JP2004360877A - Involute gear - Google Patents

Abstract

An involute gear has improved tooth strength without impairing its rotation transmitting function.
The entire area of each tooth surface (20, 22) is partitioned into a band-like contact area including a locus of a contact point between the tooth surfaces and extending along the same, and a non-contact area located outside the belt-like contact area. The contact area is formed as an involute helicoid and functions as a tooth contact surface with respect to the tooth surface of the mating gear. The non-contact area is a shape that does not contact the tooth surface of the mating gear, and the strength of the teeth in the involute gear is directly or indirectly compared to the basic tooth surface shape when the entire area is formed as an involute helicoid. Give the modified shape a better orientation. For example, the tooth tip 30 is missing from the basic tooth tip shape on both sides in the tooth width direction, and the tooth bottom 32 is raised from the basic tooth tip shape on both sides in the tooth width direction.
[Selection] Figure 2

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an involute gear having an involute helicoid as a tooth surface, and more particularly to a technique for improving the strength of each tooth of the involute gear.
[0002]
[Prior art]
The gear pair is configured by a pair of gears formed by arranging a plurality of teeth having a pair of front and rear tooth surfaces in front and behind with a tooth groove having a tooth bottom spaced one by one, and meshing with the corresponding tooth surfaces. It is configured as follows. Furthermore, the contact points where the tooth surfaces contact each other trace a locus on each tooth surface as the pair of gears engage and move. This locus is a contact point locus.
[0003]
The present inventor has repeated studies on this contact point locus, and as a result, obtained the following knowledge.
[0004]
That is, when each gear in the gear pair is a spur gear, its contact point trajectory extends along the plane perpendicular to the axis of each spur gear, whereas when it is a helical gear, its contact point It has been found that the point locus extends in a direction intersecting the plane perpendicular to the axis of each helical gear.
[0005]
Furthermore, the present inventor has further studied a technique for reducing free running noise in an involute gear, and as a result, has proposed the following technique. That is, in the central region extending along the contact point locus of each tooth surface of the gear pair, the reference involute helicoid is left as it is as a tooth surface, while in both side regions, the involute helicoid is modified, and this region is modified. He proposed a technology to make it a non-tooth contact area. This proposed technique is disclosed in Patent Document 1 of the present applicant.
[0006]
[Patent Document 1]
JP-A-9-53702
[Problems to be solved by the invention]
For involute gears, in addition to the desire to reduce rotational noise, there is also a desire to improve, for example, the strength of teeth.
[0008]
In view of such circumstances, the present invention has been made to improve the tooth strength of an involute gear without impairing its rotation transmitting function.
[0009]
Means for Solving the Problems and Effects of the Invention
The following aspects are obtained by the present invention. Each aspect is divided into sections, each section is numbered, and if necessary, described in a form in which the numbers of other sections are cited. This is to facilitate understanding of some of the technical features described in the present specification and some of the combinations thereof, and the technical features and the combinations thereof described in the present specification have the following aspects. It should not be construed as limited.
[0010]
(1) A plurality of teeth each having a pair of front and rear tooth surfaces formed as an involute helicoid are formed side by side with a tooth space having a tooth bottom spaced one by one. Is an involute gear that draws a trajectory on each tooth surface as the contact points at which they contact each other move as the pair of gears mesh with each other,
The entire area of each tooth surface thereof is partitioned into a band-shaped contact area extending along the trajectory including the trajectory of the contact point and a non-contact area located outside the contact area,
The contact area is formed as an involute helicoid, and functions as a tooth contact surface with respect to the tooth surface of the mating gear,
The non-contact area is a shape that does not contact the tooth surface of the mating gear, and the strength of the teeth in the involute gear is directly or in comparison with the basic tooth surface shape when the entire area is formed as an involute helicoid. Involute gears given a modified shape to improve indirectly.
[0011]
According to the inventor's research, they move in meshing (here, "moving" is used as a term including not only rotary motion but also linear motion). Directly contributes to transmitting load between gears. This is not a whole area of each tooth surface but a part of it. Specifically, it is a band-like region extending along and including the trajectory of the contact point in the entire region.
[0012]
Therefore, the other region, that is, the region located outside the band-shaped region, is provided on the condition that it does not contact the tooth surface of the mating gear, and for the purpose of improving the strength of the teeth, the entire region is formed. It is possible to change the basic tooth flank shape when formed as an involute helicoid.
[0013]
Based on such knowledge, in the involute gear according to this section, the entire area of each tooth surface extends along the trajectory of the contact point where each tooth surface and each tooth surface of the mating gear contact each other. It is partitioned into a strip-shaped contact area and a non-contact area located outside the contact area.
[0014]
The contact area is formed as an involute helicoid and functions as a tooth contact surface with respect to the tooth surface of the mating gear. On the other hand, the non-contact area is a shape that does not contact the tooth surface of the mating gear, and the strength of the teeth in the involute gear is different from the basic tooth surface shape when the entire area of the tooth surface is formed as an involute helicoid. Is given a modified shape to improve directly or indirectly.
[0015]
Here, the “shape changed so that the strength of the teeth is directly improved” means, for example, a part of the gear that has a given shape and a part whose strength is improved by giving the shape. It means a specific shape that matches each other. One example of such a shape is a shape that is at least locally raised from the basic root shape.
[0016]
On the other hand, "shape changed so that the strength of the teeth is indirectly improved" means, for example, a part of the gear that has a given shape and a part whose strength is improved by giving the shape. Are not coincident with each other, but a particular shape is applied to the first portion to enhance the strength of another second portion that engages the given first portion to allow the second portion to have a particular shape. Means a particular shape as shown. One example of such a shape is a shape that locally removes the shape of the basic tooth tip, thereby enabling a local elevation of the root where the tooth tip fits.
[0017]
The `` shape modified so that the strength of the teeth is directly or indirectly improved '' in this section means, for example, that the original shape of the tooth tip or the tooth bottom is not a direction along the tooth surface, that is, a circumferential direction of the gear. It can be obtained by deforming in the radial direction.
[0018]
(2) The involute gear according to (1), wherein the changed shape is given to both the tooth tip and the tooth bottom, and the given shapes complement each other.
[0019]
Improving the shape of the root is important for improving the strength of the teeth. On the other hand, if it is necessary to change the shape of the tooth bottom, it is also necessary to change the shape of the tooth tip of the mating gear that fits into the tooth bottom in order to ensure a normal meshing motion between the gears. Required.
[0020]
Based on such knowledge, in the involute gear according to this section, the shape changed with respect to the basic tooth surface shape is given to both the tooth tip and the tooth bottom, and the given shapes are mutually different. It has been made to complement.
[0021]
(3) The changed shape is the radius of the involute gear with respect to the basic tooth tip shape and the basic tooth bottom shape located on the cylindrical surface concentric with the involute gear, respectively, for the tooth tip and the tooth bottom. The involute gear according to (2), including a shape changed in the direction.
[0022]
Moving the root position radially outward generally improves the bending strength of the tooth. On the other hand, it is necessary to move the position of the tooth tip inward in the radial direction with such movement, for the normal meshing movement of the gears.
[0023]
Based on such knowledge, in the involute gear according to this section, the shape modified with respect to the basic tooth surface shape is located on the cylindrical surface concentric with the involute gear with respect to the tooth tip and the tooth bottom, respectively. The basic tooth tip shape and the basic tooth bottom shape include a shape changed in the radial direction of the involute gear.
[0024]
(4) The involute gear is a spur gear,
A trajectory of the contact point extends along a plane perpendicular to the axis of the spur gear;
The tip of each tooth is missing from the non-contact area, on both sides in the width direction of each tooth, with respect to the basic tip shape located on a cylindrical surface concentric with the spur gear,
The root in each tooth space is raised on a non-contact area, on both sides in the tooth width direction of each tooth space, with respect to a basic root shape located on a cylindrical surface concentric with the spur gear. The involute gear according to any one of (1) to (3).
[0025]
According to this involute gear, the root of the spur gear is raised on both sides in the width direction of the spur gear with respect to the basic root shape located on the cylindrical surface concentric with the spur gear. The strength is improved.
[0026]
Such a bulge of the root is formed in a non-contact area that does not affect rotation transmission with the mating gear, that is, a cylindrical area concentric with the involute gear in the tooth width direction. This is made possible by the lack of the basic tip shape located on the surface.
[0027]
Therefore, according to this involute gear, it becomes easy to improve the strength of the teeth without impairing the rotation transmission function between the involute gear and the mating gear.
[0028]
Further, according to this involute gear, it is easy to reduce the weight of each tooth at the tip of the tooth, so that it is easy to manufacture an involute gear having small rotational inertia.
[0029]
(5) The involute gear is a helical gear,
The trajectory of the contact point extends in a direction intersecting the plane perpendicular to the axis of the helical gear,
The tip of each tooth is located on a cylindrical surface concentric with the helical gear on one side of the non-contact area, which is farther from the contact point trajectory, on both sides in the tooth width direction of each tooth. Is missing for the basic tooth tip shape
The tooth bottom in each tooth space is located on a cylindrical surface concentric with the helical gear on one side closer to the contact point locus among the two non-contact areas in the width direction of each tooth space. The involute gear according to any one of (1) to (3), which is raised with respect to the basic tooth bottom shape.
[0030]
According to this involute gear, the root of the helical gear is raised on one side in the face width direction with respect to the basic root shape located on the cylindrical surface concentric with the helical gear, As a result, the strength of the root portion is improved.
[0031]
Such a bulge of the tooth bottom has a helical gear in a non-contact area that does not affect rotation transmission with a mating gear, that is, an area on one side in the tooth width direction, among tooth tips fitted into the tooth bottom. This is made possible by the lack of the basic tooth tip shape located on the concentric cylindrical surface.
[0032]
Therefore, according to this involute gear, it becomes easy to improve the strength of the teeth without impairing the rotation transmission function between the involute gear and the mating gear.
[0033]
Further, according to this involute gear, it is easy to reduce the weight of each tooth at the tip of the tooth, so that it is easy to manufacture an involute gear having small rotational inertia.
[0034]
(6) the involute gear is a helical gear,
Of a pair of tooth surfaces of each tooth, a trajectory of a contact point drawn on a tooth surface meshing with the tooth surface of the counterpart gear during forward movement of the helical gear, and a tooth of the counterpart gear during reverse movement. The trajectory of the contact point drawn on the tooth surface which meshes with the surface, in a state where they intersect with each other in a three-dimensional manner, both extend in a direction intersecting the plane perpendicular to the axis of the helical gear,
The tip of each tooth is missing in the non-contact area, at the center in the face width direction of each tooth, with respect to the basic tip shape located on a cylindrical surface concentric with the helical gear. And
A root in each tooth space is raised from a basic root shape located on a cylindrical surface concentric with the helical gear at a central portion in a tooth width direction of each tooth groove in the non-contact area. An involute gear according to any one of the above (1) to (3).
[0035]
In any type of gear, a contact point trajectory is drawn on one of a pair of tooth surfaces sharing the same tooth during forward movement, and a contact point trajectory is drawn on the other tooth surface during reverse movement. Here, “movement” includes both rotational motion and linear motion.
[0036]
In the case of a spur gear, when each tooth of the spur gear is viewed from the direction perpendicular to the axis, the contact point locus drawn on one tooth surface when the spur gear moves in the forward direction and on the other tooth surface when it moves in the reverse direction The contact point trajectories overlap one another three-dimensionally. On the other hand, if the tip of the tooth is locally lost in the non-contact area of each tooth, the effect extends to both the pair of tooth surfaces. However, in the case of a spur gear, when each tooth surface of the spur gear is viewed from the direction perpendicular to the axis, the non-contact area on one tooth surface and the other non-contact area on the other side during forward movement and reverse movement. And three-dimensionally overlap each other.
[0037]
Therefore, in the case of a spur gear, determining the missing position of the tooth tip and the raised position of the tooth bottom in consideration of only the contact point trajectory and the non-contact area at the time of the forward movement is the same as the contact at the time of the backward movement. This is equivalent to determining the missing position of the tooth tip and the raised position of the tooth bottom in consideration of the point trajectory and the non-contact area.
[0038]
On the other hand, in the case of a helical gear, when each tooth of the helical gear is viewed from the direction perpendicular to the axis, the contact point trajectory drawn on one tooth surface during the forward movement of the helical gear and the reverse movement Sometimes, the trajectory of the contact point drawn on the other tooth surface three-dimensionally intersects with each other. Similarly, in the case of a helical gear, when each tooth surface is viewed from a direction perpendicular to the axis, a non-contact area on one tooth surface between forward movement and reverse movement. And the other non-contact area cross each other three-dimensionally.
[0039]
Therefore, in the case of a helical gear, unless both the contact point trajectory and the non-contact area at the time of forward movement and the contact point trajectory and the non-contact area at the time of reverse movement are considered, the tooth tip The missing position and the raised position of the root cannot be properly determined.
[0040]
On the other hand, in the case of a helical gear, the central portion in the tooth width direction of the tooth tip and the central portion in the tooth width direction of the tooth bottom belong to the non-contact area when rotating in any direction.
[0041]
Based on the findings described above, in the involute gear according to this section, the tooth tip is cut off from the basic tip shape at the center in the tooth width direction, and the tooth bottom is shifted in the tooth width direction. Are raised with respect to the basic root shape at the central portion of.
[0042]
Therefore, according to this involute gear, it is easy to improve the strength of the teeth without impairing the rotation transmission function with the mating gear regardless of the rotation direction.
[0043]
Further, according to this involute gear, it is easy to reduce the weight of each tooth at the tip of the tooth, so that it is easy to manufacture an involute gear having small rotational inertia.
[0044]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, some of the more specific embodiments of the present invention will be described in detail with reference to the drawings.
[0045]
FIG. 1 shows a partial perspective view of an involute spur gear 10 according to a first embodiment of the present invention. In the involute spur gear 10, a plurality of teeth 12 are formed along a circumference with one tooth space 14 therebetween. FIG. 1 shows an enlarged view of one of the plurality of teeth 12 and two tooth grooves 14 sandwiching the teeth 12 from front and rear.
[0046]
Each tooth 12 has a pair of tooth surfaces 20, 22 defined before and after it, defined as an involute helicoid. Further, each tooth 12 is provided with a tooth tip 30 that fits into the tooth bottom of a mating gear (not shown). On the other hand, each tooth groove 14 is formed with a tooth bottom 32 into which the tip of the mating gear fits.
[0047]
FIG. 2 is a cross-sectional view of a main part of the involute spur gear 10 cut along a plane including a rotation axis thereof and passing through a tooth bottom 32. In the involute spur gear 10, during meshing rotation with a mating gear (not shown) (this is an example of “meshing movement”), a contact point of the mating gear with the tooth surface moves on each tooth surface 20, 22. It moves along a uniaxial plane that passes through the central portion of each tooth surface 20, 22 in the tooth width direction.
[0048]
The line of intersection between each tooth surface 20, 22 and its plane perpendicular to one axis represents the trajectory of the contact point. More precisely, when the involute spur gear 10 rotates in the forward direction, the contact point trajectory is drawn on the tooth surface 20 on one side of each tooth 12, whereas when the involute spur gear 10 rotates in the reverse direction, the tooth surface on the other side of each tooth 12 A contact point locus is drawn at 22. These contact point trajectories overlap three-dimensionally when each tooth 12 is viewed from the direction perpendicular to the axis.
[0049]
As shown in FIG. 2, on each tooth surface 20, 22, a band-like contact region including the respective contact point trajectories and extending along the trajectories is set. This contact area is defined as an involute helicoid and functions as a tooth contact surface with respect to the tooth surface of the mating gear. Therefore, the force is transmitted between the involute spur gear 10 and the mating gear through the contact area.
[0050]
As shown in FIG. 2, a pair of non-contact regions are further set on the tooth surfaces 20 and 22 outside the contact regions.
[0051]
In this embodiment, the tip 30 of each tooth 12 is cut off on both sides in the tooth width direction with respect to the basic tip shape located on a cylindrical surface concentric with the involute spur gear 10. ing. In the present embodiment, the tooth tip 30 has a convex shape that protrudes radially outward in a round shape with respect to a cross-sectional shape when the tooth tip 30 is cut by a plane including the rotation axis of the involute spur gear 10.
[0052]
As shown in FIG. 2, the root 32 is raised on both sides in the tooth width direction with respect to the basic root shape located on a cylindrical surface concentric with the involute spur gear 10. In the present embodiment, the tooth bottom 32 has a concave shape that is rounded inward in the radial direction with respect to the cross-sectional shape when the tooth bottom 32 is cut by a plane including the rotation axis of the involute spur gear 10. The concave shape is selected so as to complement the convex shape.
[0053]
As described above, in the present embodiment, since the root 32 has a portion raised from the basic root shape, it is easy to improve the strength (for example, bending strength) of each tooth in the involute spur gear 10. is there.
[0054]
Furthermore, in this embodiment, since the tooth tip 30 has a portion missing from the basic tooth tip shape, it is easy to reduce the rotational inertia of the involute spur gear 10.
[0055]
Next, an involute helical gear according to a second embodiment of the present invention will be described.
[0056]
As shown in FIG. 3, in the involute helical gear 50, similarly to the involute spur gear 10, a plurality of teeth 66 having a pair of front and rear tooth surfaces 60, 62 and a tooth tip 64, and a tooth bottom 70 are formed. The tooth grooves are arranged side by side along one circumference with one tooth space therebetween. FIG. 3 shows a case where the main part of the involute helical gear 50 is cut by a drawing method similar to that of FIG. 2 by passing through a tooth bottom 70 which is a plane including the rotation axis thereof. It is shown in cross section.
[0057]
The involute helical gear 50 is used in a state where it rotates only in one direction. Therefore, in the involute helical gear 50, unlike the involute spur gear 10, during the meshing rotation with the not-shown mating gear, the contact point with the tooth surface of the mating gear moves on one tooth surface 60, It moves along one direction that intersects the right-angled plane. As described above, in the involute helical gear 50, only the tooth surface 60 of the pair of tooth surfaces 60 and 62 of each tooth 66 is the meshing tooth surface, and the other tooth surface 62 is the non-meshing tooth surface. Therefore, the contact point locus is drawn only on the tooth surface 60.
[0058]
As shown in FIG. 3, on the tooth surface 60, a band-like contact region extending along and including the contact point locus of the tooth surface 60 is set. This contact area is defined as an involute helicoid and functions as a tooth contact surface with respect to the tooth surface of the mating gear. Therefore, through the contact area, the involute transmits a force between the helical gear 50 and the mating gear.
[0059]
As shown in FIG. 3, on the tooth surface 60, a pair of non-contact areas are further set outside the contact area.
[0060]
In the present embodiment, the tip 64 of each tooth 66 has a cylindrical shape concentric with the helical gear 50 on one side of the both sides in the tooth width direction of each tooth 66 farther from the contact point locus. It is missing for the basic tip shape located on the surface. In the present embodiment, the tooth tip 64 is cut off by a plane that is generally parallel to the contact point trajectory at the end of the both ends in the tooth width direction that is far from the intersection between the tooth tip 64 and the contact area. ing.
[0061]
As shown in FIG. 3, the root 70 is raised with respect to a basic root shape located on a cylindrical surface concentric with the helical gear 50 so that the root 70 extends along the contact point locus. . In the present embodiment, the tooth bottom 70 is raised to the vicinity of a boundary line that separates the contact region and the non-contact region on the inner peripheral side from each other.
[0062]
As described above, in the present embodiment, since the root 70 has a portion raised from the basic root shape, the involute can easily improve the strength of each tooth in the helical gear 50.
[0063]
Furthermore, in this embodiment, since the tooth tip 64 has a portion missing from the basic tooth tip shape, the involute can easily reduce the rotational inertia of the helical gear 50.
[0064]
Next, an involute helical gear according to a third embodiment of the present invention will be described.
[0065]
As shown in FIG. 4, in the involute helical gear 100, similarly to the involute helical gear 50, a plurality of teeth 116 having a pair of front and rear tooth surfaces 110, 112 and a tooth tip 114 are provided. 120 are arranged side by side along one circumference with one tooth space therebetween. FIG. 4 shows a case where the main portion of the involute helical gear 100 is cut by a method similar to that of FIG. 3 by passing through a tooth bottom 120 which is a plane including the rotation axis thereof. It is shown in cross section.
[0066]
The involute helical gear 100 is used in a state where meshing rotation with a mating gear is performed in both forward and reverse directions. Therefore, unlike the second embodiment, the involute improves the strength of the teeth 116 without impairing the rotation transmitting function of the helical gear 100 regardless of the shape of the tooth tip 114 and the tooth bottom 120 regardless of the rotation direction. It is in a shape suitable for being made.
[0067]
Specifically, at the time of forward rotation, the contact point between the tooth surfaces of the involute helical gear 100 and the mating gear is on the tooth surface 110 seen in FIG. 4 along one direction intersecting the plane perpendicular to the axis. Move.
[0068]
On the other hand, at the time of the reverse rotation, the contact point moves on the tooth surface 112 where the contact point is not visible in FIG.
[0069]
As shown in FIG. 4, on each tooth surface 110, 112, a band-like contact area including the respective contact point trajectories and extending along the trajectories is set. This contact area is defined as an involute helicoid and functions as a tooth contact surface with respect to the tooth surface of the mating gear. Therefore, through this contact area, the transmission of the force between the helical gear 100 and the mating gear of the involute is performed irrespective of the rotational direction.
[0070]
As shown in FIG. 4, on each tooth surface 110, 112, a pair of non-contact areas are further set outside the respective contact areas.
[0071]
In the present embodiment, the tip 114 of each tooth 116 has a basic tip shape that is located on a cylindrical surface concentric with the helical gear 100 at the center of the tooth 116 in the width direction. On the other hand, it is missing. The missing position is set to a position that does not correspond to the contact area when rotating in any direction. That is, of the non-contact region of the tooth surface 110 and the non-contact region of the tooth surface 112, the region is set to a common region (a region that three-dimensionally overlaps each other) in the forward rotation and the reverse rotation.
[0072]
More specifically, in the present embodiment, the tooth tip 114 relates to a cross-sectional shape when the involute is cut by a plane including the rotation axis of the helical gear 100, and a radial direction at a central portion in a tooth width direction thereof. It is provided with a concave shape that is concave inward.
[0073]
Further, in the center of the tooth root 120 in the tooth width direction, the involute is raised with respect to the basic root shape located on a cylindrical surface concentric with the helical gear 100. The protruding portion is provided with a convex shape which protrudes outward in the radial direction at a central portion in the tooth width direction of the involute with respect to a cross-sectional shape when the involute is cut by a plane including the rotation axis of the helical gear 100. I have. The convex shape is selected so as to complement the concave shape.
[0074]
As described above, in the present embodiment, since the tooth bottom 120 has a portion raised from the basic root shape, the involute can easily improve the strength of each tooth in the helical gear 100.
[0075]
Further, in the present embodiment, since the tip 120 has a portion missing from the basic tip shape, the involute can easily reduce the rotational inertia of the helical gear 100.
[0076]
As described above, some of the embodiments of the present invention have been described in detail with reference to the drawings. However, these are exemplifications, and the embodiments described in the above-mentioned “Means for Solving the Problems and Effects of the Invention” will be described. As a result, it is possible to implement the present invention in other forms with various modifications and improvements based on the knowledge of those skilled in the art.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a main part of an involute spur gear 10 according to a first embodiment of the present invention.
FIG. 2 is a partial sectional front view of one tooth 12 of the involute spur gear 10 in FIG. 1 as viewed from a direction perpendicular to the axis.
FIG. 3 is a partial sectional front view of one tooth 66 of an involute helical gear 50 according to a second embodiment of the present invention as viewed from a direction perpendicular to an axis.
FIG. 4 is a partial cross-sectional front view of one tooth 116 of an involute helical gear 100 according to a third embodiment of the present invention viewed from a direction perpendicular to an axis.
[Explanation of symbols]
10 Involute spur gear 12, 66, 116 Tooth 20, 22, 60, 62, 110, 112 Tooth surface 30, 64, 114 Tooth tip 32, 70, 120 Root 50, 100 Involute helical gear

Claims (6)

A plurality of teeth each having a pair of front and rear tooth surfaces formed as an involute helicoid are formed side by side with a tooth groove having a tooth bottom being spaced one by one, and each tooth surface and the tooth surface of a mating gear contact each other. An involute gear in which a contact point that makes a locus on each tooth surface as the pair of gears engage and move,
The entire area of each tooth surface thereof is partitioned into a band-shaped contact area extending along the trajectory including the contact point and a non-contact area located outside the contact area,
The contact area is formed as an emvolute helicoid, and functions as a tooth contact surface with respect to the tooth surface of the mating gear,
The non-contact area is a shape that does not contact the tooth surface of the mating gear, and the strength of the teeth in the involute gear is directly or in comparison with the basic tooth surface shape when the entire area is formed as an involute helicoid. Involute gears given a modified shape to improve indirectly. The involute gear according to claim 1, wherein the changed shape is provided to both the tooth tip and the tooth bottom, and the shapes given to each other complement each other. The changed shape is changed in the radial direction of the involute gear with respect to the tooth tip and the root, respectively, with respect to the basic tooth tip shape and the basic tooth bottom shape located on the cylindrical surface concentric with the involute gear. 3. The involute gear according to claim 2, wherein the involute gear includes a set shape. The involute gear is a spur gear,
A trajectory of the contact point extends along a plane perpendicular to the axis of the spur gear;
The tip of each tooth is missing from the non-contact area, on both sides in the width direction of each tooth, with respect to the basic tip shape located on a cylindrical surface concentric with the spur gear,
The root in each tooth space is raised on a non-contact area, on both sides in the tooth width direction of each tooth space, with respect to a basic root shape located on a cylindrical surface concentric with the spur gear. An involute gear according to any one of claims 1 to 3. The involute gear is a helical gear,
The trajectory of the contact point extends in a direction intersecting the plane perpendicular to the axis of the helical gear,
The tip of each tooth is located on a cylindrical surface concentric with the helical gear on one side of the non-contact area, which is farther from the contact point trajectory, on both sides in the tooth width direction of each tooth. Is missing for the basic tooth tip shape
The tooth bottom in each tooth space is located on a cylindrical surface concentric with the helical gear on one side closer to the contact point locus among the two non-contact areas in the width direction of each tooth space. The involute gear according to any one of claims 1 to 3, which is raised with respect to the basic tooth bottom shape. The involute gear is a helical gear,
Of a pair of tooth surfaces of each tooth, a trajectory of a contact point drawn on a tooth surface meshing with the tooth surface of the counterpart gear during forward movement of the helical gear, and a tooth of the counterpart gear during reverse movement. The trajectory of the contact point drawn on the tooth surface which meshes with the surface, in a state where they intersect with each other in a three-dimensional manner, both extend in a direction intersecting the plane perpendicular to the axis of the helical gear,
The tip of each tooth is missing in the non-contact area, at the center in the face width direction of each tooth, with respect to the basic tip shape located on a cylindrical surface concentric with the helical gear. And
A root in each tooth space is raised from a basic root shape located on a cylindrical surface concentric with the helical gear at a central portion in a tooth width direction of each tooth groove in the non-contact area. The involute gear according to any one of claims 1 to 3, wherein the involute gear is provided.

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