JP2011197298A - Drive unit and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drive unit including a configuration allowing uniforming load distribution to every planetary gear, achieving high-precision drive without inhibiting an automatic aligning function by a planetary gear mechanism while achieving compactness, and allowing high-quality image output.SOLUTION: The drive unit includes a planetary gear deceleration mechanism 11 on a transmission route for transmitting a drive force from a drive motor M to a driven member 1. The planetary gear deceleration mechanism 11 includes at least one stage of carrier, and a planetary gear supported by the carrier. Output parts 101, 102 are provided to the carrier 18 of the last stage and are supported by only the carrier 18 during transmission of the drive force to the driven member 1.

Description

  The present invention relates to a drive device and an image forming apparatus, and more particularly to a transmission mechanism that uses a planetary gear mechanism in a drive transmission path for a detachable driven member.

  As is well known, in an image forming apparatus such as a copying machine, a printer, or a printing machine, an electrostatic latent image formed on a photosensitive member, which is a latent image carrier, is visualized by a developer supplied from a developing device. It is processed. The image subjected to the visible image processing is transferred to a recording paper or the like and fixed to be output as a copy.

  In an image forming apparatus such as an electrophotographic copying machine or printer, an electrostatic latent image is formed on the surface of a rotating cylindrical image carrier (hereinafter referred to as a photosensitive drum), and toner is applied to the formed electrostatic latent image. The toner image is transferred to the endless belt (hereinafter referred to as a transfer belt) and then transferred onto the recording paper and fixed to obtain an image.

  Here, when a speed fluctuation occurs in the photosensitive drum that should rotate at a constant speed with high accuracy or a transfer belt that should be transported at a constant speed, jitter and density unevenness occur in the output image. When the speed fluctuation continues at a certain frequency, the periodic density unevenness occurs in the entire image, which is visually observed as a banded banding. Variation in the speed of the photosensitive drum causes a sub-scanning position shift of the exposure line of the writing system. At the same time, a sub-scanning position shift at the time of primary transfer to the transfer belt is generated. The speed fluctuation of the transfer belt causes a sub-scanning position shift between the primary transfer and the secondary transfer. Image quality is significantly degraded by banding due to this speed variation.

  On the other hand, the photosensitive drum and the transfer belt need to be detachable from the apparatus frame of the image forming apparatus for replacement and maintenance. In other words, the photosensitive drum is a consumable product because the photosensitive layer on the surface is worn away over time, and maintenance and replacement are required according to the cumulative print amount.

In addition, the transfer belt is a consumable item because scratches on the surface and cracks from the end portion are generated with the passage of time, and maintenance and replacement are required in accordance with deterioration or breakage of print quality.
Accordingly, the photosensitive drum and the transfer belt are configured to be detachable from the apparatus frame of the image forming apparatus, and are coupled to a driving mechanism such as a motor and a reduction gear train when the apparatus is mounted on the apparatus frame. It has become.

On the other hand, in recent image forming apparatuses, space-saving (reduction of occupied floor area) and miniaturization (reduction of occupied volume) of the image forming apparatus are required due to changes in the usage environment from the floor to the desk top.
The image forming apparatus is composed of many roller members as surface moving bodies such as a photosensitive drum and a transfer belt conveying roller, and the ratio of the driving mechanism such as a motor and a gear for driving the roller members in the apparatus is large. Further, in a tandem type color image forming apparatus that can obtain an output speed comparable to that of a monochrome image, the proportion of the driving mechanism in the apparatus is increasing. For example, a driving mechanism is required for each of the four color photosensitive members.

  However, the conveyance roller of the photosensitive drum or transfer belt has a circumferential length in the surface movement direction and a length in the width direction perpendicular to the surface movement direction, which are determined by the purpose of use such as the number of output sheets and the size of the image forming paper Therefore, it is difficult to make the photosensitive drum and the transfer belt itself small. Therefore, in order to reduce the size of the image forming apparatus, it is desired to reduce the size of the driving mechanism of the surface moving body driving device.

Conventionally, in response to such a problem, by adopting a planetary gear mechanism, the load is distributed to a plurality of planetary gears according to the number of planets in order to branch and transmit the load to a plurality of planetary gears. Can be miniaturized. A miniaturized driving mechanism and a motor as a driving source are arranged inside a roller member cylinder which is a conveyance roller for a photosensitive drum or a transfer belt, and a configuration that realizes a significant miniaturization has been proposed ( For example, Patent Document 1).
Patent Document 1 adopts a planetary gear mechanism to branch and transmit loads to a plurality of planetary gears, so that the load to each gear meshing portion is distributed according to the number of planets and the gears are downsized. Possible configurations are disclosed.
According to this configuration, the miniaturized driving mechanism and the motor as the driving source are arranged inside the cylinder of the roller member that is the conveying roller of the photosensitive drum or the transfer belt, so that a significant reduction in size can be realized. Further, since the roller member is configured to be detachable from the motor fixed to the side plate and the driving mechanism, the roller member can be easily replaced and maintained.

On the other hand, as described above, the transmission path that transmits power using the planetary gear mechanism in the image forming apparatus includes parts and devices that need to be replaced. It is provided as possible.
When such a member to be attached / detached is attached to the apparatus main body, the above-described problem, that is, banding due to rotation unevenness, occurs if the positional accuracy between the power input side and the output side is not secured.
For this reason, the structure which provides a coupling in the part connected in a power transmission path | route conventionally is proposed (for example, patent document 2).

  However, in the drive device disclosed in Patent Document 1, rotational accuracy is caused by manufacturing errors such as eccentricity of each gear, accumulated tooth pitch error, assembly error, and coaxial error with the motor shaft when the roller member is mounted on the drive mechanism. However, there is a problem that greatly decreases. The reason for this is that the load distribution of each planetary gear becomes uneven due to the manufacturing error and assembly error of each gear, and the coaxial error of the roller member, and the load distribution state changes with rotation, so that rotation fluctuation is likely to occur. It is.

  On the other hand, in the configuration disclosed in Patent Document 2, the eccentricity and the declination between the two axes are absorbed by the coupling so that transmission is possible even if there is a misalignment of the axial center position due to the decentering or declination. On the other hand, if a planetary gear mechanism is used for the drive device, it may be difficult to exhibit the self-aligning function of the planetary gear mechanism. The reason for this is that the self-aligning function by the planetary gear mechanism divides the load to a plurality of planetary gears and transmits it, so that the load on each gear meshing portion is distributed according to the number of planets. In other words, even if eccentricity occurs between the input side and the output side, the output side carrier that supports the planetary gear is caused to be eccentric so that the load acting on the planetary gear is equalized, thereby causing the input side and the output side to be eccentric. However, this action requires a mechanism that prevents the load from acting on the output side. Therefore, the photosensitive member that is the driven member to be replaced, and the process mechanism associated therewith. In practice, the self-aligning function described above cannot be effectively obtained.

  An object of the present invention is to solve the problems in the conventional drive device described above, and can uniformly distribute the load to each planetary gear, and while achieving downsizing, inhibits the self-aligning function by the planetary gear mechanism. It is an object of the present invention to provide a driving apparatus and an image forming apparatus having a configuration capable of achieving high-precision driving without any problem and enabling high-quality image output.

In order to achieve the above object, the present invention comprises the following arrangement.
(1) In a drive device including a planetary gear reduction mechanism in a transmission path for transmitting a drive force from a drive motor to a driven member,
The planetary gear speed reduction mechanism is provided with at least one stage carrier and a planetary gear supported by the carrier, and an output section is provided on the last stage carrier,
The output device includes a configuration in which the output unit is supported only by the carrier when the driving force is transmitted to the driven member.

(2) The output portion is provided with a coupling member that engages with an engaging portion formed on the last stage carrier or an output shaft integrated with the carrier (1). ) Drive device.

(3) The drive unit according to (1), wherein the output unit is detachably attached to the carrier.

(4) The output unit is supported only by the carrier without using a bearing with respect to a driven member supported by using a bearing, as described in (1) or (2) Drive device.

(5) The drive unit according to any one of (1) to (3), wherein the output unit includes a drop-off prevention unit during attachment / detachment.

(6) In one of (1) to (5), the carrier and the output unit are coupled using an uneven spline having a longitudinal direction in a direction perpendicular to the rotation direction. The drive device described.

(7) The drive unit according to (6), wherein the drop-off prevention member is provided in the spline coupling portion.

(8) The carrier output unit is housed in a detachable unit, and an input shaft of a driven member is detachably provided to the output unit in the unit. The drive device according to 6) or (7).

(9) An image forming apparatus using the driving device according to any one of (1) to (8), wherein the driving device is used for each of a plurality of driven members. Image forming apparatus.

  According to the present invention, the output portion provided in the last stage carrier in the planetary gear mechanism is supported not by the bearing support but by the carrier as in the driven member. As a result, since the output portion is supported in a floating state, not supported by a bearing or the like, the load on the output portion of the planetary gear mechanism can be reduced. As a result, since the self-aligning function by the planetary gear mechanism is not impaired, it is possible to prevent a decrease in power transmission efficiency due to a positional deviation between the output unit and a driven member that receives power transmission from the output unit.

1 is an external view showing an example of an image forming apparatus to which a latent image carrier, which is a driven member including a driving device according to the present invention, is applied. It is a figure which shows 1st Example regarding the principal part structure of the drive device by this invention. It is a figure which shows the one aspect | mode of the principal part structure shown in FIG. It is a figure for demonstrating the displacement state of the carrier in a planetary gear mechanism. It is a diagram which shows the experimental result regarding the torque fluctuation at the time of making the shaft support structure using a bearing into object. It is a diagram which shows the experimental result regarding the torque fluctuation at the time of considering the floating support structure which does not use a bearing. It is a figure which shows the comparison result regarding the rotational vibration with the case of the floating support structure by the Example of this invention, and the case where a bearing is used. It is a schematic diagram which shows the connection relationship of the internal tooth which becomes a female side, and the external tooth which becomes a male side in the involute tooth profile used for a spline connection part. It is a table | surface figure which shows the gear specification of the involute tooth profile shown in FIG. It is a mimetic diagram of a spline transmission part at the time of setting a distance between meshing part centers by axis angle setting. It is a schematic diagram for demonstrating the rotation state of the carrier and drum flange which were connected by the inclined spline transmission member. It is a figure which shows 2nd Example of the drive device by this invention. It is a figure which shows the state which attaches the common positioning unit in the drive device shown in FIG. 12 according to the reference position of a main body side plate. It is a figure for demonstrating the structure in the case of attaching the common positioning unit used for the drive device shown in FIG. 12 to an image forming apparatus. It is a figure for demonstrating the state at the time of the attachment or detachment of the driven member in the drive device shown in FIG. 12, and the state of the drop-off prevention member at this time. It is a figure which shows the detail of the spline tooth | gear of the spline transmission member used for the drive device shown in FIG. It is an expanded view of the tooth | gear shown in FIG. It is a figure which shows the structure of the spline transmission member used for the drive device shown in FIG.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is a view showing an image forming apparatus provided with a latent image carrier which is a driven member using a driving apparatus according to the present invention.
FIG. 1 shows an electrophotographic color copying machine using a tandem method, and an electrostatic latent image is subjected to visible image processing by a two-component developing method using a dry two-component developer. . Although the embodiment of the present invention is intended for a copying machine, the present invention is not limited to this, and it is also possible to target a printer, a facsimile machine, a printing machine, or a complex machine that combines these functions. .

The copier shown in FIG. 1 receives image data as image information from an image reading unit (not shown) and performs image forming processing. In this copying machine, as shown in the drawing, yellow (hereinafter abbreviated as “Y”), magenta (hereinafter abbreviated as “M”), cyan (hereinafter abbreviated as “C”). , Black (hereinafter abbreviated as “Bk”), photosensitive drums 1Y, 1M, 1C, and 1Bk, which are latent image carriers as four rotating bodies for each color, are arranged side by side. These photosensitive drums 1Y, 1M, 1C, and 1Bk are arranged along the belt moving direction so as to contact the endless belt-shaped intermediate transfer belt 5 supported by a plurality of rotatable rollers including a driving roller. Has been placed.
Further, around the photosensitive drums 1Y, 1M, 1C, and 1Bk, chargers 2Y, 2M, 2C, and 2Bk, developing devices 9Y, 9M, 9C, and 9Bk corresponding to the respective colors, and cleaning devices 4Y, 4M, 4C, and 4B, respectively. Electrophotographic process members such as 4Bk and static elimination lamps 3Y, 3M, 3C, and 3Bk are arranged in the order of processes.

When a full-color image is formed by the copying machine shown in the present embodiment, the photosensitive drum 1Y is uniformly charged by the charger 2Y while being driven to rotate in the direction of the arrow in the drawing by a photosensitive drum driving device to be described later. The Y electrostatic latent image is formed on the photosensitive drum 1Y by irradiating the light beam LY from the optical writing device that does not.
This Y electrostatic latent image is developed with Y toner in the developer by the developing device 9Y. During development, a predetermined developing bias is applied between the developing roller and the photosensitive drum 1Y, and the Y toner on the developing roller is electrostatically attracted to the Y electrostatic latent image portion on the photosensitive drum 1Y.

The Y toner image developed and formed in this way is conveyed to a primary transfer position where the photosensitive drum 1Y and the intermediate transfer belt 5 come into contact with the rotation of the photosensitive drum 1Y. At the primary transfer position, a predetermined bias voltage is applied to the back surface of the intermediate transfer belt 5 by the primary transfer roller 6Y. The Y toner image on the photosensitive drum 1Y is drawn toward the intermediate transfer belt 5 by the primary transfer electric field generated by this bias application, and is primarily transferred onto the intermediate transfer belt 5.
Thereafter, similarly, the M toner image, the C toner image, and the Bk toner image are also primarily transferred so as to sequentially overlap the Y toner image on the intermediate transfer belt 5.

  As described above, the toner images having the four colors superimposed on the intermediate transfer belt 5 are conveyed to the secondary transfer position facing the secondary transfer roller 7 as the intermediate transfer belt 5 rotates. Further, the transfer paper is conveyed to the secondary transfer position at a predetermined timing by a registration roller (not shown). At this secondary transfer position, a predetermined bias voltage is applied to the back surface of the transfer paper by the secondary transfer roller 7, and due to the secondary transfer electric field generated by the bias application and the contact pressure at the secondary transfer position, The toner image on the intermediate transfer belt 5 is secondarily transferred onto the transfer paper at once. Thereafter, the transfer paper on which the toner image is secondarily transferred is subjected to fixing processing by the fixing roller pair 8 and then discharged outside the apparatus.

The features of the present invention will be described below for the image forming apparatus having the above configuration.
A feature of the present invention is that the driving device uses a photosensitive drum as a driven member. Specifically, as a support structure of the output portion of the planetary gear speed reduction mechanism used in the driving device, movement in the radial direction by a bearing is performed. This is not a restricted support, but a floating support structure that can move freely in the radial direction and the thrust direction.

FIG. 2 is a diagram showing a first embodiment of the present invention. Before explaining the floating support structure in FIG. 2, the configuration of the drum driving device 10 mentioned as the first embodiment will be described as follows. .
FIG. 2 is a diagram showing a configuration of a drum driving device 10 having a planetary gear mechanism 11 equipped with a two-stage planetary gear (pinion gear) and a carrier supporting the planetary gear as a main part.
In FIG. 2, the planetary gear mechanism 11 includes a sun gear 12 integrated with the input shaft M1 of the planetary gear mechanism provided on the output shaft M1 of the drive motor M, and the internal gears of the sun gear 12 and the fixed casing 13 are provided. A first stage planetary gear 14 meshing with the gear 13 </ b> A is supported by a first stage carrier 15 and revolves around the outer periphery of the sun gear 12.

The first-stage carrier 15 is provided with a second-stage sun gear 16 corresponding to the final stage in this embodiment, and the second-stage sun gear 16 meshes with the internal gear 13A of the casing 13 2. The stage planetary gear 17 is supported by the second stage carrier 17 and revolves around the outer periphery of the second stage sun gear 16.
The second-stage carrier 18 corresponding to the final stage is provided with an output portion, and in the case shown in FIG. 2, the engagement with the spline-shaped inner teeth 19 </ b> A formed on the inner surface of the cylindrical shaft 19. A spline transmission member 20 which is a combined member is used as the output unit.
The output shaft M1 of the drive motor M described above is supported by the motor fixing flange 21 via two bearings M2.
By supporting the rotating shaft M1 of the motor M, the outer rotor that is the rotor of the DC brushless motor is supported. The motor fixing flange 21 is provided with a motor stator core, a drive circuit, and the like (not shown).
The motor fixing flange 21 is fixed to the casing 13 having the internal gear 13A by screws.

The casing 13 has a thickness of about 10 mm from the bottom of the inner teeth to the outer diameter so as to have sufficient strength. A sun gear is formed by gear cutting on the rotating shaft of the motor, and the internal gear and the motor fixing flange are positioned by fitting with an inlay to ensure coaxial accuracy between the sun gear shaft and the internal gear shaft. Has been.
An end cap 22 is fastened to the end of the casing 13 opposite to the motor fixing flange 21 by a screw inserted through the apparatus main body.

  When the planetary reduction mechanism is assembled to the main body side plate, the end cap 22 includes the planetary gears 14 and 17 carriers 15 and 18 installed in the internal gear 13A of the casing 13 and a spline transmission member 20 to be described later. This is used as a member for preventing the internal gear 13A from falling off.

A drum flange 1A is fixed to an end of a photosensitive drum (denoted by reference numeral 1 used in FIG. 1 for convenience) as a driven member, and rotates integrally with the photosensitive drum 1. .
The drum flange 1 </ b> A is rotatably supported by a drum bearing 1 </ b> B installed in the photosensitive drum unit DY that houses the photosensitive drum 1. The photosensitive drum unit DY can be attached to and detached from the main body side plate 50. When the photosensitive drum unit DY is attached, the photosensitive drum unit DY is guided to a predetermined place by a race guide (not shown).

  The main body side plate 50 is provided with a shallow fitting portion 50A into which the drum bearing 1B is inserted, and the position of the photosensitive drum unit DY is determined at two positions of a positioning pin (not shown). The support portion of the drum bearing 1 </ b> B and the main body side plate 50 are fitted with an inlay to ensure coaxial accuracy between the photosensitive drum 1 and the planetary gear mechanism in the drum driving device 10.

The planetary gear mechanism used in the drum driving device 10 shown in FIG. 2 is a 2K-H two-stage planetary gear mechanism, and its basic configuration is as follows.
The input shaft M1 connected to the motor M has a sun gear 12 at one end, and the first stage planetary gear 14 meshing with the input shaft M1 revolves around the sun gear 12 supported by a carrier. Two or more planetary gears 14 are arranged concentrically for rotational balance and torque sharing.
In the present embodiment, planetary gears are arranged at positions equally divided into three in the circumferential direction, and the outer peripheral orbits of the planetary gears rotate in mesh with the fixed and non-rotatable internal gear 13A.
The planetary gear 14 rotates and revolves by meshing with the sun gear 12 and the internal gear 13A, and the carrier 15 that supports the planetary gear 14 rotates at a reduced speed with respect to the rotation of the sun gear 12, and the first stage. Reduction ratio is acquired.

Next, the sun gear 16 provided at the center of rotation of the carrier 15 serves as an input to the second stage reduction mechanism. The first-stage sun gear 12 and the second-stage sun gear 16 are supported (floating support) and rotated by two rotation support portions S1 and S2 having a clearance.
Similarly, the planetary gear 17 provided on the second-stage carrier 18 is further decelerated and rotated by the meshing rotation with the fixed internal gear 13A common to the first stage described above on the outer circumference orbit. The rotation of the stage carrier 18, that is, the rotation on the output side.
One unit used in the 2K-H type planetary gear mechanism includes a sun gear, a planetary gear, a planetary carrier that supports the revolving motion of the planetary gear, and an outer gear. ) 4 parts.
Of the three elements of sun gear rotation, planetary gear revolution (carrier rotation), and outer ring gear rotation, one is fixed, one is input, and one is connected to the output. Depending on which one is assigned to input / output / fixed, multiple reduction ratios and rotation directions can be switched with one unit. The target 2K-H type two-stage structure in this embodiment is classified into compound planetary gear mechanisms (two or more 2K-H types), and each of the three basics of two or more 2K-H types. The two basic shafts of the shafts are connected to each other, one of the remaining basic shafts is fixed, and the other one shaft is used as a drive shaft or a driven shaft.

The linear speed ratio that affects the reduction ratio is expressed by the following equation when the number of teeth of the sun gear is Za, the number of teeth of the planetary gear is Zb, and the number of teeth of the internal gear is Zc. The subscripts 1 and 2 in the formula mean the first and second stages.
Linear speed ratio = Za1 / (Za1 + Zc1) × Za2 / (Za2 + Zc2)

On the other hand, the spline transmission means 20 used in the output unit located at the final stage of the planetary gear mechanism is supported only by the carrier 18, that is, without using the bearing member 1B1 used for the photosensitive drum 1. It can move freely in the thrust direction and radial direction. Hereinafter, this configuration will be described.
As described above, the spline-like inner teeth 19A formed in the cylindrical shaft 19 are positioned on the second-stage carrier 18 as the final stage, and also on the drum flange 1A side of the photosensitive drum 1. Similar spline-like internal teeth 1A1 are formed.
The spline transmission member 20 is adapted to transmit power from the planetary gear mechanism 11 by meshing with the internal teeth 19A, 1A1 described above.

  Since the fitting portion between the spline transmission member 20 and the internal teeth 19A, 1A1 has a spline shape, the carrier 18 can be simply pulled out from the main body side plate 50 in the axial direction of the photosensitive drum as shown in FIG. The connecting portion corresponding to the side and the photosensitive drum shaft (the portion having the internal teeth 1A1) can be disconnected. That is, the spline transmission member 20 used as the output unit corresponds to a member that can be easily attached to and detached from the carrier 28.

  The spline transmission member 20 is formed with a disk-shaped drop-off prevention protrusion 23, and when the photosensitive drum unit DY is pulled out, the spline transmission member 20 comes off together with the drum flange 1A and falls off, and the carrier 18 on the output side. Prevents the planetary gear from dropping off due to the axial movement.

The spline transmission member 20 is provided in the spline-shaped inner teeth 19A of the carrier 18 on the output unit side so that the spline fitting portion can be connected and disconnected more smoothly when the photosensitive drum unit DY is attached / detached. A biasing spring (not shown) may be installed in the gap G between the two.
In the present embodiment, the input-side carrier 15, the output-side carrier 18, and the spline transmission member 20 rotate, but a bearing that restricts the rotational position is not provided.
Thus, by not using a bearing, the rotation support portions S1 and S2 are provided for restricting the rotation region so that the gear portions are not disengaged.
With this configuration, in this embodiment, only the input shaft M1 that is a motor output and the photosensitive drum flange 1A are rotatably supported by the bearings.

  The tooth profile of the external teeth of the spline transmission member 20 and the internal teeth on the carrier 18 side and the drum flange 1A side is reduced by a tooth thickness so that a backlash of about 0.1 mm is secured at the meshing portion, or minus on the external tooth side. It is formed by dislocations. By this backlash, the output-side carrier can move on a skew or a plane perpendicular to the axis with respect to the drum axis.

In the present embodiment, the following operation is obtained in the floating support structure of the output unit using the above-described configuration.
Usually, in a gear pair that meshes two gears formed in an involute tooth profile, force is generated not only in the gear rotation direction but also in the gear rotation center direction according to the meshing pressure angle of the meshing portion. Therefore, a bearing that supports the rotation of the gear is essential.
However, in the planetary gear mechanism, by arranging the planetary gears uniformly, the meshing portions of the gears are positioned symmetrically with respect to the rotation center, so that the force in the direction of the gear rotation center is canceled out.
Therefore, the carrier having the rotation axis of the planetary gear does not support the planetary gear, but is a member that transmits the force that the planetary gear moves on the revolution orbit, and the planetary gear is symmetrical with respect to the carrier center. A rotating support bearing is not required. That is, a floating support configuration in which the spline transmission member 20 indirectly supports it as in this embodiment is possible.

The carrier moves to the center of the planetary gear mechanism and stabilizes when a load torque is applied even in a floating support state. However, strictly speaking, it moves a minute distance near the center. This occurs due to eccentricity of each gear and mounting errors.
FIG. 4 shows the locus of the carrier center axis when the planetary gear is eccentric in the carrier floating support configuration. It is a movement locus of the carrier central axis when each of the three planetary gears used in the present embodiment has an eccentricity of about 30 μm. The amount of movement of the center axis of the speed reducer in the horizontal direction is plotted on the X axis, and the vertical direction is plotted on the Y axis. When the planetary gear is eccentric, it has been found that the carrier central axis moves in a region with a radius of about 40 μm as shown in FIG.

The carrier floating support mechanism greatly contributes to improving the rotation accuracy of the output shaft of the planetary gear reduction mechanism.
FIGS. 5A and 6A show a case where the carrier rotating shaft is supported by a ball bearing (hereinafter referred to as carrier bearing support) when the planetary gear is eccentric in this embodiment. The tooth pair torque and the rotation characteristics of the planetary gear when the carrier is floated and supported are shown.
FIG. 5A shows a time transition of torque applied to the meshing portion of each planetary gear (hereinafter referred to as tooth-to-torque) in a configuration in which the carrier rotation shaft is supported by a ball bearing.
If the planetary gear is eccentric, depending on the eccentric phase, the meshing may start before the meshing of other planetary gears, or the meshing may be delayed.
As a result, as shown in FIG. 5 (A), in the time period from 0.1 to 0.18 seconds, the second planetary gear starts meshing ahead of the other planetary gears, and the load torque is large. . In particular, in the time period from 0.11 seconds to 0.17 seconds, only the 2nd planetary gear contributes to torque transmission, and the other 1st and 3rd planetary gears do not contribute to torque transmission. Since the eccentric phase changes with the rotation of the planetary gear, the planetary gear that greatly contributes to torque transmission moves from No. 2 to No. 3, No. 1. Thus, the tooth-to-torque torque applied to each planetary gear varies greatly from the eccentricity of the planetary gear.

On the other hand, FIG. 6 (A) shows the change in the tooth-to-torque of each planetary gear in the configuration of the present embodiment in which the rotation shaft of the carrier is supported floatingly.
Although the tooth-to-torque of each planetary gear fluctuates due to the eccentric phase of the planetary gear, it is almost constant and stable. This is because in each planetary gear, the carrier automatically moves so that the tooth-pair torque is equally applied. The movement trajectory of the carrier is the state described in FIG.

Next, FIG. 5 (B) and FIG. 6 (B) show the carrier when the planetary gear is eccentric in the present embodiment when the carrier bearing is supported and when the carrier is supported as in the present embodiment. The frequency analysis result of the speed fluctuation rate of output rotation is shown.
In the carrier bearing support of FIG. 5 (B), it can be seen that the rotational speed fluctuation occurs in the rotation period of the planetary gear (planetary gear rotation period) and its higher order components as viewed from above the carrier. The speed fluctuation in the vicinity of 220 Hz is the rotational fluctuation of the meshing cycle of one tooth pitch.

  On the other hand, in the carrier floating support of FIG. 6B, the tooth-to-torque fluctuation is greatly reduced by the automatic alignment of the carrier, so that the rotational speed fluctuation is also greatly reduced. In addition, the rotational fluctuation of the meshing period of one tooth pitch in the vicinity of 220 Hz is greatly reduced, and it can be seen that the rotational accuracy of the speed reducer is greatly improved.

As described above, focusing on the eccentricity of the planetary gear, the improvement of the rotation accuracy by the carrier floating support has been described, but it is also effective for the sun gear and the fixed internal gear.
FIG. 7 shows the effect of reducing the speed fluctuation rate by the carrier floating support in the rotation period of each component. The carrier floating support has an effect of reducing the speed fluctuation of the solar rotation period even when the sun gear is eccentric (solar rotation in FIG. 7).
When the fixed internal gear has an eccentricity or an installation error, a speed fluctuation occurs in the rotation cycle of the carrier rotating with respect to the fixed internal gear, and this also has an effect of reducing by the carrier floating support (FIG. 7). Inside carrier rotation). The fluctuation effect of the planetary gear rotation period is confirmed to be reduced under most assembly conditions (planetary rotation 1 in FIG. 7).
However, depending on the assembling conditions, there are cases where almost no reduction effect is obtained (planetary rotation 2 in FIG. 7). The assembling condition where the effect cannot be obtained is a state where the maximum eccentric phase of each planetary gear is radially arranged with respect to the sun axis.
When the eccentric phases of the planetary gears are radially arranged and assembled, the three gears mesh with the sun gear and the internal gear with the same eccentric phase, so that the tooth-to-torque torque is as shown in FIG. 6 (A). Although the gears are uniform, the rotation speed fluctuation of the carrier occurs according to the amount of eccentricity of the planetary gear.

By the way, even in carrier floating support, fluctuations in the planetary rotation period may not be reduced.
Therefore, in this embodiment, as a method for coping with the occurrence of such fluctuations, a photosensitive drum that moves the arrangement interval between the latent image writing unit and the primary transfer unit on the photosensitive drum in a planetary gear rotation period. Integer multiple of surface travel distance.
As a result, the writing position shift caused by the fluctuation in the rotational speed of the photosensitive drum during the rotation of the planetary gear during writing of the latent image has an opposite relationship during the transfer and is canceled.

Next, the detail of a structure of the spline transmission member 2 is demonstrated.
An involute spline-shaped gear coupling is optimal as a coupling that transmits rotation in a configuration in which the carrier floats. As other coupling methods, pin fitting and Oldham shape fitting can be considered, but the involute spline shape is excellent in the following points.
First, there are effects that the photosensitive drum is easy to attach and detach, the reaction force in the moving direction accompanying the self-aligning movement of the carrier is small, and the frictional force during the self-aligning movement of the carrier is small.

  That is, since it has a spline shape, it is easy to attach and detach the photosensitive drum unit in the rotation axis direction. Further, in the involute spline-shaped gear coupling, the spline transmission member moves to the center by the tooth-pair torque of the meshing spline teeth of the entire circumference. A force is required to move the spline transmission member from the center in the direction of the vertical axis of the rotation axis, and a reaction force is also generated.

  However, a gap (backlash) exists in the meshing portion in order to secure detachability, and the backlash can be moved with a small force in the movement and inclination of the backlash. Backlash is ensured by dislocation of involute teeth and reduction of tooth thickness. In this embodiment, in view of this point, the backlash is manufactured to be about 150 μm.

On the other hand, since the carrier moving area is 100 μm or less, the carrier can be automatically aligned. In this embodiment, since it is used for driving a photosensitive drum that requires high rotational accuracy, each gear is manufactured with high accuracy in accordance with JIS standard N7 class or less, and the eccentric amount of each gear is about 20 μm. is there. Therefore, the actual carrier movement region was within a circle with a radius of 50 μm.
In the present embodiment, the spline coupling portion with respect to the spline transmission member 20 is set in two stages of the internal teeth 19A of the cylindrical shaft 19 corresponding to the internal teeth on the carrier 18 side and the internal teeth 1A1 of the drum shaft, whereby the shaft center is set. Even in the case of fitting while tilting, rotation is transmitted with high accuracy. The reason will be described below.

  FIG. 8 shows the inner teeth on the female side (indicated by reference numerals 19A and 1A1 in FIG. 2) and the outer side on the male side among the inner teeth having the involute tooth profile applied to the spline transmission member 20 in this embodiment. The relationship with the teeth (the teeth of the spline transmission member 2) is shown. In this embodiment, the external teeth of the spline transmission member 20 on the male side are barrel-shaped external gears.

The gear specifications on the male side and female side of the spline connecting portion are as shown in FIG.
Generally, in an involute tooth-shaped spline joint or serration joint, a tooth pressure angle of 25 to 45 ° is used, but in this embodiment, the pressure angle is set to 20 °. This is because by lowering the pressure angle, the meshing pressure in the center direction acting on the male gear is reduced, and the fluctuation of the shaft angle of the spline transmission member is facilitated. Further, even when the same torque is transmitted, the tooth surface contact pressure is reduced, so that there is an advantage that the transmission rigidity is high.

In this embodiment, the normal tooth thickness reduction amount is set to 40 μm or more. In the spline connecting portion, the tooth gap corresponding to the tooth backlash is 80-100 μm when the material used for the spline connecting portion is cut with metal, and the material used for the spline connecting portion is resin injection molding. In this case, the thickness is 80 to 150 μm.
As shown in FIG. 10, the spline transmission member 20 can change the shaft angle in the tooth gap. In FIG. 8, the male axis that is the external gear is Xe, the female axis that is the internal gear is Xi, and the male side is inclined with respect to the female side by an axial angle δ around the fitting center Op. It shows that.
In this embodiment, since the tooth surface gap is set to 80 μm or more and the tooth width is set to 10 mm, the shaft angle variation δ can be inclined to about 0.5 °.

However, if the shaft angle variation δ is large, vibration and noise are generated. This is due to a change in the meshing state at the connecting portion due to the shaft angle fluctuation.
In other words, the number of meshing teeth is large at zero shaft angle, but when the shaft angle fluctuation δ increases, the number of meshing teeth suddenly decreases and the load transmission capacity decreases. Vibration will occur.

In this example, an experimental analysis revealed that the allowable axial angle is up to an axial angle variation δ of about 3 °.
If the variation in the shaft angle is within about 3 °, all the teeth of the connecting portion mesh with each other due to the deformation of the tooth portion, and the contact area of each tooth pair is sufficient, so that stable load transmission is possible.
When the allowable shaft angle δ is about 3 ° and the center-to-center distance Lsp of each meshing portion of the spline transmission member 20 is 30 mm, the allowable amount of eccentricity is calculated by the following equation, and is 157 μm.
0.157 (mm) = tan (0.3 deg) × 30 (mm)

  In this embodiment, the amount of self-aligning movement of the carrier due to the manufacturing error of each gear constituting the planetary gear mechanism is within 50 μm, and the spline connecting portion on the drum flange (member indicated by reference numeral 1A in FIG. 2) side Since the coaxial error between the planetary gear mechanism (the portion indicated by the negative sign 1A1 in FIG. 1) and the planetary gear mechanism is 50 to 100 μm, the carrier movement and the coaxial error can be corrected in the allowable shaft angle fluctuation amount at the spline connecting portion.

  By the way, if the total of the self-aligning movement amount of the carrier and the coaxial error between the drum flange 1A side and the planetary gear mechanism exceeds 150 μm, this can be dealt with by increasing the length (Lsp) of the spline transmission member 20. Can do. Alternatively, the permissible shaft angle δ may be increased by changing the meshing pitch circle diameter of the spline connecting portion (increasing the number of teeth).

In the present embodiment, a two-stage involute coupling configuration is formed by engaging the spline transmission member 20 with two-stage engagement between the inner teeth 18A of the carrier 18 and the inner teeth on the photosensitive drum shaft side. Thereby, even if it is fitting with an axis center tilting mutually, rotation is transmitted with sufficient accuracy. The reason for this will be described with reference to FIG.
FIG. 11 shows an outline of the rotation state of the carrier and the drum flange connected by the inclined spline transmission member.

First, when the angular velocity of the carrier is ω0 and the reference radius is r0, the linear velocity Vd1 (t) at the reference radius position of the carrier is given by the following equation (1).
Vd1 (t) = r0 * ω0 (1)
Further, the linear velocity of the carrier and the spline transmission member is equal at the contact point.
Therefore, assuming that the rotational radius of the spline transmission member corresponding to the reference radius r0 in the fitted state at that time is r1 (t), the angular velocity ω1 (t) of the spline transmission member is given by the following equation (2). It is done.
ω1 (t) = Vd1 (t) / r1 (t) (2)
Further, substituting the right side of equation (1) into Vd1 (t) of equation (2) yields the following equation (3).
ω1 (t) = r0 * ω0 / r1 (t) (3)
On the other hand, on the drum flange side, the angular velocity of the spline transmission member is ω1 (t), and the linear velocity of the spline transmission member and the drum flange is equal at the contact point.
Accordingly, the linear velocity Vd2 (t) of the drum flange at the position of the rotation radius r1 (t) of the spline transmission member is given by the following equation (4).
Vd2 (t) = r1 (t) * ω1 (t) (4)
Substituting the right side of the equation (3) into ω1 (t) in the above gives the following equation (5). Vd2 (t) = r1 (t) * r0 * ω0 / r1 (t) = r0 * ω0 (5)
On the other hand, the angular velocity ω2 (t) of the drum flange is given by the following equation (6) because the rotation radius of the drum flange at the contact point between the drum flange and the spline transmission member is r0.
Vd2 (t) = r0 * ω2 (t) (6)
Therefore, the following equation (7) is obtained from the equations (5) and (6).
ω2 (t) = ω0 (7)

From this, it can be seen that the rotation angular velocity of the drum flange is equal to the rotation angular velocity of the carrier and is a steady rotation.
Therefore, according to the spline transmission member, even if the spline transmission member and the drum flange are not aligned with each other, the spline transmission member is fitted as it is, and the drive transmission in the rotational direction is reliably performed.

  Conventionally, in an image forming apparatus such as a printer, a facsimile machine, and a copying machine, an image carrier (photosensitive drum) that is rotatably supported with respect to a casing of the apparatus main body, and a developing device supported by the casing. It is known that a so-called development gap, which is a gap at a position closest to a developer carrying member rotatably supported with respect to the casing, greatly affects the quality of image quality.

The development gap is desired to be narrower and have less adjustment errors in order to improve the image quality.
The development gap is usually set by adjusting the fixing position of the developing holder for fixing and holding the developing sleeve as the developer carrier relative to the photosensitive member as the image carrier.
For example, the adjustment range of the development gap is required to be adjusted with very high accuracy such that the adjustment value is narrow but the adjustment error is 0.05 mm, such as 0.4 ± 0.05 mm. .
When the movement vibration of the carrier rotation shaft due to the carrier floating support is transmitted to the photosensitive drum, a new problem of developing density unevenness occurs. In order to solve this problem, it is effective to employ a spline coupling with little moving friction in the plane perpendicular to the axis.

Next, a second embodiment of the present invention will be described.
In the second embodiment, a spline transmission member that meshes with an output shaft integrated with the carrier 18 is provided as an output portion of the planetary gear mechanism. Furthermore, in this embodiment, a configuration is provided in which the center of the planetary gear mechanism can be aligned with the photosensitive drum shaft corresponding to the driven member when the planetary gear mechanism is assembled. The configuration will be described below with reference to FIG. 12 and subsequent drawings.

FIG. 12 is a diagram showing a main configuration of a drive device that is a second embodiment of the drive device according to the present invention.
In FIG. 12, the driving device 100 is located at the final stage of a planetary gear mechanism (indicated by reference numeral 11 used in FIG. 2 for convenience) provided with a two-stage planetary gear and a carrier as in the case shown in FIG. An output shaft 101 is integrated with the carrier (for convenience, indicated by reference numeral 18 in FIG. 2) as a component of the output unit.
In addition to the output shaft 101 described above, the output unit uses a spline transmission member 20 ′ having the same principle configuration as the configuration described in FIG.

In this embodiment, the spline included in the spline transmission member 20 ′ is the female (female) side, and the output shaft 101 side and the photosensitive drum shaft side are the male (male) side.
The output shaft 101 and the spline transmission member 20 ′ constituting the output portion of the planetary gear mechanism 11 are arranged in a common positioning unit 102 together with a photosensitive drum that is detachably supported in the opposite direction to the output shaft 101. Has been.

The common positioning unit 102 has a through-hole through which the output shaft 101 and the photosensitive drum shaft can be inserted at the center, and is opposed to the end plates 102A and 102B facing the output shaft 101 side and the photosensitive drum side. In addition, axial center positioning holes 102A1 and 102B1 formed by aligning the axial center positions are provided.
The axial center positioning holes 102A1 and 102B1 are configured by holes that pass through the centers of the end plates 102A and 102B, and the inner diameter of the shaft positioning holes 102A1 and 102B1 is formed in the end plate on the planetary gear mechanism 11 side (indicated by reference numeral 22 in FIG. 2). The size is such that the fixed positioning projection 22A and the drum bearing 1B1 of the photosensitive drum 1 can be fitted.
In FIG. 12, reference numeral 201 denotes a bracket for fastening the positioning unit 102 to the main body side plate 50.

  As a result, the output shaft 101 and the photosensitive drum shaft 1A0 that can be attached to and detached from the spline transmission member 20 ′ are aligned with each other by inserting the positioning projection 102A2 and the drum bearing 1B1 into the shaft positioning hole. It will be arranged in the state that was done. On the photosensitive drum shaft 1A0 side, a projecting portion 1C that protrudes toward the common positioning unit 102 side with the same center as the drum bearing 1B1 is provided at the outer peripheral position of the drum bearing 1B1. Even if the projecting portion 1C is formed on the end plate on the common positioning unit 102 side and fitted into the recessed portion (not shown), the axial alignment with the output shaft 101 can be obtained.

On the other hand, the common positioning unit 102 that commonly supports the output shaft 101 and the photosensitive drum shaft 1A0 that can be attached to and detached from the spline transmission member 20 ′ is integrally formed by resin molding, aluminum die casting, or cutting using these materials. It is said that. As a result, a highly accurate coaxial accuracy of the hole position can be obtained.
Further, the right-angle accuracy for obtaining the coaxial accuracy of the two bodies at the time of assembling the apparatus can be easily obtained by the processing accuracy of the A surface for attachment of the speed reduction mechanism and the B surface for attachment of the main body side plate 50.
When viewed as the rigidity of the transmission system, it is generally performed that the rotation transmission body is driven in a state in which the positioning unit 102 having such an integrated block structure is fixed to each mounting surface. Since rigidity higher than the method of standing the stud on the main body side plate 50 and fixing it to the bracket can be obtained, the occurrence of vibration is suppressed here.

FIG. 13 shows a configuration when the positioning unit 102 described above is attached to the main body side plate 50.
In the figure, in order to reduce color misregistration and banding (color unevenness) in the configuration of the tandem type image forming apparatus using Y, M, C, and Bk developers, in addition to high-precision support driving of the rotating system, The positional accuracy between the modules constituting these stations must be ensured. The parallelism and alignment of the axes of the four color units must be several tens of μm or less.

In the present embodiment, as shown in FIG. 13, the common positioning unit 102 is provided with a mounting opening 501 formed in the rear side plate located behind the main body side plate 50 and two positions provided in the vicinity of the opening. Positioning with reproducibility can be performed only by fixing in accordance with the extraction reference (X-direction reference and Y-direction reference). Thereby, the positional accuracy between each unit can be easily ensured.
Further, as shown in FIG. 14, the common positioning unit 102 can be removed by attaching (screw fastening) from the outside of the apparatus to the main body side plate 50 of the apparatus so that assembly and apparatus maintenance can be easily performed. As a structure.

On the other hand, the output portion of the planetary gear mechanism 11 is provided with a configuration that prevents the output portion from falling off when being attached or detached.
FIG. 15 is a diagram showing a state where the photosensitive drum 1 corresponding to the driven member is attached / detached. In FIG. 15, the spline transmission member 20 ′ used for the output portion of the planetary gear mechanism 11 has a common positioning unit 102. A drop-off prevention member 103 whose base end is supported by one end plate of the plate is provided.

The drop-off prevention member 103 uses a leaf spring member having a fork formed at the tip extending from the base end, and the fork is fitted into the fitting groove 20A ′ formed in the spline transmission member 20 ′. is doing.
The drop-off prevention member 103 holds the position of the spline transmission member 20 ′ in a state where no displacement in the axial direction occurs, and also holds both the shafts during rotation driving.
When the photosensitive drum shaft 1A0 is inserted into the spline transmission member 20 ′, the drop-off prevention member 103 is subjected to a load in a direction in which the photosensitive drum shaft pushes and moves the spline coupling portion, thereby being deformed by being deformed in the thrust direction. To escape. As a result, it is possible to prevent the parts from being deformed or broken without applying an excessive load or impact force to the spline teeth of the spline transmission member 20 ′, the photosensitive drum 1 or the common positioning unit 102. .

  The drop-off prevention member 103 swings in the thrust direction by dragging the spline transmission member 20 ′ together with the photosensitive drum shaft when there is a resistance in the spline engaging portion when the photosensitive drum shaft is removed when the photosensitive drum is removed. If the deformation region of the leaf spring is exceeded, it is prevented from falling off. That is, as shown in FIG. 15A, in the common positioning unit 103, the stopper member 104 is provided on the end plate on the extraction side of the photosensitive drum, and the spline transmission member 20 ′ is prevented from falling off. It is designed to stop moving beyond the deformation area. As a result, when the photosensitive drum shaft is completely extracted, the spline transmission member 20 ′ returns to the initial position in conjunction with the return operation of the drop-off preventing member 103, so that the shaft when the photosensitive drum shaft is inserted again is restored. The heart position is maintained at a predetermined position.

Next, a modification of the main part of the spline transmission member 20 ′ will be described.
FIG. 16 is a diagram showing details of spline teeth of the spline transmission member 20 ′, and FIG. 17 is a developed view of the spline.
In FIG. 16 and FIG. 17, the spline teeth can be shifted to a smooth engagement by making the ends of teeth facing each other at the engagement start point in the circumferential direction into an R shape or a triangular shape with a sharpened tip. It becomes.
On the other hand, among the above-described spline teeth, the pair of teeth SP1 at a phase position of approximately 180 ° is configured to be slightly longer than the other tooth profile SP2, and it is intended to be elastically slightly deformed. As a result, when the end of the involute tooth profile of the photosensitive drum shaft 1A0 comes into contact with the end of the elongated tooth SP1, the apex of the tooth is slightly deformed and moved while receiving the contact pressure, and the abutting proceeds while escaping. Thereafter, the meshing is performed smoothly while moving along the locus indicated by the arrow.

Next, the structure of spline transmission member 20 'used for a present Example is demonstrated using FIG.
The spline transmission member 20 ′ used in this embodiment has a two-layer structure of a resin material corresponding to the tooth profile and a metal ring that wraps around the outer periphery thereof.
In general, mass-produced products are made by molding, and can be integrally formed with a metal ring. A lightweight and highly rigid material such as Al (aluminum) or an Al alloy is used as the metal ring body.
If all are made of resin, the wall thickness becomes large, and the accuracy of the tooth mold deteriorates due to the sink phenomenon of the resin. Even when the rib structure is made uniform, the problem of enlargement (large diameter) occurs.
Therefore, a method is used in which resin is poured into the unevenness formed on the inner surface of the metal ring, or through a hole, and fixed.
The resin material is basically selected from the transmission characteristics of rotational vibration, but for smooth meshing of the teeth, considering low friction and moldability, polyacetal, polycarbonate, nylon, etc. are used. Select, and in some cases, use a more rigid engineering plastic.

  When the tooth mold part is made of a resin material, the thick part in the diameter direction is not thickened and the rigidity is secured, so that extra vibration components are not generated when the transmission torque is applied. Is possible. In such a configuration, it is possible to ensure rigidity (Young's modulus) other than the meshing tooth portions, and the generated vibration is suppressed in this portion.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 1A End plate 1A1 Internal tooth 10 Drum drive device 11 Planetary gear mechanism 14 Planetary gear 18 Final stage carrier 18A Internal tooth 20, 20 'Spline transmission member 23,103 drop-off prevention member M drive motor M1 Axis located on the input side of the planetary gear mechanism

JP 2008-151868 A JP 2009-271380 A

Claims (9)

In the drive device provided with the planetary gear speed reduction mechanism in the transmission path for transmitting the drive force from the drive motor to the driven member,
The planetary gear speed reduction mechanism is provided with at least one stage carrier and a planetary gear supported by the carrier, and an output section is provided on the last stage carrier,
The output device includes a configuration in which the output unit is supported only by the carrier when the driving force is transmitted to the driven member.   The output portion is provided with a coupling member that engages with an engaging portion formed on the last stage carrier or an output shaft integrated with the carrier. Drive device.   The drive device according to claim 1, wherein the output unit is detachably attached to the carrier.   3. The driving apparatus according to claim 1, wherein the output unit is supported by only the carrier without using a bearing with respect to a driven member that is supported by using a bearing. 4.   The drive device according to claim 1, wherein the output unit includes a drop-off preventing unit during attachment / detachment.   The driving device according to claim 1, wherein the carrier and the output unit are coupled using an uneven spline having a longitudinal direction in a direction perpendicular to the rotation direction.   The drive device according to claim 6, wherein the drop-off prevention member is provided in the spline coupling portion.   The output part of the carrier is housed in a detachable unit, and an input shaft of a driven member is provided in the unit so as to be detachable from the output part. 8. The drive device according to 7.   An image forming apparatus using the driving device according to claim 1, wherein the driving device is used for each of a plurality of driven members.

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