JP2012092936A - Planetary gear speed reducer and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a planetary gear speed reducer that can improve durability, and to provide an image forming device.SOLUTION: The planetary gear speed reducer is configured to connect a second stage planetary gear mechanism 32 to the rear stage of a first stage planetary gear mechanism 31 to reduce the speed of rotary driving force from a motor M by the first stage planetary gear mechanism 31 and the second stage planetary gear mechanism 32 and transmit the force to a drum shaft 27 from an output shaft 20 provided in a second carrier 19. A center side outer diameter edge of a first carrier pin 25 is positioned inner side more than a position of outer diameter of a second sun gear 17.

Description

  The present invention relates to a planetary gear reduction device and an image forming apparatus, and more particularly to a planetary gear reduction device used in a drive transmission system of an electrophotographic image forming apparatus having a photosensitive drum and an image forming apparatus including the planetary gear reduction device.

  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.

  A plastic gear formed by injecting molten resin is used for a drive transmission portion of such a photosensitive drum or transfer belt that requires high precision driving. Plastic gears are superior to metal gears in that they are self-lubricating, have low noise during use, can be reduced in weight, have high corrosion resistance, and have high mass productivity. On the other hand, durability (abrasion resistance), high rigidity, and high accuracy are inferior.

  In order to increase durability and rigidity even when plastic gears are used, it has been proposed to use a planetary gear speed reducer as a drive speed reducer. The planetary gear reduction device has a sun gear and an internal gear arranged concentrically, and a plurality of planet gears meshing with both of them, and the planet gear is supported by rotation by a carrier and can be rotated and fixed around the sun gear. It is in a state. Since the plurality of planetary gears transmit the rotational load of the output shaft in a distributed manner, it is superior in durability and transmission rigidity to the gear device of the toothed wheel train, and downsizing of the gears can be realized. For example, a configuration has been proposed in which a downsized driving mechanism and a motor as a driving source are arranged inside a roller member that is a conveyance roller for a photosensitive drum or a transfer belt, thereby realizing a significant downsizing. (For example, refer to Patent Document 1).

  In general, in a drive speed reducer for a photosensitive drum of an image forming apparatus such as a copying machine or a printer, a drive motor and a speed reducer used in a speed reduction system for a toothed wheel train are based on required specifications for rotational accuracy and rotational speed. Motors with the following specifications are used. Method: Outer rotor type DC brushless motor. Motor rotation speed: 1000 rpm to 2500 rpm (however, considering the efficiency of the outer rotor type DC brushless motor, the rotation speed is preferably 3000 rpm to 5000 rpm). Motor shaft diameter: φ6 (when the gear of the motor shaft is larger than φ6, the stepped shaft is processed). Motor outer rotor diameter: about φ40 to φ60. Reduction gear reduction ratio: about 1/15 to 1/20. In addition, the diameter of the photosensitive drum is mainly 30 to 60.

  In a general 2K-H type planetary gear mechanism, the input shaft is connected to the sun gear, the output shaft (reducing and rotating) is connected to the carrier, the internal gear is fixed to the casing in a non-rotatable manner, and a plurality of planetary gears are connected. The structure is supported by rotation on the carrier and meshes with the sun gear and the internal gear, and even if the reduction ratio can be increased, it is about 1/10.

  However, by making the 2K-H type planetary gear mechanism in two stages, the reduction ratio of the reduction gear can be easily reduced to 1/20 to 1/40, and the motor can be used at an efficient rotational speed.

  Further, the planetary gear reduction device is driven by distributing the load to a plurality of planetary gears, but it is known that three planetary gears are equally distributed and the rotation accuracy is good.

  Further, by making the outer shape of the planetary gear reduction device equivalent to or smaller than the outer shape of the motor and the photosensitive drum, the advantage of downsizing can be exhibited.

  In recent years, the printing speed of copying machines and printers has been increased, and further high durability of the drive speed reducer has been demanded. Further, in order to improve the image quality, polymerized toner is often used, and the load torque on the drive speed reducer is increased due to an increase in load on the cleaning drum of the photosensitive drum.

  On the other hand, it is conceivable to use a planetary gear reduction device with a multistage high reduction ratio and a highly efficient motor speed. In order to simplify the configuration, the internal gear that meshes with the planetary gear of each stage is made common, the planetary gear of each stage is made common, and the sun gear is also made common with the same number of teeth (for example, Patent Document 2).

  However, a large load torque is applied to the last stage planetary gear mechanism close to the output shaft, and the largest load torque is applied to the sun gear. Therefore, in the configuration as disclosed in Patent Document 2, since the wear of the sun gear at the final stage proceeds the fastest, it is insufficient for improving the durability.

  The present invention has been made to solve such a problem, and provides a planetary gear reduction device and an image forming apparatus capable of improving durability.

  The planetary gear reduction device according to the present invention includes a first sun gear, a first internal gear arranged coaxially with the first sun gear, and an equal interval in the circumferential direction within the first internal gear. A plurality of first planetary gears disposed on the first sun gear and meshing with the first internal gear, the first planetary gear rotatably supported by a first carrier pin, and the first sun gear and A first planetary gear mechanism comprising a first carrier that is coaxially rotatable with the first internal gear, a second sun gear, and a second internal gear disposed coaxially with the second sun gear. A gear, a plurality of second planetary gears arranged at equal intervals in the circumferential direction in the second internal gear, and meshing with the second sun gear and the second internal gear; and the second planetary gear. The second carrier pin is rotatably supported and is coaxial with the second sun gear and the second internal gear. A second planetary gear mechanism comprising: a second carrier that is freely rotatable; and the second planetary gear mechanism is connected to a subsequent stage of the first planetary gear mechanism so that a rotational driving force from a driving source is generated. In the planetary gear reduction device that transmits the speed to the rotating body from the output shaft provided on the second carrier by reducing the speed by the first planetary gear mechanism and the second planetary gear mechanism, the outer diameter position of the second sun gear The center-side outer diameter edge of the first carrier pin is set inside.

  With this configuration, the second sun gear can have a large diameter, and durability can be improved. In addition, there are an effect of transmitting the rotation with high accuracy and an effect of simplifying the structure with good mass productivity.

  Moreover, the planetary gear speed reduction device according to the present invention is characterized in that a center-side outer diameter edge position of the second carrier pin is set to an inner side than an outer diameter position of the output shaft.

  With this configuration, the output shaft can have a large diameter, the torsional rigidity can be increased, and a high load torque can be handled.

  Further, the planetary gear speed reduction device according to the present invention is formed by directly cutting the first sun gear on the drive shaft of the drive source, and sharing the first internal gear and the second internal gear. The first carrier pin and the second carrier pin are made of a metal material, and the remaining other members are made of a resin material.

  With this configuration, the other members of the first carrier pin and the second carrier pin are made of a resin material, thereby enabling mass production at low cost by resin molding.

  Moreover, the planetary gear speed reduction device according to the present invention is formed such that a concave portion is formed at an end of the second sun gear on the first carrier pin side, and the second sun gear and the first carrier pin are A space is provided in the overlap portion.

  With this configuration, it is possible to prevent the tooth profile accuracy of the second sun gear from being deteriorated due to an effect such as a difference in heat shrinkage during molding.

  In the planetary gear speed reduction device according to the present invention, a concave portion is formed at an end portion of the output shaft on the second carrier pin side, and an overlap portion between the output shaft and the second carrier pin is formed. It is characterized by providing a space.

  With this configuration, resin molding is possible without deteriorating the accuracy of the tooth profile shape or spline shape.

  The planetary gear speed reduction device according to the present invention is characterized in that the number of the second planetary gears is larger than the number of the first planetary gears.

  With this configuration, the load applied to each second planetary gear can be reduced.

  The planetary gear reduction device according to the present invention is characterized in that the first planetary gear mechanism includes three first planetary gears, and the second planetary gear mechanism includes four second planetary gears. To do.

  With this configuration, the load applied to each second planetary gear can be reduced.

  The planetary gear speed reduction device according to the present invention is characterized in that the first carrier and the second carrier do not have a rotation support portion and perform floating rotation.

  With this configuration, alignment is more effectively exhibited and rotation is transmitted with high accuracy.

  The planetary gear reduction device according to the present invention is characterized in that the output shaft and the rotating body are connected by a spline coupling.

  With this configuration, the rotating body can be easily attached to and detached from the output shaft.

The image forming apparatus according to the present invention includes, in an image forming apparatus including a rotating body, a driving source that drives the rotating body, and a speed reducing unit that reduces the rotational speed of the driving source and transmits the rotating speed to the rotating body. With
The planetary gear speed reduction device according to any one of claims 1 to 9 is provided as the speed reduction means.

  With this configuration, in the image forming apparatus including the planetary gear reduction device, the second sun gear can have a large diameter and durability can be improved.

  The image forming apparatus according to the present invention is characterized in that the rotating body is an image carrier on which an electrostatic latent image is formed in an electrophotographic system.

  With this configuration, in the image forming apparatus including the image carrier as the rotating body, the second sun gear can have a large diameter, and durability can be improved.

  According to the present invention, it is possible to provide a planetary gear reduction device and an image forming apparatus that can improve durability.

1 is a diagram illustrating a schematic configuration of an entire image forming unit of an image forming apparatus according to an embodiment of the present invention. It is a figure which shows the state which used the planetary gear reduction device which concerns on one embodiment of this invention for the drive of the photosensitive drum. It is a fragmentary sectional view which shows the specific structure of the planetary gear speed reducer which concerns on one embodiment of this invention. It is sectional drawing which shows the diameter of each member of the planetary gear reduction device which concerns on one embodiment of this invention. It is sectional drawing which shows the planetary gear mechanism of the 1st step | level of the planetary gear reduction device which concerns on one embodiment of this invention. It is sectional drawing which shows the planetary gear mechanism of the 2nd step | level of the planetary gear reduction device which concerns on one embodiment of this invention. It is sectional drawing which shows the case where it is going to arrange | position four planetary gears in the planetary gear mechanism of the 1st step | paragraph of the planetary gear reduction apparatus which concerns on one embodiment of this invention. 1 is a perspective view showing a first-stage planetary gear mechanism of a planetary gear reduction device according to an embodiment of the present invention. It is a perspective view which shows the 2nd stage planetary gear mechanism of the planetary gear reduction device which concerns on one embodiment of this invention. It is sectional drawing of the planetary gear speed reducer which concerns on one embodiment of this invention, and is a figure which shows the state which formed the relief part in the root of the 2nd sun gear, and the root of the output shaft. It is a front view of the 1st career of the planetary gear speed reducer concerning one embodiment of the present invention. It is a figure which shows the state which used the planetary gear reduction device which concerns on one embodiment of this invention for the drive of a transfer belt.

  First, an outline of the embodiment will be described prior to the description with reference to the drawings.

  The gear used for the planetary gear speed reducer is preferably a resin molded product in view of mass productivity, but is inferior in wear resistance, that is, durability compared to metal.

  Therefore, in order to improve durability with a simple configuration, the applicant configured the planetary gear reduction device as follows.

  As a drive source, an outer rotor type DC brushless motor, which is most commonly used in copying machines and printers and has a motor shaft diameter of φ6, is used. The first sun gear is directly cut into the metal motor shaft. Used as

  Regarding the improvement of durability, first, there is no problem because the first sun gear is a metal material. Next, it is conceivable to increase the number of first planetary gears, but assuming that the load torque applied to the first stage planetary gear mechanism is small and that the sun gear is geared to the motor shaft φ6, The number of planetary gears that can be placed around is limited to three, and if three can be arranged, the load applied to the planetary gears is evenly distributed and the rotational accuracy is improved, so three planetary gears are arranged. To do.

  The largest load torque is applied to the last stage planetary gear mechanism. However, in the present embodiment having two planetary gear mechanisms, the largest load torque is applied to the second stage. Among them, the largest load torque is applied to the second sun gear at the center of rotation. Therefore, since the force applied to the teeth can be reduced as the diameter of the second sun gear is increased, the number of teeth of the second sun gear is configured to be larger than the number of teeth of the first sun gear. The output shaft of the second sun gear was made larger in diameter. Further, as a measure for improving the durability of the second planetary gear, the number of planetary gears is increased from three to four to reduce the load on one planetary gear. This is possible because the number of teeth of the second sun gear is increased to increase the diameter.

  In this Embodiment, the structure which enlarges the diameter of a 2nd sun gear is achieved because the 1st carrier pin was located in the center direction rather than the outer diameter of the 2nd sun gear.

  In the above configuration, the tooth profile of the second sun gear and the hole of the first carrier pin interfere with each other. Therefore, in the case of mass production by resin molding, there is a difference in heat shrinkage during molding. The tooth profile accuracy of the sun gear is degraded. As a solution to this problem, a relief portion is provided at the root of the second sun gear.

  As described above, the durability is improved by reducing the force applied to each gear and suppressing the wear of teeth.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, the configuration will be described.

  FIG. 1 is a diagram illustrating the configuration of the image forming apparatus. Hereinafter, an embodiment in which the present invention is applied to an electrophotographic color copier (hereinafter referred to as “copier”) which is an image forming apparatus will be described. Note that the image forming apparatus according to the present embodiment is a so-called tandem image forming apparatus that employs a dry two-component developing system using a dry two-component developer.

  FIG. 1 is a schematic configuration diagram of the entire image forming unit of the image forming apparatus according to the present embodiment. The image forming apparatus 100 receives image data as image information from an image reading unit (not shown) and performs image forming processing. In this image forming apparatus 100, as shown in the drawing, yellow (hereinafter abbreviated as “Y”), magenta (hereinafter abbreviated as “M”), cyan (hereinafter abbreviated as “C”). ) And black (hereinafter abbreviated as “Bk”), photosensitive drums 1Y, 1M, 1C, and 1Bk are arranged side by side as latent image carriers as four rotating bodies for each color. 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. 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, cleaning devices 4Y, 4M, 4C, Electrophotographic process members such as 4Bk, static elimination lamps 3Y, 3M, 3C, and 3Bk are arranged in the order of processes.

  When a full-color image is formed by the image forming apparatus 100 according to the present embodiment, the charger 2Y rotates the photosensitive drum 1Y in the direction of the arrow in the drawing by a driving device 10 (see FIG. 2) described later. After charging in this manner, a Y electrostatic latent image is formed on the photosensitive drum 1Y by irradiating a light beam LY from an optical writing device (not shown). 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). Then, 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.

  FIG. 2 is an explanatory diagram of a drive device including a planetary gear reduction device.

  The photosensitive drums 1Y, 1M, 1C, and 1Bk described with reference to FIG. 1 are rotationally driven by a driving device with a planetary gear reduction device described below. Since the driving devices for driving the photosensitive drums 1Y, 1M, 1C, and 1Bk have the same configuration, the driving device for the photosensitive drum 1Y will be described. Note that the driving device described below can also be applied to driving of the driving roller of the intermediate transfer belt.

  A drum flange 1A for rotating and supporting the photosensitive drum 1Y and a drum shaft 27 are fixed to the axial end of the photosensitive drum 1Y. The photosensitive drum 1Y and the charger 2Y, the developing device 9Y, the cleaning device 4Y, the static elimination lamp 3Y and the like are rotatably supported by a drum bearing 1B installed in the photosensitive drum unit DY. The drum shaft 27 is also rotatably supported by a bearing of the main body side plate 50 of the image forming apparatus 100, and the rotational force of the output shaft 20 of the planetary gear reduction device 30 supported by the drive side plate 51 is a joint (coupling). Is transmitted to the drum shaft 27. 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 above-described joint is configured so that the drum shaft 27 can be easily attached to and detached from the output shaft 20 in order to allow replacement of the photosensitive drum 1Y. The planetary gear reduction device 30 is fixed to the driving side plate 51 by a main body mechanism fixing screw 52. The internal gear 14 is non-rotatably fixed to the flange 54 by an internal tooth fixing screw 53, and the motor M is fixed to the opposite side of the flange 54. The internal gear 14 is fixed by the flange 54 so as not to rotate with respect to the motor rotation. The motor M and the planetary gear speed reduction device 30 constitute the drive device 10.

  In FIG. 2, attachment / detachment of the photosensitive drum will be described.

  A drum flange 1A is fixed to the end of the photosensitive drum 1Y, which is a driven member, and rotates integrally with the photosensitive drum 1Y.

  The drum flange 1A is rotatably supported by a drum bearing 1B installed in the photosensitive drum unit DY that houses the photosensitive drum 1Y. 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, so that the coaxial accuracy between the photosensitive drum 1 </ b> Y and the planetary gear reduction device 30 in the driving device 10 is ensured.

  Since the fitting portion between the spline-shaped external teeth 21 (see FIG. 3) of the drum shaft 27 and the output shaft 20 is spline-shaped, it is only necessary to pull out the photosensitive drum unit DY from the main body side plate 50 in the direction of the drum shaft 27. The spline-shaped external teeth 21 (connecting portion) formed on the drum shaft 27 from the output shaft 20 of the two carrier 19 can be separated. That is, the spline-shaped external teeth 21 of the drum shaft 27 correspond to a member that can be easily attached to and detached from the output shaft 20 of the second carrier 19.

  FIG. 3 is a diagram for explaining a specific planetary gear reduction device.

  The planetary gear mechanism used in the drive device shown in FIG. 2 is a 2K-H type two-stage planetary gear mechanism, and its basic configuration is shown in FIG.

  The planetary gear reduction device 30 includes a first-stage planetary gear mechanism 31 and a second-stage planetary gear mechanism 32. The first-stage planetary gear mechanism 31 includes the first sun gear 12, the first planetary gear 15, The second carrier planetary gear mechanism 32 including the first carrier 16 includes the second sun gear 17, the second planetary gear 18, and the second carrier 19. The first-stage planetary gear mechanism 31 and the second-stage planetary gear mechanism 32 include one common internal gear 14. That is, the first stage planetary gear mechanism 31 and the second stage planetary gear mechanism 32 share one internal gear 14.

  In the planetary gear reduction device 30, the first sun gear 12 is directly geared to the rotation shaft M <b> 1 of the motor M as a drive source, and the internal gear 14 fixed to the first sun gear 12 and the internal gear fixing flange 24 is used. The meshing first stage first planetary gear 15 is supported by the first stage first carrier 16 and revolves around the outer periphery of the first sun gear 12. The first planetary gear 15 is concentrically arranged at three locations for rotational balance and torque sharing. In the present embodiment, the first planetary gears 15 are arranged at positions equally divided into three in the circumferential direction. Each first planetary gear 15 is supported by a first carrier pin 25 provided on the first carrier 16 and rotates.

  The first planetary gear 15 rotates and revolves by meshing with the first sun gear 12 and the internal gear 14, and the first carrier 16 that supports the first planetary gear 15 rotates the first sun gear 12. The first reduction gear ratio is obtained.

  Next, the second sun gear 17 provided at the rotation center of the first carrier 16 serves as an input to the second stage planetary gear mechanism 32. The first carrier 16 does not have a rotation support portion, and performs floating rotation. That is, the first carrier 16 is rotatably supported by the casing.

  Similarly, the second sun gear 17 of the second stage is supported by the second carrier 19 of the second stage, and the second planetary gear 18 of the second stage that meshes with the internal gear 14 that is integrally formed up to the second stage. Thus, the outer periphery of the second sun gear 17 in the second stage is revolved. In the present embodiment, the second planetary gears 18 are arranged at positions equally divided into four in the circumferential direction. Each second planetary gear 18 rotates by being supported by a second carrier pin 26 provided on the second carrier 19. A second-stage second carrier 19 corresponding to the final stage is provided with a cylindrical output shaft 20, and spline-shaped internal teeth 20 </ b> A are formed on the inner surface of the output shaft 20. On the other hand, spline-shaped external teeth 21 are formed on the drum shaft 27 so as to mesh with the spline-shaped internal teeth 20A.

  One unit used for the 2K-H type planetary gear mechanism includes a sun gear (Sun Gear), a planetary gear (Planetary Y Gear), a planet carrier that supports the revolving motion of the planetary gear (Planetary Y Carrier), and an internal gear (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 and fixed, a plurality of reduction ratios and rotation directions can be switched by one unit.

  The target 2K-H type two-stage structure in the present embodiment is classified into compound planetary gear mechanisms (two or more 2K-H types), and each of the two or more 2K-H type three-stage structures. Of the basic shafts, two basic shafts are coupled to each other, one of the remaining basic shafts is fixed, and the other shaft is used as a drive shaft or a driven shaft.

  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.

Reduction ratio = Za1 / (Za1 + Zc1) × Za2 / (Za2 + Zc2)
The rotating shaft M1 of the motor M described above is supported by the motor fixing flange 13 via two bearings (not shown). 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 13 is also provided with a stator core of a motor (not shown), a motor drive circuit board 23, and the like.

  An internal tooth fixing flange 24 having the internal gear 14 is fixed to the motor fixing flange 13 by screws (not shown). 2 corresponds to both the internal tooth fixing flange 24 and the motor fixing flange 13, and the internal tooth fixing flange 24 and the motor fixing flange 13 may be integrally formed as the flange 54.

  The motor fixing flange 13 uses a metal plate of about 5 mm so as to have sufficient strength. A first sun gear 12 is formed by gear cutting on the rotation shaft M1 of the motor M, and in order to ensure the coaxial accuracy between the axis of the first sun gear 12 and the axis of the internal gear 14, the internal gear 14 is provided. The motor fixing flange 13 is positioned by fitting with a spigot.

  An end cap 22 is fastened to the end of the internal gear 14 opposite to the motor fixing flange 13 with screws.

  The end cap 22 includes a first planetary gear 15, a second planetary gear 18, a first carrier 16, a second carrier 19, and the like installed in the internal gear 14 when the planetary reduction mechanism is assembled to the drive side plate. It is used as a member for preventing the output shaft 20 from falling off the internal gear 14. There is sufficient clearance between the end cap 22 and the output shaft 20 of the second carrier 19, and the end cap 22 does not support the rotation of the second carrier 19, and the second carrier 19 performs floating rotation. . That is, the second carrier 19 is supported by the casing so as to be rotatable.

  As described above, the second carrier 19 is supported in a floating manner, and the spline-shaped inner teeth 20A are formed on the inner surface of the output shaft 20 as an output portion, while the drum shaft 27 meshes with the spline-shaped inner teeth 20A. Further, by forming the spline-shaped external teeth 21 and performing the spline coupling, the alignment is more effectively exhibited and the rotation is transmitted with high accuracy.

  In the planetary gear reduction device described above, the first sun gear 12 directly cut by the rotating shaft M1 of the motor M, the first carrier pin 25, and the second carrier pin 26 are made of a metal material such as stainless steel or carbon steel. The other first planetary gear 15, the first carrier 16 and the second sun gear 17 integrally formed, the second planetary gear 18, the second carrier 19 and the spline-like internal teeth 20 </ b> A of the output portion integrally formed. The internal gear 14 integrally formed with the housing case with a common gear specification meshing with the first planetary gear 15 and the second planetary gear 18 is made of a resin material, for example, a molded product such as polyacetal.

  FIG. 4 is a diagram for explaining the configuration of the characterizing portion of the invention.

  FIG. 4 is an enlarged view of the planetary gear reduction mechanism of FIG. The outer diameter of each component gear, each carrier pin, and the output shaft is represented by the following symbols.

  Ds1: 1st sun gear pitch circle diameter. Dp1: 1st planetary gear pitch circle diameter. Dcp1: first carrier pin diameter. Ds2: Second sun gear pitch circle diameter. m: Gear module. Dsc: Output shaft diameter. Dp2: Second planetary gear pitch circle diameter. Dcp2: second carrier pin diameter.

  In the present embodiment, the first-stage planetary gear mechanism 31 and the second-stage second sun gear 17 have the relationship of the following first formula.

First formula: Ds2 / 2 + m> (Ds1 + Dp1) / 2-Dcp1 / 2
In other words, the center outer diameter edge of the first carrier pin 25 is on the inner side than the outer diameter position of the second sun gear 17. In other words, the outer diameter of the second sun gear 17 is made larger than the center-side outer diameter edge of the first carrier pin 25. For this reason, the 2nd sun gear 17 can be enlarged, and durability can be improved.

  Next, the second stage planetary gear mechanism 32 and the output shaft have a relationship of the following second formula.

Second formula: Dsc / 2 <(Ds2 + Dp2) / 2-Dcp2 / 2
That is, the center-side outer diameter edge of the second carrier pin 26 is on the inner side than the outer diameter position of the output shaft 20 provided on the second carrier 19. In other words, the outer diameter of the output shaft 20 is set larger than the center-side outer diameter edge of the second carrier pin 26. For this reason, the output shaft 20 can be made large in diameter, torsional rigidity is increased, and it is possible to cope with high load torque.

  5, 6 and 7 are diagrams for explaining the number of first-stage and second-stage planetary gears and the diameter of the sun gear.

  FIG. 5 is a view showing the arrangement of the gears of the first stage planetary gear mechanism 31. Since the first sun gear 12 is geared directly to the rotation axis M1 of the motor M, the outer diameter is φ6 mm or less, and the first planetary gears 15 are equally divided around the circumference. This is because, since the outer diameter of the first sun gear 12 is small, as shown in FIG. 7, if four first planetary gears 15 are arranged, the first planetary gears 15 cannot interfere with each other and can not be arranged. It is.

FIG. 6 is a diagram showing the arrangement of the gears of the second stage planetary gear mechanism 32. Since the second sun gear 17 has more teeth than the first sun gear 12, the outer diameter is larger than that of the first sun gear 12. Therefore, the second planetary gears 18 can be arranged in four equal parts without mutual interference. For the internal gear 14, the first and second stages are common. FIGS. 8 and 9 are diagrams illustrating the first and second stage carriers and the planetary gear configuration.

  A radial load for rotating the carrier is generated on the carrier pin. For this reason, the carrier having a cantilever structure is likely to cause the carrier pin to be inclined, and the rotation transmission accuracy is deteriorated. On the other hand, the dual-support carrier structure has an advantage that the carrier pin is hardly inclined. In particular, when the carrier material is resin, high rigidity is remarkable by adopting a dual shaft support structure. Molding the carrier with resin enables mass production at low cost by injection molding.

  8 and 9, the first carrier 16 and the second carrier 19 have a structure with both shafts.

  First, in FIG. 8, the first carrier 16 is configured to support both end portions of the first carrier pin 25 that supports the first planetary gear 15 by two side plates of the carrier side plate A and the carrier side plate B. In the first stage, three planetary gears are arranged, and the carrier side plate A and the carrier side plate B are fixed by three carrier columns 28. The revolution rotation of the first planetary gear 15 becomes the rotation of the entire first carrier 16, and the rotation is transmitted to the second sun gear 17 integrally formed on the same axis as the carrier side plate A. In the configuration of the first formula described with reference to FIG. 4, the first carrier pin 25 and the second sun gear 17 are overlapped.

  In FIG. 9, the second carrier 19 has the same configuration as the first carrier 16, but the number of the second planetary gears 18 and carrier struts 28 is four. An output shaft 20 having spline-shaped inner teeth 20 </ b> A is formed in the carrier output portion integrally formed on the same axis as the carrier side plate A of the second carrier 19. In the configuration of the second formula described with reference to FIG. 4, the second carrier pin 26 and the output shaft are overlapped.

  10 and 11 are diagrams for explaining the configuration of the characterizing portion of the invention.

  FIG. 10 will be described. A concave-shaped dented portion 17a constituting a space is provided in a region overlapping the first carrier pin 25 at the base portion (end portion) of the second sun gear 17 on the first carrier 16 side. It is preferable that the relief portion 17 a is provided over the entire circumference of the root portion of the second sun gear 17.

  Further, a convex portion 20a that forms a space is provided in a region overlapping the second carrier pin 26 at the base portion (end portion) of the output shaft 20 on the second carrier 19 side. It is preferable that the space of the dented portion 20 a is provided over the entire circumference of the root portion of the second sun gear 17.

  Thus, by denying the root portion (end portion) that interferes with the first carrier pin 25 and the second carrier pin 26, resin molding can be performed without deteriorating the accuracy of the tooth profile shape and the spline shape.

  FIG. 11 shows the configuration of the U groove that supports the carrier pin.

  The first carrier 16 is formed with a U-shaped U-groove 16a as a support portion for supporting the first carrier pin 25, thereby improving mass productivity when resin molding is performed. Specifically, it can be molded from the side by a slide core of a mold. The second carrier 19 can be configured similarly.

  FIG. 12 is a diagram illustrating a planetary gear speed reduction device that drives a transfer belt.

  The transfer belt 41 corresponds to, for example, the intermediate transfer belt 5 provided in the electrophotographic image forming apparatus 100 described with reference to FIG. 1, and is stretched around a driving roller 42 and a plurality of driven rollers and tension rollers (not shown). The rotation of the driving roller 42 is transmitted to the transfer belt 41 by the friction between the driving roller 42 and the transfer belt 41 and is conveyed.

  The drive roller shaft 43 provided on the drive roller 42 and the output shaft 20 of the planetary gear reduction device 30 are spline coupled in the same manner as the photosensitive drum 1Y, and the rotation of the motor M is reduced by the planetary gear reduction device 30. Then, it is transmitted to the drive roller 42.

  As described above, the planetary gear speed reduction device 30 according to the present embodiment includes the first sun gear 12, the internal gear 14 arranged coaxially with the first sun gear 12, and the internal gear 14. A plurality of first planetary gears 15 arranged at equal intervals in the circumferential direction and meshing with the first sun gear 12 and the internal gear 14, and the first planetary gears 15 are rotatably supported by the first carrier pins 25. A first stage planetary gear mechanism 31 including a first carrier 16 coaxially rotatable with the first sun gear 12 and the internal gear 14, a second sun gear 17, and a second sun gear 17 are coaxial with each other. A plurality of second planetary gears 18 meshed with the second sun gear 17 and the internal gear 14 at equal intervals in the circumferential direction within the internal gear 14, The second planetary gear 18 is rotatably supported by the second carrier pin 26 and the second A second carrier gear 19 comprising a second carrier 19 coaxially rotatable with the positive gear 17 and the internal gear 14, and a second stage planetary gear mechanism 32 comprising a second stage planetary gear mechanism 31 at the second stage. The planetary gear mechanism 32 is connected, the rotational driving force from the motor M is decelerated by the first-stage planetary gear mechanism 31 and the second-stage planetary gear mechanism 32, and the output shaft 20 provided on the second carrier 19. In the planetary gear reduction device that transmits to the drum shaft 27 from the outer diameter position of the second sun gear 17, the center-side outer diameter edge of the first carrier pin 25 is located inside.

  With this configuration, the second sun gear 17 can have a large diameter, and durability can be improved. In addition, there are an effect of transmitting the rotation with high accuracy and an effect of simplifying the structure with good mass productivity.

  Further, the planetary gear speed reduction device 30 according to the present embodiment is characterized in that the center-side outer diameter edge position of the second carrier pin 26 is set to the inner side than the outer diameter position of the output shaft 20.

  With this configuration, the output shaft 20 can have a large diameter, the torsional rigidity is increased, and it is possible to cope with a high load torque.

  Further, the planetary gear reduction device 30 according to the present embodiment is formed by directly cutting the first sun gear 12 on the rotation shaft M1 of the motor M, and the first stage planetary gear mechanism 31 and the second stage planetary gear. The gear mechanism 32 includes one common internal gear 14, the first carrier pin 25 and the second carrier pin 26 are made of a metal material, and the remaining other members are made of a resin material. To do.

  With this configuration, the other members of the first carrier pin 25 and the second carrier pin 26 are made of a resin material, thereby enabling mass production at low cost by resin molding.

  Further, the planetary gear reduction device 30 according to the present embodiment forms a concave-shaped dented portion 17a at the end of the second sun gear 17 on the first carrier pin 25 side, and the second sun gear 17 and the first sun gear 17 A space is provided in an overlap portion with the carrier pin 25.

  With this configuration, it is possible to prevent the tooth profile accuracy of the second sun gear 17 from being deteriorated due to an effect such as a difference in heat shrinkage during molding.

  Further, the planetary gear speed reduction device 30 according to the present embodiment forms a concave-shaped dented portion 20a at the end of the output shaft 20 on the second carrier pin 26 side, and the output shaft 20 and the second carrier pin 26 It is characterized in that a space is provided in the overlap part.

  With this configuration, resin molding is possible without deteriorating the accuracy of the tooth profile shape or spline shape.

  The planetary gear reduction device 30 according to the present embodiment is characterized in that the number of the second planetary gears 18 is larger than the number of the first planetary gears 15.

  With this configuration, the load applied to each second planetary gear 18 can be reduced.

  In the planetary gear speed reduction device 30 according to the present embodiment, the first stage planetary gear mechanism 31 includes three first planetary gears 15, and the second stage planetary gear mechanism 32 includes the second planetary gear 18. It is characterized by having four.

  With this configuration, the load applied to each second planetary gear 18 can be reduced.

  Further, the planetary gear reduction device 30 according to the present embodiment is characterized in that the first carrier 16 and the second carrier 19 do not have a rotation support portion and perform floating rotation.

  With this configuration, alignment is more effectively exhibited and rotation is transmitted with high accuracy.

  The planetary gear speed reduction device 30 according to the present embodiment is characterized in that the output shaft 20 and the drum shaft 27 are connected by a spline coupling.

  With this configuration, the drum shaft 27 can be easily attached to and detached from the output shaft 20.

  The image forming apparatus 100 according to the present embodiment includes a motor M as a drive source for driving the drum shaft 27 and a rotational speed of the motor M in the image forming apparatus including the drum shaft 27 as a rotating body. And a planetary gear reduction device 30 described above as a reduction means.

  With this configuration, in the image forming apparatus 100 including the planetary gear reduction device 30 described above, the second sun gear 17 can have a large diameter, and durability can be improved.

  In the image forming apparatus 100 according to the present embodiment, the rotating body is the drum shaft 27 (including the photosensitive drum 1Y that rotates integrally with the drum shaft 27) on which an electrostatic latent image in the electrophotographic system is formed. Features.

  With this configuration, in the image forming apparatus 100 including the drum shaft 27 and the photosensitive drum 1Y as the rotating body, the second sun gear 17 can be increased in diameter and durability can be improved.

  As described above, the planetary gear speed reduction device and the image forming apparatus according to the present invention have the effect of improving the durability, and the drive transmission system of the electrophotographic image forming apparatus having the photosensitive drum. It is useful as a planetary gear reduction device and an image forming apparatus used in the above.

1Y, 1M, 1C, 1Bk Photosensitive drum (Rotating body)
DESCRIPTION OF SYMBOLS 10 Drive apparatus 12 1st sun gear 13 Motor fixing flange 14 Internal gear (1st internal gear, 2nd internal gear)
DESCRIPTION OF SYMBOLS 15 1st planetary gear 16 1st carrier 16a U groove 17 2nd sun gear 17a, 20a Nigue part 18 2nd planetary gear 19 2nd carrier 20 Output shaft 20A Internal tooth 21 External tooth 24 Internal tooth fixed flange 25 1st carrier pin 26 Second carrier pin 27 Drum shaft (rotating body)
30 planetary gear reduction device 31 planetary gear mechanism (first planetary gear mechanism)
32 Planetary gear mechanism (second planetary gear mechanism)
100 Image forming apparatus M Motor (drive source)
M1 rotating shaft (drive shaft)

JP 2008-151868 A JP 2001-173733 A

Claims (11)

A first sun gear, a first internal gear arranged coaxially with the first sun gear, and the first sun gear arranged at equal intervals in the circumferential direction in the first internal gear. A plurality of first planetary gears meshed with the first internal gear, the first planetary gear rotatably supported by a first carrier pin, and coaxial with the first sun gear and the first internal gear. A first planetary gear mechanism comprising: a rotatable first carrier;
A second sun gear, a second internal gear arranged coaxially with the second sun gear, and the second sun gear arranged at equal intervals in the circumferential direction in the second internal gear. A plurality of second planetary gears meshing with the second internal gear, the second planetary gear rotatably supported by a second carrier pin, and coaxial with the second sun gear and the second internal gear. A second planetary gear mechanism comprising a rotatable second carrier,
The second planetary gear mechanism is connected to the subsequent stage of the first planetary gear mechanism, the rotational driving force from the drive source is decelerated by the first planetary gear mechanism and the second planetary gear mechanism, and the second carrier In the planetary gear reduction device that transmits to the rotating body from the output shaft provided in the
A planetary gear reduction device characterized in that a center-side outer diameter edge of the first carrier pin is set to the inner side than an outer diameter position of the second sun gear.   2. The planetary gear reduction device according to claim 1, wherein a center-side outer diameter edge position of the second carrier pin is set to an inner side than an outer diameter position of the output shaft. The first sun gear is formed by cutting directly on the drive shaft of the drive source,
The first internal gear and the second internal gear are configured from one common member,
The planetary gear reduction device according to claim 1 or 2, wherein the first carrier pin and the second carrier pin are made of a metal material, and the remaining other members are made of a resin material.   A concave shape is formed at an end portion of the second sun gear on the first carrier pin side, and a space is provided in an overlap portion between the second sun gear and the first carrier pin. The planetary gear reduction device according to claim 3.   The concave portion is formed at an end portion of the output shaft on the second carrier pin side, and a space is provided in an overlap portion between the output shaft and the second carrier pin. Or the planetary gear speed reducer of Claim 4.   6. The planetary gear reduction device according to claim 1, wherein the number of the second planetary gears is greater than the number of the first planetary gears.   The planetary gear speed reduction device according to claim 6, wherein the first planetary gear mechanism includes three first planetary gears, and the second planetary gear mechanism includes four second planetary gears.   The planetary gear reduction device according to any one of claims 1 to 8, wherein the first carrier and the second carrier do not have a rotation support portion and perform floating rotation.   The planetary gear reduction device according to any one of claims 1 to 8, wherein the output shaft and the rotating body are connected by a spline coupling. In an image forming apparatus provided with a rotating body,
A driving source for driving the rotating body; and a speed reducing means for reducing the rotational speed of the driving source and transmitting the rotating speed to the rotating body;
An image forming apparatus comprising the planetary gear speed reduction device according to claim 1 as the speed reduction means.   The image forming apparatus according to claim 10, wherein the rotating body is an image carrier on which an electrostatic latent image in an electrophotographic system is formed.

Images