JP4289174B2 - Rotating body driving apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a driving device for a rotating member that drives and rotates a rotating member such as a photosensitive member, and an image forming apparatus that forms an image on the rotating photosensitive member.

  In an electrophotographic copying machine or printer, an electrostatic latent image is formed on the surface of a rotating cylindrical photosensitive member or a belt-shaped photosensitive member, and toner is applied to the formed electrostatic latent image. The toner image is adhered and developed, and the toner image is transferred and fixed on a recording sheet to obtain an image.

  Here, a cylindrical photosensitive member of the image forming apparatus, that is, a photosensitive drum or a driving roller for running the belt-like photosensitive member is referred to as a rotating member.

  When speed variation (rotation unevenness) occurs in the photosensitive drum that should rotate at a uniform speed, a phenomenon of small pitch banding occurs, and jitter and image unevenness occur in the output image.

  This is particularly noticeable in the digital electrophotographic technique in which writing on the photoconductor is performed by scanning with a semiconductor laser. The fluctuation in the rotation speed of the photoconductor becomes the speed fluctuation in the sub-scanning direction of the writing system. This causes a slight shift in the interval of the image and causes a significant decrease in image quality.

  There have been many proposals regarding techniques for improving the accuracy of driving a rotating body that should rotate at a uniform rotational speed, but the following two flows can be seen.

  One flow is to incorporate a flywheel into the drive system, and a conventional one that facilitates attachment / detachment of the flywheel is disclosed in Patent Document 1 and the like. Moreover, it is disclosed by patent document 2 etc. as what provides a flywheel in a rotary body. Further, Patent Document 3 discloses a technique for detecting the frequency characteristics of the rotating body and optimizing the moment of inertia of the flywheel in relation to the excitation frequency.

  Another major flow is to absorb the vibration in the rotational direction of the drive transmission system by using a gear, a timing belt, or a timing pulley incorporating an elastic member in the middle of the rotating body drive system. Specifically, it is disclosed in Patent Document 4 and the like.

  As described above, the use of a flywheel is the most effective technical means for improving the driving accuracy of a rotating body in the prior art. However, the device becomes larger and requires a large torque at the start of rotation. This is a fundamental problem. In addition, since the flywheel itself reduces rotational vibration due to the kinetic energy of rotation, when the rotating body is rotated at a low speed, in order to be effective, the diameter is larger than that of the rotating body. It is necessary to adopt a flywheel. Therefore, in order to avoid an increase in size of the apparatus, a functional limit has to be recognized even when a flywheel is provided in the rotating body.

  The rotation stabilizing device disclosed in Patent Document 5 is provided with a coupling member that couples a rotating member and an inertia member via a viscoelastic member at a position separated in the radial direction from the rotation center axis.

  In the rotation stabilizing device disclosed in Patent Document 6, the attachment position of the coupling member can be adjusted to a position arbitrarily selected from a plurality of positions.

The rotation drive device disclosed in Patent Document 7 includes a rotation system, a drive system, and a drive transmission system, and is provided with centrifugal pendulum type vibration absorbing means in the rotation system.
JP 7-281500 A Japanese Patent Laid-Open No. 6-130872 JP-A-8-63041 JP-A-6-249321 JP 2001-50249 A JP 2002-5237 A JP 2002-195348 A

  In the development of digital image forming apparatuses, as the performance has improved, the reproducibility of one dot line by laser writing has been strictly demanded, and the accuracy required for the drive system has also become severe. The accuracy required here is a level at which the uniformity in the sub-scanning direction of writing by laser is guaranteed in relation to the visual sensitivity of the visual system, and the recording density is 600 dpi (dpi indicates the number of dots per inch). ) To 2400 dpi, it is required to drive a rotating body with high accuracy and no rotation unevenness that satisfies a high level that small pitch banding cannot be recognized by humans.

  For this reason, in the range of the prior art, high precision gears, advanced drive control, large flywheels, and the like are generally used to increase the precision of driving the rotating body. However, the adoption of a flywheel inevitably increases the weight and equipment as described above. Furthermore, in order to provide an electrophotographic printer, the gear driving force is applied to a rotating body such as a photosensitive drum via an elastic member in order to provide a lightweight, compact, low-cost and highly accurate drive. Patent Documents 1 to 7 propose a transmission structure and the like. However, in these technologies, the elastic member alone has a large effect of reducing the speed unevenness above the natural frequency, but the gain in the resonance region becomes large, and it is greatly affected by the speed unevenness in the vicinity of the resonance region and the load fluctuation, and the banding is reduced. There was a problem getting worse.

  The present invention has a new structure that solves these problems, and is lightweight, compact, low-cost, hardly affected by vibration transmitted from the outside, uneven rotation, etc. It is an object of the present invention to provide a rotating body driving device that can contribute to image quality image formation and an image forming apparatus including the rotating body driving device.

  The above object is achieved by the following rotating body driving apparatus and image forming apparatus of the present invention.

(1) In a drive device for a rotating body that transmits the rotational driving force of a drive source to the rotating body via a drive transmission member,
The drive transmission member includes a tooth-shaped outer shape portion, a central rotation shaft portion, and a hollow space portion formed in a concave shape between the outer shape portion and the rotation shaft portion,
Attenuating means having different attenuation characteristics are arranged on both end surfaces orthogonal to the rotation shaft portion of the wall forming the lightening space portion ,
Each of the attenuating means is a disc-like shape having an opening in the center, is coaxial with the drive transmission member and is disposed outside the end face of the drive transmission member, and the inertia provision member is disposed on the drive transmission member. A viscoelastic member for holding and fixing to the end face;
A rotating body drive device that absorbs vibrations by means of damping means disposed on both end faces .

(2) The concave lightening space portion has a plurality of concave portions, and is formed by being arranged so that one side and the other side of the end surface perpendicular to the rotation shaft portion of the concave portion are alternately oriented. The rotating body drive device according to (1), characterized in that:

(3) The viscoelastic member is press-fitted into holes formed in both end faces of the drive transmission member, and is coupled to the inertia imparting member by a screw passing through the center of the hole. The rotating body drive device according to 1) or (2).

(4) The damping member according to any one of (1) to (3) , wherein different damping characteristics of the damping unit are imparted by changing a size of the inertia imparting member . Drive device.

(5) The different damping characteristics of the damping means are imparted by changing a radial distance from an axis of a fixed position between the inertia imparting member and the viscoelastic member. ) The rotating body drive device according to any one of the above.

  (6) Image formation characterized in that at least one of a photoconductor, a transfer unit, and an image reading device includes the rotating body driving device according to any one of (1) to (5). apparatus.

  Since the influence of the load fluctuation and the speed variation of the drive system can be extremely reduced by the driving device of the rotating body according to the present invention, the rotating body and the photosensitive drum for forming an image can always obtain highly accurate and stable rotation. Moreover, even when the load conditions and the line speed change, optimum vibration isolation characteristics can be obtained, so that more accurate driving is possible compared to the conventional solid type.

  The image forming apparatus provided with the driving device of the rotating body according to the present invention significantly reduces the small pitch banding, which is a major image trouble due to the rotational speed unevenness in the photosensitive member, the transfer unit, and the image reading apparatus, and has high image quality. Images can be provided stably.

  FIG. 1A is a cross-sectional view of a drive device for a rotating body, and FIG. 1B is a plan view of a drive transmission member 1. FIG. 2A is a perspective view of the drive transmission member 1 as viewed obliquely from above, and FIG. 2B is a perspective view of the drive transmission member 1 as viewed from obliquely below.

  The drive transmission member 1 having the gear portion 1G formed on the outer peripheral portion is connected to a drive transmission means (not shown) and drive transmission means such as a gear train and is rotated. The drive transmission member 1 is engaged with the rotating shaft 2 and is locked by a pin 2B planted on the rotating shaft 2. The rotating shaft 2 is fitted to a bearing 4A fixed to the substrate 3A and a bearing 4B fixed to the substrate 3B, and is rotatably supported. Ball bearings or the like are used for the bearings 4A and 4B.

  A connecting member (coupling) 5 is fitted to the upper shaft portion of the rotating shaft 2 in the figure, and by engagement between the long groove portion 5A formed in the connecting member 5 and the pin 2A fixed to the rotating shaft 2, The linear movement is possible only in the axial direction of the rotary shaft 2. The connecting member 5 is biased by the spring 6 and protrudes in the direction of the tip of the rotating shaft 5. The distal end portion of the connecting member 5 is detachably connected to a rotating shaft of a rotating body such as a photosensitive drum described later.

  The drive transmission member 1 has perforated space portions 1A and 1B for weight reduction. Holes 1 </ b> C pass through the ceiling portions of the three lightening spaces 1 </ b> A drilled below the drive transmission member 1. A viscoelastic member 7A is press-fitted into the hole 1C. A stepped screw 8A that penetrates the hole of the viscoelastic member 7A is screwed to an upper inertia imparting member (flywheel) 9A to couple the viscoelastic member 7A and the inertia imparting member 9A.

  Holes 1D pass through the bottoms of the three lightening spaces 1B drilled above the drive transmission member 1, respectively. A viscoelastic member 7B is press-fitted into the hole 1D. A stepped screw 8B passing through the hole of the viscoelastic member 7B is screwed to the lower inertia applying member 9B to couple the viscoelastic member 7B and the inertia applying member 9B. The viscoelastic members 7A and 7B and the inertia imparting members 9A and 9B constitute damping means, respectively.

  As the viscoelastic members 7A and 7B, vibration-proof rubber members made of synthetic rubber that can be elastically deformed flexibly are used. For example, chloroprene rubber (CR), ethylene propylene rubber (EPDM), silicon gel, oil-impregnated porous rubber, butyl rubber, thermoplastic elastomer, a highly functional material obtained by adding high vibration absorption performance to a thermoplastic resin, or the like is used.

As the inertia imparting members 9A and 9B, high-density metals such as stainless steel, copper, copper alloy, and lead are used , and are disk-shaped members having an opening at the center .

  The inertia imparting members 9A and 9B have the same function as the flywheel, and maintain constant speed rotation of the drive transmission member 1 by centrifugal force.

  The viscoelastic members 7 </ b> A and 7 </ b> B absorb vibration generated in the drive transmission member 1. The damping means composed of the viscoelastic members 7A and 7B and the inertia imparting members 9A and 9B is set to a frequency band within ± 10% centered on the gear 1 tooth component frequency during rotation.

The elastic members 7A and 7B and the inertia imparting members 9A and 9B are disposed on both end surfaces of the drive transmission member 1, and have different damping characteristics with respect to vibration and rotation unevenness. As shown in FIG. 1, the different damping characteristics can be obtained by changing the size of the inertia applying members 9A and 9B, or the radial distance from the axis of the fixed position between the inertia applying members 9A and 9B and the viscoelastic members 7A and 7B. It can be given by changing (shown by a one-dot chain line in FIG. 1B).

  The viscoelastic members 7A and 7B may be formed as a fluid-filled vibration-proof member in which a viscous fluid is sealed in a flexible membrane-like bag body that can be elastically deformed. The inertia imparting members 9A and 9B are fixed to the fluid-filled vibration-proof member.

  In addition, the lightening space portions 1A and 1B and the viscoelastic members 7A and 7B are not limited to the three illustrated locations. Further, the inertia imparting members 9A and 9B are not limited to the two illustrated locations.

[Image forming apparatus]
The configuration of a color printer, which is an example of an image forming apparatus equipped with the rotating body of the present invention, will be described with reference to the configuration diagram of FIG.

  The image forming apparatus A is called a tandem color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, a belt-like intermediate transfer member 16, a paper feeding device 20, and a fixing device 28. Consists of.

  On the upper part of the image forming apparatus A, an image reading apparatus B is installed. The document placed on the document table is scanned and exposed by the optical system of the document image scanning exposure apparatus of the image reading apparatus B, and read by the line image sensor. The analog signal photoelectrically converted by the line image sensor is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in the image processing unit, and then input to the exposure means 13Y, 13M, 13C, and 13K. .

  The image forming unit 10Y that forms a yellow (Y) image includes a charging unit 12Y, an exposure unit 13Y, a developing unit 14Y, and a cleaning unit 15Y disposed around the photosensitive drum (rotating body) 11Y. The image forming unit 10M that forms a magenta (M) color image includes a photosensitive drum 11M, a charging unit 12M, an exposure unit 13M, a developing device 14M, and a cleaning unit 15M. An image forming unit 10C for forming a cyan (C) color image includes a photosensitive drum 11C, a charging unit 12C, an exposure unit 13C, a developing device 14C, and a cleaning unit 15C. The image forming unit 10K that forms a black (K) image includes a photosensitive drum 11K, a charging unit 12K, an exposure unit 13K, a developing device 14K, and a cleaning unit 15K. The charging unit 12Y and the exposure unit 13Y, the charging unit 12M and the exposure unit 13M, the charging unit 12C and the exposure unit 13C, and the charging unit 12K and the exposure unit 13K constitute a latent image forming unit.

  The intermediate transfer member 16 is wound around a plurality of rollers and is rotatably supported. The images of the respective colors formed by the image forming units 10Y, 10M, 10C, and 10K are sequentially transferred (primary transfer) and synthesized by the primary transfer rollers 17Y, 17M, 17C, and 17K onto the rotating intermediate transfer body 16. A color image is formed.

  The paper S stored in the paper storage unit (paper cassette) 21 of the paper supply device 20 is supplied by a paper supply unit (first paper supply unit) 22 and supplied with paper supply rollers 23, 24, 25, 26, The color image is transferred onto the paper S (secondary transfer) through the registration roller (second paper feed unit) 27 and the like, and conveyed to the secondary transfer roller 19.

  It should be noted that the three-stage paper storage units 21 arranged vertically in the vertical direction below the image forming apparatus A have substantially the same configuration, and thus are denoted by the same reference numerals. Also, the three-stage paper feeding means 22 has almost the same configuration, and therefore is given the same reference numeral. The paper storage unit 21 and the paper supply means 22 are collectively referred to as a paper supply device 20.

  The sheet S on which the color image is transferred is fixed with a color toner image (or toner image) on the sheet S by applying heat and pressure in the fixing device 28, and then discharged from the apparatus by the sheet discharge roller 29A. Place on the paper tray 29B.

  On the other hand, in the intermediate transfer body 16, after the color image is transferred onto the paper S by the secondary transfer roller 19, the residual toner is removed by the cleaning unit 18.

  The rotating body driving device of the present invention is applicable to the photosensitive drums 11Y, 11M, 11C, and 11K of the image forming apparatus A, the secondary transfer roller 19, the exposure scanning unit of the image reading apparatus B, and the like.

  In the description of the image forming apparatus A, the color image formation has been described. However, the present invention includes a case of forming a monochrome image.

[Photosensitive drum drive unit]
Since the photosensitive drums 11Y, 11M, 11C, and 11K have substantially the same structure, they are hereinafter collectively referred to as the photosensitive drum 11.

  4A is a perspective view showing the photosensitive drum 11 and the drive mechanism 30 of the image forming apparatus A. FIG. FIG. 4B is a partial cross-sectional view of the photosensitive drum 11 and the drive mechanism 30.

  The drive mechanism 30 includes a drive motor M1 such as a pulse motor, gears G1, G2, and G3 connected thereto, and a drive transmission member 1 (see FIGS. 1 and 2). The final gear G3 of the gears G1, G2, and G3 meshes with the gear portion 1G of the drive transmission member 1 provided coaxially with the photosensitive drum 11 so as to be rotatable.

  A connecting member (coupling) 5 of a driving device for a rotating body is detachably connected to a driven transmission member (coupling) 11A attached to an end of the photosensitive drum 11. When the driven transmission member 11A of the photosensitive drum 11 is connected to the connecting member 5 of the rotating body driving device and the driving motor M1 starts driving, the gear portion 1G rotates through a gear train composed of the gears G1, G2, and G3. Then, the rotating shaft 2 that is integrated with the gear portion 1G rotates, and the photosensitive drum 11 is rotated via the connecting member 5 and the driven transmission member 11A.

  The drive transmission member 1 has its rotational speed fluctuation suppressed by the centrifugal force of the inertia imparting members 9A and 9B, and the rotary shaft 2 rotates at a constant speed. When vibration is generated during the rotation of the gears G1, G2, G3 and the gear portion 1G, the vibration is absorbed by the action of the viscoelastic members 7A and 7B and the rotation is stabilized.

  As a result, it is possible to efficiently reduce the speed unevenness in the vicinity of the resonance region and the high speed speed unevenness, and further, vibrations from the driving units of the developing devices 14Y, 14M, 14C, and 14K shown in FIG. A stable drive system that is resistant to disturbances such as load fluctuations and vibrations such as 15C and 15K and primary transfer rollers 17Y, 17M, 17C, and 17K can be obtained. Further, even when the load condition or the line speed changes, the optimum vibration isolation characteristic can be obtained and stable driving can be obtained.

[Driver for transfer means]
FIG. 5A is a cross-sectional view showing an example in which the rotational drive mechanism of the intermediate transfer body 16 of the image forming apparatus A is provided with the above-described rotational body drive device, and FIG. 5B is a plan view thereof.

  The drive mechanism includes a drive motor M2 and gears G4, G5, and G6.

  The intermediate transfer body 16 is rotated in the direction of the arrow shown by winding the rotation rollers 16B and 16C, the primary transfer rollers 17Y, 17M, 17C, and 17K, and the secondary transfer roller 19 by the rotational drive of the driving roller (rotating body) 16A. To do.

  A drive transmission member 1 equipped with the viscoelastic members 7A and 7B and the inertia applying members 9A and 9B is attached to the end of the drive roller 16A, and a drive system that is stable against disturbances such as load fluctuations and vibrations is provided. can get. Further, even when the load condition or the line speed changes, the optimum vibration isolation characteristic can be obtained and stable driving can be obtained.

  Therefore, the image transfer from the intermediate transfer body 16 to the paper S by the secondary transfer roller 19 is stably and reliably performed, and high-quality image formation is possible.

  Similarly to FIG. 4, the photosensitive belt can be driven by attaching a rotating body driving device equipped with viscoelastic members 7A and 7B and inertia applying members 9A and 9B, thereby enabling high-quality image formation by stable rotation. Become.

[Driver for Image Reading Apparatus]
FIG. 6 is a perspective view of the drive mechanism 40 of the image reading apparatus B. FIG.

  The driving mechanism 40 includes a motor M3 provided with a driving device for a rotating body similar to that described above, a driving pulley (rotating body) 42 that rotationally drives a rotating shaft 43 that is driven by the motor M3 via a timing belt 41, and a device. And an exposure unit 45 including a light source 44 and an optical system such as a mirror that are driven in the direction of the arrow shown in the figure by driving the wire 44. And a mirror unit 46.

  1 is attached to the drive transmission system of the motor M3, even if speed fluctuations occur in the drive transmission system, by attaching the rotating body drive device equipped with the viscoelastic members 7A and 7B and the inertia applying members 9A and 9B shown in FIG. Since the movement of the unit 45 and the V mirror unit 46 is stable, accurate image reading is realized.

Sectional drawing of the drive device of a rotary body, and the top view of a drive transmission member. The perspective view which looked at the drive transmission member from diagonally upward, and the perspective view which looked at the drive transmission member from diagonally downward. 1 is a configuration diagram of a color printer that is an example of an image forming apparatus equipped with a rotating body of the present invention. FIG. 3 is a perspective view illustrating a photosensitive drum and a driving mechanism of the image forming apparatus, and a partial cross-sectional view of the photosensitive drum and the driving mechanism. FIG. 4 is a cross-sectional view and a plan view showing an example in which the rotation driving mechanism of the intermediate transfer member of the image forming apparatus is provided with the rotation member driving device. The perspective view of the drive mechanism of an image reading apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drive transmission member 1A, 1B Thickening space part 1C, 1D Hole 1G Gear part 2 Rotating shaft 5 Connecting member (coupling)
6 Spring 7A, 7B Viscoelastic member 8A, 8B Stepped screw 9A, 9B Inertia imparting member (flywheel)
10Y, 10M, 10C, 10K Image forming means 11, 11Y, 11M, 11C, 11K Photosensitive drum (rotating body)
11A Driven transmission member (coupling)
16 Intermediate transfer member 16A Driving roller (rotating member)
17Y, 17M, 17C, 17K Primary transfer roller 19 Secondary transfer roller 30, 40 Drive mechanism 41 Timing belt 42 Drive pulley (rotating body)
45 Exposure unit 46 V mirror unit A Image forming apparatus B Image reading apparatus M1, M2, M3 Driving motor

Claims (6)

In the rotating body drive device that transmits the rotational driving force of the drive source to the rotating body via the drive transmission member,
The drive transmission member includes a tooth-shaped outer shape portion, a central rotation shaft portion, and a hollow space portion formed in a concave shape between the outer shape portion and the rotation shaft portion,
Attenuating means having different attenuation characteristics are arranged on both end surfaces orthogonal to the rotation shaft portion of the wall forming the lightening space portion ,
Each of the attenuating means is a disc-like shape having an opening in the center, is coaxial with the drive transmission member and is disposed outside the end face of the drive transmission member, and the inertia provision member is disposed on the drive transmission member. A viscoelastic member for holding and fixing to the end face;
A rotating body drive device that absorbs vibrations by means of damping means disposed on both end faces . The concave lightening space portion has a plurality of concave portions, and is formed by being arranged so that one side and the other side of the end surface perpendicular to the rotation shaft portion of the concave portion are alternately oriented. The rotating body drive device according to claim 1. The viscoelastic member is press-fitted into holes formed in both end faces of the drive transmission member, and is coupled to the inertia imparting member by a screw passing through the center of the hole. The rotating body drive device according to claim 1. The different attenuation properties of the damping means, the rotation of the driving device according to any one of claims 1 to 3, characterized in that it is applied by changing the magnitude of the inertial application member. 5. The different damping characteristics of the damping means are imparted by changing a radial distance from an axis of a fixed position between the inertia imparting member and the viscoelastic member. The rotating body drive device according to claim 1. 6. An image forming apparatus comprising the rotating body driving device according to claim 1 in at least one of a photosensitive member, a transfer unit, and an image reading device.

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