JPH08311636A - Gear and its production - Google Patents

Abstract

PURPOSE: To provide a gear with which the deviation in dimensional accuracy at the time of a nitriding treatment and the degradation in surface roughness are minimized, noises are small and which has excellent wear resistance. CONSTITUTION: The metallic gear, such as upper shaft bevel gear 3, is held for a prescribed period of time in a gaseous fluorine atmosphere previously maintained at a high temp. and fluorinated films are formed on its respective tooth surfaces, flanks, etc. The gear is thereafter heated for the prescribed period of time in a nitriding gaseous atmosphere, by which nitrided hard layers are formed thereon with the flurinated films described above as reaction media. The nitride films are formed on the surfaces of the gear in such a manner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal gear used in various machines and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, in the case of metal gears used in various machines, in order to prevent fatigue wear of the surface due to repeated loads called pitching and spalling, various surface hardening is applied to the gears. The law has been taken. Generally, a harder material improves pitting resistance, that is, wear resistance. Surface hardening methods for gear tooth surfaces include solid carburizing methods, gas carburizing methods, liquid carburizing methods, induction hardening methods, flame hardening methods, and nitriding methods.

Among these surface hardening methods, the nitriding method is more excellent in wear resistance and fatigue resistance than hardening methods such as carburizing, and is also effective for galling caused by seizure called scoring. Has been widely used.
The nitrogen compound layer formed by the nitriding treatment has a thickness of 10
Since the thickness is as thin as μm or less, it is not possible to perform processing for correcting dimensions and surface roughness after processing, and the processed surface is usually used as it is.

[0004]

However, according to the conventional nitriding treatment of gears, the gear is placed at a high temperature of 500 to 600 ° C. for the purpose of activating the surface and promoting the diffusion and reaction of nitrogen, so that the gear cutting is performed. The processing strain remaining on the surface layer during processing was released, and so-called thermal deformation occurred. In addition, since a non-uniform nitrogen compound layer of about 5 to 10 μm is formed on the surface of the gear by the nitriding treatment, dimensional swelling occurs and the tooth surface becomes rougher than before the treatment. was there. Therefore, because the meshing accuracy of the gears goes wrong,
For example, like an industrial sewing machine, 5000 to 10000
There is a problem that noise is increased during high-speed operation such as rpm, and sometimes wear is increased due to local load.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to minimize the deviation of the dimensional accuracy and the deterioration of the surface roughness during the nitriding treatment, and to reduce the noise. The purpose is to provide a gear having excellent wear resistance.

[0006]

In order to achieve this object, according to the gear of claim 1 of the present invention, at least a contact surface of a tooth of a metal gear meshing with another gear is fluorinated. Further, a nitriding process is applied to that portion to form a nitride film.

According to a second aspect of the present invention, there is provided a method for manufacturing a gear, wherein at least a contact portion of a tooth of a metal gear that meshes with another gear is heated in a fluorine-based gas atmosphere for a predetermined time, and the surface of the portion is contacted. A fluoride film is formed, and thereafter, the portion is heated in a nitriding gas atmosphere for a predetermined time to separate and remove the fluoride film, and at the same time, a nitride film is replaced and formed on the removed portion.

Further, in the method of manufacturing a gear according to a third aspect of the present invention, before forming the fluorinated film, the portion where the fluorinated film is formed is subjected to carburizing quenching, induction quenching, flame quenching, etc. A quenching process and a tempering process are performed.

[0009]

According to the gear of the first aspect of the present invention having the above-mentioned structure, at least the contact surface of the tooth of the metal gear that meshes with another gear is subjected to a fluorination treatment, and further, the nitriding treatment is applied to that portion. To form a nitride film.

Further, according to the method of manufacturing a gear of claim 2, at least a contact portion of a tooth of a metal gear that meshes with another gear is heated in a fluorine-based gas atmosphere for a predetermined time, and the portion A fluoride film is formed on the surface, and then that portion is heated in a nitriding gas atmosphere for a predetermined time to separate and remove the fluoride film, and at the same time, a nitride film is replaced and formed on the removed portion. In this case, the fluorinated film acts as a very active film when heated to the fluorination temperature or higher, and therefore, when nitriding treatment is applied to this portion, nitrogen is adsorbed at a temperature much lower than the conventional temperature. Then, nitrogen is diffused to the surface layer. At this time, the fluorinated film is removed from the surface by replacing nitrogen with nitrogen.

Further, according to the method of manufacturing a gear of claim 3, before forming the fluoride film, the portion where the fluoride film is formed is carburized, induction hardened, and flame hardened. Quenching treatment and tempering treatment. In this case, the hardness of the portion where the nitride film is finally formed can be increased to the deep layer region.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment in which the present invention is embodied in a gear used in a sewing machine will be described below with reference to the drawings.

FIG. 1 shows the structure of a power transmission mechanism between an upper shaft and a lower shaft of an industrial lockstitch sewing machine of this embodiment. When the pulley 1 driven via a belt by a drive source (not shown) such as a motor rotates in the direction of the arrow in the figure, the upper bevel gear 3 attached to the upper shaft 2 connected to the pulley 1 causes a vertical movement. The rotation is transmitted to the vertical axis bevel gear 5 attached to the upper end of the shaft 4. This rotational movement is caused by the vertical axis 4
The vertical axis bevel gear 6 attached to the lower end transmits the lower axis bevel gear 7 to the lower axis 8. The gear ratios of the gears combined at these two locations are set to be 1: 2 in total, so that the sewing machine hook 9 fixed to the end of the lower shaft 8 has a gear ratio of 2: 1. It will rotate at twice the number of rotations. Here, each of the upper bevel gear 3, the vertical bevel gear 5, the vertical bevel gear 6, and the lower bevel gear 7 is subjected to the following nitriding treatment according to the method of the present invention to obtain a surface-hardened excellent wear resistance. It is formed of a metal material having a layer.

FIG. 2 shows a structure of a power transmission mechanism between a lower shaft of a two-needle type industrial lockstitch sewing machine having a structure different from that of the sewing machine and a sewing machine hook. In this type of sewing machine, the power transmission between the upper shaft and the lower shaft is performed by the timing belt 12 and the timing pulley 12 mounted on the upper shaft 11 and the lower shaft 1.
This is done by the timing pulley 14 attached to the No. When the lower shaft 13 rotates, the rotational movement is transmitted to the two spiral gears 15 attached to the lower shaft 13. The vertical rotary motion of the spiral gear 15 causes the two sewing machine hooks 17 to rotate horizontally via the pinion gears 16 paired with the respective spiral gears 15. The spiral gear 15 and the pinion gear 1
6 is set to a gear ratio of 1: 2, so that the sewing machine hook 17 rotates at twice the number of rotations of the lower shaft 13. Here, the respective gears of the two spiral gears 15 and the pinion gears 16 are also formed of a metal material having a surface hardened layer having excellent wear resistance by performing the following nitriding treatment according to the method of the present invention. .

Next, a method of manufacturing each gear of the present invention will be described. The gear is made of carbon steel or alloy steel as a material, and is mainly formed by cutting and polishing the tooth surface. The gears processed in this way are entirely held in advance in a fluorine-based gas atmosphere at a high temperature for a predetermined time, and after forming a fluoride film on the tooth surfaces and side surfaces thereof, they are heated in a nitriding gas atmosphere for a predetermined time, A hard nitride layer is formed using the fluoride film as a reaction medium. At this time, the fluoride film is separated and removed, and at the same time, the hard nitride layer is replaced and formed in the removed portion.

NF ₃ , BF ₃ , CF ₄ , HF, SF ₆ , F ₂ , CH ₂ F are used as the fluorine gas.
₂ , CH ₃ F, C ₂ F ₆ , WF ₆ , CHF ₃ , CHF ₃ , SiF _4, etc. At least one fluorine source component is contained in an inert gas such as N ₂ , among these. , NF ₃ is the best in terms of reactivity, handleability, etc. When this NF ₃ is used as the atmospheric gas, the temperature of the furnace accommodating the gears is heated to around 300 ° C. Then, NF ₃ generates fluorine as an active group, and this fluorine reacts with the metal on the surface of each gear to form an extremely thin fluoride film on the surface. This fluorinated film acts as a protective film below the fluorination treatment temperature, but has the property of acting as an active film when heated at a temperature higher than the fluorination treatment temperature.

Each of the gears on which the fluorinated film is formed is
About 150-200 from the conventional nitriding temperature of about 550-600 ° C. using a nitriding gas such as ammonia.
When heated at a low temperature of about 400 ° C, N atoms are adsorbed on the surface of the gear due to the action of the active fluorinated film, penetrate into the metal and diffuse, and as a result, nitride is formed on the surface layer of each gear. The contained hard nitride layer is formed.

The hard nitride layer thus formed is
It has excellent seizure resistance, abrasion resistance, and impact resistance that are the same as before. Since the nitriding treatment is performed at a much lower temperature than in the conventional case, it is possible to suppress dimensional accuracy deviation due to thermal deformation, excessive swelling of the dimension due to the nitride layer, and deterioration of the surface roughness as much as possible. Therefore, the meshing accuracy of the tooth surfaces of the gears to be combined is maintained as good as before nitriding treatment, and noise and abnormal wear during high-speed operation do not occur.

Before forming the fluoride film on each of the gears, these parts may be subjected to carburizing, induction hardening, flame hardening and other hardening treatments and tempering treatments in advance. Good. By this quenching treatment, a highly hard surface layer can be obtained over the deep layer portion of each gear. Also,
Depending on the type of hardened steel used as the base material, there is a risk that tempering brittleness of the base material may occur near the nitriding temperature of 400 ° C, but the tempering temperature after quenching should be an appropriate value above the nitriding temperature. By setting to, brittleness can be prevented.

In this embodiment, the nitride film is formed on the entire surface of the gear, but at least the nitride film may be formed only on the meshing contact surface of the gear teeth. In this case, it is necessary to mask the portion other than the contact surface.

Although the embodiments in which the present invention is applied to the gears used in the sewing machine have been described above, in addition to the gears made of metal used in all machines, any gears can be used. It goes without saying that the present invention can be applied.

[0022]

As is apparent from the above detailed description, according to the gear of the present invention and the method for manufacturing the same, at least the contact surface of the tooth of the metal gear that meshes with another gear is subjected to the fluorination treatment. In addition, since a nitride film is formed by nitriding that part, it is possible to minimize thermal deformation and swelling of the gear, and it is possible to maintain the same surface roughness as before processing. Therefore, noise due to deterioration of meshing accuracy can be prevented, and wear due to local load can be suppressed.

Further, prior to the fluorination treatment, the gear is subjected to quenching and tempering treatments to further harden the surface of the tooth surface and the deep portion of the surface layer, and to obtain the effect of improving wear resistance. it can.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a power transmission mechanism between an upper shaft and a lower shaft of an industrial lockstitch sewing machine of the present embodiment.

FIG. 2 is a configuration diagram of a power transmission mechanism between a lower shaft of a two-needle type industrial lockstitch sewing machine and a sewing machine hook of the present embodiment.

[Explanation of symbols]

 3 Upper shaft bevel gear 5 Vertical shaft bevel gear 6 Vertical shaft bevel gear 7 Lower shaft bevel gear 15 Spiral gear 16 Pinion gear

Claims (3)

[Claims] 1. A gear, characterized in that at least a contact surface of a tooth of a metal gear that meshes with another gear is subjected to a fluorination treatment, and the portion is subjected to a nitriding treatment to form a nitride film. 2. A metal gear, at least a contact portion of a tooth that meshes with another gear is heated in a fluorine-based gas atmosphere for a predetermined time to form a fluoride film on the surface of the portion, and thereafter, A method of manufacturing a gear, wherein the portion is heated in a nitriding gas atmosphere for a predetermined time to separate and remove the fluoride film, and at the same time, a nitride film is replaced and formed on the removed portion. 3. Prior to forming the fluoride film, the portion where the fluoride film is to be formed is subjected to quenching treatment such as carburizing quenching, induction hardening, flame quenching and tempering treatment. The method for manufacturing a gear according to claim 2, wherein: