JP2010019271A - Planetary differential gear reduction gear and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small planetary differential gear reduction gear capable of reducing vibration and noise, having high efficiency, and capable of highly accurately transmitting driving, without causing defection, an inclination and a twist in a planetary gear and a carrier. <P>SOLUTION: This planetary differential gear reduction gear has a sun gear 21 arranged on a motor shaft (an input shaft) 17, a planetary gear 22 meshing with its sun gear, the carrier 23 for rotatably and revolvably supporting its planetary gear around the sun gear, a fixed internal teeth gear 24 meshing with the planetary gear, and a movable internal teeth gear 25 having the tooth number different from its fixed internal teeth gear and meshing with the planetary gear similarly to the fixed internal teeth gear, and an output shaft 13 is arranged in the rotational center of the movable internal teeth gear. In such a planetary differential gear reduction gear 20, the tooth number of the fixed internal teeth gear 24 is set smaller than the tooth number of the movable internal teeth gear 25, and the sun gear 21 is meshed with the planetary gear 22 in a tooth width area B where the planetary gear 22 meshes with the movable internal teeth gear 25. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a planetary differential gear reducer that is directly connected to a drive source such as a small motor and that decelerates the rotation of a drive source input from an input shaft and outputs it from an output shaft. In addition, the present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine thereof that decelerates the rotation of a drive source and transmits it to an image carrier through such a planetary differential gear reducer. In particular, the electrophotographic processes such as charging, optical writing, development, transfer, and cleaning are repeated to form toner images on the image carrier, and the toner images are sequentially transferred to record on paper, cards, OHP films, etc. The present invention relates to an electrophotographic image forming apparatus for recording on a material.

  Conventionally, a planetary differential gear reducer is generally known as a reducer that is small and lightweight, has a high reduction ratio, and can transmit a large torque. In this kind of planetary differential gear reducer, a sun gear provided on an input shaft, a planetary gear meshing with the sun gear, a carrier that supports the planetary gear so as to rotate and revolve around the sun gear, and a planetary gear A fixed internal gear that meshes with the gear, and a movable internal gear that has a different number of teeth from the fixed internal gear and meshes with the planetary gear, and an output shaft is provided at the rotation center of the movable internal gear. The rotation of the input shaft is decelerated and output from the output shaft.

  With this configuration, when the planetary gear driven by the sun gear makes one rotation around the sun gear, the movable internal gear has only an angle of the difference in the number of teeth with respect to the fixed internal gear. It is designed not to rotate. Therefore, if the difference in the number of teeth is made small, a large torque can be transmitted with a high reduction ratio.

JP 2007-255517 A JP 2003-194158 A JP-A-5-321987

  However, in the conventional planetary differential gear reducer, the planetary gear receives a force from the three members of the sun gear, the fixed internal gear, and the movable internal gear that mesh with the planetary gear. Further, the carrier supporting the planetary gear also has a problem that twisting and tilting occur due to the force received by the planetary gear.

  For example, if it is configured as described in Patent Document 1, as shown in FIG. 8, in the movable internal gear meshing portion K1, the force a received from the sun gear and the force received from the movable internal gear are received by the planetary gear 1. Since c is applied in the opposite direction, the force for tilting the planetary gear 1 is offset, but in the fixed internal gear meshing portion K2, the force a received from the sun gear and the force b received from the fixed internal gear are in the same direction. Since it works, a large force for tilting the planetary gear 1 is applied, and the planetary gear 1 is twisted or tilted as shown by a chain line in the figure.

  For example, if it is set as the structure described in patent document 2, as shown in FIG. 7, in the movable internal gear meshing | engagement part K1, it receives from the sun gear which was offset with the force c received from a movable internal gear. As the force a disappears and the fixed internal gear meshing portion K2, the force a received from the sun gear and the force b received from the fixed internal gear similarly act on the planetary gear 1 in the same direction. A large force for inclining is applied to further increase the bending, twisting and inclination of the planetary gear 1.

  When the planetary gear 1 or the carrier is bent, tilted, twisted, or the like, the sun gear, the fixed internal gear, and the movable internal gear that mesh with the planetary gear 1 cause a single contact, and vibration and noise are generated. There is a problem that the rotational transmission accuracy and transmission efficiency from the input to the output of the movable internal gear deteriorate.

  Accordingly, a first object of the present invention is to provide a small planetary gear that is low in vibration, low noise, high efficiency, and capable of high-precision drive transmission without causing bending, tilting, twisting, or the like in the planetary gear or carrier. The object is to provide a dynamic gear reducer.

  A second object of the present invention is to provide a small planetary differential gear reducer that can achieve high-accuracy drive transmission by taking the coaxiality of an input shaft and a fixed internal gear.

  A third object of the present invention is to provide a small planetary differential gear reducer that can achieve high-accuracy drive transmission by taking the coaxiality of an input shaft and a carrier.

  A fourth object of the present invention is to provide a small planetary differential gear reducer capable of high-accuracy drive transmission by providing coaxiality between an input shaft and a movable internal gear and preventing the input shaft from bending. It is in.

  A fifth object of the present invention is to provide a small planetary gear reducer having a long life.

  A sixth object of the present invention is a small planetary differential gear capable of high-accuracy drive transmission with low vibration, low noise and high efficiency without causing bending, tilting, twisting, or the like in the planetary gear or carrier. An object of the present invention is to provide an image forming apparatus using a speed reducer.

For this reason, the invention described in claim 1 is to achieve the first object described above.
A sun gear provided on an input shaft such as a motor shaft, a planetary gear meshing with the sun gear, a fixed internal gear meshing with the planetary gear, and a fixed internal gear having a different number of teeth from the fixed internal gear In the planetary differential gear reducer provided with a movable internal gear that meshes with the planetary gear in the same manner, and an output shaft is provided at the rotation center of the movable internal gear.
The number of teeth of the fixed internal gear is less than the number of teeth of the movable internal gear,
The sun gear is meshed with the planetary gear in a tooth width region where the planetary gear meshes with the movable internal gear.

  According to a second aspect of the present invention, in order to achieve the second object described above, in the planetary differential gear reducer according to the first aspect, the input shaft projects from the boss portion of the drive source, A fixed internal gear is fixed to the boss portion so as to be fixed.

  According to a third aspect of the present invention, in order to achieve the third object described above, in the planetary differential gear reducer according to the first or second aspect, the planetary gear can rotate and revolve around the sun gear. It has a carrier to be supported, and the carrier is rotatably supported around the input shaft through a bearing.

  According to a fourth aspect of the present invention, in order to achieve the fourth object described above, in the planetary differential gear reducer according to any one of the first to third aspects, the tip of the input shaft is interposed via a bearing. It is fitted to a movable internal gear and is supported rotatably at the rotation center of the movable internal gear.

  According to a fifth aspect of the present invention, in order to achieve the fifth object, the planetary differential gear reducer according to any one of the first to fourth aspects, wherein the sun gear does not directly mesh with each other. The meshing region of the toothed gear and the planetary gear is shifted, and the region of meshing with the sun gear remains in a normal tooth shape and is not displaced.

  According to a sixth aspect of the present invention, in order to achieve the sixth object described above, rotation of a drive source such as a motor can be performed via the planetary differential gear reducer according to any one of the first to fifth aspects. An image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine thereof, which is configured to be decelerated and transmitted to an image carrier such as a photosensitive drum.

  A sun gear provided on the input shaft, a planetary gear meshing with the sun gear, a fixed internal gear meshing with the planetary gear, and a planetary gear similar to the fixed internal gear, having a different number of teeth from the fixed internal gear In a planetary differential gear reducer provided with a movable internal gear meshing with a gear and having an output shaft provided at the rotation center of the movable internal gear, the number of teeth of the fixed internal gear is the same as that of the movable internal gear. In the configuration where the number of teeth is smaller, the planetary gear receives a drag force in the direction of sandwiching both tooth surfaces from the fixed internal gear and the movable internal gear, and the meshing position between the fixed internal gear and the movable internal gear is a tooth. Since they are different in the width direction, a moment acts on the planetary gear in the tooth width direction, and the planetary gear (axial direction), the shaft, the carrier, etc. are likely to bend or tilt. Further, the planetary gear receives a force on one tooth surface from the sun gear.

  However, according to the invention described in claim 1, since the sun gear is meshed with the planetary gear in the tooth width region where the planetary gear meshes with the movable internal gear, the tooth width due to the force that the planetary gear receives from the sun gear. The direction moment and the moment due to the drag force received from the movable internal gear cancel each other, and the planetary gear (axial direction), input shaft, carrier, etc. It is possible to provide a small planetary gear reducer that can prevent generation, low noise, low vibration, high efficiency, and high-accuracy drive transmission.

  According to the second aspect of the present invention, the input shaft protrudes from the boss portion of the drive source, and the fixed internal gear is fixed to the boss portion so that the boss portion of the drive source is Thus, the coaxiality between the input shaft and the fixed internal gear can be obtained through a small planetary differential gear reducer capable of transmitting a drive with higher accuracy.

  According to invention of Claim 3, it has a carrier which supports a planetary gear rotatably and revolving around a sun gear, and the carrier is rotatably supported around an input shaft via a bearing. Therefore, it is possible to provide a small planetary gear reducer that can provide a highly accurate drive transmission by providing the coaxiality of the input shaft and the carrier via the bearing.

  According to the fourth aspect of the present invention, the tip of the input shaft is fitted to the movable internal gear via the bearing and is supported rotatably at the rotation center of the movable internal gear. In addition to providing coaxiality between the input shaft and the movable internal gear, and supporting the tip of the input shaft to prevent its bending, a small planetary differential gear reducer capable of further high-precision drive transmission is provided. be able to.

  According to the fifth aspect of the present invention, the meshing region of the fixed internal gear and the planetary gear on the side where the sun gear is not directly meshed is shifted, and the region where the sun gear is meshed is kept in a normal tooth shape and is not displaced. Therefore, by receiving the force from the sun gear in the planetary gear region that is normally formed in a tooth profile, it is possible to provide a small planetary gear reducer with improved durability and a longer life.

  According to the invention described in claim 6, in the image forming apparatus, the rotation of the drive source is decelerated and transmitted to the image carrier via the planetary differential gear reducer according to any one of claims 1 to 5. This is a small planetary differential gear that is capable of high-accuracy drive transmission with low vibration, low noise, and high efficiency without causing bending, tilting, twisting, etc. in the planetary gear or carrier. An image forming apparatus using a speed reducer can be provided.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 9 shows an overall schematic configuration of a tandem electrophotographic color copying machine which is an example of an image forming apparatus.
In the figure, reference numeral 100 is a copying machine main body, 200 is a paper feed table on which it is placed, 300 is a scanner mounted on the copying machine main body 100, and 400 is an automatic document feeder (ADF) further mounted thereon.

  The copying machine main body 100 is provided with an endless belt-like intermediate transfer belt 5 in the center. Then, as shown in the figure, it is wound around, for example, three support rollers 44, 45, and 46 so as to be able to rotate and convey clockwise in the figure. In this illustrated example, a belt cleaning device 47 that removes residual toner remaining on the intermediate transfer belt 5 after image transfer is provided to the left of the second support roller 45 among the three.

  On the intermediate transfer belt 5 stretched almost horizontally between the first support roller 44 and the second support roller 45 of the three, yellow (hereinafter referred to as “Y”) along the stretch direction. ), Magenta (hereinafter abbreviated as “M”), cyan (hereinafter abbreviated as “C”), and black (hereinafter abbreviated as “Bk”). 48Y, 48C, 48M, and 48Bk are arranged side by side to have a tandem imaging device 50. Each image forming unit 48 includes a charging unit, a developing unit, a primary transfer unit 6, a cleaning unit, a charge eliminating unit, and the like around the drum-shaped photosensitive drums 1Y, 1C, 1M, and 1Bk.

  Now, as shown in FIG. 9, optical writing means 51 is further provided on the tandem image forming device 50.

  On the other hand, a secondary transfer device 52 is provided below the stretched area of the intermediate transfer belt 5. In the illustrated example, the secondary transfer device 52 includes a secondary transfer belt 54, which is an endless belt, spanned between two rollers 53, and is pressed against a third support roller 46 to be on the intermediate transfer belt 5. Transfer the image to the recording material.

  Next to the secondary transfer device 52, a fixing device 8 for fixing the transfer image on the recording material is provided. The fixing device 8 of this example is configured by pressing a pressure roller 57 against a fixing belt 56 that is an endless belt. In the example shown in the figure, a part of the intermediate transfer belt 5 is provided so as to enter below the stretched area of the intermediate transfer belt 5.

  The secondary transfer device 52 described above is also provided with a recording material conveying function for conveying the recording material after image transfer to the fixing device 8. As the secondary transfer device, a secondary transfer roller 7 may be used as in an example described later. In addition, a non-contact charger may be disposed as the secondary transfer device. In such a case, it is difficult to provide a recording material conveyance function.

  Under the secondary transfer device 52 and the fixing device 8, a recording material reversing device 58 for reversing the recording material to form images on both sides of the recording material in parallel with the tandem image forming device 50 described above. Is provided.

  By the way, when making a copy using this color copying machine, a document is set on the document table 60 of the automatic document feeder 400. Alternatively, the automatic document feeder 400 is opened, a document is set on the contact glass 62 of the scanner 300, and the automatic document feeder 400 is closed and pressed by it.

  When a start switch (not shown) is pressed, when a document is set on the automatic document feeder 400, the document is transported and moved onto the contact glass 62, and then the scanner 300 is driven to drive the first traveling body. 63 and the second traveling body 64 travel. Then, the light from the light source is reflected by the first traveling body 63 on the original surface and directed to the second traveling body 64, and the light is reflected by the mirror of the second traveling body 64 and passes through the imaging lens 65 to the reading sensor 66. Insert and read the document contents.

  When a start switch (not shown) is pressed, one of the support rollers 44, 45, and 46 is rotationally driven by a drive motor (not shown), the other two rollers are driven to rotate, and the intermediate transfer belt 5 is rotated and conveyed. . At the same time, the photosensitive drums 1 are rotated by the individual image forming means 48 to form monochrome images of black, cyan, magenta, and yellow on the respective photosensitive drums 1 respectively. Then, along with the conveyance of the intermediate transfer belt 5, these single color images are sequentially transferred to form a composite color image on the intermediate transfer belt 5.

  On the other hand, when a start switch (not shown) is pressed, one of the paper feed rollers 72 of the paper feed table 200 is selectively rotated, the recording material is fed out from one of the paper feed cassettes 74 provided in multiple stages in the paper bank 73, and the separation roller The sheet is separated one by one at 75 and put in the sheet feeding path 76, conveyed by the conveying roller 77, led to the sheet feeding path 78 in the copying machine main body 100, and abutted against the registration roller 79 and stopped. Alternatively, the sheet feeding roller 80 is rotated to feed out the recording material on the manual feed tray 81, separated one by one by the separation roller 82, put into the manual sheet feed path 83, and abutted against the registration roller 79 and stopped.

  Then, the registration roller 79 is rotated in synchronization with the composite color image on the intermediate transfer belt 5, the recording material is fed between the intermediate transfer belt 5 and the secondary transfer device 52, and transferred by the secondary transfer device 52. A color image is formed on the recording material.

  The recording material after the image transfer is conveyed by the secondary transfer device 52 and sent to the fixing device 8, and heat and pressure are applied to the fixing device 8 to fix the transferred image. The paper is discharged by a roller 86 and stacked on a paper discharge tray 87. Alternatively, it is switched by the switching claw 85 and is put into the recording material reversing device 58, where it is reversed and guided again to the transfer position, an image is formed on the back surface, and then discharged onto the discharge tray 87 by the discharge roller 86.

  On the other hand, the intermediate transfer belt 5 after the image transfer is removed by the belt cleaning device 47 to remove residual toner remaining on the intermediate transfer belt 5 after the image transfer, so that the tandem image forming device 50 can prepare for the image formation again.

  FIG. 1 shows a schematic configuration of another example of a tandem image forming apparatus 50 used in an electrophotographic color copying machine as shown in FIG. The tandem image forming apparatus 50 shown in FIG. 1 is different from the tandem image forming apparatus 50 shown in FIG. 9 and includes a tension roller 88 in addition to the support rollers 44, 45, and 46, and presses the intermediate transfer belt 5 from the outside. Further, a secondary transfer roller 7 is used as a secondary transfer device, and a fixing device 8 includes a fixing roller 90 and a pressure roller 91. The rest of the configuration is almost the same as that of the tandem imaging apparatus 50 shown in FIG. The tandem image forming apparatus 50 employs a dry two-component developing method using a dry two-component developer, and receives image data as image information from a scanner 300 (not shown) to perform image forming processing.

  As shown in the figure, the tandem image forming device 50 is provided with four photosensitive drums 1Y, 1M, 1C, and 1Bk, which are four image carriers for black, cyan, magenta, and yellow. These photosensitive drums 1Y, 1M, 1C, and 1Bk are supported by a plurality of rotatable support rollers 44, 45, and 46 including a drive roller, and an endless belt-like intermediate transfer belt to which tension is applied by a tension roller 88. 5 are arranged side by side along the belt moving direction so as to contact 5. Further, around each photosensitive drum 1Y, 1M, 1C, 1Bk, charging means 2Y, 2M, 2C, 2Bk, developing means 9Y, 9M, 9C, 9Bk corresponding to each color, cleaning means 4Y, 4M, Electrophotographic process means such as 4C, 4Bk and static eliminating means 3Y, 3M, 3C, 3Bk are installed in the order of processes.

When a full-color image is formed by the illustrated copying machine, first, the drum surface is uniformly made by the charging means 2Y while the photosensitive drum 1Y is rotated in the direction of the arrow in the drawing by the photosensitive member driving device 12 described later. Then, based on the image data, a light beam _LY is irradiated from a light writing means 51 (not shown) to form a Y electrostatic latent image on the photosensitive drum 1Y. The Y electrostatic latent image is developed by attaching the Y toner in the developer by the developing means 9Y. At the time of development, a predetermined developing bias is applied between the developing roller of the developing unit 9Y and the photosensitive drum 1Y, and the Y toner on the developing roller is electrostatically applied to the Y electrostatic latent image portion on the photosensitive drum 1Y. Adsorbed.

  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. Then, at this 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 as the primary transfer means, and the primary transfer electric field generated by the bias application causes a photosensitivity. The Y toner image on the body drum 1Y is drawn toward the intermediate transfer belt 5 and is primarily transferred onto the intermediate transfer belt 5.

In the same manner, based on the image data, light beams L _M , L _C , and L _Bk are irradiated from an optical writing unit (not shown), and electrostatic latent images of M, C, and Bk are respectively formed on the photosensitive drums 1M, 1C, and 1Bk. An image is formed, and the electrostatic latent images are developed by the developing units 9M, 9C, and 9Bk to form an M toner image, a C toner image, and a Bk toner image, and these toner images are transferred to the primary transfer roller 6M, By 6C and 6Bk, primary transfer is performed so as to sequentially overlap the Y toner image on the intermediate transfer belt 5.

  As described above, the full-color toner image superimposed on four colors on the intermediate transfer belt 5 is conveyed to the secondary transfer position facing the secondary transfer roller 7 as the intermediate transfer belt 5 rotates. Further, a recording material such as a sheet / OHP film is conveyed to the secondary transfer position at a predetermined timing by a registration roller (not shown). A predetermined bias voltage is applied to the back surface of the recording material by the secondary transfer roller 7 at the secondary transfer position, and the secondary transfer electric field generated by the bias application and the secondary transfer roller 7 at the secondary transfer position. With this contact pressure, the full color toner image on the intermediate transfer belt 5 is secondarily transferred collectively onto the recording material. Thereafter, the recording material on which the toner image has been secondarily transferred is subjected to fixing processing by the fixing device 8 and then discharged outside the device.

FIG. 2 shows an arrangement configuration of photosensitive member driving devices for driving the photosensitive drums 1Y, 1M, 1C, and 1Bk in the color copying machine shown in FIG.
Reference numeral 10 in the drawing denotes one of a pair of main body side plates that are installed facing each other in the copying machine main body. The photoreceptor driving device 12 is fixed to the outside of the main body side plate 10 by using an attachment screw or the like. The output shaft 13 of the photoconductor driving device 12 penetrates through the main body side plate 10 and protrudes toward the inside of the main body side plate 10, and the tip is connected to the drum shaft 15 of the photoconductor drum 1 via the coupling 14. One end of 1 is supported. The other end of the photosensitive drum 1 is rotatably supported by the other, not shown, of the pair of main body side plates. The photosensitive drum 1 is rotated by driving the photosensitive member driving device 12 and rotating its output shaft 13.

FIG. 3 shows an enlarged view of the photosensitive member driving device 12 of FIG.
The photoconductor drive device 12 is configured by connecting a planetary differential gear reducer 20 to a motor 16 as a drive source with an assembly screw or the like. The motor 16 is formed such that a motor shaft 17 serving as an input shaft of the planetary differential gear reducer 20 protrudes from a boss portion 18 of the motor 16. The rotation of the motor 16 is decelerated through the planetary differential gear reducer 20 and transmitted to the photosensitive drum 1.

  The planetary differential gear reducer 20 includes a sun gear 21 provided on the motor shaft 17 that is an input shaft, three planetary gears 22 that mesh with the sun gear 21, and the planetary gears 22 that are rotatable around the sun gear 21. A revolving support carrier 23, a fixed internal gear 24 meshed with the planetary gear 22, a movable internal gear 25 having a different number of teeth from the fixed internal gear 24 and meshed with the planetary gear 22, and a movable internal gear A case 26 that covers the toothed gear 25 and is fitted to the fixed internal gear 24 is provided, and the output shaft 13 that projects from the case 26 is provided at the rotation center of the movable internal gear 25. The output shaft 13 may be provided integrally with the movable internal gear 25, or may be provided by being assembled and fixed to the movable internal gear 25 by using a separate member.

  The sun gear 21 is attached and fixed to the front end side of the motor shaft 17 so as to be an input for gear mesh transmission. In this example, three planetary gears 22 are arranged at equal intervals around the sun gear 21. Of course, it is not limited to three.

  The carrier 23 is provided with a center hole 28, and a step is formed on the outer peripheral edge of the center hole 28. The motor shaft 17 is inserted into the center hole 28, and a step is fitted to the bearing 29 attached to the base end of the motor shaft 17 and the bearing 30 attached to the distal end side, and the carrier 23 attaches the bearings 29, 30 to each other. And is rotatably supported around the motor shaft 17. The carrier 23 supports both the planetary gear shafts 31 of the planetary gears 22 to support the three planetary gears 22 so as to be rotatable and revolved around the sun gear 21.

  The fixed internal gear 24 is fixedly attached to the motor 16 by fitting the boss portion 18 of the motor 16 into the center hole thereof. The movable internal gear 25 is fitted to a bearing 32 attached to the tip of the motor shaft 17 and is supported rotatably about the motor shaft 17. The case 26 constitutes an outer frame of the planetary differential gear speed reducer 20 together with the fixed internal gear 24, is fixed by being fitted to an outer peripheral step portion of the fixed internal gear 24, and is output via the bearing 33. The output shaft 13 protrudes outward while supporting the root of the. Therefore, the movable internal gear 25 rotates while being supported by the motor shaft 17 and the case 26.

  Then, by supporting the tip of the motor shaft 17 with the movable internal gear 25 in this way, the deflection of the motor shaft 17 due to the drag received when the sun gear 21 provided on the tip side of the motor shaft 17 is driven is prevented. Can do. In addition, since the sun gear 21, the carrier 23, the fixed internal gear 24, and the movable internal gear 25 are attached with the motor shaft 17 as a center reference, each mounting eccentricity is suppressed and rotation transmission accuracy is improved. it can.

  In the illustrated planetary differential gear reducer 20, the planetary gear 22 meshes with the movable internal gear 25 simultaneously with the fixed internal gear 24, and the movable internal gear 25 has a different number of teeth from the fixed internal gear 24. The planetary gear 22 rotates every revolution of the planetary gear 22 by an angle corresponding to the difference in the number of teeth. In order to simultaneously mesh the planetary gear 22 with the fixed internal gear 24 and the movable internal gear 25 having different numbers of teeth, it is necessary to shift at least one of the three gears. This will be described in detail later.

FIG. 4 shows the meshing state of the sun gear 21, the planetary gear 22, the fixed internal gear 24, and the movable internal gear 25 as viewed from the axial direction of the motor shaft 17.
As shown in the figure, the three planetary gears 22 are supported by the carrier 23 and are equally arranged around the sun gear 21 and mesh with the sun gear 21, and at the same time, the fixed internal gear 24 and the movable internal gear 25. It is inscribed and meshed with both sides. The rotation direction differs depending on the magnitude relationship between the number of teeth of the fixed internal gear 24 and the movable internal gear 25. When the number of teeth is fixed internal gear 24 <movable internal gear 25, the rotational directions of sun gear 21 (input) and movable internal gear 25 (output) are the same, and fixed internal gear 24> movable internal gear In the case of the toothed gear 25, the sun gear 21 (input) and the movable internal gear 24 (output) rotate in opposite directions. Further, the direction of the force that the planetary gear 22 receives from the movable internal gear 25 is also reversed due to the magnitude relationship of the number of teeth.

FIG. 5 schematically shows a force relationship acting on the planetary gear 22 when the number of teeth is fixed internal gear 24 <movable internal gear 25.
S is the basic circle of the sun gear 21, circle P located at the outer periphery thereof is the basic circle of the planetary gear 22, R of the outer peripheral arc is the basic circle of the fixed internal gear 24, and M is the basic circle of the movable internal gear 25. Assuming a circle, the direction of the force acting on the teeth (tooth surface) of the planetary gear 22 is indicated by a directional arrow together with the rotation direction of each gear. a is the force received by the planetary gear 22 from the sun gear 21, b is the drag received from the fixed internal gear 24, and c is the drag received from the movable internal gear 25.

FIG. 6 shows the force relationship shown in FIG. 5 in the width direction of the planetary gear 21.
According to the present invention, the number of teeth of the fixed internal gear 24 is smaller than the number of teeth of the movable internal gear 25. With such a configuration, the planetary gear 22 receives a drag force in the direction of sandwiching both tooth surfaces from the fixed internal gear 24 and the movable internal gear 25, and the planetary gear 22 receives a force b received from the fixed internal gear 24 and A drag force c received from the movable internal gear 25 is applied as shown in FIG. According to the present invention, as shown in FIG. 3, the sun gear 21 is meshed with the planetary gear 22 in the tooth width region B where the planetary gear 22 meshes with the movable internal gear 25. Therefore, in the movable internal gear meshing portion K1, the force a received from the sun gear 21 works in the opposite direction in the same region as c to cancel each other, and the fixed internal gear meshing portion K2 is fixed to the planetary gear 1. Since only the force b received from the internal gear 24 works, the planetary gear 1 can be less bent, tilted and twisted.

  Now, in order to simultaneously mesh the planetary gear 22 with the fixed internal gear 24 and the movable internal gear 25 having different numbers of teeth, it is necessary to shift at least one of the three gears. However, when the gear is shifted, the tooth base becomes thinner in the minus shift and the tooth tip becomes thinner in the plus shift, and the strength of the teeth is weakened. Therefore, in the present invention, the region of the fixed internal gear 24 and the planetary gear 22 on the side where the sun gear 21 is not directly meshed is shifted, and the region where the sun gear 21 is meshed remains in a normal tooth shape and is not displaced. By doing so, the strength of the gear to which a large driving force is applied is maintained, and durability can be increased.

1 is a schematic configuration diagram of a tandem image forming apparatus in a tandem electrophotographic color copying machine that is an example of an image forming apparatus. FIG. FIG. 2 is an arrangement configuration diagram of a photoreceptor driving device that drives each photoreceptor drum in the color copying machine shown in FIG. 1. FIG. 3 is an enlarged partial cross-sectional view of the photoconductor driving device of FIG. 2. It is a figure which shows the meshing state of the sun gear of the same photoreceptor drive device, a planetary gear, a fixed internal gear, and a movable internal gear seeing from the axial direction of a motor shaft. In the planetary differential gear reducer of the same photoreceptor driving device, when the number of teeth of the fixed internal gear is smaller than that of the movable internal gear, it is a diagram schematically showing a force relationship acting on the planetary gear. It is a perspective view which shows the force relationship shown in FIG. 5 in the width direction of a planetary gear. In the conventional planetary differential gear reducer, it is a perspective view which shows the force which acts on a planetary gear in the width direction of a planetary gear. In another conventional planetary differential gear reducer, it is a perspective view which shows the force which acts on a planetary gear in the width direction of a planetary gear. 1 is an overall schematic configuration diagram of a tandem electrophotographic color copying machine that is an example of an image forming apparatus. FIG.

Explanation of symbols

1Y, 1M, 1C, 1Bk photosensitive drum (image carrier)
12 Photoconductor Drive Device 13 Output Shaft 16 Motor (Drive Source)
17 Motor shaft (input shaft)
18 Motor boss 20 Planetary differential gear reducer 21 Sun gear 22 Planetary gear 23 Carrier 24 Fixed internal gear 25 Movable internal gear 26 Case 29 Bearing 30 Bearing 32 Bearing 33 Bearing B The planetary gear meshes with the movable internal gear Tooth width region a Force received by the planetary gear from the sun gear b Drag received from the fixed internal gear c Drag received from the movable internal gear

Claims (6)

A sun gear provided on the input shaft, a planetary gear meshing with the sun gear, a fixed internal gear meshing with the planetary gear, and a movable internal gear meshing with the planetary gear having a different number of teeth from the fixed internal gear In a planetary differential gear reducer in which an output shaft is provided at the rotation center of the movable internal gear,
The number of teeth of the fixed internal gear is less than the number of teeth of the movable internal gear,
A planetary differential gear reducer, wherein the planetary gear is in a tooth width region where the planetary gear meshes with the movable internal gear, and the sun gear meshes with the planetary gear. The planetary differential gear reducer according to claim 1,
The planetary differential gear reducer characterized in that the input shaft protrudes from a boss portion of a drive source, and the fixed internal gear is fixed to the boss portion. The planetary differential gear reducer according to claim 1 or 2,
A carrier that rotatably supports the planetary gear and revolves around the sun gear;
The planetary differential gear reducer characterized in that the carrier is rotatably supported around the input shaft via a bearing. The planetary differential gear reducer according to any one of claims 1 to 3,
A planetary differential gear reducer characterized in that the tip of the input shaft is fitted to the movable internal gear via a bearing and is rotatably supported at the rotation center of the movable internal gear. In the planetary differential gear reducer according to any one of claims 1 to 4,
The meshing region between the fixed internal gear and the planetary gear on the side where the sun gear is not directly meshed is shifted, and the region where the sun gear is meshed is a normal tooth shape and is not displaced. To planetary differential gear reducer.   6. An image forming apparatus, wherein the rotation of a drive source is decelerated and transmitted to an image carrier through the planetary differential gear reducer according to claim 1.

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