JP2005054860A - Worm gear device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a worm gear device capable of restricting a surface of a pitch circle of a worm wheel and quantity of rattle of a worm in the vertical direction to automatically eliminate backlash between them. <P>SOLUTION: This worm gear device 1 has the worm wheel 3 rotatably supported by a support base 2 through a first bearing, a worm supportable holder 5 having a second bearing for rotatably supporting the worm 4 to be engaged with the worm wheel 3 and fitted to the support base 2 through a third bearing to swing, and a coil spring 58 for pushing the worm 4 to the worm wheel 3. Each of the bearings are arranged to eliminate looseness in the thrust direction, and the second bearing is arranged so that the center axis of rotation thereof passes through a pitch point 63 of the worm wheel 3 and the worm 4 and becomes in parallel with a tangent 64 of the pitch circle 14 of the worm wheel 3, and the third bearing is arranged so that the center axis 36 of rotation thereof is separated from a surface, wherein the pitch circle 14 passes, in a direction of a parallel line 65 in parallel with the center axis 16 of rotation of the worm wheel 3 and becomes in parallel with the tangent 64. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a worm gear device that can automatically remove backlash between a worm and a worm wheel.

A conventional worm gear device has a worm wheel, a worm meshing with the worm wheel, a machine base, and a machine base by a trunnion provided at one end so as to rotatably support the worm and to change the assembly distance of the worm wheel and the worm. A worm housing that is swingably attached to the worm wheel, a worm pressure spring that is attached between the other end of the worm housing and the machine base so as to press the worm against the worm wheel, and an excessive retreat of the worm housing against the worm housing. The worm retraction stopper that restricts the worm, the worm is pressed against the worm wheel by a spring to eliminate backlash between them, and the worm gear is excessively retracted from the worm wheel, and the retraction stopper is used for the worm housing. The grayed so that constrained in contact (for example, see Patent Document 1).
JP-A-7-96441 (page 3, FIG. 1)

  However, since the conventional worm gear device has a cantilever support structure in which the worm housing is swingably supported on the machine base only by the trunnion provided at one end thereof, the worm backlash caused by the support of the worm housing. The amount tends to be larger in the direction of the central axis of rotation of the worm wheel that is perpendicular to the surface direction of the pitch circle of the worm wheel, and as a result, the pitch circle of the worm wheel is engaged with the engagement of the worm wheel and the worm. There was a problem that a large amount of backlash occurred in the direction perpendicular to the surface, and the backlash between them could not be removed successfully.

  The present invention has been made to solve the conventional problems, and in automatically removing the backlash between the worm wheel and the worm, the backlash amount of the worm is determined only by the surface direction of the pitch circle of the worm wheel. An object of the present invention is to provide a worm gear device that can be suppressed to be smaller in the direction of the rotation center axis of the worm wheel that is perpendicular to the surface.

  A worm gear device according to the present invention includes a support base, a worm wheel having a pitch circle, a first shaft extending in a direction perpendicular to the pitch circle is rotatably supported by the support base via a first bearing, and a worm wheel The worm meshes with the worm and the first bearing has a second bearing that rotatably supports the worm from both ends, and the other end swings from the both ends to the support base via the third bearing. A worm support movable holder attached to the worm support movable member, and an elastic pressing member provided between the worm support movable holder and the support base for pressing the worm against the worm wheel, the first bearing, the second bearing, The three bearings are loosely packed in the thrust direction, and the second bearing has its center axis of rotation passing through the pitch points of the worm wheel and worm. The third bearing has a position where the rotation center axis is parallel to the tangent and spaced from the surface where the pitch circle exists in the direction of the rotation center axis of the worm wheel. It has the structure arrange | positioned so that it may pass.

  With this configuration, the backlash amount of the worm is suppressed not only in the surface direction of the pitch circle of the worm wheel but also in the direction of the central axis of rotation of the worm wheel that is perpendicular to the surface of the worm wheel. A worm gear device capable of automatically removing backlash can be provided.

  In the worm gear device of the present invention, the third bearing passes through the pitch point or the vicinity of the pitch point in parallel to the rotation center axis of the worm wheel from the plane where the rotation center axis is parallel to the tangent and the pitch circle exists. It has the structure arrange | positioned so that it may pass through the position spaced apart in the direction of the parallel line.

  With this configuration, the distance between the rotation center axis of the second bearing and the rotation center axis of the third bearing can be shortened as compared with the case where the parallel line does not pass through the pitch point or the vicinity of the pitch point. It becomes possible to make it compact.

  Furthermore, the worm gear device of the present invention has a configuration including an elastic preloading member that preloads the worm with an elastic force from one of the second bearings toward the other of the second bearings. .

  With this configuration, even when an excessive thrust force is applied to the worm, the elastic preload member can be bent to move the worm in the thrust direction, i.e., the axial direction of the worm, so that the worm wheel and worm can escape. It is possible to prevent problems such as biting and overload on the electric motor.

  According to the present invention, the first bearing that supports the worm wheel on the support base, the second bearing that supports the worm on the worm support movable holder, and the third bearing that supports the worm support movable holder on the support base are loosely packed in the thrust direction. And the second bearing is arranged so that the rotation center axis is parallel to a tangent line passing through the pitch point of the worm wheel and the worm and tangent to the pitch circle of the worm wheel, and the third bearing is By arranging it so that it passes through a position parallel to the tangent line and spaced away from the surface where the pitch circle exists in the direction of the central axis of rotation of the worm wheel, the amount of worm play is not limited to the surface direction of the pitch circle of the worm wheel. The bar between the worm wheel and the worm is suppressed so that it also becomes smaller in the direction of the rotation center axis of the worm wheel perpendicular to this surface. It is possible to provide a worm gear device has the effect of crash can be automatically removed.

  Hereinafter, a worm gear device according to an embodiment of the present invention will be described with reference to the drawings.

  1 and 2 show an example in which the worm gear device 1 according to the first embodiment of the present invention is applied to a surveillance camera drive device. FIG. 1 is a perspective view of the worm gear device 1 viewed from the worm wheel 3 side, and FIG. 2 is a perspective view of the worm gear device 1 viewed from the worm 4 side. FIG. 3 is an exploded perspective view of the worm gear device 1. However, in FIG. 3, illustration of a part of the screw for attachment is omitted. In addition, in each figure, all the bearings are drawn typically.

  1, 2, and 3, a worm gear device 1 includes a support base 2, a worm wheel 3 that is rotatably supported by the support base 2, a worm 4 that meshes with the worm wheel 3, and a worm at one end side portion. 4 is supported between the worm support movable holder 5 and the support base 2 while the other end portion is supported by the support base 2 so as to be swingable. And a coil spring 58 that is provided and presses the worm 4 against the worm wheel 3. In the figure, the worm wheel 3 and the worm 4 are not shown with their teeth in order to make the drawing easier to see.

  The support base 2 is formed with a first support base 8 to which a flanged cylindrical portion 6 is attached with a screw 7 and a rectangular hole 9 through which the central portion of the first support base 8 is exposed and the flanged cylindrical portion 6 penetrates. A second support base 10 attached to the first support base 8 with screws 12, and a third support base 11 attached to the first support base 8 with screws 67 to support the worm support movable holder 5 in a swingable manner. , And combined together.

  As shown in FIG. 4, two first bearings 13 are arranged in the thrust-cylinder portion 6 so as to be separated from each other in the thrust direction. A first shaft 15 formed integrally with the worm wheel 3 and extending in a direction perpendicular to the pitch circle 14 is inserted into the first bearings 13. As a result, the worm wheel 3 is supported by the flanged cylindrical portion 6 of the support base 2 via the first bearing 13 and is rotatable about the rotation center axis 16.

  Here, each of the first bearings 13 is a tapered roller bearing. A cylindrical spacer 18 is disposed between the inner rings 17 of the first bearing 13. Moreover, the outer ring | wheel 19 of the 1st bearing 13 located in the upper side in FIG. 4 is contact | abutted inside the upper surface part 6a of the cylindrical part 6 with a flange. The outer ring 19 of the first bearing 13 located on the lower side in FIG. 4 is brought into contact with an adjusting screw disk 21 that is screwed into a screw part 20 formed inside the cylindrical part 6. A tapered roller 22 is disposed between the inner ring 17 and the outer ring 19. Accordingly, by appropriately tightening the adjusting screw 21, both the upper and lower first bearings 13 can be preloaded, and the first bearing 13 is loosely packed in the thrust direction. is there.

  The worm wheel 3 is made of synthetic resin, and has a plurality of helical teeth 3 a on the outer periphery thereof, and has a pitch circle 14. Further, a screw portion 23 is formed at a lower portion of the hollow first shaft 15 formed integrally with the lower surface of the worm wheel 3 in the drawing, and a connection member (not shown) on the surveillance camera body side is connected.

  The worm 4 is meshed with the worm wheel 3. The worm 4 is made of synthetic resin and has teeth 4a on its outer periphery, and has a pitch circle 66. The intersection of the pitch circle 14 of the worm wheel 3 and the pitch circle 66 of the worm 4 is a pitch point 63.

  As shown in FIGS. 1, 3, and 5, the worm 4 has a central axis of rotation via a second bearing 27 at one end side portion (upper portion in FIGS. 1 and 2) of the worm support movable holder 5. It is supported rotatably around 24. That is, the worm 4 has a large-diameter portion 25 in which teeth 4a are formed in the central portion and first and second ends extending in a direction away from the large-diameter portion 25 along the rotation center axis 24 of the worm 4. The two shafts 26 are integrally provided, and are rotatably supported on one end side portion of the worm support movable holder 5 via a second bearing 27 into which the second shaft 26 is inserted.

  Here, for example, an angular ball bearing is used as the second bearing 27. These second bearings 27 are respectively inserted into circular holes 29 formed in the supporting side walls 28 protruding from both side ends of the worm supporting movable holder 5. As shown in FIG. 5, the outer side of the circular hole 29 closer to the electric motor 33 is on the inner side of the outer ring 30 of the second bearing 27 of the support side wall 28 and on the outer side of the outer ring 30 of the inner ring 31. A holding portion 28a formed by extending the outer portion of the support side wall 28 to a position is provided. The second bearing 27 inserted in the circular hole 29 closer to the electric motor 33 has its outer ring 30 brought into contact with the holding portion 28a of the support side wall 28 so that it does not come out from the circular hole 29 to the electric motor 33 side. Is done.

  On the other hand, a threaded portion 34 is formed inside the circular hole 29 far from the electric motor 33, and the adjusting screw 35 is screwed. The adjustment screw 35 is brought into contact with the outer ring 30 of the second bearing 27. Further, the inner ring 31 of each second bearing 27 is brought into contact with the side surface of the large-diameter portion 25 of the worm 4 with the second shaft 26 penetrating therethrough. A plurality of balls 32 are arranged between the outer ring 30 and the inner ring 31. Therefore, it is possible to preload both the second bearings 27 by appropriately tightening the adjusting screw 35 so that the second bearings 27 are backlashed in the thrust direction.

  On the other hand, the worm support movable holder 5 is attached to the third support 11 so as to be swingable around the rotation center axis 36 as shown in FIGS. 1, 3, and 6. That is, the third shaft 37 extended in the axial direction of the worm 4 is attached to both side ends of the other end portion (the lower portion in FIGS. 1 and 2) of the worm support movable holder 5 by screwing. The worm support movable holder 5 is swingably supported by the third support 11 via the third bearing 38 into which the third shaft 37 is inserted.

  Here, for example, an angular ball bearing is used as the third bearing 38. These third bearings 38 are respectively inserted into circular holes 40 formed in both side end walls 39 of the third support 11. As shown in FIG. 6, the outer side of the circular hole 40 closer to the electric motor 33 is inside the outer ring 41 of the third bearing 38 of the side end wall 39 and outside the outer ring 41 of the inner ring 42. A holding portion 39a is provided in which the outer portion of the side end wall 39 is extended to the position. The third bearing 38 inserted into the circular hole 40 closer to the electric motor 33 has its outer ring 41 in contact with the holding portion 39a of the side end wall 39 so that it does not come out of the circular hole 40 toward the electric motor 33. To be.

  On the other hand, a screw portion 43 is formed inside the circular hole 40 far from the electric motor 33, and the adjusting screw disk 44 is screwed together. The adjusting screwing disk 44 is brought into contact with the outer ring 41 of the third bearing 38. Further, the inner ring 42 of each third bearing 38 is brought into contact with the side surface of the large diameter portion 25 of the third shaft 37. A plurality of balls 45 are arranged between the outer ring 41 and the inner ring 42. Therefore, it is possible to preload both the third bearings 38 by appropriately tightening the adjusting screwing disc 40, and the backlash in the thrust direction is reduced. In FIG. 6, the electric motor 33, the worm wheel 3, the pitch circle 14, the pitch point 63, and the rotation center of the worm 4 are shown so that the positional relationship between the electric motor 33, the worm wheel 3 and the worm 4 can be easily understood. An axis 24 is drawn.

  As shown in FIGS. 1 to 3 and 5, the third support 11 is provided with a stopper 46, and the stopper 46 can be brought into contact with the worm support movable holder 5. It is intended to regulate excessive separation from That is, the stopper plate 47 is attached to the surface of the third support 11 opposite to the worm wheel 3 with the screw 52, and the stopper portion 50 having the long hole 49 and capable of contacting the worm support movable holder 5 is the stopper. The position with respect to the plate 47 is adjusted and fixed with screws 51. By this position adjustment, the escape amount of the worm 4 (the amount that can be separated from the worm wheel 3) can be adjusted.

  As shown in FIGS. 1, 2, and 3, the electric motor 33 is attached to a plate 53 fixed to the second support base 10 with screws 52 with screws 48, and a pinion 55 is attached to the output shaft 54 thereof. Fixed. The pinion 55 is meshed with a gear wheel 56 fixed to the second shaft 26 on the electric motor 33 side of the worm 4.

  A spring holding plate 57 is fixed to the first support base 8 and the second support base 10 with screws 68. A coil spring 58 is attached between the spring holding plate 57 and the worm support movable holder 5 so as to press the worm 4 against the worm wheel 3 with an elastic force so as to remove backlash therebetween. To work. In other words, the locking plate 61 in which the four screw holes 60 are formed is fixed to the spring holding plate 57 in which the long holes 59 are formed with the screws 69 adjusted in relative positions with respect to the spring holding plate 57. A locking portion 61 a for locking one end portion of the coil spring 58 is formed on the locking plate 61, and a screw 62 for locking the other end portion of the coil spring 58 is attached to one support side wall 28 of the worm support movable holder 5. Then, a coil spring 58 is attached between them. The coil spring 58 constitutes the elastic pressing member of the present invention.

  In the worm gear device 1 configured as described above, the second bearing 27 that rotatably supports the worm 4 has the rotation center shaft 24 that passes through the pitch point 63 of the worm wheel 3 and the worm 4 and the worm wheel. 3 are arranged so as to be parallel to the tangent line 64 in contact with the third pitch circle 14. The rotation center shaft 24 of the second bearing 27 moves slightly as the worm support movable holder 5 swings, but when the worm 4 is pressed against the worm wheel 3, the pitch circle 14 of the worm wheel 3. The worm support movable holder 5 has a shape and dimensions, a position where the worm support movable holder 5 is attached to the third support base 11, and the worm support movable holder 5. A support position and the like are set.

  On the other hand, the third bearing 38 that supports the worm support movable holder 5 in a swingable manner has the rotation center axis 36 parallel to the tangent line 64 and the rotation center axis 36 of the worm wheel 3 from the surface where the pitch circle 14 exists. Are arranged so as to pass through positions separated in the direction of the parallel line 65 which is parallel to the line 65. Here, the parallel lines 65 are set so as to pass through the pitch points 63.

  The operation of the worm gear device 1 configured as described above will be described below.

  First, when the surveillance camera is stopped, the electric motor 33 is stopped. At this time, since the output shaft 54 of the electric motor 33 does not rotate, all of the pinion 55, the gear wheel 56, the worm wheel 3, and the worm 4 are stopped. In this stop state, the electric motor 33 cannot be rotated from the monitoring camera side by the auto-lock function by the worm wheel 3 and the worm 4, and the monitoring camera continues to remain stationary.

  On the other hand, to rotate the surveillance camera, the electric motor 33 is operated and the output shaft 54 is rotated. By the rotation of the output shaft 54, the pinion 55 integrated with the output shaft 54 rotates and rotates the gear wheel 56 that meshes with the pinion 55 while decelerating. The gear wheel 56 rotates the worm 4 via the second shaft 26 integrated therewith. The worm 4 rotates about the rotation center axis 24 and rotates the worm wheel 3 meshed with the worm 4 around the rotation center axis 16 perpendicular to the rotation center axis 24 while decelerating at a larger reduction ratio. .

  The meshing between the worm wheel 3 and the worm 4 is performed in a state where the worm 4 is pressed against the worm wheel 3 by the coil spring 58 and the backlash between them is removed. In this case, the worm support movable holder 5 is swingably supported from both sides by the third bearing 38 in which the rotation center shaft 36 is disposed so as to be parallel to the tangent line 64 passing through the pitch point 63 and in contact with the pitch circle 14. Therefore, the worm support movable holder 5 is suppressed so that the amount of play in the direction perpendicular to the pitch circle 14 is smaller than that in the case of cantilever. Further, the third bearing 38 arranged so that the rotation center shaft 24 is parallel to the tangent line 64 is loosely packed in the thrust direction (direction of the rotation center shaft 36), and the worm support movable holder 5 can be swung. The second bearing 27 is also loosely packed in the thrust direction (the direction of the rotation center shaft 24) and the worm 4 is rotatably supported by the worm support movable holder 5, so that the worm support movable holder 5 and the worm No. 4 is also suppressed in the surface direction of the pitch circle 14 so that the amount of play is small.

  Therefore, the worm 4 is pressed against the worm wheel 3 by the coil spring 58 in a state where the backlash in the surface direction of the pitch circle 14 and the direction perpendicular to the surface is small, and the rotation center axis of the worm 4 Since the worm support movable holder 5 swings so that 24 is parallel to the tangent line 64 and is located on or near the surface of the pitch circle 14 and meshes with the worm wheel 3, the worm wheel 3 and the worm 4 are In the state where the backlash between them is removed, the meshing rotation is started.

  As a result, the surveillance camera can be smoothly rotated without blurring due to backlash, so that a clearer and easier-to-see image can be provided, or the surveillance camera can be rotated to a desired position with higher accuracy. become.

  According to the worm gear device according to the first embodiment of the present invention, the first bearing 13 that supports the worm wheel 3 on the support base 2 and the second bearing 27 that supports the worm 4 on the worm support movable holder 5. The third bearing 38 that supports the worm support movable holder 5 on the support base 2 is loosely packed in the thrust direction, and the second bearing 27 and the rotation center shaft 24 have the pitch point 63 of the worm wheel 3 and the worm 4. The third bearing 38 is disposed so as to be parallel to the tangent line 64 that is in contact with the pitch circle 14 of the worm wheel 3 and the rotative axis 36 is parallel to the tangent line 64 and the pitch circle 14 passes through the worm. Since the wheel 3 is arranged so as to pass through a position separated in the direction of the parallel line 65 parallel to the rotation center axis 16 of the wheel 3, the backlash amount of the worm 4 is reduced. The backlash between the worm wheel 3 and the worm 4 is suppressed not only in the surface direction of the pitch circle 14 of the wheel 3 but also in the direction of the rotation center axis 16 of the worm wheel 3 perpendicular to the surface. Can be removed automatically. Further, the third bearing 38 is arranged at a pitch point 63 or in the vicinity of the pitch point 63 parallel to the rotation center axis 16 of the worm wheel 3 from the surface where the rotation center axis 36 is parallel to the tangent line 64 and the pitch circle 14 exists. Since it is arranged so as to pass through a position separated in the direction of the parallel line 65 that passes through, the rotation center shaft 24 and the third axis of the second bearing 27 are compared with the case where the parallel line 65 does not pass through the pitch point 63 or the vicinity of the pitch point 63. The distance between the bearing 38 and the rotation center shaft 36 can be shortened. As a result, the worm support movable holder 5 can be made compact.

  Next, a worm gear device according to a second embodiment of the present invention will be described with reference to FIG. The substantially same parts as those of the worm gear device 1 according to the first embodiment shown in FIGS. 1 to 6 are denoted by the same reference numerals and the description thereof is omitted. FIG. 7 is an enlarged view of a portion of the worm gear device 70 where the worm 4 is supported, and the other portions are the same as those of the worm gear device 1 according to the first embodiment. Omitted.

  As shown in FIG. 7, the worm gear device 70 includes an outer ring 30 of one second bearing 27 that rotatably supports a second shaft 26 having a smaller diameter integrated with a large diameter portion 25 of the worm 4, and the worm support movable holder 5. The disc spring 71 is interposed between the adjustment screwing disc 35 screwed to the disc and the disc spring 71 is interposed between the outer ring 30 of the other second bearing 27 and the holding portion 28 a of the worm support movable holder 5. This is different from the worm gear device 1 according to the first embodiment.

  The disc spring 71 constitutes an elastic preloading member of the present invention, and both the disc springs 71 are preloaded and press the worm 4 with preload applied from both sides. In this preload, when the worm 4 receives an excessive force in the thrust direction from the worm wheel 3, the worm 3 moves slightly in the direction in which the force acts while deflecting the disc spring 71 in the axial direction and escapes. When it is smaller, the size is set so as not to deform.

  The operation of the worm gear device 70 configured as described above will be described below.

  When an excessive force in the thrust direction that causes a problem in meshing with the worm 4 does not act, the operation is the same as that of the worm gear device 1 according to the first embodiment. At this time, the disc spring 71 is not deformed in the attached state.

  However, when an excessive force in the thrust direction is applied to the worm 4, the worm 4 can move away in the thrust direction, that is, the axial direction of the worm 4 while compressing and deforming the disc spring 71 in the pressing direction. Such problems as biting between the worm wheel 3 and the worm 4 and an overload on the electric motor 33 are prevented.

  As described above, according to the worm gear device 70 of the second embodiment of the present invention, the same effect as the worm gear device 1 according to the first embodiment can be obtained, and one of the second bearings 27 can be obtained. The worm wheel 3 when an excessive force in the thrust direction is applied to the worm 4 by providing the disc spring 71 that preloads the worm 4 with the elastic force from the bearing toward the other of the second bearings 27. It is possible to prevent problems such as biting between the worm 4 and the worm 4 and an overload on the electric motor 33.

  In the present invention, a part of the configuration of the worm gear device 1 and the worm gear device 70 according to each of the above embodiments can be modified or changed.

  That is, the worm wheel 3 and the worm 4 are made of synthetic resin, but may be made of metal. Further, the teeth of the worm wheel 3 may be flat teeth instead of helical teeth.

  Further, the first bearing 13, the second bearing 27, and the third bearing 38 are not limited to tapered roller bearings or angular ball bearings, and other types of bearings may be used as long as they can be loosely packed in the thrust direction. May be.

  Further, the parallel line 65 is set so as to pass through the pitch point 63, but the parallel line 65 does not necessarily pass through the pitch point 63, and the worm support movable holder 5 swings so that the worm 4 meshes with the worm wheel 3. The rotation center axis 24 of the worm 4 may be located on the surface of the pitch circle 14 or in the vicinity thereof in parallel with the tangent line 64.

  Furthermore, the elastic preload member is not limited to the disc spring 71, but may be another type of elastic member, or the mounting position thereof may be different.

  As described above, the worm gear device according to the present invention suppresses the amount of worm play not only in the direction of the surface of the pitch circle of the worm wheel but also in the direction of the central axis of rotation of the worm wheel perpendicular to this surface. Thus, the backlash between the worm and the worm wheel can be automatically removed, which is useful as a driving device for a surveillance camera and the like, and can also be applied to a driving device for a telescope, for example.

The perspective view which looked at the worm gear apparatus concerning the 1st Embodiment of this invention from the worm wheel side The perspective view which looked at the worm gear device concerning the 1st embodiment of the present invention from the worm side 1 is an exploded perspective view of a worm gear device according to a first embodiment of the present invention. The figure which shows the support part of the worm wheel The figure which shows the support part of the worm The figure which shows the rocking | swiveling part of a worm support movable holder The partial cross-section enlarged view of the support part of the worm which concerns on the 2nd Embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,70 Worm gear apparatus 2 Support stand 3 Worm wheel 4 Worm 5 Worm support movable holder 8 1st support stand (support stand)
10 Second support stand (support stand)
11 Third support stand (support stand)
13 First bearing 14 Pitch circle 16 Rotation center shaft 24 Rotation center shaft 27 Second bearing 33 Electric motor 36 Rotation center shaft 38 Third bearing 58 Coil spring (elastic pressing member)
63 Pitch point 64 Tangent line 65 Parallel line 66 Pitch circle 71 Disc spring (elastic preload member)

Claims (3)

A support base;
A worm wheel having a pitch circle and having a first shaft extending in a direction perpendicular to the pitch circle rotatably supported by the support base via a first bearing;
A worm meshing with the worm wheel;
One end side portion has a second bearing for rotatably supporting the worm from both side end sides, and the other end side portion is supported by the support base from the both side end sides via a third bearing so as to be swingable. Worm support movable holder,
An elastic pressing member provided between the worm support movable holder and the support base and pressing the worm against the worm wheel;
Backlash the first bearing, the second bearing, and the third bearing in the thrust direction,
The second bearing is disposed such that the rotation center axis thereof is parallel to a tangent line that passes through the pitch point of the worm wheel and the worm and touches the pitch circle of the worm wheel,
The third bearing is arranged so that the rotation center axis thereof is parallel to the tangent line and passes through a position separated from the surface where the pitch circle exists in the direction of the rotation center axis of the worm wheel. Worm gear device. The third bearing has a parallel line passing through the pitch point or the vicinity of the pitch point in parallel with the rotation center axis of the worm wheel from a surface where the rotation center axis is parallel to the tangent line and the pitch circle exists. The worm gear device according to claim 1, wherein the worm gear device is disposed so as to pass through positions separated in a direction. The worm gear according to claim 1, further comprising an elastic preloading member that preloads the worm with an elastic force from one of the second bearings toward the other of the second bearings. apparatus.

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