JP4518589B2 - Resin molded two-stage gear - Google Patents

Description

[0001]
[Industrial application fields]
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 conventional resin molded gears, the meshing pitch of the molded gears is sparse or dense due to the manufacturing accuracy of the mold for molding the gears and uneven resin shrinkage after molding. Arise. Since the gear meshes and transmits on the pitch circle, the ratio of the density of the pitch to the circumference of the pitch circle appears as rotation unevenness of the gear.
As described above, the resin-molded gear has sparse or dense portions in the gear pitch in 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 part of the pitch is engaged, the rotation is slowed by the pitch error. If the differential angular velocity at that time is Δω, the total angular velocity is ω + Δω.
On the other hand, when the dense portion is engaged, the rotation is slow, and the total angular velocity is ω−Δω. Such a gear meshing error is transmitted to the photosensitive drum and causes image unevenness.
Therefore, in the prior art, there has been a problem that the manufacturing cost becomes high because the management means such as increasing the precision of the mold used for gear manufacture or increasing the cooling time at the time of molding is used.
[0003]
[Problems to be solved by the invention]
The present invention reduces the tooth pitch error that occurs at the time of molding of the gear causing the rotation unevenness of the rotating drum as described above, and obtains a highly accurate resin-molded two-stage gear at a low cost, thereby reducing the rotation unevenness of the rotating drum. The challenge is to make it happen.
[0004]
[Means for Solving the Problems]
In the present invention, when the driven side large gear and the driving side small gear are integrally formed, the driving side small gear is engaged when the sparse side or the dense side of the pitch error of the driven side large gear is engaged. By meshing the dense side or the sparse side, the rotation unevenness generated from the driven side large gear side and the rotation unevenness generated from the drive side small gear side are offset, and the precision of the mold and the control accuracy during molding are unnecessarily high. Even if it does not, the synthetic | combination rotation nonuniformity of the two-stage gear integrally molded can be reduced.
Therefore, the problem is solved by integrally forming the pitch error density positions of the driven large gear and the driving small gear in accordance with the positions that cancel each other.
[0005]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic diagram of the structure of a reduction gear with a two-stage gear sandwiched in between. 1 is a driving gear, 1-0 is the center, 2 is a two-stage gear, a driven large gear 2-1 and a driving small gear 2 -2 is integrally formed concentrically, 2-0 meshes with the center thereof, and the driving side small gear 2-2 meshes with the driven side gear 3 and 3-0 with the center thereof. The rotation is transmitted to 3.
[0006]
Here, the positional relationship between the center 1-0 of the driving side gear 1 and the center 3-0 of the driven side gear 3 is A degrees, and the tooth pitch between the driven side large gear 2-1 and the driving side small gear 2-2. The phase difference between the sparse and dense sides is B degrees (in FIG. 1, the dense side 2-3 of the driven large gear 2-1 and the dense side 2-4 of the driving side small gear 2-2 are The angle B between the center 2-0 and the center 2-0 is shown)), the ratio of fluctuation to the pitch circumference of the driven large gear 2-1 is K1, and the pitch circumference of the drive side small gear 2-2 is Assuming that the variation rate is K2, the synthesized variation rate K is
K = K1 · Sinθ + K2 · Sin (θ + AB)
Therefore, if the positional relationship of AB is set to 180 degrees, K1 and K2 are offset and the combined rotation unevenness can be reduced.
[0007]
In FIG. 1, the center 1-0 of the driving side gear 1, the center 3-0 of the driven side gear 3, and the center 2-0 of the two-stage gear 2 are predetermined positions determined by design. Since the angle A of the positional relationship between the motor and the driven gear 3 is a predetermined value, the angle B should be set to B = (A−180 degrees).
[0008]
Since the resin-molded gear is molded by a mold, it has been empirically known that the pitch error and the direction of density of the gear molded by the mold or conditions are almost constant. The pitch error and the direction of density of the -1 and the driving side small gear 2-2 are almost constant. Therefore, the driven side large gear 2-1 and the driving side small gear 2-2 may be integrally formed so that the angle at which the pitch error is sparse or dense is the angle B described above.
[0009]
As a result of configuring the resin-molded two-stage gear as described above, in the reduction gear configured to sandwich the resin-molded two-stage gear shown in FIG. 1, the meshing pitch error of the driven large gear of the resin-molded two-stage gear is reduced. When the sparse side or the dense side is engaged, it is formed so that the dense side or the sparse side of the meshing pitch error of the driving side small gear is engaged.
[0010]
FIG. 2 is a 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 the driven large gear and the driving small gear is large. Since it is generated with a phase difference of 180 degrees, the combined rotation unevenness is offset and reduced.
[0011]
【The invention's effect】
Since the resin-molded two-stage gear according to the present invention has the above-described configuration, the molding error is adjusted by aligning the pitch error density direction of each of the gears to a position where the density cancels. It is possible to obtain a resin-molded two-stage gear with less rotational unevenness at a low cost without increasing the accuracy and the control accuracy at the time of molding unnecessarily, so that the rotational unevenness of the rotating drum can be reduced.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a configuration of a resin-molded two-stage gear according to the present invention. FIG. 2 is a chart of measurement results of rotation unevenness of a resin-molded two-stage gear according to the present invention.
1 Drive Gear 1-0 Drive Gear Center 2 Resin Molded Two-Stage Gear 2-0 Resin Molded Two-Stage Gear Center 2-1 Resin Molded Drive Side Large Gear 2-2 Resin Molded Drive Side Small Gear 2-3 Resin Molded driven side large gear part 2-4 resin "Molded driving side small gear part pitch 3 driven side gear 3-0 Driven side gear center A The center of the driving gear and the driven gear Angle B formed by the center The angle formed by the sparse or dense part of the tooth pitch of the resin molding drive side small gear and the sparse or dense part of the tooth pitch of the driven side large gear.

Claims (1)

A gear mechanism of a laser beam printer or a laser beam copier that rotates a motor at a constant speed and decelerates a plurality of gears made of resin molding to rotate the motor and drives the photosensitive drum to rotate at a constant speed.
The gear, which constitutes a part of the gear mechanism, has a driven large gear that meshes with a driving gear rotated by the motor and a driving small gear that meshes with a driven gear in a two-stage shape vertically on the same center. In what is formed by integral molding,
When the sparse side or dense side of the meshing pitch error of the driven large gear of the two-stage gear is meshed with the driving gear, the dense side or sparse side of the meshing pitch error of the small driving gear is the driven side gear. A resin-molded two-stage gear characterized by being formed so as to mesh with each other .

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