Patent Publication Number: US-9423725-B2

Title: Image forming apparatus

Description:
INCORPORATION BY REFERENCE 
     This application is based on and claims the benefit of priority from Japanese Patent Application No. 2014-175551 filed on Aug. 29, 2014 and No. 2014-175552 filed on Aug. 29, 2014, the contents of which are hereby incorporated by reference. 
     BACKGROUND 
     The present disclosure relates to an electrophotographic image forming apparatus being capable of forming a single color monochrome image and a color image having a plurality of colors. 
     An image forming apparatus, such as a color printer, includes, for example, a plurality of photosensitive drums on which toner images of respective colors of black, yellow, magenta, and cyan are formed, and an intermediate transfer belt to which the toner images that have been formed on these plurality of photosensitive drums are transferred. With the plurality of photosensitive drums, a series of electrophotographic processes of electrification, exposure, development, and transfer are performed. The toner images of the respective colors that have been formed on the respective photosensitive drums are primary-transferred to the intermediate transfer belt, and then collectively secondary-transferred to a paper from the intermediate transfer belt. Thereby, a color image is formed on the paper. 
     The respective photosensitive drums are provided with a static eliminator (an eraser), which eliminates static electricity from the surface of the respective photosensitive drums by light irradiation. The static electricity elimination is performed after the transfer as a pre-treatment for electrification at the next time. Such static electricity elimination must be suppressed to a necessary minimum, because it involves light irradiation on the surface of the photosensitive drum, resulting in an optical fatigue thereof. Then, upon a monochrome image of a single color being formed, the static eliminators for the photosensitive drums of respective colors of yellow, magenta, and cyan that are used for forming a color image are controlled so as not to be lighted. 
     SUMMARY 
     The image forming apparatus of the present disclosure is an image forming apparatus including a monochrome image forming part that forms a toner image for a monochrome image on a monochrome photosensitive drum; color image forming parts that form toner images for color images on color photosensitive drums; and an intermediate transfer belt that once carries the toner image to be transferred to a recording paper, the image forming apparatus, at the time of monochrome printing, transferring only the toner image that has been formed on the monochrome photosensitive drum, to the intermediate transfer belt, and at the time of color printing, sequentially transferring the toner image that has been formed on the monochrome photosensitive drum, and the toner images that have been formed on the color photosensitive drums, to the intermediate transfer belt,
         the image forming apparatus having;   a main body control part that controls image formation with the monochrome image forming part and the color image forming parts,   a nip separation mechanism that separates the intermediate transfer belt from the color photosensitive drums,   a separation control part that drives the nip separation mechanism on the basis of a separation control signal that is inputted from the main body control part,   a monochrome static eliminator that is comprised of a monochrome light guide body that extends in a rod shape along the monochrome photosensitive drum, and a monochrome light source that irradiates light on an end face of the monochrome light guide body,   color static eliminators that are comprised of color light guide bodies that extend in a rod shape along the color photosensitive drums, and color light sources that irradiate light on end faces of the color light guide bodies, and   an irradiation location shifting mechanism that shifts the irradiation locations of the light that is emitted from the color light sources, from the end faces of the color light guide bodies, in a state of the intermediate transfer belt being separated from the color photosensitive drums.       

     Further, the image forming apparatus of the present disclosure is an image forming apparatus including a monochrome image forming part that forms a toner image for a monochrome image on a monochrome photosensitive drum; color image forming parts that form toner images for color images on color photosensitive drums; and an intermediate transfer belt that once carries the toner image to be transferred to a recording paper, the image forming apparatus, at the time of monochrome printing, transferring only the toner image that has been formed on the monochrome photosensitive drum, to the intermediate transfer belt, and at the time of color printing, sequentially transferring the toner image that has been formed on the monochrome photosensitive drum, and the toner images that have been formed on the color photosensitive drums, to the intermediate transfer belt,
         the image forming apparatus having:   a main body control part that controls image formation with the monochrome image forming part and the color image forming parts,   a nip separation mechanism that separates the intermediate transfer belt from the color photosensitive drums,   a separation control part that drives the nip separation mechanism on the basis of a separation control signal that is inputted from the main body control part,   a monochrome static eliminator that eliminates static electricity from the monochrome photosensitive drum,   a color static eliminator that eliminates static electricity from the color photosensitive drums,   a switch that is turned ON in a state of the intermediate transfer belt being abutted against the color photosensitive drums, and that is turned OFF in a state of the intermediate transfer belt being separated from the color photosensitive drums,   a monochrome lighting power supply part that makes power distribution to the monochrome static eliminator to light it up on the basis of a lighting control signal that is inputted from the main body control part, and   color lighting power supply parts that make power distribution to the color static eliminators to light them up on the basis of the lighting control signal that is inputted from the main body control part through the switch.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an appearance perspective view illustrating a configuration of a first embodiment of an image forming apparatus in accordance with the present disclosure; 
         FIG. 2  is a sectional schematic view illustrating an internal configuration of the first embodiment of the image forming apparatus in accordance with the present disclosure; 
         FIG. 3  is a sectional schematic view illustrating an internal configuration of the first embodiment of the image forming apparatus in accordance with the present disclosure; 
         FIG. 4A  is a perspective view illustrating an example of configuration of an irradiation location shifting mechanism that shifts the irradiation locations of light sources of static eliminators shown in  FIG. 1 ; 
         FIG. 4B  is a side view illustrating an example of configuration of the irradiation location shifting mechanism that shifts the irradiation locations of the light sources of the static eliminators shown in  FIG. 1 ; 
         FIG. 5A  is a perspective view illustrating another example of configuration of the irradiation location shifting mechanism that shifts the irradiation locations of the light sources of the static eliminators shown in  FIG. 1 ; 
         FIG. 5B  is a side view illustrating another example of configuration of the irradiation location shifting mechanism that shifts the irradiation locations of the light sources of the static eliminators shown in  FIG. 1 ; 
         FIG. 6  is a sectional schematic view illustrating an internal configuration of a second embodiment of the image forming apparatus in accordance with the present disclosure; and 
         FIG. 7  is a sectional schematic view illustrating an internal configuration of the second embodiment of the image forming apparatus in accordance with the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Next, a first embodiment of the present disclosure will be specifically explained with reference to the drawings. 
     An image forming apparatus of the present embodiment is a color printer  1 , and with reference to  FIG. 1 , there are disposed an image forming part  10   a , which accommodates image data of K (black); an image forming part  10   b , which accommodates image data of C (cyan); an image forming part  10   c , which accommodates image data of M (magenta); and an image forming part  10   d , which accommodates image data of Y (yellow). Being adjacent to the top of the four image forming parts  10   a ,  10   b ,  10   c , and  10   d , an intermediate transfer belt  20  is provided. The intermediate transfer belt  20  is stretched over a driving roller  21 , a driven roller  22 , support rollers  23  and  24 , and a tension roller  25 . 
     In the four image forming parts  10   a ,  10   b ,  10   c , and  10   d , there are disposed photosensitive drums  11   a ,  11   b ,  11   c , and  11   d , respectively, which are for carrying visible images (toner images) of respective colors. Around the photosensitive drums  11   a ,  11   b ,  11   c , and  11   d , there are provided electrification apparatuses  12   a ,  12   b ,  12   c , and  12   d , which electrify the photosensitive drums  11   a ,  11   b ,  11   c , and  11   d , respectively; an exposure unit  13 , which exposes image information on the photosensitive drums  11   a ,  11   b ,  11   c , and  11   d , respectively; development apparatuses  14   a ,  14   b ,  14   c , and  14   d , which form toner images on the photosensitive drums  11   a ,  11   b ,  11   c , and  11   d , respectively; primary transfer rollers  15   a ,  15   b ,  15   c , and  15   d , which transfer the toner images on the photosensitive drums  11   a ,  11   b ,  11   c , and  11   d  to the intermediate transfer belt  20 , respectively; cleaning apparatuses  16   a ,  16   b ,  16   c , and  16   d , which remove the toner remaining on the photosensitive drums  11   a ,  11   b ,  11   c , and  11   d , respectively; and static eliminators (erasers)  17   a ,  17   b ,  17   c , and  17   d , which irradiate light on the photosensitive drums  11   a ,  11   b ,  11   c , and  11   d  to eliminate static electricity, respectively. 
     The toner images that have been formed on the photosensitive drums  11   a ,  11   b ,  11   c , and  11   d  are sequentially transferred to the intermediate transfer belt  20 , which is moved, while being abutted against the photosensitive drums  11   a ,  11   b ,  11   c , and  11   d . The toner images, which have been sequentially transferred to the intermediate transfer belt  20 , are transferred to a recording paper P with a secondary transfer roller  18  at a time. The recording paper P is stored in a paper cassette  30 , which is disposed in the bottom section, and is carried to the secondary transfer roller  18  in a recording paper carrying passage  33  through a feed roller  31  and registration rollers  32 . The toner image that has been transferred to the recording paper P is fixed on the recording paper P with a fixing apparatus  19 , and the recording paper P that has been provided with a print is discharged onto a top cover  40  by discharge rollers  34  through the recording paper carrying passage  33 . 
     As shown in  FIG. 2  and  FIG. 3 , the color printer  1  includes a frame  50 , an eccentric cam  51 , and a cam driving motor  52 . The frame  50 , the eccentric cam  51 , and the cam driving motor  52  constitute a nip separation mechanism, which moves the primary transfer rollers  15   b ,  15   c , and  15   d  in an up-down direction in the figure, separating the intermediate transfer belt  20  from the color photosensitive drums  11   b ,  11   c , and  11   d.    
     The frame  50  is a frame member that is formed substantially in a U shape in a plan view. The frame  50  rotatably supports the primary transfer rollers  15   b ,  15   c , and  15   d , and the support rollers  23  and  24  at both end parts in a width direction. The frame  50  is turnably supported around a turning axis  23   a  of the support roller  23 . The support roller  23  is disposed between the primary transfer roller  15   a  of K (black) and the primary transfer roller  15   b  of C (cyan). Further, from the support roller  23  toward the upstream side of the moving direction of the intermediate transfer belt  20 , the primary transfer roller  15   b  of C (cyan), the primary transfer roller  15   c  of M (magenta), the primary transfer roller  15   d  of Y (yellow), and the support roller  24  are disposed in this order. Therefore, by turning the frame  50  around the support roller  23 , the frame  50  can be moved to an abutting position shown in  FIG. 2 , and to a separation position shown in  FIG. 3 , respectively. In the abutting position shown in  FIG. 2 , the primary transfer roller  15   b  of C (cyan), the primary transfer roller  15   c  of M (magenta), and the primary transfer roller  15   d  of Y (yellow) are abutted against the photosensitive drums  11   b ,  11   c , and  11   d  through the intermediate transfer belt  20 , respectively, to form a primary transfer nip. In the separation position shown in  FIG. 3 , the primary transfer roller  15   b  of C (cyan), the primary transfer roller  15   c  of M (magenta), and the primary transfer roller  15   d  of Y (yellow) are separated from the photosensitive drums  11   b ,  11   c , and  11   d , respectively, the intermediate transfer belt  20  being separated from the photosensitive drums  11   b ,  11   c , and  11   d.    
     In addition, the frame  50  is urged in a counterclockwise direction around the turning axis  23   a  of the support roller  23  by an urging member  53 , such as a spring, with an eccentric cam  51  being abutted against the upper end part of the frame  50 . Thereby, the eccentric cam  51  functions as a member to move the frame  50  to the abutting position or the separation position, respectively, and fix it in the abutting position or the separation position. The eccentric cam  51  is turned clockwise or counterclockwise by a turning force transmitted from the cam driving motor  52 . The cam driving motor  52  is an apparatus to transmit a turning force to the eccentric cam  51 , the rotation drive thereof being controlled by the separation control part  54 . The separation control part  54  is a motor driver, controlling the rotation drive of the cam driving motor  52  on the basis of a separation control signal from a main body control part  2 . 
     The main body control part  2  is an information processing part of a microcomputer, or the like, including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. In the ROM, a control program for performing operation control of the image forming apparatus is stored. The CPU reads out the control program stored in the ROM, and expands the control program in the RAM. Thereby, the respective components (the image forming parts  10   a ,  10   b ,  10   c , and  10   d , the exposure unit  13 , the fixing apparatus  19 , the intermediate transfer belt  20 , and the like) are controlled to realize a series of image formation operations. 
     In the case where full-color printing in four colors is to be performed with the color printer  1 , the main body control part  2  outputs a separation control signal (for example, a Hi level signal) to instruct the abutting position to be taken. When a separation control signal to instruct the abutting position to be taken is inputted, the separation control part  54  causes a turning force to be transmitted from the cam driving motor  52  to the eccentric cam  51 . Thereby, the eccentric cam  51  is turned such that it takes a first position where the longer-diameter direction of the eccentric cam  51  is substantially orthogonal to the intermediate transfer belt  20 . With the eccentric cam  51  being turned to the first position, the frame  50 , which is pressed by the eccentric cam  51 , is turned clockwise around the turning axis  23   a  of the support roller  23  against the urging force of the urging member  53 . 
     Thereby, as shown in  FIG. 2 , the intermediate transfer belt  20  is abutted against the photosensitive drums  11   b ,  11   c , and  11   d . The primary transfer roller  15   a  of K (black) causes the intermediate transfer belt  20  to be always abutted against the photosensitive drum  11   a . Therefore, when the intermediate transfer belt  20  is moved to the abutting position, where it is abutted against the photosensitive drums  11   b ,  11   c , and  11   d , the intermediate transfer belt  20  is abutted against all of the photosensitive drums  11   a ,  11   b ,  11   c , and  11   d . Therefore, by moving the intermediate transfer belt  20  to the abutting position, it is made possible to perform full-color printing in four colors with the color printer  1 . 
     On the other hand, in the case where monochrome printing is to be performed with the color printer  1 , the main body control part  2  outputs a separation control signal (for example, a Low level signal) to instruct the separation position to be taken. When a separation control signal to instruct the separation position to be taken is inputted, the separation control part  54  causes a turning force to be transmitted from the cam driving motor  52  to the eccentric cam  51 . Thereby, the eccentric cam  51  is turned such that it takes a second position where the shorter-diameter direction of the eccentric cam  51  is substantially orthogonal to the intermediate transfer belt  20 . With the eccentric cam  51  being turned to the second position, the frame  50  is turned counterclockwise around the turning axis  23   a  of the support roller  23  by the urging force of the urging member  53 . 
     Thereby, as shown in  FIG. 3 , the intermediate transfer belt  20  is separated from the plurality of photosensitive drums  11   b ,  11   c , and  11   d . Therefore, when the intermediate transfer belt  20  is moved to the separation position, where it is separated from the photosensitive drums  11   b ,  11   c , and  11   d , the intermediate transfer belt  20  is abutted against only the photosensitive drum  11   a . Therefore, by moving the intermediate transfer belt  20  to the separation position, it is made possible to perform monochrome printing with the color printer  1 . 
     As shown in  FIG. 4A , the static eliminators  17   a ,  17   b ,  17   c , and  17   d  include light guide bodies  171   a ,  171   b ,  171   c , and  171   d  extending in a rod shape along the photosensitive drums  11   a ,  11   b ,  11   c , and  11   d , and LEDs  172   a ,  172   b ,  172   c , and  172   d , which are light sources that irradiate light on end faces of the light guide bodies  171   a ,  171   b ,  171   c , and  171   d , respectively. The light guide bodies  171   a ,  171   b ,  171   c , and  171   d  guide light that has been made incident from the end faces, irradiating the light on the photosensitive drums  11   a ,  11   b ,  11   c , and  11   d , respectively. 
     As shown in  FIG. 2  and  FIG. 3 , the LEDs  172   a ,  172   b ,  172   c , and  172   d  for the static eliminators  17   a ,  17   b ,  17   c , and  17   d  are lighted up by power distribution from the lighting power supply parts  60   a ,  60   b ,  60   c , and  60   d . Further, the lighting power supply parts  60   a ,  60   b ,  60   c , and  60   d  control power distribution to the static eliminators  17   a ,  17   b ,  17   c , and  17   d  on the basis of a common lighting control signal from the main body control part  2 . 
     The LED  172   a  for the static eliminator  17   a , which eliminates static electricity from the photosensitive drum  11   a , which is for carrying a toner image for a monochrome image, is supported by a supporting member (not shown) that is fixed to the housing, or the like. Therefore, the irradiation location of the light that is emitted from the LED  172   a  is always the end face of the light guide body  171   a.    
     As shown in  FIG. 4A , the LEDs  172   b ,  172   c , and  172   d  for the static eliminators  17   b ,  17   c , and  17   d , which eliminate static electricity from the photosensitive drums  11   b ,  11   c , and  11   d , respectively, which are for carrying toner images for color images, are fixed to one end of the support bars  71   b ,  71   c , and  71   d , respectively, which are turnably supported by the turning shaft  72 . Further, there is provided a configuration in which the other ends of the support bars  71   b ,  71   c , and  71   d  are connected to a plunger  70   a  of a solenoid  70 , and in accordance with advance/retract of the plunger  70   a , the support bars  71   b ,  71   c , and  71   d  are turned. 
     As shown in  FIG. 2  and  FIG. 3 , the solenoid  70  is controlled to be advanced/retracted by a separation control signal. The solenoid  70  moves the plunger  70   a  to a contracted position with a separation control signal (for example, a Hi level signal) to instruct the abutting position to be taken, and moves the plunger  70   a  to an extended position with a separation control signal (for example, a Low level signal) to instruct the separation position to be taken, respectively. 
     In a state in which the plunger  70   a  is moved to the contracted position, as shown in  FIG. 4A , the irradiation locations of the light emitted from the LEDs  172   b ,  172   c , and  172   d  are the end faces of the light guide bodies  171   b ,  171   c , and  171   d , respectively. Therefore, in the case where full-color printing in four colors is to be performed with the color printer  1 , the light emitted from the static eliminator  17   a  is irradiated on the photosensitive drum  11   a , which is for carrying a toner image for a monochrome image, for making static electricity elimination therefor. In addition, the light that is emitted from the static eliminators  17   b ,  17   c , and  17   d , respectively, is irradiated on the photosensitive drums  11   b ,  11   c , and  11   d , which are for carrying toner images for color images, for making static electricity elimination therefor. 
     In a state in which the plunger  70   a  is moved in the extended position, as shown in  FIG. 4B , with the support bars  71   b ,  71   c , and  71   d  being turned, the direction of light that is emitted from the LEDs  172   b ,  172   c , and  172   d , respectively, is changed. Therefore, the respective irradiation locations of the light that is emitted from the LEDs  172   b ,  172   c , and  172   d , are shifted from the end faces of the light guide bodies  171   b ,  171   c , and  171   d . Therefore, in the case where monochrome printing is to be performed with the color printer  1 , the light that is emitted from the static eliminator  17   a  is irradiated on the photosensitive drum  11   a , which is for carrying a toner image for a monochrome image, for making static electricity elimination therefor. However, the light that is irradiated from the static eliminators  17   b ,  17   c , and  17   d , respectively, is not irradiated on the photosensitive drums  11   b ,  11   c , and  11   d , which are for carrying toner images for color images, thereby the static electricity elimination being not made therefor. 
     In the present embodiment, there is provided a configuration in which the solenoid  70 , which is controlled to be advanced/retracted by a separation control signal, is used to change the direction of light that is emitted from the LEDs  172   b ,  172   c , and  172   d , respectively. However, as shown in  FIG. 5A  and  FIG. 5B , the LEDs  172   b ,  172   c , and  172   d  may be supported with a common support member  73 , and the LEDs  172   b ,  172   c , and  172   d , which are supported by the support member  73 , may be moved to directions intersecting with the axes of the light guide bodies  171   b ,  171   c , and  171   d , using the solenoid  70 , respectively. Thereby, the respective irradiation location of the light that is emitted from the LEDs  172   b ,  172   c , and  172   d  can be shifted from the end faces of the light guide bodies  171   b ,  171   c , and  171   d . In this case, it is required that the plunger  70   a  be advanced/retracted at a large stroke, as compared to the case where the direction of light is changed, however, the number of component parts, such as the support bars  71   b ,  71   c , and  71   d , can be reduced. 
     In addition, the support member  73  may be shifted interlockingly with the operation of the nip separation mechanism (movement of the frame  50  or turning of the eccentric cam  51 ), which moves the primary transfer rollers  15   b ,  15   c , and  15   d . In this case, the solenoid  70  can be obviated. 
     Further, there may be provided a light shielding plate which is advanced between the LEDs  172   b ,  172   c , and  172   d  and the end faces of the light guide bodies  171   b ,  171   c , and  171   d , the light shielding plate being advanced/retracted with the operation of the solenoid  70  or the nip separation mechanism. Thereby, the respective irradiation locations of the light that is emitted from the LEDs  172   b ,  172   c , and  172   d  can be changed. In this case, by advancing the light shielding plate between the LEDs  172   b ,  172   c , and  172   d  and the end faces of the light guide bodies  171   b ,  171   c , and  171   d , the respective irradiation locations of the light that is emitted from the LEDs  172   b ,  172   c , and  172   d  are changed into locations on the light shielding plate. 
     As described above, according to the present embodiment, there is provided a color printer  1  (an image forming apparatus) including an image forming part  10   a  (a monochrome image forming part) that forms a toner image for a monochrome image on a photosensitive drum  11   a  (a monochrome photosensitive drum); image forming parts  10   b ,  10   c , and  10   d  (color image forming parts) that form toner images for color images on photosensitive drums  11   b ,  11   c , and  11   d  (color photosensitive drums), respectively; and an intermediate transfer belt  20  that once carries the toner image to be transferred to a recording paper, the color printer  1 , at the time of monochrome printing, transferring only the toner image that has been formed on the photosensitive drum  11   a , to the intermediate transfer belt  20 , and at the time of color printing, sequentially transferring the toner image that has been formed on the photosensitive drum  11   a , and the toner images that have been formed on the photosensitive drums  11   b ,  11   c , and  11   d , respectively, to the intermediate transfer belt  20 ,
         the color printer  1  having:   a main body control part  2  that controls image formation with image forming parts  10   a ,  10   b ,  10   c , and  10   d,      a nip separation mechanism (a frame  50 , an eccentric cam  51 , and a cam driving motor  52 ) that separates the intermediate transfer belt  20  from the photosensitive drums  11   b ,  11   c , and  11   d,      a separation control part  54  that drives the nip separation mechanism on the basis of a separation control signal that is inputted from the main body control part  2 ,   a static eliminator  17   a  that is comprised of a light guide body  171   a  that extends in a rod shape along the photosensitive drum  11   a , and an LED  172   a  (a monochrome light source) that irradiates light on an end face of the light guide body  171   a,      static eliminators  17   b ,  17   c , and  17   d  that are comprised of light guide bodies  171   b ,  171   c , and  171   d  that extend in a rod shape along the photosensitive drums  11   b ,  11   c , and  11   d , and LEDs  172   b ,  172   c , and  172   d  (color light sources) that irradiate light on end faces of the light guide bodies  171   b ,  171   c , and  171   d , and   an irradiation location shifting means (a solenoid  70 , support bars  71   b ,  71   c , and  71   d , and a turning shaft  72 ) that shifts the irradiation locations of the light that is emitted from the LEDs  172   b ,  172   c , and  172   d , from the end faces of the light guide bodies  171   b ,  171   c , and  171   d , in a state of the intermediate transfer belt  20  being separated from the photosensitive drums  11   b ,  11   c , and  11   d.          

     With this configuration, at the time of monochrome printing, even if the color static eliminators  17   b ,  17   c , and  17   d  are lighted up, light will not be irradiated on the photosensitive drums  11   b ,  11   c , and  11   d  of yellow, magenta, and cyan. Therefore, lighting control of the static eliminator  17   a , which eliminates static electricity from the photosensitive drum  11   a  of black, and lighting control of the static eliminators  17   b ,  17   c , and  17   d , which eliminate static electricity from the photosensitive drums  11   b ,  11   c , and  11   d  of yellow, magenta, and cyan, can be performed with a commonalized lighting control signal. Therefore, the static eliminators  17   a ,  17   b ,  17   c , and  17   d  can be controlled with a single port of the CPU in the main body control part  2 . 
     Further, according to the present embodiment, the irradiation location shifting means (the solenoid  70 ) shifts the irradiation locations of the light that is emitted from the LEDs  172   b ,  172   c , and  172   d  from the end faces of the light guide bodies  171   b ,  171   c , and  171   d  on the basis of a lighting control signal that is inputted from the main body control part  2 . 
     Further, according to the present embodiment, the irradiation location shifting means shifts the irradiation locations of the light that is emitted from the LEDs  172   b ,  172   c , and  172   d , from the end faces of the light guide bodies  171   b ,  171   c , and  171   d , being interlocked with the operation of the nip separation mechanism. 
     Next, a second embodiment of the present disclosure will be specifically explained with reference to the drawings. 
     With the present embodiment, the light sources of the light that is irradiated on the photosensitive drums  11   a ,  11   b ,  11   c , and  11   d  by the static eliminators  17   a ,  17   b ,  17   c , and  17   d , respectively, are constituted by lamps or LEDs that are lighted up by power distribution from the lighting power supply parts  60   a ,  60   b ,  60   c , and  60   d . The lighting power supply parts  60   a ,  60   b ,  60   c , and  60   d  control the power distribution to the static eliminators  17   a ,  17   b ,  17   c , and  17   d  on the basis of a common lighting control signal from the main body control part  2 . The lighting control signal that is outputted from the main body control part  2  is directly inputted to the lighting power supply part  60   a , and is inputted to the lighting power supply parts  60   b ,  60   c , and  60   d  through the switch  80  shown in  FIGS. 6 and 7 . 
     The switch  80  is controlled to be turned ON/OFF by a separation control signal from the main body control part  2 , being controlled to be turned ON by a separation control signal (for example, a Hi level signal) that instructs an abutting position to be taken, while being controlled to be turned OFF by a separation control signal (for example, a Low level signal) that instructs a separation position to be taken. Therefore, in full-color printing in four colors, the switch  80  is controlled to be turned ON, the lighting control signal from the main body control part  2  is inputted to the lighting power supply parts  60   a ,  60   b ,  60   c , and  60   d , respectively, the main body control part  2  controlling the lighting of the static eliminators  17   a ,  17   b ,  17   c , and  17   d . Contrarily to this, in monochrome printing, the switch  80  is controlled to be turned OFF, and thus the lighting control signal from the main body control part  2  is inputted only to the lighting power supply part  60   a , the main body control part  2  controlling only the lighting of the static eliminator  17   a.    
     In the present embodiment, the switch  80  has been configured such that it is controlled to be turned ON/OFF from a separation control signal from the main body control part  2 . However, the switch  80  may be constituted by a physical switch that is turned ON/OFF with the operation (movement of the frame  50  or turning of the eccentric cam  51 ) of the nip separation mechanism, which moves the primary transfer rollers  15   b ,  15   c , and  15   d . In addition, in the present embodiment, there has been provided a configuration in which the intermediate transfer belt  20  is moved, however, there may be provided a configuration in which the image forming parts  10   b ,  10   c , and  10   d  are moved in a direction to be separated from the intermediate transfer belt  20 . 
     As described above, according to the present embodiment, there is provided a color printer  1  (an image forming apparatus) including an image forming part  10   a  (a monochrome image forming part) that forms a toner image for a monochrome image on a photosensitive drum  11   a  (a monochrome photosensitive drum); image forming parts  10   b ,  10   c , and  10   d  (color image forming parts) that form toner images for color images on photosensitive drums  11   b ,  11   c , and  11   d  (color photosensitive drums), respectively; and an intermediate transfer belt  20  that once carries the toner image to be transferred to a recording paper, the color printer  1 , at the time of monochrome printing, transferring only the toner image that has been formed on the photosensitive drum  11   a , to the intermediate transfer belt  20 , and at the time of color printing, sequentially transferring the toner image that has been formed on the photosensitive drum  11   a , and the toner images that have been formed on the photosensitive drums  11   b ,  11   c , and  11   d , respectively, to the intermediate transfer belt  20 ,
         the color printer  1  having;   a main body control part  2  that controls image formation with image forming parts  10   a ,  10   b ,  10   c , and  10   d,      a nip separation mechanism (a frame  50 , an eccentric cam  51 , and a cam driving motor  52 ) that separates the intermediate transfer belt  20  from the photosensitive drums  11   b ,  11   c , and  11   d,      a separation control part  54  that drives the nip separation mechanism on the basis of a separation control signal that is inputted from the main body control part  2 ,   a static eliminator  17   a  (a monochrome static eliminator) that eliminates static electricity from the photosensitive drum  11   a,      static eliminators  17   b ,  17   c , and  17   d  (color static eliminators) that eliminate static electricity from the photosensitive drums  11   b ,  11   c , and  11   d , respectively,   a switch  80  that is turned ON in a state of the intermediate transfer belt  20  being abutted against the photosensitive drums  11   b ,  11   c , and  11   d , and is turned OFF in a state of the intermediate transfer belt  20  being separated from the photosensitive drums  11   b ,  11   c , and  11   d,      a lighting power supply part  60   a  (a monochrome lighting power supply part) that makes power distribution to the static eliminator  17   a  to light it up on the basis of a lighting control signal that is inputted from the main body control part  2 , and   lighting power supply parts  60   b ,  60   c , and  60   d  (color lighting power supply parts) that make power distribution to the static eliminators  17   b ,  17   c , and  17   d  to light them up, respectively, on the basis of a lighting control signal that is inputted from the main body control part  2  through the switch  80 .       

     With this configuration, lighting control of the static eliminator  17   a , which eliminates static electricity from the photosensitive drum  11   a  of black, and lighting control of the static eliminators  17   b ,  17   c , and  17   d , which eliminate static electricity from the photosensitive drums  11   b ,  11   c , and  11   d  of yellow, magenta, and cyan, can be performed with a commonalized lighting control signal. Therefore, the static eliminators  17   a ,  17   b ,  17   c , and  17   d  can be controlled with a single port of the CPU in the main body control part  2 . 
     Further, according to the present embodiment, the switch  80  is controlled to be turned ON/OFF on the basis of a separation control signal. 
     Further, according to the present embodiment, the switch  80  may be a physical switch that is turned ON/OFF with the operation of the nip separation mechanism. 
     The present disclosure is not limited to the above respective embodiments, and it is obvious that the respective embodiments can be appropriately modified within the scope of the technical concept of the present disclosure. In addition, the number, location, geometry, and the like, of the above components are not limited to those mentioned in the above embodiments, and may be adapted to be a number, location, geometry, and the like, that are appropriate for embodying the present disclosure. In the respective figures, the same component is provided with the same symbol.