JP2011163517A - Power transmission mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power transmission mechanism which smoothly linearly moves a driven cylindrical member along the longitudinal direction of a drive guide member by surely rolling a ball in a simple ball retention form without using a screw shaft. <P>SOLUTION: The power transmission mechanism 100 includes the drive guide member 110 including a cylindrical coil body 112, and the driven cylindrical member 120 fitted onto the outer periphery of the drive guide member 110 in a state where a ball group 130 consisting of four balls 131 supported in a rolling manner between coil pitches CP of a coil wire 112a constituting the cylindrical coil body 112 is interposed. The ball group 130 is positioned doubly at equal intervals on the circumference of the driven cylindrical member 120 on one end side of the driven cylindrical member 120. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention is a power transmission mechanism that converts a rotational movement of a drive guide member into a linear movement of a driven cylindrical member along the longitudinal direction of the drive guide member. Is used for a linear actuator that operates the driven cylindrical member so as to freely advance and retract by converting the linear movement of the driven cylindrical member.

  As a power transmission mechanism used in a conventional linear actuator, a screw shaft having a plurality of spiral ball rolling grooves formed on the outer peripheral surface and an annular convex portion on the inner peripheral surface and both axial sides of the annular convex portion A nut having a substantially one-quarter circular ball rolling groove formed so as to face the spiral ball rolling groove, and a space between the spiral ball rolling groove and the annular ball rolling groove. There is known a ball non-circular ball screw having a mounted ball and a cage held in a nut on both sides of an annular convex portion to hold the ball so as to roll (for example, , See Patent Document 1).

JP-A-7-77260 (Claims, FIG. 1)

  A conventional power transmission mechanism composed of a non-circulating ball screw requires a screw shaft with a multi-threaded spiral ball rolling groove that fits with a large number of balls. It is necessary to form a multi-spindle spiral ball rolling groove that is completely different from the thread groove, and high machining accuracy is required to precisely form such a multi-spindle spiral ball rolling groove. There is a problem that a great processing load is imposed on the production of the screw shaft.

  Further, in a conventional power transmission mechanism composed of a ball non-circulating ball screw, it is adapted to fit to a nut for holding a large number of balls in a freely rolling manner so as to face the spiral ball rolling groove of the screw shaft described above. An annular ball rolling groove must be formed, and there is a problem that a high machining accuracy is required for the rolling groove, and a great machining burden is imposed on the production of the nut. A large number of balls are sealed and held by attaching rings, cages, etc. from the nut fitting direction, that is, the axial direction of the screw shaft, but the rolling state of each ball cannot be adjusted individually. However, there is a problem that an unbalanced load is generated in a specific ball, causing early wear of the ball, or excessively worn nuts and screw shafts to hinder power transmission by rolling the ball.

  Therefore, the present invention solves the conventional problems, that is, the object of the present invention is to drive the driven cylindrical member by reliably rolling the ball in a simple ball holding form without using a screw shaft. It is to provide a power transmission mechanism for smoothly linearly moving along a longitudinal direction of a guide member.

  According to a first aspect of the present invention, there is provided a drive guide member comprising at least a cylindrical coil body, and a ball group that rolls between coil pitches of coil wires constituting the cylindrical coil body on an outer peripheral surface of the drive guide member. A driven cylinder member inserted and inserted in an interposed state, and a power transmission mechanism for converting the rotational movement of the drive guide member into linear movement of the driven cylinder member along the longitudinal direction of the drive guide member, The balls are positioned and arranged at equal intervals in at least two places on the circumference of the driven cylindrical member on at least one end side of the driven cylindrical member, thereby solving the above-described problem.

  According to a second aspect of the present invention, in addition to the configuration of the first aspect, the ball group includes four balls that roll while pinching one of the coil wires at four points. As a result, the above-described problems are solved.

  According to a third aspect of the present invention, in addition to the structure according to the first aspect, the ball group rolls four balls while sandwiching two adjacent strips of the coil wire at three points. By solving this problem, the above-mentioned problems are solved.

  According to a fourth aspect of the present invention, in addition to the configuration according to any one of the first to third aspects, the ball diameter of the ball is a wire of a coil wire constituting the cylindrical coil body. By setting the diameter approximately equal to the diameter, the above-described problem is solved.

  Therefore, the power transmission mechanism of the present invention according to claim 1 is provided between a drive guide member comprising at least a cylindrical coil body and a coil pitch of a coil wire constituting the cylindrical coil body on the outer peripheral surface of the drive guide member. By including a driven cylindrical member inserted with a rolling ball group interposed, the ball group reliably rolls in a simple ball holding configuration without using a conventional screw shaft. Therefore, the driven cylindrical member can be linearly moved along the longitudinal direction of the drive guide member.

  A group of balls that roll between the coil pitches of the coil wires constituting the cylindrical coil body are positioned and arranged at equal intervals at least at two locations on the circumference of the driven cylindrical member on at least one end side of the driven cylindrical member. As a result, these ball groups roll to complement each other at least in the radial direction of the driven cylindrical member generated with respect to the driving guide member, so that the driven cylindrical member is driven and guided with a minimum arrangement of the ball group. It is possible to stably and smoothly linearly move along the longitudinal direction of the member, and to significantly reduce the power burden for moving the driven cylindrical member.

Here, when the above-described cylindrical coil body is fixed to the drive shaft over the entire length, the coil pitch is fixed and secured over the entire length of the cylindrical coil body. Can be stably moved at a constant speed along the longitudinal direction of the drive guide member along the longitudinal direction of the drive guide member.
Further, in the case where only both ends of the cylindrical coil body are fixed to the drive shaft, even if some impact is applied to the drive guide member or the driven cylindrical member when the driven cylindrical member moves along the drive guide member, the cylinder The impact is absorbed by elastic deformation between the coil pitches in the coil body, and the driven cylindrical member can be moved linearly and smoothly along the longitudinal direction of the drive guide member.

  According to the power transmission mechanism of the present invention according to claim 2, in addition to the effect exerted by the power transmission mechanism according to claim 1, the ball group includes four coil wires arranged in a staggered manner. Since it is composed of four balls that roll while pinching, a single coil wire is securely clamped alternately at two points on the upper and lower sides. The driven cylindrical member can be surely and smoothly linearly moved along the longitudinal direction of the drive guide member by stabilizing the engagement.

  Furthermore, according to the power transmission mechanism of the present invention according to claim 3, in addition to the effect exerted by the power transmission mechanism according to claim 1, the ball group includes three adjacent two strips of the coil wire. Since it is composed of four balls that roll while being pinched at a point, the power burden for moving the driven cylindrical member is divided into two divided coil wires adjacent to each other. The engagement between the ball and the coil wire can be stabilized with a small number of balls, and the driven cylindrical member can be linearly moved more smoothly along the longitudinal direction of the drive guide member.

  According to the power transmission mechanism of the present invention according to claim 4, in addition to the effect exhibited by the power transmission mechanism according to any one of claims 1 to 3, the ball diameter of the ball is cylindrical. Since the generated stress of the ball is reduced by being substantially equal to the diameter of the coil wire constituting the coil body, the ball wear is suppressed and the driven cylindrical member is moved along the longitudinal direction of the drive guide member. Smooth linear movement over a long period of time.

1 is an overall schematic diagram of a power transmission mechanism according to a first embodiment of the present invention. The assembly exploded view of the drive guide member and driven cylindrical member of FIG. Sectional drawing seen from the X1-X1 line direction of FIG. Explanatory drawing of the ball | bowl holding mechanism which hold | maintains a ball | bowl to the driven cylindrical member shown in FIG. Explanatory drawing which expanded the ball group used in 1st Example of this invention. The schematic diagram of the linear actuator using the power transmission mechanism of the present invention. The figure which shows the state which the linear actuator of FIG. 6 extended | stretched. The whole schematic diagram of the power transmission mechanism which is the 2nd example of the present invention. Sectional drawing seen from the X2-X2 line direction of FIG. Explanatory drawing which expanded the ball group used in 3rd Example of this invention.

  The power transmission mechanism of the present invention includes a drive guide member composed of at least a cylindrical coil body, and a ball group that rolls between the coil pitches of the coil wires constituting the cylindrical coil body on the outer peripheral surface of the drive guide member. And a driven cylindrical member that is inserted in a state in which the driven guide member is inserted, thereby converting the rotational movement of the drive guide member into linear movement of the driven cylindrical member along the longitudinal direction of the drive guide member, and a cylindrical coil body. A group of balls composed of a large number of balls supported so as to be able to roll between the coil pitches of the coil wires constituting the at least one end of the driven cylindrical member at equal intervals in at least two places on the circumference of the driven cylindrical member. Positioned and arranged, the driven cylindrical member smoothly moves linearly along the longitudinal direction of the drive guide member with a small number of balls, and the power burden for moving the driven cylindrical member is significant. As long as it Ku reduced, the form of the specific implementation, may any be any one.

  For example, the specific form of the drive guide member used in the power transmission mechanism of the present invention may be at least composed of a cylindrical coil body, for example, composed of only a cylindrical coil body, or a cylindrical coil. The body can be closely fitted to a drive shaft having a circular cross section and at least both ends of the cylindrical coil body can be fixed. However, in the former case, the number of parts of the drive guide member can be reduced. The cost can be kept low, and in the latter case, the buckling of the cylindrical coil body can be regulated by the drive shaft.

  And as for the specific material of the cylindrical coil body used for the drive guide member, either a metal wire such as a highly rigid coil spring or a plastic wire made of engineering plastic may be used. Since a commercially available spring steel material can be used as it is, stable rolling of the ball can be easily obtained. In the latter case, the ball exhibits self-lubricating properties without using lubricating oil. Rolling smoothly, the rotational movement of the drive guide member can be converted to the linear movement of the driven cylindrical member without any resistance.

  As for the cross-sectional form of the coil wire constituting the cylindrical coil body, a circular cross-section can be used as long as the ball spherical surface and the coil surface of the coil wire are in point contact between the coil pitches to make the ball rollable. It is possible to use any of the above-mentioned ones or those having an elliptical cross section.

About the specific arrangement form of the ball group in the power transmission mechanism of the present invention, it is sufficient that the ball group is positioned and arranged at equal intervals in at least two places on the circumference of the driven cylindrical member on at least one end side of the driven cylindrical member. There may be no problem even if they are arranged at two equal intervals with a 180 ° interval on the circumference of the driven cylindrical member, or even at 120 ° intervals and at three equal intervals.
In addition, the ball group may be arranged in either one or both of the upper end region and the lower end region of the driven cylindrical member, but if it is arranged in the former one, the number of parts of the driven cylindrical member The manufacturing cost can be reduced at a low cost, and the driven cylindrical member can be linearly moved more stably and smoothly along the longitudinal direction of the drive guide member if both of the latter are arranged. The power burden for moving the cylindrical member can be significantly reduced.

Hereinafter, a power transmission mechanism according to an embodiment of the present invention will be described with reference to the drawings.
Here, FIG. 1 is an overall schematic diagram of a power transmission mechanism according to an embodiment of the present invention, FIG. 2 is an exploded view of the drive guide member and the driven cylindrical member of FIG. 1, and FIG. FIG. 4 is a cross-sectional view as viewed from the X1-X1 line direction of FIG. 1, FIG. 4 is an explanatory view of a ball holding mechanism for holding the ball on the driven cylindrical member shown in FIG. 1, and FIG. It is explanatory drawing which expanded the ball group used in 1 Example, FIG. 6 is a schematic diagram of the linear actuator using the power transmission mechanism of this invention, FIG. 7 is expansion | extension of the linear actuator of FIG. FIG. 8 is an overall schematic diagram of the power transmission mechanism according to the second embodiment of the present invention, and FIG. 9 is a cross-sectional view as seen from the X2-X2 line direction of FIG. FIG. 10 is an enlarged view of the ball group used in the third embodiment of the present invention.

First, as shown in FIGS. 1 and 2, a power transmission mechanism 100 according to a first embodiment of the present invention is a cylinder made of a highly rigid spring steel material tightly fitted to a columnar drive shaft 111 having a circular cross section. A drive guide member 110 having both ends of the shaped coil body 112 fixed is provided, and the outer periphery of the drive guide member 110 can freely roll between the coil pitches CP of the coil wires 112a constituting the cylindrical coil body 112. A driven cylindrical member 120 is provided which is inserted and inserted in a state where two sets of ball groups 130, 130 composed of four balls 131 supported on each other are interposed.
As a result, a commercially available spring steel material can be used as it is as the cylindrical coil body 112 of the drive guide member 110, and the drive guide member 110 is moved when the driven cylindrical member 120 moves along the drive guide member 110. Alternatively, even if some impact is applied to the driven cylindrical member 120, the impact is absorbed by elastic deformation between the coil pitches CP in the cylindrical coil body 112, and the driven cylindrical member 120 is made elastic and smooth along the longitudinal direction of the drive guide member 110. It is designed to move in a straight line.

  Reference numeral 113 shown in FIG. 1 is a flange member that is fixedly provided on the protruding tip end side of the drive shaft 111 and prevents the driven cylindrical member 120 from coming off from the drive guide member 110. Reference numeral 114 is the drive shaft 111. This is a shaft-side gear that is fixed to the base end side of the shaft and transmitted from a drive source (not shown).

Then, as shown in FIG. 3, in the upper end region of the driven cylindrical member 120 described above, the ball groups 130 and 130 are positioned and arranged at equal intervals at two places shifted by 180 ° phase.
As a result, these ball groups 130 and 130 roll to complement each other in the radial load of the driven cylindrical member 120 generated on the drive guide member 110.
In the first embodiment, the ball groups 130 are arranged at two equal intervals. However, as a modification of the first embodiment, the ball groups 130 may be arranged at three equal intervals with a 120 ° phase shift. There is no problem.

The above-described ball groups 130 and 130 disposed above are supported between the coil pitches CP of the coil wires 112a constituting the cylindrical coil body 112, as shown in FIG.
Thereby, since the spherical surface of the ball 131 and the coil surface of the coil wire 112a are in a point contact state between the coil pitches CP, the mutual contact area is minimized, the contact resistance is eliminated, and the ball 131 rolls. It is free.

Further, as shown in FIG. 5, four balls 131 that roll while pinching one line of the coil wire 112a at four points are arranged in these ball groups 130 and 130, respectively.
As a result, the single coil wire 112a is securely clamped alternately at the two upper and lower points, so that the engagement between the ball 131 and the coil wire 112a is stabilized with a smaller number of balls.

As shown in FIG. 4, the driven cylindrical member 120 described above has a cylindrical sleeve 121 provided with ball holding holes 121 a each positioned corresponding to the ball 131, and the ball 131 directed toward the cylindrical coil body 112. And a ball sealing spring 124 for positioning and sealing the ball pressing spring 123 in the ball holding hole 121a.
As a result, the ball 131 is pressed against the coil wire 112a.

Furthermore, the ball diameter of the ball 131 is substantially equal to the wire diameter of the coil wire 112a constituting the cylindrical coil body 112, as shown in FIG.
As a result, the stress applied to each ball 131 is reduced, the wear of the ball 131 is suppressed, and the driven cylindrical member 120 is smoothly linearly moved along the longitudinal direction of the drive guide member 110 over a long period of time. It is supposed to let you.

  In the power transmission mechanism 100 according to the first embodiment of the present invention obtained as described above, the ball groups 130 and 130 that roll between the coil pitches CP of the coil wire 112a constituting the cylindrical coil body 112 are driven. Since one end side of the cylindrical member 120 is positioned at two positions on the circumference of the driven cylindrical member 120 at equal intervals, the ball group can be reliably secured with a simple ball holding configuration without using a conventional screw shaft. In addition to rolling the ball group 130, 130, the ball group 130, 130 rolls complementing each other at least in the radial direction of the driven cylindrical member 120 generated on the drive guide member 110. Whether the driven cylindrical member 120 is stable along the longitudinal direction of the drive guide member 110 by stabilizing the engagement between the ball 131 and the coil wire 112a with the minimum arrangement of 130. Smoothly it can significantly reduce the power load for moving the follower cylindrical member 120 as well as being able to move linearly.

  In the ball groups 130 and 130, four balls 131 that roll while pinching one row of the coil wire 112a at four points are arranged, so that one coil wire 112a moves up and down. Since it is securely clamped alternately at two points, the engagement between the ball 131 and the coil wire 112a is stabilized with a smaller number of balls, and the driven cylindrical member 120 is straightened more smoothly along the longitudinal direction of the drive guide member 110. The effect is enormous, such as being able to move.

Next, a linear actuator SAM using the power transmission mechanism 100 of the present invention will be described below with reference to FIGS.
That is, in the linear actuator SAM using the power transmission mechanism 100 of the present invention, the power transmission described above is applied to the rotational force of the drive gear DG attached to the rotation shaft of the electric motor M constituting the drive source via the intermediate gear MG. Power is transmitted to a shaft side gear 114 fixed to the base end side of the drive shaft 111 constituting a part of the mechanism 100, and then to the drive guide member 110 of the power transmission mechanism 100 that is pivotally attached to the shaft side gear 114. The rotational force transmitted by the power is converted into a linear movement of the driven cylindrical member 120 via a large number of balls 131, and at the same time, it is converted into a linear advance / retreat operation of the piston P fixed to the driven cylindrical member 120.
6 to 7 accommodates the drive gear DG, the intermediate gear MG, the shaft side gear 114, and the power transmission mechanism 100 described above, and allows the piston P described above to advance and retract freely. It is a housing.

  Therefore, the linear actuator SAM as described above uses the power transmission mechanism 100 of the present invention, so that a total of eight balls can be reliably secured in a simple ball holding configuration without using a conventional screw shaft. In order to roll, the rotational movement of the drive guide member 110 rotated by using the drive source M is converted into a linear movement of the driven cylindrical member 120 along the longitudinal direction of the drive guide member 110, and is fixed to the driven cylindrical member 120. The piston P can be moved linearly along the longitudinal direction of the housing H reliably, smoothly and stably.

  Further, the ball groups 130 and 130 composed of the four balls 131 are positioned and arranged at equal intervals at two locations on the circumference of the driven cylindrical member 120 on one end side of the driven cylindrical member 120, thereby reducing the number of balls. Since the engagement between the ball 131 and the coil wire 112a can be stabilized by the number of balls and the driven cylindrical member 120 can be smoothly linearly moved along the longitudinal direction of the drive guide member 110, the piston fixed to the driven cylindrical member 120 can be obtained. The effect is enormous, for example, the power load for moving P along the longitudinal direction of the housing H can be remarkably reduced.

Next, a power transmission mechanism 200 according to a second embodiment of the present invention will be described with reference to FIG.
Here, the basic configuration excluding the specific configuration of the ball groups 230A, 230A, 230B, and 230B in the power transmission mechanism 200 according to the second embodiment is completely the same as that of the power transmission mechanism 100 according to the first embodiment described above. Since they are the same, description of the power transmission mechanism 100 according to the first embodiment will be omitted by replacing the reference numerals of the 100s attached to the respective members with the reference numerals of the 200s.

Therefore, a specific configuration of the ball group 230A, 230A, 230B, 230B, which is the most characteristic feature of the power transmission mechanism 200 of the second embodiment, will be described in detail with reference to FIG.
First, as shown in FIGS. 8 to 9, the ball groups 230A and 230A are positioned and arranged at two positions with a 180 ° phase shift in the upper end region which is one end side of the driven cylindrical member 220 described above. The ball groups 230B and 230B are positioned and arranged at two positions with a 180 ° phase shift in the lower end region which is the other end side of the driven cylindrical member 220. The ball groups 230A and 230A and the two ball groups 230B and 230B arranged in the lower end region of the driven cylindrical member 220 are arranged 90 ° out of phase with each other.
That is, when viewed from the cylindrical cross section of the driven cylindrical member 220, the ball groups 230B and 230B arranged on the other end side of the driven cylindrical member 220 are positioned in the middle of the interval between the ball groups 230A and 230A arranged on the one end side. Has been placed.
As a result, these ball groups 230A, 230A, 230B, and 230B roll while complementing the thrust and radial loads of the driven cylindrical member 220 generated on the drive guide member 210. Yes.

  The power transmission mechanism 200 according to the second embodiment of the present invention obtained as described above is a group of balls 230A, 230A, 230B that roll between the coil pitches CP of the coil wire 212a constituting the cylindrical coil body 212. , 230B are positioned and arranged at two equal intervals on the circumference of the driven cylindrical member 220 on both the one end side and the other end side of the driven cylindrical member 220 without using a conventional screw shaft. Not only does the ball group 230A, 230A, 230B, 230B roll with a simple ball holding configuration, but the ball group 230A, 230A, 230B, 230B is generated by the driven cylindrical member 220 with respect to the drive guide member 210. The balls 230A, 230A, 230B, 2B, 2B, 2B, 2C, 2B The driven cylindrical member 220 can be stably and smoothly linearly moved along the longitudinal direction of the drive guide member 210 by stabilizing the engagement between the ball 231 and the coil wire 212a with the minimum arrangement of 0B and the driven cylindrical member. The power burden for moving 220 can be significantly reduced.

  In these ball groups 230A, 230A, 230B, and 230B, four balls 231 that roll while pinching one row of the coil wire 212a at four points are arranged. Since the coil wire 212a is securely held alternately at the two upper and lower points, the engagement between the ball 231 and the coil wire 212a is stabilized with a smaller number of balls, and the driven cylindrical member 220 is moved along the longitudinal direction of the drive guide member 210. The effect is enormous, for example, the linear movement can be performed more smoothly.

Next, a power transmission mechanism 300 according to a third embodiment of the present invention will be described with reference to FIG.
Here, the basic configuration except for the specific configuration of the ball groups 330 and 330 in the power transmission mechanism 300 according to the third embodiment is exactly the same as that of the power transmission mechanism 100 according to the first embodiment described above. The description of the power transmission mechanism 100 according to the first embodiment will be omitted by replacing the reference numerals of the 100 series attached to the respective members with the reference numerals of the 300 series.

Therefore, a specific configuration of the ball groups 330 and 330 that are most characteristic of the power transmission mechanism 300 of the third embodiment will be described in detail with reference to FIG.
That is, each of the ball groups 330 and 330 in the power transmission mechanism 300 of the third embodiment is composed of four balls 331 that roll while holding two adjacent strips of the coil wire at three points. .
As a result, the power load for moving the driven cylindrical member 320 is divided into two parts on the adjacent two coil wires 312a and dispersed, so that the balls 331 and the coil wires 312a can be engaged with each other with a smaller number of balls. Is to stabilize.

  In the power transmission mechanism 300 according to the third embodiment of the present invention obtained as described above, the ball groups 330 and 330 that roll between the coil pitches CP of the coil wire 312a constituting the cylindrical coil body 312 are driven. Since one end side of the cylindrical member 320 is positioned and arranged at two equal intervals on the circumference of the driven cylindrical member 320, the ball group can be reliably secured with a simple ball holding configuration without using a conventional screw shaft. In addition to rolling the ball group 330, 330, the ball group 330, 330 rolls mutually complementing at least the radial load of the driven cylindrical member 320 generated on the drive guide member 310. Whether the driven cylindrical member 320 is stable along the longitudinal direction of the drive guide member 310 by stabilizing the engagement between the ball 331 and the coil wire 312a with the minimum arrangement of 330. Smoothly it can significantly reduce the power load for moving the follower cylindrical member 320 as well as being able to move linearly.

  The ball groups 330 and 330 are composed of four balls 331 that roll while holding two adjacent strips of the coil wire 312a at three points, thereby moving the driven cylindrical member 320. Since the power load to be distributed is divided into two on the adjacent two coil wires 312a, the engagement between the balls 331 and the coil wires 312a is stabilized and the driven cylindrical member 320 is driven with a smaller number of balls. The effect is enormous, for example, the linear movement can be performed more smoothly along the longitudinal direction of the guide member 310.

  The power transmission mechanisms 100, 200, and 300 according to the first to third embodiments of the present invention can be used as a linear actuator SAM for converting the rotational force of the electric motor M into a linear advance / retreat operation. .

100, 200, 300 ... power transmission mechanism 110, 210, 310 ... drive guide members 111, 211, 311 ... drive shafts 112, 212, 312 ... cylindrical coil bodies 112a, 212a, 312a .. Coil wires 113, 213, 313 ... Flange members 114, 214, 314 ... Shaft side gears 120, 220, 320 ... Driven cylindrical members 121, 221, 321 ... Cylindrical sleeves 121a, 221a, 321a: Ball holding holes 122, 222, 322 ... Ball pressing plates 123, 223, 323 ... Ball pressing springs 124, 224, 324 ... Ball sealing plates 130, 230, 330 ... Ball group 230A: Ball group in upper region 230B: Lower region Lumpur group 131, 231, 331 ... Ball SAM ... linear actuator motor CP ... coil pitch M ... motor (drive source)
DG ... Drive gear MG ... Intermediate gear H ... Housing P ... Piston

Claims (4)

A drive guide member made of at least a cylindrical coil body, and a ball group that rolls between coil pitches of coil wires constituting the cylindrical coil body are inserted and inserted into the outer peripheral surface of the drive guide member. A power transmission mechanism that converts a rotational movement of the drive guide member into a linear movement of the driven cylinder member along the longitudinal direction of the drive guide member,
The power transmission mechanism according to claim 1, wherein the ball group is positioned and arranged at at least two locations on the circumference of the driven cylindrical member on at least one end side of the driven cylindrical member.   2. The power transmission mechanism according to claim 1, wherein the ball group includes four balls that roll while pinching one of the coil wires at four points in a zigzag manner.   2. The power transmission mechanism according to claim 1, wherein the ball group includes four balls that roll while sandwiching two adjacent strips of the coil wire at three points. 3.   4. The power according to claim 1, wherein a ball diameter of the ball is set to be approximately equal to a diameter of a coil wire constituting the cylindrical coil body. Transmission mechanism.

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