Patent Publication Number: US-6711375-B1

Title: Image forming apparatus and method of setting up the same

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an image forming apparatus and method of setting up the same for reusing recovered toner by mixing it with new toner, the apparatus and the method being applicable to an image forming apparatus and the like of, for example, a copying machine, printer, facsimile, and the like. 
     An image forming apparatus having a toner recycle device executes an image forming process such that the surface of a photosensitive drum is charged negatively, a latent image is formed by exposing the photosensitive drum with laser beams based on an image signal (a surface is charged with a potential), a visible image is formed by causing the latent image to absorb negatively charged toner, and the visible image is transferred onto a positively charged sheet and fixed thereon. 
     In this case, the toner is stored in a developing device as a developing agent mixed with a carrier. The developing device adheres a suitable amount of the developing agent on the surface of the charged photosensitive drum  2 . 
     In the above image formation, toner, which was already used for image formation and collected for recycle (hereinafter, referred to as “recovered toner”), and new toner, which is not yet used for image formation (hereinafter, referred to as “new toner”), are used in mixture. That is, the recovered toner is recycled. The recovered toner is recycled by a toner recycle device. 
     Incidentally, when the image forming apparatus is used for the first time, the developing device must be filled with an initial developing agent. The following way are conventionally available as way for filling the developing device with the initial developing agent. 
     (1) When a product is shipped, the developing device is previously filled with the initial developing agent. 
     (2) When the product is shipped, a new toner hopper is filled with the initial developing agent, and the initial developing agent in the new toner hopper is supplied into the developing device when the product is used for the first time. 
     (3) A vessel (bottle, bag and the like) filled with the initial developing agent is put into the package of an image forming apparatus main body separately therefrom and charged into the developing device when the image forming apparatus is set up. 
     However, the respective way described above have the following problems. 
     (1) When the developing device is previously filled with the initial developing agent, there is a possibility that the developing agent leaks due to vibration and the like while it is transported. Since the developing device has a developing roller which ordinarily includes a large opening, the developing agent is apt to leak from the opening in the structure of the developing device. It is very difficult to prevent the leakage of the developing agent from the opening with a simple structure. While there is an example in which a shutter structure is employed to prevent the leakage, this structure is considerably expensive. 
     There is also a system for entirely sealing the developing roller. This system, however, is time-consuming because the seal member must be removed when the image forming apparatus is set up. 
     (2) When the new toner hopper is filled with the fresh developing agent, all the initial developing agent in the new toner hopper must be supplied into the developing device when the image forming apparatus is set up. New toner cannot be replenished while the initial developing agent remains in the new toner hoper. This is because when the new toner is resupplied while the initial developing agent remains, the ratio of the toner to the carrier changes. 
     In this case, the new toner must be naturally replenished after the completion of an automatic toner adjustment, which is time-consuming. 
     (3) When the vessel is filled with the initial developing agent and put into the package of the image forming apparatus main body, the developing device must be removed from the main body, and the initial developing agent must be charged thereinto, which is considerably time-consuming. Further, since it is difficult for a user to carry out a developing agent charge job, the user cannot set up the image forming apparatus. 
     SUMMARY OF THE INVENTION 
     An object of the present invention, which has been made to overcome the problems of the conventional art described above, is to provide a less expensive image forming apparatus and a set-up method for the image forming apparatus which can reliably prevent the leakage of a developing agent without the need of a special seal structure in packaging and permits a user to easily carry out a set-up job in a short time without trouble. 
     The present invention, which has been made to achieve the above object, relates to an image forming apparatus and a set-up method for the image forming apparatus for reusing recovered toner collected after toner is used in a developing device of the image forming apparatus by mixing the recovered toner with new toner. The developing device is in an evacuated state before the image forming apparatus is initially set up, and a transfer path of the recovered toner is filled with an initial developing agent which is supplied into the developing device when the image forming apparatus is initially set up. It is preferable that a recovered toner sub-hopper of the recovered toner transfer path be filled with the initial developing agent. 
     When the image forming apparatus is initially set up, it is preferable that the initial developing agent be automatically and promptly supplied into the developing device by actuating a toner recycle device independently of the image forming apparatus and increasing the operation speed of the toner recycle device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic front elevational view showing a main portion of an image forming apparatus of an embodiment of the present invention; 
     FIG. 2 is a perspective view showing a new toner replenishment device of the embodiment; 
     FIG. 3 is a perspective view showing the image forming apparatus of the embodiment; 
     FIG. 4 is a perspective view showing the image forming apparatus of the embodiment excluding the new toner replenishment device; 
     FIG. 5 is a perspective view showing a toner recycle device of the embodiment; 
     FIG. 6 is a perspective view showing the toner recycle device of the embodiment from a view point different from that of FIG. 5; 
     FIG. 7 is a block diagram showing a control arrangement of the image forming apparatus of the embodiment; and 
     FIG. 8 is a flowchart showing a processing function when the image forming apparatus of the embodiment is set up. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of an image forming apparatus and a set-up method for the image forming apparatus according to the present invention will be described below. In the following description, it is assumed that the image forming apparatus of the embodiment is installed on a copying machine. The image forming apparatus assembled in the copying machine is an apparatus for creating an image and transferring the image onto a sheet by a reverse development system based on a document to be copied. An overall structure of the image forming apparatus will be described based on FIGS. 1 to  3 . 
     The image forming apparatus  1  is mainly composed of a photosensitive drum  2 , a discharging unit  3 , an electrifying charger  4 , a developing device  5 , a transfer unit  6 , a cleaner unit  7 , a new toner replenishment device  8  as new toner supply means, and a toner recycle device  9 . 
     The photosensitive drum  2  is a cylindrical drum rotating in one direction (a clockwise direction, that is, a direction of an arrow B in FIG.  1 ). The photosensitive drum  2  has a surface the charged state of which can be arbitrarily adjusted with laser beams. With this arrangement, an image and the like as data to be transferred can be formed on the surface of the photosensitive drum  2  as a latent image by appropriately adjusting the charged state of an arbitrary portion of the surface of the photosensitive drum  2 . 
     The discharging unit  3  is used to remove charge of the surface of the photosensitive drum  2 . The discharging unit  3  includes a discharging lamp  3 A. The charge remaining on the surface of the photosensitive drum  2  is entirely removed by impinging the light from the charge removing lamp  3 A on the surface, thereby the image forming apparatus prepares for the next print. 
     The electrifying charger  4  is used to charge the surface of the photosensitive drum  2 . The surface of the photosensitive drum  2  negatively charged by the electrifying charger  4  is exposed by the laser beams irradiated from a laser unit (not shown), thereby the latent image is formed on the surface. That is, the surface of the photosensitive drum  2  is exposed with the laser beams based on input information such as an image of a document and the like and a surface potential approaches to zero according to the density of the image and the like, thereby the latent image is formed. 
     The developing device  5  is a device for adhering a suitable amount of toner onto the surface of the charged photosensitive drum  2 . Since a two-component development system is employed here, a carrier and toner are accommodated in the developing device  5 , and the ratio of the toner to the carrier is adjusted to about 5 wt %:about 95 wt %. Specifically, the new toner replenishment device  8  and the toner recycle device  9  are appropriately controlled so as to adjust the ratio of the toner to the carrier. The amount of the toner in the developing device  5  is monitored by an automatic toner sensor  11  at all times. When the amount of the toner in the developing device  5  is less than 5 wt %, the new toner replenishment device  8  and the toner recycle device  9  are appropriately controlled by a control unit  70 , which will be described later, and a necessary amount of the toner is replenished. The replenished toner and the carrier are stirred by a mixer unit  5 A in the developing device  5 , and the toner is negatively charged by friction charge when it is stirred. The negatively charged toner is transferred onto the surface of the photosensitive drum  2  by a mag-roller  12  and absorbed by the latent image, thereby a visible image is formed. 
     The transfer unit  6  is used to transfer the toner, which is absorbed by the latent image on the surface of the photosensitive drum  2 , onto a sheet. The transfer unit  6  is mainly composed of a transfer belt  13  and a sheet supply unit  14 . The transfer belt  13  transfers and supports the sheet so that sheet comes into contact with the surface of the photosensitive drum  2  and transfers the visual image onto the sheet. The sheet supply unit  14  is disposed so as to face a portion where the transfer belt  13  is in contact with the photosensitive drum  2 . The sheet, which is supplied from the sheet supply unit  14  to the portion where the transfer belt  13  is in contact with the photosensitive drum  2 , is positively charged and absorbs the negatively charged toner forming the visual image. The sheet onto which the toner has been transferred is supplied to a fixing unit (not shown), and the toner is fusion bonded onto the sheet by thermo compression. 
     The cleaner unit  7  is used to clean the surface of the photosensitive drum  2 . The cleaner unit  7  removes the toner remaining on the surface of the photosensitive drum  2  after the toner has been transferred onto the sheet by the transfer unit  6 . The cleaner unit  7  includes a toner receiver  15  and a discharge auger  16  for discharging the toner removed from the surface of the photosensitive drum  2  to the outside. The toner having been removed from the surface of the photosensitive drum  2  drops onto the toner receiver  15  and is discharged to the toner recycle device  9  side by the discharge auger  16 . 
     The new toner replenishment device  8  is a device for replenishing new toner into the developing device  5 . As shown in FIGS. 2 and 3, the new toner replenishment device  8  is disposed in a direction perpendicular to the developing device  5 . In this state, the new toner replenishment device  8  is disposed forward of a front surface a main body of the copying machine. The new toner replenishment device  8  is composed of a new toner hopper  18 , stir and transfer paddles  19 , a remaining toner detection sensor  20 , and a conveying unit  21 . 
     The new toner hopper  18  is a vessel for storing new toner. The new toner hopper  18  is composed of an approximately semi-circular vessel having an upper open side. The semicircular new toner hopper  18  is divided into a shallow bottom section  18 A and a deep bottom section  18 B at the center of a longitudinal direction. Two sets of the stir and transfer paddles  19  are disposed in the shallow bottom section  18 A in parallel with each other. The remaining toner detection sensor  20  and the conveying unit  21  are disposed in the deep bottom section  18 B. 
     The stir and transfer paddles  19  are devices for transferring the new toner stored in the new toner hopper  18  to the conveying unit  21  while stirring it. As described above, the two sets of the stir and transfer paddles  19  are disposed in the shallow bottom section  18 A in parallel with each other. When the two stir and transfer paddles  19  rotate, the new toner in the new toner hopper  18  is transferred to the conveying unit  21  in the deep bottom section  18 B. The respective stir and transfer paddles  19  are driven by a drive unit (not shown). 
     The remaining toner detection sensor  20  is a sensor for detecting the remaining amount of the new toner stored in the new toner hopper  18 . Since an image cannot be formed if the toner is exhausted, the remaining amount of the toner is detected by the remaining toner detection sensor  20  at all times. Any know sensors such as a magnetic sensor, optical sensor, and the like can be applied to the remaining toner detection sensor  20 . They are appropriately selected depending on an accuracy with which the remaining toner is detected. 
     The conveying unit  21  is used to supply the new toner stored in the new toner hopper  18  into the developing device  5 . The conveying unit  21  is composed of a toner transfer auger  23  and an auger drive unit  24 . The toner transfer auger  23  is composed of a screw conveyer and disposed on the bottom of the deep bottom section  18 B in parallel with the new toner hopper  18 . The toner transfer auger  23  is disposed to face a toner receiving plate  64 , which will be described later, and supplies the new toner stored in the new toner hopper  18 . The auger drive unit  24  is composed of a drive motor (hereinafter, referred to as a “toner hopper motor”)  26  and a reducer  27 . The toner hopper motor  26  is composed of, for example, a stepping motor. The amount of the new toner to be supplied is accurately controlled by controlling the number of rotation and the period of time of rotation of the toner transfer auger  23  by the toner hopper motor  26 . The reducer  27  is composed of a belt  28 , a pulley  29 , and gears  30  to  36 . The gears  30  to  36  are appropriately regulated according to a speed reduction ratio. Stirring bars (not shown) disposed in the deep bottom section  18 B are attached to a rotating shaft of the gear  32 . 
     The toner recycle device  9  is used to transfer the recovered toner collected by the cleaner unit  7  to the developing device  5  in order to reuse it. The toner recycle device  9  is disposed below the new toner replenishment device  8  approximately in parallel with it. As shown in FIGS. 3 to  6 , the toner recycle device  9  is composed of a recovered toner coupling and transfer auger  41  acting as a coupling and transfer unit, a recovered toner sub-hopper  42  acting as recovered toner accommodation means, and a supply auger  43 . 
     The recovered toner coupling and transfer auger  41  is used to transfer the toner collected by the cleaner unit  7  to the developing device  5  side. The recovered toner coupling and transfer auger  41  is composed of, for example, a long screw conveyer, the lower end of the auger  41  is coupled with the discharge auger  16  of the cleaner unit  7 , and the upper end thereof is coupled with the recovered toner sub-hopper  42 . A drive unit  45  of the recovered toner coupling and transfer auger  41  is composed of a drive motor  47  disposed adjacent to the upper end of the recovered toner coupling and transfer auger  41 , a pulley  48  coupled with the recovered toner coupling and transfer auger  41 , a belt  49  for coupling the drive motor  47  with the pulley  48 , and the like. The drive motor  47  is controlled in association with a drive motor of the discharge auger  16  of the cleaner unit  7 . 
     The recovered toner sub-hopper  42  is a vessel for temporarily storing the recovered toner collected by the recovered toner coupling and transfer auger  41  and supplying a necessary amount of it into the developing device  5 . Stirring bars (not shown) are disposed in the recovered toner sub-hopper  42  to stir the recovered toner stored therein. A recovered toner replenishment auger  51  acting as recovered toner replenishment means is disposed to the lower portion in the recovered toner sub-hopper  42 . The rotation of the recovered toner replenishment auger  51  is controlled by a drive unit  52  so that the recovered toner can be supplied to the supply auger  43  in an accurate amount. The drive unit  52  is composed of a drive motor (sub-hopper motor)  53  and a reducer  54 . The sub-hopper motor  53  is composed of, for example, a stepping motor. The reducer  54  is composed of a combination of a belt  55 , a pulley  56 , and gears  57  to  61 . The gears  59  and  60  are disposed on both the sides of the recovered toner sub-hopper  42  across it and coupled with each other through a single rotating shaft, and stir bars (not shown) are attached to the rotating shaft. 
     The recovered toner sub-hopper  42  is filled with an initial developing agent in a manufacturing process of the copying machine or when the copying machine is shipped. A lid of the recovered toner sub-hopper  42  is removed, and the initial developing agent is filled in the recovered toner sub-hopper  42 . Since the recovered toner sub-hopper  42  has an excellent seal property, the initial developing agent does not leak to the outside due to vibration and the like while it is transported. Note that the new toner replenishment device  8  is filled with new toner in the manufacturing process of the copying machine or when the copying machine is shipped. Since the new toner replenishment device  8  also has an excellent seal property, the new toner does not leak to the outside due to vibration and the like while it is transported. 
     The supply auger  43  is used to receive the recovered toner from recovered toner replenishment auger  51  and the new toner from the toner transfer auger  23  of the new toner replenishment device  8  and supplies them into the developing device  5 . The supply auger  43  is composed of an auger unit  63  formed by being extended from the mixer unit  5 A of the developing device  5 , the recovered toner replenishment auger  51  of the toner recycle device  9 , and a toner receiving plate  64  that opens toward the toner transfer auger  23  of the new toner replenishment device  8 . A drive motor (not shown) of the auger unit  63  is disposed on the developing device  5  side. The recovered toner replenishment auger  51  is disposed on the developing device  5  side. In the toner receiving plate  64 , the new toner from the toner transfer auger  23  of the new toner replenishment device  8  is supplied upstream of the recovered toner from the recovered toner replenishment auger  51 . The new toner and the recovered toner having been replenished to the toner receiving plate  64  are mixed with a carrier and stirred in the mixer unit  5 A of the developing device  5 . 
     FIG. 7 is a block diagram showing a control arrangement of the image forming apparatus  1  of the embodiment. 
     A controller (shown as a CPU in FIG. 7)  70  is composed of, for example, a CPU, ROM, RAM, and the like and controls the image forming apparatus  1  in its entirety based on a processing program stored in the ROM, RAM, and the like and according to data stored in the ROM, RAM, and the like and to the outputs from various sensors. 
     The remaining toner detection sensor  20  and the automatic toner sensor  11  described above are connected to input ports of the controller  70  as well as a front cover switch  71  is connected to the sensor  20 . 
     The remaining toner detection sensor  20  detects the amount of the new toner remaining in the new toner hopper  18  as described above, and a magnetic sensor composed of a magnet and a lead switch, for example, can be applied to the remaining toner detection sensor  20 . When the new toner remains in a large amount, the new toner enters between the magnet and the lead switch and a gap is formed therebetween, thereby the lead switch is turned off. In contrast, when the new toner remains in a small amount, no gap is formed therebetween, thereby the lead switch is turned on by the attracting force of the magnet. The controller  70  detects the turning-on and the turning-off of the lead switch. 
     The automatic toner sensor  11  is a toner density ratio sensor for detecting the ratio of the toner (resin) to the carrier (iron) in a developing agent, as described above. The output from the automatic toner sensor  11  is read by the controller  70 . When a toner density drops, the controller  70  drives the toner hopper motor  26  and the like so that the toner is replenished into the developing device  5  and notifies a user of a lack of toner, and the like by displaying it on a control panel (not shown) and the like. 
     The front cover switch  71  is a switch that is turned on and off by opening and closing a main body cover (here, referred to as a “front cover”) of the copying machine. The output signal from the front cover switch  71  is read by the controller  70 , thereby the controller  70  recognizes a state of the front cover. 
     The output ports of the controller  70  are connected to the two motor drivers  72 ,  73  and a charge transformer  74 . 
     The photosensitive drum  2  and the cleaner unit  7  are driven by a drum motor  75 , which is driven in rotation by the motor driver  72 , under the control of the controller  70  when a copy or the like is executed. 
     Likewise, the developing device  5  and the transfer belt  13  are driven by a developing device motor  76  and a transfer belt motor  77 , which are driven in rotation by the motor driver  72 , under the control of the controller  70  when the copy or the like is executed. 
     Further, likewise, the new toner hopper  18 , the recovered toner coupling and transfer auger  41 , and the recovered toner sub-hopper  42  are driven by the toner hopper motor  26 , the coupling and transfer auger motor  47 , and the sub-hopper motor  53 , respectively, which are driven in rotation by the motor driver  73 . 
     Note that while the toner hopper motor  26 , the coupling and transfer auger motor  47 , and the sub-hopper motor  53  are connected to the same motor driver  73 , they can be driven individually under the control of the controller  70 . 
     As described above, the electrifying charger  4  is applied with a high voltage by the charge transformer  74  under the control of the controller  70  and charges the photosensitive drum  2  when the copy and the like are made. 
     In addition, the controller  70  stores a set-up processing function shown in a flowchart of FIG. 8 together with the processing function (not shown) for controlling the image forming apparatus  1  in its entirety. The set-up processing function is set as a subroutine which functions only once when the apparatus  1  is setup. Specifically, whether or not set-up processing is to be executed is determined at the beginning of the processing flow for controlling the image forming apparatus  1  in its entirety, and the set-up processing shown in FIG. 8 is executed only once when the apparatus  1  is set up. 
     Next, a set-up method the image forming apparatus  1  arranged as described above of the copying machine will be described. 
     The set-up processing is executed just after the processing for controlling the image forming apparatus  1  in its entirety is started by turning on a main switch for the first time. That is, the copying machine is installed at a predetermined position, power is supplied thereto, and the main switch is turned on. With this operation, the processing flow for controlling the image forming apparatus  1  in its entirety is started as described above, and it is determined that the set-up processing must be executed at the beginning of the processing flow. With this determination, the set-up processing in FIG. 8 is stated only once when the apparatus  1  is set up. 
     When the set-up processing starts, the sub-hopper motor  53  of the recovered toner sub-hopper  42  of the toner recycle device  9 , the drive motor of the auger unit  63 , and the drive motor of the mixer unit  5 A of the developing device  5  are driven (step ST 1 ). With this operation, the initial developing agent in the recovered toner sub-hopper  42  is supplied to the auger unit  63 , further supplied into the developing device  5  by the auger unit  63 , and stirred by the mixer unit  5 A of the developing device  5 . At this time, the sub-hopper motor  53  of the recovered toner sub-hopper  42  and the drive motor of the auger unit  63  are driven at a rotational speed higher than an ordinary rotational speed, thereby the initial developing agent in the recovered toner sub-hopper  42  is promptly supplied into the developing device  5  in a short time. 
     Next, the process waits until all the initial developing agent in the recovered toner sub-hopper  42  is supplied into the developing device  5  (step ST 2 ). Specifically, the remaining amount of the initial developing agent in the recovered toner sub-hopper  42  is detected by a recovered toner remaining amount detection sensor (not shown) disposed in the recovered toner sub-hopper  42 , and the process waits until the initial developing agent is exhausted. The initial developing agent supplied into the developing device  5  is stirred by the mixer unit  5 A and reaches the mag-roller  12 . 
     When the supply of the initial developing agent in the recovered toner sub-hopper  42  is completed, an initial toner density is set (step ST 3 ). The toner density of the initial developing agent is detected by the automatic toner sensor  11  and set as preference value for automatic toner adjustment. Here, the reference value is set to 5%. 
     On the completion of the initial toner density, the process waits that the image forming apparatus  1  is controlled in its entirety. Then, a job for installing the copying machine is finished without the need of filling new toner because the new toner hopper  18  is already filled with the new toner. 
     Thereafter, the toner recycle device  9  executes an ordinary function. That is, the recovered toner sub-hopper  42  acts as a vessel for temporarily storing the recovered toner. The toner recycle device  9  supplies to the developing device the recovered toner in the recovered toner sub-hopper  42  only in a necessary amount when it is required. 
     As described above, when the copying machine is packaged, the recovered toner sub-hopper  42  of the toner recycle device  9  is filled with the initial developing agent and the developing device  5  is not filled with it. Accordingly, even if a special seal mechanism is not provided when the copying machine is packaged, the leakage of the developing agent can be prevented with reliability during the transportation, and the like thereof. As a result, the toner recycle device  9  can be provided at a less expensive cost. 
     Further, since the new toner hopper  18  is not filled with the initial developing agent, it is possible for the new toner hopper  18  to be filled with the new toner when the product is shipped. Accordingly, a new toner filling job is not necessary when the apparatus  1  is set up. 
     Moreover, since a set-up job can be carried out only by pressing the main switch without the need of filling an initial developing agent and new toner, the set-up job can be easily executed without trouble. As a result, even the user can execute set-up job. 
     Note that while the recovered toner sub-hopper  42  is filled with the initial developing agent in the above embodiment, other portion may be filled with the initial developing agent, in addition to the recovered toner sub-hopper  42 . As long as a portion filled with the initial developing agent is located within a recovered toner transfer path in the toner recycle device  9 , the initial developing agent can be supplied into the developing device  5  by actuating the toner recycle device  9 , thereby the same operation/working effect as that of the above embodiment can be achieved. For example, the initial developing agent may be stored in the recovered toner coupling and transfer auger  41 , or in the recovered toner coupling and transfer auger  41  and the recovered toner sub-hopper  42 . When the initial developing agent is stored also in the coupling and transfer auger  41 , the initial developing agent in the coupling and transfer auger  41  is supplied into the recovered toner sub-hopper  42  and the initial developing agent in the recovered toner sub-hopper  42  is supplied into the developing device  5  by actuating the overall toner recycle device  9  when the apparatus  1  is set up. 
     Further, in the above embodiment, the initial toner density is set by executing the set-up processing by turning on the main switch, the set-up processing and the initial set of the toner density may be executed using the selection of an automatic toner adjustment mode as a trigger. That is, when the automatic toner adjustment mode, in which the toner density of the developing agent is automatically set to a set value, can be arbitrarily selected manually, the above processing may be executed using the selection of the automatic toner adjustment mode as the trigger. The same operation/working effect as that of the above embodiment can be achieved also in this case. 
     Also, in the above embodiment, the example in which the new toner replenishment device  8  is used as means for replenishing the new toner, new toner replenishment means using a cartridge may be also applied to the present invention. The same operation/working effect as that of the above embodiment can be achieved also in this case. 
     Also, while the mixture of the toner and the carrier is used as the developing agent, only the toner may be used. The same operation/working effect as that of the above embodiment can be achieved also in this case. 
     While the copying machine is described as an example in the above respective embodiments, the application of the image forming apparatus is by no means limited to the copying machine, and the apparatus can be applied to any other equipment for forming an image using toner such as a printer, facsimile and the like. 
     Further, the image forming apparatus can be also applied to a color copying machine. In this case, the image forming apparatus is applied to each of four sets of the image forming apparatuses  1  for three primary colors and black.