JP2010090953A - Ball screw and pulley width driving mechanism with the same for v-belt type continuously variable transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ball screw improved in operation efficiency by improving operability in regard to a ball screw having a large diameter and a large number of balls, and to provide a pulley width driving mechanism with the same for a V-belt type continuously variable transmission. <P>SOLUTION: A shaft circulation type ball screw 1 is provided with ball circulation grooves 7 and 8 by forming two screw grooves 3a and 3b into a closed loop in a land part 6 existing between the screw grooves 3a and 3b adjacent to each other in the axial direction of a screw shaft 3, and these circulation grooves are formed into a nearly S-shape meandering so that balls 4 in the downstream of the screw grooves 3a and 3b are sunken toward an inner diameter side and returned to the upstream side, riding over a land part 9 of a nut 2. The screw grooves 3a and 3b of the screw shaft 3 and the ball circulation grooves 7 and 8 are formed into a predetermined finish shape by cutting, and a predetermined hard layer is formed in the surface thereof by high-frequency quench hardening, and assembled in a state that 10-20% of balls 4 relative to a number of balls in calculation possible to be arranged within one circuit are put out. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is used for driving a movable pulley of a belt type continuously variable transmission (CVT) of an automobile or the like, and is a ball screw formed with a helical thread groove on which a large number of balls roll, and more specifically, a screw for a ball TECHNICAL FIELD The present invention relates to a so-called shaft circulation type ball screw connected by a ball circulation groove that sinks into the inner diameter side of a shaft and returns from the downstream side to the upstream side, and a pulley width drive mechanism of a V-belt type continuously variable transmission equipped with the same. It is.

  A ball screw has a ball screw shaft composed of a ball screw shaft having a spiral thread groove formed on the outer periphery, a ball screw nut having a spiral thread groove formed in a cylindrical surface, and both opposing screw grooves. It is a mechanical element that is composed of a large number of balls that are rotatably accommodated in the road, and converts the rotation of the ball screw shaft or ball screw nut into translational motion in the axial direction.

  Conventionally, in a ball screw, in order to prevent the withdrawal of a large number of balls accommodated in the respective screw grooves, regardless of the expansion and contraction movement of the screw shaft and the nut, Both ends of the ball rolling path constituted by the above are connected in communication to form a closed loop, and the ball is infinitely circulated in the closed loop.

  Such ball screws generally have different ball circulation mechanisms, for example, various types such as a return tube and an end plate, and one of them is called a piece type. This piece-type ball screw has a threaded groove connection path, and a circulation piece member with a rolling path as a circulation path is attached to the nut. The structure is relatively simple and compact. There are advantages you can do.

  As shown in FIG. 9 (a), a conventional CVT movable pulley driving ball screw has a screw shaft 50 having a spiral thread groove 50a formed on the outer periphery thereof, and is fitted to the screw shaft 50. And a plurality of balls 52 accommodated in a freely rollable manner between the opposing screw grooves 50a and 51a. For example, as shown in (b), (c), and (d), the ball 52 includes a load ball 52a that supports a load and a spacer ball 52b having a smaller diameter than the load ball 52a. , 52b are arranged so that one spacer ball 52b is interposed between the two load balls 52a, 52a, so that the spacer ball 52b and the load ball 52a adjacent thereto are rotated forward. In addition, the relative slip between the balls is eliminated so that a smooth continuously variable transmission can be performed (for example, see Patent Document 1).

  However, in this type of ball screw, in order to align the connecting portion of the connecting groove formed in the piece member (not shown) serving as a circulating member and the screw groove 51a of the nut 51 with high accuracy, In addition to increasing the machining accuracy, it requires extremely troublesome and time-consuming positioning work, which increases costs and causes quality degradation due to misalignment. As a ball screw that solves such a problem, an axial circulation type ball screw is known which is connected by a ball circulation groove that sinks the ball into the inner diameter side of the screw shaft and returns it from the downstream side to the upstream side.

  As shown in FIG. 10, the ball screw 53 includes a nut 54, a screw shaft 55 inserted in the nut 54, a plurality of balls 56, and these balls 56 are arranged in a circumferentially uniform manner, A retainer ring (not shown) mounted in a state of being relatively immovably positioned in the axial direction with respect to the screw shaft 55 and being relatively rotatable, the opposing surface of the nut 54 and the screw shaft 55 The balls 56 are circulated between them.

  The nut 54 is formed with a single thread groove 54a continuous from one end to the other end. On the other hand, the screw shaft 55 is formed with approximately two winding thread grooves 55a and 55b that are not continuous in the middle region in the axial direction. The screw groove 54a of the nut 54 and the screw grooves 55a and 55b of the screw shaft 55 are set to the same lead angle.

  Here, a ball (land portion) 57 existing between two winding screw grooves 55a and 55b adjacent in the axial direction of the screw shaft 55 is a ball having the two winding screw grooves 55a and 55b individually as a closed loop. Circulation grooves 58 and 59 are provided. The ball circulation grooves 58 and 59 individually connect the upstream side and the downstream side of the two-turn screw grooves 55a and 55b. The balls 56 downstream of the screw grooves 55a and 55b sink into the inner diameter side. Further, it is formed in a meandering shape so as to get over the thread (land) 60 of the nut 54 and return to the upstream side.

Here, by reciprocating the nut 54 in the axial direction, the range in which the nut 54 and the screw shaft 55 overlap in the axial direction changes in size, but the screw shaft 55 is individually closed looped by the ball circulation grooves 58 and 59. The balls 56 roll and circulate while being guided by the cage ring in the two screw grooves 55a and 55b of the screw shaft 55, and the nut 54 is smoothly guided by a predetermined spiral motion. In the process in which the nut 54 reciprocates within a predetermined movement stroke range, it is possible to reliably prevent the ball 56 from coming off. This eliminates the need for alignment between the connecting groove and the screw groove associated with the piece-type ball screw, thereby enabling cost reduction and avoiding quality deterioration due to misalignment or the like (see, for example, Patent Document 2). .)
JP 2002-188705 A JP 2003-074665 A

  Here, the ball 56 is constituted by a load ball and a spacer ball like the ball screw of the above-mentioned cited document 1, and one spacer ball is arranged so as to be interposed between two load balls. The space between the spacer ball and the load ball adjacent to the spacer ball is rotated forward, so that the relative slip between the balls 56 is eliminated, and a smooth continuously variable transmission can be performed. However, in the ball screw for driving a movable pulley of CVT, since a shaft (not shown) needs to penetrate the screw shaft 55, the screw shaft 55 has a relatively large diameter. In addition, since the leads are small, the outer diameter of the balls 56 used is also small, and the number of balls accommodated in one circuit is inevitably increased to at least 60. In this case, it is necessary to accurately arrange the load ball and the spacer ball in the nut 54, but the spacer ball itself must be sized to have a small diameter of, for example, −40 μm to −50 μm with respect to the load ball. . Generally, such a ball diameter is not in stock as a standard product, and several types of spacer balls must be ordered as special products. This not only complicates the assembly of the ball screw, but also increases the cost of the ball 56 and makes it difficult to reduce the cost.

  The present invention has been made in view of these conventional problems. In a ball screw having a large diameter and a large number of balls, the ball screw has improved operability and improved operating efficiency, and a V-belt type non-rotating belt provided with the ball screw has been improved. An object of the present invention is to provide a pulley width drive mechanism for a step transmission.

  In order to achieve such an object, the invention according to claim 1 of the present invention includes a cylindrical nut having a spiral thread groove formed on the inner periphery thereof, and is inserted into the nut, and the thread groove is disposed on the outer periphery thereof. A screw shaft formed with a plurality of screw grooves having the same lead angle as the lead angle, and a plurality of balls accommodated in a freely rollable manner between the two screw grooves, and adjacent to each other in the axial direction of the screw shaft. A ball circulation groove having the plurality of screw grooves individually as closed loops is provided in the land portion existing between the matching screw grooves, and this ball circulation groove causes the ball downstream of the screw groove to sink into the inner diameter side. In the axial circulation type ball screw formed in a substantially S shape so as to get over the land portion of the nut and return to the upstream side, the calculated number of balls that can be arranged in one circuit of the thread groove of the screw shaft 10% to 20% of the ball is pulled out It is assembled in the state.

  In this way, in the axial circulation type ball screw, 10-20% of the balls are assembled with respect to the calculated number of balls that can be arranged in one circuit of the thread groove of the screw shaft. The competition between balls is eliminated, and a good operating state can be achieved without using space balls, smooth operation can be obtained, and damage due to contact between balls can be prevented. Therefore, it is possible to provide a ball screw with improved operability and improved operating efficiency.

  Further, as in the invention described in claim 2, if the thread groove of the screw shaft and the ball circulation groove are formed into a predetermined finished shape by cutting and a predetermined hardened layer is formed on the surface by heat treatment A desired screw groove shape and surface roughness can be ensured, and a ball screw with a short processing time and low cost can be provided.

  If the hardened layer is formed by quenching by high-frequency induction heating as in the invention described in claim 3, the grain boundary oxide layer can be suppressed on the surface layer, and the local layer can be heated and the hardened layer depth can be reduced. This can be easily set.

  In addition, as in the invention described in claim 4, if at least the thread groove is finished by shot peening after the heat treatment, the scale and surface grain boundary oxide layer adhering to the thread groove are removed. And the durability of the ball screw can be improved.

  According to a fifth aspect of the present invention, a hollow hole into which the main shaft of the pulley is inserted is formed in the screw shaft, and the screw shaft is supported so as to be movable in the rotational direction and the axial direction. The nut is supported in a fixed state in the axial direction and rotational direction, and is moved in the axial direction by rotationally driving the screw shaft, thereby moving the pulley. It is possible to provide a pulley width driving mechanism for a V-belt type continuously variable transmission in which the side flange is moved in the axial direction to change the pulley width and the belt winding diameter is changed.

  Preferably, as in the invention described in claim 6, if the inner diameter portion of the hollow hole is kept as the base material hardness, it is possible to improve durability while suppressing an increase in cost.

  A ball screw according to the present invention includes a cylindrical nut having a helical thread groove formed on the inner periphery, and a plurality of lead nuts inserted into the nut and having the same lead angle as the lead angle of the thread groove on the outer periphery. A screw shaft in which a screw groove is formed, and a large number of balls accommodated in a freely rolling manner between the two screw grooves, and a land portion existing between adjacent screw grooves in the axial direction of the screw shaft, A ball circulation groove is provided in which the plurality of screw grooves are individually closed loops. The ball circulation groove sinks the ball downstream of the screw groove to the inner diameter side and climbs over the land portion of the nut to the upstream side. In a shaft circulation type ball screw formed in a substantially S shape so as to return to the back, 10-20% of the ball is extracted with respect to the calculated number of balls that can be arranged in one circuit of the thread groove of the screw shaft. Because it is assembled in the state This eliminates the competition between the balls, makes it possible to operate smoothly without using a space ball, provides smooth operation, and prevents damage due to contact between the balls. With a large number of ball screws, it is possible to provide a ball screw with improved operability and improved operating efficiency.

  A cylindrical nut having a helical thread groove formed on the inner periphery, and a screw shaft that is inserted into the nut and has a plurality of thread grooves having the same lead angle as the lead angle of the thread groove on the outer periphery. And a plurality of balls accommodated in a rollable manner between the two screw grooves, and the plurality of screw grooves are individually formed in land portions existing between adjacent screw grooves in the axial direction of the screw shaft. A ball circulation groove is provided as a closed loop, and these ball circulation grooves meander the ball so as to sink the ball downstream of the screw groove to the inner diameter side, get over the land portion of the nut and return to the upstream side. In an S-shaped ball circulation type ball screw, the thread groove and ball circulation groove of the screw shaft are formed into a predetermined finished shape by cutting, and a predetermined hardened layer is formed on the surface by induction hardening As To ball number of computational that can be placed in one circuit of the screw groove of the serial screw shaft, it is assembled in a state withdrawn from 10 to 20 percent of the ball.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic longitudinal sectional view showing one embodiment of a ball screw according to the present invention, FIG. 2 is a schematic sectional view of a ball circulation path in which the ball of FIG. Is a plan view showing the screw shaft, (b) is a perspective view of the screw shaft, FIG. 4 is an explanatory diagram showing a machining state of the screw groove on the screw shaft, and FIG. 5 (a) is a circular arc shape on the screw shaft. FIG. 6B is an enlarged cross-sectional view of the thread groove, and FIG. 6A is an enlarged cross-sectional view of the screw groove having a Gothic arc shape on the screw shaft. (D) is an enlarged cross-sectional view showing the machining process of the same screw groove, FIG. 7 (a) is a schematic plan view when approximately 10% of the ball is extracted, (b) is a schematic front view, and FIG. ) Is a schematic plan view when approximately 20% of the ball is extracted, and (b) is a schematic front view.

  This ball screw 1 is used in a pulley width driving mechanism of a V-belt type continuously variable transmission. As shown in FIGS. 1 and 2, a cylindrical nut 2 and a screw shaft 3 inserted in the nut 2 are used. And a number of balls 4 accommodated between the screw shaft 3 and the nut 2 and a cage ring 5 for holding the balls 4 in a circumferentially equal distribution. The cage ring 5 is attached so as to be relatively stationary in the axial direction with respect to the screw shaft 3 and in a relatively rotatable state.

  The nut 2 is made of case-hardened steel such as SCM415 or SCM420, and a spiral thread groove 2a having a predetermined lead angle θ continuous between both ends is formed on the inner periphery thereof. Is mounted with a rolling bearing 10 comprising a deep groove ball bearing. On the other hand, the screw shaft 3 has a hollow structure having a hollow hole 3c, and a pulley main shaft (not shown) can be inserted into the hollow hole 3c. The screw shaft 3 is made of medium-carbon steel such as S55C or case-hardened steel such as SCM415, and is inserted into the nut 2 and is not continuous to the outer region in the axial direction on the outer periphery (a plurality of screw grooves 3a in this case) 3a, 3b is formed. The screw groove 2a of the nut 2 and the screw grooves 3a and 3b of the screw shaft 3 are set to the same lead angle θ. Then, the screw grooves 3a and 3b are hardened by quenching, which will be described later, and the inner diameter portion of the hollow hole 3c is kept at the base material hardness. Thereby, durability can be improved while suppressing an increase in cost.

  The thread grooves 2 a, 3 a, 3 b are formed in a Gothic arc shape in which two arcs having a curvature radius slightly larger than the radius of the ball 4 are combined. Of course, the thread grooves 2a, 3a, and 3b may have a circular arc shape that has a radius of curvature slightly larger than the radius of the ball 4 and makes an angular contact with the ball 4 in addition to the gothic arc shape.

  In the present embodiment, the plurality of screw grooves 3a and 3b are closed loops, and the balls 4 respectively accommodated in the plurality of screw grooves 3a and 3b are independently endlessly circulated. That is, as shown in FIGS. 3 (a) and 3 (b), a plurality of screw grooves 3a and 3b are individually provided in the land portion 6 existing between the screw grooves 3a and 3b adjacent in the axial direction of the screw shaft 3. Ball circulation grooves 7 and 8 are provided as closed loops.

  The ball circulation grooves 7 and 8 individually connect the upstream side and the downstream side of the thread grooves 3a and 3b. The ball circulation grooves 7 and 8 sink the ball 4 downstream of the thread grooves 3a and 3b to the inner diameter side. It is formed in a substantially S-shape meandering so as to get over the two land portions 9 and return to the upstream side. Therefore, the depth of the ball circulation grooves 7 and 8 is set to such a depth that the ball 4 can get over the land 9 of the screw groove 2a in the nut 2 in the ball circulation grooves 7 and 8 (see FIG. 2). The ball circulation grooves 7 and 8 are also cured in the same manner as the thread grooves 3a and 3b.

  FIG. 4 shows a processed state of the thread grooves 3 a and 3 b in the screw shaft 3. A hollow workpiece W (3) made of raw material is gripped by a main spindle chuck 11 of a lathe and turned by an end mill 12 while being synchronously rotated in a predetermined direction. The end mill 12 is supported so as to be movable back and forth in the radial direction and movable in the axial direction, and its position is determined by NC control. Turning of the thread grooves 3a and 3b is performed by so-called point cutting. That is, when the thread groove 3a (3b) has a Gothic arc shape as shown in FIG. 6A, the end mill 12 has a nose radius R2 smaller than the groove curvature radius R1 of the thread groove 3a. As shown in b) to (d), the end mill 12 is moved a plurality of times by the effective length of the thread groove 3a, and a plurality of tracks of the end mill 12 are overlapped to form the thread groove 3a having a predetermined shape.

  Here, by setting the nose radius R2 of the end mill 12 close to the groove curvature radius R1 of the screw groove 3a, the rough shape of the screw groove 3a can be obtained without moving the end mill 12 in the axial direction, and the machining time can be reduced. It can be shortened. When the thread groove 3a (3b) has a circular arc shape as shown in FIG. 5A, an end mill 12 having the same nose radius R4 as the groove curvature radius R3 of the thread groove 3a is used. As shown to b), you may make it shape | mold the thread groove 3a of a predetermined shape by sending this end mill 12 to radial direction.

  Moreover, in this embodiment, after completing the shaping | molding process of several screw groove 3a, 3b by point cutting, the hardened layer of the range of 55-62HRC is formed in the surface by heat processing. The heat treatment may be carburization quenching or quenching by high frequency induction heating, but it is preferable to use induction hardening that can suppress the grain boundary oxide layer on the surface layer and that can locally heat and set the hardened layer depth relatively easily. .

Further, finish processing (not shown) by shot peening is performed in order to remove scale and surface grain boundary oxide layers adhering to the screw grooves 3a, 3b, etc. by heat treatment. In this shot peening, the particle size of the steel beads was 20 to 100 μm, the injection time was about 90 seconds, the injection pressure was 1 to 3 kg / cm ² , and the distance between the injection nozzle and the surface of the workpiece was about 140 mm. Thereby, the durability of the ball screw 1 can be improved.

  In the pulley width drive mechanism of the V-belt type continuously variable transmission, the screw shaft 3 is rotationally moved and the nut 2 is prevented from rotating to obtain a linear motion of the screw shaft 3. For example, the screw shaft 3 is supported so as to be movable in the rotational direction and the axial direction, and is connected to a movable flange of a pulley (not shown) via a rolling bearing 10 (see FIG. 1). The nut 2 is supported in a fixed state in the axial direction and the rotational direction, and the screw shaft 3 is moved in the axial direction by rotating the screw shaft 3 via a drive transmission mechanism (not shown), thereby moving the pulley on the movable side. By moving the flange in the axial direction, the pulley width can be changed, and the winding diameter of the belt can be changed.

  Here, in this embodiment, the balls 4 are accommodated in a state where they are extracted at a predetermined ratio with respect to the calculated number of balls that can be arranged in one circuit of the ball screw 1. For example, in a ball screw in which the shaft diameter of the screw shaft 3 is φ63 mm, the lead is 3 mm, and the outer diameter of the ball 4 is φ2.778 mm, the calculated number of balls that can be arranged in one circuit of the screw groove 3a in the screw shaft 3 is 70. As shown in FIG. 7, when approximately 10% (seven) are extracted to 63 pieces, the clearance between the adjacent balls 4 increases, and approximately 25% of the balls 4 out of all the balls 4. Becomes non-contact. Furthermore, when the calculated number of balls that can be arranged in one circuit is 70, as shown in FIG. 8, when approximately 21% (15) is extracted and 55, it is approximately 50% of all balls 4. The ball 4 becomes non-contact. Thereby, the competition between the balls 4 is eliminated, a good operating state can be obtained without using a space ball, a smooth operation can be obtained, and damage due to contact between the balls 4 can be prevented. That is, in this type of ball screw having a large diameter and a large number of balls, it is possible to provide a ball screw with improved operability and improved operating efficiency.

  In addition, when the ratio of the balls 4 to be extracted is less than 10% with respect to the calculated number of balls that can be arranged in one circuit of the thread groove 3a in the screw shaft 3, a remarkable effect cannot be obtained, and when it exceeds 20%. Since the area where the balls 4 do not exist increases, the load balance decreases and the surface pressure partially increases, the extraction ratio is preferably in the range of 10 to 20%.

  The embodiment of the present invention has been described above, but the present invention is not limited to such an embodiment, and is merely an example, and various modifications can be made without departing from the scope of the present invention. Of course, the scope of the present invention is indicated by the description of the scope of claims, and further, the equivalent meanings described in the scope of claims and all modifications within the scope of the scope of the present invention are included. Including.

  The ball screw according to the present invention can be applied to a ball screw used in a pulley width driving mechanism of a V-belt type continuously variable transmission such as an automobile.

It is a schematic longitudinal cross-sectional view which shows one Embodiment of the ball screw which concerns on this invention. FIG. 2 is a schematic cross-sectional view of a ball circulation path in which the ball of FIG. (A) is a top view which shows a screw axis | shaft. (B) is a perspective view same as the above. It is explanatory drawing which shows the processing state of the thread groove in a screw shaft. (A) is an expanded sectional view of the thread groove which consists of the circular arc shape in a screw shaft. (B) is an expanded sectional view which shows the manufacturing process of a screw groove same as the above. (A) is an expanded sectional view of the thread groove which consists of a Gothic arc shape in a screw axis. (B)-(d) is an expanded sectional view which shows the manufacturing process of a screw groove same as the above. (A) is a schematic top view at the time of extracting about 10% of a ball | bowl. (B) is a schematic front view. (A) is a schematic top view at the time of extracting about 20% of a ball | bowl. (B) is a schematic front view. (A) is a longitudinal cross-sectional view which shows the conventional ball screw. (B)-(d) is a typical partial expanded sectional view same as the above. It is a longitudinal cross-sectional view which shows the other conventional ball screw.

Explanation of symbols

1 ... Ball screw 2 ... Nut 2a, 3a, 3b・ ・ ・ ・ ・ ・ ・ ・ Thread groove 3 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Screw shaft 3c ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・... Hollow hole 4 ... Ball 5 ... ... Retainer rings 6, 9 ... Land parts 7, 8 ... Ball circulation groove 10 ... Rolling bearing 11 ... Spindle chuck 12 ...・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ End Mill 50, 55 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Screw Shaft 50a, 5 a, 54a, 55a, 55b ··· Thread grooves 51, 54 ···································· Ball 53 ... Ball screw 57, 60 ... Screw thread 58, 59 ...・ ・ ・ ・ ・ ・ ・ ・ Ball circulation grooves R1, R3 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Thread radius of curvature R2, R4 ・ ・ ・ ・ ・ ・ ・············ End mill nose radius θ

Claims (6)

A cylindrical nut having a helical thread groove formed on the inner periphery;
A screw shaft that is inserted into the nut and has a plurality of screw grooves formed on the outer periphery with the same lead angle as the lead angle of the screw groove;
A plurality of balls accommodated in a freely rollable manner between the both screw grooves,
A ball circulation groove having the plurality of screw grooves individually as closed loops is provided in a land portion existing between adjacent screw grooves in the axial direction of the screw shaft, and the ball circulation groove is disposed downstream of the screw groove. In the axial circulation type ball screw formed in a substantially S shape so as to sink the ball to the inner diameter side, get over the land portion of the nut and return to the upstream side,
A ball screw characterized by being assembled in a state where 10 to 20% of balls are extracted with respect to a calculated number of balls that can be arranged in one circuit of a screw groove of the screw shaft.   The ball screw according to claim 1, wherein the screw groove and the ball circulation groove of the screw shaft are formed into a predetermined finished shape by cutting, and a predetermined hardened layer is formed on the surface thereof by heat treatment.   The ball screw according to claim 2, wherein the hardened layer is formed by quenching by high frequency induction heating.   The ball screw according to claim 2 or 3, wherein at least the thread groove is subjected to finish processing by shot peening after the heat treatment.   A hollow hole through which the main shaft of the pulley is inserted is formed in the screw shaft, the screw shaft is supported so as to be movable in the rotational direction and the axial direction, and is connected to the movable flange of the pulley via a rolling bearing, The nut is supported in a fixed state in the axial direction and the rotational direction, and the screw shaft is rotated to move in the axial direction, and the movable side flange of the pulley is moved in the axial direction to change the width of the pulley. A pulley width driving mechanism for a V-belt continuously variable transmission, characterized in that the belt winding diameter is changed.   The pulley width drive mechanism of the V-belt type continuously variable transmission according to claim 5, wherein an inner diameter portion of the hollow hole is left with a base material hardness.

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