JP2000329215A - Resin-molded two-stage gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the irregular rotation of a rotary drum by integrally molding a driven side large gear and a driving side small gear so that their pitch error coarse/dense positions are matched with offset positions. SOLUTION: The center 1-0 of a driving side gear 1, the center 3-0 of a driven side gear 3 and the center 2-0 of a two-stage gear 2 are located at predetermined positions set by design, the angle A indicating the positional relation between the driving side gear 1 and the driven side gear 3 is a predetermined value, and the angle B may be set to B=(A-180 deg.). This resin-molded gear is molded by a die, it is known that the pitch errors and coarse/dense direction of the gears molded by the die on certain conditions are nearly fixed, and the pitch errors and coarse/dense direction of a driven side large gear and a driving side small gear 2-2 are nearly fixed. The driven side large gear and the driving side small gear 202 may be integrally molded so that the angle of the position where their pitch errors become coarse or dense is made B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear mechanism for stably driving a photosensitive drum used in a color laser beam printer or the like.

[0002] In the conventional resin molded gear, the meshing pitch of the molded gear is sparse or dense due to the manufacturing accuracy of a mold for molding the gear and the unevenness of resin shrinkage after molding. Is generated. Since the gears engage and transmit on the pitch circle, the ratio of the pitch density to the circumference of the pitch circle appears as uneven rotation of the gear. As described above, the resin-molded gear may have sparse or dense portions in the gear pitch during one rotation due to the accuracy of the mold, molding conditions, and the like. When the gear is rotating at the average angular velocity ω, if the sparse portions of the pitch are engaged, the rotation is slowed by the pitch error, and if the differential angular velocity at that time is Δω, the total angular velocity is ω + Δω. On the other hand, when the dense portions are engaged, the rotation becomes slow, and the total angular velocity becomes ω-Δω. Such a meshing error of the gears is transmitted to the photosensitive drum and causes image unevenness. Therefore, in the prior art, the accuracy of the mold used for gear manufacturing is increased,
Since the control means such as lengthening the cooling time during molding was used, there was a problem that the production cost was increased.

[0003]

SUMMARY OF THE INVENTION The present invention provides a low-cost, high-precision, resin-formed two-stage gear by reducing the tooth pitch error that occurs during the molding of a gear, which causes the above-mentioned uneven rotation of the rotary drum. The problem is to reduce rotation unevenness of the rotating drum.

[0004]

According to the present invention, there is provided a two-stage gear in which a large driven gear and a small driving gear are integrally formed, and the sparse or dense side of the pitch error of the large driven gear is reduced. By engaging the dense side or the sparse side of the small drive side gear while meshing, the rotational unevenness generated from the driven large gear side and the rotational unevenness generated from the small drive side gear are offset, and the accuracy and molding of the mold are reduced. Even if the time management accuracy is not increased unnecessarily, the combined rotational unevenness of the integrally formed two-stage gear can be reduced. Therefore, the problem is solved by forming the driven large gear and the small driving gear in such a manner that the pitch error sparse and dense positions of the driven large gear and the driving small gear are offset from each other.

[0005]

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic diagram of a structure of a speed reducer having a two-stage gear interposed therebetween.
Is a driving gear, 1-0 is its center, 2 is a two-stage gear, and the driven large gear 2-1 and the driving small gear 2-2 are integrally formed concentrically. 2-0 is its center, the driving side. The small gear 2-2 meshes with the driven gears 3 and 3-0 at their centers, and transmits rotation from the driving gear 1 to the driven gear 3.

Here, the positional relationship between the center 1-0 of the driving gear 1 and the center 3-0 of the driven gear 3 is A degrees, and the driven large gear 2-1 and the driving small gear 2-2 The phase difference between the sparse side and the dense side of the tooth pitch is set to B degrees (in FIG. 1, the dense side 2-3 of the driven large gear 2-1 and the drive small gear 2-
The angle B between the dense side 2-4 and the center 2-0 is shown. If the ratio of the variation to the pitch circumference of the driven-side large gear 2-1 is K1, and the ratio of the variation to the pitch circumference of the driving-side small gear 2-2 is K2, the combined variation ratio K is K = K1 · Sin θ + K2 · Sin (θ + AB) Therefore, if the positional relationship between AB is set to 180 degrees, K1 and K2 are canceled out and combined rotation unevenness can be reduced.

In FIG. 1, the center 1-0 of the driving gear 1 is shown.
And the center 3-0 of the driven gear 3 and the center 2- of the two-stage gear 2
Since 0 is a predetermined position determined by design, the angle A of the positional relationship between the driving side gear 1 and the driven side gear 3 is a predetermined value, so that the angle of B is B = (A-180 degrees). ).

Since the resin-molded gear is molded by a mold, it has been empirically known that the pitch error and the direction of the density of the gear molded by a mold under a certain condition are almost constant. The pitch error between the large gear 2-1 and the drive-side small gear 2-2 and the direction of their density are substantially constant. Therefore, the driven-side large gear 2-1 and the driving-side small gear 2-2 may be integrally formed such that the angle of the position where the pitch error becomes sparse or dense becomes the angle B described above.

As a result of forming the two-stage resin-molded gear as described above, the reduction gear having the two-stage resin-molded gear shown in FIG. 1 meshes with the driven-side large gear of the two-stage resin-molded gear. When the sparse or dense side of the pitch error is engaged, the dense or sparse side of the meshing pitch error of the drive-side small gear is engaged.

FIG. 2 shows test data obtained by measuring the rotation unevenness of the driven large gear and the driving small gear of the two-stage gear formed as described above. The rotation unevenness of each of the driven large gear and the driving small gear is shown. Is large, but is generated with a phase difference of 180 degrees, so that the combined rotational unevenness is offset and reduced.

[0011]

Since the resin-molded two-stage gear according to the present invention has the above-described configuration, it is necessary to form the gears so that the pitch error direction of each constituent gear is adjusted to a position where the density cancels out. Accordingly, it is possible to obtain a low-cost and low-rotation resin-molded two-stage gear without unnecessarily increasing the accuracy of the mold and the control accuracy during molding, and thus has the effect of reducing the rotational unevenness of the rotary drum.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a configuration of a resin molded two-stage gear according to the present invention.

FIG. 2 is a table showing measurement results of rotation unevenness of a resin molded two-stage gear according to the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 Drive gear 1-0 Center of drive gear 2 Resin molded two-stage gear 2-0 Center of resin molded two-stage gear 2-1 Resin molded driven large gear 2-2 Resin molded drive small gear 2-3 Resin A portion where the pitch of the formed driven large gear is dense 2-4 A portion where the pitch of the formed driven small gear is dense 3 Driven gear 3-0 Center of driven gear A Center of driven gear and driven gear Angle formed by the center B The angle formed by the small or dense portion of the tooth pitch of the resin molding driving small gear and the small or dense portion of the tooth pitch of the driven large gear.

Claims (1)

[Claims] 1. A laser beam printer or laser beam copier for reducing the speed of a motor rotating at a constant speed and a plurality of gears formed by resin molding and rotating the photosensitive drum at a constant speed. Wherein the gear is integrally formed in a two-stage shape having a large gear on the driven side and a small gear on the driving side concentrically, wherein the meshing pitch error of the large gear on the driven side of the two-stage gear is reduced. A resin-molded two-stage gear, which is formed such that when the side or the dense side is meshed, the dense side or the sparse side of the meshing pitch error of the drive side small gear meshes.