JP2018136426A - Image forming apparatus and method for controlling image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the time required to start printing.SOLUTION: An image forming apparatus comprises: an application circuit connected to a transfer unit, and including a first application part that applies a voltage having a polarity opposite to that of a voltage of a charger, and a second application part that is connected in series to the first application part and applies a voltage having the same polarity as that of the voltage of the charger; and a control part. The control part executes: first inhibitory control (time t2 to t5) of, after the start of application of a charging voltage Vc to the charger, applying a voltage Vb from the second application part with a control value based on a current I flowing in the application circuit; storage processing of storing the control value in the first inhibitory control in storage means; reverse transfer control (time t5 to t6) of, after the first inhibitory control, applying a reverse transfer voltage Vb1 having a larger absolute value than that in the first inhibitory control from the second application part; second inhibitory control (time t6 to t7) of, after the reverse transfer control, applying the voltage Vb from the second application part with the control value stored in the storage means; and transfer voltage application control (time t7 and time subsequent thereto) of, after the second inhibitory control, applying a voltage Vt from the first application part.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image forming apparatus including an application circuit connected to a transfer device, and a control method for the image forming apparatus.

  2. Description of the Related Art Conventionally, in an image forming apparatus, a voltage having the same polarity as that of a developer is applied to a transfer device between the input of a print command and the start of printing, and the developer on the photoconductor moves to the transfer device. Those configured to suppress this are known. For example, in the image forming apparatus disclosed in Patent Document 1, after a print command is input, the exposure device outputs laser light once in order to determine the timing of writing by laser light. As a result, the photosensitive member is exposed, so that a developer is supplied from the developing device onto the photosensitive member. On the other hand, a voltage having the same polarity as that of the developer is applied to the transfer device after a print command is input. Therefore, it is possible to suppress the developer placed on the photosensitive member from moving to the transfer unit. When printing is started, a voltage having a polarity opposite to that of the developer is applied to the transfer device.

  Further, conventionally, in an image forming apparatus, an application circuit connected to a transfer device is controlled to prevent an inflow current from flowing from a charged photoreceptor to the application circuit via the transfer device. Those configured to suppress the unstable operation are known. For example, in the image forming apparatus disclosed in Patent Document 2, the application circuit is connected in series to a first application unit that generates a first voltage having a polarity opposite to the polarity of the developer, and the first application unit, and the developer. And a second application unit that generates a second voltage having the same polarity as the first polarity. Then, when a print command is input and the photosensitive member is charged by the charger, first, inflow suppression control for generating a voltage in the second application unit is performed so that the current flowing through the application circuit becomes zero. It has become. After the inflow suppression control, the voltage to be generated at the second application unit is fixed, and control is performed to generate the voltage at the first application unit. Thereby, it is possible to suppress the inflow current from flowing from the photosensitive member and to stabilize the application circuit.

Japanese Patent Laid-Open No. 2006-71106 JP 2011-215262 A

  By the way, after executing the control for suppressing the developer on the photosensitive member from moving to the transfer unit described above, if the control for suppressing the inflow current is to be executed, the printing starts after the print command is input. It takes a long time.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus and a method for controlling the image forming apparatus that can shorten the time required to start printing.

In order to achieve the above-described object, an image forming apparatus of the present invention includes a photoreceptor carrying a developer, a charger for charging the photoreceptor, a transfer unit for transferring the developer on the photoreceptor to a transfer medium, A first application unit that applies a voltage having a polarity opposite to that of the charger, and a second application unit that is connected in series to the first application unit and applies a voltage having the same polarity as the voltage of the charger; An application circuit connected to the container, a storage means, and a control unit.
The control unit stores the control value in the first suppression control and the first suppression control in which the voltage is applied from the second application unit with the control value based on the current flowing in the application circuit after starting to apply the charging voltage to the charger. After the storage processing stored in the means and the first suppression control, the second application unit applies a voltage having a larger absolute value than the first suppression control, and after the reverse transfer control, the second application The second suppression control for applying the voltage with the control value stored in the storage unit from the unit and the transfer voltage application control for applying the voltage from the first application unit after the second suppression control are executed.

  According to the image forming apparatus configured as described above, when executing the second suppression control, the control value of the second application unit in the first suppression control performed before the reverse transfer control is used. The current that flows through is immediately stabilized. For this reason, the time required for the second suppression control is shorter than the case where the control for suppressing the inflow current is started from the beginning after the reverse transfer control. Therefore, it is possible to shorten the time from when the print command is input to when the transfer voltage application control is started, that is, the time until printing is started.

  In order to achieve the above-described object, the image forming apparatus control method of the present invention includes a photosensitive member carrying a developer, a charger for charging the photosensitive member, and transferring the developer on the photosensitive member to a transfer medium. A transfer device, a first application unit that applies a voltage having a polarity opposite to that of the charger, and a second application unit that is connected in series to the first application unit and applies a voltage having the same polarity as the voltage of the charger. And an application circuit connected to the transfer device, the image forming apparatus having a control value based on a current flowing in the application circuit after starting to apply the charging voltage to the charger. 1st suppression control which applies a voltage from 2 application parts, the memory processing which memorizes the control value in the 1st suppression control, and the absolute value rather than the time of 1st suppression control from the 2nd application part after the 1st suppression control After the reverse transfer control for applying a large voltage and the reverse transfer control, the second application unit A second suppression control to apply a voltage control value, after the second suppression control, executes a transfer voltage application control to apply a voltage from the first application unit.

  According to the control method of the image forming apparatus configured as described above, when the second suppression control is executed, the control value of the second application unit in the first suppression control performed before the reverse transfer control is used. The current flowing through the application circuit is immediately stabilized. For this reason, the time required for the second suppression control is shorter than the case where the control for suppressing the inflow current is started from the beginning after the reverse transfer control. Therefore, it is possible to shorten the time from when the print command is input to when the transfer voltage application control is started, that is, the time until printing is started.

  According to the present invention, the time until printing is started can be shortened.

1 is a diagram illustrating a schematic configuration of a laser printer according to an embodiment of the present invention. It is a figure which shows the structure of an exposure part. It is a circuit diagram which shows a control part and an application circuit. 6 is a timing chart showing changes in a transport motor, a light source, a BD sensor, a charging voltage, a voltage generated by a transfer bias application circuit, a voltage generated by a reverse bias application circuit, and a current flowing through the application circuit. 6 is a timing chart illustrating changes in a conveyance motor, a light source, a BD sensor, a charging voltage, a voltage generated by a transfer bias application circuit, a voltage generated by a reverse bias application circuit, and a current flowing through the application circuit in a comparative example.

  Next, an embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, after describing the schematic configuration of the laser printer 1 as an example of the image forming apparatus, the characteristic part of the present invention will be described.

  In the following description, the direction will be described with reference to the user who uses the laser printer 1. That is, the right side in FIG. 1 is “front”, the left side is “rear”, the front side is “left”, and the back side is “right”. Also, the vertical direction in FIG.

  As shown in FIG. 1, a laser printer 1 includes a main body casing 2, a paper feed unit 3 that supplies a sheet S as an example of a transfer medium, an exposure unit 5, and a process cartridge that transfers a toner image onto the sheet S. 10, a fixing device 8 that thermally fixes a toner image on the paper S, an application circuit 100, and a conveyance motor M are mainly provided.

  The paper feed unit 3 is provided at a lower portion in the main body casing 2 and mainly includes a paper feed tray 31, a paper pressing plate 32, and a paper feed mechanism 33 including a paper feed roller and the like.

  In the paper feed unit 3, the paper S in the paper feed tray 31 is brought close to a paper feed mechanism 33 provided above by a paper pressing plate 32. The sheet S is supplied to the process cartridge 10 by the sheet feeding mechanism 33.

  The exposure device 5 is a device that exposes the surface of a photosensitive drum 61 as an example of a photosensitive member, and is disposed at an upper portion in the main body casing 2. As shown in FIG. 2, the exposure unit 5 includes a light source 41, a coupling lens 42, an aperture stop 43, a cylindrical lens 44, a polygon mirror 46, a scanning lens 45, a BD sensor 47, and the like. Each of these elements is supported by the housing 4A. Further, the exposure unit 5 includes an exposure unit control unit 48. The light source 41 is, for example, a semiconductor laser. The laser light emitted from the light source 41 passes through the coupling lens 42, the aperture stop 43, the cylindrical lens 44, the polygon mirror 46, and the scanning lens 45 in this order as shown by the chain line and forms an image on the surface of the photosensitive drum 61. The

  The polygon mirror 46 has a plurality of mirror surfaces 46A provided at equal distances from the rotation axis, and each mirror surface 46A rotates at a constant speed around the rotation axis so that the laser light that has passed through the cylindrical lens 44 is reflected. Reflected and deflected in the main scanning direction.

  The BD sensor 47 is disposed at a position where the laser beam reflected by the mirror surface 46A is incident when the angle of the mirror surface 46A of the polygon mirror 46 with respect to the laser beam irradiation direction is a specific angle. The BD sensor 47 outputs a signal to the exposure device controller 48 when detecting the laser beam.

  The exposure device controller 48 is configured to control the light source 41. The exposure device controller 48 causes the light source 41 to output laser light for a predetermined period before outputting laser light for exposure. Then, the exposure device controller 48 determines the timing for outputting the exposure laser beam from the exposure device 5 based on the signal input from the BD sensor 47. Here, the exposure laser beam refers to a laser beam that exposes the surface of the photosensitive drum 61 based on image data.

  As shown in FIG. 1, the process cartridge 10 can be attached to and detached from the main body casing 2 by appropriately opening the front cover 2 </ b> A on the front side of the main body casing 2. The process cartridge 10 is mainly composed of a drum unit 6 and a developing cartridge 7.

  The drum unit 6 mainly includes a photosensitive drum 61, a charger 62, and a transfer roller 63 as an example of a transfer device.

  The photosensitive drum 61 has a cylindrical drum body 61A and a drum shaft 61B that can rotate integrally with the drum body 61A. The drum body 61A has a positively chargeable photosensitive layer on the surface. The drum shaft 61B is made of metal and is grounded.

  The charger 62 is disposed to face the photosensitive drum 61. The charger 62 includes a charging wire 62 </ b> A and a grid electrode 62 </ b> B provided between the charging wire 62 </ b> A and the photosensitive drum 61. A charging voltage application circuit 62C is connected to the charger 62. The charger 62 applies a predetermined charging voltage Vc by the charging voltage application circuit 62C, so that the surface of the photosensitive drum 61 is uniformly charged positively by the discharge from the charging wire 62A.

  The transfer roller 63 includes a roller body 63A and a metal roller shaft 63B that can rotate integrally with the roller body 63A. The transfer roller 63 is disposed to face the photosensitive drum 61. The application circuit 100 is connected to the roller shaft 63B. The transfer roller 63 is configured to transfer the toner on the photosensitive drum 61 onto the paper S when a negative voltage is applied by the application circuit 100.

  The developing cartridge 7 can be attached to and detached from the drum unit 6. The developing cartridge 7 mainly includes a developing roller 18 that extends in the left-right direction, a supply roller 19, a layer thickness regulating blade 14, and a toner container 15 that stores toner as an example of a developer. .

  In the process cartridge 10, the surface of the photosensitive drum 61 is uniformly positively charged by the charger 62 and then exposed by high-speed scanning of the laser light from the exposure device 5. As a result, an electrostatic latent image based on the image data is formed on the surface of the photosensitive drum 61. The toner in the toner storage unit 15 is first supplied to the supply roller 19, charged positively, and supplied from the supply roller 19 to the developing roller 18. As the developing roller 18 rotates, the developing roller 18 enters between the developing roller 18 and the layer thickness regulating blade 14 and is carried on the developing roller 18 as a thin layer having a constant thickness.

  The toner carried on the developing roller 18 is supplied from the developing roller 18 to the electrostatic latent image formed on the photosensitive drum 61. As a result, the electrostatic latent image is visualized and a toner image is formed on the photosensitive drum 61. That is, the photosensitive drum 61 carries toner. Thereafter, the sheet S is conveyed between the photosensitive drum 61 and the transfer roller 63 so that the toner image on the photosensitive drum 61 is transferred onto the sheet S.

  The fixing device 8 is disposed behind the process cartridge 10 and mainly includes a heating roller 8A for heating the paper S on which the toner image is formed by the process cartridge 10, and a pressure roller 8B for pressing the heating roller 8A. ing. In the fixing device 8, the toner image transferred onto the paper S is thermally fixed while the paper S passes between the heating roller 8A and the pressure roller 8B. The paper S on which the toner image is thermally fixed is discharged onto the paper discharge tray 22 by the paper discharge roller 23 and the fixing paper discharge roller 24.

  The transport motor M is connected to the paper feed mechanism 33 and the photosensitive drum 61 and is a drive source that drives the paper feed mechanism 33 and the photosensitive drum 61.

Next, a configuration for applying a voltage to the transfer roller 63 will be described in detail.
As shown in FIG. 3, the laser printer 1 includes, as a configuration for applying a voltage to the transfer roller 63, an application circuit 100, a current detection unit 130, a control unit 210, and a memory 220 as an example of a storage unit. It is mainly equipped with.

  The application circuit 100 includes a transfer bias application circuit 110 as an example of a first application unit, and a reverse bias application circuit 120 as an example of a second application unit. The transfer bias application circuit 110 and the reverse bias application circuit 120 are connected in series to the connection line 90 connected to the roller shaft 63B of the transfer roller 63 in the order of the transfer bias application circuit 110 and the reverse bias application circuit 120.

  The transfer bias application circuit 110 is a circuit that generates a voltage having a polarity opposite to the voltage of the charger 62, that is, a negative voltage Vt, and applies the negative voltage Vt to the transfer roller 63. The transfer bias application circuit 110 includes a transfer bias booster circuit 72 and a first bleeder resistor 78.

  The transfer bias booster circuit 72 includes, for example, a first transformer 75, a first diode 76, and a first smoothing capacitor 77. One end of the secondary coil 75 </ b> A of the first transformer 75 is connected to the connection line 90 via the first diode 76, and the other end is connected to the output terminal of the reverse bias application circuit 120. The first smoothing capacitor 77 and the first bleeder resistor 78 are connected in parallel to the secondary coil 75A of the first transformer 75, respectively. The primary coil 75B of the first transformer 75 is configured such that a current based on the signal S1 output from the PWM port 211 of the control unit 210 flows.

  With such a configuration, the transfer bias applying circuit 110 applies the voltage Vt based on the signal S1 from the control unit 210.

  The reverse bias application circuit 120 is connected in series to the transfer bias application circuit 110, generates a voltage having the same polarity as the voltage of the charger 62, that is, a positive voltage Vb, and applies the positive voltage Vb to the transfer roller 63. Circuit. The reverse bias application circuit 120 includes a reverse bias booster circuit 82 and a second bleeder resistor 88.

  The reverse bias booster circuit 82 includes, for example, a second transformer 85, a second diode 86, and a second smoothing capacitor 87. The secondary coil 85A of the second transformer 85 has one end connected to the other end of the secondary coil 75A of the transfer bias applying circuit 110 via the second diode 86, and the other end connected to the current detection unit 130. Yes. The second smoothing capacitor 87 and the second bleeder resistor 88 are connected in parallel to the secondary coil 85A of the second transformer 85, respectively. The primary coil 85B of the second transformer 85 is configured such that a current based on the signal S2 output from the PWM port 212 of the control unit 210 flows.

  With this configuration, the reverse bias applying circuit 120 applies the voltage Vb based on the signal S2 from the control unit 210.

  By configuring the application circuit 100 as described above, a voltage obtained by adding the voltage Vt generated by the transfer bias application circuit 110 and the voltage Vb generated by the reverse bias application circuit 120 is applied to the transfer roller 63.

  The current detection unit 130 is provided between the application circuit 100 and the ground. The current detection unit 130 is configured by, for example, a resistor Rd, and one end is connected to the reverse bias application circuit 120 and the other end is grounded.

  The current detection unit 130 is configured to transmit the potential at the detection point Pd as a signal S3 from the detection point Pd between the application circuit 100 and the resistor Rd to the A / D port 213 of the control unit 210.

  The control unit 210 includes, for example, a CPU and a memory 220. Further, the control unit 210 includes a PWM port 211 that outputs a signal S1 to the transfer bias application circuit 110, a PWM port 212 that outputs a signal S2 to the reverse bias application circuit 120, and a potential between the application circuit 100 and the resistor Rd. And an A / D port 213 for input. The memory 220 stores an application circuit 100, a charging voltage application circuit 62C, a program for controlling the transport motor M, and the like. The control unit 210 controls the application circuit 100, the charging voltage application circuit 62C, and the transport motor M in accordance with various programs stored in the memory 220.

  Next, a method for controlling the application circuit 100, the charging voltage application circuit 62C, and the transport motor M by the control unit 210 will be described.

  When a print command is input by the user, the controller 210 applies a positive charging voltage Vc to the charger 62 by the charging voltage application circuit 62C. Further, the control unit 210 drives the carry motor M when a print command is input by the user.

  In addition, after starting to apply the charging voltage Vc to the charger 62, the control unit 210 performs first suppression control for generating the voltage Vb from the reverse bias application circuit 120 with a control value based on the current I flowing through the application circuit 100. It is supposed to be.

  Specifically, the control unit 210 executes the first suppression control when the first predetermined time P1 elapses after the charging voltage Vc is applied to the charger 62. In the first suppression control, the control unit 210 changes the control value of the reverse bias application circuit 120 so that the current I flowing through the application circuit 100 becomes the first predetermined value, and uses this control value as the signal S2 to reverse bias. Output to the application circuit 120. The control unit 210 is configured to acquire the current I flowing through the application circuit 100 from the signal S3 based on the potential between the application circuit 100 and the resistor Rd input to the A / D port 213.

  Here, the first predetermined time P <b> 1 in the present embodiment is a time longer than the time required for the surface of the rotating photosensitive drum 61 to move from the position facing the charger 62 to the position facing the transfer roller 63. . The first predetermined time P1 is shorter than the time taken for the surface of the rotating photosensitive drum 61 to move from the position facing the charger 62 to the position facing the transfer roller 63, for example, zero. Also good. In the present embodiment, the first predetermined value is zero.

  Further, the control unit 210 performs a storage process of storing in the memory 220 the control value of the reverse bias application circuit 120 in the first suppression control, that is, the voltage Vb generated by the reverse bias application circuit 120 in the first suppression control. To do. Specifically, the control unit 210 stores the control value of the reverse bias application circuit 120 when the third predetermined time P3 has elapsed since the light source 41 was turned on.

  Here, the exposure device controller 48 emits a laser beam from the light source 41 (turns on the light source 41) when the second predetermined time P2 elapses after the charging voltage Vc is applied to the charger 62, and the BD sensor 47. When the laser beam is detected, initial control for turning off the light source 41 is executed.

  Then, after the first suppression control, the control unit 210 executes reverse transfer control for generating a reverse transfer voltage Vb1 having a larger absolute value than that in the first suppression control from the reverse bias application circuit 120. . Specifically, the control unit 210 performs reverse transfer control when the third predetermined time P3 has elapsed since the light source 41 was turned on. That is, the control unit 210 starts reverse transfer control based on the timing at which the laser beam is output from the exposure device 5.

  The third predetermined time P3 is the same time as the time required for the surface of the rotating photosensitive drum 61 to move from the position exposed by the exposure device 5 to the position facing the transfer roller 63, or from this time. A little short time.

  Further, after the reverse transfer control, the control unit 210 specifically controls the control value in the first suppression control stored in the memory 220 when the fourth predetermined time P4 has elapsed since the light source 41 was turned on. Thus, the second suppression control for generating the voltage Vb in the reverse bias applying circuit 120 is executed. Then, in the second suppression control, the control unit 210 changes the control value of the reverse bias application circuit 120 so that the current I flowing through the application circuit 100 becomes the first predetermined value, that is, zero, and this control value is set to The signal S2 is output to the reverse bias applying circuit 120.

  The fourth predetermined time P4 is a time sufficient for the portion of the photosensitive drum 61 exposed by the exposure device 5 to pass the position facing the transfer roller 63.

  Further, after the second suppression control, the control unit 210 executes transfer voltage application control for generating the voltage Vt from the transfer bias application circuit 110.

  Specifically, after starting the second suppression control, the control unit 210 executes the transfer voltage application control when a fifth predetermined time P5 has elapsed. The fifth predetermined time P5 is a time sufficient for stabilizing the current I flowing through the application circuit 100 set by experiment or the like. When starting the transfer voltage application control, the control unit 210 fixes the control value of the reverse bias application circuit 120. Then, in the transfer voltage application control, the control unit 210 changes the control value of the transfer bias application circuit 110 so that the current I flowing through the application circuit 100 becomes a predetermined current value I1 as an example of the second predetermined value. This control value is output to the transfer bias application circuit 110 as a signal S1.

  The operation and effect of the laser printer 1 configured as described above will be described with reference to the timing chart of FIG.

  When the user inputs a print command, first, the charging voltage Vc is applied to the charger 62 (time t1). As a result, the surface of the photosensitive drum 61 is charged. When the charged portion of the photosensitive drum 61 reaches a position facing the transfer roller 63 due to the rotation of the photosensitive drum 61, the charge on the photosensitive drum 61 starts to move to the transfer roller 63. Therefore, an inflow current flows from the transfer roller 63 to the application circuit 100, and the current I starts to be detected at the detection point Pd.

  When the first predetermined time P1 elapses after the charging voltage Vc starts to be applied to the charger 62 (time t2), the control unit 210 executes the first suppression control (time t2 to t5), and the reverse bias application circuit 120 performs the positive control. The voltage Vb having the value of begins to be generated. As a result, a positive voltage starts to be applied from the application circuit 100 to the transfer roller 63. The voltage Vb generated in the reverse bias application circuit 120 gradually becomes a voltage having a large absolute value, and accordingly, the voltage applied to the transfer roller 63 also increases. As a result, the potential difference between the transfer roller 63 and the surface of the photosensitive drum 61 becomes smaller, so that the charge on the photosensitive drum 61 becomes difficult to move to the transfer roller 63. For this reason, the current I flowing through the application circuit 100 becomes smaller. When the current I flowing through the application circuit 100 becomes zero (time t3), the voltage Vb generated in the reverse bias application circuit 120 becomes substantially constant (time t3 to t5).

  When the second predetermined time P2 elapses after the charging voltage Vc is applied to the charger 62 (time t4), laser light is output from the light source 41. At this time, toner is supplied from the developing roller 18 to a portion exposed on the photosensitive drum 61 by laser light. The portion carrying the toner on the photosensitive drum 61 reaches a position facing the transfer roller 63 after a third predetermined time P3 after the laser light is output from the light source 41. The light source 41 is turned off when the BD sensor 47 detects the laser light (turned on).

  When a third predetermined time P3 elapses after the laser light is output from the light source 41 (time t5), first, a storage process is executed by the control unit 210, and the control value of the voltage Vb generated by the reverse bias applying circuit 120 is determined. (Vb2) is stored in the memory 220.

  Then, reverse transfer control is executed by the control unit 210. When the reverse transfer control is executed, the reverse transfer voltage Vb1 is generated in the reverse bias application circuit 120 (time t5 to t6). As a result, a positive reverse transfer voltage Vb <b> 1 is applied to the transfer roller 63, so that the toner on the photosensitive drum 61 can be prevented from moving to the transfer roller 63. Even when toner has already adhered to the transfer roller 63, the toner moves to the photosensitive drum 61 due to the potential difference between the transfer roller 63 and the photosensitive drum 61.

  When the fourth predetermined time P4 elapses after the laser light is output from the light source 41 (time t6), the exposed portion of the photosensitive drum 61 passes the position facing the transfer roller 63. Then, the control unit 210 executes the second suppression control. When the second suppression control is executed, the control value of the reverse bias application circuit 120 generates the voltage Vb2 at the start of execution of the reverse transfer control stored in the memory 220 from the value that generates the reverse transfer voltage Vb1. Changed to a value. The voltage Vb generated in the reverse bias application circuit 120 is controlled such that the current I flowing through the application circuit 100 becomes zero (time t6 to t7).

  When the fifth predetermined time P5 elapses after the second suppression control is executed (time t7), the transfer voltage application control is executed by the control unit 210. When the transfer voltage application control is executed, the voltage Vb generated by the reverse bias application circuit 120 is fixed to the value at the start of execution of the transfer voltage application control. Then, the transfer bias application circuit 110 starts to generate a negative voltage Vt having a larger absolute value than the voltage Vb generated in the reverse bias application circuit 120 (from time t7). As a result, a negative voltage is applied from the application circuit 100 to the transfer roller 63. When the current I flowing through the application circuit 100 reaches a predetermined current value I1, the voltage Vt generated by the transfer bias application circuit 110 becomes substantially constant.

  As described above, in the transfer voltage application control, the voltage Vb generated in the reverse bias application circuit 120 is fixed to the voltage generated in the second suppression control, and is applied to the transfer roller 63 while suppressing the inflow current. The voltage can be controlled. Therefore, the operation of the application circuit 100 at the time of rising is stabilized.

  Further, when the fifth predetermined time P5 has elapsed since the execution of the second suppression control, the exposure laser beam starts to be output from the light source 41. Thereby, printing is started.

  As described above, the first suppression control, the reverse transfer control, and the second suppression control are executed after the print command is input, thereby suppressing the toner on the photosensitive drum 61 from moving to the transfer roller 63. However, the inflow current can be suppressed and the operation of the application circuit 100 can be stabilized.

  FIG. 5 shows a comparative example of a configuration in which the control unit 210 performs the suppression control for suppressing the inflow current after the reverse transfer control without performing the first suppression control before the reverse transfer control. In this case, when the fourth predetermined time P4 has elapsed after the laser light is output from the light source 41 (time t6), the voltage Vb generated in the reverse bias application circuit 120 becomes zero. Then, the control unit 210 changes the control value of the reverse bias application circuit 120 so that the current I flowing through the application circuit 100 becomes zero. As a result, the voltage Vb generated by the reverse bias application circuit 120 increases, and accordingly, the current I flowing through the application circuit 100 decreases. When the current I flowing through the application circuit 100 becomes zero (time t9), when the fluctuation amount of the current I flowing through the application circuit 100 is less than the predetermined amount continues for the fifth predetermined time P5 (time t10), the control is performed. The transfer voltage application control is executed by the unit 210. In this case, since it takes time until the current I flowing through the application circuit 100 is stabilized after the suppression control is started, the start of printing is delayed compared to the case where the first suppression control is performed before the reverse transfer control.

  In this embodiment, when the first suppression control is performed before the reverse transfer control and the second suppression control is started after the reverse transfer control, the reverse bias application at the start of the reverse transfer control (immediately before the reverse transfer control is performed) By using the control value of the circuit 120, as shown in FIG. 4, the current I flowing in the application circuit 100 immediately stabilizes after the reverse transfer control is completed. Thereby, since the second suppression control can be shortened, the time from when the print command is input to the transfer voltage application control, that is, the time until the start of printing can be shortened.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. About a concrete structure, it can change suitably in the range which does not deviate from the meaning of this invention.

  In the embodiment, the first predetermined value is set to zero as an example, and the reverse bias application circuit 120 is controlled so that the current I flowing through the application circuit 100 is zero in the first suppression control and the second suppression control. 1 The predetermined value is not limited to this. For example, the first predetermined value may be a value other than zero that is smaller than the inflow current.

  In the embodiment, the control unit 210 executes the transfer voltage application control when the predetermined fifth predetermined time P5 has elapsed after starting the second suppression control. The execution timing is not limited to this. For example, after starting the second suppression control, the controller 210 may execute the transfer voltage application control when the current I flowing through the application circuit 100 is stabilized. Whether or not the current I flowing through the application circuit 100 is stable can be determined by whether or not the state in which the amount of change in the current I flowing through the application circuit 100 is less than a predetermined value has continued for a predetermined time.

  In the embodiment, the reverse transfer control is executed after the current I flowing through the application circuit 100 is stabilized in the first suppression control. However, the timing of executing the reverse transfer control is not limited to this. For example, the controller 210 may perform reverse transfer control before the current I flowing through the application circuit 100 is stabilized in the first suppression control.

  In the embodiment, when the second suppression control is executed, the control value of the reverse bias application circuit 120 is set to a value that generates the voltage Vb2 at the start of the reverse transfer control stored in the memory 220. In the second suppression control, the control value of the reverse bias application circuit 120 is set to the value of the reverse transfer control in the second suppression control. You may fix to the value which generate | occur | produces voltage Vb2 at the time of an execution start.

  Moreover, each element of each above-mentioned embodiment and each modification can be implemented in arbitrary combinations.

DESCRIPTION OF SYMBOLS 1 Laser printer 5 Exposure device 61 Photosensitive drum 62 Charging device 63 Transfer roller 100 Application circuit 110 Transfer bias application circuit 120 Reverse bias application circuit 210 Control part 220 Memory Rd Resistance S Paper

Claims (6)

A photoreceptor carrying a developer;
A charger for charging the photoreceptor;
A transfer device for transferring the developer on the photoreceptor to a transfer medium;
A first application unit that applies a voltage having a polarity opposite to the voltage of the charger, and a second application unit that is connected in series to the first application unit and applies a voltage having the same polarity as the voltage of the charger. And an application circuit connected to the transfer device;
Storage means;
A control unit,
The controller is
A first suppression control for applying a voltage from the second application unit at a control value based on a current flowing through the application circuit after starting to apply a charging voltage to the charger;
A storage process for storing the control value in the first suppression control in the storage means;
After the first suppression control, reverse transfer control for applying a voltage having a larger absolute value than the first suppression control from the second application unit;
After the reverse transfer control, a second suppression control for applying a voltage with a control value stored in the storage means from the second application unit;
An image forming apparatus that performs transfer voltage application control for applying a voltage from the first application unit after the second suppression control.   The said control part changes the control value of a said 2nd application part so that the electric current which flows into the said application circuit may become a 1st predetermined value in the said 1st suppression control and the said 2nd suppression control. Item 2. The image forming apparatus according to Item 1.   2. The control unit according to claim 1, wherein, in the transfer voltage application control, the control unit changes a control value of the first application unit so that a current flowing through the application circuit becomes a second predetermined value. The image forming apparatus according to 2. A resistor is provided between the application circuit and ground,
The image forming apparatus according to claim 1, wherein the control unit obtains a current flowing through the application circuit from a potential between the application circuit and the resistor. An exposure device for exposing the surface of the photoreceptor;
5. The image forming apparatus according to claim 1, wherein the control unit starts the reverse transfer control based on a timing at which light is output from the exposure unit. A photosensitive member carrying a developer, a charger for charging the photosensitive member, a transfer unit for transferring the developer on the photosensitive member to a transfer medium, and a voltage having a polarity opposite to that of the charger. An application circuit connected to the transfer unit, the first application unit, and a second application unit connected in series to the first application unit and applying a voltage having the same polarity as the voltage of the charger. A control method of an image forming apparatus provided,
A first suppression control for applying a voltage from the second application unit with a control value based on a current flowing in the application circuit when a charging voltage is applied to the charger;
A storage process for storing a control value in the first suppression control;
After the first suppression control, reverse transfer control for applying a voltage having a larger absolute value than the first suppression control from the second application unit;
A second suppression control for applying a voltage with a control value stored from the second application unit after the reverse transfer control;
After the second suppression control, a transfer voltage application control for applying a voltage from the first application unit is executed.

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