JP2011075295A - Tire dynamic balance measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase measurement accuracy by reducing the inclination and movements of an upper rim shaft during rotation. <P>SOLUTION: The upper rim shaft 14 is inserted into an insertion hole of a drive shaft 11 which is rotatingly driven integrally with lower rim shafts 5, 8, and a hollow operation sleeve 34 is allowed to slide at an engagement position. A plurality of balls 12 held at two vertically arranged points on the peripheral wall forming the insertion hole of the drive shaft 11 are thereby engaged with an annular groove 14a formed on the outer peripheral surface of the upper rim shaft 14 to lock the upper rim shaft 14 firmly at the two vertically arranged points in the circumferential direction. The upper rim shaft 14 is thereby prevented from inclining and moving during rotation to increase measurement accuracy. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  In the present invention, a lower rim provided on a rotatably supported lower rim shaft, and an upper rim disposed so as to be movable up and down at a position facing the lower rim, with the measured tire held between them. The present invention relates to a dynamic balance measuring device for a tire which can measure the dynamic balance of the tire to be measured by rotating it integrally.

  The tire dynamic balance measuring apparatus is generally provided in a lower rim provided on a lower rim shaft that is vertically supported through a bearing and driven to rotate, and can be moved up and down on the upper side facing the lower rim so as to be rotatable. When measuring the dynamic balance of the measured tire, the upper rim is configured so as to be integrally rotatable with the measured tire held between the two rims. In this dynamic balance measurement, in order to allow the upper rim and the lower rim to rotate integrally, the measured tire is firmly held between the upper rim shaft and the lower rim shaft, and then the pressure air is supplied to the tire. Enclose in. And it is necessary for the high-accuracy measurement to firmly connect the upper rim shaft and the lower rim shaft to reduce the core runout.

  In one conventional structure for obtaining a strong connection between the upper rim shaft and the lower rim shaft, the lower rim shaft is provided with an insertion hole into which the upper rim shaft is inserted, while the upper rim shaft has an outer periphery at its lower end. The upper rim shaft is inserted into the insertion hole of the lower rim shaft, and an engaging member such as a claw or a chuck provided on the lower rim shaft side is engaged with the engagement groove on the outer periphery of the lower end. By combining them, the upper rim shaft and the lower rim shaft are coupled and fixed (see, for example, Patent Document 1, Patent Document 2, etc.).

Japanese Patent Laid-Open No. 7-174658 Japanese Patent Laid-Open No. 5-240725

  In the conventional tire dynamic balance measuring apparatus having the above-described structure, the upper rim shaft has an engaging groove such as a claw or chuck provided on the lower rim shaft side in an engaging groove formed on the outer periphery of the lower end thereof. Since it is engaged and fixed, the upper and lower end surfaces of the engagement groove and the engagement member such as a claw or chuck can be in contact with each other, so that the displacement in the vertical direction (axial direction) can be regulated. However, it can be reliably prevented from coming out of the insertion hole of the lower rim shaft.

  However, there is a clearance of about 30 to 50 μm between the outer periphery of the upper rim shaft and the inner peripheral surface of the insertion hole of the lower rim shaft into which the upper rim shaft is inserted. In the hole, at one place in the axial direction of the upper rim shaft, it is fixed by the engagement of the engagement groove and the engagement member, so when holding and rotating the measured tire, The upper rim shaft tilts or swings with respect to the lower rim shaft, which is a rotational drive shaft, and there is a problem that the measurement accuracy of dynamic balance is lowered.

  The present invention has been made in order to solve the above-described problems. When measuring a dynamic balance while holding a measured tire between an upper rim and a lower rim, the present invention is applied to the lower rim shaft. The purpose is to increase the measurement accuracy by suppressing the tilt and deflection of the upper rim shaft.

In order to achieve the above object, a tire dynamic balance measuring device according to the present invention comprises a lower rim provided on a rotationally driven lower rim shaft, and an upper rim disposed so as to be movable up and down at a position facing the lower rim. In a tire dynamic balance measuring device for measuring the dynamic balance of a tire by attaching and rotating a tire in between,
A drive having an upper rim shaft extending downward from the upper rim and having a plurality of annular grooves formed on the outer peripheral surface thereof, an insertion hole into which the upper rim shaft is inserted while rotating integrally with the lower rim shaft A shaft and an operation member disposed on the outer periphery of the drive shaft so as to be slidable along the axial direction of the lower rim shaft;
A plurality of balls that can be engaged with and disengaged from the annular groove of the upper rim shaft are provided along the circumferential direction at each of at least two locations in the axial direction of the lower rim shaft on the peripheral wall forming the insertion hole of the drive shaft. Held at each position to be movable in the radial direction,
The operation member moves the ball held on the drive shaft radially inward to engage with the annular groove of the upper rim shaft inserted into the insertion hole, and radially outward of the ball. An engagement position that prevents the movement of the upper rim shaft on the drive shaft, and a release position that releases the engagement with the annular groove while allowing the ball to move radially outward. It can be slid over.

  According to the tire dynamic balance measuring apparatus of the present invention, the upper rim shaft is inserted into the insertion hole of the drive shaft, and the operating member is slid to the engagement position, whereby the peripheral wall forming the insertion hole of the drive shaft is formed. The plurality of held balls can be engaged and locked with an annular groove formed on the outer peripheral surface of the upper rim shaft, and the upper rim and the lower rim can be rotated together.

  In addition, the upper rim shaft is engaged and locked with a plurality of balls at respective positions along the circumferential direction in at least two positions in the axial direction of the lower rim shaft in the insertion hole of the drive shaft. The rim shaft can be firmly locked at two upper and lower positions in the axial direction, whereby the upper rim shaft can be prevented from being tilted or swung during rotation, and the measurement accuracy is improved.

  In a preferred embodiment of the present invention, the lower rim shaft is hollow, and the drive shaft has a cylindrical portion that forms the insertion hole, and the cylindrical portion is located in the lower rim shaft. The operation member has a cylindrical portion that is fitted on and slides on the cylindrical portion of the drive shaft in the lower rim shaft.

  According to this embodiment, the insertion is performed by concentrically disposing a hollow lower rim shaft and an insertion hole of a drive shaft disposed along the axial direction of the lower rim shaft in the lower rim shaft. The axial center of the upper rim shaft that is inserted into the hole and is engaged and locked by a plurality of balls at each position along the circumferential direction at each of the two axial positions is aligned with the axial center of the lower rim shaft. So-called centering can be performed with high accuracy.

  By engaging and locking the upper rim shaft thus inserted into the insertion hole with a plurality of balls at respective positions along the circumferential direction at two locations in the axial direction, the upper rim shaft and the lower rim shaft Therefore, the clearance between the outer periphery of the upper rim shaft and the inner peripheral surface of the insertion hole can be made larger than before, and insertion / removal of the upper rim shaft with respect to the insertion hole is facilitated.

  In another preferred embodiment of the present invention, the peripheral wall forming the insertion hole of the drive shaft penetrates in the radial direction at at least three positions at equal intervals in the circumferential direction at each of the two locations in the axial direction. In addition, a ball holding opening having a diameter at the opening end radially inward smaller than the diameter of the ball is formed, the ball is held in each opening, and the two axial directions are Is at least larger than the maximum outer diameter of the upper rim shaft.

  According to this embodiment, at each of two axial positions of the lower rim shaft, the upper rim shaft is moved by at least three balls held in at least three ball holding openings that are equally spaced in the circumferential direction. It can be locked in a stable state, and the distance between the two axial directions is larger than the maximum outer diameter of the upper rim shaft, so the upper rim shaft can be stabilized in the axial direction and tilted. , And can be effectively suppressed.

  In still another preferred embodiment of the present invention, the operating member is urged by an urging member on one side in the axial direction of the lower rim shaft, and the driving member resists the urging force of the urging member by the driving means. It slides on the other side in the axial direction.

  According to this embodiment, the operating member can be slid between the engagement position and the release position by the driving means and the biasing member.

  In still another preferred embodiment of the present invention, an annular recess into which the ball is fitted is formed in the inner peripheral surface of the operation member at the release position at at least two locations in the axial direction of the lower rim shaft. Has been.

  The dent may be a dent, and may be a groove or a notch.

  According to this embodiment, when the operating member is in the release position, the ball held on the peripheral wall of the drive shaft can be retracted from the insertion hole by fitting into the annular recess formed on the inner peripheral surface of the operating member. Therefore, in this state, it is possible to insert / remove the upper rim shaft into / from the insertion hole.

  According to the present invention, the upper rim shaft is inserted into the insertion hole of the drive shaft that is rotationally driven integrally with the lower rim shaft, and the operation member is slid to the engagement position, whereby the insertion hole of the drive shaft is formed. A plurality of balls held on the peripheral wall to be formed can be engaged and locked with an annular groove formed on the outer peripheral surface of the upper rim shaft, and the upper rim and the lower rim can be rotated together.

  In addition, the upper rim shaft is engaged and locked by a plurality of balls at respective positions along the circumferential direction in each of at least two locations in the axial direction of the lower rim shaft in the insertion hole of the drive shaft. The upper rim shaft can be firmly locked at two upper and lower positions in the axial direction, whereby the upper rim shaft can be prevented from being tilted or swung during rotation, and the measurement accuracy is improved.

FIG. 1 is a longitudinal sectional view of a tire dynamic balance measuring apparatus according to an embodiment of the present invention. FIG. 2 is a cutaway sectional view of the apparatus of FIG. 1 as viewed from the side. FIG. 3 is an enlarged view showing a main part of FIG. 4A is a cross-sectional view taken along section line (4a)-(4a) in FIG. 3, and FIG. 4B is a cross-sectional view taken along section line (4b)-(4b) in FIG. is there. 5A, 5B, and 5C are partially enlarged cross-sectional views for explaining engagement and disengagement between the upper rim shaft and the drive shaft of the lower rim.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  A tire dynamic balance measuring apparatus according to an embodiment of the present invention will be described with reference to FIGS. 1 to 4. 1 is a longitudinal sectional view of the tire dynamic balance measuring device, FIG. 2 is a cutaway sectional view of the device of FIG. 1 viewed from the side, FIG. 3 is a partially enlarged view of the main part of FIG. ) Is a cross-sectional view seen from the section line (4a)-(4a) in FIG. 3, and FIG. 4 (b) is a cross-sectional view seen from the section line (4b)-(4b) in FIG.

  In these drawings, the tire dynamic balance measuring apparatus according to the embodiment includes a casing 1 supported in a vertical state on a frame (not shown). The casing 1 includes a cylindrical upper casing 2 and a lower casing 3.

  In the upper casing 2, a hollow rotary shaft 5 is rotatably supported by a pair of upper and lower axial bearings 6 and 7. The hollow rotating shaft 5 has a hollow small-diameter shaft portion 5a extending in the vertical direction, and a hollow large-diameter shaft portion 5b protruding upward from the upper casing 2 at the axial upper end of the hollow small-diameter shaft portion 5a. The lower end of the cylindrical ring shaft 8 is fixed to the upper end of the hollow large-diameter shaft portion 5b. A cylindrical sleeve 9 is attached to the inner periphery of the ring shaft 8.

  The ring shaft 8 includes a large-diameter flange portion 8a at the upper end in the axial direction, a shaft portion 8b, and a small-diameter flange portion 8c at the lower end in the axial direction. The lower rim 4 is fixed to the large diameter flange portion 8a.

  The ring shaft 8 and the hollow rotary shaft 5 having the above configuration constitute a lower rim shaft that rotationally drives the lower rim 4. In the following description, for convenience and understanding, the ring shaft 8 and the hollow rotary shaft 5 are both referred to as a lower rim shaft.

  The lower rim 4 includes a rim body 10 on the radially outer peripheral side and a drive shaft 11 on the radially inner peripheral side, both of which are fixed to a ring shaft (lower rim shaft) 8.

Above the lower rim 4, an upper rim 13 that is lifted and lowered by a lifting mechanism (not shown) is disposed. An upper rim shaft 14 is provided at the center of the lower surface of the upper rim 13 so as to be integrally rotatable.
The upper rim shaft 14 has a hollow shaft portion, and on the outer periphery thereof, a plurality of arc-shaped annular grooves 14a are formed adjacent to each other in the axial direction. The pitch in the axial direction of the plurality of annular grooves 14 corresponds to the rim width of the tire 16 to be measured.

  The upper rim shaft 14 has a plurality of openings 14b at equal intervals in the circumferential direction of the opening 14b at the lower end surface in the axial direction and the outer peripheral surface in the axial direction, and four openings 14c in this embodiment, and these openings 14b and 14c are arranged in the axial direction. And a communication hole 15 communicating with each other. The openings 14 b and 14 c and the communication hole 15 in the upper rim shaft 14 serve as an air supply path to the inside of the measured tire 16 mounted between the upper rim 13 and the lower rim 4.

The upper casing 2 is suspended and supported by a frame (not shown) via a pair of parallel torsion bars 17 and 18 as shown in FIG. The upper casing 2 is also supported on a frame (not shown) by a pair of torsion bars 19 and 20 parallel to the horizontal direction (perpendicular to the paper surface), as shown in FIG.
As shown in FIG. 1, the lower casing 3 is supported on a frame (not shown) by a pair of torsion bars 21 and 22 parallel to the horizontal direction (perpendicular to the paper surface).

  As shown in FIG. 2, the upper casing 2 and the lower casing 3 are provided with load detectors 23 a and 23 b such as two load cells, and the load detectors 23 a and 23 b are connected to a frame 24. Yes. The load detectors 23a and 23b detect a displacement load acting on the casing 1 in the left-right direction in FIG. 1 (perpendicular to the paper surface in FIG. 2).

  A pulley 25 is fixed in the lower casing 3 to the lower end of the hollow small-diameter shaft portion 5 a of the hollow rotating shaft (lower rim shaft) 5 that is rotatably supported in the upper casing 2. As shown in FIG. 2, a belt 26 is stretched between the pulley 25 and a servo motor (not shown) which is a rotational drive source of the pulley 25, and the pulley 25, Therefore, the hollow rotary shaft (lower rim shaft) 5 is rotationally driven. A hollow encoder (not shown) for detecting the rotational position is attached to the hollow small-diameter shaft portion 5a of the hollow rotating shaft (lower rim shaft) 5.

  A hollow cylindrical operation member 27 is slidably fitted in a predetermined stroke in the axial direction in the hollow interior of each of the hollow rotating shaft (lower rim shaft) 5 and the ring shaft (lower rim shaft) 8 above it. ing.

  The operation member 27 includes a hollow operation rod 33 extending in the axial direction and a hollow operation sleeve 34 fixed to the upper end thereof.

  The operation member 27 is urged downward by a spring 28 disposed on the outer periphery of the hollow operation rod 33. As shown in FIG. 1, an annular flange portion 33 a is formed on the outer periphery of the lower end of the hollow operation rod 33, and this flange portion 33 a serves as a drive means that pushes up against the urging force of the spring 28. An air cylinder 29 is provided.

  The operation member 27 can be driven up and down by an air cylinder 29 via a push-up member 30 connected to the piston rod 29 a of the air cylinder 29. Further, a rotary joint 31 connected to a compressor is connected to the lower end opening of the hollow operation rod 33 of the operation member 27 so that air can be supplied into the hollow while allowing the operation member 27 to rotate. Yes.

  Next, the rotation of the hollow rotation shaft (lower rim shaft) 5 that is rotationally driven by a servo motor (not shown), and the ring shaft (lower rim shaft) 8 and the lower rim 4 integrated therewith are transmitted to the upper rim 13. The configuration for this will be described in detail.

  As shown in FIGS. 5A to 5C, the drive shaft 11 on the inner peripheral side of the lower rim 4 has a cylindrical shaft portion 11a extending in the axial direction. As shown in FIG. 5A, an insertion hole 32 into which the upper rim shaft 14 of the upper rim 13 is inserted is formed. The insertion hole 32 is formed so as to be located on the center line of the hollow rotary shaft 5 and the ring shaft 8 which are lower rim shafts.

    4 (a) and 4 (a), which are cross-sectional views seen from the cutting plane lines (4a)-(4a), (4b)-(4b) in FIG. (B) As shown in each, a plurality of ball holding openings 11b are formed at equal intervals in the circumferential direction, eight in this embodiment, penetrating in the radial direction and having a reduced diameter inward in the radial direction. The The diameter of the opening end in the radial direction of the opening 11b is smaller than the diameter of the ball 12 for locking. In addition, since the cross-sectional structure seen from each cut surface line (4a)-(4a), (4b)-(4b) is the same structure, the code | symbol is made the same for convenience of illustration. A lock ball 12 that engages with the circular annular groove 14a of the upper rim shaft 14 is accommodated in each of the openings 11b formed in each of the two peripheral walls in the axial direction of the shaft portion 11a. Each ball 12 is held so as to be movable in the radial direction so that a part of the ball 12 can advance into the insertion hole 32 or retreat out of the insertion hole 32. In order to stably fix the upper rim shaft 14, the axial distance between the upper and lower two positions where the balls 12 are arranged is preferably larger than the maximum outer diameter of the upper rim shaft 14. The distance is set to 1.5 times the maximum outer diameter of the rim shaft 14.

  On the outer periphery of the cylindrical shaft portion 11a, a hollow operating sleeve 34 of the operating member 27 is disposed so as to be slidable in the axial direction up and down with a predetermined stroke, and the engagement of the ball 12 with the annular groove 14a or its The disengagement can be operated.

  The upper inner peripheral surface of the hollow operation sleeve 34 is formed so that a part of the ball 12 is advanced into the insertion hole 32 of the shaft portion 11a, and a part of the ball 12 is radially outward from the insertion hole 32. An annular recess 34a and an annular notch 34b, which are depressions into which the ball 12 is fitted, are respectively formed in the axial direction so as to be retracted in the axial direction at a predetermined interval.

  As described above, the operating member 27 is urged downward by the spring 28, and in this urging position, as shown in FIGS. 1 to 4 and FIG. The inner peripheral surface presses the ball 12 so that a part of the ball 12 advances into the insertion hole 32, and two axially upper and lower portions are formed in the annular groove 14 a of the upper rim shaft 14 inserted in the insertion hole 32. By engaging eight balls 12 in the circumferential direction, the upper rim shaft 14 is fastened and fixed by the drive shaft 11 of the lower rim 4 at two places, upper and lower, and eight places on the entire circumference. In this engagement position, the rotation of the drive shaft 11 of the lower rim 4 is transmitted to the upper rim shaft 14 of the upper rim 13 and the upper rim shaft 14 and the drive shaft 11 are aligned.

  On the other hand, when the operating member 27 is pushed up against the urging force of the spring 28 by the air cylinder 29, as shown in FIGS. 5 (a) and 5 (b), the inside of the upper part of the hollow operating sleeve 34 of the operating member 27 is provided. An annular recess 34a and an annular notch 34b on the peripheral surface face the ball 12 in the opening 11b of the shaft portion 11a, respectively, and a part of the ball 12 can be retracted radially outward from the insertion hole 32, The engagement with the 12 annular grooves 14a is released. At this release position, the upper rim 13 is raised by an elevating device (not shown), and the upper rim shaft 14 of the upper rim 13 is removed from the insertion hole 32, or the upper rim 13 is lowered and the upper rim shaft 14 is lowered. It can be inserted into the insertion hole 32.

  Next, a procedure for measuring the dynamic balance of the tire using the tire dynamic balance measuring device will be described.

  First, the operating member 27 is raised by the air cylinder 29, and as shown in FIG. 5A, the annular recess 34a and the annular notch 34b on the upper inner peripheral surface of the hollow operation sleeve 34 are respectively connected to the balls 12 of the shaft portion 11a. A part of the ball 12 can be retracted from the insertion hole 32 to the outside (radially outward). In this state, the upper rim shaft 14 is raised by an elevating device (not shown) and extracted from the insertion hole 32.

  Then, the measured tire 16 is placed on the upper surface of the lower rim 4. Next, the upper rim 13 is lowered and brought into close contact with the upper surface of the tire 16 to be measured, and as shown in FIGS. 5 (a) to 5 (b), the upper rim shaft 14 is inserted into the insertion hole of the shaft portion 11a. 32 is inserted.

  Next, by releasing the lift by the air cylinder 29, the operation member 27 is displaced downward by the biasing force of the spring 28, and the upper inner peripheral surface of the hollow operation sleeve 34 detaches a part of the ball 12 from the shaft portion 11a. Is pushed inward in the radial direction so as to advance into the insertion hole 32, whereby the ball 12 engages with the annular groove 14 a on the outer periphery of the upper rim shaft 14 and enters a locked state.

  In this state, pressurized air is supplied into the measured tire 16 through a passage provided inside the operation member 27 and the communication hole 15 of the upper rim shaft 14. Then, a servo motor (not shown) is driven, and the hollow rotating shaft (lower rim shaft) 5, the ring shaft (lower rim shaft) 8, the upper and lower rim portions 13, 4, and the device to be measured are coupled together. The tire 16 is rotated, the output signals of the load detectors 23a and 23b during the rotation of the measured tire 16 are read, and thereby the dynamic balance of the measured tire 16 is measured.

  As described above, in this embodiment, the upper rim shaft 14 is inserted into the insertion hole 32 of the drive shaft 11 on the side of the lower rim shafts 5 and 8, and the lower rim shafts 5 and 8 are respectively located at two locations in the vertical direction. Since the eight balls 12 held at equal circumferential positions are respectively engaged with the annular grooves 14a of the upper rim shaft 14 and locked, the upper rim shaft 14 is inserted into the lower rim within the insertion hole 32. It will be firmly fixed concentrically with the shafts 5 and 8, and the upper rim shaft 14 will be prevented from tilting or swinging during rotation, thereby improving measurement accuracy.

  Specifically, compared with the conventional example described in Patent Document 1, that is, the conventional example in which the upper rim shaft is fixed with the claws provided on the lower rim shaft side, in this embodiment, the same tire is used a plurality of times. The variation in the measured value when measured was reduced to about ½.

  In addition, the upper rim shaft 14 is locked by the eight balls 12 arranged at equal intervals in the circumferential direction at each of the two upper and lower portions in the axial direction, so that the upper rim shaft 14 is moved to the lower rim shaft 5. , 8 is concentrically fixed, so that the clearance between the outer periphery of the upper rim shaft 14 and the inner peripheral surface of the insertion hole 32 is larger than, for example, about 30 to 50 μm, for example, about 0.1 mm. Thus, the insertion and removal of the upper rim shaft 14 from the insertion hole 32 is facilitated.

The present invention is useful as a dynamic balance measuring device for tires for measuring the balance of tires.

4 Lower rim 5 Hollow rotating shaft (lower rim shaft)
8 Ring shaft (lower rim shaft)
DESCRIPTION OF SYMBOLS 11 Drive shaft 11a Shaft part 11b Opening 32 Insertion hole 12 Ball 13 Upper rim 14 Upper rim shaft 14a Annular groove 16 Tire to be measured 27 Operation member 33 Hollow operation rod 34 Hollow operation sleeve 34a Annular recess 34b Annular notch 28 Spring 29 Air cylinder

Claims (5)

For tires that measure the dynamic balance of a tire by attaching and rotating a tire between a lower rim provided on a rotationally driven lower rim shaft and an upper rim that can be moved up and down at a position facing the lower rim. In the dynamic balance measuring device,
A drive having an upper rim shaft extending downward from the upper rim and having a plurality of annular grooves formed on the outer peripheral surface thereof, an insertion hole into which the upper rim shaft is inserted while rotating integrally with the lower rim shaft A shaft, and an operating member disposed on the outer periphery of the drive shaft so as to be slidable along the axial direction of the lower rim shaft,
A plurality of balls that can be engaged with and disengaged from the annular groove of the upper rim shaft are provided along the circumferential direction at at least two locations in the axial direction of the lower rim shaft on the peripheral wall forming the insertion hole of the drive shaft. Held at each position to be movable in the radial direction,
The operation member moves the ball held on the drive shaft radially inward to engage with the annular groove of the upper rim shaft inserted into the insertion hole, and radially outward of the ball. An engagement position that prevents the movement of the upper rim shaft on the drive shaft, and a release position that releases the engagement with the annular groove while allowing the ball to move radially outward. A tire dynamic balance measuring device characterized by being slidable over the distance. The lower rim shaft is hollow;
The drive shaft has a cylindrical portion that forms the insertion hole, and the cylindrical portion is disposed in the lower rim shaft so as to extend in the axial direction of the lower rim shaft,
2. The tire dynamic balance measuring device according to claim 1, wherein the operation member has a cylindrical portion that is fitted on and slides on the cylindrical portion of the drive shaft in the lower rim shaft.   In the peripheral wall forming the insertion hole of the drive shaft, at least two positions in the circumferential direction at the two positions in the axial direction are radially penetrated and radially inwardly opened. A ball holding opening having an end diameter smaller than the diameter of the ball is formed, the ball is held in each opening, and the axial distance between the two locations is at least that of the upper rim shaft. The tire dynamic balance measuring device according to claim 1 or 2, wherein the tire dynamic balance measuring device is larger than a maximum outer diameter.   The operation member is urged by an urging member on one side in the axial direction of the lower rim shaft, and slides to the other side in the axial direction against the urging force of the urging member by a driving unit. 4. The tire dynamic balance measuring device according to any one of 3 to 3.   5. An annular recess into which the ball fits in the release position is formed on the inner peripheral surface of the operation member at at least two locations in the axial direction of the lower rim shaft. The dynamic balance measuring device for tires described in 1.

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