Patent Publication Number: US-9835999-B2

Title: Image forming apparatus including forming unit capable of forming transfer-object image and patch image

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2015-254491 filed Dec. 25, 2015. 
     BACKGROUND 
     Technical Field 
     The present invention relates to an image forming apparatus. 
     SUMMARY 
     According to an aspect of the invention, there is provided an image forming apparatus including a photosensitive member having an image area, a first area, and a second area, the first and second areas being provided at different predetermined positions, respectively, at an axial end of the photosensitive member, the first and second areas not overlapping the image area in an axial direction of the photosensitive member; a detecting unit that detects an image; and a forming unit that forms a transfer-object image in the image area of the photosensitive member, the transfer-object image being transferred to a transfer area of continuous-form paper, the forming unit further forming a first image in the first area of the photosensitive member and a second image in the second area of the photosensitive member, the first image not being transferred to the transfer area of the continuous-form paper, the first image being detected by the detecting unit and being used in an operation of controlling conditions for image formation, the second image not being transferred to the transfer area of the continuous-form paper and not being used in the operation of controlling the conditions for image formation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An exemplary embodiment of the present invention will be described in detail based on the following figures, wherein: 
         FIG. 1  is a schematic diagram illustrating a configuration of an image forming apparatus, seen from the front side, according to the exemplary embodiment; 
         FIG. 2  is a schematic diagram of a toner-image-forming unit according to the exemplary embodiment; 
         FIG. 3  is a development of a photoconductor drum according to the exemplary embodiment; 
         FIG. 4  is a schematic diagram illustrating transfer-object images, patches for color-misregistration detection, and patches for potential control that are formed on continuous-form paper in the exemplary embodiment; 
         FIG. 5  is a development of a photoconductor drum according to a modification of the exemplary embodiment; and 
         FIG. 6  is a development of a photoconductor drum according to another modification of the exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An image forming apparatus according to an exemplary embodiment of the present invention will now be described with reference to the accompanying drawings, wherein an arrow H represents the vertical direction, and an arrow W represents the horizontal direction corresponding to the widthwise direction of the apparatus (hereinafter referred to as “the apparatus-width direction”). 
     Configuration of Image Forming Apparatus  10   
       FIG. 1  is a schematic diagram illustrating a configuration of an image forming apparatus  10 , seen from the front side, according to the exemplary embodiment. As illustrated in  FIG. 1 , the image forming apparatus  10  includes an image forming section  12  that electrophotographically forms an image on continuous-form paper P such as a label sheet, a transporting device  50  that transports the continuous-form paper P, and a controller  70  that controls operations of relevant elements included in the image forming apparatus  10 . 
     Transporting Device  50   
     As illustrated in  FIG. 1 , the transporting device  50  includes a feed roller  51  from which a roll of continuous-form paper P is unwound, a winding roller  53  on which the unwound continuous-form paper P is wound, and a continuous portion (not illustrated). When the transporting device  50  is activated, the feed roller  51  and the winding roller  53  are rotated, whereby the winding roller  53  winds up the continuous-form paper P while the feed roller  51  unwinds the roll of continuous-form paper P. 
     Pairs of transport rollers  52  transport the continuous-form paper P from the feed roller  51  to a second-transfer position NT. A pair of transport rollers  54  transport the continuous-form paper P from the second-transfer position NT to a fixing device  40 . A pair of transport rollers  56  transport the continuous-form paper P from the fixing device  40  to the winding roller  53 . 
     Image Forming Section  12   
     The image forming section  12  includes toner-image-forming units  20  that form respective toner images, a transfer device  30  that transfers the toner images formed by the toner-image-forming units  20  to the continuous-form paper P, and the fixing device  40  that fixes the toner images on the continuous-form paper P by applying heat and pressure thereto. 
     The toner-image-forming units  20  form toner images in different colors. In the present exemplary embodiment, five toner-image-forming units  20  are provided for five colors of yellow (Y), magenta (M), cyan (C), black (K), and a special color (V). The toner-image-forming units  20  are arranged side by side in order of that for the special color (V), that for yellow (Y), that for magenta (M), that for cyan (C), and that for black (K) from the upstream side toward the downstream side in the direction of rotation of a transfer belt  31 , which will be described later. 
     Suffixes (V), (Y), (M), (C), and (K) given to some reference numerals in  FIG. 1  indicate the respective colors for which elements denoted by those reference numerals are provided. The special color (V) is, for example, silver or gold. 
     Toner-Image-Forming Unit  20   
     The toner-image-forming units  20  basically have the same configuration, except the kinds of toner to be used. Specifically, referring to  FIG. 2 , the toner-image-forming units  20  each include a photoconductor drum  21  (an exemplary photosensitive member) that rotates clockwise in  FIG. 2 , a charger  22  that charges the photoconductor drum  21 , an exposure device  23  that exposes the photoconductor drum  21  charged by the charger  22  to light and thus forms an electrostatic latent image on the photoconductor drum  21 , a developing device  24  that develops the electrostatic latent image formed on the photoconductor drum  21  by the exposure device  23  and thus forms a toner image, and a blade  25  as a removal member that removes residual toner particles from the surface of the photoconductor drum  21  having undergone the transfer of the toner image to the transfer device  30 . 
     The charger  22  charges the surface (a photosensitive layer) of the photoconductor drum  21  to have, for example, negative polarity. The negatively charged surface of the photoconductor drum  21  is exposed to exposure light L emitted from the exposure device  23 . The exposed part of the photoconductor drum  21  comes to have positive polarity, whereby an electrostatic latent image is formed on the surface of the photoconductor drum  21 . Toner in the developing device  24  is triboelectrically charged to have negative polarity. The negatively charged toner is attracted to the positively charged electrostatic latent image, whereby the electrostatic latent image is developed. In this manner, a toner image is formed on the surface (the outer peripheral surface) of the photoconductor drum  21 . Thus, in the present exemplary embodiment, a combination of the charger  22 , the exposure device  23 , and the developing device  24  serves as an exemplary forming unit that forms a toner image on the photoconductor drum  21 . The blade  25  is in contact with the surface of the photoconductor drum  21  and thus scrapes residual toner particles off the surface of the photoconductor drum  21 . 
     Transfer Device  30   
     The transfer device  30  transfers, in first transfer, the toner images formed on the respective photoconductor drums  21  to the transfer belt  31  (an intermediate transfer body) such that the toner images are superposed one on top of another, and further transfers, in second transfer, the set of toner images superposed on the transfer belt  31  to the continuous-form paper P at the second-transfer position NT (an exemplary transfer nip). Specifically, as illustrated in  FIG. 1 , the transfer device  30  includes the transfer belt  31 , first-transfer rollers  33 , and a second-transfer roller  34 . 
     Transfer Belt  31   
     Referring to  FIG. 1 , the transfer belt  31  has an endless shape and is positioned by being stretched around plural rollers  32 . In the present exemplary embodiment, the transfer belt  31  has an inverted obtuse-triangular shape in front view with the base thereof extending in the apparatus-width direction. Among the plural rollers  32  illustrated in  FIG. 1 , the roller  32 D serves as a driving roller that is driven by a motor (not illustrated) and thus rotates the transfer belt  31  in a direction indicated by an arrow A. The transfer belt  31  transports the toner images transferred thereto in the first transfer to the second-transfer position NT by rotating in the direction of the arrow A. 
     Among the plural rollers  32  illustrated in  FIG. 1 , the roller  32 T serves as a tension-applying roller that applies tension to the transfer belt  31 . Among the plural rollers  32  illustrated in  FIG. 1 , the roller  32 B serves as a counter roller for the second-transfer roller  34 . The counter roller  32 B is provided at the obtuse vertex, i.e., the lower end, of the transfer belt  31  having the inverted obtuse-triangular shape. The transfer belt  31  is in contact with the photoconductor drums  21  for the respective colors from below at the base, i.e., the upper side, extending in the apparatus-width direction. 
     First-Transfer Rollers  33   
     The first-transfer rollers  33  are rollers that transfer the toner images on the respective photoconductor drums  21  to the transfer belt  31 . As illustrated in  FIG. 1 , the first-transfer rollers  33  are provided on the inner side of the transfer belt  31  and across the transfer belt  31  from the respective photoconductor drums  21 . A first-transfer voltage of the polarity opposite to the polarity of the toner is applied to each of the first-transfer rollers  33  from a power-feeding unit  37  (see  FIG. 2 ). With the application of the first-transfer voltage, the toner images on the respective photoconductor drums  21  are transferred to the transfer belt  31  at respective first-transfer positions T each defined between a corresponding one of the photoconductor drums  21  and a corresponding one of the first-transfer rollers  33 . 
     Second-Transfer Roller  34   
     The second-transfer roller  34  transfers the toner images superposed on the transfer belt  31  to the continuous-form paper P. As illustrated in  FIG. 1 , the second-transfer roller  34  is provided such that the transfer belt  31  is held between the second-transfer roller  34  and the counter roller  32 B. The second-transfer roller  34  and the transfer belt  31  are in contact with each other under a predetermined load. The nip between the second-transfer roller  34  and the transfer belt  31  that are in contact with each other is defined as the second-transfer position NT. The second-transfer position NT is supplied with the continuous-form paper P transported from the feed roller  51 . The second-transfer roller  34  rotates clockwise in  FIG. 1 . 
     Furthermore, a negative voltage is applied to the counter roller  32 B from an application unit (not illustrated). Therefore, a potential difference is produced between the counter roller  32 B and the second-transfer roller  34 . Since the negative voltage is applied to the counter roller  32 B, a second-transfer voltage (a positive voltage) of the polarity opposite to that of the toner is indirectly applied to the second-transfer roller  34 , which serves as a counter electrode for the counter roller  32 B. Thus, a transfer electric field is generated between the counter roller  32 B and the second-transfer roller  34 , and an electrostatic force acts on the toner images on the transfer belt  31 . Consequently, the toner images on the transfer belt  31  are transferred to the continuous-form paper P passing through the second-transfer position NT. 
     Featured Elements 
       FIG. 3  is a development of a representative one of the photoconductor drums  21  and illustrates the outer peripheral surface thereof. In  FIG. 3 , the axial direction of the photoconductor drum  21  is represented by an arrow B. As illustrated in  FIG. 3 , the toner image that is formed on the photoconductor drum  21  includes a transfer-object image  90 , a patch  92  for color-misregistration detection, a patch  94  for potential control, and a band  96  for protection of the blade  25 . The transfer-object image  90  is to be transferred to a transfer area P 1  (see  FIG. 4 ) of the continuous-form paper P. 
     The band  96  has a higher image density (a larger amount of toner per unit area) than the patches  92  and  94  and is formed on the photoconductor drum  21  more often than the patches  92  and  94 . 
     The photoconductor drum  21  has patch areas  82  and  84  in which the patch  92  for color-misregistration detection and the patch  94  for potential control are to be formed, respectively, a band area  86  in which the band  96  for protection of the blade  25  is to be formed, and an image area  80  in which the transfer-object image  90  is to be formed. 
     The patch areas  82  and  84  and the band area  86  are provided at respective predetermined positions at a first axial end (the upper end in  FIG. 3 ) of the photoconductor drum  21  and do not overlap the image area  80  in the axial direction of the photoconductor drum  21 . 
     Specifically, the patch areas  82  and  84  and the band area  86  are at different positions in the peripheral direction of the photoconductor drum  21  but are at the same position in the axial direction of the photoconductor drum  21 . The image area  80  is provided on a side nearer to a second axial end of the photoconductor drum  21  with respect to the patch areas  82  and  84  and the band area  86 . 
     In the present exemplary embodiment, as illustrated in  FIG. 3 , a reference position HP is defined in the peripheral direction of the photoconductor drum  21 . The patch areas  82  and  84  and the band area  86  are defined on the basis of, for example, the distance (or angle) from a reference position HP in the peripheral direction of the photoconductor drum  21 . The reference position HP may be detected by, for example, a sensor. Alternatively, the angle of rotation of the photoconductor drum  21  may be detected by using a sensor, such as a rotary encoder, or on the basis of information, such as a driving pulse, so that the positions of the patch areas  82  and  84  and the band area  86  are recognized. 
     In the present embodiment, as illustrated in  FIG. 1 , a detection sensor  72  (an exemplary detecting unit) that detects the patch  92  for color-misregistration detection is provided at a position on the downstream side with respect to the toner-image-forming unit  20 (K) and on the upstream side with respect to the second-transfer position NT in the direction of rotation of the transfer belt  31 . 
     The detection sensor  72  detects the patches  92  included in the respective toner images on the transfer belt  31 , whereby any misregistration of the toner images in the respective colors on the transfer belt  31  is detected. On the basis of the result of the detection, the controller  70  controls the positions of images to be formed on the respective photoconductor drums  21 , as exemplary conditions for image formation. 
     Referring now to  FIG. 2 , a detection sensor  74  (another exemplary detecting unit) that detects the patch  94  for potential control is provided to each of the photoconductor drums  21  at a position on the downstream side with respect to the developing device  24  and on the upstream side with respect to the first-transfer position T in the direction of rotation of the photoconductor drum  21 . 
     The detection sensor  74  detects the density of the patch  94 . Then, the controller  70  controls the levels of charging potential, exposure potential, and development potential (exemplary conditions for image formation) such that the detected density is adjusted to a predetermined target density. 
     Note that the patch  94  for potential control is formed at the first axial end of the photoconductor drum  21 . The levels of charging potential, exposure potential, and development potential are controlled on the premise that the image density at the first axial end of the photoconductor drum  21  is substantially the same as those in an axially central part and at the second axial end of the photoconductor drum  21 . 
     Toner particles forming the band  96  for protection of the blade  25  are fed to a position between the photoconductor drum  21  and the blade  25  with the rotation of the photoconductor drum  21 . Therefore, the friction between the blade  25  and the photoconductor drum  21  is reduced. Thus, the blade  25  is protected. 
     The patches  92  and  94  and the band  96  transferred from the photoconductor drum  21  to the transfer belt  31  are further transferred to a first widthwise end (an end in a direction orthogonal to the longitudinal direction) of the continuous-form paper P. That is, the patches  92  and  94  and the band  96  are transferred to neither a position between adjacent ones of the transfer areas P 1  that are side by side in the longitudinal direction of the continuous-form paper P nor a position in any of the transfer areas P 1 . 
     Thus, the patches  92  and  94  serve as exemplary first images that are not transferred to the transfer area P 1  but are detected by the respective detection sensors  72  and  74  (exemplary detecting units) so as to be used in an operation of controlling the conditions for image formation. 
     The band  96  is not transferred to the transfer area P 1  but serves as an exemplary second image, which is not used in the operation of controlling the conditions for image formation. The phrase “not used in the operation of controlling the conditions for image formation” does not imply that the result of detection of the second image is not used in any operation of controlling (adjusting) the conditions for image formation, but implies that the density of the second image is not detected by the detection sensors  72  and  74  (exemplary detecting units) or that the density of the second image is detected by the detection sensors  72  and  74  but is not used in the operation of controlling the conditions for image formation. 
     Functions of Exemplary Embodiment 
     Functions of the present exemplary embodiment will now be described in comparison with functions of a comparative example. 
     As a comparative example, suppose that the patch  94  for potential control and the band  96  for protection of the blade  25  are formed in the same arbitrary area at the first axial end of the photoconductor drum  21 . More specifically, the patch  94  and the band  96  provided at the first axial end of the photoconductor drum  21  are at the same position in the axial direction and in the peripheral direction of the photoconductor drum  21  and are formed alternately with every revolution of the photoconductor drum  21 . That is, for example, after the band  96  having been formed at a specific position is erased, the patch  94  is formed at that position. 
     In such a case where the patch  94  and the band  96  are alternately formed in the same area at the first axial end of the photoconductor drum  21 , adhesion of toner particles to that area and removal of toner particles with the blade  25  from that area are performed repeatedly. Such a situation may lead to a reduction in the sensitivity of the photoconductor drum  21  or an increase in the potential of the photoconductor drum  21  in that area. 
     Consequently, the result of detection of the patch  94  by the detection sensor  74  may deviate from the characteristics, such as sensitivity and potential, in the axially central part of the photoconductor drum  21 . In such an event, even if conditions such as the levels of charging potential, exposure potential, and development potential are controlled by the controller  70  on the basis of the result of detection of the patch  94  by the detection sensor  74 , the conditions are not controlled appropriately. 
     In contrast, according to the present exemplary embodiment, the patch area  84  and the band area  86  provided at the first axial end (the upper end) of the photoconductor drum  21  are at different positions in the peripheral direction of the photoconductor drum  21 . 
     Furthermore, according to the present exemplary embodiment, the patch area  84  and the band area  86  are provided at different positions in the peripheral direction of the photoconductor drum  21 . Therefore, even if the patch area  84  and the band area  86  are provided at the same position in the axial direction of the photoconductor drum  21  as in the present exemplary embodiment, there is no chance that the patch  94  and the band  96  may be formed in the same area. According to the exemplary embodiment, since the patch area  84  and the band area  86  are provided at the same position in the axial direction of the photoconductor drum  21 , the patch area  84  and the band area  86  are allowed to be provided within an area having a short length in the axial direction of the photoconductor drum  21  at the first end of the photoconductor drum  21 . 
     Modifications 
     While the above exemplary embodiment concerns a case where the patch areas  82  and  84  and the band area  86  are provided at the first axial end (the upper end in  FIG. 3 ) of the photoconductor drum  21  and at different positions in the peripheral direction of the photoconductor drum  21 , the present invention is not limited to such a case. 
     Referring to  FIG. 5 , the patch areas  82  and  84  and the band area  86  provided at the first axial end (the upper end in  FIG. 5 ) of the photoconductor drum  21  may be at different positions in the axial direction of the photoconductor drum  21 . In a modification illustrated in  FIG. 5 , the patch area  82  also serves as the patch area  84 , and vice versa. That is, in the modification illustrated in  FIG. 5 , after the patch  92  having been formed at a specific position is erased, the patch  94  may be formed at that position. 
     In such a modification, the area over which the patch areas  82  and  84  are expected to extend in the axial direction of the photoconductor drum  21  only needs to be detected by the detection sensors  72  and  74 . Hence, in the above modification, the patch  94  and the band  96  are allowed to be shifted in the peripheral direction of the photoconductor drum  21  within a predetermined area. 
       FIG. 6  illustrates another modification in which the patch areas  82  and  84  and the band area  86  are provided at different positions in the axial direction of the photoconductor drum  21 . In the modification illustrated in  FIG. 6 , the patch areas  82  and  84  are provided at the first axial end (the upper end in  FIG. 6 ) of the photoconductor drum  21 , whereas the band area  86  is provided at the second axial end of the photoconductor drum  21 . In addition, the patch area  82  also serves as the patch area  84 , and vice versa. 
     Furthermore, while the above exemplary embodiment concerns a case where the patch  92  for color-misregistration detection and the patch  94  for potential control are employed as the first images, the present invention is not limited to such a case. For example, the first image may be a gradation patch for adjustment of the gradation of each of the colors. 
     Furthermore, while the above exemplary embodiment concerns a case where the band  96  for protection of the blade  25  is employed as the second image, the present invention is not limited to such a case. For example, the second image may be a band for consumption of deteriorated developer (toner particles). 
     Furthermore, while the above exemplary embodiment concerns a case where the patches  92  and  94  and the band  96  are transferred to the continuous-form paper P, the present invention is not limited to such a case. For example, the first image and the second image may be retained on the transfer belt  31  and be removed by a cleaning device or the like, instead of being transferred from the transfer belt  31  to the continuous-form paper P. 
     The foregoing description of the exemplary embodiment of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiment was chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.