity center in water tank unit 5 resiliently supported. The respective resonance frequencies combine with each other and cause complicated behavior. In general, a large vibration mode mainly causing pitching (vertical rotation mode) is generated, at rotational speeds in the vicinity of approximately 250 r/min, for example.

[0022] In such a vibration mode, lower support bracket 16 on the oscillation side makes little vertical oscillation, and makes motion in the directions in which supporting shafts 23 and 23a rotate (tilt down), precession motion in a circular or elliptic shape as shown by the arrow C or B, respectively, or complex oscillations in combination of these movements.

[0023] Hereinafter, a description is provided of the operation and advantage of the first exemplary embodiment.

[0024] Fig. 2 is a drawing showing an operation of the vibration-proof damper in the drum-type washing machine in accordance with the first exemplary embodiment of the present invention. With reference to Fig. 2, a description is provided of the operation of liquid-filled cushion rubber 26 and viscous oil 27.

[0025] When tilting oscillation as shown by the arrow B or C in Fig. 1 is generated in lower support bracket 16 on the water tank unit side, supporting shaft 23 tilts by an angle of θ. At this time, liquid-filled cushion rubber 26 elastically deforms. The sectional shape of cushion rubber 26 that has been bilaterally symmetrical deforms to have different shapes in left space 27a and right space 27b. At this time, inside viscous oil 27 flows horizontally or vertically. Thus, the flow resistance caused by the viscosity exerts damping action, which damps and suppresses the motion of supporting shaft 23 in the tilting direction.

[0026] Thus, with liquid-filled cushion rubber 26, a sufficient damping force can be ensured in the rotational directions, and whirling vibrations of water tank unit 5 can be effectively suppressed.

[0027] The spring constants and damping coefficients in the rotational and translational directions of liquid-filled cushion rubber 26 can be optionally selected and set for the purposes, according to the viscosity of viscous oil 27 and the shape and hardness of liquid-filled cushion rubber 26.

[0028] In the steady state (at rotational speeds of 800 to 1,200 r/min) of the spin-drying operation in which the damping force is unnecessary as a rule, supporting shafts 23 and 23a do not make largely tilting oscillation or rotational motion that is seen at the start of the spin-drying operation, and mostly make vertical motion as shown by the arrow A in Fig. 1 on which vibration-proof damper 20 mainly works. For this reason, the damping force of liquid-filled cushion rubber 26 causes substantially no increase in the vibration transmissibility to washing machine body 8. Thus, this structure can suppress the whirling vibrations of water tank unit 5 at the start (at rotational speeds of 0 to 300 r/min) of spin-drying operation, while suppressing the vibration transmission to washing machine body 8 in the steady state (at rotational speeds of 800 to 1,200 r/min) of the spin-drying operation. As a result, vibrations can be reduced.

[0029] In the first exemplary embodiment, liquid-filled cushion rubber 26 is disposed on the side of base 14 only. However, the use of such a cushion rubber in cushioning member 15 on the side of lower support bracket 16 offers a greater advantage.

SECOND EMBODIMENT

[0030] Fig. 3 is a drawing showing a structure of a vibration-proof damper in a drum-type washing machine in accordance with the second exemplary embodiment of the present invention. The schematic structure of the drum-type washing machine other than the vibration-proof damper is identical with that of the conventional example shown in Fig. 6.

[0031] With reference to Fig. 3, vibration-proof damper 30 includes oil damper mechanism 31 having a cylinder filled with oil, and coil spring mechanism 32 disposed coaxially with respect to oil damper mechanism 31. Supporting shaft 33 is fixed to the bottom end of oil damper mechanism 31, and coil spring mechanism 32 is disposed along the outer periphery of the supporting shaft. The supporting shaft is fixed to base 14 of washing machine body 8 via cushioning member 35 so that the cushioning member vertically sandwiches the base. Second supporting shaft 33a constituting oil damper mechanism 31 is fixed, via cushioning member 35, to lower support bracket 16 that is fixed to a lower portion of water tank 3 so that the cushioning member vertically sandwiches the lower support bracket.

[0032] Cushioning member 35 is made of a rubber material having a dissipation factor of tanδ = 0.7 ± 0.2.

[0033] A description is provided of the operation and advantage of the second exemplary embodiment structured as above.

[0034] The physical meaning of the dissipation factor and the reason for the setting are described as follows.

[0035] A dissipation factor of tanδ is expressed by the following equation:


where τ shows a transmission rate (resonance magnification) at resonance.

[0036] As shown above, the dissipation factor is one of the indexes for evaluating vibration-damping characteristics. In general, the value of G"/G', i.e. the ratio of the loss shearing modulus G" to the storage shearing modulus G', is called a loss tangent (dissipation factor) and expressed as tanδ. The dissipation factor shows how much a material absorbs energy (changes the energy to heat) when the material deforms, and is measured using a dynamic viscoelasticity measuring device. A material having a larger value of tanδ absorbs more energy, and exhibits a smaller repulsive elastic modulus in a shock cushioning test and a lower resonance magnification in a vibration test.

[0037] As described above, in a vibration mode including pitching at the start of spin-drying operation, the water tank unit is in the directions in which shafts 33 and 33a rotate (tilt down), in precession motion in a circular or elliptic shape as shown by the arrow C or B, respectively, in Fig. 3, or in motion in combination of these movements. In other words, the water tank unit makes small strokes in the vertical direction. Thus, a sufficient damping force is not easily obtainable only with conventional oil damper mechanism 31.

[0038] When supporting shaft 33 is fixed via cushioning member 35, the strong internal damping action that supporting shaft 33 exerts in the rotational directions can ensure a large damping force, and effectively suppress the whirling vibrations of water tank unit 5. For cushioning member 35 made of a rubber material, the spring constants and dissipation factors in the rotational and translational directions can be determined simply by the material and simple shape. An excessively large value of the dissipation factor increases the vibration transmissibility to washing machine body 8 and promotes vibration of the washing machine body. For this reason, the optimum values of the dissipation factor are determined according to experiments.

[0039] Fig. 4 is a graph showing the relation between dissipation factors and vibration values in the drum-type washing machine in accordance with the second exemplary embodiment of the present invention. In Fig. 4, the ordinate axis on the left side shows whirling vibration values of water tank unit 5 at the start of spin-drying operation. The ordinate axis on the right side shows values of the vibration amplitudes of washing machine body 8 in the spin-drying operation. The abscissa axis shows dissipation factors (i.e. damping coefficients).

[0040] At a smaller value of the dissipation factor (i.e. damping coefficient), the whirling of the water tank unit is higher but the vibration transmissibility to washing machine body 8 is smaller. Thus, washing machine body 8 has smaller vibrations. In contrast, at a larger value of the dissipation factor, the motion of water tank unit 5 is damped and reduced, but the vibration transmissibility to washing machine body 8 is larger. Thus, washing machine body 8 has larger vibrations.

[0041] Relative comparisons are made between the vibration values of water tank unit 5 and the allowable vibration limit of washing machine body 8, and studies are made on the vibration-damping characteristics of the cushioning member capable of preventing worsened vibrations of the washing machine body and suppressing the whirling of water tank unit 5. According to the conclusion of the studies, a dissipation factor of tanδ = 0.7 ± 0.2 shows the range of optimum values. Because the cushioning member works to support water tank unit 5, materials having extremely low rubber hardness are difficult to use. In this exemplary embodiment, the tilt angle of water tank unit 5 is assumed to be 45° or larger.

[0042] The cushioning member generally for use in a drum-type washing machine has an external shape of 30 mm in diameter and a radial thickness of 10 mm. Experimental results show that the above tendency is substantially unchanged even when the cushioning member has a different external shape or radial thickness. Thus, the above cushioning member can suppress the whirling vibrations of water tank unit 5 at the start (at rotational speeds of 0 to 300 r/min) of spin-drying operation while suppressing the vibration transmission to the washing machine body in the steady state (at rotational speeds of 800 to 1,200 r/min) of the spin-drying operation. As a result, vibrations can be reduced.

THIRD EMBODIMENT

[0043] Fig. 5A is a drawing showing a partial structure of a vibration-proof damper in a drum-type washing machine in accordance with the third exemplary embodiment of the present invention. The structure other than the damper is identical with that of the first exemplary embodiment. With reference to Fig. 5A, cushioning member 36 is fixed to the bottom end of supporting shaft 33 of the vibration-proof damper so that the cushioning member is sandwiched between washers 37 disposed in the positions above and below base 14 and vertically sandwiches base 14.

[0044] Cushioning member 36 is formed in a double doughnut shape. In other words, first cushioning member 36a is provided on the inner side, i.e. the side of supporting shaft 33, and second cushioning member 36b is provided on the outer side of the first cushioning member. Thus, the cushioning member exhibits a double structure having different dissipation factors or different hardnesses. Further, second cushioning member 36b has inclined plane 36c formed so that the thickness is reduced toward the outer side of the second cushioning member.

[0045] The cushioning member is structured so that first cushioning member 36a on the inner side has a smaller dissipation factor or hardness than second cushioning member 36b on the outer side. For example, second cushioning member 36b on the outer side is formed of a rubber material having a dissipation factor of tanδ = 0.7 ± 0.2, and first cushioning member 36a on the inner side is formed of a conventional general rubber material having a dissipation factor of tanδ = 0.1 to 0.4, for example. In such a combination, second cushioning member 36b on the outer side having the larger dissipation factor works only in the directions in which the supporting shaft 33 largely rotates (tilts down), or in precession motion.

[0046] Fig. 5B is a drawing showing an operation of the vibration-proof damper in the drum-type washing machine in accordance with the third exemplary embodiment of the present invention. With reference to Fig. 5B, when the vibration of the water tank unit causes tilting oscillation, supporting shaft 33 tilts by an angle of β. At this time, when the tilt angle is equal to or larger than a predetermined angle, the outer peripheries of washers 37 depress second cushioning member 36b on the outer side having the larger dissipation factor, thus exerting strong damping action.

[0047] The general vertical vibrations are supported by first cushioning member 36a on the inner side having the smaller dissipation factor. Thus, the damping action is low and the vibration transmission to washing machine body 8 is small.

[0048] In short, the spring constants and dissipation factors in the rotational and translational directions can be adjusted relatively easily.

[0049] Thus, the vibration-proof damper can suppress the vibration transmission to washing machine body 8 in the steady state (at rotational speeds of 800 to 1,200 r/min) of spin-drying operation and suppress the whirling vibrations of water tank unit 5 at the start (at rotational speeds of 0 to 300 r/min) of the spin-drying operation. As a result, vibrations can be reduced.

[0050] As described above, a vibration-proof damper is fixed via a cushioning member, and a liquid-filled cushion rubber is used for the cushioning member. This structure can suppress the vibration transmission to the washing machine body in the steady state of spin-drying operation without any additional component or weight. Further, this structure can provide a drum-type washing machine in which whirling vibrations of a water tank unit housing a rotary drum thereof are reduced at the start of spin-drying operation.

[0051] Further, the dissipation factor (damping coefficient) of the cushioning member is set to an optimum value. This setting allows the cushioning member to suppress the vibrations at the start of spin-drying operation and satisfy the allowable vibration limit in the steady state at the same time.

[0052] Further, the present invention provides a simple structure of the cushioning member that allows the cushioning member to satisfy a plurality of vibration conditions for the vibrations at the start and in the steady state of spin-drying operation.

[0053] The drum-type washing machine of the present invention can also be used for applications, including a dehydrator and a centrifugal separator.

Claims

1. A drum-type washing machine, comprising:

i) a drum that has a rotation center axis in substantially a horizontal direction, contains laundry, and makes rotary motion;

ii) a water tank unit that houses the drum so that the drum is rotatable therein, and is resiliently supported in a body of the washing machine;

iii) a motor for rotating the drum;

iv) a damper mechanism that resiliently supports the water tank unit thereunder and damps vibrations;

v) a supporting shaft disposed coaxially with respect to the damper mechanism, and a coil spring mechanism disposed around the supporting shaft;

vi) a lower cushioning member for fixing a bottom end of the damper mechanism to a base of the washing machine body; and

vii) an upper cushioning member for fixing a top end of the damper mechanism to a lower portion of the water tank unit,

wherein at least one of the lower cushioning member and the upper cushioning member includes a liquid-filled cushion rubber attached to an outer periphery of the supporting shaft.

2. A drum-type washing machine, comprising:

i) a drum that has a rotation center axis in substantially a horizontal direction, contains laundry, and makes rotary motion;

ii) a water tank unit that houses the drum so that the drum is rotatable therein, and is resiliently supported in a body of the washing machine;

iii) a motor for rotating the drum;

iv) a damper mechanism that resiliently supports the water tank unit thereunder and damps vibrations;

v) a supporting shaft disposed coaxially with respect to the damper mechanism, and a coil spring mechanism disposed around the supporting shaft;

vi) a lower cushioning member for fixing a bottom end of the damper mechanism to a base of the washing machine body; and

vii) an upper cushioning member for fixing a top end of the damper mechanism to a lower portion of the water tank unit,

w herein each of the lower cushioning member and the upper cushioning member are made of a rubber material, and
a dissipation factor of the rubber material is in a range of 0.7 ± 0.2.

3. The drum-type washing machine of claim 2, wherein
each of the lower cushioning member and the upper cushioning member further comprises:

a first cushioning member on an inner peripheral side adjacent to the supporting shaft of the damper mechanism; and

a second cushioning member on an outer peripheral side of the first cushioning member, and

the second cushioning member on the outer peripheral side has a larger dissipation factor than the first cushioning member on the inner peripheral side.

4. The drum-type washing machine of claim 2, wherein
each of the lower cushioning member and the upper cushioning member further comprises:

a first cushioning member on an inner peripheral side adjacent to the supporting shaft of the damper mechanism; and

a second cushioning member on an outer peripheral side of the first cushioning member, and

the second cushioning member on the outer peripheral side has a larger hardness than the first cushioning member on the inner peripheral side.

Drawing