Device and method for polishing gear

Abstract

To provide a device and a method for polishing a gear, which can reduce material cost and polishing cost of a polishing gear and solving the problem of a resource environment.SOLUTION: A polishing device 1 for rotary-driving a polishing gear to polish the tooth surface of a polished gear in a state where the polishing gear 8 and the polished gear 9 are engaged with each other is configured such that a coating layer 10 in which a film thickness α of an acrylic resin material is about 20 μm is formed on the tooth surface 8a of the polishing gear, a polishing liquid containing silicon carbide abrasives smaller in average grain diameter than the film thickness of the coating layer of the polishing gear is supplied to the engaging place of the polishing gear and the polished gear, and the polishing gear is rotary-driven to polish the tooth surface 9a of the polished gear.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an improved gear grinding apparatus and grinding method. [Background technology]

[0002] A known conventional gear grinding device is, for example, that described in Patent Document 1 below.

[0003] This gear polishing device uses a lapping method, in which a lapping gear (gear to be polished) and a workpiece gear (gear to be polished) are meshed with each other with a lapping agent interposed between them, and the workpiece gear is rotated around a drive shaft while moving back and forth in the axial direction of the drive shaft. This creates relative motion between the lapping gear and the workpiece gear, resulting in a smooth finish to the tooth surface of the workpiece gear.

[0004] The polishing device also includes a vibration generating means for vibrating the wrap gear in the axial direction of the driven shaft at a predetermined frequency, and the wrap gear is vibrated in the axial direction of the driven shaft at the predetermined frequency by the excitation force from the vibration generating means. As a result, different tooth flanks of the wrap gear and the work gear always come into contact with each other, ensuring uniform lapping across the entire tooth profile of the work gear. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-343328 Summary of the Invention [Problem to be solved by the invention]

[0006] In the conventional gear grinding device described in Patent Document 1, the wrap gear is integrally formed from monomer cast nylon (MC nylon), which has excellent mechanical properties such as tensile strength and bending strength. Therefore, when the tooth surface of the wrap gear wears after long-term use, it is replaced with a new one and reused. In other words, whenever a wrap gear becomes unusable due to wear, it is replaced with a new one. This leads to rising material and processing costs and may also cause environmental problems.

[0007] The present invention was devised in consideration of the technical problems inherent in conventional gear polishing devices, and one of its objects is to provide a gear polishing device and method that can reduce material costs and polishing processing costs and eliminate resource and environmental issues. [Means for solving the problem]

[0008] One aspect of the present invention is characterized in that a coating layer of a resin material or soft metal is formed on the tooth surface of a gear to be polished, a polishing liquid containing abrasive grains with an average particle size smaller than the film thickness of the coating layer of the gear to be polished is supplied to the meshing point between the gear to be polished and the gear to be polished, and the gear to be polished is rotated to polish the tooth surface of the gear to be polished. [Effects of the Invention]

[0009] According to an embodiment of the present invention, when the coating layer on the tooth surface of the grinding gear becomes worn, the tooth surface can be re-coated and the same grinding gear can be used again. This reduces the material costs and grinding processing costs of the grinding gear and eliminates resource and environmental issues. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a side view showing a gear grinding device according to an embodiment of the present invention. FIG. [Figure 2]FIG. 1(a) is a side view showing a state in which a gear to be ground and a gear to be ground are engaged in the gear grinding device of the present embodiment, and FIG. 1(b) is an enlarged view of part A in FIG. 1(a). [Figure 3] FIG. 2 is a plan view showing a state in which a grinding gear and a gear to be ground are meshed together in the gear grinding device of the present embodiment. [Figure 4] 1 is a table showing the experimental results of the indentation hardness and arithmetic mean roughness of a coated test piece in which the tooth surface of a gear for grinding is coated with a plurality of resins. [Figure 5] 1 is a graph showing the relationship between the indentation hardness and the arithmetic mean roughness of the coated test piece. [Figure 6] Graphs showing the arithmetic mean roughness of the tooth surface of a grinding gear coated with acrylic resin before and after grinding the tooth surface of a gear to be processed, where (a) is a graph showing the arithmetic mean roughness before grinding, and (b) is a graph showing the arithmetic mean roughness after grinding. [Figure 7] FIG. 10 shows a second embodiment of the present invention, in which (a) is a side view showing a state in which a grinding gear and a gear to be ground are meshed together using the gear grinding device of this embodiment, and (b) is an enlarged view of part B in (a) of the same figure. [Figure 8] FIG. 2 is a plan view showing a state in which a grinding gear and a gear to be ground are meshed together in the gear grinding device of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a gear grinding apparatus and a gear grinding method according to the present invention will be described with reference to the accompanying drawings.

[0012] FIG. 1 is a side view showing a gear grinding apparatus according to a first embodiment of the present invention, FIG. 2(a) is a side view showing a state in which a grinding gear and a gear to be ground are meshed together using the gear grinding apparatus of this embodiment, FIG. 2(b) is an enlarged view of part A in FIG. 2(a), and FIG. 3 is a plan view showing a state in which a grinding gear and a gear to be ground are meshed together using the gear grinding apparatus of this embodiment.

[0013] 1, 2, and 3, the gear grinding apparatus 1 in the first embodiment includes a first electric motor 2 and a second electric motor 3, which are two drive mechanisms arranged on the left and right sides in Fig. 1; first and second rotating shafts 6 and 7 connected to first and second motor shafts 2a and 3a of the first and second electric motors 2 and 3 via first and second couplings 4 and 5, respectively; a grinding gear 8 attached to the tip of the first rotating shaft 6 and serving as a tool for machining; and a grinding gear 9 attached to the tip of the second rotating shaft 7 and meshing with the grinding gear 8 for machining. That is, in this embodiment, the small-diameter gear attached to the first rotating shaft 6 is set as the grinding gear 8, and the large-diameter gear attached to the second rotating shaft 7 is set as the grinding gear 9.

[0014] As shown in FIG. 2, the inter-axial distance S between the first rotating shaft 6 and the second rotating shaft 7 is set to a desired distance by a movement mechanism not shown, and in particular, the inter-axial distance S is adjusted according to the film thickness α of the coating layer 10, which will be described later.

[0015] The first and second electric motors 2, 3 are configured so that when one is driven, the other is driven. In this embodiment, the first electric motor 2 is the driving rotation side, and the second electric motor 3 is the driven rotation side. The drive, stop, rotation speed, etc. of the first electric motor 2 are controlled by an electronic control unit (not shown). The rotation speed of the driven first electric motor 2 is controlled to be constantly constant, for example, at approximately 2000 rpm per minute. Therefore, the rotation of the first electric motor 2 drives the grinding gear 8, and the rotational force is transmitted to the gear 9 to be ground, which meshes with the grinding gear 8, causing the second electric motor 3 to rotate in a driven manner.

[0016] The first and second couplings 4 and 5 have a general joint structure, and transmit the rotational driving force from the first motor shaft 2a to the grinding gear 8 via the corresponding first rotating shaft 6, and from there to the gear to be ground 9, which then rotates the second electric motor 3 via the second coupling 5. The first and second rotating shafts 6 and 7 are rotatably supported by a pair of bearings provided on a pair of support plates not shown.

[0017] The grinding gear 8 and the grinded gear 9 are spur gears made of, for example, chrome molybdenum steel (SCM420H). In this embodiment, the grinding gear 8 is on the small diameter side and has 17 teeth, while the grinded gear 9 is on the large diameter side and has 31 teeth.

[0018] 2(b) and 3, both tooth flanks 8a, 9a of the grinding gear 8 and the gear to be ground 9 are machined into a crowned shape, and as shown in Fig. 3, central portions 8b, 9b (hatched areas in the figure) in the tooth trace direction (tooth width direction) L are formed more convexly than both end portions 8c, 8c, 9c, 9c in the tooth width direction L, and are higher than both end portions 8c-9c. When the grinding operation begins, the grinding gear 8 and the gear to be ground 9 are configured so that the central portions 8b, 8b (areas surrounded by ellipses) of each tooth flank 8a of the grinding gear 8 mesh with the central portions 9b, 9b of each tooth flank 9a of the gear to be ground 9, as shown in Figs. 2(b) and 3.

[0019] Before being assembled in the grinding machine, the entire tooth surface 8a of the grinding gear 8 is coated with a resin material, such as an acrylic resin material, as shown by the dots in Fig. 2(b). The coating layer 10 of this acrylic resin material has a film thickness α of about 20 μm and an indentation hardness of about 20 N / mm. 2 The above is approximately 360N / mm 2 The indentation hardness is set as follows: As will be described later, the inventors of the present application selected this numerical value based on the relationship with the arithmetic mean roughness Ra, which is the surface roughness of the tooth flank 9a of the grinding target gear 9 when ground by the tooth flank 8a of the grinding gear 8, through experiments.

[0020] The distance S between the first rotating shaft 6 and the second rotating shaft 7 is adjusted to a distance corresponding to the film thickness α of the coating layer 10 applied to the tooth surface 8a of the grinding gear 8. This allows the tooth surface load to be controlled.

[0021] As shown in FIG. 6(a) to be described later, the gear 9 to be ground has a tooth surface 9a with an arithmetic mean roughness Ra of about 0.32 μm before grinding.

[0022] Furthermore, during polishing, a polishing liquid is supplied to the meshing portion between the polishing gear 8 and the workpiece gear 9, for example, by splashing. The base oil of the polishing liquid contains abrasive grains, which are an abrasive material. For example, silicon carbide-based GC#3000 abrasive grains are used, and their average particle size is set smaller than the film thickness α (approximately 20 μm) of the coating layer 10, for example, approximately 4 μm. The size of these abrasive grains is preferably less than one-fifth of the film thickness α of the coating layer 10, which is approximately 20 μm. In other words, if the average particle size is larger than the film thickness α, the amount of protrusion from the film thickness α increases, resulting in a surface roughness greater than desired for the tooth surface 9a of the workpiece gear 9.

[0023] Considering the relative relationship between the indentation hardness of the coating layer 10 on the tooth surface 8a of the grinding gear 8 and the size of the abrasive grains contained in the grinding liquid, if the indentation hardness is low (soft), when a grinding load is applied to the abrasive grains, the abrasive grains sink into the coating layer 10, reducing the depth of cut of the abrasive grains. As the depth of cut of the abrasive grains decreases, the surface roughness of the tooth surface 9a of the grinded gear 9 is improved. Furthermore, as the indentation hardness decreases, the amount of sinking of the abrasive grains into the coating layer 10 increases, resulting in a stronger retention of the abrasive grains. As the retention of the abrasive grains in the coating layer 10 increases, the abrasive grains are less likely to fall off the coating layer 10 and become rolling abrasive grains, improving the surface roughness of the tooth surface 9a.

[0024] Therefore, there is a strong correlation between the indentation hardness of the coating layer 10 on the tooth surface 8a and the surface roughness of the tooth surface 9a of the gear 9 to be ground. For this reason, the inventors of the present application conducted experiments and, based on the experimental results shown in Figures 4 and 5 below, concluded that in order to make the arithmetic mean roughness of the tooth surface 9a of the gear 9 to be ground 0.15 μm or less, the indentation hardness of the coating layer 10 should be approximately 20 N / mm 2 More than 360N / mm2 The reason why the arithmetic mean roughness of the tooth surface 9a of the gear 9 to be ground is set to 0.15 μm or less is because the tooth surface 9a becomes a glossy, smooth surface, which ensures smooth rotation of the gear.

[0025] Figure 4 is a table showing the experimental results of the indentation hardness and arithmetic mean roughness of a coated test piece in which the tooth surface of a gear for grinding was coated with multiple resins, and Figure 5 is a graph showing the relationship between the indentation hardness and arithmetic mean roughness of the same coated test piece.

[0026] As shown in FIG. 4, the inventors of the present application measured the indentation hardness (N / mm 2 ) and the arithmetic mean roughness Ra (μm) of the tooth surface 9a of the gear 9 to be ground.

[0027] The resin materials used for the coating test pieces were epoxy resin (A), vinyl chloride resin (B), nitrocellulose resin (C), urethane resin (D), acrylic resin (E), amide-imide resin (F), and phenol-epoxy resin (G).The soft metal material used for the coating test pieces was bright tin plating (H).

[0028] From the results of this experiment, as shown in FIG. 4, the indentation hardness (N / mm 2 ) was 212 for (A), 220 for (B), 325 for (C), 194 for (D), 25 for (E), 670 for (F), 417 for (G), and 207 for (H). The indentation hardness ((N / mm 2 It was found that the arithmetic mean roughness Ra (μm) of the tooth surface 9a of the gear 9 to be ground for (A) was 0.13, (B) was 0.12, (C) was 0.15, (D) was 0.12, (E) was 0.15, (F) was 0.33, (G) was 0.26, and (H) was 0.15.

[0029] Considering the relative relationship between the indentation hardness and the arithmetic mean roughness Ra, as shown in the dashed frame in Figure 5, the indentation hardness of the tooth surface 8a of the grinding gear 8 is approximately 20 N / mm 2 The above is approximately 360N / mm 2 In other words, it was found that the indentation hardness of the tooth surface 8a is about 20 N / mm in relation to the average particle diameter of the abrasive grains contained in the polishing liquid. 2 If the abrasive grains are less than this, the coating layer 10 will be too soft, and the abrasive grains will easily sink into the coating layer 10, resulting in almost no protrusion from the coating layer 10, which may result in insufficient grinding of the tooth surface 9a of the gear 9 to be ground. On the other hand, if the abrasive grains are less than this, as in (F) and (G), the abrasive grains will be less than 360 N / mm 2 If this is the case, the coating layer 10 becomes too hard, the abrasive grains do not sink into the coating layer 10, the amount of protrusion becomes excessively large, the arithmetic mean roughness of the tooth surface 9a becomes 0.15 μm or more, and the desired polishing becomes difficult.

[0030] From the experimental results shown in FIGS. 4 and 5, the indentation hardness of the coating layer 10 on the tooth surface 8a is set to about 20 N / mm 2 ~Approx. 360N / mm 2 If the range is set to this range, it is clear that the arithmetic mean roughness of the gear 9 to be ground will be 0.15 μm or less in relation to the average particle diameter of the abrasive grains. Therefore, in this embodiment, the indentation hardness of the coating layer 10 on the tooth surface 8 a is set to about 20 N / mm 2 ~Approx. 360N / mm 2 The range was set as follows.

[0031] Figure 6 shows the arithmetic mean roughness Ra of the tooth surface of a grinding gear coated with acrylic resin before and after grinding the tooth surface of a gear to be processed. (a) is a graph showing the arithmetic mean roughness Ra before grinding, and (b) is a graph showing the arithmetic mean roughness Ra after grinding.

[0032] In the above experiment, when the acrylic resin (E) was used as the coating layer 10, the arithmetic mean roughness Ra of the tooth surface 9a of the gear 9 to be ground was examined. As shown in FIG. 6(a), before grinding with the grinding gear 8, the arithmetic mean roughness Ra was approximately 0.32 μm. However, after grinding, as shown in FIG. 6(b), the arithmetic mean roughness Ra became approximately 0.15 μm.

[0033] Therefore, in this embodiment, acrylic resin (E) was selected as the resin material that satisfies the relationship between the indentation hardness and the arithmetic mean roughness Ra. Nitrocellulose resin (c) could also be selected. Furthermore, bright tin plating (H) was selected as the soft metal material in the above experiment, and since this bright tin plating (H) also obtained results that were almost the same as those of nitrocellulose resin (C) and acrylic resin (E), this bright tin plating (H) can also be used.

[0034] [Gear Polishing Method According to the Present Embodiment] The gear grinding method according to this embodiment will now be described. The process includes the following three steps: a first step of forming an acrylic resin coating layer 10 on the tooth surface 8a of the grinding gear 8; a second step of meshing the grinding gear 8 with the gear 9 to be ground at a predetermined center distance S; and a third step of polishing the tooth surface 9a of the gear 9 to be ground by rotating the grinding gear 8 while supplying a polishing liquid containing abrasive grains with an average grain size smaller than the film thickness α of the coating layer 10 on the tooth surface 8a of the grinding gear 8 to the meshing point between the tooth surfaces 8a, 9a of the grinding gear 8 and the gear 9 to be ground.

[0035] The specific configurations of this gear grinding method, i.e., the indentation hardness of the coating layer 10 on the tooth surface 8a of the grinding gear 8 and the arithmetic mean roughness Ra of the tooth surface 9a of the gear 9 to be ground by grinding, are as described above.

[0036] Therefore, according to the polishing apparatus and polishing method of this embodiment, the average particle size of the abrasive grains contained in the polishing liquid is made smaller than the film thickness α of the coating layer 10 of, for example, an acrylic resin formed on the tooth surface 8a of the polishing gear 8, thereby preventing deterioration of the surface roughness of the polished tooth surface 9a of the gear 9 to be polished.

[0037] In particular, in this embodiment, a coating layer 10 made of acrylic resin or the like is formed on the tooth surface 8a of the grinding gear 8. Therefore, if the coating layer 10 wears away due to long-term grinding, the tooth surface 8a can be re-applied with the coating layer 10, and the same grinding gear 8 can be used for grinding again.

[0038] Therefore, unlike the conventional technology, there is no need to replace the worn grinding gear 8 with a new one, which reduces material costs and processing costs, and also reduces the impact on the resource environment because the grinding gear 8 can be used as is.

[0039] Furthermore, during grinding, when the tooth flank 8a of the grinding gear 8 and the tooth flank 9a of the gear to be ground 9 come into contact with each other at both ends 8c, 8c and 9c, 9c in the face width direction L, the surface pressure is higher at both ends 8c-9c than at the center 8b, 9b in the face width direction L, making it easier for wear and peeling to occur in the coating layer 10 on the both ends 8c-9c side.

[0040] However, in this embodiment, because the tooth flanks 8a, 9a are crowned, the widthwise end portions 8c-9c do not come into contact, and only the central portions 8b, 9b come into contact. This prevents wear and peeling of the coating layer 10 on the end portions 8c-9c during grinding. As a result, wear of the coating layer 10 of the gear 8 to be ground can be reduced. Furthermore, the tooth widthwise end portions 8c-9c, which do not affect the meshing of the tooth flanks 8a, 9a, are not ground, thereby reducing the processing time. Second Embodiment 7 and 8 show a second embodiment of the present invention, in which FIG. 7(a) is a side view showing the state in which a grinding gear and a gear to be ground are meshed together using the gear grinding device of this embodiment, FIG. 7(b) is an enlarged view of part B in FIG. 7(a), and FIG. 8 is a plan view showing the state in which a grinding gear and a gear to be ground are meshed together using the gear grinding device of this embodiment.

[0041] In this second embodiment, the gear to be ground 8 and the gear to be ground 9 of the first embodiment are reversed, with the gear on the smaller diameter side being the gear to be ground 9 and the gear on the larger diameter side being the gear to be ground 8. In addition, the first electric motor 2 is configured as a driven motor, and the second electric motor 3 is configured as a drive motor, and the rotational drive of this second electric motor 3 is controlled by a control unit not shown.

[0042] As shown in Figure 7, the small-diameter gear to be ground 9 and the large-diameter gear to be ground 8 have the same number of teeth, 17 and 31, respectively, and an acrylic resin coating layer 10 with a film thickness α of approximately 20 μm is formed on the surface of the tooth flank 8a of the large-diameter gear to be ground 8, as shown in Figures 7(b) and 8. The indentation hardness of this coating layer 10 is approximately 20 N / mm, taking into account slight measurement errors, etc. 2 ~Approx. 360N / mm 2 is set to the range. As in the first embodiment, the abrasive grains contained in the polishing liquid are, for example, silicon carbide-based GC#3000, and the average grain size is set smaller than the film thickness α (approximately 20 μm) of the coating layer 10, for example, approximately 4 μm.

[0043] The arithmetic mean roughness Ra of the tooth flank 9a of the gear 9 to be ground before grinding is approximately 0.32 μm, as shown in Fig. 6(a). Other configurations, such as the fact that each tooth flank 8a, 9a is crowned and central portions 8b, 9b (areas indicated by ellipses) are convex, are the same as in the first embodiment.

[0044] Therefore, in the second embodiment, as in the first embodiment, the average particle size of the abrasive grains is made smaller than the film thickness α of the acrylic resin coating layer 10 on the tooth surface 8a, thereby making it possible to suppress deterioration of the surface roughness of the ground tooth surface 9a of the gear 9 to be ground.

[0045] Furthermore, since a coating layer 10 made of acrylic resin or the like is formed on the tooth surface 8a of the grinding gear 8, if the tooth surface 8a becomes worn, the coating layer 10 can be applied again to the tooth surface 8a, and the same grinding gear 8 can be used to grind it again.

[0046] Therefore, the same effects as those of the first embodiment can be obtained, such as reduced material costs and processing costs. In addition, in this embodiment, the number of teeth of the grinding gear 8 is greater than the number of teeth of the gear 9 to be ground, so the grinding work time can be shortened.

[0047] The present invention is not limited to the configurations of the above-described embodiments, and can be applied to gears other than spur gears, such as helical gears, in which the gear to be ground and the gear to be ground are formed. Furthermore, the size and number of teeth of both gears can be freely set.

[0048] Furthermore, the thickness of the coating layer and the average particle size of the abrasive grains can also be changed relatively freely.

[0049] In the above embodiment, the coating layer formed on the tooth surface of the grinding gear is made of a resin material and a soft metal such as bright tin plating, but it is also possible to use matte tin plating or tin alloy plating.

[0050] Furthermore, as the abrasive grains contained in the polishing liquid, in addition to silicon carbide, white alundum, which is a type of alumina, can also be used. [Explanation of symbols]

[0051] 1...grinding device, 2...first electric motor, 3...second electric motor, 4·5...coupling, 6·7...rotating shaft, 8...gear to be ground, 8a...tooth surface, 8b...center, 8c...both ends, 9...gear to be ground, 9a...tooth surface, 9b...center, 9c...both ends, 10...coating layer, S...center distance, L...face width direction.

Claims

1. A grinding device that grinds a tooth surface of a gear to be ground by rotating a grinding gear while the gear and the gear to be ground are meshed, comprising: forming a coating layer of a resin material or a soft metal on the tooth surface of the gear to be polished; A gear polishing device characterized by supplying a polishing liquid containing abrasive grains with an average grain size smaller than the film thickness of the coating layer of the gear to be polished to the meshing point between the polishing gear and the gear to be polished, and rotating the polishing gear to polish the tooth surface of the gear to be polished.

2. 2. The gear grinding device according to claim 1, The tooth flanks of the gear to be polished and the tooth flanks of the gear to be polished are each formed with a crowning shape that is higher at the center of the tooth width of the tooth flank, and the gear polishing device is characterized in that the center of the tooth width of the tooth flank of the gear to be polished is polished.

3. 2. The gear grinding device according to claim 1, The indentation hardness of the resin or soft metal coating layer applied to the tooth surface of the grinding gear is about 20 N / mm ２ Above about 360N / mm ２ A gear grinding device characterized by the following settings:

4. 2. The gear grinding device according to claim 1, 10. A gear grinding device according to claim 9, wherein the resin material formed on the tooth surface of the gear to be ground is an acrylic resin material or a nitrocellulose resin material.

5. 2. The gear grinding device according to claim 1, 1. A gear polishing device according to claim 1, wherein the soft metal formed on the tooth surface of the gear to be polished is plated with tin or a tin alloy.

6. 2. The gear grinding device according to claim 1, A gear polishing device characterized in that the center distance between the gear to be polished and the gear to be polished when they are meshed is adjusted to a distance corresponding to the film thickness of the coating layer.

7. a grinding method in which the grinding gear and the gear to be ground are engaged with each other, and the grinding gear is rotationally driven to grind the tooth surface of the gear to be ground by the grinding gear, a step of forming a coating layer of a resin material or a soft metal on the tooth surface of the gear to be polished in advance; a step of meshing the gear to be ground and the gear to be ground at a predetermined center distance; a step of polishing the tooth surface of the gear to be polished by rotating the polishing gear while supplying a polishing liquid containing abrasive grains having an average grain size smaller than the film thickness of the coating layer of the gear to be polished to a meshing point between the polishing gear and the gear to be polished; A gear polishing method comprising the steps of:

8. A grinding method comprising: a first gear and a second gear that mesh with each other to form a pair; one of the first gear and the second gear being a gear to be ground and the other being a gear to be ground; and grinding a tooth surface of the gear to be ground by rotating the gear to be ground, a step of forming a coating layer of a resin material or a soft metal on the tooth surface of the gear to be ground; a step of meshing the pair of gears to be ground and the gear to be ground at a predetermined center distance; a step of polishing the tooth surface of the gear to be polished by rotating the polishing gear while supplying a polishing liquid containing abrasive grains having an average grain size smaller than the film thickness of the coating layer on the tooth surface of the polishing gear to a meshing location between the polishing gear and the gear to be polished; A gear polishing method comprising the steps of:

9. 9. A gear grinding method according to claim 8, comprising: The tooth flanks of the gear to be polished and the gear to be polished are each formed with a crowning shape that is higher at the center of the tooth width of the tooth flank, and the center of the tooth width of the gear to be polished is polished.

10. 9. A gear grinding method according to claim 8, comprising: The indentation hardness of the resin or soft metal coating layer applied to the tooth surface of the grinding gear is about 20 N / mm ２ Above about 360N / mm ２ A gear grinding method characterized by the following:

11. 9. A gear grinding method according to claim 8, comprising: A gear polishing method characterized in that the resin material formed on the tooth surface of the gear to be polished is an acrylic resin material or a nitrocellulose resin material.

12. 9. A gear grinding method according to claim 8, comprising: A method for polishing a gear, wherein the soft metal formed on the tooth surface of the gear to be polished is plated with tin or a tin alloy.

13. 9. A gear grinding method according to claim 8, comprising: a gear grinding method characterized in that the center distance between the gear to be ground and the gear to be ground when they are meshed is adjusted to a distance corresponding to the film thickness of the coating layer.

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