Enplas Corporation

Kenji Ohmi

Toru Murakami

Masaya Tsukamoto

Yasutaka Kawakami

A plastic helical gear has a three-dimensional tooth surface modification section on a tooth surface of each of involute-shaped teeth. The three-dimensional tooth surface modification section is a combined surface of a tooth top modification surface and an arc crowning surface. The tooth top modification surface is reduced in tooth thickness from a position between a tooth top and a tooth root toward the tooth top. The arc crowning surface is reduced in tooth thickness from a position between one end in the tooth width direction and the other end in the tooth width direction toward both ends in the tooth width direction. A line extending from an intersection point Pbetween the starting position of the tooth top modification surface and the apex position of the arc crowning surface to the tooth root is aligned with a line on the tooth surface of the involute-shaped tooth.

Plastic helical gear

A resin helical gear is formed by setting a first machining reference line obliquely coupling a tooth tip side of a first tooth to a tooth root side of a second tooth on another end side in the tooth width direction along a tooth surface, and a second machining reference line obliquely coupling a tooth tip side of the second tooth to a tooth root side of the first tooth along the tooth surface. Then, the tooth surface is cut out from the first machining reference line to the tooth root of the first tooth while the tooth surface is cut out from the second machining reference line to the tooth root of the second tooth. Then, an involute tooth profile form is left on a tooth tip side of the tooth with respect to the first machining reference line and the second machining reference line.

Resin helical gear

Provided is a fiber reinforced resin gear whose durability in use under a high temperature is enhanced. A fiber reinforced resin gear is formed by injecting a resin material containing glass wool into the inside of a cavity of a mold. A fiber diameter of the glass wool is scattered in a wide range of 0.1 to 15 &#x3bc;m, and is distributed such that a most frequent value of the fiber diameter appears within a range of 2 to 5 &#x3bc;m, and an average fiber diameter of the glass wool falls within a range of 3 to 5 &#x3bc;m. The fiber reinforced resin gear according to the present invention can enhance durability and abrasion resistance under a high temperature compared to a conventional fiber reinforced resin gear.

Fiber-reinforced resin gear

A gear includes teethto be engaged with teeth of a corresponding gear to transmit a rotational motion, in which a form (b) of a tooth root side of each toothincludes: a first curved surface c which smoothly connects with a tooth surface a having an involute curve and has a profile represented by a curve which is convex in a direction opposite to the involute curve of the tooth surface a; and a second curved surface d which smoothly connects with the first curved surface c and has a profile defined by a quadratic function having a curve being convex in the same direction as that of the first curved surface c. Therefore, a stress generated on the tooth root side at the time of engagement with the teeth of the corresponding gear can be reduced, and the strength of the teeth can be increased.

Gear and manufacturing method for the same

In a gear (G) according to the present invention, which is provided with a plurality of teeth () to be mated with teeth of a mating gear to thereby transmit a rotational motion, a predetermined region (A) in at least one tooth flank () of each tooth () is formed in a configuration such that, from at least one place in a tooth width direction on a crossing () of the tooth flank () and a tooth tip surface (), the mating with the teeth of the mating gear is started with the point contact or the line contact shorter than the total tooth width, and thereafter, is gradually shifted to the line contact so that the length of contact line () thereof is sequentially increased as the line contact moves from a tooth tip surface () side toward a tooth root side.

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Saitama, Japan

Kenji Ohmi