Machine element or mechanism – Gearing – Teeth
Reexamination Certificate
1999-10-21
2001-08-21
Herrmann, Allan D. (Department: 3682)
Machine element or mechanism
Gearing
Teeth
Reexamination Certificate
active
06276226
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cycloidal gear, and in particular to a cycloidal gear with a small number of teeth, which is used as a pinion, or a small diameter gear, of a gear, or large diameter gear, and the pinion constituting a reduction gear mechanism.
2. Description of the Related Art
Conventionally, a gear with involute tooth has been used as a gear, and a gear train has been constituted by combining a gear with the involute tooth and a pinion therewith. When gear ratio is intended to be increased by reducing the tooth number of the pinion, undercut occurs at a deddendum of the pinion. As a method for solving the undercut, a shift method has been proposed, but, when the tooth number of the pinion is reduced, strength and durability thereof deteriorate remarkably. Therefore, the pinion is required to have six or more teeth in practical use. Assumed that the tooth number of a pinion is denoted by Z
1
and the tooth number of a gear is denoted by Z
2
, the gear ratio is represented by Z
2
/Z
1
.
On the other hand, a logix gear (for example, refer to Japanese Patent Application Publication (JP-B) No. 2-15743) has been developed in recent years. In the logix gear, a tooth has been formed by connecting a plurality of involute curves of micro-distances to one another in a continuously curved manner. For this reason, when the logix gear is used, the shape of a tooth can be designed in a various manner. According to this design, a pinion can be obtained which does not cause any problem regarding its strength even when the pinion has only four teeth, thereby making it possible to develop a gear train of a high gear ratio.
However, there occurs a problem that, when a gear or a pinion to which the logix gear is applied is designed, calculations for connecting a remarkable number of involute curves to one another continuously are repeated many times for various tooth shapes, so that much time is required to complete the design of the gear or the pinion.
SUMMARY OF THE INVENTION
In view of the above circumstances, the present invention has been attained, and an object thereof is to provide a cycloidal gear where a gear or pinion with a small number of teeth can easily be designed in a short time by using a cycloid tooth as a tooth profile of the gear.
In order to solve the above problem, the invention of a first aspect is a cycloidal gear with a small number of teeth, comprising: a tooth of cycloid tooth, wherein the number of teeth is four or five; and wherein the cycloidal gear with a small number of teeth meshes with a large gear with cycloid tooth to constitute a gear train.
The invention of a second aspect is a cycloidal gear according to the invention of the first aspect, wherein a tooth thickness ratio (T) calculated assuming a circle pitch as a denominator and a tooth thickness on the pitch circle as a numerator, is 0.655 to 0.741; epi-rolling circle radius (r1) is 3.5 to 6.5 mm/l module; hypo-rolling circle radius (r2) is 1.97 to 2.60 mm/l module; addendum height (h1) is 0.68 to 1.14 mm/l module; and deddendum height (h2) is 0.454 to 1.650 mm/l module.
In the invention of the first aspect, a gear or pinion constituted with four teeth can be formed which is practical and is usable to the same degree as the logix gear which has actual results with four teeth. For this reason, a gear or pinion with five or four teeth can be provided which can not be obtained by a gear or pinion with involute tooth. Accordingly, for example, when the gear or pinion of the invention of the first aspect is used as one gear or pinion in a reduction gear mechanism, a large reduction ratio can be obtained at once and the reduction gear mechanism can be reduced in size. Also, since a cycloid curve is used as the tooth of the gear, calculations for design are simplified and a gear or pinion with a desired number of teeth can be designed in a short time.
In the invention of the second aspect, the tooth thickness ratio (T) is set to 0.655 to 0.741, the epi-rolling circle radius (r1) is set to 3.5 to 6.5 mm/l module, the hypo-rolling circle radius (r2) is set to 1.97 to 2.60 mm/l module, the addendum height (h1) is set to 0.68 to 1.14 mm/l module, and the deddendum height (h2) is set to 0.454 to 1.650 mm/l module, so that, even when the tooth number of the gear or pinion is set to four or five, the meshing ratio of 1.0 or more can be secured and the deddendum strength of the gear can be secured sufficiently without occurrence of undercut and/or tip sharpening.
REFERENCES:
patent: 2666336 (1954-01-01), Hill et al.
patent: 4321839 (1982-03-01), Vuilleumier
patent: 4922781 (1990-05-01), Peiji
patent: 61-244966 (1986-10-01), None
Fujikiko Kabushiki Kaisha
Herrmann Allan D.
Kilpatrick & Stockton LLP
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