JP5659140B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  2. Description of the Related Art Conventionally, an image forming apparatus adopting an electrophotographic method charges a surface of an image carrier such as a photosensitive drum to a predetermined polarity with a charger, and exposes the charged surface of the image carrier with an exposure device to electrostatically charge the surface. A latent image is formed, and the electrostatic latent image is developed with toner by a developing device to form a toner image. Subsequently, the image forming apparatus transfers the toner image formed on the surface of the image carrier onto the transfer material (paper, intermediate transfer belt) at the transfer unit. Then, the image forming apparatus removes the residual toner remaining without being transferred to the image carrier by the cleaning member, and neutralizes the charge remaining on the image carrier by the static eliminator. The image forming apparatus repeats this process as one cycle.

In such an image forming apparatus, in order to suppress the generation of ozone and the generation of discharge products in the image carrier, it is preferable that the output of charge in the charger is as off as possible.
Further, in the image forming apparatus, the developing unit, the charge output unit constituting the transfer unit, the static eliminator, and the like perform predetermined functions, and thus ON / OFF and the like are controlled at each timing.

  Here, in order to maintain suitable image formation, the ON / OFF timing of the charger and the charge eliminator is important. However, the charge eliminator (erase lamp) is synchronized with the application timing of the charger (charging means). An image forming apparatus that is ON / OFF controlled is proposed (for example, see Patent Document 1).

JP 2003-140526 A

Here, in the image forming apparatus of Patent Document 1, ON / OFF is separately controlled for the charge output from the charger and the static eliminator.
On the other hand, for the purpose of cost reduction or the like, it is desired to reduce the number of output ports to each member on the control board or the like as much as possible.
For example, it is desired that the charge output in the charger and the ON / OFF control of the static elimination operation in the static eliminator are performed together (controlled by one output port).

However, if the charge output in the charger and the charge removal operation in the charge eliminator are simultaneously switched from ON to OFF, the image carrier is not subjected to charge removal processing on the area charged by the charger. Become.
For this reason, a defect may occur in an image formed thereafter (for example, occurrence of fogging).

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of simultaneously controlling ON / OFF of a charge output in a charger and a charge eliminating operation in a charge remover, and suppressing deterioration in quality of an image to be formed.

  According to the present invention, an image carrier that can rotate around a rotation axis and carries a toner image on a surface thereof, and is disposed to face a predetermined position on the image carrier, and outputs a charge of one polarity. A charging unit that charges the surface of the image carrier to one polarity; a developing unit that is disposed downstream of the charging unit in the rotation direction of the image carrier and that develops a toner image on the image carrier; Located downstream of the developing unit in the rotation direction of the image carrier, is disposed opposite the image carrier with the transfer material interposed therebetween, and outputs charges of the other polarity to the image carrier, A transfer unit that transfers a toner image developed by the developing unit to a transfer member; and a downstream side of the transfer unit in the rotation direction of the image carrier and an upstream side of the charging unit, and the image Remove the charge remaining on the surface of the carrier A neutralization unit; a first control unit that simultaneously controls ON / OFF of an output of charge of one polarity in the charging unit and a neutralization operation in the neutralization unit; and a second power control unit that controls the transfer unit, A second control unit that continues to output the charge of the other polarity in the transfer unit and turns off after a predetermined time when the output of the charge of one polarity in the charging unit and the neutralization operation in the neutralization unit are turned off. And an image forming apparatus.

  According to the present invention, it is possible to provide an image forming apparatus capable of simultaneously controlling ON / OFF of the charge output in the charger and the charge eliminating operation in the charge remover and suppressing the deterioration of the quality of the image to be formed.

FIG. 3 is a diagram for explaining an arrangement of each component of the printer 1 in the first embodiment. 2 is an enlarged cross-sectional view of a peripheral portion of a photosensitive drum 2. FIG. 2 is a block diagram illustrating a control system of the printer 1 according to the first embodiment. FIG. FIG. 6 is a flowchart for explaining the operation of the printer 1 in the first embodiment. It is a block diagram explaining the control system of printer 1A in a 2nd embodiment. It is a flowchart explaining the effect | action of the printer 1A in 2nd Embodiment. It is a block diagram explaining the control system of the printer 1B in 3rd Embodiment. It is a flowchart explaining the effect | action of the printer 1B in 3rd Embodiment.

Hereinafter, embodiments of the present invention will be described.
With reference to FIG. 1, the overall structure of a printer 1 as an image forming apparatus in the first embodiment of the present invention will be described. FIG. 1 is a diagram for explaining the arrangement of components of the printer 1 according to the first embodiment.

  As shown in FIG. 1, a printer 1 as an image forming apparatus includes an apparatus main body M and an image forming unit GK that forms a predetermined toner image on a sheet T as a sheet-like transfer material based on predetermined image information. And a paper supply / discharge unit KH that supplies the paper T to the image forming unit GK and discharges the paper T on which the toner image is formed.

  As shown in FIG. 1, the image forming unit GK includes a photosensitive drum 2 as an image carrier (photosensitive member), a charging unit 10, a laser scanner unit 4 as an exposure unit, a developing unit 16, and a toner cartridge. 5, a toner supply unit 6, a drum cleaning unit 11, a charge removal unit 12, a transfer roller 8 constituting a transfer unit, and a fixing unit 9.

  As shown in FIG. 1, the paper supply / discharge unit KH includes a paper feed cassette 52, a manual paper feed unit 64, a transport path L of the paper T, a registration roller pair 80, and a paper discharge unit 50.

Hereinafter, each configuration of the image forming unit GK and the paper supply / discharge unit KH will be described in detail.
First, the image forming unit GK will be described.
In the image forming unit GK, in order from the upstream side to the downstream side with respect to the surface of the photosensitive drum 2, charging by the charging unit 10, exposure by the laser scanner unit 4, development by the developing unit 16, transfer by the transfer roller 8, Cleaning by the drum cleaning unit 11, neutralization by the neutralization unit 12, and fixing by the fixing unit 9 are performed.

  The photosensitive drum 2 is made of a cylindrical member and functions as a photosensitive member or an image carrier. The photosensitive drum 2 is disposed so as to be capable of being driven to rotate in the direction of an arrow about a rotation axis J1 serving as an axis extending in a direction orthogonal to the conveyance direction of the paper T in the conveyance path L. An electrostatic latent image is formed on the surface of the photosensitive drum 2.

  The charging unit 10 is disposed to face the surface of the photosensitive drum 2. The charging unit 10 uniformly charges the surface of the photosensitive drum 2 to be negative (minus polarity) or positive (plus polarity). For example, in the present embodiment, the charging unit 10 uniformly charges the surface of the photosensitive drum 2 to a positive (plus polarity) side polarity.

  The laser scanner unit 4 functions as an exposure unit, and is disposed apart from the surface of the photosensitive drum 2. The laser scanner unit 4 includes a laser light source (not shown), a polygon mirror, a polygon mirror motor, and the like.

  The laser scanner unit 4 scans and exposes the surface of the photosensitive drum 2 based on image information output from an external device such as a PC (personal computer). By performing scanning exposure by the laser scanner unit 4, electric charges charged on the surface of the photosensitive drum 2 are removed. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 2.

  The developing unit 16 (developing roller 17) is disposed opposite to the surface of the photosensitive drum 2 on the downstream side of the charging unit 10 in the rotation direction of the photosensitive drum 2. The developing unit 16 develops a single color toner image by attaching a single color (usually black) toner to the electrostatic latent image formed on the photoconductive drum 2 (forms a toner image on the surface of the photoconductive drum). ). The developing unit 16 includes a developing roller 17 that can be disposed opposite to the surface of the photosensitive drum 2, a stirring roller 18 for stirring the toner, and the like.

  The toner cartridge 5 is provided corresponding to the developing unit 16 and stores toner supplied to the developing unit 16.

  The toner supply unit 6 is provided corresponding to the toner cartridge 5 and the developing unit 16, and supplies the toner contained in the toner cartridge 5 to the developing unit 16.

The transfer roller 8 (transfer unit) is disposed downstream of the developing unit 16 (developing roller 17) in the rotation direction of the photosensitive drum 2 so as to face the photosensitive drum with the paper T interposed therebetween.
The transfer roller 8 transfers the toner image developed on the surface of the photosensitive drum 2 to the paper T.
A transfer bias for transferring the toner image developed on the photosensitive drum 2 to the paper T is applied to the transfer roller 8. The transfer roller 8 outputs a charge having a polarity opposite to the polarity charged by the charging unit 10 to the photosensitive drum 2 side.

  The transfer roller 8 is brought into contact with and separated from the photosensitive drum 2. Specifically, the transfer roller 8 is configured to be movable between a contact position where the transfer roller 8 is in contact with the photosensitive drum 2 and a separation position where the transfer roller 8 is separated from the photosensitive drum 2. Specifically, the transfer roller 8 is moved to the contact position when the toner image developed on the photosensitive drum 2 is transferred to the paper T, and is moved to the separation position in other cases.

  A sheet T conveyed through the conveyance path L is sandwiched between the photosensitive drum 2 and the transfer roller 8. The sandwiched paper T is pressed against the surface of the photosensitive drum 2. A transfer nip N is formed between the photosensitive drum 2 and the transfer roller 8. In the transfer nip N, the toner image developed on the photosensitive drum 2 is transferred onto the paper T.

  The neutralization unit 12 is disposed downstream of the transfer roller 8 in the rotation direction of the photosensitive drum 2 and upstream of the charging unit 10. The neutralization unit 12 irradiates the surface of the photosensitive drum 2 with light, thereby removing negative (minus polarity) or positive (plus polarity) charge remaining on the surface of the photosensitive drum 2 after the transfer is performed. .

  The drum cleaning unit 11 is disposed to face the surface of the photosensitive drum 2. The drum cleaning unit 11 removes the toner and deposits remaining on the surface of the photosensitive drum 2, and transports the removed toner to a predetermined recovery mechanism via the recovery spiral 11s for recovery.

  The fixing unit 9 melts the toner constituting the toner image transferred onto the paper T and fixes it on the paper T. The fixing unit 9 includes a heating roller 9a heated by a heater, and a pressure roller 9b pressed against the heating roller 9a. The heating roller 9a and the pressure roller 9b convey the paper T on which the toner image is transferred so as to be sandwiched. When the paper T is conveyed so as to be sandwiched between the heating roller 9a and the pressure roller 9b, the toner transferred onto the paper T is melted and fixed on the paper T.

Next, the paper supply / discharge unit KH will be described.
As shown in FIG. 1, in the lower part of the apparatus main body M, a single paper feed cassette 52 that stores paper T is disposed. The paper feed cassette 52 is configured to be drawable from the apparatus main body M in the horizontal direction. In the paper feed cassette 52, a placement plate 60 on which the paper T is placed is disposed. In the paper feed cassette 52, the paper T is stored in a state of being stacked on the placement plate 60. The paper T placed on the placement plate 60 is sent out to the transport path L by the cassette paper feed unit 51 arranged at the end of the paper feed cassette 52 on the paper feed side (the left end in FIG. 1). The cassette paper feed unit 51 includes a double feed prevention mechanism including a forward feed roller 61 for taking out the paper T on the placement plate 60 and a paper feed roller pair 63 for feeding the paper T one by one to the transport path L. Prepare.

  A manual paper feed unit 64 is provided on the left side surface (left side in FIG. 1) of the apparatus main body M. The manual paper feed unit 64 is provided mainly for supplying the apparatus main body M with a paper T of a size and type different from the paper T set in the paper feed cassette 52. The manual paper feed unit 64 includes a manual feed tray 65 that forms a part of the apparatus main body M in the closed state, and a paper feed roller 66. The lower end of the manual feed tray 65 is attached to the vicinity of the paper feed roller 66 so as to be rotatable (openable and closable). The paper T is placed on the open manual feed tray 65. The manual paper feed unit 64 feeds the paper T placed on the open manual feed tray 65 to the manual feed path La.

  A paper discharge unit 50 is provided on the upper side of the apparatus main body M. The paper discharge unit 50 discharges the paper T to the outside of the apparatus main body M. Details of the paper discharge unit 50 will be described later.

  The conveyance path L for conveying the paper T is a first conveyance path L1 from the cassette paper feeding unit 51 to the transfer roller 8, a second conveyance path L2 from the transfer roller 8 to the fixing unit 9, and a discharge from the fixing unit 9. A third conveyance path L3 to the section 50, a manual conveyance path La that joins the paper supplied from the manual sheet feeding unit 64 to the first conveyance path L1, and a third conveyance path L3 from the upstream side to the downstream side. And a return transport path Lb that reverses the paper and returns it to the first transport path L1.

Moreover, the 1st junction part P1 and the 2nd junction part P2 are provided in the middle of the 1st conveyance path L1. A first branch portion Q1 is provided in the middle of the third transport path L3.
The first joining part P1 is a joining part where the manual feed path La joins the first transport path L1. The second junction P2 is a junction where the return conveyance path Lb merges with the first conveyance path L1.
The first branch portion Q1 is a branch portion where the return transport path Lb branches from the third transport path L3.

  In the middle of the first conveyance path L1 (specifically, between the second joining portion P2 and the transfer roller 8), a sensor for detecting the paper T, skew correction of the paper T (toner feeding) and toner A registration roller pair 80 is arranged for adjusting the timing with the image. The sensor is arranged immediately upstream (upstream side) of the registration roller pair 80 in the transport direction of the paper T. The registration roller pair 80 conveys the paper T by performing the above-described correction and timing adjustment based on detection information from the sensor.

  The return conveyance path Lb is a conveyance path that is provided so that the opposite surface (non-printing surface) to the surface that has already been printed faces the photosensitive drum 2 when performing duplex printing on the paper T. According to the return transport path Lb, the paper T transported from the first branching section Q1 to the paper discharge section 50 side is reversed and returned to the first transport path L1, and the resist disposed on the upstream side of the transfer roller 8 It can be conveyed to the upstream side of the roller pair 80. A predetermined toner image is transferred onto the non-printing surface by the photosensitive drum 2 on the paper T that has been turned upside down by the return conveyance path Lb.

  A paper discharge unit 50 is formed at the end of the third transport path L3. The paper discharge unit 50 is disposed on the upper side of the apparatus main body M. The paper discharge unit 50 opens toward the right side of the apparatus main body M (the right side in FIG. 1, the side opposite to the manual paper feed unit 64). The paper discharge unit 50 discharges the paper T conveyed on the conveyance path L3 to the outside of the apparatus main body M.

On the opening side of the paper discharge unit 50, a paper discharge stacking unit M1 is formed. The paper discharge stacking unit M1 is formed on the upper surface (outer surface) of the apparatus main body M. The paper discharge stacking unit M1 is a part formed by the upper surface of the apparatus main body M being depressed downward. The bottom surface of the paper discharge stacking unit M1 constitutes a part of the top surface of the apparatus main body M. In the paper discharge stacking unit M1, sheets T onto which a predetermined toner image has been transferred and discharged from the paper discharge unit 50 are stacked and stacked.
A sheet detection sensor is disposed at a predetermined position in each conveyance path.

Next, the configuration of the peripheral portion of the photosensitive drum 2 in the printer 1 and the control system centering on the peripheral portion of the photosensitive drum 2 will be described with reference to FIGS.
FIG. 2 is an enlarged cross-sectional view of the periphery of the photosensitive drum 2. FIG. 3 is a block diagram illustrating a control system of the printer 1 according to the first embodiment.

  As shown in FIG. 2, at the periphery of the photosensitive drum 2, the charging unit 10, the developing roller 17 (developing unit 16), in order from the upstream side in the rotation direction (arrow direction) of the photosensitive drum 2, A transfer roller 8 (transfer unit), a drum cleaning unit 11, and a charge removal unit 12 are disposed to face the surface of the photosensitive drum 2. Further, a current sensor 70 (measuring unit) that measures the charging current of the photosensitive drum 2 is also disposed in contact with or close to the photosensitive drum 2.

The charging unit 10 includes a charging roller 101 that rotates in sliding contact with the surface of the photosensitive drum 2.
In the present embodiment, the charging roller 101 uniformly charges the surface of the photosensitive drum 2 positively (plus polarity). The charging roller 101 is connected to a charging power supply unit 110 that outputs a positive (plus polarity) charge.

  The developing roller 17 of the developing unit 16 is connected to a developing power supply unit 120 that applies an alternating developing bias voltage.

  The transfer roller 8 that forms the transfer nip N outputs a negative (minus polarity) charge to the surface of the photosensitive drum 2 to transfer the toner image developed on the surface of the photosensitive drum 2 to the paper T. It is connected to a transfer power supply unit 130 for applying a transfer bias voltage.

The neutralization unit 12 includes a neutralization lamp (erase lamp) 102 that irradiates light on the surface of the photosensitive drum 2.
The neutralizing lamp 102 is connected to a neutralizing lamp power supply unit 140 that emits light from the neutralizing lamp 102.

A motor 2M is connected to the photosensitive drum 2. The motor 2M rotates the photosensitive drum 2 around the rotation axis J in the direction of the arrow.
The motor 2M is connected to a motor power supply unit 145.

As shown in FIG. 3, the printer 1 includes a timer 100, a charging power supply unit 110, a discharge lamp power supply unit 140, a developing power supply unit 120, a transfer power supply unit 130, and a motor power supply unit 145. , And control unit 150.
Here, in the present embodiment and other embodiments, the charging power supply unit 110 constitutes a charging unit. Further, the power source unit 140 for the static elimination lamp constitutes a static elimination unit. The transfer power unit 130 constitutes a transfer unit.

  The timer 100 has a time measuring function. The timer 100 is configured to be able to output time information to the transfer control unit 153.

  The charging power supply unit 110 causes the charging unit 10 (charging roller 101) to output charges of one polarity (plus polarity). The charging power supply unit 110 is ON / OFF controlled simultaneously with the charge removal unit 12 by the charge / charge removal control unit 151.

  The neutralization lamp power unit 140 causes the neutralization unit 12 to perform a neutralization operation. Specifically, the static elimination lamp power supply unit 140 causes the static elimination lamp 102 constituting the static elimination unit 12 to emit light. The power supply unit 140 for the static elimination lamp is ON / OFF controlled simultaneously with the charging unit 10 by the charging / static elimination control unit 151.

  The developing power supply unit 120 causes the developing roller 17 to apply an AC developing bias voltage. Specifically, the development power supply unit 120 outputs an alternating development bias voltage. The development power supply unit 120 is ON / OFF controlled by the development control unit 152.

  The transfer power supply unit 130 causes the transfer roller 8 to output charges of the other polarity (minus polarity). The transfer power supply unit 130 is ON / OFF controlled by the transfer control unit 153.

  The motor power supply unit 145 rotates the motor 2M. The motor power unit 145 is ON / OFF controlled by the motor control unit 154.

The control unit 150 includes a charging / discharging control unit 151 (first control unit), a development control unit 152, a transfer control unit 153 (second control unit), and a motor control unit 154.
Further, the control unit 150 includes various functional units (not shown) that control each element constituting the image forming unit G.

The charging / discharging control unit 151 simultaneously performs ON / OFF control on the output of the charge of one polarity in the charging unit 10 and the discharging operation in the discharging unit 12. Specifically, the charging / discharging control unit 151 simultaneously controls ON / OFF of the charging power supply unit 110 and the discharging lamp power supply unit 140.
The charging / discharging control unit 151 outputs an ON / OFF control signal to the charging power supply unit 110 and the discharging lamp power supply unit 140 from one output port 151a.
In addition, when the charging / discharging control unit 151 outputs an OFF control signal to the charging power supply unit 110 and the discharging lamp power supply unit 140, the charging / discharging control unit 151 notifies the transfer control unit 153 accordingly.

The development control unit 152 controls the application operation of the alternating development bias voltage in the development roller 17.
Specifically, the development control unit 152 performs ON / OFF control of the development power supply unit 120.
The development control unit 152 outputs an ON / OFF control signal to the development power supply unit 120 from the output port 152a.

The transfer control unit 153 performs ON / OFF control on the output of the other polarity (minus polarity) charge in the transfer roller 8.
Specifically, the transfer control unit 153 determines that the other polarity (minus polarity) in the transfer roller 8 when the output of the charge of one polarity (plus polarity) in the charging unit 10 and the neutralization operation in the neutralization unit 12 are turned off. ) Continues to be output and is turned off after a predetermined time.
The transfer control unit 153 controls ON / OFF of the transfer power supply unit 130.
More specifically, the transfer control unit 153 outputs an OFF control signal after a predetermined time from receiving the above notification from the charging / discharging control unit 151 to the transfer power supply unit 130 from the output port 153a.

Here, for a predetermined time, the photosensitive drum 2 facing the charging unit 10 when the charging / discharging control unit 151 outputs an OFF control signal to the charging power supply unit 110 and the discharging lamp power supply unit 140. This time is equal to or shorter than the time required for the predetermined area on the surface to move to a position facing the transfer roller 8. For example, the predetermined time is the time until the predetermined area is located immediately before the position facing the transfer roller.
The predetermined time is, for example, the circumferential speed of the photosensitive drum 2 and the length (circumferential length) of the region from the position facing the charging unit 10 to the position facing the transfer nip N (immediately before) on the photosensitive drum 2. Calculated based on
In the present embodiment, the predetermined time is set in advance in the transfer control unit 153.

The motor control unit 154 controls the motor 2M. Specifically, the motor control unit 154 controls ON / OFF of the motor power supply unit 145.
The motor control unit 154 outputs an ON / OFF control signal from the output port 154a to the motor 2M.

Here, the control unit 150 has a control program. The control unit 150 receives an operation instruction (image formation instruction) signal based on a predetermined control program, and controls the charging / discharging control unit 151, the development control unit 152, the transfer control unit 153, and the motor control unit 154. Operate according to the procedure. The control unit 150 controls the operations of the charging unit 10, the charge removal unit 12, the developing unit 16, the transfer roller 8, and the photosensitive drum 2 through each function control unit.
The control unit 150 controls the image forming operation of the image forming unit GK by operating a predetermined function control unit based on a predetermined control program.

Next, the operation of the printer 1 in the first embodiment will be described with reference to FIG. Specifically, the operation of the charging unit 10, the developing unit 16, the transfer roller 8, the static eliminating unit 12, the motor 2M of the photosensitive drum 2, and the control unit 150 that controls them will be described.
FIG. 4 is a flowchart for explaining the operation of the printer 1 in the first embodiment.

  First, in step ST11, the printer 1 (control unit 150) receives an image formation instruction including image information via a communication unit (not shown). Thereby, the printer 1 (the control unit 150 and the image forming unit GK) starts a predetermined operation.

Subsequently, in step ST12, the control unit 150 operates each function control unit based on the control program. Specifically, the charging / discharging control unit 151 outputs an ON control signal to the charging power supply unit 110 and the discharging lamp power supply unit 140 via the output port 151a. Further, the development control unit 152 outputs an ON control signal to the development power supply unit 120 via the output port 152a. The transfer controller 153 outputs an ON control signal to the transfer power supply unit 130 via the output port 153a. The motor control unit 154 outputs an ON control signal to the motor power supply unit 145 via the output port 154a.
As a result, the charging power supply unit 110, the discharge lamp power supply unit 140, the developing power supply unit 120, and the motor power supply unit 145 are turned on.

Subsequently, in step ST13, the control unit 150 causes the image forming unit GK to perform an image forming operation. Specifically, the control unit 150 causes the image forming unit G to perform an image forming operation by operating various functional units. The control unit 150 causes the image forming unit GK to form an image based on the image information by operating the function control units in a predetermined order.
The image forming unit GK is charged by the charging unit 10, exposed by the laser scanner unit 4, developed by the developing unit 16, transferred by the transfer roller 8, and a drum cleaning unit based on instructions from each functional unit included in the control unit 150. The image forming processing operation is performed in which one cycle includes cleaning by 11, discharging by the discharging unit 12, and fixing by the fixing unit 9.

Subsequently, in step ST14, when the image forming operation based on one image forming instruction is completed, the control unit 150 confirms whether there is another image forming instruction.
If there is another image forming instruction (YES at ST14), control unit 150 returns the process to step ST13 and causes image forming unit G to perform an image forming operation based on the other image forming instruction.
If there is no further other image formation instruction (ST14, NO), control unit 150 advances the process to step ST15.

Subsequently, in step ST15, the control unit 150 (charging / discharging control unit 151) outputs an OFF control signal to the charging power supply unit 110 and the discharging lamp power supply unit 140.
As a result, the charging power supply unit 110 and the discharge lamp power supply unit 140 are simultaneously turned off.
Here, when the charging power supply unit 110 and the discharge lamp power supply unit 140 are simultaneously turned off, the region from the position facing the charging unit 10 to the position facing the transfer roller 8 on the photosensitive drum 2 is as follows. It is in a state of being charged by the charging unit 10.

  In addition, when the charging / discharging control unit 151 outputs an OFF control signal to the charging power supply unit 110 and the discharging lamp power supply unit 140, the charging / discharging control unit 151 notifies the transfer control unit 153 accordingly.

  The control unit 150 (development control unit 152) outputs an OFF control signal to the development power supply unit 120.

Subsequently, in step ST16, the control unit 150 (transfer control unit 153) determines whether or not a predetermined time has elapsed since the charging power supply unit 110 and the discharge lamp power supply unit 140 are turned off.
Specifically, the transfer control unit 153 determines, based on the time information from the timer 100, whether or not a predetermined time has elapsed since receiving the notification from the charging / discharging control unit 151.
Here, for a predetermined time, the photosensitive drum 2 facing the charging unit 10 when the charging / discharging control unit 151 outputs an OFF control signal to the charging power supply unit 110 and the discharging lamp power supply unit 140. The time required for the predetermined area on the surface to move to a position immediately before the position facing the transfer roller 8 is set.

  When it is determined that the predetermined time has not elapsed (NO in step ST16), the control unit 150 (transfer control unit 153) returns the process to step ST16 and continues to make a determination based on time information from the timer.

  If control unit 150 (transfer control unit 153) determines that a predetermined time has elapsed (YES in step ST16), the process proceeds to step ST17.

  Subsequently, in step ST <b> 17, the control unit 150 (transfer control unit 153) outputs an OFF control signal to the transfer power supply unit 130. As a result, the transfer power supply unit 130 is turned off.

Thus, after the charging power supply unit 110 and the discharge lamp power supply unit 140 are simultaneously turned OFF, the printer 1 uses the transfer bias by keeping the transfer power supply unit 130 ON for a predetermined time. Then, a charge removal process is performed on the charged region.
Accordingly, the printer 1 can suppress the occurrence of problems such as fogging in the image formed on the paper T.

The control unit 150 (motor control unit 154) outputs an OFF control signal to the motor power supply unit 145.
Then, the printer 1 (the control unit 150) ends the operation based on the received image formation instruction.

According to the printer 1 of the first embodiment, the following effects are produced.
The printer 1 includes a charging / discharging control unit 151 that simultaneously controls ON / OFF of the charging power supply unit 110 and the discharging lamp power supply unit 140.
Thereby, the printer 1 can reduce the number of output ports in the control unit 150. Accordingly, the printer 1 is configured to be able to reduce component costs such as a substrate cost.

In addition, when the charging power supply unit 110 and the discharge lamp power supply unit 140 are simultaneously controlled to be OFF, the printer 1 includes a transfer control unit 153 that keeps the transfer power supply unit 130 ON and turns it OFF after a predetermined time. Prepare.
Thereby, the printer 1 can suppress the occurrence of problems such as fogging in the image formed on the paper T. Specifically, it is as follows.
First, when the charging power supply unit 110 and the discharge lamp power supply unit 140 are simultaneously turned off, the region from the position facing the charging unit 10 to the position facing the transfer roller 8 on the photosensitive drum 2 is charged. It is in a state of being charged by the unit 10.
On the other hand, after the charging power supply unit 110 and the discharge lamp power supply unit 140 are simultaneously turned OFF, the printer 1 uses the transfer bias by keeping the transfer power supply unit 130 ON for a predetermined time. Then, the charge removal process is performed on the charged region.
As a result, the printer 1 can suppress the occurrence of problems such as fogging in the image formed on the paper T.

Further, in this embodiment, the charging / discharging control unit 151 faces the charging unit 10 when the charging / discharging control unit 151 outputs an OFF control signal to the charging power supply unit 110 and the discharging lamp power supply unit 140 in the predetermined time. This time is equal to or shorter than the time required for the predetermined area on the surface of the photosensitive drum 2 to move to a position facing the transfer roller 8. For example, the predetermined time is the time until the predetermined area is located immediately before the position facing the transfer roller.
In other words, the printer 1 can suitably neutralize an area that is not discharged if left untreated by using the transfer bias in the transfer roller 8.

  In addition, the printer 1 performs transfer before the predetermined area on the surface of the photosensitive drum 2 facing the charging unit 10 moves to a position facing the transfer roller 8 (before the position facing the transfer roller 8). By controlling the power supply unit 130 to be OFF, it is possible to suppress the occurrence of so-called reverse charging, in which a charge having a reverse polarity to the charging by the charging unit 10 is added to the surface of the photosensitive drum 2. Thereby, the printer 1 maintains the stability of the image quality.

  Next, a second embodiment of the present invention will be described. The second embodiment will be described mainly with respect to differences from the first embodiment. The same components as those in the first embodiment will be denoted by the same reference numerals, and detailed description thereof will be omitted. In the second embodiment, the description of the first embodiment is appropriately applied to points that are not particularly described. Furthermore, in the second embodiment, the same effect as that of the first embodiment is achieved.

  In the printer 1A (control unit 150A) according to the second embodiment, the charging / discharging control unit 151 performs the output of the charge of one polarity in the charging unit 10 (charging roller 101) and the discharging operation in the discharging unit 12 (discharge lamp 102). When turned off, the output amount per unit time of other polar charges output from the transfer roller 8 is the same as the output of one polarity charge in the charging unit 10 and before the discharging operation in the discharging unit 12 is turned off. This is different from the printer 1 in the first embodiment in that the output amount is changed to be smaller than the output amount.

The printer 1A according to the second embodiment will be described with reference to FIGS.
FIG. 5 is a block diagram illustrating a control system of the printer 1A according to the second embodiment. FIG. 6 is a flowchart for explaining the operation of the printer 1A according to the second embodiment.

As shown in FIG. 5, the printer 1 </ b> A includes a transfer bias changing unit 131.
The transfer bias changing unit 131 is connected to the transfer power supply unit 130 and changes the transfer bias voltage.
The transfer bias changing unit 131 changes the output amount per unit time of negative (minus polarity) charge output from the transfer power supply unit 130 to the surface side of the photosensitive drum 2, that is, the transfer bias voltage.

  The transfer bias changing unit 131 receives a control signal including information on the changed bias voltage value VB from the transfer control unit 153 via the output port 153b. The transfer bias changing unit 131 changes the transfer bias to the change bias voltage value VB based on the received information of the change bias voltage value VB.

Here, the transfer bias during the normal operation is often large for the charge removal processing on the area charged by the charging unit 10. Therefore, the change bias voltage value VB is normally a voltage value smaller than the transfer bias voltage value VA during normal operation.
As described above, the transfer bias changing unit 131 changes the transfer bias voltage value to the change bias voltage value VB that is a voltage value smaller than the transfer bias voltage value VA at the time of transfer.

The printer 1 </ b> A includes an output value storage unit 210.
The output value storage unit 210 stores a changed bias voltage value VB that is changed in the transfer bias changing unit 131 when the charging power supply unit 110 and the discharge lamp power supply unit 140 are turned off.
The change bias voltage value VB is a voltage value smaller than the transfer bias voltage value VA set at the time of transfer as described above.
The change bias voltage value VB is a voltage value at which reverse charging does not occur (or can be suppressed) when the area charged by the charging unit 10 is neutralized by the transfer roller 8.
The output value storage unit 210 outputs information on the changed bias voltage value VB to the transfer control unit 153.

  The transfer control unit 153 controls the transfer bias changing unit 131 in addition to the operation in the first embodiment. In the present embodiment, the transfer control unit 153 has information on a transfer bias voltage value VA that is a voltage value of a transfer bias at the time of transfer.

When receiving the above notification from the charging / discharging control unit 151, the transfer control unit 153 outputs a control signal including information on the changed bias voltage value VB to the transfer bias changing unit 131 from the output port 153b.
Then, the transfer control unit 153 outputs an OFF control signal to the transfer power supply unit 130 from the output port 153a after a predetermined time from receiving the above notification from the charging / discharging control unit 151.

  The transfer control unit 153 transfers the transfer roller when the charge / discharge control unit 151 turns off the output of the charge of one polarity in the charging unit 10 (charging roller 101) and the discharging operation in the discharging unit 12 (discharge lamp 102). 8, the output amount per unit time of the charge of the other polarity output in 8 is changed to be smaller than the output amount of the charge of one polarity in the charging unit 10 and the output amount before the discharging operation in the discharging unit 12 is turned off. .

  Next, the operation of the printer 1A in the second embodiment will be described with reference to FIG. Specifically, the operation of the charging unit 10, the developing unit 16, the transfer roller 8, the static eliminating unit 12, the motor 2M of the photosensitive drum 2, and the control unit 150A that controls them will be described.

  First, in step ST21, the printer 1A (control unit 150A) receives an image formation instruction including image information via a communication unit (not shown). Accordingly, the printer 1A (the control unit 150A and the image forming unit GK) starts a predetermined operation.

Subsequently, in step ST22, the control unit 150A operates each function control unit based on the control program. Specifically, the charging / discharging control unit 151 outputs an ON control signal to the charging power supply unit 110 and the discharging lamp power supply unit 140 via the output port 151a. Further, the development control unit 152 outputs an ON control signal to the development power supply unit 120 via the output port 152a. The transfer controller 153 outputs an ON control signal to the transfer power supply unit 130 via the output port 153a. The motor control unit 154 outputs an ON control signal to the motor power supply unit 145 via the output port 154a.
As a result, the charging power supply unit 110, the discharge lamp power supply unit 140, the developing power supply unit 120, and the motor power supply unit 145 are turned on.
In addition, the transfer control unit 153 outputs a control signal including information on the bias voltage value VA to the transfer bias changing unit 131 via the output port 153b. Thereby, the voltage value of the transfer bias at the time of transfer in the transfer roller 8 is set to the transfer bias voltage value VA.

Subsequently, in step ST23, the control unit 150A causes the image forming unit GK to perform an image forming operation. Specifically, the control unit 150A causes the image forming unit G to perform an image forming operation by operating various functional units. The control unit 150A causes the image forming unit GK to form an image based on the image information by operating the function control units in a predetermined order.
The image forming unit GK is charged by the charging unit 10, exposed by the laser scanner unit 4, developed by the developing unit 16, transferred by the transfer roller 8, and a drum cleaning unit based on instructions from each functional unit included in the control unit 150 </ b> A. The image forming processing operation is performed in which one cycle includes cleaning by 11, discharging by the discharging unit 12, and fixing by the fixing unit 9.

Subsequently, in step ST24, when the image forming operation based on one image forming instruction is completed, control unit 150A confirms whether there is another image forming instruction.
When there is another image forming instruction (YES in ST24), control unit 150A returns the process to step ST23 and causes image forming unit G to perform an image forming operation based on the other image forming instruction.
If there is no further other image formation instruction (ST24, NO), control unit 150A advances the process to step ST25.

Subsequently, in step ST25, the control unit 150A (charging / discharging control unit 151) outputs an OFF control signal to the charging power supply unit 110 and the discharging lamp power supply unit 140.
As a result, the charging power supply unit 110 and the discharge lamp power supply unit 140 are simultaneously turned off.
Here, when the charging power supply unit 110 and the discharge lamp power supply unit 140 are simultaneously turned off, the region from the position facing the charging unit 10 to the position facing the transfer roller 8 on the photosensitive drum 2 is as follows. It is in a state of being charged by the charging unit 10.

  In addition, when the charging / discharging control unit 151 outputs an OFF control signal to the charging power supply unit 110 and the discharging lamp power supply unit 140, the charging / discharging control unit 151 notifies the transfer control unit 153 accordingly.

  The control unit 150A (development control unit 152) outputs an OFF control signal to the development power supply unit 120.

Subsequently, in step ST26, the control unit 150A (transfer control unit 153) causes the transfer bias changing unit 131 to change the transfer bias voltage.
When receiving the above notification from the charging / discharging control unit 151, the transfer control unit 153 outputs a control signal including information on the changed bias voltage value VB to the transfer bias changing unit 131 from the output port 153b.
Accordingly, the transfer control unit 153 changes the transfer bias voltage value at the transfer roller 8 from the transfer bias voltage value VA at the time of transfer to the changed bias voltage value VB.
Since the voltage value of the transfer bias in the transfer roller 8 is changed to the changed bias voltage value VB that is smaller than the transfer bias voltage value VA, the area charged by the charging unit 10 is subjected to charge removal processing by the transfer roller 8. In the region, reverse charging does not occur (or is suppressed).

Subsequently, in step ST27, the control unit 150A (transfer control unit 153) determines whether or not a predetermined time has elapsed since the charging power supply unit 110 and the discharge lamp power supply unit 140 are turned off.
Specifically, the transfer control unit 153 determines, based on the time information from the timer 100, whether or not a predetermined time has elapsed since receiving the notification from the charging / discharging control unit 151.
Here, for a predetermined time, the photosensitive drum 2 facing the charging unit 10 when the charging / discharging control unit 151 outputs an OFF control signal to the charging power supply unit 110 and the discharging lamp power supply unit 140. The time required for the predetermined area on the surface to move to a position immediately before the position facing the transfer roller 8 is set.

  When it is determined that the predetermined time has not elapsed (NO in step ST27), control unit 150A (transfer control unit 153) returns the process to step ST27 and continues to make a determination based on time information from the timer.

  When controller 150A (transfer controller 153) determines that the predetermined time has elapsed (YES in step ST27), the process proceeds to step ST28.

  Subsequently, in step ST28, the control unit 150A (transfer control unit 153) outputs an OFF control signal to the transfer power supply unit 130. As a result, the transfer power supply unit 130 is turned off.

  Thus, in the printer 1A, after the charging power supply unit 110 and the discharge lamp power supply unit 140 are simultaneously turned off, the transfer bias changing unit 131 decreases the transfer bias voltage value and the transfer power supply unit 130 is turned on. By continuing the state for a predetermined time, the charge removal process is suitably performed on the charged area using a transfer bias.

In addition, the control unit 150A (motor control unit 154) outputs an OFF control signal to the motor power supply unit 145.
Then, the printer 1A (the control unit 150A) ends the operation based on the received image formation instruction.

According to the printer 1 of the second embodiment, in addition to the same effects as those of the first embodiment, for example, the following effects are exhibited.
In addition, when the charging power supply unit 110 and the discharge lamp power supply unit 140 are simultaneously OFF-controlled, the printer 1A (transfer control unit 153) sets the bias voltage value output from the transfer power supply unit 130 during normal transfer. The changed bias voltage value VB is smaller than the bias voltage value VA.
As a result, it is possible to suppress the occurrence of reverse charging that tends to occur on the surface of the photosensitive drum 2 because the transfer current value is too high if the bias voltage value VA during normal transfer remains unchanged. Accordingly, the printer 1A can maintain the voltage value on the surface of the photosensitive drum 2 with good stability. This also, the printer 1A is a quality of the image that will be formed on the sheet T can be stabilized.

  Next, a third embodiment of the present invention will be described. The third embodiment will be described mainly with respect to differences from the second embodiment, the same reference numerals are given to the same configurations as those in the first and second embodiments, and detailed description thereof will be omitted. In the third embodiment, the descriptions of the first and second embodiments are appropriately applied to points that are not particularly described. Furthermore, in the third embodiment, the same effects as those in the first and second embodiments are achieved.

In the printer 1B (control unit 150B) according to the third embodiment, the transfer control unit 153 causes the charging / discharging control unit 151 to output charges of one polarity in the charging unit 10 (charging roller 101) and the discharging unit 12 (static discharge lamp). 102), when the discharging operation is turned off, the charging unit 10 determines the output amount per unit time of charges of other polarity output from the transfer roller 8 according to the charging current value measured by the current sensor 70. Is different from the printer 1 </ b> A in the second embodiment in that it is changed to be smaller than the output amount of the charge of one polarity in FIG.
The printer 1B is different from the printer 1A in the second embodiment in that the changed bias voltage value VB is set according to the charging current value measured by the current sensor 70.

A printer 1B according to the third embodiment will be described with reference to FIGS.
FIG. 7 is a block diagram illustrating a control system of the printer 1B according to the third embodiment. FIG. 8 is a flowchart for explaining the operation of the printer 1B according to the third embodiment.

As illustrated in FIG. 7, the printer 1 </ b> B includes a current sensor 70.
The current sensor 70 measures a charging current in the photosensitive drum 2. The current sensor 70 measures the charging current value μA in the photosensitive drum 2 by the flow current to the charging roller 101. The current sensor 70 measures a charging current in the photosensitive drum 2 when the charging power supply unit 110 and the discharge lamp power supply unit 140 are turned off. The current sensor 70 outputs information on the measured charging current value to an output value setting unit 155 described later.

In addition, the printer 1B includes a setting condition storage unit 220.
The setting condition storage unit 220 stores setting conditions (for example, a table, a table, a calculation formula, etc.) for the output value setting unit 155 to be described later to set the changed bias voltage value VB based on the charging current value.
The setting condition storage unit 220 outputs the above setting conditions to the output value setting unit 155.

The printer 1B (control unit 150B) includes an output value setting unit 155.
The output value setting unit 155 sets the change bias voltage value VB in accordance with the charging current value information from the current sensor 70.
Specifically, the output value setting unit 155 sets the changed bias voltage value VB corresponding to the charging current value based on the information on the setting condition from the setting condition storage unit 220.
For example, the output value setting unit 155 sets a change bias voltage value VB that provides an appropriate charge removal transfer current value −dμA according to the charging current value dμA measured by the current sensor 70.
The output value setting unit 155 is an appropriate neutralization transfer current set so that the charging voltage on the photosensitive drum 2 after neutralization becomes 0 V (or in the vicinity of 0 V) according to the charging current value dμA measured by the current sensor 70. A value −dμA is obtained, and a changed bias voltage value VB from which an appropriate static transfer current value −dμA is obtained is set.

Then, the transfer control unit 153 outputs control information including the changed bias voltage value VB set according to the charging current value by the output value setting unit 155 to the transfer bias changing unit 131.
The transfer controller 153 is a current sensor when the charge / discharge controller 151 turns off the output of the charge of one polarity in the charging unit 10 (charging roller 101) and the discharging operation in the discharging unit 12 (discharge lamp 102). According to the charging current value measured at 70, the output amount per unit time of the charges of other polarity output from the transfer roller 8 is output as the charge output of one polarity at the charging unit 10 and the charge removal at the charge removal unit 12. The output amount is changed to be smaller than that before the operation is turned off.

  The operation of the printer 1B in the third embodiment will be described with reference to FIG. Specifically, the operation of the charging unit 10, the developing unit 16, the transfer roller 8, the static eliminating unit 12, the motor 2M of the photosensitive drum 2, and the control unit 150B that controls these will be described.

  Here, step ST31 to step ST34 are the same as step ST21 to step ST24 described in the second embodiment, and a description thereof will be omitted.

Subsequently, in step ST35, the control unit 150B (charging / discharging control unit 151) outputs an OFF control signal to the charging power supply unit 110 and the discharging lamp power supply unit 140.
As a result, the charging power supply unit 110 and the discharge lamp power supply unit 140 are simultaneously turned off.
Here, when the charging power supply unit 110 and the discharge lamp power supply unit 140 are simultaneously turned off, the region from the position facing the charging unit 10 to the position facing the transfer roller 8 on the photosensitive drum 2 is as follows. It is in a state of being charged by the charging unit 10.

  In addition, when the charging / discharging control unit 151 outputs an OFF control signal to the charging power supply unit 110 and the discharging lamp power supply unit 140, the charging / discharging control unit 151 notifies the transfer control unit 153 accordingly.

  The control unit 150B (development control unit 152) outputs an OFF control signal to the development power supply unit 120.

Subsequently, in step ST36, the control unit 150B (output value setting unit 155) sets the changed bias voltage value VB according to the charging current value measured by the current sensor 70.
Specifically, the output value setting unit 155 sets the changed bias voltage value VB corresponding to the charging current value based on the information on the setting condition from the setting condition storage unit 220.
As described above, for example, the output value setting unit 155 sets the change bias voltage value VB at which the proper charge removal transfer current value −dμA is obtained according to the measured value dμA of the charging current value measured by the current sensor 70.
The output value setting unit 155 outputs information about the set changed bias voltage value VB to the transfer control unit 153.

Subsequently, in step ST37, the control unit 150B (transfer control unit 153) causes the transfer bias changing unit 131 to change the transfer bias voltage.
When the transfer control unit 153 receives the above notification from the charge / discharge control unit 151, the transfer control unit 153 controls the transfer bias changing unit 131 from the output port 153b to include information on the changed bias voltage value VB acquired from the output value setting unit 155. Output a signal.
Accordingly, the transfer control unit 153 changes the transfer bias voltage value at the transfer roller 8 from the transfer bias voltage value VA at the time of transfer to the changed bias voltage value VB.
Since the voltage value of the transfer bias in the transfer roller 8 is changed to the changed bias voltage value VB that is smaller than the transfer bias voltage value VA, the area charged by the charging unit 10 is subjected to charge removal processing by the transfer roller 8. In the region, reverse charging does not occur (or is suppressed).
In the present embodiment, since an appropriate bias voltage value corresponding to the charging current value measured by the current sensor 70 is set as the changed bias voltage value, the printer 1B is suitable for suppressing the reverse charging described above. Static elimination can be performed.

Subsequently, in step ST38, the control unit 150B (transfer control unit 153) determines whether or not a predetermined time has elapsed since the charging power supply unit 110 and the discharge lamp power supply unit 140 are turned off.
Specifically, the transfer control unit 153 determines, based on the time information from the timer 100, whether or not a predetermined time has elapsed since receiving the notification from the charging / discharging control unit 151.
Here, for a predetermined time, the photosensitive drum 2 facing the charging unit 10 when the charging / discharging control unit 151 outputs an OFF control signal to the charging power supply unit 110 and the discharging lamp power supply unit 140. The time required for the predetermined area on the surface to move to a position immediately before the position facing the transfer roller 8 is set.

  If it is determined that the predetermined time has not elapsed (NO in step ST38), control unit 150B (transfer control unit 153) returns the process to step ST38 and continues to make a determination based on time information from the timer.

  If controller 150B (transfer controller 153) determines that the predetermined time has elapsed (YES in step ST38), the process proceeds to step ST39.

  Subsequently, in step ST39, the control unit 150B (transfer control unit 153) outputs an OFF control signal to the transfer power supply unit. As a result, the transfer power supply unit 130 is turned off.

Thus, in the printer 1, after the charging power supply unit 110 and the discharge lamp power supply unit 140 are simultaneously turned off, the transfer bias voltage value is reduced by the transfer bias changing unit 131 and the transfer power supply unit 130 is turned on. By continuing the state for a predetermined time, the charge removal process is more suitably performed on the charged area using the transfer bias.
In addition, the printer 1B sets an appropriate bias voltage value as the changed bias voltage value in accordance with the charging current value measured by the current sensor 70, so that the above-described reverse charge is further suppressed to perform suitable static elimination. Can do.

Further, the control unit 150B (motor control unit 154) outputs an OFF control signal to the motor power supply unit 145.
Then, the printer 1B (the control unit 150A) ends the operation based on the received image formation instruction.

According to the printer 1B of the third embodiment, in addition to the same effects as those of the first and second embodiments, for example, the following effects are exhibited.
In addition, when the charging power supply unit 110 and the discharge lamp power supply unit 140 are simultaneously OFF-controlled, the printer 1B (transfer control unit 153) transfers the transfer power supply unit according to the charging current value measured by the current sensor 70. The bias voltage value output from 130 is changed to a changed bias voltage value VB smaller than the bias voltage value VA during normal transfer.
As a result, the voltage value of the transfer bias in the transfer roller 8 is changed to a changed bias voltage value VB that is smaller than the transfer bias voltage value VA. Reverse charging does not occur (or is suppressed) in the area that has been damaged.
Accordingly, since the printer 1B sets an appropriate bias voltage value as the changed bias voltage value according to the charging current value measured by the current sensor 70, the above-described reverse charge is further suppressed. It can be performed.

  Further, according to the printer 1B, an appropriate bias voltage for static elimination can be output even when the charging ability of the photosensitive drum 2 is changed due to environmental fluctuations, shaving or deterioration of the photosensitive layer, and the like. Thereby, the printer 1B can stably maintain the voltage value on the surface of the photosensitive drum 2 with high accuracy. Accordingly, the printer 1B can further stabilize the quality of the image formed on the paper T.

In each of the above embodiments, the monochrome type printer 1 is described as the image forming apparatus. However, the image forming apparatus is not limited to this, and may be a color printer, a copier, a facsimile, a complex machine thereof, or the like.
Further, the material to be transferred is not limited to paper, and may be a film-like sheet or an intermediate transfer belt.

DESCRIPTION OF SYMBOLS 1 ... Printer (image forming apparatus), 2 ... Photosensitive drum (image carrier), 8 ... Transfer roller (transfer part), 10 ... Charging part, 12 ... Static elimination part, 16 ... Development part, 70... Current sensor (measuring unit) 100 ... Timer, 110... Charging power supply unit, 140. ... Control unit 151 ... Charge / charge elimination control unit (first control unit), 153 ... Transfer control unit (second control unit), 155 ... Output value setting unit, T ... Paper (material to be transferred)

Claims (3)

An image carrier capable of rotating about a rotation axis and carrying a toner image on the surface;
A charging unit that is arranged opposite to a predetermined position in the image carrier, and outputs a charge of one polarity to charge the surface of the image carrier to one polarity;
A developing unit disposed downstream of the charging unit in the rotation direction of the image carrier and developing a toner image on the image carrier;
Located downstream of the developing unit in the rotation direction of the image carrier, is disposed opposite the image carrier with the transfer material interposed therebetween, and outputs charges of the other polarity to the image carrier, A transfer unit for transferring the toner image developed by the development unit to a transfer member;
A charge removal unit disposed downstream of the transfer unit in the rotation direction of the image carrier and upstream of the charging unit, and removing charges remaining on the surface of the image carrier;
A first control unit that simultaneously performs ON / OFF control of the output of charge of one polarity in the charging unit and the discharging operation in the discharging unit;
A second power control unit for controlling the transfer unit,
A second control unit that continues to output the charge of the other polarity in the transfer unit and turns off after a predetermined time when the output of the charge of one polarity in the charging unit and the neutralization operation in the neutralization unit are turned off. An image forming apparatus. The second controller is
A predetermined area in the image carrier, which is opposite to the charging section when the output of the charge of one polarity in the charging section and the discharging operation in the discharging section is turned off, is the transfer section. The image forming apparatus according to claim 1, wherein the output of the charge of the other polarity in the transfer unit is turned off before moving to a position opposite to. The second controller is
When the output of one polarity of charge in the charging unit and the neutralization operation in the neutralization unit are turned off by the first control unit, the output amount per unit time of the other polarity of charge output in the transfer unit 3. The image forming apparatus according to claim 1, wherein the output amount is changed to be smaller than an output amount of the charge of one polarity in the charging unit and an output amount before the discharging operation in the discharging unit is turned off.

Images