JP2005292634A - Driving unit for image forming apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving unit for an image forming apparatus realizing high image quality by preventing an image defect such as color slurring, and an image forming apparatus. <P>SOLUTION: The gear tooth surface of an intermediate gear 47 meshed with a drum driving gear 48 connected to a photoreceptor drum 1 is formed into a crowning shape, and the intermediate gear 47 is composed of a resin member whose bending elastic modulus is equal to or under 60% of the bending elastic modulus of resin of which the drum driving gear 48 is formed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus having a function of forming an image on a recording medium such as a sheet, such as a copying machine, a printer, or a facsimile machine, and more particularly to a drive unit of the image forming apparatus. .

  In recent years, the demand for color electrophotographic image forming apparatuses capable of forming color images has increased. (1) Low running cost (2) Small space (3) Low power (4) High image quality (5) High It is expected to introduce a color image forming apparatus capable of achieving six items of speed (6) improvement in operability.

  Among them, (6) while simplifying operability, (5) high speed and (4) a technique for providing a high-quality color image, a color image forming apparatus is provided with yellow, There is a system that uses four process cartridges of magenta, cyan, and black to form four photosensitive drums in parallel to form an image, thereby improving operability and increasing the speed. This system is called a tandem or 4-drum system color image forming apparatus.

  Even in this method, (4) as a factor that hinders high image quality, rotation of the photosensitive drum is caused by minute vibration generated by meshing of the drive gear train that drives the photosensitive drum, resulting in pitch unevenness on the image. There is a problem of appearing.

  In response to this, for example, as shown in Patent Document 1, the driving gear for driving the photosensitive drum has a large diameter to reduce the pitch unevenness generated on the image, or to drive the photosensitive drum. There has been an improvement method that makes the pitch unevenness inconspicuous by limiting the meshing frequency generated by setting the number of reduction stages of the gear train to one.

Further, (4) as a factor that hinders high image quality, the positional accuracy of the four photosensitive drums and the corresponding four exposure means deteriorates, resulting in positional deviation in the scanning direction for each color. There is a problem that it appears as a color shift on the image. For this, an improvement method such as positioning all of the four photosensitive drums and the four exposure means on both side plates of the image forming apparatus main body, and minimizing the mutual positional error generated between the units. There is.
JP 2001-147618 A

  However, in the case of the prior art as described above, the following problems have occurred.

  The conventional gear configuration does not reduce the fundamental causes of pitch unevenness, but aims to make the generated pitch unevenness inconspicuous. There is a risk that pitch unevenness with a low level may occur on the image due to an increase in the meshing vibration caused by.

The large-diameter gear configuration has the effect of making the initial pitch unevenness inconspicuous, but simply reduces the pitch unevenness generated on the image (increases the gear meshing frequency) and is less than the visible sensitivity at the conventional image observation distance. Therefore, in an image forming apparatus that has higher image quality and can output color photographic images, etc., the user can view the output color photographic image by hand and observe closer than the conventional image observation distance. Since there are many opportunities to judge the output image by distance, there is a concern that a bad impression may be given to the user even at a pitch (frequency) that is lower than the visual sensitivity in the conventional configuration.

  In addition, the one-stage reduction configuration may take a configuration in which the number of teeth is reduced as much as possible by directly cutting the rotating metal shaft of the drive source such as a motor in order to increase the reduction ratio. Since the large gear of the mold is directly meshed, at the end of the main body life of the image forming apparatus, the tooth surface of the molded large gear is worn due to durability, the vibration due to the meshing of the gear increases, and the level of pitch unevenness is increased. There is a risk of getting worse.

  FIG. 10 is a schematic cross-sectional view of a main part of an image forming apparatus according to the prior art.

  Further, when the photosensitive drum 1A is positioned by the side plates (101A) of the main body of the image forming apparatus in order to minimize the color shift in the scanning direction caused by the positional shift with the exposure means, When the rotational drive to the photosensitive drum 1A is configured to transmit via the coupling 52A provided in the photosensitive member driving gear 48A arranged in a straight line with the photosensitive drum 1A, one of the photosensitive member driving gear 48A is the photosensitive drum 1A. , And the other is positioned by the main body drive unit (bearing 51A thereof), resulting in a decrease in the positional accuracy of the photoconductor drive gear 48A, and the alignment with the upstream counterpart gear 46A is extremely large. There is a risk of getting worse. In that case, the vibration at the time of meshing of the photoconductor driving gear 48A increases, causing a problem that the level of pitch unevenness deteriorates and the image quality deteriorates. If the alignment deteriorates in this way, it is difficult to obtain an effect of improving the pitch unevenness level even if a large-diameter gear configuration or a one-stage reduction configuration is adopted.

  The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to prevent image defects such as color misregistration and achieve a high image quality and a drive unit for an image forming apparatus. An object is to provide an image forming apparatus.

In order to achieve the above object, the present invention provides:
First drive transmission means;
A second drive transmission means for contacting the first drive transmission means and transmitting the driving force from the first drive transmission means to the driven transmission section;
In the drive unit of the image forming apparatus provided with
Vibration suppression that suppresses vibration when the first drive transmission means contacts the second drive transmission means to transmit the driving force to at least one of the first drive transmission means and the second drive transmission means. A feature is provided.

In the image forming apparatus,
A drive unit of the image forming apparatus described above;
An image carrier to which driving force is transmitted by being connected to the driving unit;
It is characterized by providing.

  As described above, according to the present invention, it is possible to provide a drive unit and an image forming apparatus for an image forming apparatus that prevent image defects such as color misregistration and realize high image quality.

Exemplary embodiments of the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the scope to the following embodiments.

(Overall description of image forming apparatus)
FIG. 1 is a cross-sectional view schematically showing an image forming apparatus according to an embodiment of the present invention.

  The image forming apparatus shown in FIG. 1 includes four photosensitive drums (image carriers) 1 (1a, 1b, 1c, 1d) as driven transmission portions, and around each photosensitive drum 1 The charging means 2 (2a, 2b, 2c, 2d) for uniformly charging the surface of the photosensitive drum 1 in order according to the rotation direction, and the electrostatic latent image on the photosensitive drum 1 by irradiating a laser beam based on the image information Exposure means 3 (3a, 3b, 3c, 3d) for forming the toner, developing means 4 (toner storage portions 4a1, 4b1, 4c1, 4d1, developing roller for attaching toner to the electrostatic latent image to visualize the toner image) 4a2, 4b2, 4c2, 4d2, etc.), transfer means (transfer roller) 5 (5a, 5b, 5c, 5d) for transferring the toner image on the photosensitive drum 1 to a transfer material, and the photoconductor after transfer Rolls remaining on the drum 1 surface Cleaning means 6 for removing the rear toner (6a, 6b, 6c, 6d) or the like is disposed image forming means (image forming portion) is constituted.

  Here, the photosensitive drum 1, the charging unit 2, the developing unit 4, and the cleaning unit 6 for removing the toner are integrally formed into a cartridge to form a process cartridge 7 (7 a, 7 b, 7 c, 7 d).

  Further, the transfer material S fed from the feeding unit 8 is conveyed to the image forming unit by a conveying unit 9 constituted by a conveying belt, and each color toner image is sequentially transferred to record a color image, and then the fixing unit. The image is fixed at 10 and discharged to the discharge unit 13 by the discharge roller pair 11, 12.

  In double-sided printing, before the transfer material S is fixed by the fixing unit 10 and discharged by the paper discharge rollers 11 and 12, the paper discharge rollers 11 and 12 are reversed to enter the double-sided conveyance path 15. It is conveyed (arrow A direction). The transfer material S conveyed to the double-sided conveyance path 15 passes through the oblique feeding roller 16 on the front surface of the apparatus main body, and is conveyed vertically downward to the U-turn roller 17, and an image forming unit is formed by the U-turn roller 17 and the registration roller 8 d. It is conveyed to.

  Next, the configuration of each unit will be described sequentially.

(Feeding department)
The feeding unit 8 includes a paper feed cassette 8a, a multi-feed tray 8b, a multi-feed unit 8c, and a registration roller 8d.

  The paper feed cassette 8a stores a plurality of transfer materials S and is loaded on the inner bottom of the apparatus main body. At the time of image formation from the paper cassette 8a, the transfer material S is separated and conveyed one by one by the cassette pickup roller 8a1, and conveyed to the image forming unit by the cassette conveyance roller 8a2 and the registration roller 8d.

  The multi-feed tray 8b is normally stored in front of the apparatus main body, but when used, the multi-feed tray 8b is rotated and opened from the apparatus main body, and a plurality of transfer materials S are set. At the time of image formation from the multi-feed tray 8b, the transfer material S is separated and conveyed one by one by the multi-pickup roller 8c1, and conveyed to the image forming unit by the multi-conveying roller 8c2 and the registration roller 8d.

  Separation and conveyance of paper in the paper feed cassette 8a and the multi-feed unit 8c are performed via a gear drive train by a paper feed motor (not shown) in the feed unit.

(Image formation configuration)
The photosensitive drum 1 as an image carrier is configured by applying an organic photoconductive layer (OPC) to the outer peripheral surface of an aluminum cylinder. Both ends of the photosensitive drum 1 are rotatably supported by flanges, and are driven to rotate in the counterclockwise arrow direction by transmitting a driving force from a driving motor (not shown) to one end.

  Each charging means 2 is a conductive roller formed in the shape of a roller. The roller is brought into contact with the surface of the photosensitive drum 1 and a charging bias voltage is applied by a power source (not shown) to thereby surface the surface of the photosensitive drum 1. Is uniformly charged.

  The exposure means 3 has a polygon mirror, and this polygon mirror is irradiated with image light corresponding to an image signal from a laser diode (not shown).

  The developing means 4 is adjacent to the toner storage portions 4a1, 4b1, 4c1, 4d1 that store toners of black, cyan, magenta, and yellow, respectively, and is driven to rotate by a drive unit (not shown). It comprises developing rollers 4a2, 4b2, 4c2, 4d2, etc. that perform development by applying a developing bias voltage from a developing bias power source (not shown).

  In addition, transfer members 5a, 5b, 5c, and 5d that are in contact with the transfer and transport belt 9a so as to face the four photosensitive drums 1a, 1b, 1c, and 1d are provided inside the transfer transport belt 9a, which will be described later. ing. These transfer members 5 are connected by a power supply for transfer bias (not shown), and positive charges are applied from the transfer member 5 to the transfer material via the transfer conveyance belt 9a, and contact with the photosensitive drum 1 by this electric field. The negative color toner images on the photosensitive drum 1 are sequentially transferred to the transfer material inside to form a color image.

(Transfer material transfer configuration)
The transfer material S is conveyed from the feeding unit 8 to the image forming area by the conveying unit 9.

  A transfer conveyance belt 9a as a transfer material carrier constituting the conveyance means 9 is stretched and supported by four rollers of a driving roller 9b and driven rollers 9c, 9d, 9e, and all the photosensitive drums 1a, 1b, 1c are supported. , 1d.

  The transfer conveyance belt 9 a is circulated and moved by a drive roller 9 b so that the transfer material S is electrostatically attracted to the outer peripheral surface facing the photoconductor drum 1 and the transfer material is brought into contact with the photoconductor drum 1. Thereby, the transfer material is conveyed to the transfer position by the transfer conveyance belt 9a, and the toner image on the photosensitive drum 1 is transferred.

  Further, at the most upstream position of the transfer conveyance belt 9a, an adsorption roller 9f that holds the transfer material together with the belt 9a and adsorbs the transfer material to the transfer conveyance belt 9a is disposed. When the transfer material is conveyed, a voltage is applied to the suction roller 9f to form an electric field with the opposing grounded roller 9c, and dielectric polarization is generated between the transfer conveyance belt 9a and the transfer material. The electrostatic attraction force is generated in both of them.

(Auxiliary transport configuration)
When the transfer material S is conveyed by the transfer conveyance belt 9a, the transfer material S is configured not to be peeled off from the transfer conveyance belt 9a by the auxiliary member. This auxiliary member carries the transfer material on the transfer conveyance belt 9a. As described later, it also functions as a moving means for moving the transfer conveyance belt 9a to the second position.

  Specifically, a plurality of auxiliary conveyance rollers 14 are arranged as auxiliary members that can be driven and rotated on the front side of the transfer conveyance belt 9a, and these auxiliary conveyance rollers 14 are integrated in the left-right direction by a cam mechanism (not shown). It is configured to be movable.

  When color recording is performed, the conveyance auxiliary roller 14 is retracted to the left and separated from the transfer conveyance belt 9a. On the other hand, when performing monochrome recording, the cam mechanism operates to move the conveyance auxiliary roller 14 to the right, abut against the transfer conveyance belt 9a, and push the belt 9a. As a result, the transfer / conveying belt 9a remains in contact with the black photosensitive member 1d, but is separated from the other photosensitive drums 1a, 1b, and 1c.

(Fixing part)
The fixing unit 10 fixes the image formed on the recording material by applying heat and pressure.

  Reference numeral 10a denotes a cylindrical fixing belt having an electromagnetic induction heat generating layer, which is guided by a belt guide member having a built-in magnetic field generating means including an exciting coil and a T-shaped magnetic core.

  An elastic pressure roller 10b sandwiches the fixing belt 10a and forms a fixing nip portion N having a predetermined width with a predetermined pressure contact force with a belt guide member.

  The pressure roller 10b is rotationally driven by a driving means (not shown), and the cylindrical fixing belt 10a rotates accordingly, and electromagnetic induction heat generation of the fixing belt 10a is performed by feeding power from an excitation circuit (not shown) to the excitation coil. .

  In a state where the fixing nip N rises to a predetermined temperature and is temperature-controlled, the transfer material S on which the unfixed toner image conveyed from the image forming unit is formed is the fixing belt 10a and the pressure roller 10b of the fixing nip N. The image surface faces upward, i.e., faces the fixing belt surface, and the fixing nip portion N holds the fixing nip portion N together with the fixing belt 10a with the image surface closely contacting the outer surface of the fixing belt 10a. It will be done.

  In the process in which the recording material is nipped and conveyed together with the fixing belt 10a through the fixing nip N, the unfixed toner image on the transfer material S is heated and fixed by being heated by electromagnetic induction heat of the fixing belt 10a.

(Image forming operation)
An operation when image recording is performed by the image forming apparatus having the above configuration will be described.

  First, when performing color image recording, as shown in FIG. 1, the auxiliary conveyance roller 14 is retracted to the left. In this state, the transfer conveyance belt 9a is in contact with the four photosensitive drums 1a, 1b, 1c, 1d (first position), and the transfer material fed from the feeding unit 8 is transferred to the transfer conveyance belt 9a. While being sucked and conveyed, the toner images of the respective colors are sequentially transferred by the image forming unit to form a color image, fixed by the fixing unit 10, and then discharged to the discharge unit 13.

  Next, black printing (monochrome printing) will be described.

  On the other hand, when monochrome image recording using only the black photosensitive drum 1d is selected, as shown in FIG. 2, a cam mechanism (not shown) is driven to move the auxiliary conveyance roller 14 to the right, and the roller 14 is transferred and conveyed. By pushing the belt 9a, the transfer / conveying belt 9a is separated from the other photosensitive drums 1a, 1b, and 1c except the black photosensitive drum 1d.

  In this state, the black toner image formed on the black photosensitive drum 1 d is transferred to a transfer material, fixed by the fixing unit 10, and then discharged to the discharge unit 13.

  Next, a characteristic configuration of the present embodiment will be described with reference to FIGS.

  FIG. 2 is a diagram showing a state in which the process cartridge 7 is mounted on the image forming apparatus main body, and the photosensitive drum 1 in the process cartridge 7 is positioned on the image forming apparatus main body side plate. FIG. 3 is a diagram illustrating a schematic configuration of the drive unit 103. FIG. 4 is a schematic configuration diagram illustrating a connection form between the drive unit 103 and the photosensitive drum 1. FIG. 5 is a schematic configuration diagram illustrating a connection form between the drive unit 103 and the photosensitive drum 1.

  The process cartridge 7 is a cartridge in which the photosensitive drum 1 and process means (charging device and developing device) that act on the photosensitive drum 1 are integrated into a cartridge, and the user can attach and detach the image forming apparatus main body. .

Inside the image forming apparatus main body, a guide rail portion (not shown) is provided along the attaching / detaching direction of the process cartridge 7, and the user inserts the process cartridge 7 along this direction. At this time, bearing portions 130 and 1 for rotating and supporting the photosensitive drum 1 in the process cartridge 7 are used.
When 31 hits the edge notch end surfaces 133 and 134 of the main body right side plate 101 and the main body left side plate 102, the photosensitive drum 1 and the process cartridge 7 are positioned and fixed with respect to the main body of the image forming apparatus.

  A drive unit 103 that drives the plurality of photosensitive drums 1 is positioned and fixed to the outside of the right frame (main body right side plate) 101 of the main body of the image forming apparatus on the right side in the insertion direction of the process cartridge 7.

  As shown in FIG. 3, in the drive unit 103, the drive units 103Y, 103M, 103C, and 103Bk for driving the photosensitive drums 1 of Y, M, C, and Bk colors are positioned and fixed on the drive frame 104 with high accuracy. Yes. The drive unit 103 includes a drum motor (drive source) 45 fixed to the drive frame 104, a pinion 46 fixed to the motor shaft of the motor 45, and second drive transmission means (second drive transmission member, second A drum drive gear 48 as a drive transmission gear) and an intermediate gear 47 as a first drive transmission means (first drive transmission member, first drive transmission gear) meshed with the pinion 46 and the drum drive gear 48 and rotatably supported. And a bearing 51 for supporting the drum drive gear 48 and a triangular coupling recess 52 formed at the tip of the drum drive gear 48. Here, the intermediate gear 47 constitutes a vibration suppressing unit according to the present invention.

  Here, the positioning pin holes 105 (105a, 105b) are fixed at two places on the drive frame 104, and their positions are coaxial with the central axis of the photosensitive drum 1 of each color (x = 0). The positioning pin hole (first reference hole) 105a on the Bk side is also a reference in the z direction of the drive frame 104 (z = 0), and the drive unit 103 is a main body with reference to the positioning pin hole (first reference hole) 105a. It is fixed to the right side plate 101 with screws or the like.

  As shown in FIG. 4, the main body right side plate 101 is provided with a reference pin 106 that fits into the positioning pin hole 105 of the drive unit 103. The first reference pin 106a is accurately fitted to the first reference hole 105a in both the x and z directions to position the drive unit 103, but the second reference hole 105b into which the second reference pin 106b is inserted is in the z direction. And is positioned by being fitted to the second reference pin 106b only in the xy direction.

Next, a connection configuration between the photosensitive drum 1 and the drive unit 103 will be described with reference to FIGS.

  After the user attaches the process cartridge 7 to the main body of the image forming apparatus, the rotating cam 128 rotates in conjunction with the rotating operation of bringing the transfer material carrying / conveying unit (not shown) into contact with the photosensitive drum 1. When the mating rotary cam 129 to be connected is thrust along with the drum drive gear 48 in the axial direction of the photosensitive drum 1 by the urging force of the return spring 62, the triangular coupling recess 52 formed at the tip of the drum drive gear 48 is formed. The drum driving gear 48 is positioned and fixed with respect to the photosensitive drum 1 by being connected to and fitted with a triangular coupling convex portion 37 formed on the flange 60 at the end of the photosensitive drum 1, and the drum driving gear. 48 axes are arranged on the same straight line with respect to the photosensitive drum 1.

  The triangular coupling concave portion 52 has a hole that becomes a twisted regular triangular prism, and is engaged with and disengaged from the triangular coupling convex portion 37 in the axial direction. When the triangular coupling convex portion 37 and the triangular coupling concave portion 52 are fitted, the ridge line of the twisted regular triangular prism of the triangular coupling convex portion 37 comes into contact with the twisted triangular prism surface of the triangular coupling concave portion 52, so that the triangular cup The ring convex part 37 and the triangular coupling concave part 52 are aligned so that the centers of rotation coincide.

  Further, in the above, the drum drive gear 48 during image formation has its thrust position determined at the position most moved to the process cartridge side when the bottom surface of the triangular coupling concave portion 52 and the end surface of the triangular coupling convex portion 37 abut against each other. It is supported so that it can reverse | retreat against the urging | biasing force of the return spring 62 along.

  Further, when the triangular phase of the triangular coupling convex portion 37 and the triangular coupling concave portion 52 are not matched and the triangular coupling is not connected, the end surface of the triangular coupling convex portion 37 is the mouth of the triangular coupling concave portion 52. The drum driving gear 48 is moved backward to the outside of the image forming apparatus against the urging force of the return spring 62. Then, after the process cartridge 7 is mounted, the connection is instantaneously made when the triangular phases of the triangular coupling convex portion 37 and the triangular coupling concave portion 52 are matched when the image forming apparatus main body is rotated forward.

  As described above, the drum driving gear 48 and the photosensitive drum 1 are positioned and fixed only when the triangular coupling concave portion 52 and the triangular coupling convex portion 37 are engaged with each other, and are a driving source. The rotational driving force by the drum motor 45 is transmitted to the photosensitive drum 1.

  In this configuration, the intermediate gear 47 on the upstream side of the drum drive gear 48 includes an idler shaft (shaft member) (not shown) that is caulked and supported by the drive frame 104, and a drive frame 110 (110Y, 110C,. 110M, 110Bk) is supported so as to be rotatable with high precision with respect to the pinion 46, and the alignment with respect to the pinion 46 is not deteriorated, and the rotation unevenness is minimized.

  However, the shaft (shaft member) of the drum drive gear 48 is supported on the outer side of the image forming apparatus from the gear portion by a bearing 51 fixed on the drive frame 104 so as to be rotatable with high precision with respect to the intermediate gear 47. Since the inner side of the image forming apparatus is positioned and fixed by the triangular coupling convex portion 37 formed on the flange 60 at the end of the photosensitive drum 1, the alignment with respect to the intermediate gear 47 may be deteriorated. .

In the present embodiment, the flange 60, the bearing portion 130, the main body right side plate 101, and the positioning between the support position of the inner end portion of the image forming apparatus and the support position of the outer end portion of the image forming apparatus of the drum drive gear 48. Since a total of seven parts including the pin 106, the driving frame 104, the bearing 51, and the drum driving gear 48 are interposed, the alignment of the drum driving gear 48 with respect to the intermediate gear 47 may be deteriorated by 0.1 mm or more. The nature is great. If the alignment is further deteriorated, backlash may decrease and the tooth bottom contact may occur or the tooth surface contact may occur, and when the gear tooth surface meshes, impact vibration occurs and the photosensitive drum There is a high possibility that the level of pitch unevenness on the image is deteriorated.

  Here, the gear configuration which is a feature of the present embodiment in the drive unit configuration will be mainly described with reference to FIGS. FIG. 6 is a view for explaining the shape of the gear tooth surface of the drive unit 103, and shows one tooth viewed from the axial direction and a side view of the tooth. FIG. 7 is a diagram for explaining a gear meshing state of the drive unit 103. FIG. 8 is a view for explaining the shape of the gear tooth surface of the drive unit 103.

  The pinion 46, the intermediate gear 47, and the drum drive gear 48 that transmit the rotational force from the drum motor 45, which is a drive source, to the drum drive gear 48 are each a module 0.5 and a helical gear made of a resin member with a twist angle of 20 °. Yes. In particular, the intermediate gear 47 is formed of an elastic resin member having a small bending elastic modulus, and the bending elastic modulus is different from the bending elastic modulus of the drum driving gear 48. The bending elastic modulus is about 60% or less. Further, the gear tooth surface of the intermediate gear 47 is not the ideal tooth trace shape as shown in FIGS. 6 (a) and 8 (a), but the crowning shape as shown in FIGS. 6 (d) and 8 (b). Is intentionally formed at the time of injection molding.

  At present, as a current state of normal injection molding, even if the tooth trace shape of the gear tooth surface is molded aiming at an ideal shape as shown in FIG. 6A, there is always a certain amount of tooth trace shape error (in FIG. 6). A) occurs. For example, even in a gear that has a tooth trace shape error within a certain range, as shown in FIG. 6 (c), the central part of the gear width of the gear is pulled and the tooth traces at both ends are skewed to the convex side. In such a case, a minute impact vibration is generated at the beginning and end of meshing of the gear, and is directly transmitted to the photosensitive drum, thereby causing remarkable pitch unevenness on the image.

  That is, both gears start to mesh at point c-1 in FIG. 7 (a), but at this time, both ends of the tooth trace shape shown in FIG. 6 (c) (solid line portions in FIG. 7 (a)) are in contact. At the point b-1 in FIG. 7 (a) (the point where the central portion of FIG. 6 (c) is engaged), the tooth surface of the gear is instantaneously non-contact (FIG. 7 (a)). ), And a transition from the c-1 point to the b-1 point causes an impact vibration when passing through a stepped portion having a gear tooth trace shape. The same shock vibration occurs in the transition from the point b-1 to the point d-1 in FIG.

  On the other hand, FIG. 7 (b) shows the meshing of a gear having a crowning shape formed on the tooth surface as shown in FIG. 6 (d). The point c-2 in the figure is the point where both gears start to mesh, but at this moment the end of the tooth trace is rounded by crowning, so both gears are not yet in contact, but immediately after this, smooth The gears will begin to mesh. After that, it is possible to stably engage at the central portion of the gear tooth trace until just before the point d-2 at which the mesh is disengaged through the point b-2, so that the impact vibration when passing through the step portion of the gear tooth trace shape. Does not occur and the pitch unevenness does not deteriorate. At this time, as described above, the meshing rate is slightly reduced by making the gear tooth surface a crowning shape, but the reduction is slight, and if the meshing rate is sufficiently secured in advance, it can be seen on the image. There is no negative effect on the pitch unevenness level.

In addition, even when the tooth traces at both ends of the tooth width are not out of order (FIG. 6A), the flatness of the sheet metal with the crimped shaft tilted or the shaft crimped is poor, and the parallelism between the gear shafts is out of order. In the case where the drum driving gear 48 is positioned by the photosensitive drum 1 and the other is positioned by the main body driving unit as in this embodiment, the positional accuracy of the drum driving gear 48 is reduced, and the intermediate gear Even in the case of adopting a drive transmission configuration in which the alignment with 47 may be extremely deteriorated, the same effect as described above can be obtained.

  This is because when the gear is tilted, the end of the gear tooth surface comes into contact with one side and the impact becomes large, or there is a risk that micro-vibration increases due to uneven wear. Since the crowning can realize a stable meshing by the central part of the gear tooth width, an effect of suppressing the occurrence of minute vibrations by keeping the meshing smooth can be expected. The deterioration of the parallelism between the axes causes the pitch unevenness not only in the helical gear but also in the spur gear, so that the crowning of the gear tooth surface is effective even in the image forming drive train using the spur gear.

  Furthermore, since the intermediate gear 47 is molded using an elastic resin member having a low bending elastic modulus, the bending elastic modulus is low at the start of gear engagement or at the end of gear engagement between the intermediate gear 47 and the drum drive gear 48. Since the tooth surface of the intermediate gear 47 on the gear side is bent and the effect of absorbing the impact at the time of meshing can be expected, the meshing of the gear is kept smoother, the occurrence of minute vibrations is prevented, and the pitch unevenness level on the actual image Demonstrate the effect of improving.

  The effectiveness of using the intermediate gear 47 as an elastic resin and crowning the gear tooth surface in the image forming gear train described above can be confirmed by evaluation as shown in FIG.

  FIG. 9 shows an image obtained by outputting a horizontal line image (for example, 2 dot horizontal line, 3 dot space) as an actual image and performing FFT analysis on the pitch interval unevenness of the output horizontal line. FIG. 9A is a measurement using an intermediate gear 47 which is formed with the same material as that of the drum drive gear 48 and which is a gear formed with an ideal shape as shown in FIG. (B) is a result of measuring the gear tooth surface of the intermediate gear 47 with a crowning and using an elastic resin having a bending elastic modulus of 60% or less of the material used for the drum drive gear 48 as the gear material.

  In this embodiment, the meshing frequency generated by the meshing of the intermediate gear 47 and the drum drive gear 48 is approximately 114.4 Hz. However, the intermediate gear 47 is made of an elastic resin and the gear tooth surface is crowned. Thus, it can be confirmed that the minute vibration due to the meshing of the gears is reduced and the pitch unevenness does not occur on the image.

  As described above, in the present embodiment, coupling is performed to the image carrier (corresponding to the photosensitive drum 1) positioned by the both side plates (corresponding to the main body right side plate 101 and the main body left side plate 102) of the image forming apparatus main body. Rotational drive is transmitted via (corresponding to the triangular coupling recess 52), and one end side of the image carrier driving gear (corresponding to the drum driving gear 48) arranged on the same straight line as the center of the image carrier is driven by the main body. A coupling (corresponding to the triangular coupling convex portion 37) provided on the image carrier on the other side with the gear fitted to a bearing member (corresponding to the bearing 51) provided in the unit (corresponding to the drive unit 103). ), A motor pinion gear (pinion gear) provided in the image carrier driving gear and a driving source (corresponding to the drum motor 45) in the main body structure supporting both sides of the image carrier driving gear. 46), an idler gear (corresponding to the intermediate gear 47) formed of at least one resin member is disposed between the two metal plates (corresponding to the drive frame 104 and the drive frame 110). Forms a gear both-end supported structure that caulks and supports the rotation shaft of the idler gear, and forms a front idler gear on the opposite side that meshes with the image carrier driving gear with an elastic resin member, and the gear tooth surface has a crowning shape. It is characterized by things.

  This pre-stage idler gear is made into an elastic resin, and the effect is remarkably exhibited when the flexural modulus is configured to be 60% or less of the flexural modulus of the resin forming the photosensitive member driving gear. The crowning of the tooth surface is particularly effective when the drive train is composed of a helical gear.

  Thus, by making the front idler gear into an elastic resin, the gear side tooth surface having a low bending elastic modulus is bent at the start of gear engagement or at the end of gear engagement, and the effect of absorbing the impact at the time of engagement is obtained. Therefore, one of the image carrier driving gears as described above is positioned by the image carrier supported by the both side plates of the main body, and the other is positioned by the main body driving unit and the upstream thereof. Even in the case of an image forming device with a configuration that may deteriorate due to many parts being unaligned with the side gear, it is possible to minimize the effect and improve the pitch unevenness level on the image. It becomes.

  Also, by setting the tooth surface of the gear to a crowning shape, both ends of the tooth width become smaller than the center part, so at the beginning of meshing, the timing of the normal gear starting to contact is delayed for a minute time, and meshing At the end, the separation becomes faster by a minute time, so that stable meshing by the central portion of the gear tooth width can be realized.

  When the helical gear meshes, if the tooth traces at both ends of the gear width of the gear are out of order, one end of the gear in the tooth width direction comes into contact with the mating gear and the other end separates from the mating gear. Since the meshing is finished, impact vibration is generated and transmitted directly to the photosensitive drum, which may cause significant pitch unevenness on the image. However, if the gear tooth surface is crowned, minute vibration will occur. It is possible to reduce the level of pitch unevenness that occurs on the image while suppressing the above.

  At this time, as described above, the meshing ratio of the gear tooth surface is slightly reduced by the crowning shape. However, the decrease is slight, and if the meshing ratio is sufficiently secured in advance, it is indicated on the image. There is no negative effect on the pitch unevenness level.

  In this way, at the beginning of gear meshing or at the end of gear meshing, the gear side tooth surface having a low bending elastic modulus is bent to absorb the impact at the time of meshing, and the gear tooth surface is crowned. Since stable meshing by the central portion of the gear tooth width is realized and generation of minute vibrations that occur during meshing can be suppressed, it is possible to improve the level of pitch unevenness that occurs on an actual image. Furthermore, by supporting the rotating shaft of the upstream gear with caulking with two metal plates, the alignment accuracy of the upstream gear train can be improved, and the strength of the entire drive unit can be improved. It is possible to minimize the occurrence of vibration.

  The above-described operation can be remarkably exerted in the case of an image forming apparatus having a configuration in which the alignment between the photosensitive member driving gear and its upstream gear may be extremely deteriorated as described above. . The same effect can be expected even when the parallelism between the shafts is slightly out of order due to the fall of the caulking shaft of the front idler gear and the deterioration of the flatness of the sheet metal.

  In other words, by adopting the drive unit configuration as described above, all of the four image carriers and the four exposure means are positioned by the both side plates of the image forming apparatus main body, and mutual position errors occurring between the respective units are eliminated. It is possible to improve the color misregistration in the scanning direction due to the exposure means while minimizing it, and it is possible to improve the pitch unevenness due to the gear meshing frequency, and it is possible to realize a comprehensive image quality improvement.

In this embodiment, the flexural modulus of the intermediate gear 47 is set to about 60% or less of the flexural modulus of the drum drive gear 48. However, the flexural modulus of the drum drive gear 48 is equal to the flexural modulus of the intermediate gear 47. It is good also as about 60% or less of. In the present embodiment, the gear tooth surface of the intermediate gear 47 has a crowning shape. However, the gear tooth surface of the drum drive gear 48 may have a crowning shape. Forty-eight gear tooth surfaces may be crowned.

  Further, the drive transmission means constituted by the intermediate gear 47 and the drive transmission means constituted by the drum drive gear 48 are constituted by a gear train (drive transmission member group) composed of a plurality of drive transmission gears (drive transmission members). May be. In this case, at least the drive transmission gear (drive transmission member) that contacts the intermediate gear 47 or the drum drive gear 48 among the plurality of drive transmission gears is flexibly elastic with respect to other drive transmission gears (drive transmission members). What is necessary is just to change a rate. Further, at least a gear tooth surface of the drive transmission gear (drive transmission member) that contacts the intermediate gear 47 or the drum drive gear 48 among the plurality of drive transmission gears may be crowned.

1 is a schematic cross-sectional view showing an overall configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic perspective view for explaining a configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a diagram illustrating a schematic configuration of a drive unit of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram illustrating a connection form between a drive unit and a photosensitive drum of the image forming apparatus according to the embodiment of the present invention. FIG. 2 is a schematic configuration diagram illustrating a connection form between a drive unit and a photosensitive drum of the image forming apparatus according to the embodiment of the present invention. It is a figure for demonstrating the shape of the gear tooth surface of the drive unit of the image forming apparatus which concerns on embodiment of this invention. FIG. 5 is a diagram for explaining a gear meshing state of a drive unit of the image forming apparatus according to the embodiment of the present invention. It is a figure for demonstrating the shape of the gear tooth surface of the drive unit of the image forming apparatus which concerns on embodiment of this invention. It is a figure for demonstrating the reduction effect of the minute vibration by the meshing | engagement of the gear of the drive unit of the image forming apparatus which concerns on embodiment of this invention. It is the schematic which shows the structure of the image forming apparatus which concerns on a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging means 3 Exposure means 4 Developing means 5 Transfer means 6 Cleaning means 7 Process cartridge 8 Feeding part 9 Conveying means 9a Transfer conveying belt 10 Fixing part 11, 12 Discharge roller pair 13 Discharge part 37 Triangular coupling Convex portion 45 Motor 46 Motor pinion 47 Intermediate gear 48 Drum drive gear 51 Bearing 52 Triangular coupling recess 57 Positioning portion 60 Flange 61 Fitting hole 62 Return spring 64 Drum through shaft 101 Main body right side plate 102 Main body left side plate 103 Drive unit 104, DESCRIPTION OF SYMBOLS 110 Drive frame 104a Bending part 105 Positioning pin hole 106 Positioning reference pin 128 Rotating cam 129 Opposite side rotating cam 130, 131 Bearing part 133, 134 Edge notch part

Claims (10)

First drive transmission means;
A second drive transmission means for contacting the first drive transmission means and transmitting the driving force from the first drive transmission means to the driven transmission section;
In the drive unit of the image forming apparatus provided with
Vibration suppression that suppresses vibration when the first drive transmission means contacts the second drive transmission means to transmit the driving force to at least one of the first drive transmission means and the second drive transmission means. A drive unit for an image forming apparatus, characterized in that a unit is provided. The first drive transmission means and the second drive transmission means have a first drive transmission member and a second drive transmission member, respectively, and the first drive transmission member comes into contact with the second drive transmission member to drive force. Is transmitted,
The vibration suppressing unit is one of the first drive transmission member and the second drive transmission member, and the one drive transmission member has a bending elastic modulus with respect to the other drive transmission member. The drive unit of the image forming apparatus according to claim 1, wherein the drive unit is configured by different elastic members.   The drive unit of the image forming apparatus according to claim 2, wherein a bending elastic modulus of the one drive transmission member is 60% or less of a bending elastic modulus of the other drive transmission member. At least one of the first drive transmission unit and the second drive transmission unit includes a plurality of drive transmission members that transmit a driving force,
The vibration suppressing unit is a drive transmission member that contacts at least one of the first drive transmission unit and the second drive transmission unit among the plurality of drive transmission members. The drive unit of the image forming apparatus according to claim 1, wherein the drive unit is constituted by an elastic member having a bending elastic modulus different from that of the drive transmission member.   The drive unit of the image forming apparatus according to claim 2, wherein a bending elastic modulus of the drive transmission member is 60% or less of a bending elastic modulus of the other drive transmission member. The first drive transmission means and the second drive transmission means have a first drive transmission gear and a second drive transmission gear, respectively, and the first drive transmission gear contacts the second drive transmission gear to drive force. Is transmitted,
The vibration suppression unit is at least one of the first drive transmission gear and the second drive transmission gear, and the tooth surface of the one drive transmission gear has a crowning shape. Item 2. A drive unit for an image forming apparatus according to Item 1. At least one of the first drive transmission means and the second drive transmission means has a plurality of drive transmission gears for transmitting a driving force,
The vibration suppression unit is a drive transmission gear that contacts at least one of the first drive transmission unit and the second drive transmission unit among the plurality of drive transmission gears, and has a tooth surface of the drive transmission gear. The drive unit of the image forming apparatus according to claim 1, wherein the driving unit has a crowning shape.   8. The drive unit of an image forming apparatus according to claim 6, wherein a bending elastic modulus of the drive transmission gear having the crowning shape is set to 60% or less of a bending elastic modulus of another drive transmission gear. The first drive transmission means has a shaft member supported at both ends by the unit body,
9. The second drive transmission means includes a shaft member having one end supported by the unit body and the other end connected to a rotation shaft of an image carrier having a driven transmission portion. A drive unit of the image forming apparatus according to claim 1. A drive unit of the image forming apparatus according to any one of claims 1 to 9,
An image carrier to which driving force is transmitted by being connected to the driving unit;
An image forming apparatus comprising:

Images