JP2013210007A - Worm gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a worm gear having high precision, high strength and high efficiency without causing tooth tip interference on the engagement of a worm shaft with a worm wheel even in a case of a low pressure angle or a small curvature radius and by providing an arcuate tooth profile curve capable of increasing a tooth root width.SOLUTION: Tooth profiles of a worm shaft 10 and a worm wheel are configured such that a cross-sectional shape in the direction perpendicular to a tooth part of the worm shaft 10 is such a composite arcuate tooth profile that a tooth profile curve F10 of the tooth root side and a convex arcuater shape of the tooth tip side make a tangent in common to each other at a pitch point c or in the vicinity of the pitch point c, and corresponding to the tooth part shape of the worm shaft 10, the cross-sectional shape in the perpendicular direction of the tooth part of the worm wheel is configured such that a concave arcuate shape of the tooth root side and a convex arcuate shape of the tooth tip side make a tangent in common to each other at a pitch point or in the vicinity of the pitch point.

Description

  The present invention relates to a worm gear.

  Conventionally, in worm gears, the tooth section has a strength that can withstand high output and high torque, and in order to achieve downsizing, the cross-sectional shape of the tooth portion is not an involute tooth shape, but a single concave arc shape Neiman tooth shape, A device such as increasing the original width has been devised (for example, see FIG. 5 of Patent Document 1).

International Publication No. 2008/123588

According to Patent Document 1, the tooth profile in the cross section of the tooth of the worm shaft is a single concave arc shaped Neiman tooth profile, and the tooth root width can be increased and the strength can be increased compared to the case of the conventional involute tooth profile.
The prior art of Patent Document 1 will be described in more detail with reference to FIGS.
FIG. 6 is a diagram illustrating a Neiman tooth profile corresponding to the prior art of Patent Document 1. In FIG.
FIG. 7 is a view showing an involute tooth profile as compared with a Neiman tooth profile, and corresponds to FIG.

  In FIG. 6, a tooth profile curve F30, which is a Neiman tooth profile of the worm shaft 30 of the prior art, has a concave arc shape with a radius of curvature (hereinafter, the radius of curvature may be simply referred to as a radius) R3, and a pressure angle in the pitch circle Pc. The pressure angle α3 and the tooth root width B3 are larger than the pressure angle α5 and the tooth root width B5 in the pitch circle Pc of the involute tooth profile F50 shown in FIG.

  However, as in the tooth profile curve F40 of the worm shaft 40 indicated by a two-dot chain line in FIG. 6, when the pressure angle α4 in the pitch circle Pc is lower than the pressure angle α3, or the radius R4 is smaller than the radius R3. In this case, the protruding tooth tip indicated by P4 in the drawing may interfere with the tooth root portion of the worm wheel (not shown), and the tooth width B4 shown in the drawing becomes smaller than the tooth width B3. 7 may be smaller than the tooth root width B5 of the involute tooth profile F50 shown in FIG. 7, and the superiority of the Neiman tooth profile of high strength, high output, and high torque may not be exhibited.

  In view of the above-described circumstances, the present invention has an arc shape that can increase the root width without causing tooth tip interference when the worm shaft and the worm wheel are engaged even in the case of a low pressure angle or a small curvature radius. The objective is to provide a worm gear with high accuracy, high strength and high efficiency by realizing a tooth profile curve.

The present invention solves the above problems by the following means.
(1) The worm gear of the first means is a worm gear comprising a worm shaft whose tooth cross section is an arc-shaped tooth profile and a worm wheel meshing with the worm shaft. The worm shaft has a cross-sectional shape in the direction perpendicular to the tooth portion of the shaft, which is a composite arc tooth shape having a tangent side concave arc shape and a tooth tip side convex arc shape having a common tangent line at or near the pitch point. According to the tooth shape of the worm wheel, the cross-sectional shape in the perpendicular direction of the tooth portion of the worm wheel is a common tangent line at the pitch point or in the vicinity of the pitch point of the concave arc shape on the tooth root side and the convex arc shape on the tooth tip side. It is comprised so that it may become a compound circular arc tooth profile.

(2) The worm gear of the second means is a worm gear of the first means, wherein the concave arc shape on the tooth root side of the worm shaft is a plurality of concave arc shapes having mutually different radii of curvature. According to the shape of the tooth portion of the worm shaft, the convex arc shape on the tooth tip side of the worm wheel is composed of a plurality of convex arc shapes having mutually different radii of curvature, A convex arc shape on the tooth tip side of the worm shaft is constituted by a plurality of convex arc shapes having different radii of curvature that share a tangent to each other, and the teeth of the worm wheel according to the tooth shape of the worm shaft. The original concave arc shape is constituted by a plurality of concave arc shapes having different radii of curvature having a common tangent to each other.

According to a first aspect of the present invention, there is provided a worm gear including a worm shaft having a tooth profile having a circular arc-shaped tooth profile and a worm wheel meshing with the worm shaft. The cross-sectional shape in the right-angle direction of the tooth portion is a compound arc tooth profile in which the concave arc shape on the tooth base side and the convex arc shape on the tooth tip side are common to each other at the pitch point or in the vicinity of the pitch point. According to the shape of the part, the cross-sectional shape in the perpendicular direction of the tooth portion of the worm wheel is such that the concave arc shape on the tooth base side and the convex arc shape on the tooth tip side are tangent to each other at or near the pitch point. By configuring it as a complex arc tooth profile, it is possible to achieve a low pressure angle, and to achieve a high-precision, high-load capacity, high-efficiency worm gear. It has the effect that the door can be.
In addition, the number of options for increasing the tooth root width of the worm wheel is increased, and the bending strength can be improved by the large tooth root width.

  According to a second aspect of the present invention, in the worm gear according to the first aspect, the concave arc shape on the tooth root side of the worm shaft is configured by a plurality of concave arc shapes having mutually different radii of curvature that are tangent to each other. According to the shape of the tooth portion of the worm shaft, the convex arc shape on the tooth tip side of the worm wheel is constituted by a plurality of convex arc shapes having different radii of curvature that are tangent to each other, The convex arc shape on the tooth tip side of the worm shaft is composed of a plurality of convex arc shapes having different radii of curvature that have a common tangent to each other, and according to the tooth shape of the worm shaft, the tooth root of the worm wheel The concave arc shape on the side is composed of a plurality of concave arc shapes with different radii of curvature that share the same tangent line, so that the selection of the tooth profile curve and the worm shaft or wall An effect that variety spreads the choice of dedendum width or pressure angle Muhoiru.

It is meshing sectional drawing of the worm gear concerning the 1st Embodiment of this invention. It is a tooth profile figure of the worm shaft of the worm gear shown in FIG. It is a figure explaining the tooth profile by this invention in contrast with the conventional Neiman tooth profile. It is a meshing sectional view of the worm gear according to the second embodiment of the present invention, and corresponds to FIG. It is a tooth profile figure of the worm shaft of the worm gear shown in FIG. It is a figure explaining the Neiman tooth profile equivalent to the prior art of patent document 1. FIG. It is a figure which shows the involute tooth profile compared with a Neiman tooth profile, and is a figure equivalent to FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or that are substantially the same.
(First Embodiment of the Invention)

A first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a meshing sectional view of a worm gear according to a first embodiment of the present invention.
FIG. 2 is a tooth profile of the worm shaft of the worm gear shown in FIG.
In FIG. 1, the worm gear 1 includes a worm shaft 10 and a worm wheel 10w that mesh with each other, and the pitch circle Pc10 of the worm shaft 10 and the pitch circle Pc10w of the worm wheel 10w are in contact with each other as illustrated. .

In FIG. 2, the tooth profile curve F10 of the cross section of the tooth of the worm shaft 10 indicates that the root side between the end a of the root width B1 and the pitch point c in the pitch circle Pc has a radius of curvature (hereinafter simply referred to as a radius of curvature). Ra) is formed by a concave arc of Ra, and the tooth tip side between the pitch point c and the tooth tip b is formed by a convex arc of radius Rb, and the tangent and radius of the concave arc of radius Ra The tangent line of the convex arc of Rb is a composite arc tooth profile common to the pitch points.
The tooth profile curve F10 has a pressure angle α1 at the pitch point c.

  The worm wheel 10w has a tooth profile curve that fits with the teeth of the worm shaft 10 described above, and a detailed illustration is omitted, but the tooth base side is formed as a concave arc, and the tooth tip side is It is formed by a convex arc, and is a composite arc tooth profile in which the tangent of the concave arc on the tooth base side and the tangent of the convex arc on the tooth tip side are common at the pitch point.

Next, the operation of the worm gear 1 according to the first embodiment of the present invention will be described.
The tooth of the worm shaft 10 adopts the tooth profile curve F10, so that the low pressure angle α1 and the radius Ra of the concave arc on the tooth root side are reduced, and a convex arc of the radius Rb on the tooth tip side is formed. Therefore, there is no protrusion of the prior art as shown in FIG. 6 (protrusion P4 as shown in FIG. 6) at the tooth tip part b, and there is no interference with the tooth root part of the worm wheel 10w engaged with the worm shaft 10.
Further, by adopting the tooth profile curve F10, the tooth root width B1 can be increased, the bending strength of the tooth root portion of the worm shaft 10 can be improved, and the tooth root width of the worm wheel 10w is also increased. Therefore, the bending strength of the tooth base portion of the worm wheel 10w can also be improved.

The features of the tooth profile curve F10 of the worm shaft 10 will be described in more detail with reference to FIG.
FIG. 3 is a diagram illustrating a tooth profile according to the present invention in comparison with a conventional Neiman tooth profile.
In FIG. 3, the axial direction of the worm shaft (hereinafter, the worm shaft may be simply referred to as a worm) 10 is the z direction, the central axis direction of the worm wheel 10w that is perpendicular to the z direction and meshes with the worm 10 is the y direction, A direction perpendicular to the y direction and the z direction is represented as an x direction.
The (a) worm cross section also shows a partial cross section of a tool (grinding stone) for forming the tooth profile of the worm 10.
Further, (b) the contact line with the grindstone shows the contact line between the worm 10 and the grindstone, (c) the meshing section shows the meshing section of the worm 10 and the worm wheel 10w, d) The simultaneous contact line shows the contact line in meshing of the worm 10 and the worm wheel 10w.
In the case of the conventional Neiman tooth profile, similarly, the x direction, the y direction, and the z direction are illustrated.

As shown in FIG. 3, the cross-sectional shape of the grinding wheel for tooth profile according to the present invention is naturally different from the cross-sectional shape of the conventional grinding wheel for Neiman tooth profile, and the contact line with the grinding stone is also different as shown in the figure. doing.
From the comparison of the meshing section between the worm 10 and the worm wheel 10w and the meshing section between the worm 30 and the worm wheel 30w, the tooth root width B1w of the worm wheel 10w is made larger than the tooth root width B3w of the worm wheel 30w. Therefore, the bending strength of the base portion of the worm wheel 10w is improved.

  In addition, as can be seen from the comparison between the case of the tooth profile according to the present invention and the case of the conventional Neiman tooth profile, (d) in the case of the tooth profile according to the present invention, the contact near the pitch circle is around the pitch circle. (In contrast, in the case of the conventional Neiman tooth profile, it is dense in the direction perpendicular to the pitch circle), and the sensitivity of the tooth contact change to the error in the distance between the centers of the worm and the worm wheel is reduced. Therefore, it is possible to obtain a worm gear with high accuracy, load capacity and efficiency.

In the above description, the concave arc on the tooth base side and the convex arc on the tooth tip side of the worm shaft 10 have been described with reference to the case where the common tangent lines of both are connected at the pitch point c as shown in FIG. The connection of the tangent line is not limited to the pitch point c. The connection of the common tangent line may be in the vicinity of the pitch point c, and its operation is similar to the above description. Omitted.
In the above description, the concave arc on the tooth root side of the worm shaft 10 has been described as starting from the end a of the tooth width B1, but the starting point is not limited to the point a shown in the figure. It may be in the vicinity of a point, and its operation is similar to that described above, and thus detailed description thereof is omitted.
(Second Embodiment)

Next, a worm gear 2 according to a second embodiment of the present invention will be described with reference to FIGS.
FIG. 4 is a meshing sectional view of a worm gear according to the second embodiment of the present invention, and corresponds to FIG.
FIG. 5 is a tooth profile of the worm shaft of the worm gear shown in FIG.
4, the worm gear 2 includes a worm shaft 20 and a worm wheel 20w that mesh with each other, and the pitch circle Pc20 of the worm shaft 20 and the pitch circle Pc20w of the worm wheel 20w are in contact with each other as illustrated. .

In FIG. 5, the tooth profile curve F20 of the cross section of the tooth of the worm shaft 20 shows that the tooth root side between the end portion d of the tooth root width B2 and the pitch point f in the pitch circle Pc is common at each contact point s. Are formed with a concave arc of radius Rd and two concave arcs of radius Rs, and the tooth tip side between the pitch point f and the tooth tip e is a radius Rt in which the respective tangents are common at the contact t. And a convex arc shape having two radii of radius Re and a tangent line of the concave arc of radius Rs and a tangent line of the convex arc of radius Rt are combined at the pitch point f. .
The tooth profile curve F20 has a pressure angle α2 at the pitch point f.

  The worm wheel 20w has a tooth profile curve that fits with the teeth of the worm shaft 20 described above, and a detailed illustration is omitted, but the tooth base side has two concave arc shapes with different curvature radii. The tooth tip side is formed in two convex arc shapes with different curvature radii, and the tangent line of the concave arc on the pitch point side on the tooth base side and the tangent line of the convex arc on the pitch point side on the tooth tip side Is a common arc tooth profile common to the pitch points.

Next, the operation of the worm gear 2 according to the second embodiment of the present invention will be described.
Since the tooth of the worm shaft 20 adopts the tooth profile curve F20, the low pressure angle α2 and the radius Rd of the concave arc on the tooth root side can be reduced, and the convex arc of the radius Re on the tooth tip side can be formed. Therefore, there is no conventional protrusion (protrusion P4 as shown in FIG. 6) as shown in FIG. 6 at the tooth tip part e, and there is no interference with the tooth root part of the worm wheel 20w meshing with the worm shaft 20.
Further, by adopting the tooth profile curve F20, the tooth root width B2 can be increased, the bending strength of the tooth root portion of the worm shaft 20 can be improved, and the tooth root width of the worm wheel 20w is also increased. It is possible to improve the bending strength of the tooth base portion of the worm wheel 20w.

  Here, in the second embodiment of the present invention, the tooth base side is formed by two concave arcs having different radii of curvature, so selection of the size of the tooth root width B2 of the tooth of the worm shaft 20 is performed, The degree of freedom can be increased according to the strength and the like of the target worm gear 2, and the degree of freedom can be increased according to the meshing performance of the target worm gear 2 and the selection of the size of the pressure angle α2. Can do.

  In the above description, the case where the tooth base side and the tooth tip side are formed with two arc shapes with different curvature radii has been described. However, the arc shape is not limited to two, and a plurality of three or more with different curvature radii are used. Alternatively, only one of the tooth base side and the tooth tip side may be formed into a plurality of arc shapes, and the selection may be made according to the intended strength, meshing performance, etc. of the worm gear.

Since the comparison with the conventional Neiman tooth profile in the second embodiment of the present invention is the same as that described in the first embodiment of the present invention, a detailed description thereof will be omitted.
In the above description, a plurality of concave arcs having different radii of curvature on the tooth base side of the worm shaft 20 and a plurality of convex arcs having different radii of curvature on the tooth tip side are represented by a common tangent line as shown in FIG. Although the case where they are connected at the pitch point f has been described, the connection of the two common tangents is not limited to the pitch point f, and the connection of the two common tangents may be near the pitch point f. Is the same as that described in the first embodiment of the present invention, and a detailed description thereof will be omitted.
In the above description, the concave arc on the tooth base side of the worm shaft 20 is described as starting from the end d of the tooth width B2, but the starting point is not limited to the illustrated point d. The fact that it may be in the vicinity of a point is the same as that described in the first embodiment of the present invention, and a detailed description thereof will be omitted.

1, 2, Worm gear 10, 20, Worm shaft (worm)
10w, 20w Worm wheel B1, B2 Root width F10, F20 Tooth profile curve Pc Pitch circle Ra, Rd, Rs (curvature) radius of concave arc (tooth side) Rb, Re, Rt Convex arc (tooth side) (Curvature) radius c, f Pitch point α1, α2 Pressure angle

Claims (2)

  In a worm gear comprising a worm shaft having a tooth profile with an arc-shaped tooth profile and a worm wheel meshing with the worm shaft, the tooth profile of the worm shaft and the worm wheel has a cross-sectional shape in a direction perpendicular to the tooth portion of the worm shaft. A concave arc shape on the tooth base side and a convex arc shape on the tooth tip side are composite arc tooth shapes having a common tangent to each other at the pitch point or in the vicinity of the pitch point, and in accordance with the tooth shape of the worm shaft, The cross-sectional shape in the right-angle direction of the tooth portion of the wheel is configured such that the concave arc shape on the tooth root side and the convex arc shape on the tooth tip side are a composite arc tooth shape having a common tangent line at or near the pitch point. Worm gear characterized by that.   2. The worm gear according to claim 1, wherein the concave arc shape on the tooth root side of the worm shaft is configured by a plurality of concave arc shapes having mutually different radii of curvature that are tangent to each other, and the tooth portion shape of the worm shaft is formed. Correspondingly, the convex arc shape on the tooth tip side of the worm wheel is constituted by a plurality of convex arc shapes having mutually different radii of curvature, and the convex arc on the tooth tip side of the worm shaft. Consists of a plurality of convex arc shapes with different radii of curvature that share a tangent to each other, and the concave arc shape on the tooth base side of the worm wheel is common to each other according to the tooth shape of the worm shaft A worm gear comprising a plurality of concave arc shapes having different radii of curvature.

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