JP2020160357A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of surely preventing the generation of a leak current. An image forming apparatus (1) includes a tray (11) for accommodating a recording sheet (P), a photoconductor drum (33Y, 33M, 33C, 33K), and a transfer roller (32Y, 32M, 32C, 32K). ), A transport unit (2), and a voltage application unit (5). The transfer roller (32Y, 32M, 32C, 32K) prints the developer image formed on the surface of the photoconductor drum (33Y, 33M, 33C, 33K) on the recording sheet (P) by applying the transfer voltage. Transcribe. The transport unit (2) transports the recording sheet (P) housed in the tray (11) to the transfer position (W). Then, the voltage application unit (5) starts applying a predetermined voltage having the same polarity as the transfer voltage to the transport unit (2) before the tip of the recording sheet (P) reaches the transfer position (W), and the recording sheet. After the rear end of (P) has passed through the transport unit (2), the application of a predetermined voltage ends. [Selection diagram] Fig. 2

Description

The present invention relates to an image forming apparatus.

Conventionally, in an image forming apparatus such as a color printer, when a toner image formed on a photoconductor drum is transferred to a recording sheet, a predetermined transfer is performed to the transfer roller at a timing when the recording sheet is transferred to a transfer position by a transfer roller. By applying a voltage, the toner image is transferred to a desired portion of the recording sheet and printing is started. At this time, a part of the transfer current due to the transfer voltage applied to the transfer roller flows from the recording sheet to the transfer roller as a leak current, which may cause transfer defects such as white spots that are not printed on the printed portion.

Therefore, a current detection unit for detecting the leak current is provided, and when a leak current larger than the reference current value is detected by the current detection unit, a predetermined voltage having the same polarity as the transfer voltage is applied to the transport roller. As a result, an image forming apparatus in which the leakage current is reduced to a reference current value or less has been proposed (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2008-83233

In the image forming apparatus of Patent Document 1, after printing is started by applying a transfer voltage to the transfer roller, when a leakage current is detected by the current detection unit, a predetermined voltage is applied to the transfer roller to whiten the image. This is to prevent transfer defects such as omission. Therefore, it is not possible to suppress the generation of the leak current from the time when the recording sheet reaches the transfer position and the leakage current is generated until the predetermined voltage is applied to the transport roller, and the transfer failure immediately after the start of printing is caused. There is a problem that it cannot be prevented.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an image forming apparatus capable of reliably preventing the generation of a leak current.

In order to solve the above problems, the image forming apparatus according to one aspect of the present invention includes a tray for accommodating a recording sheet, a photoconductor drum, a transfer roller, a conveying unit, and a voltage applying unit. There is. The transfer roller sandwiches and conveys the recording sheet between the photoconductor drum and the photoconductor drum at the transfer position, and transfers the developer image formed on the surface of the photoconductor drum to the recording sheet by applying the transfer voltage. To do. The transport unit is located upstream of the transfer position in the transport direction of the recording sheet, and transports the recording sheet contained in the tray to the transfer position. The voltage application unit applies a predetermined voltage having the same polarity as the transfer voltage to the transport unit. The voltage application unit starts applying a predetermined voltage having the same polarity as the transfer voltage to the transfer unit before the tip of the recording sheet reaches the transfer position, and applies the predetermined voltage after the rear end of the recording sheet passes through the transfer unit. It is characterized by ending.

According to the image forming apparatus having the above configuration, the voltage application unit starts applying a predetermined voltage having the same polarity as the transfer voltage to the transport unit before the tip of the recording sheet reaches the transfer position, and after the recording sheet. After the end passes through the transport section, the application of the predetermined voltage ends. As a result, it is possible to prevent the generation of a leak current from the recording sheet to the transport section by keeping a predetermined voltage applied to the transport section from immediately after the start of transfer until the recording sheet has passed through the transport section. , Transfer defects can be reliably prevented.

Further, in the image forming apparatus according to one aspect of the present invention, it is preferable that the voltage application unit starts applying a predetermined voltage to the transfer unit before the transfer unit starts the transfer of the recording sheet.

According to the image forming apparatus having the above configuration, the voltage application unit starts applying a predetermined voltage to the transport unit before the transport unit starts transporting the recording sheet, so that the leakage current from the recording sheet to the transport unit is generated. Occurrence can be reliably prevented, and transfer defects can be prevented more reliably.

Further, in the image forming apparatus according to one aspect of the present invention, the transport unit includes a transport roller and a rising plate. The transfer rollers are arranged upstream of the transfer position and downstream of the tray in the transfer direction, and transfer the recording sheet from the transfer start position to the transfer position. The raising plate raises the recording sheet housed in the tray to the transport start position. The voltage application unit preferably applies a predetermined voltage to either the transport roller or the riser plate.

According to the image forming apparatus having the above configuration, the voltage application unit applies a predetermined voltage to either the transfer roller or the riser plate, so that the transfer current due to the transfer voltage of the recording sheet is transferred from the transfer roller or the riser plate. Leakage can be reliably prevented.

Further, in the image forming apparatus according to one aspect of the present invention, it is preferable that the voltage applying unit starts applying a predetermined voltage to the rising plate before the rising plate raises the recording sheet to the transport start position.

According to the image forming apparatus having the above configuration, the voltage applying unit starts applying the voltage to the rising plate before the recording sheet is raised to the transfer start position by the rising plate, so that a leakage current is generated in the rising plate. Can be prevented more reliably.

Further, in the image forming apparatus according to one aspect of the present invention, it is preferable that the voltage applying unit ends applying a predetermined voltage after the rear end of the recording sheet is discharged from the tray by the conveying roller.

According to the image forming apparatus having the above configuration, the voltage application unit ends the voltage application to the transfer unit after the rear end of the recording sheet is discharged from the tray by the transfer roller, so that the power consumption applied to the transfer unit is consumed. It is possible to prevent the generation of leak current to the transport section while suppressing the above.

Further, the image forming apparatus according to one aspect of the present invention includes a paper feed motor for driving the transport unit. It is preferable that the voltage application unit ends applying a predetermined voltage at the same time as the paper feed motor is stopped.

According to the image forming apparatus having the above configuration, the voltage application unit ends the voltage application to the transfer unit at the same time as the paper feed motor is stopped, so that the voltage application to the transfer unit is suppressed while suppressing the power consumption applied to the transfer unit. Leakage current can be prevented.

Further, the image forming apparatus according to one aspect of the present invention has a discharge port for discharging the recording sheet, a fixing portion for fixing the developer image transferred to the recording sheet, and fixing on the upstream side in the transport direction from the discharge port. It is provided on the downstream side in the transport direction with respect to the portion, and includes a sensor for detecting that the recording sheet has passed a predetermined position on the downstream side in the transport direction with respect to the fixing portion. It is preferable that the voltage applying unit ends applying the predetermined voltage when the sensor detects that the recording sheet has passed the predetermined position.

According to the image forming apparatus having the above configuration, when the sensor detects that the recording sheet has passed a predetermined position on the downstream side in the transport direction from the fixing portion, the application of the predetermined voltage to the transport portion is terminated. , It is possible to suppress the application of unnecessary voltage to the transport unit.

Further, in the image forming apparatus according to one aspect of the present invention, a preliminary transfer voltage having an absolute value smaller than the transfer voltage is applied to the transfer roller before the transfer voltage is applied. It is preferable that the voltage application unit starts applying a predetermined voltage at the same time as the application of the preliminary transfer voltage is started.

According to the image forming apparatus having the above configuration, the transfer voltage is applied to the transfer roller well by applying the preliminary transfer voltage having an absolute value smaller than the transfer voltage before the transfer voltage is applied to the transfer roller. Can be done. Further, by starting the application of a predetermined voltage to the transfer unit at the same time as the start of application of the preliminary transfer voltage by the voltage application unit, it is possible to more reliably prevent the transfer current due to the transfer voltage from leaking from the recording sheet to the transfer unit.

Further, in the image forming apparatus according to one aspect of the present invention, the voltage application unit applies a first voltage and a second voltage having an absolute value larger than the first voltage stepwise to the transport unit as predetermined voltages. Is preferable.

According to the image forming apparatus having the above configuration, the potential difference between the transfer roller and the transfer unit is obtained by stepwise applying the voltage to the transfer unit in accordance with the application of the preliminary transfer voltage and the transfer voltage to the transfer roller. Can be effectively reduced to satisfactorily suppress the generation of leak current.

Further, the image forming apparatus according to one aspect of the present invention further includes a current control circuit that controls the current supplied to the transfer roller to be constant. The voltage application unit preferably has a voltage control circuit that controls the voltage supplied to the transport unit to be constant.

According to the image forming apparatus having the above configuration, the transfer voltage applied to the transfer roller can be kept satisfactorily constant by controlling the current supplied to the transfer roller by the current control circuit so as to be constant. .. Further, since the voltage application unit has a voltage control circuit that controls the voltage supplied to the transport unit to be constant, the voltage application unit can stably apply a predetermined voltage to the transport unit and generate a leak current. It can be reliably prevented.

According to one aspect of the present invention, the generation of a leak current can be reliably prevented, and transfer defects can be reliably prevented.

It is the schematic which shows an example of the image forming apparatus which concerns on Embodiment 1 of this invention. It is the schematic which shows the internal structure of the image forming apparatus which concerns on Embodiment 1. FIG. It is a block diagram of the image forming apparatus which concerns on Embodiment 1. FIG. It is a flowchart which shows the flow of the printing operation of the image forming apparatus which concerns on Embodiment 1. It is a timing chart which shows the timing of voltage application to the transport part of the image forming apparatus which concerns on Embodiment 1. It is a table which shows the relationship between the target voltage of a voltage control circuit and the applied voltage of a voltage application part. It is a block diagram of the image forming apparatus which concerns on Embodiment 2 of this invention. It is a flowchart which shows the flow of the printing operation of the image forming apparatus which concerns on Embodiment 2. It is a timing chart which shows the timing of voltage application to the transport part which concerns on Embodiment 2. It is a flowchart which shows the flow of the printing operation of the image forming apparatus which concerns on the modification 1 of Embodiment 1 of this invention. It is a timing chart which shows the timing of voltage application to the transport part of the image forming apparatus which concerns on modification 1. FIG.

[Embodiment 1]
Hereinafter, the image forming apparatus according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 6.
[Outline configuration of image forming apparatus]
FIG. 1 is a schematic view showing an example of the image forming apparatus 1 according to the first embodiment. The image forming apparatus 1 is, for example, a color printer, and as shown in FIG. 1, includes a housing 10, an operation panel 10a provided on the upper surface of the housing 10, a discharge tray 10b, and a discharge port 10c. There is. The operation panel 10a has a display unit, an operation unit, and the like. The image forming apparatus 1 is not limited to a color printer, and may be, for example, a monochrome printer.

By operating the operation panel 10a, the user can form a desired color image or monochrome image on one side or both sides of the recording sheet P and print the image. The printed recording sheet P is discharged to the discharge tray 10b through the discharge port 10c.

[Internal configuration of image forming apparatus]
Next, the internal configuration of the image forming apparatus 1 will be described with reference to FIG. FIG. 2 is a schematic view showing the internal configuration of the image forming apparatus 1. Inside the housing 10 of the image forming apparatus 1, as shown in FIG. 2, a tray 11 for accommodating the recording sheet P, an ascending plate 21, transfer rollers 22, 23, 24, transfer rollers 32Y, 32M, 32C, 32K, photoconductor drums 33Y, 33M, 33C, 33K, an exposure device 34, a fixing unit 35, an discharge sensor 6, a temperature sensor 7, a humidity sensor 8, and a paper feed motor 9 are provided. ing.

The tray 11 is a box-shaped member having an open upper surface, and can accommodate a predetermined amount of recording sheets P. The tray 11 is slidably arranged in the left-right direction of FIG. 2 so that the user can manually open and close the tray 11. When the recording sheet P in the tray 11 is exhausted, the operation panel 10a is displayed to urge the user to replenish the recording sheet P. Further, the size and number of trays 11 can be changed as appropriate.

(Transport section)
As shown in FIG. 2, the transport unit 2 is a member arranged upstream of the transfer position W in the transport direction of the recording sheet P and for transporting the recording sheet P housed in the tray 11 to the transfer position W. is there. The transport unit 2 includes a riser plate 21 and transport rollers 22, 23, and 24.

The rising plate 21 is, for example, a rectangular plate-shaped metal member, and is arranged in contact with the bottom surface of the tray 11. The rising plate 21 can rotate by a predetermined range about the rotation fulcrum 21a. The ascending plate 21 can ascend to the transfer start position X, which is a position where the recording sheet P housed in the tray 11 can be fed to the transfer roller 22. Specifically, the ascending plate 21 is connected to the paper feed motor 9 via the paper feed clutch 4, and rises to the transfer start position X by switching the on / off state of the paper feed clutch 4. In the first embodiment, the voltage applying unit 5 for applying a predetermined voltage is electrically connected to the rising plate 21.

The transfer rollers 22, 23, and 24 are arranged upstream of the transfer position W and downstream of the tray 11 in the transfer direction of the recording sheet P, and transfer the recording sheet P from the transfer start position X to the transfer position W. It is a transport member for this purpose. The transfer rollers 22, 23, and 24 are connected to the paper feed motor 9, and are rotationally driven by the driving force from the paper feed motor 9. More specifically, the transport roller 22 is a paper feed roller for taking out the recording sheet P in the tray 11 raised to a position where paper can be fed by the raising plate 21 from the tray 11. The transport roller 22 is arranged above the rising plate 21. The transfer roller 22 presses and contacts one of the upper ends of the plurality of recording sheets P housed in the tray 11 with an appropriate pressure to transfer the sheet to the transfer roller 23 side.

Further, the transfer roller 23 is arranged downstream of the transfer roller 22 in the transfer direction of the recording sheet P. The transport roller 23 transports the recording sheet P to the transport roller 24 side. The transfer roller 24 is arranged on the downstream side of the transfer roller 23 in the transfer direction of the recording sheet P. The transport roller 24 functions as a resist roller for transporting the recording sheet P toward the transfer position W at a predetermined timing after temporarily stopping the movement of the tip of the transported recording sheet P.

(Transfer part)
At the transfer position W, a transport belt V wound around a pair of belt rollers 30 is provided. One of the pair of belt rollers 30 rotates by transmitting a driving force from a driving motor (not shown). The transport belt V is circulated and driven by the rotation of the pair of belt rollers 30. The transport belt V transports the recording sheet P in the horizontal direction from the left side to the right side in FIG. 2 at the transfer position W. The transport belt V is made of a resin material such as polycarbonate. The width of the transport belt V is equal to or larger than the maximum size of the recording sheet P, for example, the width of the A4 size.

Further, at the transfer position W, four photoconductor drums 33Y, 33M corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K) are arranged in order from the upstream side in the transport direction. 33C and 33K are arranged. The photoconductor drums 33Y, 33M, 33C, and 33K are rotationally driven by a driving force from a driving motor (not shown). The arrangement order of the photoconductor drums 33Y, 33M, 33C, and 33K is not limited to this, and can be changed as appropriate.

The surfaces of the photoconductor drums 33Y, 33M, 33C, and 33K are uniformly charged by a charger (not shown). Exposure is performed by irradiating the photoconductor drums 33Y, 33M, 33C, and 33K with light from an exposure device 34, which will be described later, corresponding to each color. By being exposed by the exposure device 34, an electrostatic latent image of the image data printed on the recording sheet P is formed on the surfaces of the photoconductor drums 33Y, 33M, 33C, and 33K. Then, the toner contained in the toner cartridge (not shown) is supplied to the photoconductor drums 33M, 33C, 33K via a developing device (not shown), whereby the photoconductor drums 33Y, 33M, 33C, The electrostatic latent image formed on the surface of 33K becomes a toner image (developer image).

The four exposure devices 34 are provided at positions corresponding to the four photoconductor drums 33Y, 33M, 33C, and 33K described above. The four exposure devices 34 expose the photoconductor drums 33Y, 33M, 33C, and 33K by irradiating them with light. As the four exposure devices 34, for example, an LED exposure head can be adopted. An electrostatic latent image of image data to be formed on the recording sheet P by the exposure device 34 is formed on the surfaces of the photoconductor drums 33Y, 33M, 33C, and 33K.

Then, by supplying toner to each photoconductor drum 33 via a developing device (not shown), an electrostatic agent image formed on the surface of each photoconductor drum 33Y, 33M, 33C, 33K is a toner image. It becomes. In color printing, toner images are formed on the four photoconductor drums 33Y, 33M, 33C, and 33K, respectively. On the other hand, in monochrome printing, a toner image is formed only on the photoconductor drum 33K.

Further, at the transfer position W, four transfer rollers 32Y, 32M, 32C, 32K are arranged at positions facing the four photoconductor drums 33Y, 33M, 33C, 33K. The transfer voltage of the negative electrode is applied to these four transfer rollers 32Y, 32M, 32C, and 32K by the transfer voltage application unit 3. Further, the transfer rollers 32Y, 32M, 32C, and 32K are rotationally driven by a driving force from a driving motor (not shown). The recording sheet P is conveyed while being sandwiched between the transfer rollers 32Y, 32M, 32C, 32K to which the transfer voltage is applied and the photoconductor drums 33Y, 33M, 33C, 33K. As a result, the toner images formed on the surfaces of the photoconductor drums 33Y, 33M, 33C, and 33K are transferred to the recording sheet P.

In the case of a color printer as in the first embodiment, the transfer nip is located in the area where the recording sheet P is sandwiched by the photoconductor drums 33Y, 33M, 33C, 33K and the transfer rollers 32Y, 32M, 32C, 32K, respectively. It is formed. In the following, unless otherwise specified, the position of the most upstream transfer nip in the transport direction of the recording sheet P among the transfer nips will be simply referred to as “transfer position W”.

The transfer voltage application unit 3 applies a predetermined transfer voltage to the transfer rollers 32Y, 32M, 32C, and 32K. In the first embodiment, as shown in FIG. 5, the transfer voltage application unit 3 applies a transfer voltage having an absolute value larger than the preliminary transfer voltage after applying the preliminary transfer voltage. The transfer voltage application unit 3 has a current control circuit 31. By performing PWM (Pulse Width Modulation) control, the current control circuit 31 performs feedback control so that the transfer current supplied from the transfer voltage application unit 3 to the transfer rollers 32Y, 32M, 32C, and 32K becomes a target value. Do.

The fixing portion 35 has a heating roller 35a and a pressing roller 35b. The heating roller 35a is rotationally driven by a driving force from a driving motor (not shown), and is heated by being supplied with electric power from a power source (not shown). The pressing roller 35b is arranged to face the heating roller 35a. The fixing unit 35 applies a pressing force between the heating roller 35a and the pressing roller 35b to the conveyed recording sheet P, and heats the conveyed recording sheet P by the heating roller 35a to fix the toner image on the recording sheet P. ..

(Control unit and various sensors)
As shown in FIG. 3, the control unit 50 performs general control on each unit of the image forming apparatus 1. The control unit 50 includes a CPU (Central Processing Unit) 50a, a ROM (Read Only Memory) 50b, a RAM (Random Access Memory) 50c, and the like. The ROM 50b stores various control programs, various settings, and the like for controlling the image forming apparatus 1. The RAM 50c is used as a work area for reading various control programs and a storage area for temporarily storing image data.

The control unit 50 is electrically connected to the transfer voltage application unit 3, the paper feed clutch 4, the voltage application unit 5, and the paper feed motor 9. Further, the control unit 50 is electrically connected to the operation panel 10a, a network interface (not shown), and the like. The network interface is connected to a network such as a LAN, and enables connection with an external device in which a driver for the image forming apparatus 1 is incorporated. The image forming apparatus 1 can receive a print job via the network interface.

Further, the control unit 50 is electrically connected to the discharge sensor 6, the temperature sensor 7, and the humidity sensor 8, and the detection signals from the sensors 6, 7, and 8 are input. The control unit 50 controls each unit of the image forming apparatus 1 based on the control program read from the ROM 50b and the detection signals output from the sensors 6, 7, and 8.

As shown in FIG. 2, the discharge sensor 6 is provided on the upstream side in the transport direction with respect to the discharge port 10c and on the downstream side in the transport direction with respect to the fixing portion 35, and the recording sheet P is on the downstream side in the transport direction with respect to the fixing portion 35. It is a sensor that detects that it has passed a predetermined position Z. As the discharge sensor 6, a sensor having an actuator that swings when the recording sheet P comes into contact with the recording sheet P, an optical sensor, or the like can be used. The discharge sensor 6 is turned on when the recording sheet P has passed the predetermined position Z, and is turned off when the recording sheet P is not at the predetermined position Z. The detection signal by the discharge sensor 6 is output to the control unit 50.

Further, the temperature sensor 7 is, for example, a sensor provided in the upper part of the housing 10 (upper left side in FIG. 2) to detect the temperature inside the housing 10. The temperature sensor 7 outputs a temperature signal corresponding to the detected temperature to the control unit 50.

Further, the humidity sensor 8 is, for example, a sensor provided in the upper part of the housing 10 (upper left side in FIG. 2) to detect the humidity in the housing 10. The humidity sensor 8 outputs a humidity signal corresponding to the detected humidity to the control unit 50.

(Voltage application part)
The image forming apparatus 1 according to the first embodiment is provided with a voltage applying unit 5 for applying a predetermined voltage having the same polarity as the transfer voltage to the rising plate 21. The voltage application unit 5 is a high-voltage substrate in which a voltage control circuit 51 that generates a high voltage is patterned. The voltage control circuit 51 is a circuit that generates a high voltage of, for example, about 2000 V, and performs feedback control so that the voltage supplied to the riser plate 21 becomes constant.

In the first embodiment, the voltage application unit 5 applies a voltage having the same polarity as the transfer voltage to the metal rising plate 21 having high conductivity, thereby applying the voltage to the transfer rollers 32Y, 32M, 32C, 32K. It prevents a part of the transfer current due to the transfer voltage from flowing as a leak current to the rising plate 21 side via the recording sheet P.

Although the voltage application unit 5 will be described in detail later, before the tip of the recording sheet P reaches the transfer position W, the voltage application unit 5 starts applying the predetermined voltage to the rising plate 21, and the rear end of the recording sheet P provides the transport unit 2. After passing through, that is, after passing through the transport end position Y, the predetermined voltage is applied and finished. As shown in FIG. 5, in the first embodiment, the voltage application unit 5 stepwise raises the first voltage and the second voltage having an absolute value larger than the first voltage as the predetermined voltage. Apply to 21.

[Flow of printing operation]
Next, the flow of the printing operation of the image forming apparatus 1 in the first embodiment will be described with reference to FIGS. 4 to 6. FIG. 4 is a flowchart showing the flow of the printing operation of the image forming apparatus 1. The flowchart shown in FIG. 4 is an example, and the present invention is not limited to this. FIG. 5 is a timing chart showing the timing of voltage application to the rising plate 21.

For example, when the user executes printing by operating the operation panel 10a, the control unit 50 receives the print job (S1). The control unit 50 activates the paper feed motor 9 based on receiving the print job signal (S2).

When the paper feed motor 9 is started, the driving force of the paper feed motor 9 is transmitted to the transfer rollers 22, 23, 24. At this time, the paper feed clutch 4 executes an off operation in which the driving force of the paper feed motor 9 is not transmitted to the riser plate 21. As the paper feed clutch 4, for example, an electromagnetic clutch can be used.

Subsequently, the control unit 50 determines whether the temperature in the image forming apparatus 1 is equal to or higher than a predetermined value and the humidity is equal to or higher than a predetermined value (S3). Specifically, in the control unit 50, the temperature detected by the temperature sensor 7 is equal to or higher than a predetermined value (for example, about 30 ° C.), and the humidity detected by the humidity sensor 8 is a predetermined value (for example, 60%). Degree) or more is judged. This takes into consideration that a leak current from the recording sheet P to the transport unit 2 is likely to occur when the temperature and humidity are high.

When the temperature in the image forming apparatus 1 is equal to or higher than the predetermined value and the humidity is equal to or higher than the predetermined value (S3: YES), the control unit 50 starts applying a predetermined voltage to the rising plate 21 before the rising plate 21 rises. (S4). Specifically, the control unit 50 is at a timing (time t _{S in} FIG. 5) earlier by time T1 (for example, 200 [ms]) than the time when the paper feed clutch 4 is activated (time t _{2 in} FIG. 5). By outputting the control signal to the voltage applying unit 5, the first voltage is started to be applied to the rising plate 21.

FIG. 6 is a table showing the relationship between the target voltage of the voltage control circuit 51 and the voltage applied to the rising plate 21. In this case, the voltage control circuit 51 sets the voltage detected by the voltage control circuit 51 to a target value of 0.355 [V] based on the relationship shown in FIG. 6, and the first voltage control circuit 51 is applied to the riser plate 21. Feedback control is performed so that the voltage becomes, for example, about 1000 [V]. The value of the first voltage is an example and is not limited to this.

As described above, in the image forming apparatus 1 of the first embodiment, the voltage applying unit 5 applies a predetermined voltage to the rising plate 21 before the rising plate 21 starts transporting the recording sheet P, whereby the recording sheet P is applied. It is possible to prevent the transfer current due to the transfer voltage applied to the above from leaking through the rising plate 21.

The control unit 50 starts transporting the recording sheet P when the temperature in the image forming apparatus 1 is not equal to or higher than a predetermined value (S3: NO) and after the processing of S4 (S5). Specifically, the control unit 50 causes the paper feed clutch 4 to perform an on operation (time t _{2 in} FIG. 5), and controls so as to transmit the driving force of the paper feed motor 9 to the riser plate 21. As a result, the ascending plate 21 starts ascending while rotating around the rotation fulcrum 21a, and reaches the conveying start position X where the recording sheet P housed in the tray 11 can be fed to the conveying roller 22. Stop after climbing.

Subsequently, the recording sheet P is conveyed to the transfer position W (S6). Specifically, one recording sheet P at the upper end of the tray raised to the transport start position X is taken out from the tray 11 by the transport roller 22 and transported to the transport roller 23 side. The recording sheet P transported to the transport roller 23 is temporarily stopped by the transport roller 24 and then transported to the transfer position W.

Next, printing on the recording sheet P transported to the transfer position W is started (S7). Specifically, the recording sheet P transported to the transfer position W is sandwiched between the transfer roller 32Y and the photoconductor drum 33Y and transported. After that, the toner images formed on the surfaces of the photoconductor drums 33Y, 33M, 33C, 33K by sandwiching and transporting the transfer rollers 32M, 32C, 32K and the photoconductor drums 33M, 33C, 33K. Is transferred to a predetermined location on the recording sheet P. The recording sheet P on which the toner image is transferred is conveyed while being sandwiched between the heating roller 35a and the pressing roller 35b of the fixing portion 35, and is heated and pressed to fix the toner image on the recording sheet P.

In the first embodiment, as shown in FIG. 5, the voltage application unit 5 applies a second voltage having an absolute value larger than the first voltage to the rising plate 21 at the start of transfer (time t _{3 in} FIG. 5). Start applying. In this case, the voltage control circuit 51 sets the target voltage to 0.711 [V] and sets the second voltage applied to the riser plate 21 to, for example, 2000 [V] based on the relationship shown in FIG. Then, the voltage control circuit 51 performs feedback control so that the voltage in the voltage control circuit 51 becomes a target value. The value of the second voltage is an example and is not limited to this.

Subsequently, the control unit 50, simultaneously with the discharge sensor 6 is turned on (time t _e of FIG. _5), a predetermined voltage is applied ends to increase plate 21 (S8). As a result, it is possible to suppress the power consumption applied from the voltage applying unit 5 to the rising plate 21.

Then, the recording sheet P on which the toner image is formed passes through the ejection sensor 6 and is ejected to the ejection port 10c via the paper ejection roller 36, so that printing on the recording sheet P is completed (S9). Here, if the print job executes printing of one sheet, the printing operation of the image forming apparatus 1 is completed in S9. On the other hand, when a print job for executing printing of a plurality of sheets is received, printing of the second and subsequent sheets is continuously performed after printing of the first recording sheet P is completed. In this case, the processes S2 to S8 may be repeatedly executed until the printing of the last one recording sheet P is completed, or the process is continued until the last one recording sheet P passes through the ejection sensor 6. A voltage may be applied to the rising plate 21.

When double-sided printing is performed by the image forming apparatus 1, the recording sheet P on which a desired image is formed on one surface is conveyed to the paper ejection roller 36 via the conveying path R1. After the rear end of the recording sheet P has passed the branch point U1, the paper ejection roller 36 temporarily stops in a state of sandwiching the recording sheet P. After that, the rotation direction of the paper ejection roller 36 is switched, the conveying direction of the recording sheet P is reversed, and the recording sheet P is conveyed to the re-conveying path R2. Then, the recording sheet P is returned to the transport path R1 at the confluence point U2 of the transport path R1. As a result, the front and back sides of the recording sheet P are reversed, and printing is performed on the other side.

In the image forming apparatus 1 according to the first embodiment described above, the voltage applying unit 5 starts applying a predetermined voltage having the same polarity as the transfer voltage to the rising plate 21 before the tip of the recording sheet P reaches the transfer position W. Will be done. Specifically, the voltage applying unit 5 starts applying a predetermined voltage to the rising plate 21 before the rising plate 21 raises the recording sheet P to the transport start position X (S4), and the rear end of the recording sheet P. After passing through the rising plate 21 and the transport rollers 22, 23, 24, the application of the predetermined voltage is completed. As a result, a predetermined voltage is applied to the ascending plate 21 from immediately after the start of transfer of the recording sheet P until the recording sheet P finishes passing through the conveying unit 2, so that the leakage from the recording sheet P to the ascending plate 21 The generation of electric current can be prevented, and transfer defects such as white spots can be reliably prevented.

Further, in the image forming apparatus 1 having the above-described configuration, the voltage applying unit 5 ends the voltage application to the rising plate 21 after the rear end of the recording sheet P is discharged from the tray 11 by the transport rollers 31 and 32. Specifically, when the discharge sensor 6 detects that the recording sheet P has passed a predetermined position Z (see FIG. 2) on the downstream side in the transport direction from the fixing portion 35, a predetermined voltage is applied to the rising plate 21. Finish (S8). As a result, it is possible to suppress the application of unnecessary voltage to the rising plate 21.

Further, according to the image forming apparatus 1 having the above configuration, the current control circuit 31 controls the currents supplied to the transfer rollers 32Y, 32M, 32C, 32K so as to be constant, so that the transfer rollers 32Y, 32M, The transfer voltage applied to 32C and 32K can be kept satisfactorily constant. Further, since the voltage application unit 5 has a voltage control circuit 51 that controls the voltage supplied to the riser plate 21 so as to be constant, the voltage application unit 5 can stably apply a predetermined voltage to the riser plate 21. The generation of leak current can be reliably prevented.

[Embodiment 2]
Next, the image forming apparatus according to the second embodiment of the present invention will be described with reference to FIGS. 7 to 9. For convenience of explanation, the same reference numerals will be added to the members having the same functions as the members described in the first embodiment, and the description will not be repeated.

(Voltage application part)
In the image forming apparatus 1 of the second embodiment, the voltage application unit 5 applies a predetermined voltage having the same polarity as the transfer voltage to the transfer roller 23. As shown in FIG. 7, the voltage application unit 5 has a voltage control circuit 51. The voltage application unit 5 is a high-voltage substrate in which a voltage control circuit 51 that generates a high voltage is patterned. The voltage control circuit 51 is a circuit that generates a high voltage of, for example, about 2000 V, and performs feedback control so that the voltage supplied to the transfer roller 23 becomes constant.

[Flow of printing operation]
FIG. 8 is a flowchart showing the flow of the printing operation of the image forming apparatus 1 in the second embodiment. The flowchart shown in FIG. 8 is an example, and the present invention is not limited to this. FIG. 9 is a timing chart showing the timing of voltage application to the transfer roller 23 in the second embodiment.

When the control unit 50 receives the print job (S11), the control unit 50 activates the paper feed motor 9 (S2). When the paper feed motor 9 is started, the transfer rollers 22, 23, 24 are driven. At this time, the paper feed clutch 4 executes an off operation in which the driving force of the paper feed motor 9 is not transmitted to the riser plate 21.

Subsequently, the control unit 50 determines whether the temperature in the image forming apparatus 1 is equal to or higher than a predetermined value and the humidity is equal to or higher than a predetermined value (S13). Specifically, in the control unit 50, the temperature detected by the temperature sensor 7 is equal to or higher than a predetermined value (for example, about 30 ° C.), and the humidity detected by the humidity sensor 8 is a predetermined value (for example, 60%). Degree) or more is judged.

When the temperature in the image forming apparatus 1 is equal to or higher than a predetermined value and the humidity is equal to or higher than a predetermined value (S13: YES), the control unit 50 before starting the transfer of the recording sheet P by the transfer rollers 22, 23, 24. , A predetermined voltage is started to be applied to the transfer roller 23 (S14). Specifically, the control unit 50 conveys the paper at a timing (time t _{S in} FIG. 9) earlier than the time when the paper feed clutch 4 starts to start (time t _{2 in} FIG. 9) by time T1 (for example, 200 ms). The first voltage is applied to the roller 23. Based on the relationship shown in FIG. 6, the voltage control circuit 51 sets the target voltage to 0.355 [V], and sets the first voltage applied to the transport roller 23 to, for example, 1000 [V]. Then, the voltage control circuit 51 performs feedback control so that the voltage in the voltage control circuit 51 becomes a target value.

As described above, in the second embodiment, the voltage application unit 5 applies the first voltage having the same polarity as the transfer voltage to the transfer roller 23, so that the transfer is performed by the transfer voltage applied to the transfer rollers 32Y, 32M, 32C, 32K. It prevents a part of the current from flowing from the recording sheet P to the transport roller 23 as a leak current.

The control unit 50 starts transporting the recording sheet P when the temperature in the image forming apparatus 1 is not equal to or higher than a predetermined value (S13: NO) and after the processing of S14 (S15). Specifically, the control unit 50 causes the paper feed clutch 4 to perform an on operation (time t _{2 in} FIG. 9), and controls so as to transmit the driving force of the paper feed motor 9 to the riser plate 21. As a result, the ascending plate 21 starts ascending, and the recording sheet P housed in the tray 11 rises to the conveying start position X where the paper is fed by the conveying roller 22 and stops.

Subsequently, the recording sheet P transported to the transport start position X is transported to the transfer position W (S16). Specifically, one of the upper ends of the recording sheet P housed in the tray 11 is taken out from the transport roller 22 and transported to the transport roller 23 side. The recording sheet P transported to the transport roller 23 is temporarily stopped by the transport roller 24 and then transported to the transfer position W.

Next, printing on the recording sheet P transported to the transfer position W is started (S17). Specifically, the recording sheet P transported to the transfer position W is sandwiched between the transfer roller 32Y and the photoconductor drum 33Y and transported. After that, the toner images formed on the surfaces of the photoconductor drums 33Y, 33M, 33C, 33K by sandwiching and transporting the transfer rollers 32M, 32C, 32K and the photoconductor drums 33M, 33C, 33K. Is transferred to a predetermined location on the recording sheet P. The recording sheet P on which the toner image is transferred is conveyed while being sandwiched between the heating roller 35a and the pressing roller 35b of the fixing portion 35, so that the toner image is fixed on the recording sheet P by heating and pressing pressure. ..

In the second embodiment, the voltage application unit 5 starts applying a second voltage having an absolute value larger than the first voltage to the transfer roller 23 at the start of transfer (time t _{3 in} FIG. 9). Similar to the first embodiment, the voltage control circuit 51 sets the target voltage detected by the voltage control circuit 51 to 0.711 [V] based on the relationship shown in FIG. 6 and applies it to the transfer roller 23. The second voltage to be generated is, for example, 2000 [V]. Then, the voltage control circuit 51 performs feedback control so that the voltage in the voltage control circuit 51 becomes a target value.

Subsequently, the control unit 50 outputs a control signal to the voltage application unit 5, simultaneously with the stopping of the feed motor 9 (time t _e of FIG. _9), to apply terminated a predetermined voltage to rise plate 21 (S18) .. As a result, it is possible to suppress the power consumption applied from the voltage applying unit 5 to the rising plate 21.

Then, the recording sheet P on which the toner image is formed passes through the ejection sensor 6 and is ejected to the ejection port 10c via the paper ejection roller 36, so that printing on the recording sheet P is completed (S19).

The same effect as that of the first embodiment can be obtained in the image forming apparatus 1 of the second embodiment described above. That is, according to the image forming apparatus 1 in the second embodiment, the voltage application unit 5 starts applying a predetermined voltage to the transfer roller 23 before the transfer rollers 22, 23, and 24 start the transfer of the recording sheet P. , The generation of a leak current from the recording sheet P to the transfer roller 23 can be reliably prevented, and transfer defects such as white spots can be more reliably prevented.

Further, in the image forming apparatus 1 of the second embodiment, the voltage applying unit 5 ends the voltage application to the transport roller 23 at the same time as the paper feed motor 9 is stopped (S18), so that the power consumption applied to the transport roller 23 is consumed. It is possible to prevent the generation of a leak current to the transport roller 23 while suppressing the above.

[Modification 1]
Next, the image forming apparatus according to the first modification of the first embodiment of the present invention will be described with reference to FIGS. 2, 10 and 11. For convenience of explanation, the same reference numerals will be added to the members having the same functions as the members described in the first embodiment, and the description will not be repeated.

[Flow of printing operation]
In the image forming apparatus 1 in the first modification, the flow of the printing operation by the control unit 50 is different from that of the first embodiment. FIG. 10 is a flowchart showing the flow of the printing operation of the image forming apparatus 1 according to the first modification. FIG. 11 is a timing chart showing the timing of voltage application to the rising plate 21 according to the first modification. In the first modification, the temperature and humidity determination process S3 (see FIG. 4) in the first embodiment is omitted.

As shown in FIG. 10, the control unit 50 activates the paper feed motor 9 (S22) when it receives the print job (S21). When the paper feed motor 9 is started, the driving force of the paper feed motor 9 is transmitted to the transfer rollers 22, 23, 24. At this time, the paper feed clutch 4 executes an off operation in which the driving force of the paper feed motor 9 is not transmitted to the riser plate 21.

Next, as shown in FIG. 11, the control unit 50, the application start and simultaneous pre-transfer voltage (time _{t s} in FIG. 11), the first voltage application start to rise plate 21 (S23). Subsequently, the control unit 50 starts conveying the recording sheet P by controlling the paper feed clutch 4 (S24). Specifically, the control unit 50 causes the paper feed clutch 4 to perform an on operation (time t _{2 in} FIG. 11), and transmits the driving force of the paper feed motor 9 to the riser plate 21. As a result, the ascending plate 21 starts ascending, and the recording sheet P housed in the tray 11 rises to the conveying start position X to be fed to the conveying roller 22, and then stops.

Subsequently, the recording sheet P transported to the transport start position X is transported to the transfer position W (S25). Specifically, the transport roller 22 takes out one of the upper ends of the recording sheet P housed in the tray 11 and transports it to the transport roller 23 side. The recording sheet P transported to the transport roller 23 is temporarily stopped by the transport roller 24 and then transported to the transfer position W (see FIG. 2).

Next, printing on the recording sheet P transported to the transfer position W is started (S26). Specifically, the recording sheet P transported to the transfer position W is sandwiched between the transfer roller 32Y and the photoconductor drum 33Y and transported. After that, the toner images formed on the surfaces of the photoconductor drums 33Y, 33M, 33C, 33K by sandwiching and transporting the transfer rollers 32M, 32C, 32K and the photoconductor drums 33M, 33C, 33K. Is transferred to a predetermined location on the recording sheet P. The recording sheet P on which the toner image is transferred is conveyed while being sandwiched between the heating roller 35a and the pressing roller 35b of the fixing portion 35, so that the toner image is fixed on the recording sheet P by heating and pressing pressure. ..

In the first modification, the voltage application unit 5 starts applying the second voltage to the rising plate 21 at the start of transfer (time t _{3 in} FIG. 11). Based on the relationship shown in FIG. 6, the voltage control circuit 51 sets the target voltage to 0.711 [V], and sets the second voltage applied to the rising plate 21 to, for example, 2000 [V]. Then, the voltage control circuit 51 performs feedback control so that the voltage detected by the voltage control circuit 51 becomes a target value.

Subsequently, the control unit 50, the stop and simultaneous feed motor 9 (time _{t e} of FIG. 11), a predetermined voltage is applied ends to increase plate 21 (S27). As a result, it is possible to suppress the power consumption applied from the voltage applying unit 5 to the rising plate 21. Then, the recording sheet P on which the toner image is formed passes through the ejection sensor 6 and is ejected to the ejection port 10c via the paper ejection roller 36, so that printing on the recording sheet P is completed (S28).

The same effect as that of the first embodiment can be obtained in the image forming apparatus 1 in the modified example 1 described above. That is, according to the image forming apparatus 1 in the first modification, the voltage applying unit 5 applies a predetermined voltage having the same polarity as the transfer voltage to the rising plate 21 before the rising plate 21 starts transporting the recording sheet P. Is started, and after the rear end of the recording sheet P has passed through the rising plate 21, the application of the predetermined voltage is completed. As a result, a predetermined voltage (for example, 2000 [V]) is applied to the ascending plate 21 from immediately after the start of transfer of the recording sheet P until the recording sheet P finishes passing through the conveying unit 2. It is possible to prevent the transfer current from leaking from P to the rising plate 21. As a result, transfer defects on the recording sheet P can be reliably prevented.

In particular, according to the image forming apparatus 1 in the modification 1, the temperature and humidity determination processing S3 (see FIG. 4) in the image forming apparatus 1 is not executed, so that the temperature detected by the temperature sensor 7 is less than a predetermined value. Alternatively, even if the humidity detected by the humidity sensor 8 is less than a predetermined value, the voltage applying unit 5 applies a predetermined voltage to the rising plate 21. Therefore, it is possible to prevent the generation of a leak current from the recording sheet P to the rising plate 21 regardless of the temperature and humidity in the image forming apparatus 1.

According to the image forming apparatus 1 in the above-described modification 1, the voltage application unit 5 ends the voltage application to the riser plate 21 at the same time as the paper feed motor 9 is stopped (S27), so that the voltage is applied to the riser plate 21. It is possible to prevent the generation of a leak current to the rising plate 21 while suppressing power consumption.

Further, according to the image forming apparatus 1 in the above-described modification 1, the preliminary transfer voltage having an absolute value smaller than the transfer voltage is applied before the transfer voltage is applied to the transfer rollers 32Y, 32M, 32C, 32K. Therefore, the transfer voltage can be satisfactorily applied to the transfer rollers 32Y, 32M, 32C, and 32K, and the transfer to the recording sheet P can be satisfactorily performed. Further, the voltage application unit 5 starts applying a predetermined voltage to the riser plate 21 at the same time as the start of applying the preliminary transfer voltage, thereby reliably preventing the transfer current due to the transfer voltage from leaking from the recording sheet P to the riser plate 21. it can.

Further, by gradually applying the voltage to the riser plate 21 in correspondence with the application of the preliminary transfer voltage and the transfer voltage to the transfer rollers 32Y, 32M, 32C, 32K, the transfer rollers 32Y, 32M, 32C, 32K The potential difference between the and the rising plate 21 can be effectively reduced, and the generation of leak current can be satisfactorily suppressed.

[Other Embodiments]
The image forming apparatus 1 described above is said to be a color printer or a monochrome printer, but the present invention is not limited to this, and any other apparatus having a printing function, such as a multifunction device or a FAX apparatus, can be applied. Further, it may be a device for exclusively printing a color image or a monochrome image.

Further, in the above-described embodiment, a predetermined voltage is applied from the voltage application unit 5 to either the raising plate 21 or the transfer roller 23, but a predetermined voltage is applied to the transfer rollers 22 and 24 from the voltage application unit 5. A voltage may be applied to another member provided between the transfer start position X and the transfer position W.

Further, in the above-described embodiment, the voltage application unit 5 gradually applies the first voltage and the second voltage as predetermined voltages to either the rising plate 21 or the transport roller 23. It is not limited, and for example, only the second voltage may be applied.

Further, in the above-described embodiment, the recording sheet P is transported by the transport belt V at the transfer position W, but the present invention is not limited to this configuration. For example, the transfer belt V may not be provided, and the recording sheet P may be conveyed using a plurality of rollers including transfer rollers 32Y, 32M, 32C, and 32K.

Further, in the above-described embodiment, a predetermined voltage is applied from the voltage application unit 5 to either the raising plate 21 or the transfer roller 23, but the transfer rollers 22 and 24 are also specified by the voltage application unit 5. A voltage may be applied, or a voltage may be applied to another member provided between the transfer start position X and the transfer position W.

[Example of realization by software]
The control unit 50 of the image forming apparatus 1 may be realized by a logic circuit (hardware) formed in an integrated circuit (IC chip) or the like, or may be realized by software.

In the latter case, the image forming apparatus 1 includes a computer that executes instructions of a program that is software that realizes each function. The computer includes, for example, one or more processors and a computer-readable recording medium that stores the program. Then, in the computer, the processor reads the program from the recording medium and executes it, thereby achieving the object of the present invention. As the processor, for example, a CPU (Central Processing Unit) can be used. As the recording medium, in addition to a “non-temporary tangible medium” such as a ROM (Read Only Memory), a tape, a disk, a card, a semiconductor memory, a programmable logic circuit, or the like can be used. Further, a RAM (Random Access Memory) for expanding the above program may be further provided. Further, the program may be supplied to the computer via an arbitrary transmission medium (communication network, broadcast wave, etc.) capable of transmitting the program. It should be noted that one aspect of the present invention can also be realized in the form of a data signal embedded in a carrier wave, in which the above program is embodied by electronic transmission.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the present invention can be obtained by appropriately combining the technical means disclosed in the different embodiments. The form is also included in the technical scope of the present invention.

1 Image forming device 2 Conveying unit 21 Raising plate (conveying unit)
22, 23, 24 Conveying rollers (conveying section)
3 Transfer voltage application unit 31 Current control circuit 32Y, 32M, 32C, 32K Transfer roller 33Y, 33M, 33C, 33K Photoreceptor drum 34 Exposed device 35 Fixing unit 5 Voltage application unit 50 Control unit 51 Voltage control circuit 6 Emission sensor (sensor) )
9 Paper feed motor 10c Discharge port X Transfer start position W Transfer position Z Predetermined position

Claims (10)

A tray for storing recording sheets and
Photoreceptor drum and
The recording sheet is sandwiched and conveyed between the photoconductor drum and the photoconductor drum at the transfer position, and the developer image formed on the surface of the photoconductor drum is transferred to the recording sheet by applying a transfer voltage. Transfer roller and
A transport unit located upstream of the transfer position in the transport direction of the recording sheet and transporting the recording sheet contained in the tray to the transfer position.
The transport unit is provided with a voltage application unit that applies a predetermined voltage having the same polarity as the transfer voltage.
The voltage application unit is
Before the tip of the recording sheet reaches the transfer position, a predetermined voltage having the same polarity as the transfer voltage is started to be applied to the transfer portion, and after the rear end of the recording sheet passes through the transfer portion, the predetermined voltage is applied. An image forming apparatus, characterized in that the application is completed. The image forming apparatus according to claim 1, wherein the voltage application unit starts applying the predetermined voltage to the transfer unit before the transfer unit starts the transfer of the recording sheet. The transport unit
A transport roller that is arranged upstream of the transfer position and downstream of the tray in the transport direction and transports the recording sheet from the transport start position to the transfer position.
It has a rising plate that raises the recording sheet housed in the tray to the transport start position.
The image forming apparatus according to claim 1 or 2, wherein the voltage applying unit applies the predetermined voltage to either one of the transport roller and the rising plate. The image forming apparatus according to claim 3, wherein the voltage applying unit starts applying the predetermined voltage to the rising plate before the rising plate raises the recording sheet to the transport start position. The image forming apparatus according to claim 4, wherein the voltage applying unit finishes applying the predetermined voltage after the rear end of the recording sheet is discharged from the tray by the transport roller. A paper feed motor for driving the transport unit is provided.
The image forming apparatus according to any one of claims 1 to 5, wherein the voltage applying unit finishes applying the predetermined voltage at the same time as stopping the paper feeding motor. An outlet for discharging the recording sheet and
A fixing portion for fixing the developer image transferred to the recording sheet,
A sensor provided on the upstream side in the transport direction from the discharge port and on the downstream side in the transport direction from the fixing portion, and detecting that the recording sheet has passed a predetermined position on the downstream side in the transport direction from the fixing portion.
With
The method according to any one of claims 1 to 6, wherein the voltage applying unit ends applying the predetermined voltage when the sensor detects that the recording sheet has passed the predetermined position. Image forming device. Before the transfer voltage is applied to the transfer roller, a preliminary transfer voltage having an absolute value smaller than the transfer voltage is applied to the transfer roller.
The image forming apparatus according to claim 1, wherein the voltage application unit starts applying the predetermined voltage at the same time as the application of the preliminary transfer voltage is started. The eighth aspect of the present invention, wherein the voltage application unit gradually applies a first voltage and a second voltage having an absolute value larger than the first voltage to the transport unit as the predetermined voltage. Image forming device. Further, a current control circuit for controlling the current supplied to the transfer roller to be constant is provided.
The image forming apparatus according to any one of claims 1 to 9, wherein the voltage applying unit includes a voltage control circuit that controls the voltage supplied to the transport unit to be constant.

Images