JP2004326085A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To always read a toner image on a belt body with high accuracy and to easily position an image reading sensor. <P>SOLUTION: The image reading sensor 21 is disposed between a driving roller 46 and a driven roller 48, facing an intermediate transfer belt 45. A supporting frame 26 is provided with a bearing part 27 which supports a shaft body 23 on at least two points, and the image reading sensor is fixed and supported on the supporting frame in the position opposing to the line connecting the above two points. The peripheral face of the shaft body is rotatably brought into contact with the intermediate transfer belt between the driving roller and the driven roller and presses the intermediate transfer belt in the direction to the image reading sensor. The intermediate transfer unit 24 can be attached to and detached from the chassis of the apparatus. When the intermediate transfer unit is attached to the chassis, the shaft body is supported by the bearing part. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, or a facsimile apparatus using an electrophotographic process, and more particularly, to an image forming apparatus having a belt for image formation.

  Generally, as an image forming apparatus, an image forming apparatus is known in which a toner image formed on a belt body is directly or indirectly transferred to a recording medium.

  As an example of such an image forming apparatus, in a so-called tandem-type color image forming apparatus in which a plurality of image forming units are arranged along an intermediate transfer belt stretched over a plurality of rollers serving as a belt body, an intermediate transfer belt is used. For example, a black (B) image forming unit, a yellow (Y) image forming unit, a magenta (M) image forming unit, and a cyan (C) image forming unit are arranged along the traveling direction of The unit is provided with a charger, a photosensitive drum serving as an image carrier, an exposure unit, a developing unit, a cleaning unit, and the like.The electrostatic latent image formed on the photosensitive drum is developed by the developing unit. The toner image formed on the photosensitive drum is transferred to the intermediate transfer belt as a primary transfer image.

  In this way, the B, Y, M, and C toner images are sequentially transferred to the intermediate transfer belt, and a color toner image is formed on the intermediate transfer belt. Then, the color toner image is transferred to a recording sheet as a secondary transfer image at a secondary transfer position, and then the color toner image on the recording sheet is fixed by a fixing unit and discharged.

  The above-described intermediate transfer belt is generally unitized as an intermediate transfer unit. For example, as shown in FIG. 4, the intermediate transfer unit includes a unit frame 11. A drive roller 46, a driven roller 48, and a tension roller 47, which are examples of the rollers, are mounted, and an intermediate transfer belt 45 is stretched over the drive roller 46, the driven roller 48, and the tension roller 47. Then, the intermediate transfer belt 45 is rotated in the direction indicated by the thick arrow in the drawing by the rotational driving of the drive roller 46.

  The position of the driven roller 48 is defined as a secondary transfer position, and although not shown, between the tension roller 47 and the drive roller 46, from the upstream side to the downstream side along the traveling direction of the intermediate transfer belt 45, For example, the B image forming unit, the Y image forming unit, the M image forming unit, and the C image forming unit are arranged in this order.

  In the above-described color image forming apparatus, a density sensor for detecting the density of the toner image (primary transfer image) transferred on the intermediate transfer belt 45 is provided, and the primary transfer image on the intermediate transfer belt 45 is converted to a secondary image. A registration sensor is provided for adjusting the timing of reaching the transfer position and the timing of transporting the recording sheet to the secondary transfer position (hereinafter, the density sensor and the registration sensor are collectively referred to as an image reading sensor). The image reading sensor eliminates an image forming error due to an environment in which the image forming apparatus is used and a component variation for each image forming apparatus.

  Incidentally, for example, an optical sensor is used as the above-described image reading sensor. In general, in an optical sensor, it is necessary to accurately adjust a focal length with an object to be measured. If the distance is deviated, the sensitivity is significantly reduced, and as a result, detection cannot be performed with high accuracy.

  As described above, the intermediate transfer belt 45 is stretched around the driving roller 46, the driven roller 48, and the tension roller 47, and is given tension by the tension roller 47 so as not to bend. On the other hand, in order to reduce the height of the intermediate transfer unit itself and to make it compact, the driven roller 48 is disposed near the tension roller 47, and is located between the driving roller 46 and the driven roller 48 (that is, the secondary transfer position). Becomes longer.

  As shown in FIG. 5, the image reading sensor 21 is attached to the support member 21 a or the like between the driving roller 46 and the driven roller 48, facing the intermediate transfer belt 45, and is transferred to the intermediate transfer belt 45. A toner image has been detected.

  However, the intermediate transfer belt 45 is generally made of rubber, and the distance between the driving roller 46 and the driven roller 48 is much longer than the distance between the driven roller 48 and the tension roller 47. As a result, the intermediate transfer belt 45 may be bent as shown by a dashed line in FIG. When such bending occurs in the intermediate transfer belt 45, the distance between the image reading sensor 21 and the intermediate transfer belt 45 is not maintained at the focal length, and the detection accuracy is reduced.

  By the way, the above-mentioned intermediate transfer unit is detachable from the image forming apparatus main body, and the intermediate transfer unit is replaced as needed. When replacing the intermediate transfer unit, it is necessary to position the image reading sensor 21 and the intermediate transfer belt 45.

  For this reason (ie, for positioning), as shown in FIGS. 7A and 7B, the image reading sensor 21 is provided on the bottom surface of the frame 22 provided in the housing (not shown) of the image forming apparatus. A receiving portion 22a that receives the rotating shaft 46a of the driving roller 46 is formed on the frame 22 when it is mounted. Then, when replacing the intermediate transfer unit 30, the drive roller rotating shaft 46a of the new intermediate transfer unit 30 is placed on the receiving portion 22a. Thus, the positioning between the intermediate transfer belt 45 and the image reading sensor 21 is performed.

  However, as shown in FIGS. 7A and 7B, even if the intermediate transfer belt 45 and the image reading sensor 21 are positioned, if the intermediate transfer belt 45 is bent as described above, the image is not obtained. The distance between the reading sensor 21 and the intermediate transfer belt 45 is not maintained at the focal length, and the detection accuracy is still reduced.

On the other hand, when the secondary transfer roller (49 in FIG. 1) moves toward and away from the intermediate transfer belt, even if vibration occurs in the intermediate transfer belt, the secondary transfer roller maintains the image reading accuracy by the image reading means. The image reading means is arranged at a position for reading the toner image transferred on the intermediate transfer belt disposed farthest from the secondary transfer position where the roller is disposed and perpendicular to the direction of separation and contact of the secondary transfer roller. (See Patent Document 1).
JP-A-2000-321838 (paragraphs (0062) to (0067), FIG. 1)

  Although the technique described in Patent Document 1 can cope with the vibration of the intermediate transfer belt that occurs when the secondary transfer roller is separated from and brought into contact with the secondary transfer roller, In addition, if the image reading means is arranged at a position for reading the toner image transferred on the intermediate transfer belt arranged in a direction perpendicular to the direction of separation and contact of the secondary transfer roller, the influence of vibration in the vertical direction on the image surface can be obtained. Is the smallest in terms of reading accuracy, but no consideration is given to the bending of the intermediate transfer belt itself, and furthermore, as in Patent Document 1, when an image reading sensor is arranged to face the driving roller, There is also a problem of being affected by rotational driving.

  Furthermore, Patent Document 1 does not consider the positioning of the intermediate transfer unit and the image reading sensor at all, and has a problem that the space near the driving roller is extremely narrow and it is difficult to arrange the image reading sensor. .

  In any case, in the conventional image forming apparatus, the image reading (image detection) cannot be performed accurately due to the bending of the intermediate transfer belt, and the positioning of the intermediate transfer belt and the image reading sensor is difficult. is there.

  An object of the present invention is to provide an image forming apparatus capable of reading a toner image on an intermediate transfer belt with high accuracy.

  Another object of the present invention is to provide an image reading device in which the positioning of the image reading sensor is easy.

  According to the present invention, one of a photoreceptor belt, an intermediate transfer belt, or a transfer belt for transferring a toner image to a recording medium, which is housed in the apparatus housing, and drives the belt member. A drive roller, a driven roller, and a tension roller that applies tension to the belt body at a position farther from the drive roller than the driven roller, and a distance between the drive roller and the driven roller is such that the driven roller is Image detecting means configured to be longer than the distance between the tension rollers, disposed between the driving roller and the driven roller, facing the belt member, and detecting a primary transfer image on the belt member; And a contact member that presses the belt body toward the image detection unit while facing the image detection unit in a state where the belt body is in contact with the image detection unit. The image forming apparatus is obtained, wherein the door.

  As described above, the image detecting means (image reading sensor) for detecting the primary transfer image on the belt body (intermediate transfer belt) facing the belt body between the driving roller and the driven roller is disposed and brought into contact therewith. When the belt body is pressed against the image detecting means while the member is in contact with the belt body with the belt body facing the image detecting means, the belt body is less likely to be bent, Or, even if vibration or the like occurs, the distance between the image detecting means and the contact member does not change, and the distance between the image detecting means and the belt body can be always kept constant, and the detection accuracy does not decrease.

  For example, the belt body, the driving roller, the driven roller, and the tension roller are integrated as a belt unit, and the contact member is incorporated in the belt unit.

  In this way, if the belt body, the driving roller, the driven roller, and the tension roller are integrated as a belt unit, and the contact member is incorporated in the belt unit, the distance between the image detecting means and the belt body can be easily fixed at all times. Can be maintained.

  Further, in the present invention, the contact member is a shaft body, and the shaft body is in contact with the belt body between the drive roller and the driven roller so as to be rotatable with the belt body. A support frame on which the image detection unit is mounted, wherein the support frame is provided with a receiving portion that supports the shaft body at at least two points, and the image detection unit includes: It is fixed and supported by the support frame at a position facing a line connecting the two points. The belt unit is detachable from the device housing. When the belt unit is mounted on the device housing, the shaft is supported by the receiving portion.

  In this way, using the shaft body as the abutting member, the peripheral surface of the shaft body abuts on the belt body between the drive roller and the driven roller in a rotatable state, and is supported by the apparatus housing. The image detection means is mounted on the support frame, and the support frame defines a receiving portion for supporting the shaft body at at least two points, and the image detection means is fixed and supported by the support frame at a position facing a line connecting the two points. If the shaft unit is supported by the receiving portion when the belt unit is mounted on the apparatus housing, the positioning between the shaft unit and the image detecting means becomes easy, and the distance between the image detecting means and the belt body is reduced. It can always be kept in a constant state, and the detection accuracy does not decrease.

  As described above, according to the present invention, the image detecting means (image reading sensor) for detecting the primary transfer image on the belt body facing the belt body is disposed between the driving roller and the driven roller. In a state where the contact member is in contact with the belt body, the belt body is pressed to the image detection means side with the image detection means and the belt body interposed therebetween, so that the belt body is less likely to be bent, Even if bending or vibration occurs, the distance between the image detecting means and the contact member does not change, and the distance between the image detecting means and the belt body can always be kept constant, and the detection accuracy does not decrease. This has the effect.

  In the present invention, since the belt member, the driving roller, the driven roller, and the tension roller are integrated as an intermediate transfer unit, and the contact member is incorporated in the intermediate transfer unit, the distance between the image detecting means and the belt member can be easily reduced. There is an effect that a constant state can be always maintained.

  In the present invention, the shaft body is used as the abutting member, and the peripheral surface of the shaft body abuts on the belt body between the driving roller and the driven roller in a rotatable state. The image detecting means is mounted on the support frame, the receiving portion is defined so as to support the shaft body at at least two fulcrums on the support frame, and the image detecting means is fixed to the support frame at a position facing a line connecting the fulcrums. When the intermediate transfer unit is mounted on the apparatus casing, the shaft is supported by the receiving portion, so that the positioning between the shaft and the image detecting means is easy, and the image detecting means and the belt Has a constant effect that the detection accuracy is not reduced.

  Hereinafter, embodiments of the present invention will be illustratively described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention to them, unless otherwise specified, and are merely mere descriptions. This is just an example.

  Referring to FIG. 1, the illustrated image forming apparatus includes a plurality of image forming units 41 to 44, each of which has a photosensitive drum (image carrier) 41a to 44a and a toner. Containers 41b to 44b are provided.

  In the illustrated example, the image forming units 41, 42, 43, and 44 correspond to black (B), yellow (Y), magenta (M), and cyan (C), respectively. 44, that is, the photoconductor drums 41a to 44a are arranged along the feeding direction (conveyance path) of the intermediate transfer belt 45 as a belt body, and the photoconductor drum 41a is located on the most upstream side, and the photoconductor drum is on the most downstream side. The drum 44a is located.

  The intermediate transfer belt 45 is supported by the driving roller 46, the tension roller 47, and the driven roller 48. As described above, the driving roller 46, the tension roller 47, and the driven roller 48 are supported by the unit frame 11, and Is composed. (See FIG. 4) The intermediate transfer unit is detachably mounted on the housing 32 of the image forming apparatus. The intermediate transfer belt 45 is driven by a driving roller 46 in a direction indicated by a solid line arrow in the drawing, and a predetermined tension (tension) is applied by a tension roller 47 as described later.

  When the intermediate transfer unit is mounted on the image forming apparatus housing 32, the driven roller 48 is arranged to face the secondary transfer roller 49. A primary transfer section is defined between the drive roller 46 and the tension roller 47, and the above-described image forming units 41, 42, 43, and 44 are arranged along the primary transfer section.

  As illustrated, the intermediate transfer belt 45 is inclined upward from the left side to the right side in the drawing at the primary transfer portion. That is, the intermediate transfer belt 45 is inclined upward from the photosensitive drum 41a toward the photosensitive drum 44a. The driven roller 48 is disposed near the lower side of the photosensitive drum 41a in the vertical direction. As a result, the driven roller 48 is disposed close to the tension roller 47.

  When an image is formed on a recording medium (recording paper), a toner image is formed on the photosensitive drums 41a to 44a in synchronization with the feeding of the intermediate transfer belt 45. Then, the toner image is sequentially primary-transferred onto the intermediate transfer belt 45 to form a primary transfer image. The recording paper (not shown) is reversed from the paper supply unit 60 by the paper reversing roller 61, conveyed along the recording medium conveyance path 62 via the registration roller 62a, and sent to the secondary transfer position. The recording sheet is sandwiched between the driven roller 48 and the secondary transfer roller 49 together with the intermediate transfer belt 45, and the toner image (primary transfer image) is secondarily transferred to the recording sheet by the secondary transfer roller 49. The secondary transfer roller 49 is fixed to the intermediate transfer belt differently from the related art, and applies a transfer bias voltage having a polarity opposite to that during image formation during the secondary transfer to the recording paper. The voltage is applied to the transfer roller 49 to prevent the secondary transfer roller 49 from being stained by toner.

  Thereafter, the recording sheet is sent to a fixing device (fixing roller pair) 63, where the recording sheet is fixed, and then the recording sheet is discharged to a discharge tray 64 by a conveyance roller 63a and a discharge roller 64a. Note that the recording paper may be manually inserted into the recording medium transport path 62 using the manual feeding roller 61a.

  Referring to FIG. 2 as well, an image reading sensor 21 is disposed between the driving roller 46 and the driven roller 48 so as to face the intermediate transfer belt 45. The image reading sensor 21 is provided in the housing of the image forming apparatus. It is fixed to a mounting support (support frame) 25 which is a component of the body 32 (not shown in FIG. 2). Then, the toner image on the intermediate transfer belt 45 is read by the image reading sensor 21, and, for example, drive timing control of a registration roller and image density adjustment are performed.

  A shaft member 23 having a circular cross section is disposed at a position facing the image reading sensor 21 with the intermediate transfer belt 45 interposed therebetween, and the shaft member 23 has a peripheral surface abutting on the inner side surface of the intermediate transfer belt 45. 2, the intermediate transfer belt 45 is pressed in the direction of the image reading sensor 21 as indicated by a solid arrow.

  The shaft body 23 is supported by a unit frame (not shown) of the intermediate transfer belt unit so as to be rotatable around its axis. When the intermediate transfer unit is mounted on the housing of the image forming apparatus, the shaft body 23 is moved to the intermediate transfer belt 45. Is positioned at a position facing the image reading sensor 21 with the. The peripheral surface of the shaft body 23 is coated with fluorine or molybdenum.

  In this way, the intermediate transfer belt 45 is pressed toward the image reading sensor 21 by the shaft member 23 between the driving roller 46 and the driven roller 48, and the image reading sensor 21 Since the image reading sensor 21 faces the body 23, that is, the image reading sensor 21 detects and reads an image on the intermediate transfer belt 45 located on the shaft body 23, the intermediate transfer belt 45 is bent. The distance between the image reading sensor 21 and the shaft body 23 does not change even if bending, vibration, or the like occurs (that is, the distance between the image reading sensor 21 and the intermediate transfer belt 45 on the shaft body 23). (The distance does not change), the distance between the image reading sensor 21 and the intermediate transfer belt 45 can always be maintained at the focal length, and the detection accuracy decreases. That there is no.

  Here, referring to FIGS. 3A and 3B, in the illustrated example, the image reading sensor 21 is fixedly supported by a support frame 26. The support frame 26 has a bottom plate 26a, and flanges 26b and 26c extending from both ends of the bottom plate 26a in directions orthogonal to the bottom plate 26a, respectively. It is defined to be longer than the width of the unit 24. The support frame 26 is a component of the housing of the image forming apparatus.

  At the upper ends of the flange portions 26a and 26c, receiving portions 27 (only one receiving portion is shown in FIGS. 3A and 3B) are formed to face each other. The shaft body 23 is supported by the receiving portion 27. The image reading sensor 21 is disposed on the upper surface of the bottom plate portion 26a such that the center of the image reading sensor 21 is located on a perpendicular line drawn from a straight line connecting the receiving portions 27 to the bottom plate portion 26a.

  As described above, the intermediate transfer unit 24 is detachable from the housing of the image forming apparatus. When the intermediate transfer unit 24 is mounted on the housing of the image forming apparatus, the shaft member 23 is attached to the receiving portion 27. The intermediate transfer unit 24 is mounted on the housing of the image forming apparatus such that

  When the intermediate transfer unit 24 is mounted on the housing of the image forming apparatus in this manner, the shaft body 23 is necessarily located on the line connecting the receiving portions 27, and the image reading sensor 21 is located immediately below this line. Is fixed, the positioning between the shaft body 23 and the image-type reading sensor 21 can be easily performed, and the image detection accuracy does not decrease as described above.

  In the present embodiment, an image forming apparatus using an intermediate transfer belt as an example of a belt body has been described. However, the present invention is applicable to a transfer belt and a photosensitive belt as other examples of the belt body. Needless to say.

FIG. 1 is a configuration diagram illustrating an example of an image forming apparatus according to the present invention. FIG. 2 is a schematic side view illustrating a state in which an image reading sensor and a shaft body are positioned with an intermediate transfer belt as a belt body therebetween in the image forming apparatus illustrated in FIG. 1. FIGS. 2A and 2B are diagrams for explaining a support frame body that supports a shaft body and mounts an image reading sensor in the image forming apparatus illustrated in FIG. 1, wherein FIG. 1A is a side view and FIG. FIG. 3 is a perspective view schematically illustrating an example of an intermediate transfer unit. FIG. 9 is a schematic diagram illustrating a positional relationship between an intermediate transfer belt and an image reading sensor in a conventional image forming apparatus from the side. FIG. 6 is a schematic diagram showing a state in which the intermediate transfer belt is bent in FIG. 5. FIG. 7A is a diagram for explaining a support base that supports a driving roller rotation shaft and mounts an image reading sensor in a conventional image forming apparatus, where FIG. 7A is a side view and FIG. 8B is a perspective view.

Explanation of reference numerals

21 Image Reading Sensor 23 Shaft 24 Intermediate Transfer Unit 26 Support Frame 41-44 Image Forming Unit 45 Intermediate Transfer Belt 46 Drive Roller 47 Tension Roller 48 Follower Roller 49 Secondary Transfer Roller

Claims (5)

One of a photoreceptor belt, an intermediate transfer belt, or a transfer belt for transferring a toner image to a recording medium, the driving roller driving the belt, and a driven roller And a tension roller that applies tension to the belt body at a position farther from the drive roller than the driven roller, wherein a distance between the drive roller and the driven roller is greater than a distance between the driven roller and the tension roller. Is also configured to be longer,
Image detecting means disposed between the drive roller and the driven roller so as to face the belt member and detecting a primary transfer image on the belt member;
An image forming apparatus, comprising: the image detection unit and a contact member that faces the image detection unit while holding the image detection unit in a state in which the image detection unit is in contact with the image formation unit. The belt body, the driving roller, the driven roller, and the tension roller are integrated as a belt unit,
The image forming apparatus according to claim 1, wherein the contact member is incorporated in the belt unit. The contact member is a shaft body,
The image forming apparatus according to claim 2, wherein a peripheral surface of the shaft member abuts on the belt member between the driving roller and the driven roller in a rotatable state. A component of the device housing, comprising a support frame on which the image detection means is mounted,
A receiving portion that supports the shaft body at at least two points is defined in the support frame,
The image forming apparatus according to claim 3, wherein the image detection unit is fixed to the support frame at a position facing a line connecting the two points. The belt unit is detachable from the device housing,
The image forming apparatus according to claim 4, wherein the shaft body is supported by the receiving portion when the belt unit is mounted on the apparatus housing.

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