Balancer device

Abstract

A balancer device (100) includes a housing (10) having a cylindrical body portion (11), a front end plate (12), and a rear end plate (13) that close both ends of the body portion (11) in the axial direction; a rod (20) that penetrates the front end plate (12) in the plate thickness direction and is supported so as to be movable in the axial direction; a movable member (30) that is fixed to the rod (20) and is housed in the housing (10); a compression coil spring (40) that is disposed between the movable member (30) and the rear end plate (13); and a connection member (50) that connects the rod (20) and the rear end plate (13) in such a manner that the rod (20) has a larger play than the stroke in the axial direction.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a balancer device. BACKGROUND

[0002] A robot gravity balancer is known in which a compression coil spring inside a housing exerts a force in a direction in which a shaft is pushed out of the housing, thereby reducing a load moment caused by gravity acting on a first arm of a robot (see, for example, Patent Literature 1).

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2019-188513 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] In the robot gravity balancer of Patent Literature 1, the rebound force of the compressed compression coil spring always acts on an end plate of the housing on the side opposite the shaft, and in the case where the housing is broken, the detached end plate can fly out to the outside.

[0008] Therefore, it is desirable to prevent the end plate from flying out even in the case where the housing is broken.

[0009] SOLUTION TO PROBLEM

[0010] An aspect of the present disclosure is a balancer device including: a housing including a cylindrical body portion, and a front end plate and a rear end plate that close both ends of the body portion in an axial direction; a shaft that penetrates the front end plate in a plate thickness direction and is supported so as to be movable in the axial direction; a movable member that is fixed to the shaft and is housed in the housing; a compression coil spring that is disposed between the movable member and the rear end plate; and a connection member that connects the shaft and the rear end plate in such a manner that a play larger than a stroke of the shaft is provided in the axial direction. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a side view of a hanging robot including the balancer device of the first embodiment of the present disclosure.

[0012] Figure 2 is a longitudinal sectional view of the balancer device shown in Figure 1

[0013] Figure 3 is a perspective view of a longitudinal cross section of the connection member of the balancer device shown in Figure 1

[0014] Figure 4 ​​It shows Figure 1 A longitudinal sectional view of a balancer device showing a state in which the rear end plate and the main body are separated.

[0015] Figure 5 It shows Figure 1 A longitudinal sectional view of a first modified example of the balancer device is shown.

[0016] Figure 6 It shows Figure 1 A longitudinal sectional view of a second modified example of the balancer device is shown.

[0017] Figure 7 It shows Figure 1 A longitudinal sectional view of a third modified example of the balancer device is shown.

[0018] Figure 8 It is a longitudinal sectional view showing a state in which the compression coil spring of the balancer device according to the second embodiment of the present disclosure is maximally compressed.

[0019] Figure 9 It shows Figure 8 A longitudinal sectional view of a balancer device showing a compression coil spring in a most extended state.

[0020] Figure 10 It shows Figure 8 A longitudinal sectional view of a first modified example of the balancer device.

[0021] Figure 11 It shows Figure 8 A longitudinal sectional view of a second modified example of the balancer device.

[0022] Figure 12 It shows Figure 8 A longitudinal sectional view of a third modified example of the balancer device.

[0023] Figure 13 It shows Figure 8 A longitudinal sectional view of a fourth modified example of the balancer device. DETAILED DESCRIPTION

[0024] Hereinafter, a balancer device 100 according to a first embodiment of the present disclosure will be described with reference to the drawings.

[0025] like Figure 1 As shown, the balancer device 100 of the present embodiment is mounted on a ceiling-mounted robot 1 installed in a state of being suspended from a ceiling, for example.

[0026] The ceiling-mounted robot 1 includes a base 2 mounted on a ceiling, a rotating body 3 supported for rotation relative to the base 2 about a first axis J1 extending in the vertical direction, and an arm 4 supported for rotation relative to the rotating body 3 about a second axis J2 extending in the horizontal direction. A balancer device 100 is disposed between the rotating body 3 and the arm 4.

[0027] like Figure 2 As shown, the balancer device 100 includes a housing 10 , a rod 20 , a movable member 30 , a compression coil spring 40 , and a connecting member 50 .

[0028] The housing 10 includes a cylindrical main body 11 , and a flat front end plate 12 and a flat rear end plate 13 that close both ends of the main body 11 in the direction of a central axis (axis) OL1 .

[0029] The front end plate 12 and the rear end plate 13 are fixed to the main body 11, for example, by bolts (not shown). Alternatively, either the front end plate 12 or the rear end plate 13 may be integral with the main body 11. A through-hole extending through the front end plate 12 in the thickness direction is provided at the center. A through-hole 13h extending through the rear end plate 13 in the thickness direction is provided at the center. Multiple threaded holes are provided around the through-hole 13h.

[0030] The rod 20 is supported so as to be movable relative to the housing 10 in a direction along the central axis OL1 by a bearing 12b disposed in a through-hole provided in the front end plate 12. Alternatively, the bearing 12b may be integral with the front end plate 12 rather than being a separate component. A mounting block 21 is fixed to one end of the rod 20 disposed outside the housing 10 for attaching the rod 20 to the arm 4.

[0031] A movable member 30 is fixed to the other end of the rod 20 disposed inside the housing 10. The movable member 30 is formed in the shape of a disk having an outer diameter slightly smaller than the inner diameter of the main body 11 of the housing 10, and is fixed to the other end of the rod 20 by, for example, a nut fastened to an external thread formed on the other end of the rod 20.

[0032] The compression coil spring 40 is housed within the main body 11 of the housing 10 and is disposed in a compressed state between the rear end plate 13 and the movable member 30. As a result, the movable member 30 is constantly pressed toward the front end plate 12 by the repulsive force of the compression coil spring 40, thereby pushing the rod 20 outward from the housing 10.

[0033] like Figure 2 as well as Figure 3 As shown, the connecting member 50 includes a first connecting piece (first member) 51 fixed to the rear end plate 13 and a second connecting piece (second member) 52 fixed to the movable member 30 .

[0034] The first connecting piece 51 includes a cylindrical main body 51a having an outer diameter smaller than the inner diameter of the through-hole 13h in the rear end plate 13, and a flange-shaped mounting seat 51b. The main body 51a has an outer diameter smaller than the inner diameter of the through-hole 13h in the rear end plate 13. The mounting seat 51b protrudes radially outward from the outer circumference of one end of the main body 51a and has an outer diameter larger than the inner diameter of the through-hole 13h. Furthermore, the first connecting piece 51 includes a flange-shaped stopper 51c protruding radially inward from the inner circumference of the other end of the main body 51a.

[0035] The mounting seat surface 51b is provided with a plurality of through-holes extending axially through the main body portion 51a. With the main body portion 51a inserted from the outside into the through-holes 13h of the rear end plate 13, the first connecting piece 51 is secured to the rear end plate 13 by fastening bolts 15 extending through the through-holes of the mounting seat surface 51b to threaded holes in the rear end plate 13.

[0036] The second connecting piece 52 includes a cylindrical main body 52a and a flange-shaped abutment portion (abutment surface) 52b. The main body 52a has an outer diameter that can penetrate the radially inner side of the stopper 51c. The abutment portion 52b protrudes radially outward from the outer circumference of one end of the main body 52a and is larger than the inner diameter of the stopper 51c. Furthermore, the second connecting piece 52 includes a flange-shaped base plate 52c that protrudes radially inward from the inner circumference of the other end of the main body 52a. The base plate 52c is provided with a through hole that extends axially through the main body 52a and allows the external thread of the rod 20 to pass through.

[0037] The second connecting piece 52 is fixed to the rod 20 together with the movable member 30 by passing the external thread of the rod 20 through the through hole of the bottom plate 52 c and fastening the second connecting piece 52 with a nut fastened to the external thread of the rod 20 .

[0038] The position of the rod 20 relative to the housing 10 changes accordingly according to the rotation angle of the arm 4 relative to the rotating body 3. In this case, throughout the entire stroke range of the rod 20 corresponding to the range of motion of the arm 4, the abutting portion 52b of the second connecting piece 52 and the stopper 51c of the first connecting piece 51 are arranged with a gap therebetween, maintaining a non-contact positional relationship.

[0039] That is, the connecting member 50 connects the movable member 30 and the rear end plate 13 with a play larger than the stroke of the rod 20 in the direction of the central axis OL1 .

[0040] A pair of first mounting holes 16 extending along an axis OL2 orthogonal to the central axis OL1 are provided on both sides of the main body 11 of the housing 10 at a position midway along the central axis OL1. A pair of first shafts (not shown) fixed to the rotating body 3 are inserted into each first mounting hole 16. The first shafts are arranged on the same straight line extending along a first mounting axis J11 parallel to the second axis J2.

[0041] Thus, the housing 10 is mounted on the rotating body 3 so as to be rotatable about the first mounting axis J11 .

[0042] The mounting block 21 is provided with a second mounting hole 22 extending perpendicularly to the central axis OL1. A second shaft (not shown) fixed to the arm 4 is inserted into the second mounting hole 22. The second shaft extends along a second mounting axis J12 parallel to the second axis J2. Thus, the distal end of the rod 20 is rotatably mounted on the arm 4 about the second mounting axis J12.

[0043] Next, the operation of the balancer device 100 according to the present embodiment configured in this manner will be described.

[0044] In the ceiling-mounted robot 1 equipped with the balancer device 100 of this embodiment, for example, Figure 1 As shown in FIG. 2 , when the arm 4 is extended forward, a gravity load moment GF in a direction around the second axis J2 acts on the arm 4 due to gravity.

[0045] On the other hand, the balancer device 100 pushes the rod 20 outward from the housing 10 using the rebound force of the compression coil spring 40. This force acts on the second mounting axis J12 eccentric from the second axis J2, thereby generating an assist torque in a direction resisting the gravity load moment.

[0046] In this case, the compression amount of the compression coil spring 40 provided in the balancer device 100 is such that the arm 4 is compressed. Figure 1 The spring force is smallest when the arm 4 is extended forward and rearward, and largest when the arm 4 is extended vertically downward. The compression coil spring 40 has a very large spring constant, generating sufficient assist torque even at its minimum compression. Therefore, the rear end plate 13 is constantly pushed rearward by the large repulsive force of the compression coil spring 40.

[0047] Therefore, for example, if the body 11 of the housing 10 and the rear end plate 13 are broken due to some reason such as deterioration caused by long-term operation, the rear end plate 13 tends to fly out rearward.

[0048] In this case, if Figure 4 As shown, since the distance between the rear end plate 13 and the movable member 30 increases, the stopper 51c and the abutment portion 52b abut against each other, and the rear end plate 13 is restricted from further rearward movement.

[0049] In addition, since the first connecting piece 51 and the second connecting piece 52 do not contact each other during operation, there is no large rebound force generated by the compression coil spring 40, and fatigue caused by stress will not accumulate even if the operation is long-term.

[0050] Therefore, the first connecting piece 51 and the second connecting piece 52 are less likely to deteriorate than the case 10 which is always subjected to the rebound force of the compression coil spring 40, and thus even if the case 10 is broken due to deterioration, the flying out of the rear end plate 13 can be reliably prevented.

[0051] In addition, in the present embodiment, the stopper 51c is disposed closer to the movable member 30 than the rear end plate 13 by using the space on the inner side of the compression coil spring 40, and thus the abutting portion 52b can also be correspondingly closer to the movable member 30.

[0052] That is, since the abutting portion 52b is closer to the bottom plate 52c, it has an advantage that the axial dimension of the second connecting piece 52 can be suppressed to be small.

[0053] Furthermore, by forming the main body portion 51a of the first connecting piece 51 in a cylindrical shape and housing the abutting portion 52b inside thereof, it also has an advantage that the radial dimension of the second connecting piece 52 provided with the abutting portion 52b can be suppressed to be small.

[0054] In addition, in the present embodiment, the main body portion 52a is also cylindrical in addition to the main body portion 51a, and thus the through hole provided to the bottom plate 52c can be seen from the outside of the rear end plate 13 side. Thereby, the external thread of the rod 20 which passes through the bottom plate 52c and the nut which is fastened to the external thread can be easily accessed from the outside.

[0055] That is, the connecting member 50 can be attached and detached from the outside of the case 10, and the workability of the assembly and disassembly work of the balancer device 100 can be improved.

[0056] Further, in the present embodiment, the first connecting piece 51 provided with the stopper 51c is provided separately from the rear end plate 13 and is fixed to the rear end plate 13 by the bolt 15, but instead, as shown in Figure 5 , the first connecting piece 51 can be integrated with the rear end plate 13.

[0057] In this case, the bolt 15 for fixing the first connecting piece 51 to the rear end plate 13 is not needed, and the number of components and assembly man-hours can be reduced.

[0058] Further, as shown in Figure 6 , the peripheral portion of the through hole 13h of the rear end plate 13 can also be used as the stopper 51c.

[0059] In this case, the abutting portion 52b of the second connecting piece 52 has an outer diameter larger than the inner diameter of the through hole 13h of the rear end plate 13, and in a state where the main body portion 52a is inserted from the outside of the through hole 13h, the second connecting piece 52 is fixed to the movable member 30. Thereby, the rear end plate 13 can be formed in a simpler shape.

[0060] In addition, in the present embodiment, the main body 52a of the second connection piece 52 is cylindrical, but the main body 52a may be rod-shaped instead.

[0061] In this case, there is an advantage that the structure of the second connecting piece 52 can be simplified.

[0062] In addition, in the present embodiment, the connection member 50 may be formed of a flexible linear member such as a metal wire.

[0063] In this case, for example, Figure 7 As shown, one end of the connecting member 50 is ring-shaped, and by fastening a bolt 17 passing through the inner side of the ring to the rear end plate 13, the one end of the connecting member 50 is sandwiched between the bolt head of the bolt 17 and the rear end plate 13 and fixed. Similarly, the other end of the connecting member 50 is fixed to the movable member 30, and the length of the portion of the connecting member 50 spanning between the rear end plate 13 and the movable member 30 is set to be slightly longer than the maximum stroke of the rod 20.

[0064] Thus, the connecting member 50 bends throughout the entire stroke of the rod 20 , but when the housing 10 separates and the distance between the rear end plate 13 and the movable member 30 increases, the connecting member 50 is tensioned without bending, thereby restricting rearward movement of the rear end plate 13 .

[0065] Therefore, the balancer device 100 can be made into a simpler structure and the rear end plate 13 can be prevented from flying backward. In addition, there is the following advantage: when the housing 10 is not separated, the connecting member 50 can be freely bent and can be accommodated in the housing 10 with good space efficiency, thereby achieving miniaturization of the housing 10.

[0066] In addition, in this embodiment, the case where the housing 10 is broken between the main body 11 and the rear end plate 13 is exemplified, but the present invention is not limited thereto. Regardless of the breaking position of the housing 10 , the rear end plate 13 can be prevented from flying out.

[0067] Next, a balancer device 200 according to a second embodiment of the present disclosure will be described below with reference to the drawings. In the description of this embodiment, components identical to those of the balancer device 100 according to the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

[0068] In the balancer device 100 of the first embodiment, in order to ensure the clearance between the abutting portion 52b of the second member 52 and the stopper 51c of the first member 51, the second member 52 is formed to be elongated, and the abutting portion 52b is arranged at a position away from the movable member 30 in the direction along the central axis OL1. Figure 8As shown, the balancer device 200 of this embodiment has the second member 152 shorter in the direction along the central axis OL1 and the rod 120 longer in the same length as the length of the housing 10 in the direction along the central axis OL1. Figure 9 As shown, even in a state where the rod 120 is made to protrude maximally from the front end plate 12 , a clearance can be ensured between the abutting portion 52 b of the second member 152 and the stopper 51 c of the first member 151 .

[0069] Similar to the balancer device 100 of the first embodiment, the rod 120 includes a rod body 121 having a first outer diameter that engages with the bearing 12b, and a small-diameter portion (shock absorber) 122 having a second outer diameter smaller than the rod body 121 and positioned closer to the rear end plate 13 than the rod body 121. A step 123 is provided between the rod body 121 and the small-diameter portion 122, which abuts against the surface of the movable member 30 on the front end plate 12 side. Furthermore, an externally threaded portion (threaded portion) 124 capable of fastening a nut (fastener) 125 is provided closer to the rear end plate 13 than the small-diameter portion 122. Furthermore, similar to the first embodiment, the movable member 30 and the second member 152 are clamped and fixed between the nut 125 fastened to the externally threaded portion 124 and the step 123.

[0070] The length of the small-diameter portion 122 of the balancer device 200 of this embodiment is sufficiently longer than that of the balancer device 100 of the first embodiment, and is equivalent to the length of the first member 151 along the central axis OL1. Furthermore, a cylindrical spacer 70 having a through-hole 70a extending from the small-diameter portion 122 to the inner bore is sandwiched between the movable member 30 and the second member 152.

[0071] In this embodiment, the rod 120 and the second member 152 are made of carbon steel, and the first member 151 is a casting. Furthermore, the small-diameter portion 122 is the smallest diameter portion of the rod 120 and has a cross-sectional area smaller than the minimum cross-sectional area of ​​both the first member 151 and the second member 152. Furthermore, the diameter of the small-diameter portion 122 is set to a size that allows for elastic or plastic deformation in the longitudinal direction without breaking, even if the rear end plate 13 separates from the main body 11 and the stopper 51c of the first member 151 collides with the abutment portion 52b of the second member 152, exerting the maximum impact force assumed.

[0072] The outer peripheral edge of the end surface of the second member 152 on the front end plate 12 side is provided with a tapered surface 152a that tapers toward the front end plate 12 side, at a portion located radially outward of the outer peripheral surface of the spacer 70. Furthermore, an annular rubber plate (buffer member) 80 is fixed to the annular abutment portion 52b of the second member 152.

[0073] The operation of the balancer device 200 of the present embodiment configured in this manner will be described below.

[0074] According to the balancer device 200 of this embodiment, when the rear end plate 13 separates from the main body 11, the stopper 51c of the first member 151 collides with the abutment portion 52b of the second member 152, thereby preventing the rear end plate 13 from flying backward. In this case, the impact force generated by the collision is borne by the rod 120, the first member 151, and the second member 152. However, the small diameter portion 122 of the rod 120, which has a smaller cross-sectional area than the other portions, deforms the most.

[0075] According to this embodiment, since the small-diameter portion 122 is sufficiently long, the impact energy is absorbed by deforming the small-diameter portion 122 in the direction of the central axis OL1. In other words, by lengthening the small-diameter portion 122, a larger allowable strain can be ensured without breaking, thereby absorbing a correspondingly larger impact energy.

[0076] Furthermore, in this embodiment, by making the rod 120 longer and arranging the spacer 70, the second member 152 can be constructed more compactly than in the first embodiment. Since the second member 152 collides with the first member 151, it is made of a high-ductility, expensive material. Meanwhile, the spacer 70 is a member that does not require particular strength and can be constructed of a less expensive material. Therefore, the compact design of the second member 152 offers the advantage of reducing material and processing costs.

[0077] Furthermore, if the outer diameter of the spacer 70 is set smaller to reduce the weight of the spacer 70, the amount of radial outward protrusion of the second member 152 from the outer peripheral surface of the spacer 70 increases. However, the provision of the tapered surface 152a allows the stopper 51c to move along the tapered surface 152a even if it collides with the protruding portion, thus limiting the final collision to the abutment portion 52b of the second member 152. Furthermore, the provision of the rubber sheet 80 on the abutment portion 52b can mitigate the impact of the collision with the stopper 51c.

[0078] Furthermore, if Figure 8 As shown, by setting the length of the rod 120 to be equal to the length of the housing 10 along the central axis OL1, the second member 152 can be arranged in the housing 10 in the stored state even when the rod 120 is in the state of being maximally retracted into the housing 10. In this state, the length of the rod 120 can be longer while allowing the second member 152 to protrude out of the housing 10 further rearward than the rear end plate 13.

[0079] In addition, in this embodiment, the rear end plate 13 and the first member 151 are manufactured separately and assembled by bolts (not shown), but instead, they may be assembled as shown in FIG. Figure 10 The structure shown is integrated.

[0080] In this embodiment, the rod 120, the first member 151, and the second member 152 are formed of materials having equivalent tensile strengths, and the shape is set to satisfy the relationship of the cross-sectional area of ​​the small-diameter portion 122 < the minimum cross-sectional area of ​​the first member 151 and the second member 152. Alternatively, if the first member 151 and the second member 152 are formed of a material having a higher tensile strength than the rod 120, the above relationship does not need to be satisfied.

[0081] In addition, in this embodiment, the spacer 70 is held between the movable member 30 and the second member 152, but instead, as shown in FIG. Figure 11 As shown, the cylindrical portion 31 may be provided integrally with the movable member 30 instead of the spacer 70. This also allows the second member 152 to be compactly configured, thereby achieving cost reduction.

[0082] In addition, if Figure 12 As shown in FIG. 1 , the cylindrical portion 71 replacing the spacer 70 may be provided integrally with the second member. Figure 13 As shown, the spacer 70 sandwiched between the movable member 30 and the second member 152 may also be sandwiched between the second member 152 and the nut 125 .

[0083] In this embodiment, the shock absorbing portion that deforms due to an impact is formed by the small-diameter portion 122 of the rod 120. However, the shock absorbing portion may be provided on the first member 151 or the second member 152. Alternatively, the shock absorbing portion may be provided on two or more of the rod 120, the first member 151, and the second member 152.

[0084] In addition, an external thread portion 124 is provided at the front end of the rod 120, and a nut 125 fastened to the external thread portion 124 is exemplified as a fastener. However, an internal thread may be provided at the front end of the rod 120, and a bolt may be used as the fastener.

[0085] Description of Reference Numerals

[0086] 10 shell

[0087] 11Main part

[0088] 12 front end panel

[0089] 13 rear end plate

[0090] 20, 120 strokes

[0091] 30 movable components

[0092] 40 compression coil spring

[0093] 50 connecting components

[0094] 51, 151 first connecting piece (first component)

[0095] 51a Main body

[0096] 51c stopper

[0097] 52, 152 second connecting piece (second component)

[0098] 52b abutment portion (abutment surface)

[0099] 70 spacers

[0100] 70a through hole

[0101] 80 rubber sheet (buffer component)

[0102] 100, 200 balancer device

[0103] 122 Small diameter part (shock absorbing part)

[0104] 123 steps

[0105] 124 external thread part (thread part)

[0106] 125 nut (fastener)

[0107] 152a conical surface

[0108] OL1 center axis (axis)

Claims

1. A balancer device, characterized in that: have: a housing including a cylindrical main body portion, and a front end plate and a rear end plate closing both axial ends of the main body portion; a rod penetrating the front end plate in the plate thickness direction and supported so as to be movable along the axial direction; a movable member fixed to the rod and housed in the housing; a compression coil spring disposed in a compressed state between the movable member and the rear end plate; as well as A connecting member connects the rod and the rear end plate with a clearance in the axial direction that is larger than a stroke of the rod.

2. The balancer device according to claim 1, characterized in that The connecting member includes a first member fixed to the rear end plate and a second member fixed to the rod. The second member includes a contact surface that contacts the first member from the rear end plate side when the play disappears.

3. The balancer device according to claim 2, characterized in that The first member includes a main body extending from the rear end plate toward the front end plate in the axial direction, and a stopper provided at a front end of the main body on the front end plate side and abutting against the abutting surface.

4. The balancer device according to claim 3, characterized in that The main body is formed into a cylindrical shape with an inner hole. The second member is configured to house the front end of the rear end plate in the inner hole. The stopper extends in a flange shape on the inner peripheral surface of the front end of the main body in a direction perpendicular to the axis.

5. The balancer device according to claim 2, characterized in that An impact absorbing portion is provided on at least one of the rod, the first member and the second member. The impact absorbing portion does not break due to the impact when the abutting surface of the second member abuts the first member, but absorbs the energy of the impact by deforming in the axial direction.

6. The balancer device according to claim 5, characterized in that The shock absorbing portion is a small-diameter portion provided on the rod and having a cross-sectional area smaller than the minimum cross-sectional area of ​​the first member and the second member.

7. The balancer device according to claim 6, characterized in that The rod is configured to penetrate the movable member and the second member in the axial direction and has a step portion that abuts against the surface of the movable member on the front end plate side, and a threaded portion provided at the end portion on the rear end plate side and capable of fastening a fastener. The movable member and the second member are fixed to the rod by clamping the movable member and the second member in the axial direction between the fastener fastened to the threaded portion and the step portion. The small diameter portion is arranged between the step portion and the threaded portion.

8. The balancer device according to claim 7, characterized in that The small diameter portion has a length equivalent to a length of the first member in the axial direction.

9. The balancer device according to claim 7, characterized in that A cylindrical spacer is interposed between the movable member and the second member or between the second member and the fastener. The spacer includes a through hole through which the small-diameter portion passes.

10. The balancer device according to claim 9, characterized in that The second member includes a tapered surface that tapers toward the front end plate at a position further outward than the spacer.

11. The balancer device according to any one of claims 2 to 10, A buffer member is fixed to at least one of the contact surface of the second member or a surface of the first member that faces the contact surface in the axial direction.

12. The balancer device according to claim 1, wherein The connecting member is a flexible linear body having one end fixed to the movable member and the other end fixed to the rear end plate in a bent state.

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