JP5716463B2 - Image forming apparatus, control method, and control program - Google Patents

Description

  The present invention relates to an image forming apparatus, a control method, and a control program.

2. Description of the Related Art Conventionally, as one of developing methods used in an electrophotographic image forming apparatus, a method in which toner is clouded (hopped state, hereinafter referred to as flare development) is known (for example, see Patent Document 1).
In this flare development system, the toner is clouded by alternately applying reverse-phase pulses to the flare development apparatus and repeating charge and discharge.

In order to reduce the size and cost of the power supply, the output of one high-voltage power supply unit (high-voltage power supply circuit) is distributed and fed to multiple developing devices (flare developing devices) to prevent longer life and toner scattering. Depending on the image forming mode (for example, monochrome mode), in order to avoid application to a developing device that is not used (flare developing device corresponding to color toner), a function of electrically disconnecting the developing device as these loads is provided. An image forming apparatus is also proposed.
In such an image forming apparatus that electrically connects or disconnects the developing device as a load, when switching from the monochrome mode to the full color mode, or when switching from the full color mode to the monochrome mode, the image forming timing and In order to match the output timing of the high-voltage power supply unit, the output of the high-voltage power supply unit is temporarily stopped and then the output of the high-voltage power supply unit is resumed.

  However, since the output of the high-voltage power supply unit is temporarily stopped in the conventional technique, the output of the high-voltage power supply unit is not always stable at the stage of shifting to the image forming timing, and the image forming quality is deteriorated. There was a fear.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus, a control method, and a control program capable of switching without stopping the output of the high-voltage power supply unit even when a plurality of developing devices share the high-voltage power supply unit and switch the printing mode. Is to provide.

In order to solve the above-described problems and achieve the object, an image forming apparatus of the present invention includes an image carrier, a high-voltage power supply unit that generates a high-voltage pulse signal for clouding toner, and the high-voltage power supply unit. A plurality of development units connected to supply the high-voltage pulse signal to the toner to float the toner and perform flare development, and to form an image on the image carrier; and the plurality of developments A connection switching unit that switches electrical connection and disconnection to the high-voltage power supply unit with respect to a predetermined part of the development units of the unit, and an image forming sequence in the image forming unit that indicates a switching timing in the connection switching unit. and control means for synchronizing the said developing unit has a developing device columnar metal core constitutes one of the electrodes, said high voltage power supply means, the peripheral surface of the core metal The control means has a contact arranged so as to be electrically connectable and detachable, and the control means causes the connection switching means to physically move the mandrel along its rotation axis, thereby providing electric power to the high-voltage power supply means. The connection or disconnection is switched through the contact point.

The control method of the present invention includes an image carrier, a high-voltage power supply unit that generates a high-voltage pulse signal for clouding toner, a plurality of developing units that can supply the high-voltage pulse signal , and the plurality of developing units. A connection switching unit that switches electrical connection to and disconnection from the high-voltage power supply unit with respect to a predetermined part of the development unit of the unit, and the development unit includes a cylindrical metal core that has one electrode A control method executed in an image forming apparatus having contacts arranged so as to be electrically connected to and disconnected from the peripheral surface of the core metal, the developing device comprising: An image forming process in which the high voltage pulse signal is supplied to the developing unit according to an image forming sequence to float the toner and flare development to form an image on the image carrier; and the plurality of developments For a given portion of the development unit of the knitting, by moving physically along its axis of rotation the core metal to the connection switching unit, electrically connected to said high voltage power supply means, the switching of the disconnect , And a process of performing via the contact and a process of synchronizing the switching timing with the imaging sequence .

The control program of the present invention includes an image carrier, a high-voltage power supply unit that generates a high-voltage pulse signal for clouding toner, a plurality of developing units that can supply the high-voltage pulse signal , and the plurality of developing units. A connection switching unit that switches electrical connection to and disconnection from the high-voltage power supply unit with respect to a predetermined part of the development unit of the unit, and the development unit includes a cylindrical metal core that has one electrode A control program for controlling, by a computer, the image forming apparatus having contacts arranged so as to be electrically connected to and disconnected from the peripheral surface of the core metal. The computer supplies the high-pressure pulse signal to the developing unit in accordance with a predetermined image forming sequence to float the toner and perform flare development. And image forming means for performing image formation on the carrier, for a given portion of the development unit of the plurality of developing units, move the metal core to physically along its axis of rotation to the connection switching unit by the electrical connection to said high voltage power supply means, the switching of the disconnection, and means for causing through the contact, and means for synchronizing the switching timing in the image forming sequence, characterized thereby to function with To do.

  According to the present invention, even when a high voltage power supply unit is shared by a plurality of developing devices and the print mode is switched, the output of the high voltage power supply unit can be switched without being stopped.

FIG. 1 is a schematic configuration diagram of a color image forming system having an image forming apparatus according to an embodiment. FIG. 2 is an explanatory diagram of an example of an image forming unit constituting the image forming unit. FIG. 3 is a schematic explanatory diagram of a power supply system of the image forming apparatus. FIG. 4 is an explanatory diagram of the relationship between the developing device constituting the developing device and the cloud pulse signal. FIG. 5 is an explanatory diagram of a hardware configuration for driving the developing device to perform contact / separation of mechanical contacts. FIG. 6 is a diagram for explaining the configuration and operation of the contact / separation part. FIG. 7 is an operation timing chart of the embodiment. FIG. 8 is an explanatory diagram of image formation. FIG. 9 is an operation processing flowchart of the image forming apparatus according to the embodiment.

  Exemplary embodiments of a power supply apparatus, an image forming apparatus, and a power supply control method according to the present invention will be described below in detail with reference to the accompanying drawings.

  The image forming apparatus according to the present embodiment is generally called a multi-function machine having at least two functions among a copy function, a printer function, a scanner function, and a facsimile function, and converts a document into read image data. An image reading unit, an image processing unit that performs image processing on image data obtained by reading an original with the image reading unit, and an image forming unit (image forming unit) that forms an image on a paper surface based on the image processed image data The image processing unit and the image forming unit (image forming unit) are housed inside the housing, and the front surface of the housing can be opened and closed by an exterior cover.

FIG. 1 is a schematic configuration diagram of a color image forming system having an image forming apparatus according to an embodiment.
The color image forming system 100 is roughly classified into an information terminal device 101 configured as a personal computer having a microprocessor, a ROM, a RAM, an external storage device and the like (not shown), and a print command (printing) generated by the information terminal device 101. An image forming apparatus 103 that receives a job) via the communication network 102 and is configured as a printer or the like and performs image formation.

The first control board unit 111 of the image forming apparatus 103 has a communication interface, and controls the entire image forming apparatus 103 based on a print command received from the information terminal apparatus 101 via the communication network 102. More specifically, the first control board 111 sets a recording paper size, a print mode (monochrome mode / full color mode), and the like based on a print command received via the communication network 102. Here, the first control board 111 is configured as a microcomputer having an MPU, a ROM, a RAM, and the like (not shown), and controls the image forming apparatus 103 according to a control program stored in the ROM.
The second control board unit 112 performs actual image formation control for controlling the third control board unit 113 based on the set recording paper size, print mode, and the like under the control of the first control board unit 111.

The third control board unit 113 performs drive control of a high voltage power supply unit 114 (not shown), a motor and a fan (not shown) under the control of the second control board unit 112.
The high voltage power supply unit 114 has a full bridge circuit (not shown), and generates and outputs a high voltage pulse signal for setting the toner in a floating state (hopping state).
The image processing unit 115 performs drive control of a laser beam (not shown) based on image processing data set and output by the first control board unit 111 and including the recording paper size, print mode, print data, and the like. A latent image is formed on the photosensitive drum (image carrier) constituting the image forming apparatus.
The image forming unit 116 develops the latent image formed on the photosensitive drum based on the high-voltage pulse signal, transfers the image to a recording sheet, fixes it, and outputs the image.

FIG. 2 is an explanatory diagram of an example of an image forming unit constituting the image forming unit.
First, the image forming unit 116 has four photosensitive drums 10Y, 10M, 10C, and 10K that function as image carriers and latent images formed on the photosensitive drums 10Y, 10M, 10C, and 10K in different colors. A plurality of developing devices (developing rollers) 11Y, 11M, 11C, and 11K (hereinafter simply referred to as the developing device 11 when there is no need to distinguish between them) and different color toners. An intermediate transfer belt 16 serving as an image carrier that rotates in the direction of arrow A, on which images are primarily transferred in a superimposed state, is provided.

  The intermediate transfer belt 16 is an endless belt. In the present embodiment, above the intermediate transfer belt 16, along the rotational direction A of the intermediate transfer belt 16, the above-described four photosensitive drums 10Y, 10M, and 10C for black, cyan, magenta, and yellow are used. , 10K (hereinafter, simply referred to as the photosensitive drum 10 when there is no need to distinguish between them) are arranged in parallel. Around the photosensitive drum 10, a charging device 12, the developing device 11 described above, a primary transfer roller 14 constituting a primary transfer device, and a cleaning device 13 are disposed.

  The photosensitive drum 10 is rotationally driven in the rotation direction B. At this time, the charging device 12 charges the surface of the photosensitive drum 10 to a predetermined polarity. Next, the charged surface is irradiated with laser light emitted from the exposure device 15, thereby forming an electrostatic latent image on the photosensitive drum 10, and the electrostatic latent image is converted into a toner image of each color by the developing device 11. Visualized.

  A primary transfer roller 14 is disposed opposite to each photoconductor drum 10, and rotates with the intermediate transfer belt 16 sandwiched between each primary transfer roller 14 and the photoconductor drum 10. It has become.

  At this time, the intermediate transfer belt 16 is supported by two rollers, a driving roller 17 and a tension roller 19. Although the intermediate transfer belt 16 may be stretched by three or more rollers, in order to reduce the size as much as possible and suppress the height, in this embodiment, the intermediate transfer belt 16 is stretched by two rollers. , Suppress the height.

  Next, a toner image visualized on each photosensitive drum 10 is transferred onto the surface of the intermediate transfer belt 16 by the action of the primary transfer roller 14. In this manner, the black (K), cyan (C), magenta (M), and yellow (Y) toner images are transferred in a state of being sequentially and accurately superimposed on the intermediate transfer belt 16, thereby synthesizing a full color. A color image is formed.

  On the other hand, a secondary transfer roller 18 is disposed opposite to the driving roller 17 (secondary transfer counter roller) with the intermediate transfer belt 16 interposed therebetween, and the paper P as a recording medium is fed from the paper feed unit 21. . Accordingly, the sheet P is fed between the driving roller 17 and the secondary transfer roller 18 at a predetermined timing by the rotation of the registration roller pair 22. Then, the composite color image carried on the intermediate transfer belt 16 is collectively transferred onto the paper P by the action of the secondary transfer roller 18.

  Then, the toner image on the paper P is fixed by heat and pressure by the fixing device 23 and discharged onto a paper discharge tray (not shown). Transfer residual toner adhering to the surface of the intermediate transfer belt 16 after the toner image secondary transfer is removed by the cleaning device 20.

  Although FIG. 2 shows an example of a method of transferring to a sheet via a secondary transfer roller, an image forming unit of a method of transferring directly to a sheet may be used.

  In the present embodiment, the developing device 11 as the image forming unit applies a high voltage power source unit for flare development to a high-capacity flare developing device, thereby developing the flare development in a state where toner is hopped. It is carried out.

FIG. 3 is a schematic explanatory diagram of a power supply system of the image forming apparatus.
The power supply system of the image forming apparatus 103 is a cloud generated by the high-voltage conversion unit (full bridge circuit) 114A in the developing devices 11K, 11Y, 11M, and 11C under the control of the third control board unit 113 as loads. The pulse signal CP is supplied. In this case, a high voltage converter 114A is connected to the developing devices 11Y, 11M, and 11C via a mechanical contact MC to control supply / cutoff of the cloud pulse signal CP to the developing devices 11Y, 11M, and 11C. It can be configured. This is because when the print mode is the monochrome mode, the developing devices 11Y, 11M, and 11C do not need to be used. Therefore, in order to reduce power consumption, the developing devices 11Y, 11M, and 11C are electrically connected. This is because it is preferable to cut off the supply of the cloud pulse signal CP.

FIG. 4 is an explanatory diagram of the relationship between the developing device constituting the developing device and the cloud pulse signal.
The developing devices 11K, 11Y, 11M, and 11C cloud the toner and rotate it to carry the toner.

As shown in FIG. 4A, the developing device 11 is formed by stacking a cylindrical cored bar 51 configured as one electrode and an insulating layer 52 on the cored bar 51 to form the other electrode. In order to protect the electrode formed on the electrode layer 53 and the electrode layer 53, a surface layer 54 covering the electrode layer 53 is provided.
Thus, since the insulating layer 52 is provided between the pair of electrodes (the core metal 51 and the electrode layer 53), the developing device 11 forms a capacitive load.

A plurality of electrodes 53 </ b> A constituting the electrode layer 53 are provided at a predetermined interval while extending in a direction orthogonal to the rotation direction of the developing device 11.
Here, the metal core 51 is supported by a pair of ring-shaped support members 55 that can rotate and can slide in the left-right direction in FIG. 4. Further, the core metal 51 is urged leftward in FIG. 4 by an elastic member (spring, leaf spring, etc.) 56 in order to hold the core metal 51 in a predetermined operation position when the toner is clouded. ing.
Then, as shown in the upper part of FIG. 4B, the A-phase cloud pulse signal CP having the minimum value Vmin and the peak value Vpp is generated by the high-voltage conversion unit 114A constituting the high-voltage power supply unit 114. And a cloud pulse signal CP of B phase opposite to the A phase as shown in the lower part of FIG. 4B is applied to the cored bar 51 to form a toner cloud state. .

FIG. 5 is an explanatory diagram of a hardware configuration for driving the developing device to perform contact / separation of mechanical contacts.
In the present embodiment, when the printing mode is the monochrome mode, the developing devices 11Y, 11M, and 11C, which are developing devices that are not used in the monochrome mode, are temporarily disconnected from the high-voltage power supply unit 114, thereby providing a high voltage. The power supply unit 114 is shared.

  For this reason, as shown in FIG. 5, image forming signals GF1 to GF4 that become “H” level during the image forming period and become “L” level during the image non-forming period for each color (BK, C, M, Y). When the color information signal COL that is “H” level in the monochrome mode and “L” level in the full color mode is input, and the image forming signals GF1 to GF4 and the color information signal COL are all at the “H” level, An AND circuit 61 that outputs the contact contact / separation control signal SC as “H” level and a power supply circuit that supplies power from the high potential side power source VP when the contact contact / separation control signal SC becomes “H” level. 62 and a contact contacting / separating portion 63 having a solenoid that contacts and separates contacts, which will be described later, upon receiving power supply from the power supply circuit 62.

  The power supply circuit 62 has a base terminal B connected to the output terminal of the AND circuit 61, an emitter terminal E connected to the ground (GND), and a first transistor TR1 composed of a bipolar transistor, and a collector terminal of the first transistor TR1. A base terminal B is connected to C, a high potential side power source VP is connected to an emitter terminal E via a current limiting resistor R, a collector terminal C is connected to a contact contact / separation portion 63, and a second transistor configured by a bipolar transistor TR2.

FIG. 6 is a diagram for explaining the configuration and operation of the contact / separation part.
The contact contact / separation unit 63 receives power supply from the power supply circuit 62 and is driven to the right as shown in FIG. 6 (b). As shown, a solenoid 64 driven to a standby position is provided.

In the initial state, the peripheral surface of the cored bar 51 is in physical contact with the conductive frame FR, and is electrically connected to the high voltage power supply unit 114 via the frame FR and the contact 114C. The cloud pulse signal CP can be supplied from the high voltage conversion unit 114A of the unit 114.
When the contact contact / separation part 63 receives power supply from the power supply circuit 62 in the initial state, the solenoid 64 of the contact contact / separation part 63 is driven rightward as shown in FIG. .
As a result, one end (left end in FIG. 6) of the core bar 51 of the developing device 11 is brought into contact with the urging force of the elastic member 56, and the developing device 11 is moved in the right direction along the rotation axis of the core bar 51. Move to. Thereby, the metal core 51 is moved by the movement distance DL in FIG. 6, and the peripheral surface of the metal core 51 is cut off from the conductive frame FR.

As described above, when the metal core 51 is physically disconnected from the contact point 114C and the frame FR and is electrically disconnected from the contact point 114C of the high voltage power supply unit 114, the cloud pulse signal CP supplied from the high voltage power supply unit 114 is obtained. Is not supplied to the developing device 11, and the developing device 11 is in a non-driven state and does not consume power.
According to the above-described procedure, in the monochrome mode, the developing devices 11Y, 11M, and 11C are in a non-driven state during a period in which the developing devices 11Y, 11M, and 11C are electrically disconnected from the high voltage power supply unit 114, thereby reducing power consumption.

Next, the operation of the embodiment will be described.
FIG. 7 is an operation timing chart of the embodiment.
FIG. 8 is an explanatory diagram of image formation.
FIGS. 7A to 7D show the cloud pulse signal CP in order to cause the developing devices 11K, 11C, 11M, and 11Y to output the cloud pulse signal CP from the high-voltage power supply unit 114 to perform image formation. PWM control signals PWM1 to PWM4 that are at the “H” level when a PWM signal corresponding to is output.
Therefore, the period during which the PWM control signals PWM1 to PWM4 are at the “H” level is a period in which image formation is possible.

FIGS. 7E to 7H show the image forming signals GF1 to GF4 that become “H” level during image formation.
Therefore, it indicates that image formation is possible during the period from time t1 to time t2.
More specifically, as shown in FIG. 8, the image forming direction is indicated by an arrow GFD in order to actually form an image (here, the image includes character information and the like) of the paper P to be image formed. As a direction, it is from the leading position PS of the paper P to the terminal position PE of the paper P, from the image forming possible start position ST to the image forming possible end position ED. In FIG. 8, symbols P1 and P2 represent image forming areas that do not include character data such as bitmap data as print data.

In FIG. 7, the image formable start position ST on the paper P corresponds to time t1, and the image formable end position ED corresponds to time t2.
Note that the image formable start position ST and the image formable end position ED merely represent positions where an image can be formed, and whether an image is actually formed depends on an input print job (JOB). Depends on the print data included.

  FIG. 7 (i) is a color information signal COL representing the print mode. The color information signal COL is “H” level when the print mode is the monochrome mode, and “L” level when the print mode is the full color mode. Note that the print mode is not set for each paper P or for a print job, and even for a single paper P, the monochrome mode and the full color mode may be mixed. That is, in an area where only monochrome printing is performed in the printing process of one sheet P (for example, only black characters, only a monochrome image, or a mixture of these), the monochrome mode is set. In the area, the full color mode is set.

  The developing device 11K is used in both the monochrome mode and the full color mode, but the developing devices 11C, 11M, and 11Y are not used in the monochrome mode.

Therefore, in the present embodiment, the print mode is the monochrome mode, and in the period from the image formation possible start position ST to the image formation possible end position ED, for example, the period from time t1 to time t2, FIG. As shown in (b), the solenoid 64 is driven to physically disconnect the metal core 51 from the conductive frame FR, and to electrically disconnect the metal core 51 from the contact 114C and the frame FR, The power consumption is reduced by not supplying the cloud pulse signal CP to the developing devices 11C, 11M, and 11Y.
Then, when the image forming possible end position ED is reached, the drive of the solenoid 64 is stopped, and the cored bar 51 is physically contacted from the conductive frame FR as shown in FIG. The core metal 51 is electrically connected from the FR, and the supply of the cloud pulse signal CP to the developing devices 11C, 11M, and 11Y is resumed to prepare for the next image formation.

FIG. 9 is an operation processing flowchart of the image forming apparatus according to the embodiment.
When receiving the print job from the information terminal device 101, the first control board unit 111 of the image forming apparatus 103 starts executing the print job (step S11).
Subsequently, the first control board unit 111 determines whether or not color information is included in the print job, that is, whether the print mode is a monochrome mode or a full color mode (step S12).

If it is determined in step S12 that the print job includes color information, that is, if the print mode is the full color mode (step S12; Yes), the solenoid 64 is in a non-driven state (solenoid off state). Therefore, in addition to supplying the cloud pulse signal CP to the developing device 11K, the cloud pulse signal CP is supplied to the developing devices 11C, 11M, and 11Y to form an image (step S13).
Subsequently, the first control board unit 111 determines whether or not the print job is finished (step S14).
If it is determined in step S14 that the print job has not been completed (step S14; No), the first control board unit 111 enters a standby state.

On the other hand, if it is determined in step S14 that the print job is completed (step S14; Yes), the process is terminated and the next print job is waited for.
Further, when the color information is not included in the print job in the determination of step S12, that is, when the print mode is the monochrome mode (step S12; No), the first control board unit 111 displays the image processing unit. The image forming unit 116 is controlled via 115, the solenoid 64 is driven (solenoid ON state) in synchronization with the image forming sequence, and the supply of the cloud pulse signal CP to the developing device 11K is continued, and the core The gold 51 is physically disconnected from the conductive frame FR, the core metal 51 is electrically disconnected from the contact 114C and the frame FR, and the cloud pulse signal CP is supplied to the developing devices 11C, 11M, and 11Y. In such a manner, image formation is performed (step S15).

Subsequently, the first control board unit 111 determines whether or not the print job is completed (step S16).
If it is determined in step S16 that the print job has not ended yet (step S16; No), unlike the case of the full color mode, the process proceeds to step S12 again, and the first control board unit 111 performs printing. It is determined whether or not the job includes color information, that is, whether the print mode is the monochrome mode or the full color mode (step S12).

As shown in FIG. 8, among the print target areas AR, for example, only the photo area P1 and the photo area P2 need full color printing, color information is included in the middle of the print job, and the rest are only characters. This is to cope with the case where monochrome printing is performed.
On the other hand, if it is determined in step S16 that the print job has ended (step S16; Yes), the first control board unit 111 ends the process and waits for the next print job to be received.

  As described above, according to the present embodiment, the high voltage power supply unit 114 is electrically connected to the developing devices 11C, 11M, and 11Y used only in the full color mode in synchronization with the image forming sequence in the monochrome mode. Therefore, the print mode can be switched without stopping the high-voltage power supply unit 114.

That is, when the mode is shifted to the monochrome mode, the high-voltage power supply unit 114C, 11M, and 11Y used only in the full-color mode in which image formation is not performed in the monochrome mode printing is performed without stopping the high-voltage power supply unit 114. Since the output from the unit 114 can be cut off, unnecessary power consumption can be reduced. That is, when the power consumption in the full color mode is 100%, the power consumption in the monochrome mode can be reduced to approximately 25%, and the power consumption can be reduced by approximately 75%.
Further, the time required to stop the high-voltage power supply unit 114 is not required when switching the print mode, and the printing throughput can be improved.
Furthermore, since the high-voltage power supply unit 114 is not stopped even when the printing mode is switched, it is possible to suppress a decrease in image formation quality due to an unstable supply voltage when the high-voltage power supply unit is restarted.
In addition, when the output from the high voltage power supply unit 114 is cut off from the developing devices 11C, 11M, and 11Y, the mechanical contact MC is used. By blocking the output from the power supply unit 114, the power consumption can be reliably reduced.
Furthermore, since there is only one high-voltage power supply system, the image forming apparatus is compared with a case where a high-voltage power supply unit is provided for each of the developing devices 11K, 11C, 11M, and 11Y (four high-voltage power supply systems). Can be reduced in weight.

  In the above embodiment, the image forming apparatus of the present invention has been described as an example in which the image forming apparatus is applied to a multifunction machine having at least two functions among a copy function, a printer function, a scanner function, and a facsimile function. The present invention can be applied to any image forming apparatus such as a printer and a facsimile apparatus.

  Further, the present invention is not limited to the embodiment described in the mode for carrying out the invention. Modifications can be made without departing from the spirit of the present invention.

10, 10K, 10Y, 10C, 10M Photosensitive drum (image carrier)
11, 11K, 11Y, 11C, 11M Development device (development unit)
51 Core Bar 52 Insulating Layer 53 Electrode Layer 53A Electrode 54 Surface Layer 55 Support Member 56 Elastic Member 61 AND Circuit 62 Power Supply Circuit 63 Contact Contact / Separation Portion 64 Solenoid 100 Color Image Forming System 101 Information Terminal Device 102 Communication Network 103 Image Forming Device 111 1st control board part 112 2nd control board part 113 3rd control board part 114 High voltage power supply part 114A High voltage conversion part 114C Contact point 115 Image processing part 116 Imaging part COL Color information signal CP Cloud pulse signal DL Moving distance GF1-GF4 image Formation signal MC Mechanical contact P Paper SC Contact contact / separation control signal

JP 2010-044167 A

Claims (5)

An image carrier;
High-voltage power supply means for generating a high-voltage pulse signal for clouding toner;
An image forming means for connecting to the high voltage power supply means and supplying a high voltage pulse signal to the toner to float the toner and performing flare development, and forming an image on the image carrier; ,
For a given portion of the development unit of the plurality of developing units, electrical connection to said high voltage power supply unit, a connection switching means for switching disconnection,
Control means for synchronizing the switching timing in the connection switching means with the image forming sequence in the image forming means ,
The developing unit has a developing device in which a cylindrical cored bar constitutes one electrode,
The high-voltage power supply means has a contact disposed so as to be electrically connected to and disconnected from the peripheral surface of the cored bar,
The control means causes the connection switching means to physically move the metal core along its rotation axis, thereby switching electrical connection and disconnection to and from the high-voltage power supply means via the contacts. about
An image forming apparatus feature a. The image forming means has a monochrome mode and a full color mode as operation modes, and an image forming signal is input during an image formable period,
The control means, when an image forming signal is input to the image forming means, and when the operation mode is a monochrome mode, the connection switching means physically moves the core metal along its rotation axis.
The image forming apparatus according to claim 1 . The control means causes the connection switching means to perform switching at the transition timing from the full color mode to the monochrome mode.
The image forming apparatus according to claim 2 . An image carrier, a high-voltage power supply unit that generates a high-voltage pulse signal for clouding toner, a plurality of development units that can supply the high-voltage pulse signal, and a predetermined partial development of the plurality of development units The unit includes an electrical connection to the high-voltage power supply unit, and a connection switching unit that performs switching of disconnection ,
The developing unit has a developing device in which a cylindrical cored bar constitutes one electrode,
The high-voltage power supply means is a control method executed in an image forming apparatus having contacts arranged so as to be electrically connected to and disconnected from the peripheral surface of the core metal ,
An image forming process for supplying the high-voltage pulse signal to the developing unit according to a predetermined image forming sequence to float the toner and performing flare development to form an image on the image carrier;
Electrical connection to the high-voltage power supply means by physically moving the cored bar along the rotation axis to the connection switching unit with respect to a predetermined part of the plurality of development units, A process of switching separation through the contact ;
Synchronizing the switching timing with the imaging sequence;
A control method comprising: An image carrier, a high-voltage power supply unit that generates a high-voltage pulse signal for clouding toner, a plurality of development units that can supply the high-voltage pulse signal, and a predetermined partial development of the plurality of development units The unit includes an electrical connection to the high-voltage power supply unit, and a connection switching unit that performs switching of disconnection ,
The developing unit has a developing device in which a cylindrical cored bar constitutes one electrode,
The high-voltage power supply means is a control program for controlling an image forming apparatus having a contact disposed so as to be electrically connected to and disconnected from the peripheral surface of the core metal by a computer,
The computer,
An image forming means for supplying the high-voltage pulse signal to the developing unit according to a predetermined image forming sequence to float the toner and performing flare development to form an image on the image carrier;
Electrical connection to the high-voltage power supply means by physically moving the cored bar along the rotation axis to the connection switching unit with respect to a predetermined part of the plurality of development units, Means for switching separation through the contact ;
Means for synchronizing the switching timing with the imaging sequence;
A control program characterized by functioning as a function.

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