Gear device

Abstract

To provide a gear device capable of suppressing failure in a gear caused by axial reaction force.SOLUTION: A gear device comprises a first gear, and a second gear that meshes with the first gear at a front meshing ratio of 1 or less. The teeth of the first gear and teeth 132T of the second gear have a twist angle. In a cross section of the teeth of the second gear, a first tooth surface S1 and a second tooth surface S2 have first end parts a1, a2 located on one side in a tooth trace direction, second end parts b1, b2 located on the other side in the tooth trace direction, and protrusion parts c1, c2 that protrude most in a tooth thickness direction between the first end parts a1, a2 and the second end parts b1, b2. The positions of the protrusion parts c1, c2 in the tooth trace direction, first differences Δa1, Δa2 which are the height differences between the protrusion parts c1, c2 and the first end parts a1, a2 in the tooth thickness direction, and second differences Δb1, Δb2 which are the height differences between the protrusion parts c1, c2 and the second end parts b1, b2 in the tooth thickness direction are different between the first tooth surface S1 and the second tooth surface S2.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a gear device.

Background Art

[0002] Citation Document 1 shows a gear device in which a plurality of gears having a twist angle are engaged with each other.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When torque is applied to a gear having a twist angle, an axial reaction force is generated in the gear. Further, when the number of teeth of the gear is reduced to increase the reduction ratio, the twist angle has to be increased accordingly, and the axial reaction force may increase. The axial reaction force affects the tooth contact of the gear.

[0005] An object of the present invention is to provide a gear device capable of suppressing defects of a gear caused by an axial reaction force.

Means for Solving the Problems

[0006] The gear device according to the present invention includes a first gear, a second gear that meshes with the first gear with a face contact ratio of 1 or less, and is provided with the tooth portion of the first gear and the tooth portion of the second gear have a twist angle, the tooth portion of the second gear has a first tooth surface facing the first rotation direction and a second tooth surface facing a direction opposite to the first rotation direction, In a cross section along the cylindrical surface centered on the rotation axis of the second gear, the first tooth surface and the second tooth surface have a first end portion located on one side in the tooth flank direction, a second end portion located on the other side in the tooth flank direction, and a protruding portion that protrudes most in the tooth thickness direction between the first end portion and the second end portion. At least one of the position of the protruding portion in the tooth flank direction, a first difference that is the difference in height in the tooth thickness direction between the protruding portion and the first end portion, and a second difference that is the difference in height in the tooth thickness direction between the protruding portion and the second end portion is different between the first tooth surface and the second tooth surface.

Advantages of the Invention

[0007] According to the present invention, it is possible to suppress defects of the second gear caused by axial reaction force.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0009] Hereinafter, each embodiment of the present invention will be described in detail with reference to the drawings.

[0010] (Embodiment 1) FIG. 1 is a cross-sectional view showing a gear device according to Embodiment 1 of the present invention.

[0011] The gear device 1 of Embodiment 1 includes a base 11 supported from the outside, a drive unit 12 that generates power, an input shaft 14 driven by the drive unit 12, a planetary gear mechanism 13 that decelerates the rotational motion of the input shaft 14, and an output shaft 15 to which the decelerated rotational motion is output.

[0012] The gear device 1 further includes a bearing 16 that rotatably supports the input shaft 14, and a bearing 17 that rotatably supports the output shaft 15 and the planetary carrier 133. The bearing 16 is provided between the base 11 and the input shaft 14, and the bearing 17 is provided between the output shaft 15 and the planetary carrier 133 and the base 11. The base 11 may be a casing member that covers the outside of the gear device 1.

[0013] The drive unit 12 is configured to be capable of forward drive and reverse drive. The drive unit 12 is, for example, an electric motor, but may be configured to drive the input shaft 14 using power other than electric power.

[0014] The planetary gear mechanism 13 includes a first gear (specifically, a sun gear) 131, a second gear (specifically, a planetary gear) 132, a planetary carrier 133 that supports the second gear 132, and an internal gear 134. The first gear 131 is integrated with the input shaft 14 and rotates integrally with the input shaft 14. Integration includes a configuration in which they are connected to each other and a configuration in which they are integrally formed with each other. The internal gear 134 is positioned along the circumferential direction centered on the first gear 131 and is integrated with the base 11. The second gear 132 is positioned between the first gear 131 and the internal gear 134 and meshes with the first gear 131 and the internal gear 134. The planetary carrier 133 rotatably supports the second gear 132 and is rotatably supported by the base 11. The planetary carrier 133 is integrated with the output shaft 15.

[0015] According to the gear device 1 configured as described above, when the input shaft 14 is rotationally driven by the drive unit 12, the first gear 131 rotates integrally with the input shaft 14, and this rotation is transmitted so that the second gear 132 rotates and revolves. Then, the revolution of the second gear 132 is transmitted to the planetary carrier 133, and the planetary carrier 133 and the output shaft 15 rotate. Thus, the rotational motion of the input shaft 14 is decelerated and output to the output shaft 15.

[0016] The first gear 131 and the second gear 132 are involute gears. Being an involute gear means that the cross-sectional shape orthogonal to the rotation axis of the tooth surface is an involute curve. However, in this specification, being an involute gear is not limited to a configuration where the cross-sectional shape of the tooth surface exactly matches the involute curve, and includes cases where an error is included between the cross-sectional shape of the tooth and the involute curve as long as the same or similar tooth meshing action can be obtained. The error is within the range of the calculation formula regarding the allowable value of the gear error defined in JIS B_1702―1:2016_6.3.

[0017] The first gear 131 and the second gear 132 mesh with a face contact ratio of 1 or less. The face contact ratio is defined in JIS (Japanese Industrial Standards) B_0102-1:2013_3.2.3.11. By adopting a configuration in which at least one of the number of teeth of the first gear and the second gear is small, the reduction ratio can be increased. At this time, if the number of teeth of at least one of the first gear and the second gear with a small number of teeth is reduced to further increase the reduction ratio, shaving and tooth tip sharpness become problems, and it is necessary to adjust the displacement coefficient and the tooth tip height to avoid them. As a result, the total tooth height becomes shorter, that is, the meshing range becomes shorter, so the face contact ratio becomes less than 1.

[0018] The number of teeth of the first gear 131 may be 2 or more and 6 or less. By using such a small number of teeth gear, the reduction ratio can be made larger. Therefore, while suppressing the increase in size of the gear device 1, the reduction ratio of the gear device 1 can be increased. The number of teeth of the first gear 131 may be 10 or less, or may be 12 or less. As the number of teeth increases, the reduction ratio decreases, but a sufficiently large reduction ratio can also be obtained with such a number of teeth.

[0019] Each tooth portion of the first gear 131, the second gear 132, and the internal gear 134 has a helix angle. In FIG. 1, the helix angle of the tooth portion of the first gear 131 is represented by a two-dot chain line on the first gear 131. In FIG. 1, the helix angle of the tooth portion of the second gear 132 is represented by a two-dot chain line on the second gear 132. By having a helix angle, the contact ratio can be made larger than the face contact ratio, and an appropriate contact ratio can be ensured. In particular, in the first gear 131 and the second gear 132 where the face contact ratio is 1 or less, the contact ratio can be set to an appropriate value of 1 or more.

[0020] When the first gear 131 with a small number of teeth is adopted and the face contact ratio becomes a small value of 1 or less, a large helix angle is adopted in order to obtain an appropriate contact ratio. As the helix angle increases, a relatively large axial reaction force is generated in the first gear 131 and the second gear 132.

[0021] During the operation of the gear device 1, if the driving unit 12 outputs torque in the forward rotation direction, torque in the rotation direction A1 is output from the output shaft 15. If the driving unit 12 outputs torque in the reverse rotation direction, torque in the direction opposite to the rotation direction A1 is output from the output shaft 15. Further, during the operation of the gear device 1, when the output shaft 15 rotates in the rotation direction A1 and receives torque in the direction opposite to the rotation direction A1 from the driven member, the torque is transmitted to the planetary carrier 133 and the second gear 132, and the input shaft 14 receives torque in the reverse rotation direction while rotating forward. Also, during the operation of the gear device 1, when the output shaft 15 rotates in the direction opposite to the rotation direction A1 and receives torque in the rotation direction A1 from the driven member, the torque is transmitted to the planetary carrier 133 and the second gear 132, and the input shaft 14 receives torque in the forward rotation direction while rotating in reverse.

[0022] As described above, when the direction of the torque applied to the first gear 131 and the second gear 132 changes, the direction of the axial reaction force generated in the first gear 131 and the second gear 132 also reverses.

[0023] <Action by Axial Reaction Force> In the gear device 1, the axial reaction forces generated in the plurality of gears act relatively greatly on the second gear 132, which is a planetary gear, generating a moment M1 in the second gear 132 and causing distortion in the second gear 132 or its support portion. The moment M1 is caused by the first axial reaction force generated at the tooth contact portion between the first gear 131 and the second gear 132 and the second axial reaction force generated at the tooth contact portion between the second gear 132 and the internal gear 134. The first axial reaction force and the second axial reaction force are in opposite directions to each other. The distortion of the second gear 132 or its support portion due to the moment M1 becomes a cause of the problem of one-sided contact of the tooth surface at the meshing portion between the first gear 131 and the second gear 132.

[0024] Furthermore, depending on the direction of the torque applied to the first gear 131 and the second gear 132, the moment M1 becomes reverse. And when a clockwise moment M1 occurs in FIG. 1 and when a counterclockwise moment M1 occurs, the direction of the strain generated in the second gear 132 and its support portion changes. Furthermore, due to this change, at the meshing portion between the first gear 131 and the second gear 132, the side where the tooth portions approach each other and the side where they move away from each other due to the above strain are opposite between the first end portion a side and the second end portion b side.

[0025] The gear device 1 of Embodiment 1 suppresses the occurrence of single-sided contact on the tooth surface due to such strain related to the second gear 132 by the tooth surface shape shown below.

[0026] <Tooth surface shape> FIG. 2 is a cross-sectional view for explaining the shape of the tooth portion 132T of the second gear 132. FIG. 2 omits the cross-sectional hatching to avoid complexity. FIG. 2 shows a cross-section along the cylindrical surface centered on the rotation axis of the second gear 132. In FIG. 2, mainly the dimensions in the tooth thickness direction are enlarged for easy understanding. The radial height of the above cross-section is any height within the range where tooth contact occurs between the first gear 131 and the second gear 132. The shape of the tooth surface may have the shape shown in FIG. 2 at any position within the height range where tooth contact occurs.

[0027] The center line L0 in FIG. 2 is a straight line along the tooth rib of the tooth portion 132T and is also a straight line located in the middle between the first tooth surface S1 and the second tooth surface S2. The tooth rib is a line where the tooth surface and the tooth bottom surface intersect. In this specification, the direction along the center line L0 is defined as the tooth rib direction, and the direction orthogonal to the center line L0 in the above cross-section is defined as the tooth thickness direction.

[0028] The first tooth surface S1 is the tooth surface facing the first rotation direction R1, and the second tooth surface S2 is the tooth surface facing the second rotation direction R2 opposite to the first rotation direction R1.

[0029] The first tooth surface S1 and the second tooth surface S2 each have first ends a1, a2 located on one side in the tooth flanks direction, second ends b1, b2 located on the other side in the tooth flanks direction, and protruding portions c1, c2 that protrude most in the tooth thickness direction in the above cross section. The first tooth surface S1 has a curved surface shape that is high at the protruding portion c1 in the tooth thickness direction, gradually decreases from the protruding portion c1 to the first end a1, and gradually decreases from the protruding portion c1 to the second end b1. The second tooth surface S2 has a curved surface shape that is high at the protruding portion c2 in the tooth thickness direction, gradually decreases from the protruding portion c2 to the first end a2, and gradually decreases from the protruding portion c2 to the second end b2. These shapes may be realized by crowning machining.

[0030] Chamfers d1 to d4 may be provided at the ends of the tooth portion 132T in the tooth flanks direction. In this specification, the chamfers d1 to d4 are not included in the tooth surfaces. The chamfers d1 to d4 are for the purpose of removing burrs and preventing indentation scratches, and are clearly distinguished from the first tooth surface S1 and the second tooth surface S2. The order of the chamfer amount is on the order of 0.1 to several millimeters, and the tooth surface finishing is on the order of several micrometers to several tens of micrometers.

[0031] <Feature 1 of tooth surface shape> In the tooth portion 132T of the second gear 132, the positions of the protruding portions c1, c2 in the tooth flanks direction are different between the first tooth surface S1 and the second tooth surface S2. Further, the first differences Δa1, Δa2 in height in the tooth thickness direction between the first ends a1, a2 and the protruding portions c1, c2 are different between the first tooth surface S1 and the second tooth surface S2. Further, the second differences Δb1, Δb2 in height in the tooth thickness direction between the second ends b1, b2 and the protruding portions c1, c2 are different between the first tooth surface S1 and the second tooth surface S2. Note that not all of the positions of the protruding portions c1, c2, the first differences Δa1, Δa2 in height, and the second differences Δb1, Δb2 in height need to be different, and they may have a shape where any one or two of them are different.

[0032] As described above, in the gear device 1, when surface pressure is applied to the first tooth surface S1 and when surface pressure is applied to the second tooth surface S2, the direction of the moment M1 (see FIG. 1) generated in the second gear 132 is reversed, and the mode of strain related to the second gear 132 caused by the moment M1 changes. Then, due to this change, at the meshing portion between the first gear 131 and the second gear 132, the side where the tooth portions approach each other and the side where they move away from each other due to the above strain are reversed between the first end portion a side and the second end portion b side. Therefore, the shape of the first tooth surface S1 that suppresses the contact of the tooth surfaces due to strain does not match the shape of the second tooth surface S2.

[0033] In Embodiment 1, due to the above-described Feature 1 of the tooth surface shape, it is possible to suppress the contact of the tooth surfaces both when surface pressure is applied to the first tooth surface S1 and when surface pressure is applied to the second tooth surface S2 in response to the strain related to the second gear 132 that changes as described above.

[0034] The position of the protruding portion c1 of the first tooth surface S1 in the tooth trace direction, and the first difference Δa1 and the second difference Δb1 in the tooth thickness direction at both ends may adopt appropriate positions and difference amounts according to the assumed surface pressure of the first tooth surface S1 and the magnitude of the moment M1. The position of the protruding portion c2 of the second tooth surface S2 in the tooth trace direction, and the first difference Δa2 and the second difference Δb2 in the tooth thickness direction at both ends may adopt appropriate positions and difference amounts according to the assumed surface pressure of the second tooth surface S2 and the magnitude of the moment M2.

[0035] <Feature 2 of the tooth surface shape> In the tooth portion 132T of the present embodiment, further, the protruding portion c1 of the first tooth surface S1 is located closer to the first end portion a1 than the second end portion b1, and conversely, the protruding portion c2 of the second tooth surface S2 is located closer to the second end portion b2 than the first end portion a2. That is, which of the first end portions a1, a2 and the second end portions b1, b2 the protruding portions c1, c2 are closer to is reversed between the first tooth surface S1 and the second tooth surface S2.

[0036] Furthermore, when comparing the first difference Δa1 and the second difference Δb1 at both ends of the first tooth surface S1, the second difference Δb1 is larger. On the other hand, when comparing the first difference Δa2 and the second difference Δb2 at both ends of the second tooth surface S2, the first difference Δa2 is larger. That is, when comparing the first differences Δa1, Δa2 and the second differences Δb1, Δb2 in the height direction of the tooth thickness at both ends, whether the first ends a1, a2 side is larger or the second ends b1, b2 side is larger is reversed between the first tooth surface S1 and the second tooth surface S2.

[0037] Due to the shape of the tooth portion 132T like this, when surface pressure is applied to the first tooth surface S1 and when surface pressure is applied to the second tooth surface S2, in the case where the direction of strain regarding the second gear 132 reverses between the first ends a1, a2 side and the second ends b1, b2 side, it is possible to cope well. That is, with respect to the strain regarding the second gear 132 as described above, it is possible to suppress both the contact on the first tooth surface S1 and the contact on the second tooth surface S2.

[0038] Note that the tooth portion 132T may have only either one of the above-mentioned feature 2 regarding the positions of the protruding portions c1, c2 and the above-mentioned feature 2 regarding the magnitude relationship between the first differences Δa1, Δa2 and the second differences Δb1, Δb2. Even if it has only one of the features, the tooth contact can be improved on both the first tooth surface S1 and the second tooth surface S2 with respect to the strain regarding the second gear 132 as described above.

[0039] <Characteristic 3 of tooth surface shape> In the tooth portion 132T of the present embodiment, furthermore, the positions of the protruding portions c1, c2 in the tooth flanks direction are different between the first tooth surface S1 and the second tooth surface S2, and the distance L1 from the first end a1 of the first tooth surface S1 to the protruding portion c1 in the tooth flanks direction and the distance L2 from the second end b2 of the second tooth surface S2 to the protruding portion c2 in the tooth flanks direction are the same. In this specification, being the same includes not only an exact match but also a mode of matching within a range with an allowable error added. The allowable error is within the range of the calculation formula regarding the allowable value of the error of the gear defined in JIS B_1702―1:2016_6.3.

[0040] In the tooth portion 132T of the present embodiment, further, in the above cross-section, it has the characteristic that when the first tooth surface S1 is rotated 180 degrees, it overlaps with the second tooth surface S2. In this specification, "overlap" includes not only the mode of exact overlap without error, but also the mode of overlap within the range in which an allowable error is added in the tooth thickness direction. The allowable error is within the range of the calculation formula regarding the allowable value of the error of the gear defined in JIS B_1702―1:2016_6.3.

[0041] Due to the shape of the tooth portion 132T like this, when surface pressure is applied to the first tooth surface S1 and when surface pressure is applied to the second tooth surface S2, the direction of the strain regarding the second gear 132 is reversed between the first end portions a1, a2 side and the second end portions b1, b2 side, and when these strain amounts are equal, it can cope well. That is, with respect to the strain of the second gear 132 as described above, both the contact on the first tooth surface S1 and the contact on the second tooth surface S2 can be suppressed.

[0042] <Method of forming tooth surface> FIG. 3 is an explanatory diagram showing an example of the grinding process of the tooth surface of the second gear 132. The shapes of the first tooth surface S1 and the second tooth surface S2 of the tooth portion 132T can be formed by a grinding process using a tooth cutting tool 41. The tooth cutting tool 41 grinds the work surface by bringing it into contact with the work surface while rotating, for example, a rod-shaped grindstone. Alternatively, the tooth cutting tool 41 may be configured to grind the work surface by bringing the polishing surface provided on one side surface S41a and the other side surface S41b into contact with the work surface and vibrating it.

[0043] In the tooth surface grinding process, the gear cutting tool 41 grinds the first tooth surface S1 of one tooth part 132T and the second tooth surface S2 of the other tooth part 132T between two adjacent tooth parts 132T of the second gear 132. At this time, the gear cutting tool 41 can simultaneously contact the first tooth surface S1 and the second tooth surface S2, or alternately contact them by translating, without changing the relative angle with the second gear 132 or changing the relative angle greatly, to grind the first tooth surface S1 and the second tooth surface S2. By such a grinding method, when grinding is performed closer to the first end a1 of the first tooth surface S1, grinding similar to the said grinding can be performed closer to the second end b2 of the second tooth surface S2. Conversely, when grinding is performed closer to the second end b1 of the first tooth surface S1, grinding similar to the said grinding can be performed closer to the first end a2 of the second tooth surface S2.

[0044] Therefore, since the second gear 132 has the above-described tooth surface shape features 2 and 3, by applying the above-described grinding process, the first tooth surface S1 and the second tooth surface S2 can be efficiently formed. That is, without changing the posture of the gear cutting tool 41 (the relative posture with respect to the second gear 132) much, grinding of the first tooth surface S1 and the second tooth surface S2 of two adjacent tooth parts 132T can be realized.

[0045] (Embodiment 2) FIG. 4 is a cross-sectional view showing the gear device 2 according to Embodiment 2 of the present invention. FIG. 5 is a side view showing the gear device 2 according to Embodiment 2. FIG. 4 shows a cross-section along the cutting line e of FIG. 5.

[0046] The gear device 2 of Embodiment 2 includes a drive unit 21, a first bevel gear 22 provided on the rotation shaft 21a of the drive unit 21, a parallel shaft reduction mechanism 24 that decelerates and transmits the rotational movement of the first bevel gear 22, an output shaft 26 that outputs the rotational movement transmitted by the parallel shaft reduction mechanism 24 to the outside, and a casing member 27 that surrounds the parallel shaft reduction mechanism 24 and the output shaft 26. The rotation center axis of the drive unit 21 and the rotation center axis of the output shaft 26 are orthogonal or in a position where the axes are twisted, and when viewed from the direction passing through each axis, the axes form a relationship of 90 degrees with each other.

[0047] The parallel-axis reduction mechanism 24 includes a first rotating shaft 241, a second rotating shaft 242, and a third rotating shaft 243 whose rotation center axes are parallel to each other, and a plurality of gears fixed to these rotating shafts.

[0048] In a plan view, the first rotating shaft 241, the second rotating shaft 242, and the third rotating shaft 243 are arranged in this order in a direction orthogonal to the rotating shafts. The first rotating shaft 241 to the third rotating shaft 243 and the output shaft 26 are rotatably supported by the casing member 27 via bearings 28a to 31a, 28b to 31b, respectively.

[0049] The plurality of gears includes a second bevel gear 246 and a first gear 251 fixed to the first rotating shaft 241, a second gear 252 and a third gear 253 fixed to the second rotating shaft 242, a fourth gear 254 and a fifth gear 255 fixed to the third rotating shaft 243, and a sixth gear 256 fixed to the output shaft 26.

[0050] Among the plurality of gears, the first bevel gear 22 meshes with the second bevel gear 246, the first gear 251 meshes with the second gear 252, the third gear 253 meshes with the fourth gear 254, and the fifth gear 255 meshes with the sixth gear 256.

[0051] The first gear 251 and the second gear 252 are helical gears, and the first gear 251 and the second gear 252 have a helix angle. The third gear 253 to the sixth gear 256 are spur gears. The number of teeth of each of the first gear 251 to the sixth gear 256 is set so that the rotational motion is gradually decelerated.

[0052] The drive unit 21 is configured to be capable of forward drive and reverse drive. The drive unit 21 is, for example, an electric motor, but may be configured to drive the rotating shaft 21a using power other than electric power.

[0053] With the above configuration, when the rotary shaft 21a is rotationally driven by the drive unit 21, the first bevel gear 22 rotates integrally with the rotary shaft 21a, and this rotation is transmitted to the second bevel gear 246 and the first to sixth gears 251 to 256, causing the output shaft 26 to rotate. As a result, the rotational motion of the drive unit 21 is decelerated and output to the output shaft 26.

[0054] The first gear 251 and the second gear 252 are involute gears. The first gear 251 and the second gear 252 mesh with a face contact ratio of 1 or less. The number of teeth of the first gear 251 may be 2 or more and 6 or less. By using such a small number of teeth gear, the reduction ratio can be made larger. The number of teeth of the first gear 251 may be 10 or less, or may be 12 or less. As the number of teeth increases, the reduction ratio decreases, but a sufficiently large reduction ratio can still be obtained with such a number of teeth.

[0055] Each tooth portion of the first gear 251 and the second gear 252 has a twist angle. In FIG. 4, the twist angle of the tooth portion of the first gear 251 is represented by a two-dot chain line on the first gear 251. In FIG. 4, the twist angle of the tooth portion of the second gear 252 is represented by a two-dot chain line on the second gear 252. By having a twist angle, in the first gear 251 and the second gear 252 with a face contact ratio of 1 or less, the contact ratio can be set to an appropriate value of 1 or more.

[0056] Also in the gear device 2 of Embodiment 2, when torque is applied to the first gear 251 and the second gear 252, an axial reaction force is generated in the first gear 251 and the second gear 252. The axial reaction force generates a moment M2 in the second gear 252, causing distortion in the second gear 252 or its support portion. This distortion becomes a cause of a problem of tooth surface single contact at the meshing portion between the first gear 251 and the second gear 252.

[0057] Furthermore, the direction of moment M2 changes depending on the direction of the torque applied to the first gear 251 and the second gear 252. Then, when a clockwise moment M2 occurs in FIG. 4 and when a counterclockwise moment M2 occurs, the direction of the strain generated in the second gear 252 and its support portion changes. Furthermore, due to this change, at the meshing portion between the first gear 251 and the second gear 252, the side where the tooth portions approach each other and the side where they move away from each other due to the above strain are opposite between the first end portion a side and the second end portion b side.

[0058] In the gear device 2 of Embodiment 2, the tooth surface shape of the tooth portion 252T of the second gear 252 has the same tooth surface shape as the tooth portion 132T of the second gear 132 of Embodiment 1. Due to such a shape of the tooth portion 252T, the same effects as those of Embodiment 1 can be obtained also in Embodiment 2. That is, in both cases when surface pressure is applied to the first tooth surface S1 and when surface pressure is applied to the second tooth surface S2, corresponding to the strain related to the second gear 252, both the single contact on the first tooth surface S1 and the single contact on the second tooth surface S2 can be suppressed. Furthermore, in the grinding process of the tooth surface of the second gear 132, the first tooth surface S1 and the second tooth surface S2 can be efficiently formed.

[0059] The above describes each embodiment of the present invention. However, the present invention is not limited to the above embodiments. For example, in the above embodiments, the drive units 12 and 21 are shown to be capable of forward and reverse driving. However, the drive units 12 and 21 may be configured to be capable of only one-way driving. Also, in the above embodiments, the tooth portion of the second gear is shown to have all of Features 1 to 3. However, a configuration having Feature 1 and not having Features 2 and 3, or a configuration having Features 1 and 2 and not having Feature 3 may also be acceptable.

[0060] In the above-described Embodiment 1, in the first gear 131 which is a sun gear and the second gear 132 which is a planetary gear, the number of teeth of the first gear 131 is small, and the shape of the tooth portion of the second gear 132 has Features 1 to 3. However, the shape of the tooth portion of the sun gear with a small number of teeth may have Features 1 to 3. In this case, the sun gear may be regarded as the second gear according to the present invention, and the planetary gear may be regarded as the first gear according to the present invention.

[0061] Similarly, in the above-described Embodiment 2, among the first gear 251 with a small number of teeth and the second gear 252, the shape of the tooth portion of the second gear 252 has Features 1 to 3. However, the shape of the tooth portion of the gear (251) with a small number of teeth may have Features 1 to 3. In this case, the gear (251) with a smaller number of teeth may be regarded as the second gear according to the present invention, and the other gear (252) may be regarded as the first gear according to the present invention.

[0062] In the above-described embodiments, the gear devices 1 and 2 are configured to include drive units 12 and 21. However, the gear device according to the present invention may be configured not to have a drive unit and to have a driving force introduced from the outside. Further, the gear device according to the present invention may be applied to drive units of escalators, belt conveyors, etc. In addition, the details shown in the embodiments can be appropriately changed without departing from the gist of the invention.

Explanation of Reference Numerals

[0063] 1, 2 Gear device 11 Base 12, 21 Drive unit 13 Planetary gear mechanism 131 First gear 132 Second gear 132T Tooth portion 133 Planetary carrier 134 Internal gear 14 Input shaft 15, 26 Output shaft 16, 17 Bearing 22 First bevel gear 24 Parallel shaft reduction mechanism 28a~31a, 28b~31b Bearing 241 First rotating shaft 242 Second rotating shaft 243 Third rotating shaft 246 Second bevel gear 251 First gear 252 Second gear 252T Tooth part 253 - 256 Third gear - Sixth gear 27 Casing member 41 Tooth cutting tool S1 First tooth surface S2 Second tooth surface a, a1, a2 First end b, b1, b2 Second end c1, c2 Protrusion d1 - d4 Chamfer L0 Center line M1, M2 Moment Δa1, Δa2 First difference Δb1, Δb2 Second difference L1, L2 Distance

Claims

1. a first gear, a second gear that meshes with the first gear with a face engagement ratio of 1 or less, and comprising the tooth portion of the first gear and the tooth portion of the second gear have a twist angle, the tooth portion of the second gear has a first tooth surface facing a first rotation direction and a second tooth surface facing a direction opposite to the first rotation direction, in a cross section along a cylindrical surface centered on the rotation axis of the second gear, the first tooth surface and the second tooth surface have a first end portion located on one side in the tooth flank direction, a second end portion located on the other side in the tooth flank direction, and a protruding portion that protrudes most in the tooth thickness direction between the first end portion and the second end portion, at least one of the position of the protruding portion in the tooth flank direction, a first difference that is the difference in height in the tooth thickness direction between the protruding portion and the first end portion, and a second difference that is the difference in height in the tooth thickness direction between the protruding portion and the second end portion is different between the first tooth surface and the second tooth surface, a gear device.

2. Whether the protruding portion is closer to the first end portion or the second end portion, or which of the first difference and the second difference is larger is reversed between the first tooth surface and the second tooth surface, The gear device according to Claim 1.

3. the position of the protruding portion in the tooth flank direction is different between the first tooth surface and the second tooth surface, the distance from the first end portion to the protruding portion of the first tooth surface in the tooth flank direction and the distance from the second end portion to the protruding portion of the second tooth surface in the tooth flank direction are the same, The gear device according to Claim 2.

4. when the first tooth surface is rotated 180 degrees in the cross section, it overlaps with the second tooth surface, The gear device according to Claim 2.

5. the gear device comprises a driving portion that rotationally drives the first gear and the second gear, the driving portion is capable of forward rotation driving and reverse rotation driving, The gear device according to Claim 1.

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