Gear wheel and method for manufacturing gear wheel

Abstract

To provide a gear wheel that can improve toughness of a tooth bottom and a dedendum to improve durability of a gear wheel, and to provide a method for manufacturing a gear wheel that can improve workability of manufacturing operation of a gear wheel that can improve durability.SOLUTION: A gear wheel 1 includes: a tooth bottom 2A; a dedendum 2B communicated to the tooth bottom 2A; an addendum 2C; a tooth flank 2D formed between the dedendum 2B and the addendum 2C; a carburized layer 5 provided on the tooth flank 2D; and a non-carburized part 6 provided in a dedendum part 3, where the dedendum part 3 has a surface hardness that is lower than the hardness of the tooth flank 2D.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a gear and a method for manufacturing a gear. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there has been known a method for manufacturing a toothed component in which a carburizing treatment is carried out to add carbon to a gear in order to improve the hardness and wear resistance of a surface layer (see Patent Document 1).

[0003] In this method of manufacturing a toothed part, when manufacturing a toothed part that has been carburized and quenched, the carburization treatment is carried out in a state where the tip portion of the toothed part has been subjected to an anti-carburization treatment. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 63-109152 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in conventional methods for manufacturing toothed parts, masking is required to apply anti-carburizing treatment only to the tips of the gear teeth, which requires the effort of masking and the process of removing the masking.

[0006] In addition, the carburized hardened layer has the properties of improving hardness and wear resistance, but decreasing toughness. In the conventional manufacturing method for toothed parts, the tooth base and tooth bottom are also carburized, which decreases the toughness of the tooth base and tooth bottom.

[0007] If the toughness of the tooth base or tooth bottom decreases, the gear will be weak against impacts and bending caused by the meshing of the teeth, and the carburized areas will be more likely to cause cracks (fissures or splits), which may reduce the durability of the gear.

[0008] The present invention has been made in light of the above-mentioned circumstances, and has as its object to provide a gear that can improve the toughness of the tooth root and the tooth base to thereby improve the durability of the gear, and a method for manufacturing such a gear that can improve the workability of the gear manufacturing operation. [Means for solving the problem]

[0009] The present invention is a gear having a tooth bottom, a tooth base connected to the tooth bottom, a tooth tip, and a tooth surface formed between the tooth base and the tooth tip, characterized in that it has a carburized hardened layer provided on the tooth surface and non-carburized portions provided on the tooth bottom and the tooth base, and the hardness of the surface of the tooth bottom and the surface of the tooth base is lower than the hardness of the tooth surface.

[0010] The present invention is also characterized by including a gear cutting process for cutting the gear including the bottom, the root connected to the bottom, the tip, and the tooth surface formed between the root and the tip; a carburization treatment process for applying carburization treatment to the entire gear including the bottom, the root, the tip and the tooth surface; a removal process for removing the carburization treatment portion formed on the tooth surface by the carburization treatment process; and a carburization and quenching process for carburizing and quenching the tooth surface. Effect of the Invention

[0011] As described above, according to the present invention, it is possible to provide a gear that can improve the toughness of the tooth root and the tooth base to improve the durability of the gear, and it is also possible to provide a method for manufacturing a gear that can improve the workability of the manufacturing operation of the gear with improved durability. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing a part of a gear according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing a part of a gear that has been subjected to anti-carburization treatment according to one embodiment of the present invention. [Diagram 3] FIG. 3 is a diagram showing a part of a gear that has been subjected to a case-hardening treatment according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] A gear according to one embodiment of the present invention has a tooth bottom, a tooth base connected to the tooth bottom, a tooth tip, and a tooth surface formed between the tooth base and the tooth tip, and has a carburized hardened layer on the tooth surface and non-carburized portions on the tooth bottom and tooth base, and the hardness of the surfaces of the tooth bottom and tooth base is lower than the hardness of the tooth surface.

[0014] As a result, the gear according to one embodiment of the present invention can improve the toughness of the tooth root and the tooth base, thereby improving the durability of the gear.

[0015] In addition, a manufacturing method for a gear in one embodiment of the present invention includes a gear cutting process for cutting the teeth including the bottom, the base, the tip, and the tooth surface formed between the base and the tip, a carburization treatment process for applying a carburization treatment to the entire gear including the bottom, the base, the tip and the tooth surface, a removal process for removing the carburization treatment portion formed on the tooth surface by the carburization treatment process, and a carburization and quenching process for carburizing and quenching the tooth surface.

[0016] As a result, the method for manufacturing a gear according to one embodiment of the present invention can improve the workability of manufacturing gears with improved durability. EXAMPLES

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A gear and a method for manufacturing a gear according to an embodiment of the present invention will now be described with reference to the drawings.

[0018] 1 to 3 are diagrams showing a gear and a method for manufacturing the gear according to one embodiment of the present invention.

[0019] First, the configuration will be described. 1, a gear 1 is roughly machined to have teeth 2 by gear cutting using a hob tool (not shown). This gear cutting corresponds to a gear cutting process.

[0020] The teeth 2 formed by the gear cutting process have a tooth bottom 2A, a tooth base 2B connected to the tooth bottom 2A, a tooth tip 2C, and a tooth surface 2D formed between the tooth base 2B and the tooth tip 2C.

[0021] After the gear cutting process, the entire gear 1, including the tooth bottom 2A, the tooth base 2B, the tooth tip 2C, and the tooth surface 2D, is subjected to anti-carburization treatment (anti-carburization treatment process). Here, the R-shaped portion including the tooth bottom 2A and the tooth base 2B is also referred to as the tooth base portion 3.

[0022] Next, as shown in FIG. 2, the entire gear 1 including the tooth tip 2C, tooth surface 2D and tooth base 3 is subjected to anti-carburization treatment to form anti-carburization areas 4 shown hatched (anti-carburization treatment step).

[0023] Next, the tooth surface 2D is precisely machined by shaving, and the anti-carburization treatment portion 4 on the tooth surface 2D is removed (removal step).

[0024] The shaving process processes only the tooth surface 2D, and only the anti-carburization treatment portion 4 on the tooth surface 2D is removed, so that the anti-carburization treatment portion 4 remains on the tooth tip 2C, the tooth base 3, and the tooth end 2E (the end surface in the tooth width direction of the tooth 2). In Figures 1 to 3, only one end surface in the tooth width direction of the tooth end 2E is shown, but a tooth end is also formed on the other end surface in the tooth width direction on the opposite side, and this tooth end is also subjected to anti-carburization treatment.

[0025] Next, the tooth surface 2D is subjected to carburizing and hardening treatment to form a carburized hardened layer 5 (see FIG. 3). As a result, non-carburized portions 6 that are not subjected to carburizing treatment are formed on the tooth tip 2C, the tooth base 3, and the tooth end 2E (see FIG. 3).

[0026] 2 and 3, the carburized portion 4 and the non-carburized portion 6 are highlighted by hatching so that the treated portions are clearly visible for ease of explanation.

[0027] Here, carburizing and quenching is a process in which carbon is dissolved from the surface layer of a metal to harden only the surface, with the aim of improving hardness and wear resistance, and quenching is also performed at the same time.

[0028] As for the carburizing method, in addition to solid carburizing (charcoal), gas carburizing, liquid carburizing, vacuum carburizing (a method of carburizing using a vacuum furnace), plasma carburizing (also called ion carburizing) and drip carburizing (a CHO-based liquid organic agent is dripped into a furnace and the carbon generated by pyrolysis is used) can be used, but they are not limited to these.

[0029] Anti-carburizing is a process that is performed on materials before carburizing to prevent carburization of the materials. Examples of anti-carburizing processes include Cu plating, Cr plating, Ni plating, etc., but are not limited to these.

[0030] Next, the effects of the gear 1 of this embodiment will be described. The carburized hardened layer 5 has the properties of improving hardness and wear resistance but decreasing toughness, so that when the tooth base 3 is carburized, the toughness of the tooth base 3 decreases.

[0031] If the toughness of the tooth base 3 decreases, when bending stress is applied to the tooth 2 as a result of the tooth surface 2D meshing with the tooth surface of another gear, the tooth base 3, which is the area with reduced toughness, becomes weak against impact and bending, and is prone to cracks.

[0032] The gear 1 of this embodiment has a bottom 2A, a base 2B connected to the bottom 2A, a tooth tip 2C, a tooth surface 2D formed between the base 2B and the tooth tip 2C, a carburized hardened layer 5 provided on the tooth surface 2D, and a non-carburized portion 6 provided in the base 3, and the hardness of the surface of the base 3 is lower than that of the tooth surface 2D.

[0033] This makes it possible to suppress a decrease in the toughness of the tooth base 3 and increase the strength of the tooth base 3. Therefore, when bending stress is applied to the tooth 2 as a result of the tooth surface 2D meshing with the tooth surface of another gear, it is possible to increase the resistance of the tooth base 3 to impact and bending stress.

[0034] As a result, the occurrence of cracks in the tooth base portion 3 can be suppressed, and the durability of the gear 1 can be prevented from being deteriorated.

[0035] In addition, the manufacturing method of gear 1 in this embodiment includes a gear cutting process that performs gear cutting processing including bottom 2A, root 2B connected to bottom 2A, tooth tip 2C, and tooth surface 2D formed between root 2B and tooth tip 2C, a carburization treatment process that performs carburization treatment on the entire gear 1 including bottom 2A, root 2B, tip 2C and tooth surface 2D, a removal process that removes carburization treatment portion 4 formed on tooth surface 2D by the carburization treatment process, and a carburization and quenching process that carburizes and quenches the tooth surface 2D.

[0036] This allows easy anti-carburization treatment of gear 1, and easy manufacturing of gear 1 that does not have carburized quenching treatment applied to root portion 3. As a result, the workability of manufacturing gear 1, which can improve durability, can be improved.

[0037] Here, since the tooth surface 2D is formed long in the tooth width direction (axial direction of the gear 1), when the tooth surface 2D is carburized and hardened, the carburized hardened layer tends to merge with the adjacent tooth surface 2D at the tooth tip 2C or tooth end 2E.

[0038] As a result, a carburized hardened layer develops deep into the tooth tips 2C and tooth ends 2E, the toughness of the tooth tips 2C and tooth ends 2E decreases significantly, and they become weak against impact and bending, making them susceptible to cracks.

[0039] According to the manufacturing method of gear 1 of this embodiment, after the entire gear 1 including the tooth bottom 2A, the tooth base 2B, the tooth tip 2C and the tooth surface 2D is subjected to carburization treatment, the carburization-proof treated portion 4 formed on the tooth surface 2D in the carburization treatment process is removed and the tooth surface 2D is carburized and hardened. This makes it possible to form the non-carburized portion 6 while leaving the carburization-proof treated portion 4 on the tooth tip 2C and the tooth end 2E.

[0040] As a result, the toughness of the tooth tip 2C and the tooth end 2E is prevented from decreasing, and when the tooth surface 2D meshes with the tooth surface of another gear and an impact or bending stress is applied to the tooth 2, the strength of the tooth tip 2C and the tooth end 2E can be increased, and the tooth tip 2C and the tooth end 2E can adequately withstand the impact and bending stress.

[0041] Therefore, the occurrence of cracks in the tooth tips 2C and the tooth ends 2E can be suppressed, and the durability of the gear 1 can be more effectively prevented from deteriorating.

[0042] Alternatively, a cylindrical opening may be formed on the inner periphery of gear 1, an inner spline into which the outer spline of the rotating shaft fits may be formed on the inner periphery of the opening, and the inner spline may be subjected to carburizing and quenching.

[0043] Although an embodiment of the invention has been disclosed, it will be apparent to one of ordinary skill in the art that modifications may be made thereto without departing from the scope of the invention, and it is intended that all such modifications and equivalents be included in the following claims. [Explanation of symbols]

[0044] 1 Gears 2 Teeth 2A Root 2B Root 2C Tooth tip 2D tooth surface 5 Carburized hardening layer 6 Non-carburized parts

Claims

1. A gear having a tooth bottom, a tooth base connected to the tooth bottom, a tooth tip, and a tooth surface formed between the tooth bottom and the tooth tip, A carburized hardened layer provided on the tooth surface; a non-carburized portion provided at the tooth bottom and the tooth base, A gear, characterized in that the hardness of the tooth bottom surface and the tooth root surface is lower than the hardness of the tooth flank.

2. a gear cutting process for cutting a tooth including a tooth bottom, a tooth base connected to the tooth bottom, a tooth tip, and a tooth surface formed between the tooth bottom and the tooth tip; a carburization prevention treatment process for performing carburization prevention treatment on the entire gear including the tooth bottom, the tooth base, the tooth tip, and the tooth surface; a removing step of removing the anti-carburizing treatment portion formed on the tooth surface by the anti-carburizing treatment step; a carburizing and quenching treatment step of carburizing and quenching the tooth surface.

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