JP2009271223A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of suppressing banding of an output image. <P>SOLUTION: In the image forming apparatus, the tip part of an abutment pin 46 of an LPH 20 abuts on a second positioning part 72 separated by 40 to 55 degrees along the circumferential direction of an outer circumferential surface of a bearing 52 in the opposite direction with respect to the rotational direction (the direction of an arrow B) of a photoreceptor drum 16 from a first positioning part 70 where a developing roller 24 is positioned. The second positioning part 72 where the abutment pin 46 of the LPH 20 abuts thereon is the minimum deformation position where the deformation of the bearing due to a load of a developing device 22 is at the minimum. The LPH 20 exposes the photoreceptor drum 16 in a stable state without vibration, thereby suppressing the banding of an output image. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus including a light emitter in which a plurality of light emitting elements for exposing the surface of a photosensitive drum are arranged.

In the image forming apparatus described in Patent Document 1, a light emitter that extends in the axial direction of the photosensitive drum is disposed along the surface of the photosensitive drum. At both ends of the light emitter, contact pins extending toward the photosensitive drum are provided. Then, by bringing the tip of the contact pin into contact with the bearing member of the photosensitive drum, the focal length of the light emitter can be maintained at a predetermined distance, and a high quality output image can be obtained. ing.
JP 2001-130047 JP

  However, when the photosensitive drum itself vibrates, the light emitter vibrates through the contact pin, and the focal length of the light emitter changes due to the vibration of the light emitter, and streaks (so-called banding) occur in the output image. Conceivable.

  In particular, since a developing device that develops a latent image formed on the surface of the photosensitive drum as a toner image includes a driving unit such as a motor, the developing unit may vibrate the photosensitive drum. .

  An object of the present invention is to suppress banding of an output image in consideration of the above fact.

  An image forming apparatus according to claim 1 of the present invention includes a photosensitive drum on which a latent image is formed by light irradiation, and a support that is disposed at both ends of the photosensitive drum and rotatably supports the photosensitive drum. A member, a frame member that is positioned by contact with the support member, a developing unit that develops a latent image formed on the surface of the photosensitive drum to form a toner image, and the developing unit. A developing unit positioning member that positions the developing unit at a position where the latent image formed on the surface of the photosensitive drum can be developed by contacting the support member, and extends along the axial direction of the photosensitive drum. A light emitting device in which a plurality of light emitting elements that form a latent image by irradiating light on the surface of the photosensitive drum are arranged, and a load applied to the support member by the developing device is changed. To do And a light emitter positioning member that positions the light emitter at a position where the light can be irradiated onto the surface of the photosensitive drum by contacting a minimum deformation position where the deformation of the support member is minimized. And

  According to the above configuration, the supporting members disposed at both ends of the photosensitive drum rotatably support the photosensitive drum on which a latent image is formed by light irradiation. The support member is positioned in contact with the frame member.

  Further, a developing device that develops a latent image formed on the surface of the photosensitive drum to form a toner image is formed on the surface of the photosensitive drum by a positioning member provided in the developing device contacting the support member. The latent image is positioned at a position where it can be developed.

  Further, a light emitter in which a plurality of light emitting elements that form a latent image by irradiating light onto the surface of the photosensitive drum is arranged to extend along the axial direction of the photosensitive drum.

  Furthermore, the light emitter positioning member provided in the light emitter is in contact with the minimum deformation position where the deformation of the support member caused by the change in the load applied to the support member by the developing device is minimized. Accordingly, the light emitter positioning member positions the light emitter at a position where light can be irradiated onto the surface of the photosensitive drum.

  Here, when the light emitter positioning member is in contact with a position where the deformation of the support member is large, the light emitter vibrates with the deformation of the support member, and streaks (so-called banding) may occur in the output image. is there.

  However, as described above, the light emitter positioning member is in contact with the minimum deformation position where the deformation of the support member is minimum. For this reason, it is possible to prevent vibration of the light emitter and suppress banding of the output image.

  The image forming apparatus according to a second aspect of the present invention is the image forming apparatus according to the first aspect, wherein the support member is a circular bearing attached to both ends of the photosensitive drum, and the frame member is the bearing. A first abutting portion that abuts on the outer peripheral surface of the first outer peripheral surface, and a second abutting portion that is separated from the first abutting portion by 90 degrees along the circumferential direction of the outer peripheral surface. The first abutting portion or the second abutting portion abuts against the first positioning portion on the outer peripheral surface of the bearing facing across the bearing center, and the light emitter positioning member is separated from the first positioning portion. It is in contact with a second positioning portion 40 to 55 degrees apart along the circumferential direction of the outer peripheral surface in the opposite direction to the rotation direction of the photosensitive drum.

  According to the above configuration, the support member is a circular bearing attached to both ends of the photosensitive drum. The frame member includes a first contact portion that contacts the outer peripheral surface of the bearing, and a second contact portion that is 90 degrees away from the first contact portion along the circumferential direction of the outer peripheral surface of the bearing. The bearing is positioned in contact with the surface.

  Further, the developing device positioning member contacts the first positioning portion on the outer peripheral surface of the bearing facing the first contact portion or the second contact portion across the bearing center to position the developing device in position. .

  Further, the light emitter positioning member is a second positioning portion that is at a minimum deformation position 40 to 55 degrees away from the first positioning portion along the circumferential direction of the outer peripheral surface of the bearing in the direction opposite to the rotation direction of the photosensitive drum. Abut.

  By arranging in this way, vibration of the light emitter can be suppressed and banding of the output image can be suppressed.

  According to the image forming apparatus of the present invention, banding of the output image can be suppressed.

  An image forming apparatus according to a first embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 8, the image forming apparatus 10 is stretched around a plurality of rollers 12 inside a casing 11 constituting the main body, and is conveyed in the direction of arrow A by driving a motor (not shown). An endless belt-like intermediate transfer belt 14 is provided.

  The image forming apparatus 10 corresponds to the formation of a color image, and forms an image forming unit that forms toner images corresponding to four colors of yellow (Y), magenta (M), cyan (C), and black (K). 15Y, 15M, 15C, and 15K are arranged along the longitudinal direction of the intermediate transfer belt 14.

  In addition, about the member provided for each color, it adds and shows the alphabet (Y / M / C / K) which shows each color at the end of a code | symbol, but when it demonstrates without distinguishing especially a color, The description will be made by omitting the alphabet at the end of the code.

  The image forming unit 15 includes a photosensitive drum 16 that is rotated counterclockwise by a driving unit including a motor and a gear (not shown).

  Further, a charging roller 18 for uniformly charging the surface of the photosensitive drum 16 to a predetermined potential is disposed on the peripheral surface of the photosensitive drum 16. The charging roller 18 is a conductive roller, and its peripheral surface is in contact with the peripheral surface of the photosensitive drum 16, and is arranged so that the axial direction of the charging roller 18 coincides with the axial direction of the photosensitive drum 16. Has been.

  Further, on the peripheral surface on the downstream side of the charging roller 18 in the rotation direction of the photosensitive drum 16, light emission using an LED (light emitting diode) as a light emitting element for forming a latent image on the photosensitive drum 16 as a light source. An LED print head (LPH) 20 as a container extends in the axial direction of the photosensitive drum 16. Hereinafter, the LED print head 20 is referred to as LPH 20.

  As shown in FIG. 7, the LPH 20 includes a plurality of LED arrays 28 in which LED chips 30 in which a large number of LEDs are arranged in a line are arranged, and a plurality of LEDs in order to form an image of light output from the LEDs on the surface of the photoreceptor. The self-lens lens array 32 in which the rod lenses are arranged, and a rectangular parallelepiped support member 38 that supports the self-focal lens array 32 are configured.

  Specifically, the LED array 28 is configured by arranging a plurality of LED chips 30 on a printed board 28A on which a circuit for supplying various signals for controlling the driving of the LED array 28 is formed. The number of LEDs in the entire LED array 28 corresponds to the number of pixels (dots) corresponding to the resolution, for example, paper of A3 size (420 mm × 297 mm), and printing is performed at 600 dpi in the LED arrangement direction (LPH longitudinal direction). In this case, about 7020 are provided.

  Further, the LED chips 30 are arranged in the longitudinal direction of the LPH 20 (staggered arrangement) with the arrangement direction of each LED aligned with the longitudinal direction of the LPH 20, and the mounting positions are alternately shifted by a predetermined pitch (staggered arrangement). It is attached.

  Since the LED chips 30 are arranged in a staggered manner in this way, the LPH longitudinal direction positions of the LED chips 30 adjacent to each other in the longitudinal direction of the LPH 20 can be arranged in an overlapping manner, and the intervals between the LEDs may vary. There is no such thing.

  The LED chips 30 may be arranged in a line regardless of the staggered arrangement as long as the LEDs are arranged at equal intervals in the LPH longitudinal direction. May be arranged only.

  The SELFOC lens array 32 is provided between the LED array 28 and the photosensitive drum 16 as an imaging lens. The SELFOC lens array 32 is composed of, for example, refractive index distribution type rod lenses arranged at a pitch corresponding to each pixel (dot) corresponding to the resolution, and sensitizes the light beam emitted from each LED. An image is formed on the body drum 16.

  The LPH 20 having the above configuration forms a latent image on the photosensitive drum 16 by irradiating the photosensitive drum 16 with a light beam according to image data.

  Further, as shown in FIG. 8, a latent image formed on the photosensitive drum 16 is placed on a peripheral surface downstream of the LPH 20 in the rotational direction of each photosensitive drum 16 with a predetermined color (yellow / magenta / cyan). / Black) is provided with a developing device 22 for developing the toner image to form a toner image.

  The developing device 22 has a cylindrical developing roller 24 that is disposed in proximity to the photosensitive drum 16 and is rotatably provided. A developing bias is applied to the developing roller 24, and the toner loaded in the developing device 22 is attached to the peripheral surface. As the developing roller 24 rotates, the toner attached to the developing roller 24 is conveyed to the surface of the photoconductive drum 16, and the toner is rubbed against the photoconductive drum 16 to form a latent image formed on the photoconductive drum 16. It is configured to be developed.

  Details of the LPH 20 and the developing device 22 will be described later.

  Further, a transfer roller 25 for transferring the toner image on each photosensitive drum 16 to the intermediate transfer belt 14 is provided on the peripheral surface downstream of the developing device 22 in the rotation direction of each photosensitive drum 16. . The transfer roller 25 is charged to a predetermined potential and rotates clockwise to convey the intermediate transfer belt 14 at a predetermined speed and sequentially face the photosensitive drum 16. As a result, the transfer roller 25 transfers the toner on the photosensitive drum 16 onto the intermediate transfer belt 14.

  Further, a cleaning blade 26 that collects residual toner such as transfer residual toner and retransfer toner on the photosensitive drum 16 is disposed downstream of the transfer roller 25 on the peripheral surface of the photosensitive drum 16. The cleaning blade 26 is arranged so that one side is in contact with the photosensitive drum 16, and toner remaining on the photosensitive drum 16 without being transferred to the intermediate transfer belt 14, or on the photosensitive drum 16 at the time of transfer. The toner of other colors that have adhered to the toner is scraped off and collected.

  Here, the toner images of different colors formed by the image forming units 15 are transferred on the belt surface of the intermediate transfer belt 14 so as to overlap each other. As a result, a color toner image is formed on the intermediate transfer belt 14. In this embodiment, the toner image in which the four color toner images are transferred in a superimposed manner is referred to as a final toner image.

  On the downstream side of the four image forming units 15 in the transport direction of the intermediate transfer belt 14, a transfer device 34 including two rollers 34A and 34B facing each other is disposed. The final toner image formed on the intermediate transfer body belt 14 is sent between the rollers 34A and 34B, taken out from the paper tray 36 provided at the bottom of the image forming apparatus 10, and is similarly supplied to the rollers 34A and 34B. It is transferred to the sheet material P that has been conveyed in between.

  In addition, a fixing device 40 including a heating roller 40A and a pressure roller 40B is disposed in the conveyance path of the sheet material P to which the final toner image has been transferred. The sheet material P conveyed to the fixing device 40 is nipped and conveyed by the heating roller 40A and the pressure roller 40B, whereby the toner on the sheet material P melts and is pressed against the sheet material P to be fixed. .

  On the other hand, a cleaner 42 that collects toner remaining on the intermediate transfer belt 14 without being transferred to the sheet material P by the transfer device 34 is disposed downstream of the transfer device 34 in the conveyance direction of the intermediate transfer belt 14. Has been. The cleaner 42 is provided with a blade 44 so as to be in contact with the intermediate transfer body belt 14, and collects residual toner by rubbing it.

  In the image forming apparatus 10 configured as described above, an image is formed as follows.

  First, the charging roller 18 uniformly negatively charges the surface of the photosensitive drum 16 with a predetermined charging portion potential. Further, exposure is performed by the LHP 20 so that the image portion on the charged photosensitive drum 16 becomes a predetermined exposure portion potential, and a latent image is formed on the photosensitive drum 16.

  That is, a latent image corresponding to an image is formed on each photosensitive drum 16 by turning on and off the laser beam of the LHP 20 based on image data supplied from a control unit (not shown).

  Further, when the latent image on the rotating photosensitive drum 16 passes through the developing roller 24 provided in the developing device 22, the toner of the developer G adheres to the latent image by electric force, and the latent image is visualized as a toner image. The

  The visualized toner images of the respective colors are sequentially transferred to the intermediate transfer body belt 14 by the electric force of the transfer roller 25, and a color final toner image is formed on the intermediate transfer body belt 14.

  This final toner image is fed between rollers 34A and 34B provided in the transfer device 34, taken out from the paper tray 36, and transferred to the sheet material P that is also conveyed between the rollers 34A and 34B. .

  Further, the toner image transferred to the sheet material P is fixed by the fixing device 40, and the sheet material P is discharged outside the device.

  Next, the LPH 20, the developing device 22, the photosensitive drum 16, and the like will be described in detail.

  As shown in FIG. 4, the photosensitive drum 16 has a cylindrical shaft portion 50 that protrudes outward from both end faces. A drum gear (not shown) is attached to the shaft portion 50, and a rotational force is transmitted from the motor through the gear group. Further, cylindrical bearings 52 are respectively provided at both ends of the photosensitive drum 16, and the bearings 52 rotatably support the photosensitive drum 16.

  Further, a plate-like frame member 60 provided with a rectangular opening 60A is provided upright at both ends of the photosensitive drum 16, and the bearing 52 is in contact with the end surface of the opening 60A. Yes.

  Specifically, the bearings 52 are pressed against the corners of the respective openings 60A, and the first and second contact portions 62 and 64 that contact the outer peripheral surface of the bearing 52 are arranged in the circumferential direction of the outer peripheral surface. 90 degrees apart. Thereby, the bearing 52 is positioned.

  On the other hand, the developing device 22 is provided with a plate-like bracket 66 that rotatably supports the shaft portion 24A of the developing roller 24. As shown in FIG. 2, the end portion of the bracket 66 facing the photosensitive drum 16 is bent outward at a right angle, and the bent portion 66A protrudes toward the bearing 52. A pin 68 as a positioning member is provided.

  As shown in FIG. 1, the tip of the pin 68 is in contact with the first positioning portion 70 on the outer peripheral surface of the bearing 52 facing the second contact portion 64 across the center of the bearing 52. With this configuration, the developing roller 24 is positioned at a position where the latent image formed on the surface of the photosensitive drum 16 can be developed.

  As shown in FIGS. 2 and 3, the LPH 20 is disposed so as to face the photosensitive drum 16, and contact pins 46 extending toward the bearing 52 are provided at both ends of the LPH 20. Yes.

  As shown in FIG. 1, the tip of the contact pin 46 has a bearing 52 in a direction opposite to the rotational direction (arrow B direction) of the photosensitive drum from the first positioning portion 70 where the developing roller 24 is positioned. The second positioning part 72 is in contact with the second positioning part 72 separated by 40 to 55 degrees along the circumferential direction of the outer peripheral surface. With this configuration, the LPH 20 is positioned at a position where the surface of the photosensitive drum 16 can be irradiated with light.

  On the other hand, the developing device 22 is provided with a driving means for rotating the developing roller 24. This driving means becomes a vibration source, and the developing device 22 vibrates. This vibration is transmitted to the bearing 52 through the pin 68 applied to the bearing 52, whereby the bearing 52 is deformed.

  If the second positioning portion 72 of the bearing 52 with which the contact pin 46 is in contact is a part where the deformation of the bearing 52 is large, the LPH 20 vibrates with the deformation of the bearing 52, and the output image is streaked (so-called so-called). (Banding) occurs.

  However, if the second positioning portion 72 with which the contact pin 46 of the LPH 20 contacts is at the minimum deformation position where the deformation of the bearing 52 is minimum, the LPH 20 exposes the photosensitive drum 16 in a stable state without vibration. Can do.

  Here, the inventor of the present application investigated the deformation (vibration) generated in the bearing 52 by the vibration of the developing device 22 in the simulation and experiment.

  FIG. 5 shows the result of the simulation. The horizontal axis is an angle opposite to the direction in which the photosensitive drum 16 rotates, with the first positioning unit 70 where the developing unit 22 contacts the bearing 52 being 0 degrees. Are shown as 5 degrees, 10 degrees,...

  Further, regarding the vertical axis, the amplitude on the outer peripheral surface of the bearing 52 is shown. In addition, the solid line indicates the vibration amplitude in the vertical direction (X direction shown in FIG. 1), and the dotted line indicates the vibration amplitude in the horizontal direction (Y direction shown in FIG. 1). It is.

  As can be seen from the simulation results, the amplitude of the vibration in the vertical direction is 0 mm at 40 degrees, and the amplitude of the vibration in the vertical direction is 0 mm at 55 degrees. In consideration of longitudinal vibration and lateral vibration, the range of 40 to 55 degrees can be said to be the minimum deformation position.

  6 (A) and 6 (B) show the experimental results. As in FIG. 3, the horizontal axis is the angle opposite to the direction in which the photosensitive drum 16 rotates with the first positioning portion 70 as 0 degree. The vertical axis indicates the amplitude of vibration of the bearing 52.

  Note that due to the limitations of the experimental equipment, it was not possible to measure amplitudes from 0 degrees to 40 degrees.

  6A shows the amplitude in the vertical direction (X direction shown in FIG. 1), and FIG. 6B shows the amplitude in the horizontal direction (Y direction shown in FIG. 1), the same tendency as the simulation result. You can see that.

  Thus, as can be seen from the simulation and experimental results, it can be seen that the second positioning portion 72 that is 40 to 55 degrees away from the first positioning portion 70 is the minimum deformation position at which the deformation of the bearing 52 is minimum. The position where the contact pin 46 is contacted is more preferably 47.5 degrees where the vertical and horizontal vibrations are small.

  Therefore, since the LPH 20 exposes the photosensitive drum 16 in a stable state without vibration, banding of the output image can be suppressed.

  Next, the image forming apparatus 10 of the second embodiment will be described with reference to FIGS.

  In addition, about the same member as 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  In this embodiment, as shown in FIGS. 9, 10, and 11, unlike the first embodiment, the LPH 20 is disposed below the photosensitive drum 16.

  Further, the contact pin 80 extending from both ends of the LPH 20 toward the bearing 52 protrudes from the side surface of the LPH 20 and is bent into an L shape, and the tip of the contact pin 80 is in contact with the second positioning portion 72. .

  Further, an L-shaped auxiliary contact pin 84 is provided from the side opposite to the side surface of the LPH 20 from which the contact pin 80 protrudes, and the tip of the auxiliary contact pin 84 holds the LPH 20 in a balanced manner. The second positioning portion 72 is in contact with the outer peripheral surface of the bearing 52 on the opposite side.

  In this way, the LPH 20 can be disposed below the photosensitive drum 16.

FIG. 2 is a side view showing an LPH, a developing device, a photosensitive drum, and the like employed in the image forming apparatus according to the first embodiment of the present invention. 1 is an enlarged perspective view showing an LPH, a developing device, a photosensitive drum, and the like employed in an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a perspective view illustrating an LPH, a developing device, a photosensitive drum, and the like employed in the image forming apparatus according to the first embodiment of the present invention. FIG. 2 is a perspective view illustrating an LPH, a developing device, a photosensitive drum, and the like employed in the image forming apparatus according to the first embodiment of the present invention. 3 is a diagram illustrating a vibration result by simulation of a bearing employed in the image forming apparatus according to the first embodiment of the present invention. (A) (B) It is drawing which showed the vibration result by the experiment of the bearing employ | adopted as the image forming apparatus which concerns on 1st Embodiment of this invention. 1 is a perspective view showing an LPH employed in an image forming apparatus according to a first embodiment of the present invention. 1 is a schematic configuration diagram illustrating an image forming apparatus according to a first embodiment of the present invention. FIG. 5 is a side view showing an LPH, a developing device, a photosensitive drum, and the like employed in an image forming apparatus according to a second embodiment of the present invention. FIG. 5 is an enlarged perspective view showing an LPH, a developing device, a photosensitive drum, and the like employed in an image forming apparatus according to a second embodiment of the present invention. FIG. 6 is a perspective view showing an LPH, a developing device, a photosensitive drum, and the like employed in an image forming apparatus according to a second embodiment of the present invention.

Explanation of symbols

10 Image forming apparatus 16 Photosensitive drum 20 LPH (light emitting device)
22 Developer 46 Contact Pin (Light Emitter Positioning Member)
52 Bearing (support member)
60 Frame member 62 First contact portion 64 Second contact portion 68 Pin (developer positioning member)
70 First position textured portion 72 Second position textured portion 80 Contact pin (light emitting device positioning member)

Claims (2)

A photosensitive drum on which a latent image is formed by light irradiation;
A support member disposed at both ends of the photosensitive drum and rotatably supporting the photosensitive drum;
A frame member that is positioned by contacting the support member;
A developing unit for developing a latent image formed on the surface of the photosensitive drum to form a toner image;
A developing device positioning member that is provided in the developing device and positions the developing device at a position where the latent image formed on the surface of the photosensitive drum in contact with the support member can be developed;
A light emitter that extends along the axial direction of the photoconductive drum, and in which a plurality of light emitting elements that form a latent image by irradiating light on the surface of the photoconductive drum are arranged;
Light is applied to the surface of the photosensitive drum by contacting the minimum deformation position where the deformation of the support member that occurs when the load applied to the support member by the developing device changes is provided. A light emitter positioning member for positioning the light emitter in a possible position;
An image forming apparatus comprising: The support member is a circular bearing attached to both ends of the photosensitive drum,
The frame member includes a first contact portion that contacts the outer peripheral surface of the bearing, and a second contact portion that is separated from the first contact portion by 90 degrees along the circumferential direction of the outer peripheral surface,
The developing device positioning member contacts the first positioning portion or the first positioning portion of the outer peripheral surface of the bearing facing the second contact portion across the bearing center,
The light emitter positioning member is in contact with a second positioning portion that is separated from the first positioning portion by 40 to 55 degrees along the circumferential direction of the outer peripheral surface in a direction opposite to the rotation direction of the photosensitive drum. The image forming apparatus according to claim 1, wherein:

Images