CN107448580B

CN107448580B - Gear device, method for manufacturing involute gear, and method for manufacturing gear device

Info

Publication number: CN107448580B
Application number: CN201710368023.1A
Authority: CN
Inventors: 三好洋之
Original assignee: Nabtesco Corp
Current assignee: Nabtesco Corp
Priority date: 2016-05-30
Filing date: 2017-05-23
Publication date: 2022-02-18
Anticipated expiration: 2037-05-23
Also published as: KR20170135688A; JP6704296B2; CN107448580A; KR102390794B1; JP2017214941A

Abstract

The application discloses a gear device, a method for manufacturing an involute gear, and a method for manufacturing a gear device. The gear device includes a plurality of spur gears formed as involute gears, and an input gear that meshes with the plurality of spur gears and rotates the plurality of spur gears in synchronization. The plurality of spur gears respectively have tooth surfaces formed with grinding marks extending in a tooth profile direction.

Description

Gear device, method for manufacturing involute gear, and method for manufacturing gear device

Technical Field

The present invention relates to a gear device that reduces noise from the gear device, a method of manufacturing an involute gear, and a method of manufacturing a gear device.

Background

In various technical fields such as industrial robots, machine tools, and vehicles, various gear devices have been developed (see japanese patent laid-open publication No. 2015-21555). Japanese patent laid-open publication No. 2015-21555 discloses a gear device having a plurality of spur gears. The input gear is engaged with a plurality of spur gears, respectively, and rotates these gears in synchronization.

Since the input gear rotates at a higher speed than other portions, the meshing portion between the input gear and the plurality of spur gears is liable to generate a large noise. The use of a spur gear having a tooth surface formed with high accuracy is useful for reducing the above-described noise. However, complete conformity of the tooth surface shape among the plurality of spur gears is not realistic. For example, even if a manufacturer who manufactures a gear device selects 3 spur gears having the highest accuracy from a number of spur gears, there is a difference in tooth surface shape between the 3 spur gears. Further, the deviation of the rotation center of the spur gear meshed with the input gear from the rotation center determined in the design can also cause a large noise. In this case, the replacement of the spur gear does not contribute to the reduction of the noise level. Therefore, the conventional design technique or manufacturing technique cannot sufficiently reduce noise from the meshing portion between the input gear and the plurality of spur gears.

Disclosure of Invention

The invention aims to provide a technology for reducing noise generated from a meshing part between an input gear and a plurality of spur gears.

A gear device according to an aspect of the present invention includes: a plurality of spur gears formed as involute gears; and an input gear that meshes with the plurality of spur gears and rotates the plurality of spur gears in synchronization. The plurality of spur gears respectively have tooth surfaces formed with grinding marks extending in a tooth profile direction.

Another method for manufacturing an involute gear according to another aspect of the present invention includes: a step of driving a1 st involute gear and a2 nd involute gear engaged with the 1 st involute gear; and supplying free abrasive grains to a meshing portion between the 1 st involute gear and the 2 nd involute gear.

A method for manufacturing a gear device according to still another aspect of the present invention includes: a step of driving an input gear formed as an involute gear and meshed with a plurality of spur gears incorporated in a gear device; supplying free abrasive grains to an engagement portion between the input gear and the plurality of spur gears; and a step of grinding the meshed portion by rotating the input gear and the spur gear in a state where both gears are meshed with each other.

The above-described technique can reduce noise generated from the meshing portion between the input gear and the plurality of spur gears.

The objects, features and advantages of the above-described technology will become more apparent from the following detailed description and the accompanying drawings.

Drawings

Fig. 1 is a schematic front view of a gear device according to embodiment 1.

Fig. 2 is a schematic perspective view of external teeth of a spur gear or an input gear of the gear device shown in fig. 1.

FIG. 3 is an exemplary roughness curve obtained from the tooth flanks of the external teeth shown in FIG. 2.

FIG. 4 is an exemplary roughness curve obtained from the tooth flanks of the external teeth shown in FIG. 2.

Fig. 5 is a schematic cross-sectional view of the gear device according to embodiment 2.

Fig. 6 is a schematic sectional view taken along line a-a shown in fig. 5.

Fig. 7 is a conceptual diagram of the polishing apparatus according to embodiment 3.

Fig. 8 is a schematic front view of the gear device according to embodiment 4.

Detailed Description

< embodiment 1 >

The present inventors have developed a gear device capable of achieving a low noise level. In embodiment 1, an exemplary gear device capable of achieving a low noise level will be described.

Fig. 1 is a schematic front view of a gear device 100 according to embodiment 1. Referring to fig. 1, a gear assembly 100 is illustrated.

The gear device 100 includes 3

spur gears

111, 112, and 113 and an input gear 120.

Spur gears

111, 112, 113 are formed as involute gears, respectively. Likewise, the input gear 120 is also formed as an involute gear.

Fig. 1 shows the rotation axis RAX and the 3 transfer axes TX1, TX2, TX 3. The transmission axes TX1, TX2, and TX3 are arranged at substantially equal intervals on a phantom circle centered on the rotation axis RAX. The input gear 120 rotates about the rotation axis RAX. Spur gear 111 rotates about transfer axis TX 1. Spur gear 112 rotates about transfer axis TX 2. Spur gear 113 rotates about transfer axis TX 3.

The input gear 120 meshes with

spur gears

111, 112, 113. When the input gear 120 rotates around the rotation axis RAX, the

spur gears

111, 112, 113 rotate in synchronization.

Fig. 2 is a schematic perspective view of the external teeth 130. Referring to fig. 1 and 2, the gear assembly 100 is further illustrated. The description relating to the external teeth 130 applies to the teeth of each of the

spur gears

111, 112, 113. The description about the external teeth 130 may be applied to the teeth of the input gear 120.

In the following description, the term "tooth-form direction" refers to a direction extending from a tooth root to a tooth tip or a direction extending from a tooth tip to a tooth root. The term "tooth trace direction" refers to a direction perpendicular to the tooth profile direction.

The tooth surface of the external teeth 130 is formed with grinding marks extending in the tooth profile direction. The grinding traces may be formed by free abrasive grains supplied to the meshing portions between the

spur gears

111, 112, 113 and the input gear 120, or may be formed by other grinding techniques. The principle of the present embodiment is not limited to a specific polishing technique for forming polishing marks.

FIG. 3 shows an exemplary roughness profile obtained from the tooth flanks of external teeth 130. Referring to fig. 2 and 3, the surface roughness of the tooth flanks of the outer teeth 130 is explained.

The left graph of fig. 3 is data obtained from a stylus that traces the tooth flanks of the outer teeth 130 along the tooth profile direction. The right graph of fig. 3 is data obtained from a stylus that traces the tooth surface of the external teeth 130 in the tooth trace direction. Fig. 3 represents the maximum peak height obtained from the data of the left graph with the notation "Rp 1" and the maximum peak height obtained from the data of the right graph with the notation "Rp 2".

As for the left figure, as a result of the grinding treatment in the tooth profile direction, a portion constituting the peak of the roughness curve is chipped off, and therefore, the maximum peak height Rp1 becomes very small as compared with the maximum peak height Rp2 of the left figure. Thus, the level of noise generated due to the sliding between the tooth surface of the external teeth 130 and the tooth surfaces of the other gears becomes very small.

Fig. 4 shows the arithmetic mean roughness of the tooth flanks of the outer teeth 130. The arithmetic mean roughness of the tooth surface of the external teeth 130 is described with reference to fig. 2 to 4.

The data shown in fig. 4 is the same as the data shown in fig. 3. That is, the left diagram of fig. 4 is data obtained from a stylus that traces the tooth surface of the external teeth 130 in the tooth profile direction. The right graph of fig. 4 is data obtained from a stylus that traces the tooth surface of the external teeth 130 in the tooth trace direction. The solid line shown in fig. 4 represents the roughness curve on the peak side. The dotted line shown in fig. 4 indicates the roughness curve on the valley side.

Fig. 4 shows the arithmetic average roughness obtained from the data of the left diagram with the notation "Ra 1", and the arithmetic average roughness obtained from the data of the right diagram with the notation "Ra 2". As for the left figure, since the portion constituting the peak of the roughness curve is shaved off as a result of the polishing treatment in the tooth profile direction, the arithmetic average roughness Ra1 is smaller than the arithmetic average roughness Ra2 of the left figure. Thus, the level of noise generated due to the sliding between the tooth surface of the external teeth 130 and the tooth surfaces of the other gears becomes very small.

< embodiment 2 >

The gear device can have various internal configurations for synchronously rotating a plurality of spur gears. In embodiment 2, an exemplary structure of a gear device will be described.

Fig. 5 is a schematic cross-sectional view of the gear device 100 according to embodiment 2. Fig. 6 is a schematic sectional view taken along line a-a shown in fig. 5. Referring to fig. 1, 5, and 6, a gear device 100 will be described.

As described in connection with embodiment 1, the gear device 100 includes the input gear 120. The gear device 100 includes an outer cylinder 210, a carrier 220, 3 crankshaft assemblies 300, a gear portion 400, and two

main bearings

610 and 620. The 3 spur gears 111, 112, and 113 described in relation to embodiment 1 are respectively incorporated in the 3 crankshaft assemblies 300. Fig. 5 shows only the crankshaft assembly 300 in which the spur gear 111 is incorporated.

As described in connection with embodiment 1, the input gear 120 rotates about the rotation axis RAX and transmits the driving force to the 3 spur gears 111, 112, and 113. As a result, the 3 crankshaft assemblies 300 to which the spur gears 111, 112, 113 are respectively attached rotate about the transmission axes TX1, TX2, TX3, respectively. The rotation of the 3 crank assemblies 300 is transmitted to the gear portion 400 disposed in the internal space surrounded by the outer cylinder 210 and the carrier 220.

As shown in fig. 5, the two

main bearings

610 and 620 are fitted in an annular space formed between the outer cylinder 210 and the carrier 220 surrounded by the outer cylinder 210. The two

main bearings

610 and 620 are capable of relative rotational movement between the outer cylinder 210 and the carrier 220. The common central axis of the two

main bearings

610, 620 may also coincide with the rotational axis RAX of the input gear 120. One of the outer cylinder 210 and the carrier 220 rotates about the rotation axis RAX by the driving force transmitted to the gear portion 400. The other of the outer cylinder 210 and the gear holder 220 is fixed to a target member (not shown) to which the gear device 100 is attached.

As shown in fig. 5, the outer cylinder 210 includes a substantially cylindrical housing 211 and a plurality of inner gear pins 212. The housing 211 cooperates with the carrier 220 to form a cylindrical inner space for accommodating the crankshaft assembly 300 and the gear portion 400. The plurality of inner pins 212 are arranged in a ring shape along the inner circumferential surface of the housing 211 and form an inner ring gear.

Each of the plurality of inner pins 212 is a substantially columnar member extending in the extending direction of the rotation axis RAX. The plurality of inner pins 212 are fitted into groove portions formed in the inner peripheral surface of the housing 211. Thus, the plurality of inner pins 212 are properly held by the housing 211, respectively.

As shown in fig. 5, the plurality of inner-tooth pins 212 are arranged in a ring shape around the rotation axis RAX at substantially constant intervals. Each half circumferential surface of the plurality of inner pins 212 protrudes from the inner circumferential surface of the housing 211 toward the rotation axis RAX. Therefore, the plurality of internal gear pins 212 function as a plurality of internal teeth that mesh with the gear portion 400. In the present embodiment, the internal teeth are exemplified by a plurality of internal tooth pins 212, respectively.

As shown in fig. 5, the gear carrier 220 includes a base portion 230 and an end plate 240. The carrier 220 is cylindrical as a whole. The end plate 240 has a substantially circular plate shape. The peripheral surface of the end plate 240 is partially surrounded by the outer cylinder 210. The main bearing 620 is fitted into an annular gap formed between the outer cylinder 210 and the circumferential surface of the end plate 240.

The base portion 230 includes a substantially circular plate-shaped base plate portion 231 (see fig. 5) and 3 shaft portions 232 (see fig. 6). The circumferential surface of the substrate 231 is partially surrounded by the outer cylinder 210. The main bearing 610 is fitted into an annular gap formed between the outer cylinder 210 and the circumferential surface of the base plate 231. The base plate portion 231 is separated from the end plate 240 in the extending direction of the rotation axis RAX. The base plate 231 is substantially coaxial with the end plate 240. That is, the rotation axis RAX corresponds to the central axis of the substrate portion 231 and the end plate 240.

The substrate portion 231 includes an inner surface 233 and an outer surface 234 on the opposite side of the inner surface 233. The inner surface 233 is opposite to the gear portion 400. The inner surface 233 and the outer surface 234 are along an imaginary plane (not shown) orthogonal to the rotation axis RAX.

A central through-hole 235 (see fig. 5) and 3 holding through-holes 236 (fig. 5 shows 1 of the 3 holding through-holes 236) are formed in the substrate portion 231. The central through hole 235 extends along the rotation axis RAX between the inner surface 233 and the outer surface 234. The rotation axis RAX corresponds to the center axis of the central through hole 235. The central axes of the 3 holding through-holes 236 coincide with 3 transfer axes TX1, TX2, TX3 (fig. 5 shows only the transfer axis TX1) substantially parallel to the rotation axis RAX, respectively. The 3 retention through-holes 236 extend between the inner surface 233 and the outer surface 234 along 3 transfer axes TX1, TX2, TX 3. A part of the crankshaft assembly 300 is disposed in the holding through hole 236.

The end plate 240 includes an inner surface 243 and an outer surface 244 on the side opposite the inner surface 243. The inner surface 243 is opposite to the gear portion 400. The inner surface 243 and the outer surface 244 are along an imaginary plane (not shown) orthogonal to the rotation axis RAX.

A central through-hole 245 (see fig. 5) and 3 holding through-holes 246 (fig. 5 shows 1 of the 3 holding through-holes 246) are formed in the end plate 240. The central through hole 245 extends along the rotation axis RAX between the inner surface 243 and the outer surface 244. The rotation axis RAX corresponds to the center axis of the center through hole 245. The 3 retention through-holes 246 extend between the inner surface 243 and the outer surface 244 along 3 transfer axes TX1, TX2, TX3, respectively. The 3 transfer axes TX1, TX2, TX3 correspond to the central axes of the 3 holding through holes 246, respectively. A part of the crankshaft assembly 300 is disposed in the holding through hole 246. The 3 holding through-holes 246 formed in the end plate 240 are substantially coaxial with the 3 holding through-holes 236 formed in the substrate portion 231, respectively.

The 3 shaft portions 232 extend from the inner surface 233 of the base plate portion 231 toward the inner surface 243 of the end plate 240, respectively. The end plate 240 is connected to the tip end surface of each of the 3 shaft portions 232. The end plate 240 may be connected to the tip end surface of each of the 3 shaft portions 232 by a close-fit bolt, a positioning pin, or other appropriate fixing technique. The principle of the present embodiment is not limited to a specific connection technique between each of the end plates 240 and the 3 shaft portions 232.

As shown in fig. 5, the gear portion 400 is disposed between the inner surface 233 of the base plate portion 231 and the inner surface 243 of the end plate 240. The 3 shaft portions 232 penetrate the gear portion 400 and are connected to the end plate 240.

As shown in fig. 5, the gear portion 400 includes two

oscillating gears

410, 420. The swing gear 410 is disposed between the end plate 240 and the swing gear 420. The swing gear 420 is disposed between the substrate portion 231 and the swing gear 410. The oscillating gears 410 and 420 may be trochoid gears or cycloid gears formed based on a general design drawing.

The oscillating gears 410 and 420 each include a plurality of external teeth 430 (see fig. 6) protruding toward the inner wall of the housing 211. When the crankshaft assembly 300 rotates about the transmission axes TX1, TX2, and TX3, the oscillating gears 410 and 420 revolve (i.e., oscillate and rotate) in the housing 211 while engaging the plurality of external teeth 430 with the plurality of internal tooth pins 212. During this time, the centers of the oscillating gears 410, 420 revolve around the rotation axis RAX. The rotation of the outer tub 210 or the carrier 220 is caused by the oscillating rotation of the oscillating gears 410, 420.

The spur gears 111, 112, 113 are involute gears, and therefore, noise generated from the meshing portions between the spur gears 111, 112, 113 and the input gear 120 tends to be larger than noise generated from the meshing portions between the swing gears 410, 420 of the trochoid gears and the outer cylinder 210. Thus, the maximum peak height of the roughness curve extending in the tooth profile direction of the tooth surface of the

spur gear

111, 112, 113 is set to a value smaller than the maximum peak height of the roughness curve extending in the tooth profile direction of the tooth surface of the

wobble gear

410, 420.

As required, the oscillating gears 410 and 420 may have tooth surfaces on which grinding traces extending in the tooth profile direction are formed, as in the case of the spur gears 111, 112, and 113. In this case, noise generated from the meshing portions between the swing gears 410, 420 and the outer cylinder 210 is suppressed to a very low level. The grinding traces of the oscillating gears 410 and 420 may be formed of free abrasive grains or grinding films. The principle of the present embodiment is not limited to a specific grinding technique for forming grinding marks on the oscillating gears 410 and 420.

A central through-hole 411 is formed in the center of the swing gear 410. The central through hole 421 is formed in the center of the swing gear 420. The center through hole 411 communicates with the center through hole 245 of the end plate 240 and the center through hole 421 of the swing gear 420. The central through hole 421 communicates with the central through hole 235 of the substrate portion 231 and the central through hole 411 of the swing gear 410.

As shown in fig. 6, 3 circular through holes 422 are formed in the swing gear 420. Likewise, 3 circular through holes are formed in the swing gear 410. The circular through-holes 422 of the oscillating gear 420 and the circular through-holes of the oscillating gear 410 form a housing space for housing the crankshaft assembly 300 in cooperation with the holding through-

holes

236 and 246 of the base plate portion 231 and the end plate 240.

3 trapezoidal through holes 413 (fig. 5 shows 1 of the 3 trapezoidal through holes 413) are formed in the swing gear 410. 3 trapezoidal through holes 423 (see fig. 6) are formed in the swing gear 420. The shaft 232 of the carrier 220 passes through the trapezoidal through

holes

413 and 423. The trapezoidal through

holes

413 and 423 are sized so as not to interfere with the shaft portion 232.

The 3 crankshaft assemblies 300 include a crankshaft 320, two

journal bearings

331, 332, and two

crankshaft bearings

341, 342, respectively. The crankshaft 320 includes a1 st journal 321, a2 nd journal 322, a1 st eccentric portion 323, and a2 nd eccentric portion 324. The 1 st journal 321 is inserted into the holding through hole 246 of the end plate 240. The 2 nd journal 322 is inserted into the holding through hole 236 of the substrate portion 231. Journal bearing 331 is fitted into an annular space between 1 st journal 321 and the inner wall of end plate 240 where holding through hole 246 is formed. As a result, the 1 st journal 321 is coupled to the end plate 240. The journal bearing 332 is fitted into an annular space between the 2 nd journal 322 and the inner wall of the base plate portion 231 forming the holding through hole 236. As a result, the 2 nd journal 322 is coupled to the substrate portion 231. Thus, the carrier 220 can appropriately support the 3 crankshaft assemblies 300. As shown in fig. 1, the spur gears 111, 112, 113 are spline-coupled to the 1 st journal 321, respectively.

The 1 st eccentric portion 323 is located between the 1 st journal 321 and the 2 nd eccentric portion 324. The 2 nd eccentric portion 324 is located between the 2 nd journal 322 and the 1 st eccentric portion 323. The crank bearing 341 is fitted into an annular space between the 1 st eccentric portion 323 and an inner wall of the wobble gear 410 forming a circular through hole. As a result, the swing gear 410 is attached to the 1 st eccentric portion 323. The crank bearing 342 is fitted into an annular space between the 2 nd eccentric portion 324 and an inner wall of the wobble gear 420 forming the circular through hole 422. As a result, the swing gear 420 is attached to the 2 nd eccentric portion 324.

The 1 st journal 321 is substantially coaxial with the 2 nd journal 322 and rotates about the corresponding transfer axis (i.e., 1 of the transfer axes TX1, TX2, TX 3). The 1 st eccentric portion 323 and the 2 nd eccentric portion 324 are formed in a cylindrical shape, respectively, and are eccentric with respect to the corresponding transmission axes. The 1 st eccentric portion 323 and the 2 nd eccentric portion 324 eccentrically rotate with respect to the corresponding transmission axes, and impart a rocking rotation to the rocking gears 410 and 420. When the outer cylinder 210 is fixed, the oscillating rotation of the oscillating gears 410 and 420 is converted into the revolving motion of the crankshaft 320 about the rotation axis RAX. Since the end plate 240 and the base plate 231 are coupled to the 1 st journal 321 and the 2 nd journal 322, respectively, the revolving motion of the crankshaft 320 is converted into the rotational motion of the end plate 240 and the base plate 231 about the rotation axis RAX. The rotational phase difference between the oscillating gears 410 and 420 is determined by the difference in the eccentric direction between the 1 st eccentric portion 323 and the 2 nd eccentric portion 324. When the carrier 220 is fixed, the swing rotation of the swing gears 410 and 420 is converted into the rotational movement of the outer cylinder 210 about the rotation axis RAX.

< embodiment 3 >

The grinding traces extending in the tooth-shaped direction can also be formed by various methods. If the free abrasive grains are used for forming the grinding marks, the grinding marks are easily formed. In embodiment 3, an exemplary polishing technique for forming polishing marks extending in the tooth-shaped direction will be described.

Fig. 7 is a conceptual diagram of the polishing apparatus 140 according to embodiment 3. The grinding apparatus 140 is explained with reference to fig. 1 and 7.

Fig. 7 shows a1 st involute gear 150 in addition to the polishing device 140. Involute gear 1 is attached to grinding device 140. The polishing device 140 may include a member (not shown) that rotatably holds the 1 st involute gear 150. Involute gear 1 150 may also serve as input gear 120. Alternatively, the 1 st involute gear 150 may also be used as 1 of the spur gears 111, 112, 113.

The grinding device 140 includes a2 nd involute gear 160. Involute gear 2 may also be used as a special tool for grinding the tooth surfaces of involute gear 1 150. Alternatively, the 2 nd involute gear 160 may be detached from the grinding device 140 and used as 1 of the spur gears 111, 112, 113.

The milling device 140 further comprises a nozzle 141. The loose abrasive grains are blown out from the nozzle 141 and supplied to the meshing portion between the 1 st involute gear 150 and the 2 nd involute gear 160.

The worker who performs the grinding work attaches the 1 st involute gear 150 to the grinding device 140 and meshes it with the 2 nd involute gear 160. In order to properly mesh between involute gear 1 and involute gear 2 160, involute gear 1, 150 has a module that corresponds to the module of involute gear 2, 160.

Thereafter, the operator drives involute gear 2 to rotate involute gear 1 150 and involute gear 2 160. The operator ejects the free abrasive particles from the nozzle 141. As a result, the free abrasive grains are supplied to the meshing portion between the 1 st involute gear 150 and the 2 nd involute gear 160.

In the meshing portion between 1 st involute gear 150 and 2 nd involute gear 160, the tooth face of 1 st involute gear 150 is relatively moved in the tooth profile direction with respect to the tooth face of 2 nd involute gear 160. Free abrasive grains are interposed between the tooth surface of 1 st involute gear 150 and the tooth surface of 2 nd involute gear 160, and therefore, grinding marks extending in the tooth profile direction are efficiently formed on the tooth surfaces of 1 st involute gear 150 and 2 nd involute gear 160.

The free abrasive grains can efficiently grind the tooth surfaces of 1 st involute gear 150 and 2 nd involute gear 160 at a portion where the contact pressure between the tooth surface of 1 st involute gear 150 and the tooth surface of 2 nd involute gear 160 is high (i.e., the tooth surface area of 1 st involute gear 150 and 2 nd involute gear 160 corresponding to the pitch circle diameter).

As shown in fig. 7, 2 nd involute gear 160 has more teeth than 1 st involute gear 150. Thus, the 2 nd involute gear 160 is less likely to be worn than the 1 st involute gear 150. The operator can continue to use involute gear 2 for polishing other gears.

The number of teeth of 2 nd involute gear 160 may be a prime number. In this case, the frequency of contact between a specific tooth surface of the 1 st involute gear 150 and a specific tooth surface of the 2 nd involute gear 160 becomes very small. This means that 1 tooth face of 1 st involute gear 150 is rubbed against various tooth faces of 2 nd involute gear 160. Thus, the tooth surface shape of the 1 st involute gear 150 is uniformized over the entire tooth range of the 1 st involute gear 150.

Polishing device 140 may have a mechanism (e.g., a spring mechanism or a cylinder mechanism: not shown) for pressing 1 st involute gear 150 against 2 nd involute gear 160. In this case, the operator may press 1 st involute gear 150 against 2 nd involute gear 160 and drive 2 nd involute gear 160. As a result, the grinding traces formed on the 1 st involute gear 150 become longer in the tooth profile direction.

The tooth height of 2 nd involute gear 160 may be larger than the tooth height of 1 st involute gear 150. In this case, the grinding traces formed on the 1 st involute gear 150 also become longer in the tooth profile direction.

< embodiment 4 >

The grinding technique described in connection with embodiment 3 can be applied directly to a gear device. In embodiment 4, an exemplary polishing technique for simultaneously polishing the tooth surface of a spur gear incorporated in a gear device and the tooth surface of an input gear will be described.

Fig. 8 is a schematic front view of the gear device 100 subjected to the polishing process. The grinding process performed on the gear device 100 will be described with reference to fig. 8.

Fig. 8 shows the case 142. The operator who performs the polishing work covers the outer cylinder 210 with the housing 142, and isolates the outer cylinder 210 and the carrier 220 from the meshing portion between the spur gears 111, 112, 113 and the input gear 120. One of the outer tub 210 and the carrier 220 may also be fixed within the case 142.

After that, the operator drives the input gear 120. As a result, the spur gears 111, 112, 113 rotate together with the input gear 120. Similarly to embodiment 3, the worker supplies the loose abrasive grains to the meshing portions between the spur gears 111, 112, 113 and the input gear 120. As a result, grinding marks extending in the tooth profile direction are formed on the tooth surfaces of the spur gears 111, 112, 113 and the input gear 120, respectively.

Mounting errors and other manufacturing errors of the input gear 120 and the spur gears 111, 112, 113 are reflected in the lapping of the tooth surfaces of the spur gears 111, 112, 113 and the tooth surface of the input gear 120. Thus, the tooth surfaces of the spur gears 111, 112, 113 and the tooth surfaces of the input gear 120 automatically adapt to the inherent characteristics of the gear arrangement 100. For example, a portion where the contact pressure between the tooth surfaces is high is more ground by the free abrasive grains. On the other hand, the portion with a low contact pressure is not so much ground by the loose abrasive grains. As a result, a contact pressure close to the design value was obtained.

During the supply of the free abrasive grains, a gas such as air may be supplied into the box 142. The environment inside the tank 142 is maintained at a high pressure by the supplied gas. As a result, the outer cylinder 210, the gear holder 220, and an internal gear mechanism (not shown) are protected from the loose abrasive grains.

The design principles described in connection with the various embodiments described above can be applied to various gear devices. Some of the various features described in connection with 1 of the various embodiments described above may also be applied to a gear device described in connection with another embodiment.

The technique described in connection with the above-described embodiment mainly has the following features.

A gear device according to an aspect of the above embodiment includes: a plurality of spur gears formed as involute gears; and an input gear that meshes with the plurality of spur gears and rotates the plurality of spur gears in synchronization. The plurality of spur gears respectively have tooth surfaces formed with grinding marks extending in a tooth profile direction.

According to the above configuration, since each of the plurality of spur gears has a tooth surface on which a grinding mark extending in the tooth profile direction is formed, the direction of sliding between the tooth surface of each of the plurality of spur gears and the tooth surface of the input gear follows the grinding mark. Therefore, even if the tooth profiles of the plurality of spur gears do not completely match, or even if the rotational centers of the plurality of spur gears are shifted from the designed rotational center, a large noise is less likely to be generated from the meshing portion between the input gear and the plurality of spur gears.

In the above-described configuration, the input gear may have a tooth surface on which a grinding trace extending in a tooth profile direction is formed.

According to the above configuration, the input gear has the tooth surface on which the grinding traces extending in the tooth profile direction are formed, and therefore, the direction of sliding between the tooth surface of each of the plurality of spur gears and the tooth surface of the input gear follows the grinding traces formed on the input gear and the plurality of spur gears. Thus, a large noise is difficult to be generated from the meshing portion between the input gear and the plurality of spur gears.

In the above configuration, a maximum peak height of a roughness curve in the tooth profile direction of 1 of the plurality of spur gears may be smaller than a maximum peak height of a roughness curve in the tooth trace direction of the 1 of the plurality of spur gears.

According to the above-described structure, the maximum peak height of the roughness curve in the tooth profile direction of 1 of the plurality of spur gears is smaller than the maximum peak height of the roughness curve in the tooth trace direction of 1 of the plurality of spur gears, and therefore, noise generated during rubbing of the tooth surface of the spur gear with the tooth surface of the input gear is effectively reduced.

With the above-described configuration, an arithmetic average roughness obtained from a roughness curve in the tooth profile direction of 1 of the plurality of spur gears may be smaller than an arithmetic average roughness obtained from a roughness curve in the tooth trace direction of the 1 of the plurality of spur gears.

According to the above-described structure, the arithmetic average roughness obtained from the roughness curve in the tooth profile direction of 1 of the plurality of spur gears is smaller than the arithmetic average roughness obtained from the roughness curve in the tooth trace direction of 1 of the plurality of spur gears, and therefore, the noise generated during the rubbing of the tooth surface of the spur gear with the tooth surface of the input gear is effectively reduced.

In the above-described configuration, the grinding mark may not be formed on a tooth root portion of at least one of the input gear and the spur gear, more preferably both of the input gear and the spur gear, which portion is not in contact with the spur gear.

According to the above configuration, the target tooth does not come into contact with the tooth root portions of the plurality of spur gears which are not in contact with the input gear and/or the tooth root portions of the input gear which are not in contact with the spur gears, and therefore, even if grinding marks are not formed on the portions, a low noise level can be achieved.

With regard to the above configuration, the gear device may include: an outer cylinder having an inner circumferential surface on which a plurality of internal teeth are formed surrounding a predetermined rotation axis; a swing gear that meshes with the plurality of internal teeth; a plurality of crankshaft assemblies that are coupled to the plurality of spur gears, respectively, and that impart oscillating rotation to the oscillating gear so as to revolve the center of the oscillating gear around the rotation axis, based on the driving force input from the input gear; and a carrier that supports the plurality of crankshaft assemblies and rotates relative to the outer cylinder about the rotation axis. The oscillating gear may have a tooth surface on which a grinding trace extending in a tooth profile direction is formed.

According to the above configuration, since the oscillating gear has the tooth surface on which the grinding trace extending in the tooth profile direction is formed, the direction of sliding between the tooth surface of each of the plurality of internal teeth formed on the outer cylinder and the tooth surface of the oscillating gear is along the grinding trace formed on the oscillating gear. Thus, a large noise is difficult to be generated from the meshing portion between the oscillating gear and the plurality of internal teeth.

In the above configuration, a maximum peak height of the roughness curve in the tooth profile direction of 1 spur gear of the plurality of spur gears may be smaller than a maximum peak height of the roughness curve in the tooth profile direction of the wobble gear.

According to the above configuration, the maximum peak height of the roughness curve in the tooth profile direction of 1 spur gear out of the plurality of spur gears is smaller than the maximum peak height of the roughness curve in the tooth profile direction of the wobble gear, and therefore, large noise is less likely to be generated from the meshing portion between the input gear and the plurality of spur gears.

A method of manufacturing an involute gear according to another aspect of the above embodiment includes: a step of driving a1 st involute gear and a2 nd involute gear engaged with the 1 st involute gear; and supplying free abrasive grains to a meshing portion between the 1 st involute gear and the 2 nd involute gear.

According to the above configuration, since the free abrasive grains are supplied to the meshing portion between the 1 st involute gear and the 2 nd involute gear, the grinding traces extending in the tooth profile direction are formed on the tooth surface of the 1 st involute gear and the tooth surface of the 2 nd involute gear. Since the direction of sliding between the tooth surface of the 1 st involute gear or the tooth surface of the 2 nd involute gear and the tooth surface of the other gear is along the grinding trace formed on the tooth surface of the 1 st involute gear or the tooth surface of the 2 nd involute gear, a large noise is less likely to occur from the meshing portion between the 1 st involute gear or the 2 nd involute gear and the other gear.

In the above configuration, the 2 nd involute gear may have a number of teeth larger than a number of teeth of the 1 st involute gear.

According to the above configuration, since the 2 nd involute gear has a larger number of teeth than the 1 st involute gear, the 2 nd involute gear is less likely to be worn than the 1 st involute gear. Therefore, the 2 nd involute gear can be appropriately used as a grinding tool for grinding the tooth surface of the 1 st involute gear.

In the above configuration, the number of teeth of the 2 nd involute gear may be a prime number.

According to the above configuration, the number of teeth of the 2 nd involute gear is prime, and therefore, the teeth of the 1 st involute gear easily collide with teeth different from the 2 nd involute gear. As a result, the shape is made uniform among the plurality of teeth of the 1 st involute gear.

In the above configuration, the 2 nd involute gear may have a tooth height larger than a tooth height of the 1 st involute gear.

According to the above configuration, since the 2 nd involute gear has a tooth height larger than that of the 1 st involute gear, a sufficiently long grinding mark is formed on the tooth surface of the 1 st involute gear in the tooth profile direction.

In the above configuration, the step of driving the 1 st involute gear and the 2 nd involute gear may include a step of applying a force to press the 1 st involute gear against the 2 nd involute gear.

According to the above configuration, since the step of driving the 1 st involute gear and the 2 nd involute gear includes the step of applying a force to press the 1 st involute gear against the 2 nd involute gear, grinding marks sufficiently long in the tooth profile direction are formed on the tooth profile of the 1 st involute gear.

In the above configuration, the module of the 1 st involute gear may be equal to the module of the 2 nd involute gear.

According to the above configuration, the module of the 1 st involute gear is equal to the module of the 2 nd involute gear, and therefore, the 1 st involute gear can be appropriately meshed with the 2 nd involute gear.

A method of manufacturing a gear device according to still another aspect of the above embodiment includes: a step of driving an input gear formed as an involute gear and meshed with a plurality of spur gears incorporated in a gear device; supplying free abrasive grains to an engagement portion between the input gear and the plurality of spur gears; and a step of rotating both the gears in a state where the input gear is meshed with the spur gear to grind the meshed portion.

According to the above configuration, the input gear formed as an involute gear and meshed with the plurality of spur gears incorporated in the gear device is driven, and therefore, the free abrasive grains can automatically grind the tooth surfaces of the input gear and the plurality of spur gears, and noise from the meshed portion of the input gear and the plurality of spur gears can be reduced.

Industrial applicability

The principles of the above-described embodiments can be suitably applied to various gear devices.

Claims

1. A gear device is provided with:

a plurality of spur gears formed as involute gears; and

an input gear meshed with the plurality of spur gears and rotating the plurality of spur gears in synchronization,

the plurality of spur gears respectively have tooth surfaces formed with grinding traces extending in a tooth profile direction,

a maximum peak height of a roughness curve in the tooth profile direction of 1 of the plurality of spur gears is smaller than a maximum peak height of a roughness curve in the tooth trace direction of the 1 of the plurality of spur gears.

2. The gear device according to claim 1,

the input gear has a tooth surface formed with grinding marks extending in a tooth profile direction.

3. The gear device according to claim 1 or 2,

an arithmetic average roughness obtained from the roughness curve in the tooth profile direction of 1 spur gear of the plurality of spur gears is smaller than an arithmetic average roughness obtained from the roughness curve in the tooth trace direction of the 1 spur gear of the plurality of spur gears.

4. The gear device according to claim 1 or 2,

the grinding mark is not formed on a tooth root portion of at least one of the input gear and the spur gear, at which the input gear does not contact the spur gear.

5. The gear device according to claim 1 or 2,

the gear device is provided with:

an outer cylinder having an inner circumferential surface on which a plurality of internal teeth are formed surrounding a predetermined rotation axis;

a swing gear that meshes with the plurality of internal teeth;

a plurality of crankshaft assemblies that are coupled to the plurality of spur gears, respectively, and that impart oscillating rotation to the oscillating gear so as to revolve the center of the oscillating gear around the rotation axis, based on the driving force input from the input gear; and

a carrier that supports the plurality of crankshaft assemblies and rotates relative to the outer cylinder about the rotation axis,

the oscillating gear has a tooth surface formed with grinding marks extending in a tooth profile direction.

6. A gear device is provided with:

a plurality of spur gears formed as involute gears;

an input gear meshed with the plurality of spur gears and rotating the plurality of spur gears in synchronization;

a swing gear that meshes with the plurality of internal teeth;

the oscillating gear has a tooth surface formed with grinding marks extending in a tooth-shaped direction,

the maximum peak height of the roughness curve in the tooth profile direction of 1 spur gear of the plurality of spur gears is smaller than the maximum peak height of the roughness curve in the tooth profile direction of the wobble gear.

7. A method for manufacturing an involute gear, comprising:

a step of attaching a1 st involute gear to a polishing apparatus, and bringing the 1 st involute gear into engagement with a2 nd involute gear included in the polishing apparatus;

a step of driving a2 nd involute gear meshing with the 1 st involute gear to rotate the 1 st involute gear and the 2 nd involute gear; and

supplying free abrasive grains to a meshing portion between the 1 st involute gear and the 2 nd involute gear,

the number of teeth of the 2 nd involute gear is a prime number larger than the number of teeth of the 1 st involute gear, and the frequency of contact between a specific tooth surface of the 2 nd involute gear and a specific tooth surface of the 1 st involute gear is reduced in the step of rotating the 1 st involute gear and the 2 nd involute gear,

the maximum peak height of the roughness curve in the tooth profile direction of 1 involute gear in the 1 st involute gear and the 2 nd involute gear is smaller than the maximum peak height of the roughness curve in the tooth profile direction of 1 involute gear in the 1 st involute gear and the 2 nd involute gear.

8. The manufacturing method according to claim 7,

the 2 nd involute gear has a tooth height larger than that of the 1 st involute gear.

9. The manufacturing method according to claim 8,

the step of driving the 1 st involute gear and the 2 nd involute gear includes a step of applying a force to press the 1 st involute gear against the 2 nd involute gear.

10. A method of manufacturing a gear device, the gear device comprising:

a swing gear that meshes with the plurality of internal teeth;

a plurality of spur gears formed as involute gears;

a carrier that supports the plurality of crankshaft assemblies and relatively rotates with respect to the outer cylinder about the rotation axis, wherein,

the method for manufacturing the gear device comprises the following steps:

a step of isolating the outer cylinder and the carrier from the meshing portions between the plurality of spur gears and the input gear;

a step of driving an input gear formed as an involute gear and meshed with the plurality of spur gears; and

supplying free abrasive grains to an engagement portion between the input gear and the plurality of spur gears,

the input gear is driven to rotate the gears in a state where the input gear is meshed with the spur gear, thereby grinding the meshed portion,

the maximum peak height of the roughness curve in the tooth profile direction of 1 spur gear of the plurality of spur gears is smaller than the maximum peak height of the roughness curve in the tooth trace direction of the 1 spur gear of the plurality of spur gears.