JP2012233974A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device that maintains excellent toner recovery performance and enables favorable transfer even in borderless image formation.SOLUTION: The image forming device 1 includes: a photoreceptor on which an electrostatic latent image is formed; exposure means for forming an electrostatic latent image on the photoreceptor; primary transfer means for transferring a developer image formed on the photoreceptor to an intermediate transfer body; and secondary transfer means for transferring the developer image transferred on the intermediate transfer body to a medium. The image forming device 1 includes borderless image forming means (command/image processing part 102, control part 104) for forming a developer image protruding from the edge of the medium; cleaning means 26 for removing the developer image transferred on the secondary transfer means; and cleaning voltage control means 109 for controlling the cleaning voltage to be applied on the cleaning means according to the position where the cleaning means removes the developer image on the secondary transfer means.

Description

  The present invention relates to an image forming apparatus that forms an image by transferring a developer image formed on an image carrier onto a recording medium.

  Conventionally, in an electrophotographic color image forming apparatus, each toner image formed on each color photoconductor is sequentially transferred (primary transfer) so as to be superimposed on the intermediate transfer body, and then each color on the intermediate transfer body is transferred. The toner image is transferred (secondary transfer) to a batch recording medium by a secondary transfer portion (secondary transfer roller).

  Further, the image forming apparatus is provided with a cleaning unit for removing toner attached to the secondary transfer roller during the secondary transfer. The cleaning unit includes a cleaning roller that applies a cleaning bias to collect the toner attached to the secondary transfer roller, and a cleaning blade that scrapes off the toner attached to the surface of the cleaning roller by collecting the toner.

In such an image forming apparatus, for example, in Japanese Patent Application Laid-Open No. 2003-228620, for forming a toner image, there is an edge-forming image forming processing function for forming a toner image that fits inside the recording medium, and no edge for forming a toner image that protrudes from the recording medium. What has an image formation processing function is disclosed.
In the case of borderless image forming processing in the cleaning after the secondary transfer, the toner that protrudes from the recording medium during the secondary transfer adheres to the secondary transfer roller, so that the adhered toner is reliably recovered. In order to achieve this, a technique for increasing the cleaning bias and improving the toner collecting ability of the cleaning roller as compared with the image forming process with a border is shown.

JP 2004-45457 A

  However, as in Patent Document 1, if a high bias is applied to the secondary transfer roller while the borderless image forming process is being performed, the surface of the secondary transfer roller becomes overcharged and the secondary transfer is performed. This adversely affects the formation of the electric field in the area, and there is a problem in that transfer failure occurs.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of performing good transfer while maintaining excellent toner recovery power even in borderless image forming processing.

  That is, the present invention transfers a photosensitive member on which an electrostatic latent image is formed, an exposure unit that forms an electrostatic latent image on the photosensitive member, and a developer image formed on the photosensitive member to an intermediate transfer member. In an image forming apparatus comprising a primary transfer means and a secondary transfer means for transferring a developer image transferred onto the intermediate transfer member to a medium, an edgeless image for forming a developer image that protrudes from the edge of the medium Forming means; cleaning means for removing the developer image transferred onto the secondary transfer means; and the cleaning means depending on the position on the secondary transfer means where the cleaning means removes the developer image. An image forming apparatus comprising: cleaning voltage control means for controlling the magnitude of the cleaning voltage applied to the image forming apparatus.

  According to the present invention, the cleaning voltage control means increases the cleaning voltage when removing the developer image on the secondary transfer roller transferred from the leading edge and the trailing edge of the medium in the conveyance direction of the medium. Is possible. As a result, even in the borderless image forming process, it is possible to perform a good transfer while maintaining an excellent toner collecting ability.

FIG. 3 is a block diagram illustrating a configuration of a control circuit unit according to the first embodiment. 1 is a configuration diagram illustrating an image forming apparatus of the present invention. It is a figure which shows the relationship between a recording medium and a printing area. It is an enlarged view of a secondary transfer part. It is a time chart which shows the operation | movement at the time of printing with a border. It is a time chart which shows the operation | movement at the time of borderless printing. It is a block diagram which shows the structure of the high voltage | pressure control part by Example 2. FIG. FIG. 6 is a block diagram illustrating a configuration of a cleaning voltage control unit according to a second embodiment. 6 is a flowchart showing the operation of the second embodiment.

Hereinafter, an image forming apparatus according to the present invention will be described with reference to FIGS.
In this embodiment, an electrophotographic color printer will be described as an example of the image forming apparatus.

  First, the configuration of the image forming apparatus 1 (color printer 1) to which the present invention is applied will be described with reference to FIG. FIG. 2 is a block diagram showing the image forming apparatus of the present invention.

As shown in FIG. 2, the color printer 1 includes an image drum unit 2 for forming developer images (toner images) of black (K), yellow (Y), magenta (M), and cyan (C). (Hereinafter referred to as ID unit 2) is detachably mounted.
These ID units 2 have the same configuration for each color.

  The ID unit 2 includes a photosensitive drum 5, a charging roller 6, an LED head (exposure means) 3, a developing roller 8, a supply roller 7, a toner cartridge 4, and a cleaning blade 9, and among these, the charging roller 6 and the developing roller. The roller 8 and the cleaning blade 9 are disposed so as to be in contact with the surface of the photosensitive drum 5.

A negative charging voltage is applied to the charging roller 6 to negatively charge the surface of the photosensitive drum 5.
The LED head 3 is disposed above the photosensitive drum 5 and selectively irradiates light onto the surface of the charged photosensitive drum 5 to form an electrostatic latent image based on image data.

A negative voltage is applied to the developing roller 8, and the electrostatic latent image formed on the surface of the photosensitive drum 5 is developed with toner to form a toner image.
The supply roller 7 supplies toner to the developing roller 8 during development, and negatively frictionally charges the toner by a stirring operation at that time.

The toner cartridge 4 is a container that stores toner to be supplied to the supply roller 7. Each toner cartridge 4 stores toner of each color, and is detachably attached to each ID unit 2.
The cleaning blade 9 scrapes and removes residual toner adhering to the surface of the photosensitive drum 5 after the transfer of the toner image.

  The intermediate transfer belt 11 is an endless belt made of, for example, a high-resistance semiconductive plastic film stretched around three rollers, a driving roller 12, a belt driven roller 13, and a secondary transfer backup roller 14. The upper surface portion is rotatably disposed so as to move between a primary transfer roller (primary transfer means) 10 disposed opposite to each ID unit 2 and the photosensitive drum 5. The intermediate transfer belt 11 is rotated by a driving roller 12 and can be moved.

In addition, a plate-like cleaning blade 15 whose tip is in contact with the intermediate transfer belt 11 is disposed at a side surface of the intermediate transfer belt 11 and facing the belt driven roller 13.
Below the cleaning blade 15, a cleaner container 16 is disposed that stores deposits such as toner scraped off from the intermediate transfer belt 11 by the cleaning blade 15.

  A secondary transfer roller 25 is disposed at a position facing the secondary transfer backup roller 14 so as to contact the surface of the intermediate transfer belt 11. The secondary transfer roller 25 is made of, for example, a conductive rubber material, and its metal shaft is connected (grounded) to the casing.

  A cleaning roller (cleaning means) 26 is disposed in contact with the lower surface of the secondary transfer roller 25, and a plate-like shape that scrapes off toner adhering to the surface of the cleaning roller 26 so as to contact the lower surface of the cleaning roller 26. A cleaning blade 27 is provided. For example, a metal roller is used as the cleaning roller 26.

  Further, below the cleaning blade 27, a cleaner container 28 for collecting the toner scraped off from the cleaning roller 26 by the cleaning blade 15 is disposed.

A recording medium storage cassette 29 on which recording media are loaded is detachably mounted on the bottom of the color printer 1.
Near the recording medium outlet of the recording medium containing cassette 29, a discriminating means (not shown) for feeding the recording media in the cassette one by one to the transport path 31 and a hopping roller 30 are provided.

On the downstream side of the hopping roller 30, a registration roller 17 that conveys the recording medium fed from the recording medium accommodation cassette 29 to a contact portion (nip portion) between the intermediate transfer belt 11 and the secondary transfer roller 25 at a predetermined timing. However, the transport rollers 18 and 19 are disposed in the downstream portion.
A sensor 24 that detects the presence or absence of a recording medium is disposed between the conveyance roller 19 and the secondary transfer roller 25.

A fixing device 20 for fixing the transfer image on the recording medium is disposed downstream of the secondary transfer roller 25. The fixing device 20 includes a heat roller 21 that heats and melts toner on a recording medium with a built-in heater, and a pressure roller 22 that pressurizes and melts the melted toner onto the recording medium. .
A thermistor 23 that detects the temperature of the heat roller 21 is disposed in the vicinity of the surface of the heat roller 21.

  The color printer 1 has a control circuit unit as a control system in addition to the above-described configuration, and forms an image with a margin by forming a margin at the peripheral edge of the recording medium under the control of the control circuit unit. It is possible to execute the processing and the borderless image forming processing for forming an image without providing a margin at the peripheral edge of the recording medium (see FIG. 3).

  Next, the configuration of the control circuit unit will be described with reference to FIG. FIG. 1 is a block diagram illustrating a configuration of a control circuit unit according to the first embodiment.

  As shown in FIG. 1, the control circuit unit includes a host interface unit 101, a command / image processing unit 102, an LED head interface unit 103, a control unit 104, a high voltage control unit 100, and the like.

  The host interface unit 101 is a part that communicates with, for example, a host computer (not shown) as an external device and receives print data (command data, image data, etc.) from the host side. The received data is sent to the command / image processing unit 102. The data transmitted from the host computer is print data expressed in a page description language (PDL).

The command / image processing unit 102 is a part that analyzes and processes the print data received by the host interface unit 101.
That is, the command / image processing unit 102 analyzes the command and the image data, determines whether the received job is a bordered printing process or a borderless printing process, and converts the image data into bitmap data (printing) corresponding to each process. Image data in a possible format) and the bitmap data is sent to the LED head interface unit 103.
Further, the command / image processing unit 102 notifies the control unit 104 of the analysis result (whether the received job is a bordered printing process or a borderless printing process).

  The LED head interface unit 103 is a part that processes the bitmap data sent from the command / image processing unit 102 into data that can be received by the LED head 3 of each color (K, Y, M, C). The processed bitmap data of each color is sent to the corresponding LED head 3.

The control unit 104 is a unit that performs overall control of the mechanism of the color printer 1 and control of the applied voltage based on the analysis result notified from the command / image processing unit 102.
That is, the control unit 104 controls each drive system such as the hopping motor 110, the registration motor 111, the conveyance motor 112, the belt motor 113, the ID motor 114, the fixing device heater motor 115, and the secondary transfer motor 116 at a predetermined timing and speed. Drive control. Further, the control unit 104 controls the temperature of the fixing device heater 117 based on the detection value of the thermistor 23.

Here, the hopping motor 110 rotationally drives the hopping roller 30.
The registration motor 111 rotates the registration roller 17.
The conveyance motor 112 drives the conveyance rollers 18 and 19 to rotate.
The belt motor 113 rotationally drives the belt driving roller 12.
The ID motor 114 rotationally drives a drive system (photosensitive drum 5 or the like) in the ID unit.
The fixing device heater motor 115 rotationally drives the heat roller 21.
The secondary transfer motor 116 drives the secondary transfer roller 25 to rotate.

The high voltage control unit 100 includes a charging voltage control unit 105, a development voltage control unit 106, a primary transfer voltage control unit 107, a secondary transfer voltage control unit 108, and a cleaning voltage control unit 109. Based on an instruction from the control unit 104, This is a part for supplying a predetermined voltage to each roller.
That is, the charging voltage control unit 105 controls the voltage (negative voltage) applied to the charging roller 6.
The development voltage control unit 106 controls the voltage (negative voltage) applied to the development roller 8.
The primary transfer voltage control unit 107 controls the voltage (positive voltage) applied to the primary transfer roller 10.
The secondary transfer voltage control unit 108 controls the voltage (negative voltage) applied to the secondary transfer backup roller 14.
The cleaning voltage control unit 109 controls the voltage (positive voltage) applied to the cleaning roller 26.

  Here, in each component configuration of the control circuit unit described above, an assembly of the command / image processing unit 102 and the control unit 104 corresponds to the borderless image forming unit in the claims.

Next, a series of printing processes by the color printer 1 having the above configuration will be described.
First, when print data created on the host side is transmitted to the printer side, the command / image processing unit 102 receives the print data via the host interface unit 101.

The command / image processing unit 102 analyzes the received data, determines whether the received job is a bordered printing process or a borderless printing process, and develops the image data into bitmap data corresponding to each process.
At the same time, the command / image processing unit 102 notifies the control unit 104 whether the developed bitmap data is for bordered printing processing or borderless printing processing.

  When the control unit 104 receives the notification from the command / image processing unit 102, the control unit 104 rotates the fixing device heater motor 115 and performs ON / OFF control of the energization to the fixing device heater 117 according to the detection value of the thermistor 23. When the temperature of the roller 21 reaches a predetermined temperature, a printing operation described later is started.

  In starting the printing operation, the control unit 104 first drives the belt motor 113, the ID motor 114, and the secondary transfer motor 116 to rotate, and instructs the high-voltage control unit 100 to apply a voltage. The control unit 105 supplies a predetermined negative voltage to the charging roller 6, and the development voltage control unit 106 supplies a predetermined negative voltage to the development roller 8.

When the charging of the photosensitive drum 5 is stabilized, the command / image processing unit 102 sends the developed bitmap data to the LED head interface unit 103.
The LED head interface unit 103 processes the bitmap data sent from the command / image processing unit 102 into a form that can be received by the LED heads 3 of each color, and sends them to the corresponding LED heads 3.

Each LED head 3 emits an LED corresponding to the sent data, and forms an electrostatic latent image based on the bitmap data on the surface of the uniformly charged photoreceptor drum 5.
The electrostatic latent image on the photosensitive drum 5 is developed by the developing roller 8 to form a toner image.

The control unit 104 instructs the high-voltage control unit 100 to apply a voltage again, and the primary transfer voltage control unit 107 receives the instruction and applies a predetermined primary transfer voltage to the primary transfer roller 10.
The primary transfer voltage is applied at a timing at least before the time required for the photosensitive drum 5 to rotate from the primary transfer portion to the exposure portion after the latent image formation on the photosensitive drum 5 is started. Is called.

  At the contact portion (primary transfer position) between the photosensitive drum 5 of each color and the intermediate transfer belt 11, the toner image of each color on each photosensitive drum 5 is sequentially transferred to the surface of the intermediate transfer belt 11, and finally. It is formed on the intermediate transfer belt 11 so that full-color (K, Y, M, C) unfixed toner images are superimposed.

  On the other hand, the control unit 104 controls the hopping motor 110, the registration motor 111, and the timing at which the toner image on the intermediate transfer belt 11 reaches the secondary transfer unit, that is, the nip portion between the intermediate transfer belt 11 and the secondary transfer roller 25. The conveyance motor 112 is driven. As a result, the hopping roller 30 and the conveyance rollers 18 and 19 are rotationally driven, and the recording medium loaded in the recording medium accommodation cassette 29 is fed out onto the conveyance path 31 and conveyed to the secondary transfer unit.

  The control unit 104 determines that the toner image on the intermediate transfer belt 11 is secondary based on the transmission start timing of the image data, the driving speed of the belt driving roller 12, and the distance from the primary transfer unit to the secondary transfer unit. Since the time to reach the transfer portion can be calculated, when the recording medium on the conveyance path 31 reaches the secondary transfer portion, the drive system is set so that the toner image on the intermediate transfer belt 11 reaches the secondary transfer portion. It is possible to control.

Further, the control unit 104 detects the timing at which the recording medium reaches the secondary transfer unit based on the detection signal from the sensor 24, and instructs the high voltage control unit 100 to apply a voltage at the timing. In response to this instruction, the secondary transfer voltage control unit 108 applies a voltage (negative voltage) having the same polarity as the toner to the secondary transfer backup roller 14.
In the secondary transfer portion, the negatively charged toner image on the intermediate transfer belt 11 is attracted to the recording medium by the negative voltage of the secondary transfer backup roller 14 and the positive voltage of the secondary transfer roller 25, and the recording is performed. Transferred onto the medium.

  The recording medium onto which the toner image has been transferred is conveyed to a fixing device 20 where the toner image on the recording medium is melted and pressed by a heat roller 21 and a pressure roller 22 and fixed on the recording medium. After fixing, it is discharged outside the device.

When the discharge of the recording medium is completed, the control unit 104 stops driving all the motors.
The primary transfer voltage is turned off when the intermediate transfer belt 11 is stopped by the voltage applied to each drive system. The secondary transfer voltage is turned off at the timing when the trailing edge of the printing area on the recording medium passes through the secondary transfer portion. The charging voltage and the developing voltage are turned off when the rotation of the photosensitive drum 5 is stopped.

  By repeating the above operation, a series of printing operations are performed.

  Next, the operation of bordered printing and borderless printing according to the first embodiment will be described with reference to FIGS. FIG. 3 is a diagram showing the relationship between the recording medium and the print area, FIG. 4 is an enlarged view of the secondary transfer unit, FIG. 5 is a time chart showing the operation during bordered printing, and FIG. 6 is during borderless printing. It is a time chart which shows this operation | movement.

As shown in FIG. 3, in the case of printing with a border, a toner image is formed inside the recording medium (printed region with a border), so that the toner adheres to the secondary transfer roller 25 during the secondary transfer. There is no.
On the other hand, in the case of borderless printing, a toner image is formed outside the periphery of the recording medium, so that the toner protruding from the recording medium during the secondary transfer adheres to the secondary transfer roller 25.

The toner adhering to the secondary transfer roller 25 is collected by a cleaning roller 26 to which a positive voltage having a polarity opposite to that of the toner is applied, and the toner collected on the cleaning roller 26 is scraped off by a cleaning blade 27. To be collected in the cleaner container 28.
This is because, when the next printing is performed in a state where the toner is attached to the secondary transfer roller 25, a show-through occurs in which the toner adheres to the back side of the recording medium during the secondary transfer, which deteriorates the quality of the printed matter. Because.

In FIG. 4, a contact portion (nip portion) between the intermediate transfer belt 11 and the secondary transfer roller 25 is a secondary transfer position, and a contact portion (nip portion) between the secondary transfer roller 25 and the cleaning roller 26 is a cleaning position.
The distance from the sensor 24 to the secondary transfer position is L1, the distance from the cleaning position to the secondary transfer position is L2, and the distance from the secondary transfer position to the cleaning position is L3.

First, the operation at the time of bordered printing will be described with reference to FIG.
In FIG. 5, ΔT1 is the time required for the leading edge of the recording medium to pass the sensor 24 and travel the distance L1, and ΔT2 is the time required for the secondary transfer roller 25 to rotate the distance L2.

  When the leading edge of the recording medium fed out from the recording medium accommodating cassette 29 reaches the secondary transfer sensor (sensor 24), the detection output of the sensor 24 switches from Low to High (t1). The control unit 104 monitors the detection output of the sensor 24.

When the detection output of the sensor 24 switches from Low to High, the control unit 104 instructs the cleaning voltage control unit 109 of the high voltage control unit 100 to apply a voltage.
In response to an instruction from the control unit 104, the cleaning voltage control unit 109 reverses the polarity of the toner to the cleaning roller 26 at a timing at least ΔT2 before the time when the leading edge of the recording medium passes the sensor 24 and reaches the secondary transfer position. A cleaning voltage (for example, +1.5 KV) is applied (t2).

  When the time ΔT1 elapses after the sensor 24 detects the leading edge of the recording medium being conveyed, the control unit 104 determines that the leading edge of the recording medium has reached the secondary transfer position, and The secondary transfer voltage control unit 108 is instructed to apply a voltage. The secondary transfer voltage control unit 108 applies a secondary transfer voltage (for example, −2 KV) having the same polarity as the toner to the secondary transfer backup roller 14 according to an instruction from the control unit 104 (t3).

When the trailing edge of the recording medium passes through the sensor 24, the detection output of the sensor 24 switches from High to Low (t4).
When the detection output of the sensor 24 is switched from High to Low, the control unit 104 instructs the high voltage control unit 100 to turn off voltage application. In response to this instruction, the cleaning voltage control unit 109 turns off the applied voltage (cleaning voltage) to the cleaning roller 26 at least a time ΔT2 before the time when the trailing edge of the recording medium reaches the secondary transfer position ( t5).

  When the time ΔT1 elapses after the sensor 24 detects the trailing edge of the recording medium, the control unit 104 determines that the trailing edge of the recording medium has passed the secondary transfer position and turns off the applied voltage to the high voltage control unit 100. Give instructions. Upon receiving this instruction, the secondary transfer voltage control unit 108 turns off the voltage (secondary transfer voltage) applied to the secondary transfer backup roller 14 (t6).

Next, the operation during borderless printing will be described with reference to FIG.
In FIG. 6, when the leading edge of the recording medium fed out from the recording medium accommodating cassette 29 reaches the secondary transfer sensor (sensor 24), the detection output of the sensor 24 switches from Low to High (t7). The control unit 104 monitors the detection output of the sensor 24.

When the detection output of the sensor 24 switches from Low to High, the control unit 104 instructs the cleaning voltage control unit 109 of the high voltage control unit 100 to apply a voltage.
In response to an instruction from the control unit 104, the cleaning voltage control unit 109 applies toner to the cleaning roller 26 at a timing at least ΔT2 before the time (t10) when the leading edge of the recording medium passes the sensor 24 and reaches the secondary transfer position. A cleaning voltage (V1) having a polarity opposite to that is applied (t8). The applied cleaning voltage (V1) is, for example, 1.5 KV.

  Next, the control unit 104 instructs the secondary transfer voltage control unit 108 of the high voltage control unit 100 to apply a voltage. In response to an instruction from the control unit 104, the secondary transfer voltage control unit 108 supplies the same toner as the toner to the secondary transfer backup roller 14 at a time ΔT4 before the time (t10) when the leading edge of the recording medium reaches the secondary transfer position. A polar secondary transfer voltage (for example, -2 KV) is applied (t9).

Here, ΔT4 is the time required for the recording medium to travel a distance L4 from the sheet edge of the toner image formed outside the recording medium in FIG.
That is, the secondary transfer voltage control unit 108 applies the secondary transfer voltage to the secondary transfer backup roller 14 at the timing when the leading edge of the toner image formed on the outside of the recording medium reaches the secondary transfer position. Is applied (t9).

  After the time ΔT3 has elapsed since the application of the secondary transfer voltage (t9), that is, at the timing when the toner image transferred to the secondary transfer roller 25 reaches the cleaning position, the cleaning voltage control unit 109 sets the cleaning voltage to (V1). ) To (V2) (t11). The cleaning voltage (V2) is, for example, +3 KV, and | V1 | <| V2 |.

  The cleaning voltage control unit 109 changes the cleaning voltage from V2 to V1 when the time ΔT4 has elapsed after changing the cleaning voltage (t12).

When time ΔT1 elapses after the sensor 24 detects the trailing edge of the recording medium (t13), the trailing edge of the recording medium reaches the secondary transfer position (t14).
When the time ΔT4 further elapses after the trailing edge of the recording medium reaches the secondary transfer position, the control unit 104 determines that the toner image that protrudes outward from the trailing edge of the recording medium has passed the secondary transfer position. Then, the high voltage controller 100 is instructed to turn off the applied voltage. In response to this instruction, the secondary transfer voltage control unit 108 turns off the voltage applied to the secondary transfer backup roller 14 (secondary transfer voltage) (t15).

Further, the cleaning voltage control unit 109 determines that the toner image transferred onto the secondary transfer roller 25 is at the cleaning position after the time ΔT3 has elapsed since the trailing edge of the recording medium has reached the secondary transfer position (t14). At the timing of arrival, the cleaning voltage is changed again from (V1) to (V2) (t16).
Thereafter, when the time ΔT4 has elapsed, the cleaning voltage control unit 109 turns off the cleaning voltage (t17).

  As described above, in the first exemplary embodiment, in the secondary transfer operation for borderless printing, the toner transferred from the front and rear ends of the recording medium to the transfer direction of the recording medium is transferred onto the secondary transfer roller 25. The cleaning voltage (for example, +3 KV) at the time of recovery is set higher than the cleaning voltage (for example, +1.5 KV) in the transfer area to the recording medium.

  In such a configuration, the toner transferred from the front end and the rear end in the conveyance direction of the recording medium during the borderless printing and transferred onto the secondary transfer roller 25 can be recovered well with an excellent toner recovery force. As a result, the toner can be prevented from being exposed to the recording medium during the next printing, and an excessive charging phenomenon on the surface of the secondary transfer roller, which is likely to occur when a high voltage is applied to the secondary transfer roller for a long time, is prevented. Therefore, good transfer can be performed.

  Next, based on FIG. 7, the structure of the high voltage | pressure control part 200 by Example 2 is demonstrated. FIG. 7 is a block diagram illustrating the configuration of the high-pressure controller according to the second embodiment.

As shown in FIG. 7, the high voltage control unit 200 of the present embodiment is similar to the first embodiment (FIG. 1) in that the charging voltage control unit 105, the development voltage control unit 106, the primary transfer voltage control unit 107, and the secondary transfer. A voltage control unit 108 and a cleaning voltage control unit 201 are provided to control voltage application to each roller based on an instruction (control value) from the control unit 104.
However, the cleaning voltage control unit 201 of this embodiment controls the cleaning voltage so that the current flowing through the contact portion (cleaning position) between the cleaning roller 26 and the secondary transfer roller 25 during the secondary transfer is constant. This is different from the first embodiment (FIG. 1). The other parts are the same as those of the first embodiment (FIG. 1), and the same reference numerals are given and the description thereof is omitted.

  Hereinafter, based on FIG. 8, the structure of the cleaning voltage control part 201 by a present Example is demonstrated. FIG. 8 is a block diagram illustrating the configuration of the cleaning voltage controller according to the second embodiment.

  As shown in FIG. 8, the high voltage control unit 200 includes a set value storage unit 202, a current control unit 203, a high voltage generation circuit 204, a current feedback circuit 205, an A / D converter 206, and a current detection circuit 207.

The set value storage unit 202 is a part that stores a control value instructed by the control unit 104.
The current control unit (current control unit) 203 compares the control value stored in the set value storage unit 202 with the output value of the A / D converter 206, and outputs a voltage control value corresponding to the comparison result to the high voltage generation circuit 204. This is the part to send out.

The high voltage generation circuit 204 is a circuit that generates a voltage corresponding to the voltage control value from the current control unit 203 and supplies the voltage to the cleaning roller 26. The current detection circuit 207 is a current ( That is, it is a circuit for detecting a current flowing in the cleaning position.
The current feedback circuit 205 is a circuit that feeds back the analog current output detected by the current detection circuit 207 to the A / D converter 206.

  The A / D converter 206 is a part that converts the fed back analog current output into a digital value.

Next, the operation at the time of borderless printing of the high-pressure controller 200 having the above configuration will be described with reference to FIG. FIG. 9 is a flowchart illustrating the operation of the second embodiment.
In the operation of this embodiment, the timing for turning on / off the secondary transfer voltage and the cleaning voltage is the same as that in the first embodiment (FIG. 6), and the description thereof is omitted.

  In FIG. 9, the set value storage unit 202 stores the control value instructed by the control unit 104 and notifies the current control unit 203 of the stored value (S101).

The current control unit 203 compares the control value from the set value storage unit 202 with the output value from the A / D converter 206 (S102), and if both are equal, the control value notified from the set value storage unit 202 is used. The corresponding voltage control value is sent to the high voltage generation circuit 204 (S103).
In this state, a cleaning voltage is applied to the cleaning roller 26 so that the current flowing to the cleaning position maintains a predetermined value.

On the other hand, when the output value from the A / D converter 206 is smaller than the control value from the set value storage unit 202 in S104 (this phenomenon is that the amount of toner adhering to the cleaning position is large and the current flowing therethrough is small). The current control unit 203 makes the voltage control value larger than the current value and sends it to the high voltage generation circuit 204 (S105). As a result, the cleaning voltage increases and the current flowing through the cleaning position can be set to a predetermined value.
This is a state in which the toner image protruding from the front end and the rear end in the conveyance direction of the recording medium is transferred onto the secondary transfer roller 25 during the secondary transfer at the time of borderless printing.

Further, when the output value from the A / D converter 206 is larger than the control value from the set value storage unit 202 in the previous S104 (this state is that almost no toner adheres to the cleaning position and the current flowing therethrough). Current control section 203 makes the voltage control value smaller than the current value and sends it to high voltage generation circuit 204 (S106). As a result, the cleaning voltage is reduced, and the current flowing through the cleaning position can be set to a predetermined value.
This is a transfer area portion to the recording medium, and the amount of toner transferred onto the secondary transfer roller 25 is extremely small.

  As a result of the above processing, after the state in which the cleaning voltage corresponding to the voltage control value is applied to the cleaning roller 26 is continued for a predetermined time (period in which the cleaning voltage control unit 201 performs control), the process proceeds to S102 again, and the same as above. The process is executed (S107).

  As described above, in the second exemplary embodiment, the processes in steps S101 to S107 are repeatedly performed, so that cleaning is performed in a region where a large amount of toner is adhered to the secondary transfer roller 25 and a region where the amount of toner is extremely small. The cleaning voltage is controlled so as to keep the current flowing through the position constant.

  In this way, by changing the cleaning voltage so as to keep the current flowing to the cleaning position constant, it is possible to secure an excellent toner collecting power and when a high voltage is applied to the secondary transfer roller for a long time. It is possible to prevent an overcharge phenomenon on the surface of the secondary transfer roller, which tends to occur, and to perform good transfer.

  In this embodiment, the printer has been described as an example. However, the present invention can also be applied to an electrophotographic facsimile, a copying machine, an MPF (multifunction machine), and the like.

1 Color printer (image forming device)
3 LED head (exposure means)
10 Primary transfer roller (primary transfer means)
26 Cleaning roller (cleaning means)
102 Command / Image Processing Unit 104 Control Unit 109 Cleaning Voltage Control Unit (Cleaning Voltage Control Unit)
203 Current control unit (current control means)

Claims (3)

A photoreceptor on which an electrostatic latent image is formed;
Exposure means for forming an electrostatic latent image on the photoreceptor;
Primary transfer means for transferring the developer image formed on the photosensitive member to an intermediate transfer member;
Secondary transfer means for transferring the developer image transferred onto the intermediate transfer member to a medium;
In an image forming apparatus comprising:
An edgeless image forming means for forming a developer image protruding from the edge of the medium;
Cleaning means for removing the developer image transferred onto the secondary transfer means;
Cleaning voltage control means for controlling the magnitude of the cleaning voltage applied to the cleaning means in accordance with the position on the secondary transfer means where the cleaning means removes the developer image;
An image forming apparatus comprising: The cleaning voltage control means includes
The cleaning voltage for removing the developer image in the area transferred from the leading edge and the trailing edge of the medium with respect to the conveyance direction of the medium is the cleaning voltage in the transfer area of the developer image to the medium. The image forming apparatus according to claim 1, wherein the image forming apparatus is larger.   And a current control unit configured to determine a region transferred from a front end and a rear end of the medium and a transfer region of the developer image onto the medium according to an amount of current supplied to the cleaning unit. Item 3. The image forming apparatus according to Item 2.

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