Patent Publication Number: US-8111277-B2

Title: Image forming apparatus with a plurality of exposure units

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of co-pending U.S. application Ser. No. 12/340,778, filed Dec. 22, 2008, which claims priority from Japanese Patent Application No. 2007-335638, filed on Dec. 27, 2007, the entire subject matter of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     Aspects of the present invention relate to an image forming apparatus having a plurality of exposure units configured to be opposed to photosensitive members. 
     BACKGROUND 
     In a related-art image forming apparatus, a plurality of LED heads that generate electrostatic latent images on photosensitive drums are held by a pivotable upper cover by way of a holding member. In association with pivoting movement of the upper cover, the LED heads are moved from exposure positions where the LED heads expose the photosensitive drums with light and retracted positions where the LED heads are separated from the photosensitive drums (see; for example, JP-A-2007-65125). In such an image forming apparatus, a control substrate that controls light emission of the LED heads on the basis of data pertaining to an image to be generated is provided in an apparatus main body, and the control substrate of the apparatus main body and the respective LED heads of the upper cover are electrically connected together via respective cables. 
     In the related-art image forming apparatus, a plurality of cables are laid over a long distance from the control substrate of the apparatus main body to the LED heads of the upper cover. Through these cables connecting the control substrate and the LED heads, power for driving the LED heads is supplied to the LED heads as well as a signal, such as an image data. Therefore, the cables supply a larger amount of power as compared with a cable for supplying only a signal. 
     Noise arising in the high-power cable greatly affects adjacent cable or other members. Therefore, the cable is usually shielded with a shield member, such as aluminum. However, such a shield member is expensive. 
     Moreover, since a plurality of cables are laid over a long distance from the control substrate of the apparatus main body to the LED heads of the upper cover, a space for laying (routing) the plurality of cables has to be ensured in the apparatus main body and the upper cover, which raises a problem of complication of wiring. 
     SUMMARY 
     Exemplary embodiments of the present invention address the above disadvantages and other disadvantages not described above. However, the present invention is not required to overcome the disadvantages described above, and thus, an exemplary embodiment of the present invention may not overcome any of the problems described above. 
     Accordingly, it is an aspect of the present invention to provide an image forming apparatus that has a high-power cable shorter than a related-art cable and that is simply wired. 
     According to an exemplary embodiment of the present invention, there is provided an image forming apparatus including: an lower body including a plurality of photosensitive members and having an opening; a upper body which is configured to open and cover the opening; a plurality of exposure units which are supported by the upper body and which are opposed to the photosensitive members when the upper body covers the opening; a main substrate provided in the housing; an exposure control substrate which is provided to the upper body and controls light emission of the plurality of exposure units; a plurality of first cables which electrically connect the exposure units to the exposure control substrate, respectively, each of the first cables including a plurality of signal lines; and a second cable which electrically connects the exposure control substrate to the main substrate and which includes at least one signal line, a number of which is smaller than a total number of the signal lines included in the plurality of first cables. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects of the present invention will become more apparent and more readily appreciated from the following description of exemplary embodiments of the present invention taken in conjunction with the attached drawings, in which: 
         FIG. 1  is a cross-sectional view showing an overall configuration of a color printer; 
         FIG. 2  is a cross-sectional view showing the color printer in which an upper cover is opened; 
         FIG. 3  is a cross-sectional view taken along line III-III shown in  FIG. 1 ; and 
         FIG. 4  is a schematic diagram showing a wiring configuration in a main control substrate and an LED control substrate and an LED head. 
     
    
    
     DETAILED DESCRIPTION 
     An exemplary embodiment of the present invention will now be described in detail with reference to the drawings. In the drawings,  FIG. 1  is a cross-sectional view showing the overall configuration of a color printer, and  FIG. 2  is cross-sectional view showing the color printer in which an upper cover is opened. 
     In the following descriptions, directions will be described by reference to user&#39;s directions when the color printer is in use. Specifically, in  FIG. 1 , the left side of the sheet is taken as “front”; the right side of the sheet is taken as “rear”; a direction away from the viewer in the sheet is taken as “left”; and a direction toward the viewer in the sheet is taken as “right.” The vertical direction of the sheet is taken as the “vertical (upper and lower) direction.” 
     As shown in  FIG. 1 , a color printer  1  has, within a main housing  10 , a sheet feeding section  20  for feeding a sheet P; an image forming section  30  for forming an image on the thus-fed sheet P; a sheet discharging section  90  that discharges the sheet P on which an image is formed; and a main substrate  100  for controlling the respective sections at the time of formation of an image. The main housing  10  has an opening  10 A at an upper portion thereof. 
     As shown in  FIG. 2 , an upper cover  11  that is configured to open and cover the opening  10 A of the main housing  10  is provided at the upper portion of the main housing  10 . The upper cover  11  is vertically pivotable about a rotary shaft  12  provided at a rear side of the main housing  10 . As shown in  FIG. 1 , an upper surface of an upper cover  11  constitutes a sheet discharging tray  13  on which the sheets P discharged from the main housing  10  is stacked. A lower surface of the upper cover  11  is provided with a plurality of holding members  14  which hold (support) LED units  40 . An LED control substrate  110  and a shield plate  120  opposing the LED control substrate  110  are provided inside of the upper cover  11 . 
     The sheet feeding section  20  includes a sheet feeding tray  21  that is provided in a lower inner portion of the main housing  10  and that is removably attached to the main housing  10 ; and a sheet feeding mechanism  22  that conveys the sheets P from the sheet feeding tray  21  to an image forming section  30 . The sheet feeding mechanism  22  is provided on the right side of the sheet feeding tray  21  and includes a feed roller  23 , a separation roller  24 , and a separation pad  25 . 
     In the sheet feeding section  20  configured as mentioned above, the sheets P loaded in the sheet feeding tray  21  are separated one at a time and fed upwardly. After paper powder is removed during the course of the sheet passing between a paper powder removal roller  26  and a pinch roller  27 , the sheet passes through a conveyance path  28 , to thus be turned back and fed to the image forming section  30 . 
     The image forming section  30  includes the four LED units  40 ; four process cartridges  50 ; a transfer unit  70 ; and a fixing unit  80 . 
     The LED units  40  are disposed above the respective photosensitive drums  53 . Each of the LED units  40  includes an LED head  41  and a frame  42 . The LED heads  41  are disposed to be opposed to the respective photosensitive drums  53 . 
     A plurality of light-emitting diodes (LEDs, not shown) are arranged in a right-and-left direction on the surface of the LED head  41  to be opposed to the photosensitive drum  53 . Each of the LEDs receives an input signal from an LED control substrate  110 , which will be described later, on the basis of data pertaining to an image to be formed, to thus illuminate and expose the surface of the photosensitive drum  53 . 
     The frame  42  covers the LED head  41  and attached in a pivotable manner to the upper cover  11  through a holding member  14 . As a result, as shown in  FIG. 2 , the LED unit  40  (the LED head  41 ) is moved from an exposure position where the LED unit opposes the photosensitive drum  53 , to an upper retracted position upwardly pivoting the upper cover  11 . 
     As shown in  FIG. 1 , the process cartridges  50  are aligned in a longitudinal direction while being sandwiched between the upper cover  11  and the sheet feeding section  20 , and each of the process cartridges  50  includes a drum unit  51  and a developing unit  61  removably attached to the drum unit  51 . The process cartridge  50  can be replaced through the opening  10 A of the main housing  10  after the upper cover  11  is pivoted upwardly (see  FIG. 2 ). The process cartridges  50  differ from each other only in terms of the color of toner (a developing agent) housed in a toner housing chamber  66  of a developing unit  61  and are identical with each other in terms of a structure. 
     Each of the drum units  51  includes a drum case  52 ; a photosensitive drum  53  rotatably supported by the drum case  52 ; and an electrifier  54 . 
     As a result of the developing unit  61  being attached to the drum case  52 , an exposure space  55  (see  FIG. 2 ) through which the photosensitive drum  53  is viewed from the outside is defined. The LED unit  40  (the LED head  41 ) is inserted into the exposure space  55  so as to oppose an upper area of the surface of the photosensitive drum  53 . 
     The developing unit  61  has a case  62 ; a developing roller  63  and a supply roller  64  that are rotatably supported by the case  62 ; and a blade assembly  65 . Further, the developing unit  61  has a toner housing chamber  66  that houses toner. 
     As shown in  FIG. 1 , a transfer unit  70  is interposed between the sheet feeding section  20  and the respective process cartridges  50 . The transfer unit  70  includes a drive roller  71 , a driven roller  72 , a conveyance belt  73 , a transfer roller  74 , and a cleaning section  75 . 
     The drive roller  71  and the driven roller  72  are provided in parallel while being spaced apart from each other in the longitudinal direction. The conveyance belt  73  formed from an endless belt is wound around the drive roller  71  and the driven roller  72 . An external surface of the conveyance belt  73  is in contact with the respective photosensitive drums  53 . Four transfer rollers  74  that nip the conveyance belt  73  in conjunction with the respective photosensitive drums  53  are disposed inside of the conveyance belt  73  so as to oppose the respective photosensitive drums  53 . A transfer bias voltage is applied to the transfer rollers  74  by constant current control operation performed during transfer. 
     The cleaning section  75  is disposed below the conveyance belt  73  and configured so as to remove the toner adhering to the conveyance belt  73  and cause the thus-removed toner to fall into a toner reservoir section  76  disposed below the cleaning section  75 . 
     The fixing unit  80  is disposed at the rear of the respective process cartridges  50  and the transfer unit  70  and includes a heating roller  81  and a pressing roller  82  that is disposed opposite the heating roller  81  and presses the heating roller  81 . 
     In the image forming section  30  configured as mentioned above, surfaces of the respective photosensitive drums  53  are uniformly charged by the electrifiers  54  and subsequently exposed to LED light emitted from the respective LED heads  41 . Thereby, the electric potential of exposed areas becomes lower, and electrostatic latent images based on image data are formed on the respective photosensitive drums  53 . 
     The toner in the toner housing chamber  66  is supplied to the developing roller  63  by rotation of the supply roller  64 , and the thus-supplied toner enters a space between the developing roller  63  and the blade assembly  65  by rotation of the developing roller  63 , whereupon the toner is held on the developing roller  63  as a thin layer of specific thickness. 
     The toner held on the developing roller  63  is supplied to the electrostatic latent image formed on the photosensitive drum  53  when the developing roller  63  contacts the photosensitive drum  53  in an opposing manner. Thereby, the toner is selectively held on the photosensitive drum  53 , so that the electrostatic latent image is visualized and that a toner image is generated by this reversal development. 
     In the course of the sheet P fed on the conveyance belt  73  passing between the respective photosensitive drums  53  and the respective transfer rollers  74  disposed inside of the conveyance belt  73 , the toner images formed on the respective photosensitive drums  53  are sequentially transferred to the sheet P. When the sheet P passes between the heating roller  81  and the pressing roller  82 , the toner images transferred onto the sheet P are thermally fixed. 
     The sheet discharging section  90  includes a sheet discharging path  91  that is formed so as to upwardly extend from an exit of the fixing unit  80  and turn to the right side and a plurality of conveyance roller pairs  92  for conveying the sheet P. The sheet P on which the toner images are transferred and thermally fixed is conveyed along the sheet discharging path  91  by the conveyance rollers  92 , discharged to the outside of the main housing  10 , and stacked on the sheet discharging tray  13 . 
     A wiring configuration in the main substrate  100 , the LED control substrate  110  and the LED heads  41  will now be described.  FIG. 3  is a cross-sectional view taken along line III-III shown in  FIG. 1 , and  FIG. 4  is a schematic view showing the wiring configuration in the main substrate, the LED control substrate and the LED heads. 
     The main substrate  100  is configured to control respective sections of the color printer  1  during image forming operation by means of a related-art technique. Specifically, the main substrate  100  directly controls or indirectly controls, through another control substrate (e.g., the LED control substrate  110 ), rotational speeds of the photosensitive drums  53  and the drive roller  71 , the conveyance speed of the sheet P achieved at the sheet feeding section  20  and at the fixing unit  80 , and illumination timings of the respective LEDs. As shown in  FIGS. 1 and 3 , the main substrate  100  is arranged to stand upright along a rear lower portion of the left side surface in the main housing  10 , that is, a substrate surface (a circuit surface) of the substrate is oriented in the right-to-left direction. 
     By a related-art technique, the LED control substrate  110  outputs signals to the respective LEDs of the respective LED heads  41  on the basis of data pertaining to an image to be formed, thereby controlling illumination (light emission) of the LEDs. As shown in  FIG. 2 , the LED control substrate  110  is disposed at the front interior side of the upper cover  11  so that the centroid G of the upper cover  11  is positioned at more front than the center C located at an equidistance L from the front end and the rear end of the upper cover  11 . In other words, the centroid G of the upper cover  11  is positioned between the front end thereof and the center C thereof. As a result, the LED control substrate  110  acts as a weight, so that the upper cover  11  can be closed firmly. The centroid of the LED control substrate  110  is also positioned more front than the center C of the upper cover  11  shown in  FIG. 2 . 
     The shield plate  120  is a plate material made of metal and shields noise, such as electromagnetic waves, arising in the LED control substrate  110 . As shown in  FIG. 1 , the shield plate  120  includes an upper shield plate  121  disposed at the front side of the upper cover  11  and that opposes an upper surface of the LED control substrate  110  and a lower shield plate  122  that opposes a lower surface of the LED control substrate  110 . 
     Emission of noise to outside, such as electromagnetic waves, arising in the LED control substrate  110  can be prevented by providing the shield plate  120 . Further, the shield plate  120  formed from metal serves as a reinforcement member, to thus enable enhancement of the strength of the upper cover  11 . Further, the shield plate  120  is disposed so as to oppose upper and lower surfaces of the LED control substrate  110 . Therefore, the shield plate  120  made of metal acts as a weight in conjunction with the LED control substrate  110 , so that the upper cover  11  can be closed firmly. 
     As shown in  FIG. 3 , the respective LED units  40  (the respective LED heads  41 ) and the LED control substrate  110  are electrically connected with each other via flat cables  130  including a plurality of flat cables  130 A to  130 D. The LED control substrate  110  and the main substrate  100  are electrically connected with each other via a single flat cable  140 . 
     Each of the flat cables  130  ( 130 A to  130 D) is a single cable formed by tying signal lines covered with an insulating resin coating into a bundle having a belt shape. One end of each of the flat cables  130 A to  130 D is connected to the respective one of connectors  111 A to  111 D provided on the LED control substrate  110 . The flat cables are drawn rightwardly from the right end portion of the LED control substrate  110  and bent as necessary. The other end of each of the flat cables  130 A to  130 D is connected to the respective one of connectors  43 A to  43 C provided on the LED unit  40 . The respective connectors  43 A to  43 D are electrically connected to the respective LED heads  41  via the frame  42 . 
     The flat cable  140  is a single cable formed by tying signal lines covered with an insulating resin coating are into a bundle having a belt shape. Although unillustrated, the total number of the signal lines included in the flat cable  140  is smaller than the total number of the signal lines included in the four flat cables  130 . Further, the flat cable  140  is different from the flat cable  130  in terms of a data transfer rate achieved per line and a protocol to be used therein. 
     One end of the flat cable  140  is connected to the connector  112  provided on the LED control substrate  110 , and the other end of the flat cable  140  is connected to the connector  101  provided on the main substrate  100 . More specifically, the flat cable is drawn, in the upper cover  11 , leftwardly from the left end portion of the LED control substrate  110 , which is a side where the main substrate  100  is disposed. And, the drawn flat cable is bent from left to rear and extends further rearwardly. Further, the flat cable  140  is wrapped over the rear of the pivotal shaft  12 , to thus enter the main housing  10 , turn to the front, undergo leftward bent, and be finally connected to the connector  101 . 
     The above wiring configuration will be described more simply. As shown in  FIG. 4 , in the color printer  1 , the main substrate  100  provided in the main housing  10  and the LED control substrate  110  provided in the upper cover  11  are electrically connected to each other via the single flat cable  140 . The four flat cables  130 A to  130 D are drawn from the LED control substrate  110  and electrically connected to the respective LED units  40  (the LED heads  41 ). Specifically, the four flat cables  130 A to  130 D connected to the respective LED heads  41  are brought together at the LED control substrate  110 , and the flat cables are connected to the main substrate  100 , via the single flat cable  140  including the signal lines, the number of which is small. Additionally, power for driving the respective LED units  40  (LED heads  41 ) is supplied with using the four flat cables  130 A to  130 D. 
     In the present exemplary embodiment, power for driving the respective LED units  40  (LED heads  41 ) is supplied from a power substrate  150  disposed separately from the main substrate  100  in the main housing  10  via a cable  151  independent from the flat cable  140 . The cable  151  drawn from the power substrate  150  is connected to a power connector  113  provided on the LED control substrate  110 . The LED control substrate  110  supplies the power from the power connector  113  to the respective LED units  40  (LED heads  41 ) with using the four flat cables  130 A to  130 D. 
     According to the above configuration of this exemplary embodiment, the following effects can be achieved. 
     The main substrate  100  and the LED control substrate  110  are connected to each other via the single flat cable  140 , and the LED control substrate  110  and the respective LED heads  41 , both of which are provided on the upper cover  11 , are connected via the flat cables  130 A to  130 D. Therefore, the LED control substrate  110  can apply power for driving the LED heads  41  to the flat cables  130 A to  130 D. That is, for the flat cable  140 , it is necessary to flow only a signal, such as image data. In other words, the flat cable  40  is not used for supplying power for driving the respective LED units  40  (LED heads  41 ). 
     As a result, comparing with the case where the main substrate  100  and the respective LED units  40  (LED heads  41 ) would be directly connected to each other with using four flat cables  130 A to  130 D, the length of the flat cables  130 A to  130 D which connect the LED control substrate  110  to the LED heads  41 , respectively, becomes shorter. That is, the usage of the flat cables  130 A to  130 D for high power, which needs an expensive shield member, can be reduced in the entire apparatus. Additionally, since the length of the flat cables  130 A to  130 D can be shorter, noise arising in the flat cables  130 A to  130 D cab be diminished. Consequently, a necessity for covering the flat cables  130 A to  13 D with a shield member, such as aluminum, is obviated (or areas to be covered can be reduced), and therefore, wiring can be made cost efficiently. 
     Further, since the total number of signal lines included in the flat cable  140  is smaller than the total number of signal lines included in the four flat cables  130 A to  130 D, the width of the flat cable  140  can be smaller. As a result, comparing with the case where the main substrate  100  and the respective LED heads  41  are directly connected to each other, that is, the case where a large-size cable into which four flat cables are tied into a bundle is used, for example, a space in the upper cover  11  and a space in the main housing  10 , which are used for routing the cable, can be reduced. Consequently, the upper cover  11  and the main housing  10  can be miniaturized, and the color printer  1  can be miniaturized. Moreover, since the flat cable  140  of smaller width can be used, routing of the cable around the pivotal shaft  12  becomes effectively. 
     In particularly, in the present exemplary embodiment, the flat cable  140  is a single cable, and therefore, the cable can be more readily arranged (routed) in the upper cover  11  and the main housing  10  as compared with the case where four flat cables  130 A to  13 D would be used for directly connecting the main substrate  100  to the respective LED heads  41 . Routing of the cable around the pivotal shaft  12  becomes further improved. 
     Since only a signal, such as image data, flows though the flat cable  140 , the amount of noise arising in the cable becomes small. Accordingly, a necessity for sheathing the flat cable  140  with a shield member, such as aluminum, is obviated, and therefore, wiring can be made cost efficiently. 
     Since the flat cables  130  ( 130 A to  130 D) and the flat cable  140  are drawn from the LED control substrate  110  in different directions, influence of noise, such as electromagnetic waves, arising in the flat cables can be diminished. Especially, the influence of noise arising in the high-power flat cable  130  can be prevented affecting the flat cable  140  through which a signal mainly flows. In the present exemplary embodiment, the flat cables are drawn in different directions with respect to the right-and-left direction, miniaturization of the LED control substrate  110  becomes possible. Consequently, the color printer  1  can be miniaturized. 
     The flat cable  140  is drawn from an end portion of the LED control substrate  110  at a side closest to the side at which the main substrate  100  is disposed. Therefore, the cable (the flat cable  140 ) laid between the main substrate  100  and the LED control substrate  110  can be shortened. Moreover, since the flat cable  140  and the main substrate  100  are disposed on the same side, wiring can be made effectively. 
     While the present invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. 
     The present exemplary embodiment provides the case where the upper cover  11  provided so as to be vertically pivotable about the pivotal shaft  12  disposed at the rear side of the main housing  10 . However, the cover is not limited to the upper cover. For example, a the upper cover may be configured to slidably move (parallel movement) upwardly. Moreover, the direction in which the cover is opened and covered is not limited to the vertical direction. For example, a cover may be provided on the left or right side surface of the main housing and is opened and covered in the right-and-left direction. 
     The exemplary embodiment provides the case where the LED heads  41  using LEDs are adopted. However, the present invention is not limited thereto. For example, an exposure unit using Organic Light-Emitting Diode (OLED), fluorescent substances, or the like, may also be adopted in place of the LEDs. Moreover, an exposure unit that includes a plurality of optical shutters (e.g., liquid-crystal elements, PLZT elements, and the like) arranged for controlling light from a single or a plurality of light sources and that selectively controls an opening and closing time of the optical shutters on the basis of image data. 
     The exemplary embodiment provides the case where the flat cables  130  and  140  are adopted. However, the present invention is not limited thereto. For example, the flexible flat cables (FFC), and the like may be used in place of the flat cables  130  and  140 . Although no mentioned is particularly made to the signal lines, each signal line may be configured by a single lead wire or a multi-lead wire. 
     Although the exemplary embodiment provides the case where the flat cables  130  and  140  are drawn in opposite directions along the right-to-left direction, the way to draw the cables is not limited to this. For example, if the flat cable  140  is drawn from the left end portion of the LED control substrate  110 , the flat cable  130  may be drawn from the front end portion or the rear end portion of the LED control substrate  110 . Moreover, the flat cables  130  and  140  may be drawn from an end portion on the same side of the LED control substrate  110 . 
     The exemplary embodiment provides the case where the main substrate  100  is disposed on the left surface of the main housing  10 . However, the location of the main substrate  100  is not limited to the left surface but may also be disposed on, for example, the right surface of the main housing. In this case, the flat cables  130  is desirably drawn from the right end portion of the LED control substrate  110 . Further, the main substrate  100  may also be disposed on the rear of the main housing. 
     The exemplary embodiment provides the case where the main substrate  100  is arranged so that the substrate surface (the circuit surface) of the substrate is oriented in the right-and-left direction in the main housing  10 . However, the present invention is not limited thereto. For example, in the case where the main substrate is arranged on the rear surface of the main housing, the substrate surface (the circuit surface) can also be oriented in the front-to-rear direction. Alternatively, the main substrate may also be laid in the main housing; namely, the substrate surface (the circuit surface) may be vertically oriented. 
     The exemplary embodiment provides the configuration in which the flat cable  140  is wrapped over the rear of the pivotal shaft  12 , to thus enter the lower main housing  10 . However, the present invention is not limited thereto. Specifically, no limitations are imposed on the configuration, so long as the layout (wiring) does not interfere with opening and closing actions of the upper cover  11 . 
     The exemplary embodiment provides the configuration in which power of the LED control substrate  110  is supplied from the power substrate  150  separate from the main substrate  100 . However, the present invention is not limited thereto. Specifically, power is supplied from the main substrate. In other words, the main substrate also functions as a power substrate.