JP2015097600A - Drum-type washing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drum-type washing machine capable of reliably reducing vibration in a short period of time.SOLUTION: The drum-type washing machine includes: a drum 3 rotatably supported by a horizontal or inclined revolving shaft; a drive motor 12 for rotationally driving the drum 3; a water tub 2 housing the drum; and balancers 8 each having an annular container accommodating a mobile body comprising a rolling body 9 and a viscous fluid 10, disposed at front and rear end parts of the drum. At the start of rotation of the drum 3, the rolling body 9A in the annular container of the balancer 8A at the frond end part and the rolling body 9B in the annular container of the balancer 8B at the rear end part are made to start rotation movement at different numbers of rotations above an uppermost part of the annular container.

Description

  The present invention relates to a drum-type washing machine that performs washing, rinsing, and dewatering of a laundry in a drum having a horizontal or inclined rotating shaft.

  In general, in a dewatering process of a drum type washing machine having a horizontal or inclined rotating shaft, the laundry may be in an uneven state, that is, an unbalanced state in the drum. When an unbalanced state occurs during the dehydration process, a biased force is applied to the rotating shaft of the drum and vibration is generated. The amplitude of vibration increases in proportion to the square of the rotational speed of the rotating drum. Due to the vibration, the washing machine itself moves, and the noise is so intense that it becomes impossible to drive at a predetermined rotational speed or higher.

  In order to solve this problem and reduce vibration due to unbalance of the laundry, an automatic balancer device is provided on the drum.

  Automatic balancer devices include fluid balancer devices that use viscous fluids (generally oil or calcium chloride aqueous solution), and balls that use rolling elements (generally used as metal balls, hereinafter referred to as balls). Balancer devices are known.

  In the fluid balancer device, an annular container that contains a viscous fluid separated into a plurality of layers in the radial direction is attached to the inner periphery of the drum. In each layer of the annular container, a plurality of partition walls are formed from the outer peripheral surface toward the inner peripheral surface side, and a viscous fluid passage is formed between the partition walls and the inner peripheral surface. Thus, the balance device utilizes a dynamic phenomenon in which the viscous fluid automatically moves to a position that cancels the unbalance with respect to the unbalanced body that generates the eccentric load while restricting the movement of the viscous fluid by the partition wall. The fluid balancer device has an advantage that the viscous fluid can move to a position where the unbalance is canceled and the unbalance can be eliminated in a short time.

  Further, the ball balancer device includes a plurality of balls having degrees of freedom in the rotation direction (circumferential direction) in an annular container attached to the inner periphery of the drum. The ball balancer device is a balance device that utilizes a dynamic phenomenon in which a ball automatically moves to a position where the unbalance is canceled against an unbalanced body that generates an eccentric load. Since the ball itself is heavier than the viscous fluid, the ball balancer device has an advantage that the imbalance can be reduced even when a large imbalance occurs.

  In an automatic balancer device, it is known that a moving body made of a ball and a viscous fluid is enclosed. With this configuration, the fluid balancer device and the ball balancer device can be combined.

  In a drum-type washing machine having a horizontal or inclined rotating shaft, unbalance may occur on the front end side of the drum, or unbalance may occur on the rear end side of the drum. For this reason, automatic balancer devices are disposed at the front end and the rear end of the drum (for example, Patent Document 1).

JP 2012-122576 A

  However, in a drum-type washing machine having a horizontal or inclined rotating shaft, an eccentric load due to unbalance generates different positions and different weights in the front-rear direction of the drum. Therefore, it is unclear how imbalance occurs in the drum.

  In such a drum type washing machine, since the position of the moving body of the automatic balancer device relative to the position of the laundry that causes imbalance cannot be specified at the time of start-up, the automatic balancer device is provided at the front end portion and the rear end portion of the drum. In the arrangement, the operation of the automatic balancer device becomes uncertain, and there is a problem that it is difficult to reliably reduce vibration in a short time.

  The present invention solves the above-described conventional problems, and an object thereof is to provide a drum type washing machine capable of reliably reducing vibrations in a short time.

  In order to solve the above-described conventional problems, a drum-type washing machine according to the present invention accommodates a drum rotatably supported by a horizontal or inclined rotating shaft, a drive motor that rotationally drives the drum, and the drum. A water tank and an annular container that houses a moving body made of rolling elements and / or viscous fluid, and includes a balancer disposed at a front end portion and a rear end portion of the drum. The moving body in the annular container at the rear part and the moving body in the annular container at the rear end start to move beyond the top of the annular container from a sliding state where the moving body stays between the bottom and top of the annular container at different drum rotation speeds It is a thing.

  The present invention also provides a drum rotatably supported by a horizontal or inclined rotating shaft, a drive motor that rotationally drives the drum, a water tank that accommodates the drum, an annular container that accommodates rolling elements and viscous fluid. A balancer disposed at the front end and the rear end of the drum, the viscous fluid in the annular container of the balancer disposed at the front end, and the ring of the balancer disposed at the rear end The liquid volume of the container is different from that of the viscous fluid.

  Furthermore, the present invention provides a drum that is rotatably supported by a horizontal or inclined rotating shaft, a drive motor that rotationally drives the drum, a water tank that accommodates the drum, an annular container that accommodates rolling elements and viscous fluid. A balancer disposed at the front end portion and the rear end portion of the drum, and a rolling element of the annular container of the balancer disposed at the front end portion, and an annular shape of the balancer disposed at the rear end portion The number of rolling elements of the container is different.

  Furthermore, the present invention provides a drum that is rotatably supported by a horizontal or inclined rotating shaft, a drive motor that rotationally drives the drum, a water tank that accommodates the drum, an annular container that accommodates rolling elements and viscous fluid. A balancer disposed at the front end portion and the rear end portion of the drum, and a rolling element of the annular container of the balancer disposed at the front end portion, and an annular shape of the balancer disposed at the rear end portion The hardness of the rolling elements of the container is varied.

  The present invention also provides a drum rotatably supported by a horizontal or inclined rotating shaft, a drive motor that rotationally drives the drum, a water tank that accommodates the drum, an annular container that accommodates rolling elements and viscous fluid. And the balancer disposed at the front end portion and the rear end portion of the drum, and the rolling element is composed of a sphere serving as a center and a coating material applied to the surface of the sphere, and the front end portion The material of the sphere of the rolling element of the annular container of the balancer arranged in the sphere is different from the material of the sphere of the rolling element of the annular container of the balancer arranged at the rear end.

Furthermore, the present invention provides a drum that is rotatably supported by a horizontal or inclined rotating shaft, a drive motor that rotationally drives the drum, a water tank that accommodates the drum, an annular container that accommodates rolling elements and viscous fluid. A balancer disposed at the front end portion and the rear end portion of the drum, wherein the balancer disposed at the front end portion and the balancer disposed at the rear end portion are different in size. It is.

  The drum type washing machine of the present invention can move the balancer moving bodies provided at the front end portion and the rear end portion of the drum in different phases, and can reliably reduce vibration in a short time.

Schematic sectional view of the drum type washing machine in the first embodiment of the present invention. It is sectional drawing seen from the front-end part side of the balancer in Embodiment 1 of this invention, (a) is sectional drawing of a balancer, (b) is a principal part expanded sectional view of a balancer, (c) is (b). Vertical section BRIEF DESCRIPTION OF THE DRAWINGS The drum in Embodiment 1 of this invention is shown, (a) is a schematic block diagram of a drum, (b) is a principal part enlarged view of a balancer. Schematic explaining operation | movement of a rolling element and viscous fluid in Embodiment 1 of this invention. FIG. 1 is a schematic configuration diagram of a comparison device described in comparison with the first embodiment of the present invention. The figure which shows the vibration value of the washing tub in Embodiment 1 of this invention. The figure which shows the relationship between the movement start rotation speed of a rolling element and the liquid quantity of a viscous fluid in Embodiment 1 of this invention. The figure which shows the relationship between the clearance gap between the cyclic | annular container of a balancer and rolling element in Embodiment 1 of this invention, rolling element movement start rotation speed, and the liquid quantity of viscous fluid. The figure which shows the relationship between the hardness of the rolling element in Embodiment 1 of this invention, the rolling element movement start rotation speed, and the liquid quantity of a viscous fluid.

  A drum-type washing machine according to a first aspect of the present invention is a drum that is rotatably supported by a horizontal or inclined rotating shaft, a drive motor that rotationally drives the drum, a water tank that houses the drum, a rolling element, and / or An annular container that contains a moving body made of a viscous fluid, and includes a balancer disposed at a front end portion and a rear end portion of the drum, and the moving body in the annular container at the front end portion when the drum starts rotating. The moving body in the annular container at the rear end portion starts to move beyond the uppermost part of the annular container from the sliding state where the moving body stays between the bottom part and the uppermost part of the annular container at different drum rotation speeds.

  With this configuration, the moving body of the balancer at the front end portion of the drum and the moving body of the balancer at the rear end portion start rotational movement beyond the uppermost portion of the annular container at different drum rotation speeds. Since the moving bodies of the parts move with different phases, it is possible to suppress the vibration increase of the drum.

  According to a second aspect of the present invention, there is provided a drum rotatably supported by a horizontal or inclined rotating shaft, a drive motor for rotationally driving the drum, a water tank for accommodating the drum, an annular container for accommodating rolling elements and viscous fluid. A balancer disposed at the front end and the rear end of the drum, the viscous fluid in the annular container of the balancer disposed at the front end, and the ring of the balancer disposed at the rear end The liquid volume of the container is different from that of the viscous fluid.

  With this configuration, the moving body of the balancer at the front end portion of the drum and the moving body of the balancer at the rear end portion start rotational movement beyond the uppermost portion of the annular container at different drum rotation speeds. Since the moving bodies of the parts move with different phases, it is possible to suppress the vibration increase of the drum.

  According to a third aspect of the present invention, there is provided a drum rotatably supported by a horizontal or inclined rotating shaft, a drive motor for rotationally driving the drum, a water tank for accommodating the drum, an annular container for accommodating rolling elements and viscous fluid. A balancer disposed at the front end portion and the rear end portion of the drum, and a rolling element of the annular container of the balancer disposed at the front end portion, and an annular shape of the balancer disposed at the rear end portion The number of rolling elements of the container is different.

  With this configuration, the moving body of the balancer at the front end portion of the drum and the moving body of the balancer at the rear end portion start rotational movement beyond the uppermost portion of the annular container at different drum rotation speeds. Since the moving bodies of the parts move with different phases, it is possible to suppress the vibration increase of the drum.

  A fourth invention is a drum that is rotatably supported by a horizontal or inclined rotating shaft, a drive motor that rotationally drives the drum, a water tank that accommodates the drum, an annular container that accommodates rolling elements and viscous fluid. A balancer disposed at the front end portion and the rear end portion of the drum, and a rolling element of the annular container of the balancer disposed at the front end portion, and an annular shape of the balancer disposed at the rear end portion The hardness of the rolling elements of the container is varied.

  With this configuration, the moving body of the balancer at the front end portion of the drum and the moving body of the balancer at the rear end portion start rotational movement beyond the uppermost portion of the annular container at different drum rotation speeds. Since the moving bodies of the parts move with different phases, it is possible to suppress the vibration increase of the drum.

  According to a fifth aspect of the present invention, there is provided a drum rotatably supported by a horizontal or inclined rotating shaft, a drive motor for rotationally driving the drum, a water tank for accommodating the drum, an annular container for accommodating rolling elements and viscous fluid. And the balancer disposed at the front end portion and the rear end portion of the drum, and the rolling element is composed of a sphere serving as a center and a coating material applied to the surface of the sphere, and the front end portion The material of the sphere of the rolling element of the annular container of the balancer arranged in the sphere is different from the material of the sphere of the rolling element of the annular container of the balancer arranged at the rear end.

  With this configuration, the moving body of the balancer at the front end portion of the drum and the moving body of the balancer at the rear end portion start rotational movement beyond the uppermost portion of the annular container at different drum rotation speeds. Since the moving bodies of the parts move with different phases, it is possible to suppress the vibration increase of the drum.

  A sixth invention is a drum that is rotatably supported by a horizontal or inclined rotating shaft, a drive motor that rotationally drives the drum, a water tank that accommodates the drum, an annular container that accommodates rolling elements and viscous fluid. A balancer disposed at the front end portion and the rear end portion of the drum, wherein the balancer disposed at the front end portion and the balancer disposed at the rear end portion are different in size. It is.

  With this configuration, the moving body of the balancer at the front end portion of the drum and the moving body of the balancer at the rear end portion start rotational movement beyond the uppermost portion of the annular container at different drum rotation speeds. Since the moving bodies of the parts move with different phases, it is possible to suppress the vibration increase of the drum.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, this plan is not limited by this embodiment.

(Embodiment 1)
1 is a schematic cross-sectional view of a drum-type washing machine according to Embodiment 1 of the present invention. Inside the drum type washing machine 1, a bottomed cylindrical water tank 2 is accommodated. The water tank 2 is elastically supported by a spring 24 and a damper 19. A bottomed cylindrical drum 3 is accommodated in the water tank 2. On the front side of the drum-type washing machine 1, an opening 3 b that communicates with the drum 3 through the opening 2 a of the water tank 2 is provided. The drum 3 is disposed such that a rotation shaft 3a for rotating and supporting the drum 3 is in a substantially horizontal direction. In consideration of ease of taking out the laundry 18 and water saving at the time of washing, the rotary shaft 3a may be inclined downward from the front side to the bottom side so that the drum 3 is inclined. .

  Inside the drum 3, a baffle 7 is provided that can lift and drop the laundry 18 as the drum 3 rotates. When the drum 3 is driven to rotate, the laundry lifted by the baffle 7 is struck against the water surface from the upper part of the drum 3 and is washed by tapping (mechanical force). Further, the drum 3 is provided with a plurality of through holes 20 on the entire circumference. Water can be passed from the water tank 2 into the drum 3 through the through holes 20.

  Moreover, the door 21 which closes | closes the opening part 2a of the water tub 2 so that opening and closing is possible is provided in the front surface of the washing machine 1. FIG. The opening 2a of the water tank 2 is provided with an annular sealing material (not shown) at its mouth edge. The front side of the sealing material is in contact with the rear side of the door 21 to be sealed, and even when the opening 2a of the water tank 2 that swings up and down, right and left and back and forth moves, the sealing material is deformed and the rear side of the door 21 The airtightness is maintained.

  The drive motor 12 that drives the drum 3 applies rotational power to the rotary shaft 3 a via the belt 6, so that the drum 3 rotates in the water tank 2. A vibration detection unit 40 that measures the vibration value of the water tank 2 when the drum 3 rotates is provided in front of the upper part of the water tank 2.

  With the opening 3b side of the drum 3 as the front end, the opposite side of the opening 3b as the rear end, a balancer 8A is disposed at the front end, and a balancer 8B is disposed at the rear end. The balancers 8A and 8B are formed in an annular container shape. In the present embodiment, the shape of the annular container of the balancer 8A and the annular container of the balancer 8B are formed in the same shape.

  In the annular containers of the balancers 8A and 8B, viscous fluids 10A and 10B (in this embodiment, a low-viscosity calcium chloride aqueous solution of 4 cSt or less) and rolling elements 9A and 9B (in this embodiment, on the steel ball surface) It contains a rubber coated ball). The rolling elements 9A and 9B and the viscous fluids 10A and 10B constitute a moving body. The amount of the viscous fluid 10A of the balancer 8A is different from that of the viscous fluid 10B of the balancer 8B. In the present embodiment, the viscous fluid 10A of the balancer 8A is made larger than the viscous fluid 10B of the balancer 8B.

  FIG. 2A is a cross-sectional view of a balancer provided on the drum 3 of the drum type washing machine 1 according to Embodiment 1 of the present invention. FIG. 2B is an enlarged cross-sectional view of a main part of the protrusion of the balancer. FIG. 2C is a vertical sectional view of FIG.

  As shown in FIGS. 2A to 2C, in the annular containers of the balancers 8A and 8B, between the inner peripheral surface 25 and the outer peripheral surface 26, rolling elements 9A and 9B and viscous fluids 10A and 10B are provided. And are configured to move. A plurality of protrusions 29 are provided on one side of the drum shaft on the inner peripheral surface 25 side of the annular container. The flat surface on which the protrusion 29 of the inner peripheral surface 25 is not formed is formed higher than the radius of the rolling elements 9A and 9B. Further, the protrusions 29 are formed with a slight clearance with respect to the flat surface so as not to protrude from the flat surface on which the protrusions 29 of the inner peripheral surface 25 are not formed. Thus, the rolling elements 9A and 9B are configured not to contact the protrusion 29.

  The protrusion 29 is formed in a sawtooth shape, and the surface on the rotation direction side is formed to be substantially perpendicular to the normal line, and has a space for storing the viscous fluids 10A and 10B between the protrusions 29. ing.

  The balancer 8A disposed at the front end portion of the drum 3 and the balancer 8B provided at the rear end portion have the same structure. The balancers 8A and 8B are disposed on the drum 3 so that the protrusions 29 face in the same direction.

  When the drum 3 rotates in the rotation direction C1 of the drum 3 during the dehydration process, the balancers 8A and 8B disposed on the drum 3 are spaces between the protrusions 29 at positions below the drum 3 where the viscous fluids 10A and 10B are gathered. Thus, the viscous fluids 10A and 10B are rotated while being scooped up, and the viscous fluids 10A and 10B are pushed by the surface of the protrusion 29 on the rotational direction side so as to apply a propulsive force.

  The balancer 8B disposed at the rear end of the drum 3 has a smaller amount of viscous fluid 10B than the balancer 8A. Therefore, the propulsive force that the protrusion 29 of the balancer 8B applies to the viscous fluid 10B is less than the propulsive force that the protrusion 29 of the balancer 8A applies to the viscous fluid 10A. Therefore, the viscous fluid 10B of the balancer 8B has a relatively low flow rate compared to the viscous fluid 10A of the balancer 8A.

  FIG. 4 is a schematic cross-sectional view for explaining the operation of the rolling elements 9A and 9B and the viscous fluids 10A and 10B in the balancers 8A and B.

  In the present embodiment, the rotational speed at which rotational movement of the rolling elements 9A and 9B starts (rotational movement starting rotational speed) refers to the rotational speed of the drum 3 when the rolling elements 9A and 9B housed inside the balancers 8A and 8B. The number of rotations of the balancers 8A and 8B that move to the upper side of the annular container and start rotational movement beyond the uppermost part of the annular container.

  FIG. 4 shows the drum 3 in the dehydration process, and the state on the left side in FIG. 4 shows the state where the drum 3 is stopped. In FIG. 4, the lower left 100 </ b> A indicates the state of the balancer 8 </ b> A disposed at the front end of the drum 3, and the upper left 100 </ b> B indicates the state of the balancer 8 </ b> B disposed at the rear end of the drum 3. As shown in the drawing, when the drum 3 is stopped, the rolling elements 9A and 9B and the viscous fluids 10A and 10B are biased toward the bottom of the drum 3. The unbalance of the laundry 18 is also biased toward the bottom.

  In FIG. 4, the center shows a state in which the drum 3 is rotating at 120 rpm in the direction of forward rotation (C1). At this time, it is assumed that the unbalance of the laundry 18 is stuck to the inner surface of the drum 3. In FIG. 4, 101A at the bottom center indicates the state of the balancer 8A, and 101B at the center indicates the state of the balancer 8B.

  When the drum 3 starts rotating, the viscous fluids 10A and 10B in the balancers 8A and 8B move to the outer peripheral side of the annular containers of the balancers 8A and 8B by centrifugal force as the rotational speed of the drum 3 increases. Further, the viscous fluids 10A and 10B move to the rotation direction side of the drum 3 by the frictional resistance between the inner surfaces of the annular containers of the balancers 8A and 8B and the viscous fluids 10A and 10B and the propulsive force by the protrusions 29.

  The viscous fluid 10A of the balancer 8A has a larger liquid volume than the viscous fluid 10B of the balancer 8B. Accordingly, the viscous fluid 10A in the balancer 8A has a faster flow velocity than the viscous fluid 10B in the balancer 8B, and the viscous fluid 10A in the balancer 8A is closer to the rotation direction of the drum 3 than the viscous fluid 10B in the balancer 8B. Moved.

  When the number of rotations of the drum 3 further increases, the viscous fluids 10A and 10B in the balancer 8A eventually stick to the outer periphery of the annular container beyond the uppermost part of the annular containers of the balancers 8A and 8B by centrifugal force.

  The rolling elements 9A and 9B move to the rotation direction side of the drum 3 by the frictional resistance with the inner surfaces of the annular containers of the balancers 8A and 8B and the propulsive force of the viscous fluids 10A and 10B. The rolling element 9A of the balancer 8A moves to the rotational direction side of the drum 3 with respect to the rolling element 9B of the balancer 8B by the viscous fluid 10A to which the propelling force is given by the protrusion 29.

  As a result, in the balancers 8A and 8B, the rolling elements 9A and 9B move in an asynchronous state, out of synchronization. The rolling elements 9 </ b> A and 9 </ b> B are not in a state of co-rotation with the rotation of the drum 3 by the centrifugal force generated by the rotation speed of the drum 3 at 120 rpm.

  In FIG. 4, the state on the right side shows a state in which the number of rotations of the drum 3 increases and the drum 3 is rotating at 140 rpm in the direction of forward rotation (C1). In FIG. 4, the lower right 102A indicates the state of the balancer 8A, and the upper right 102B indicates the state of the balancer 8B.

  As the number of revolutions of the drum increases, the moving speed of the viscous fluids 10A and 10B in the balancers 8A and 8B increases, and due to the centrifugal force and the propulsive force from the protrusions 29, the outer circumferences of the balancers 8A and 8B It becomes a spread state. In the balancer 8A, the action of the protrusion 29 on the viscous fluid 10A is strong, and thus the viscous fluid 10A is in a state of sticking over substantially the entire outer periphery of the annular container.

  In the balancer 8A, the rolling element 9A is pushed up toward the top of the annular container of the balancer 8A by the frictional resistance with the inner surface of the annular container of the balancer 8A and the propulsive force of the viscous fluid 10A. Rotation starts beyond the top.

  When the rotational speed is 140 rpm or more, the rolling element 9A continuously rotates over the uppermost portion of the annular container of the balancer 8A, and the rolling element 9A rotates together with the annular container of the balancer 8A (the rolling element 9A and the annular container). Are in the state of rotating together with the same rotational speed or the rotational speed of the rolling element 9A slightly delayed from the annular container.

  In the balancer 8B, in the state where the drum 3 is rotating at 140 rpm, the rolling element 9B moves to the upper end side than in the state where the drum 3 is rotating at 120 rpm, and in a biased state from the bottom of the annular container. It stays in the state up to the top. In the balancer 8B, when the number of rotations of the drum 3 exceeds 160 rpm, the rolling element 9B starts rotating.

  In the present embodiment, the rolling element 9A of the balancer 8A starts rotating with the rotation speed of the drum 3 being 140 rpm or more, and the rolling element 9B of the balancer 8B is the rotation speed of the drum 3 being 160 rpm or more. Rotational movement has started.

  In this embodiment, the rolling element 9A of the balancer 8A disposed at the front end of the drum 3 is rotated first, but the rolling element 9B of the balancer 8B disposed at the rear end of the drum 3 is You may comprise so that it may rotate first.

Next, FIG. 5 shows a comparison device for comparison with the present embodiment. The comparison apparatus uses balancers 8A and 8B having the same configuration, and the liquid amounts of the viscous fluids 10A and 10B of the balancers 8A and 8B are the same. Accordingly, the rolling elements 9A and 9B start to rotate and move in a state where the drum 3 is rotated at a rotation speed of 140 rpm or more in the forward rotation direction (C1).

  In the comparison device shown in FIG. 5, the rolling elements 9 </ b> A and 9 </ b> B start rotating over the uppermost portions of the annular containers of the balancers 8 </ b> A and 8 </ b> B in a state where the drum 3 rotates in the forward rotation direction at a rotational speed of 140 rpm or more. . Since the rolling elements 9A and 9B of both balancers 8A and 8B start to rotate almost simultaneously, the rolling elements 9A and 9B act as an unbalance. That is, the rolling elements 9 </ b> A and 9 </ b> B rotate and move in the same phase (circumferential same phase position) at the front end portion and the rear end portion of the drum 3. Therefore, the correction amounts of both the balancers 8A and 8B that should correct the unbalance act on the drum 3 as the unbalance amount.

  When the unbalanced position of the laundry 18 with respect to the drum 3 is in phase with the rotational movement of the rolling elements 9A and 9B at the front and rear ends of the drum 3, the unbalanced state will further increase. The vibration is increased.

  6 shows the number of rotations and the left-right vibration value of the drum 3 in the present embodiment and the comparison device shown in FIG. The left-right vibration value is detected by a vibration detection unit 40 provided at the upper front end of the water tank 2.

  L1 is a vibration value limit at start-up, and is a value set to prevent the water tank 2 of the drum type washing machine 1 from colliding with the outer frame of the drum type washing machine 1 due to vibration. . The time T1 is a time for rotating the drum 3 at 120 rpm at the time of startup, measuring the vibration value of the vibration detection unit 40, and determining the unbalanced state of the laundry 18. At this rotational speed, the rolling elements 9A and 9B of the balancers 8A and 8B are not rotationally moved.

  Furthermore, the vibration waveform S2 shows the vibration waveform of the present embodiment, and the vibration waveform S21 is a state where the drum 3 is rotating at a rotation speed of 140 rpm (point R1: time t11). The change in the vibration value of the vibration detection unit 40 in a state where only the rolling elements 9A of the balancer 8A disposed at the front end portion of the drum 3 starts rotating is shown. The vibration waveform S22 is the vibration detection unit 40 when the rolling element 9B of the balancer 8B at the rear end of the drum 3 starts rotating in a state where the drum 3 is rotating at 160 rpm (point R2: time t12). The vibration value change is shown.

  As shown in FIG. 6, when the rotation speed of the drum 3 reaches 140 rpm after the lapse of time T1, the rolling element 9A of the balancer 8A starts rotating and moving over the top of the annular container of the balancer 8A. The vibration does not increase as shown by the vibration waveform S21. When the number of rotations of the drum 3 is increased to 160 rpm, the rolling elements 9B of the balancer 8B start to rotate over the uppermost part of the annular container. At the start of the rotational movement of the rolling element 9B, the rolling element 9A has already been rotationally moved. Accordingly, the rotational movement of the rolling elements 9A and 9B has different phases (not overlapping) in the circumferential direction of the drum 3, so that the vibration of the drum 3 does not increase as shown by the vibration waveform S22. As a result, the vibration of the water tank 2 is suppressed from increasing.

  Further, for example, when the unbalanced position of the laundry 18 and the rotational movement of the rolling element 9B move to the same phase (overlapping) position, the rolling element 9A has a different phase (not overlapping) with respect to the rolling element 9B. ) To rotate. Thereby, the rolling element 9A acts so as to correct the unbalanced state synthesized by the laundry 18 and the rolling element 9B, and the increase in vibration of the drum 3 can be suppressed.

As described above, a difference is provided in the rotational speed at which the rotational movement is started between the rolling element 9A of the balancer 8A located at the front end and the rolling element 9B of the balancer 8B located at the rear end. With this configuration, increase in vibration of the drum 3 can be prevented. This can be easily realized by disposing balancers 8A and 8B having different amounts of the viscous fluid 10A and the viscous fluid 10B at the front end portion and the rear end portion of the drum 3, respectively.

  Next, a vibration waveform S1 in FIG. 6 shows a vibration waveform of the comparison device. In the comparison device, the rolling elements 9A and 9B of the balancers 8A and 8B disposed at the front end portion and the rear end portion of the drum 3 simultaneously start rotational movement with the drum 3 rotating at 140 rpm (time t11). In the comparison device, since the rolling elements 9A and 9B move in the same phase, it operates as an unbalanced state exceeding the correction amount of the balancers 8A and 8B, and it can be seen that the vibration value of the vibration detector 40 is increased. .

  The test results shown in FIG. 6 show a case where the drum 3 of the present embodiment and the comparison device is rotated at a constant rotational acceleration and the rotational speed is increased. In the present embodiment, even when the rotational acceleration condition is changed, the rolling element 9A of the balancer 8A at the front end of the drum 3 starts to rotate and rotates at the rotational speed of the drum 3 of 140 rpm. In a state of 160 rpm, the rolling element 9B of the balancer 8B at the rear end of the drum 3 starts to rotate. The time t11 when the rolling element 9A starts to rotate and the time t12 when the rolling element 9B starts to rotate vary depending on the rotational acceleration.

  In the present embodiment, even when the rotational acceleration is changed, there is a difference between the time t11 when the rolling element 9A starts rotating and the time t12 when the rolling element 9B starts rotating. Thereby, since the position (phase) of the circumferential direction of the drum 3 differs in the position where the rolling element 9A and the rolling element 9B rotate, the increase in vibration can be suppressed. Therefore, the vibration can be minimized by optimizing the time t11 when the rolling element 9A starts to rotate and the time t12 when the rolling element 9B starts rotating.

  Next, FIG. 7 shows the number of rotations of the drum 3 for setting the conditions for the rolling element 9A of the balancer 8A to start rotational movement beyond the uppermost part of the annular container, and the balancer 8A in the present embodiment. The relationship with the liquid quantity of 10 A of viscous fluid to accommodate is shown.

  The balancers 8A and 8B have 48 protrusions 29 formed in an annular container. The viscous fluids 10A and 10B are calcium chloride aqueous solutions and have a viscosity of 4 cSt. The amount of the viscous fluid 10A of the balancer 8A is 450 g, and the amount of the viscous fluid 10B of the balancer 8B is *** g. The rolling elements 9A and 9B have the same configuration and 20 pieces are used. The rolling elements 9A and 9B have an outer diameter of φ21 and a mass of 30 g / piece. The rolling elements 9 </ b> A and 9 </ b> B are made of steel balls inside and EPDM rubber is uniformly coated on the surface, and the hardness of the rubber is 70.

  FIG. 7 shows the rotational speed characteristics at which the rolling elements 9A and 9B start rotating when the amount of the aqueous solution of calcium chloride, which is the viscous fluids 10A and 10B, is changed under the above conditions. The viscous fluid 10A of the balancer 8A and the viscous fluid 10B of the balancer 8B are adjusted so as to increase or decrease at the same rate.

  FIG. 7 shows the amount of the viscous fluid 10A of the balancer 8A.

  In FIG. 7, CS1 (CW) indicates the rotational speed characteristic at which the rolling element 9A of the balancer 8A starts rotational movement, and CS2 (CCW) indicates the rotational speed characteristic at which the rolling element 9B of the balancer 8B starts rotational movement. Yes. As shown in CS1 (CW) and CS2 (CCW), the rotational speed at which the rolling elements 9A and 9B start rotational movement generates a difference in constant rotational speed even if the liquid amounts of the viscous fluids 10A and 10B are adjusted. To do. As the amount of the aqueous solution of calcium chloride, which is the viscous fluids 10A and 10B, increases, the rotational speed at which the rolling elements 9A and 9B start to rotate decreases.

The rotation speed at which the gravity applied to the laundry 18 and the centrifugal force due to the rotation of the drum 3 are balanced and the laundry 18 is stuck to the inner surface of the drum 3 is about 90 to 110 rpm. The primary resonance speed of the water tank 2 is about 190 to 210 rpm. Accordingly, the rolling elements 9A and 9B start rotating in the range of 100 rpm or more and 200 rpm or less, and the rolling element 9A is approximately rotated between the number of rotations at which the rolling element 9A starts rotating and the number of rotations at which the rolling element 9B starts rotating. The condition is that a difference of 10 to 20 rpm can be generated.

  In order to detect the unbalanced state of the laundry 18, the vibration value can be measured by the vibration detection unit 40, and the rotational speed at which the rolling elements 9A and 9B do not start rotating is 120 rpm. Assuming that the rotational speed is 120 rpm or more and that there is a difference of about 20 rpm in the rotational speed at which the rolling elements 9A and 9B start rotating, the viscous fluid 10A of the balancer 8A is chlorinated based on FIG. The calcium aqueous solution is set to 450 g. Further, in order to provide a difference of about 20 rpm in the rotational speed at which the rolling element 9A and the rolling element 9B start rotating, the viscous fluid 10B of the balancer 8B is set to calcium chloride aqueous solution *** g.

  In this embodiment, the viscosity of the viscous fluids 10A and 10B is 4 cSt. However, when the viscosity of the viscous fluids 10A and 10B is increased, CS1 and CS2 shown in FIG. Transition. Therefore, when the number of rotations is set to 140 rpm and 160 rpm, adjustment is possible by reducing the liquid amounts of the viscous fluids 10A and 10B.

  Due to a dimensional error in the distance between the inner surface and the outer surface of the annular containers of the balancers 8A and 8B and a dimensional error in the outer diameter of the rolling elements 9A and 9B, a variation in the gap occurs between the annular container and the rolling elements 9A and 9B. .

  FIG. 8 shows the measurement of the rotation characteristics due to the variation in the gap between the inner surface of the annular container and the outer periphery of the rolling elements 9A and 8B in the balancers 8A and 8B while the drum 3 of the present embodiment is rotated. In balancer 8A and 8B, it adjusts and measures so that the dispersion | variation in the clearance gap between the annular container inner surface and rolling element 9A and 8B outer periphery may become the same.

  FIG. 8 shows the measurement result of the balancer 8A.

  A case where the variation in the gap is maximum (MAX) is indicated as CS4, a case where the variation is minimum (MIN) is indicated as CS5, and a case where the variation is intermediate (CENTER) is indicated as CS1. According to this result, it can be seen that as the gap between the rolling elements 9A and 9B and the annular containers of the balancers 8A and 8B becomes larger, the rotational speed at which the rolling movement of the rolling element 9A starts is shifted to the higher rotational speed side. In the present embodiment, the gap is set so that the variation rotational speed is about 10 rpm.

  In the present embodiment, the gap between the annular containers of the balancers 8A and 8B and the rolling elements 9A and 9B is 1 mm. By adjusting this gap, the rotational movement start rotational speed of the rolling elements 9A and 9B can be adjusted. When the gap is reduced, the propulsive force that propels the viscous fluids 10A and 10B in the rotational direction tends to increase. Accordingly, since the propulsive force for the rolling elements 9A and 9B also becomes strong, CS1 and CS2 shown in FIG. 7 shift in a direction in which the rotational speed decreases overall.

  Further, when the gap is increased, the relationship between the movement start rotational speed of the rolling elements 9A and 9B and the liquid amount of the viscous fluids 10A and 10B shifts from the CS1 side shown in FIG. 8 to the CS4 side. Conversely, when the gap is reduced, the CS1 side is shifted to the CS5 side.

Therefore, the variation in the gap between the annular containers of the balancers 8A and 8B and the rolling elements 9A and 9B can be adjusted by increasing or decreasing the amount of the viscous fluids 10A and 10B.

  The clearance between the annular containers of the balancers 8A and 8B and the rolling elements 9A and 9B can be adjusted by adjusting the inner and outer diameters of the annular containers or by adjusting the diameters of the rolling elements 9A and 9B. Even when such adjustment is performed, it is possible to adjust the rotation speed of the drum 3 on which the rolling elements 9A and 9B rotate by adjusting the liquid amounts of the viscous fluids 10A and 10B.

  FIG. 9 shows a change in the rotational movement start rotational speed of the rolling element 9A due to variation in hardness of the EPDM rubber coated on the surface of the rolling element 9A of the balancer 8A of the present embodiment. The variation in hardness of the rolling elements 9A of the balancer 8A and the rolling elements 9B of the balancer 8B is adjusted and measured so as to satisfy the same conditions.

  FIG. 9 shows the maximum hardness (MAX) due to the variation in the hardness of the surface of the rolling element 9A of the balancer 8A as CS6, the minimum hardness (MIN) as CS7, and the intermediate hardness (CENTER) as CS1. As shown in FIG. 9, as the hardness of the rolling element 9A increases, the rotational speed at which the rolling movement of the rolling element 9A starts is shifted to the higher rotational speed side.

  As a result of the above test, balancers 8A and 8B containing moving bodies composed of rolling elements 9A and 9B and viscous fluids 10A and 10B are arranged at the front end and the rear end of drum 3, and balancers 8A and 8B are The liquid amounts of the viscous fluid 10A and the viscous fluid 10B are made different.

  With this configuration, the rotational speed at which the rolling elements 9A and 9B start to rotate is less than or equal to the primary resonant rotational speed (190 to 210 rpm) of the water tub 2 and the laundry 18 is attached to the inner peripheral surface of the drum 3. It can set to the rotation speed (90-110 rpm) or more which can be maintained. Furthermore, the difference of the rotation speed which starts the rotational movement of the rolling elements 9A and 9B in balancer 8A and 8B arrange | positioned at the front-end part and rear-end part of the drum 3 can be set to about 10-20 rpm.

  In the present embodiment, an aqueous calcium chloride solution is used as the viscous fluids 10A and 10B in the balancers 8A and 8B, the viscosity is 4 cSt, and the liquid amount is 450 g. The rolling elements 9A and 9B are steel balls, and the surface thereof is coated with EPDM rubber to have a hardness of 70 degrees. Furthermore, although the shape of the protrusion 29 is illustrated as an example, it is not limited to these configurations.

  For example, water or silicone oil may be used as the viscous fluids 10A and 10B. The liquid used as the viscous fluids 10A and 10B may have a viscosity of 1 cSt or more. By adjusting the fluid amounts of the viscous fluids 10A and 10B and the friction coefficient of the rolling elements 9A and 9B, the rotational speed at which the rolling elements 9A and 9B start to rotate is changed to the primary resonance rotational speed (190 to 210 rpm) of the water tank 2. The rotational speed (90 to 110 rpm) can be set to be equal to or higher than the following so that the laundry 18 can be kept attached to the inner peripheral surface of the drum 3.

  Further, as a sphere serving as the center of the rolling elements 9A and 9B, a metal sphere, a glass sphere, or a rubber sphere having a specific gravity equivalent to a steel ball may be used. Further, as a coating material on the surface of the rolling elements 9A and 9B, a material that generates friction between the inner surface of the annular container of the balancers 8A and 8B and the surface of the rolling elements 9A and 9B, such as EPDM, silicon rubber, nylon, urethane, polyethylene, etc. Other materials may be used if present.

The hardness of the surfaces of the rolling elements 9A and 9B is such that the rotational speed at which the rolling elements 9A and 9B start rotational movement is equal to or less than the primary resonance rotational speed (190 to 210 rpm) of the water tub 2 and the inner circumference of the drum 3 of the laundry 18 What is necessary is just the range which can be adjusted by adjustment of the viscosity, liquid quantity, etc. of viscous fluid 10A and 10B so that it can set to the rotation speed (90-110 rpm) or more which can maintain the state sticking to a surface.

  In the present embodiment, 48 protrusions 29 are formed, but the number is not limited to 48. When the number of the protrusions 29 is reduced, the propulsive force for propelling the viscous fluids 10A and 10B in the rotational direction is weakened, so that the drag force against the rolling elements 9A and 9B is also weakened. Therefore, CS1 and CS2 shown in FIG. 7 shift in a direction in which the rotational movement start rotational speed increases as a whole.

  Therefore, when the number of rotations of the drum 3 on which the rolling elements 9A and 9B rotate is set to 140 rpm and 160 rpm, adjustment is possible by increasing the liquid amounts of the viscous fluids 10A and 10B. On the contrary, when increasing the number of formation of the protrusions 29, it is possible to adjust by decreasing the amount of the viscous fluids 10A and 10B.

  In the present embodiment, the surface hardness of the rolling elements 9A and 9B is set to 70 degrees. When the hardness changes, the friction coefficient between the annular container inner surfaces of the balancers 8A and 8B and the rolling elements 9A and 9B changes. Thereby, the rotational movement start rotation speed of the rolling elements 9A and 9B changes.

  When the hardness of the rolling elements 9A and 9B is increased, the rotational movement start rotational speed of the rolling elements 9A and 9B is increased from CENTER (CS1) shown in FIG. 8 to the MAX (CS6) side. In contrast, when the hardness of the rolling elements 9A and 9B decreases, the rotational movement start rotational speed is shifted from CENTER (CS1) to the MIN (CS7) side.

  That is, when the hardness of the rolling elements 9A and 9B increases, the rolling elements 9A and 9B easily move (the friction is small). In addition, when the hardness of the rolling elements 9A and 9B is low, the rolling elements 9A and 9B are difficult to move (the friction is large).

  Therefore, when the hardness of the rolling elements 9A and 9B is increased, adjustment can be performed by increasing the amount of the viscous fluids 10A and 10B. Conversely, when the hardness of the rolling elements 9A and 9B is low, adjustment can be made by reducing the amount of the viscous fluids 10A and 10B.

  Further, regarding the gap between the annular containers of the balancers 8A and 8B and the rolling elements 9A and 9B, the viscosity of the viscous fluids 10A and 10B, the frictional resistance of the surfaces of the rolling elements 9A and 9B, the shape of the protrusions 29, the number of the protrusions 29, etc. By adjusting the above, it is possible to set the conditions for the rotational movement start rotational speed of the rolling elements 9A and 9B described above, and the present invention is not limited to this embodiment.

  A structure having a constant rotational speed difference between the movement start rotational speed of the rolling element 9A of the balancer 8A and the movement start rotational speed of the rolling element 9B of the balancer 8B disposed at the front end portion and the rear end portion of the drum 3. If there is, it is not limited to the above-mentioned conditions. If the rotational speeds of the rolling elements 9A of the balancer 8A and the rolling elements 9B of the balancer 8B are different from each other, the structure in which the rolling elements 9A and 9B of the balancers 8A and 8B start moving simultaneously at the start of dehydration (comparison device). It is possible to prevent the occurrence of unbalance in.

  The protrusion 29 having an asymmetric shape with respect to the rotating direction of the drum 3 generates a propulsive force in the rotating direction with respect to the viscous fluids 10A and 10B, and moves the rolling element 9A in the rotating direction by the propelling force. It is.

Therefore, the protrusion 29 may have any shape as long as it can generate a propulsive force with respect to the viscous fluids 10A and 10B. Therefore, the present invention is not limited to the shape and number of embodiments.

  In the present embodiment, the same materials are used for the viscous fluids 10A and 10B. However, the viscous fluid 10A and the viscous fluid 10B may be made of different viscous materials. Also in this case, it is possible to adjust the liquid amount so that the difference between the rotational movement opening rotational speeds of the rolling elements 9A and 9B becomes a desired rotational speed.

  In the present embodiment, the rolling elements 9A and 9B and the viscous fluids 10A and 10B are housed in the balancers 8A and 8B. However, only the rolling elements or only the viscous fluid may be used. The rolling elements 9A and 9B have been described as spheres, but may have other shapes as long as they can move freely within the annular containers of the balancers 8A and 8B.

  Further, in the present embodiment, the rolling element 9A of the balancer 8A is set to start rotating at the rotation speed of the drum 3 at 140 rpm, and the rolling element 9B of the balancer 8B is set to start to move at the rotation speed of the drum 3 at 160 rpm. However, the number of rotations is not limited, and the number of rotations at which the rolling elements 9A and 9B start rotating is appropriately selected according to conditions such as the shape and weight of the drum.

(Embodiment 2)
In the second embodiment, the hardness of the rolling element 9A of the balancer 8A is different from the hardness of the rolling element 9B of the balancer 8B.

  With this configuration, a difference is provided between the rolling elements 9A of the balancer 8A located at the front end and the rotational speeds at which rotational movement is started between the rolling elements 9B of the balancer 8B located at the rear end. It is possible to prevent the vibration of the drum 3 from increasing.

  As shown in FIG. 9, the time for the rolling element 9A to start rotating varies depending on the hardness. Accordingly, by selecting the hardness of the rolling element 9A and the hardness of the rolling element 9B, the difference between the time when the rolling element 9A of the balancer 8A starts rotating and the time when the rolling element 9B of the balancer 8B starts rotating. Can be set to a desired rotational speed.

  Further, the material of the sphere serving as the center of the rolling element 9A may be different from the material of the sphere serving as the center of the rolling element 9B. By making the materials different, the weights of the rolling elements 9A and the rolling elements 9B are different. Due to the difference in weight, the amount of movement by the propulsive force of the viscous fluids 10A and 10B differs. Therefore, by selecting the weight of the rolling element 9A and the weight of the rolling element 9B, the difference between the time when the rolling element 9A of the balancer 8A starts rotating and the time when the rolling element 9B of the balancer 8B starts rotating. Can be set to a desired rotational speed.

  The weights of the rolling elements 9A and 9B can be set by adjusting the material and diameter of the sphere that is the center of the rolling elements 9A and 9B.

  Further, the number of rolling elements 9A stored in the annular container of the balancer 8A may be different from the number of rolling elements 9B stored in the annular container of the balancer 8B.

The number of rolling elements 9A and the rolling elements 9B are such that the difference between the time when the rolling elements 9A of the balancer 8A starts rotating and the time when the rolling elements 9B of the balancer 8B starts rotating becomes the desired number of rotations. It can be set by selecting the quantity.
(Embodiment 3)
In the first and second embodiments described above, the annular container of the balancer 8A and the annular container of the balancer 8B are formed in the same size.

  In the third embodiment, one annular container is formed smaller than the other annular container. A small annular container also reduces the internal space. Therefore, by selecting the hardness, weight and quantity of the rolling elements 9A and 9b, and the liquid amount and viscosity of the viscous fluids 10A and 10B, the time for the rolling element 9A of the balancer 8A to start rotating and the balancer 8B The difference from the time when the rolling element 9B starts to rotate can be set so as to be a desired number of rotations.

  Further, the annular container of the balancer 8A and the annular container of the balancer 8B may be formed in the same size, and the inner space of one annular container may be formed smaller than the inner space of the other annular container.

  Also in this case, by selecting the hardness, weight and quantity of the rolling elements 9A and 9b, and the amount and viscosity of the viscous fluids 10A and 10B, the time for the rolling element 9A of the balancer 8A to start rotating and the balancer The difference from the time when the 8B rolling element 9B starts to rotate can be set to a desired number of rotations.

  In the present embodiment, the drum-type washing machine has been described. However, a device that performs a dehydrating operation using a drum-type washing dryer can obtain the same effect.

  When the washing machine according to the present invention includes a balancer at the front end portion and the rear end portion of the drum, when the moving body in the balancer starts to move, the moving body itself generates an unbalance and cannot be started. Therefore, it is useful as a drum-type washing machine or a cleaning device for home use or business use.

1 Drum-type washing machine 2 Water tank (washing tank)
DESCRIPTION OF SYMBOLS 3 Drum 3a Rotating shaft 8A Balancer 8B Balancer 9A Rolling element 9B Rolling element 10A Viscous fluid 10B Viscous fluid 12 Drive motor 18 Laundry 29 Projection body

Claims (6)

A drum rotatably supported by a horizontal or inclined rotating shaft;
A drive motor for rotationally driving the drum;
A water tank containing the drum;
An annular container for accommodating a rolling element and / or a moving body made of a viscous fluid, comprising a balancer disposed at a front end portion and a rear end portion of the drum;
When the drum starts rotating, the moving body in the annular container at the front end and the moving body in the annular container at the rear end stay at the drum container from the slip state where the moving body stays between the bottom and top of the annular container at different drum rotation speeds. A drum type washing machine characterized by starting to move beyond the upper part. A drum rotatably supported by a horizontal or inclined rotating shaft;
A drive motor for rotationally driving the drum;
A water tank containing the drum;
An annular container for storing rolling elements and viscous fluid, and comprising a balancer disposed at a front end portion and a rear end portion of the drum;
A drum type washing machine characterized in that the amount of liquid of the viscous fluid in the annular container of the balancer arranged at the front end is different from that of the viscous fluid in the annular container of the balancer arranged at the rear end. A drum rotatably supported by a horizontal or inclined rotating shaft;
A drive motor for rotationally driving the drum;
A water tank containing the drum;
An annular container for storing rolling elements and viscous fluid, and comprising a balancer disposed at a front end portion and a rear end portion of the drum;
A drum-type washing machine characterized in that the number of rolling elements of the annular container of the balancer arranged at the front end and the number of rolling elements of the annular container of the balancer arranged at the rear end are different. A drum rotatably supported by a horizontal or inclined rotating shaft;
A drive motor for rotationally driving the drum;
A water tank containing the drum;
An annular container for storing rolling elements and viscous fluid, and comprising a balancer disposed at a front end portion and a rear end portion of the drum;
A drum-type washing machine characterized in that the rolling elements of the annular container of the balancer arranged at the front end and the rolling elements of the annular container of the balancer arranged at the rear end are made different in hardness. A drum rotatably supported by a horizontal or inclined rotating shaft;
A drive motor for rotationally driving the drum;
A water tank containing the drum;
An annular container for storing rolling elements and viscous fluid, and comprising a balancer disposed at a front end portion and a rear end portion of the drum;
The rolling element is composed of a sphere serving as a center and a coating material applied to the surface of the sphere, and is disposed at the rear end of the rolling element of the annular container of the balancer disposed at the front end. A drum-type washing machine characterized in that the material of the sphere of the rolling element of the annular container of the balancer is made different. A drum rotatably supported by a horizontal or inclined rotating shaft;
A drive motor for rotationally driving the drum;
A water tank containing the drum;
An annular container for storing rolling elements and viscous fluid, and comprising a balancer disposed at a front end portion and a rear end portion of the drum;
A drum-type washing machine, wherein the balancer disposed at the front end and the balancer disposed at the rear end are different in size.

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