Precision gear, its gear mechanism, and production method of precision gear

Abstract

A metal-made high-precision gear and a gear mechanism are disclosed. The precision gear is made of a novel material which does not exist in conventional materials for precision gears, including resins and tool steels, has high hardness, strength and excellent surface smoothness, and is superior in workability. In the precision gear which is formed of an amorphous metal alloy having a ternary, quaternary or higher composition containing iron group elements, such as Fe, Co, Ni, and Cu, Ti, Zr, Hf, as the principal elements, the precision gear whose module is 0.2 or less is made of the amorphous metal alloy having a disordered structure which does not have a fixed regularity and whose XRD pattern is a halo pattern, namely exhibits a broad peak.

Description

TECHNICAL FIELD [0001] The present invention relates to a precision gear which is small-sized, subjected to a heavy load and required to have a long life-span, a gear mechanism employing the precision gear, and a method for manufacturing the precision gear. BACKGROUND OF THE INVENTION [0002] In the field of precision gears which are used in precision devices requiring high accuracy, such as watches and micro-geared motors, metal-made precision-gears whose modules exceed 0.2 and which have excellent properties and accuracy are manufactured by various methods including pressing and forming by rolling, as well as electro-discharge forming, cutting, etc. [0003] However, regarding forming of a metal-made gear whose module is 0.2 or less, it is difficult to practically employ the electro-discharge forming, cutting, pressing, and forming by rolling, since there are problems in terms of accuracy of the gear, manufacturing cost and the like. For this reason, resin-made precision-gears whose ...

AI Technical Summary

Benefits of technology

[0042] It is known that in the case where crystal particles having excellent toughness and ductility are mixed in the matrix of an amorphous metal, the mechanical characteristics are improved. In this case, the crystal size is preferably 20 nm or less. If the crystal size exceeds 100 nm, there is an adverse effect on surface roughness of a gear made of the metal material. Therefore, the crystal particles that are mixed in the amorphous metal matrix are preferably 100 nm or less in size.

[0043] Moreover, in the amorphous metal material, fragility increases with high hardness, and it is a known fact that this has a large adverse effect on resistance to gear surface fatigue such as pitting and the like. However, many of the precision gears of the preferred embodiments according to the present invention have excellent resistance to gear surface fatigue such as pitting and the like although they have high hardness, since the precision gears according to the present invention have low Young's module.

[0044] In order that this effect can be remarkably exhibited, it is preferable that the amount of non-metallic elements contained in the materials of the gears is 30 atomic percent or less. It has become clear that, if the amount of non-metallic elements is 25% or less, even in the hardest precision gear whose material contains Fe as the principal element thereof, bending strain to yield or breakage is 1.5% or more. This leads to the conclusion that it is possible to produce tough precision gears.

[0045] As discussed above, according to the present invention, there is provided a precision gear whose module is 0.2 or less, which is superior in dimensional accuracy, surface smoothness and mechanical properties as compared to the prior art gears, and which can be formed with a simple process.

[0046] In forming the precision gear of the present invention whose module is 0.2 or less, regardless of t

Problems solved by technology

However, regarding forming of a metal-made gear whose module is 0.2 or less, it is difficult to practically employ the electro-discharge forming, cutting, pressing, and forming by rolling, since there are problems in terms of accuracy of the gear, manufacturing cost and the like.

However, as compared to metal-made products, resin-molded integrated products are considerably inferior to the metal-made products in mechanical strength and hardness, tend to change in size and configuration thereof according to change in environmental temperature, and have creep properties.

Therefore, the resin-molding is completely unsatisfactory for forming an ultra-high-precision gear whose module is 0.2 or less and which is highly reliable.

In addition, as compared to the surface hardness and tensile strength of metallic material, those of resinous material are considerably low.

Moreover, the resinous material is inferior to the metallic material in heat resistance.

These properties of the resinous material have great adverse-effects on the durability and lifespan of the resin-molded product.

However, the present situation in the filed of the resinous materials does not yet reach the level of practical use of the metallic materials including tool steels.

However, the tensile strength of the alloys is about 750 MPa and is low like that of the resin materials.

In addition, the surface roughness of products made from the alloys is about 5 μm Ry and uneven shrinkage of the alloy products occurs du

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