JP2013218166A - Image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to separately adjust an electrical current flowing in the transfer current route of each imaging part in an image formation device having a plurality of imaging parts.SOLUTION: When an image carrier 2a is charged by a charging part 3a, a current It flows in a transfer current route with charges on the image carrier 2a being an electromotive force. The current It is detected from a voltage Vi across a resistor Ri. Impedance of a load Za is calculated from the current It and the primary voltage Vt of a step-up transformer 22. The impedance of loads Zb, Zc, and Zd are calculated in the same way. When the current It is output from the step-up transformer 22, each current flowing in each load is calculated from the current It and the impedance of each load and each current is adjusted to be equal to a target current value output to each load.

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer that forms an image by an electrophotographic process.

  2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus that forms an image on a recording sheet by an electrophotographic process has been widely used. The electrophotographic image forming apparatus includes an image carrier, a charging unit, a developing unit, a transfer unit, and the like as an image forming unit. The image carrier is uniformly charged positively or negatively by the charging unit. Then, an optical image is projected corresponding to the image to be formed, and a charge pattern is generated on the image carrier according to the pattern to obtain an electrostatic latent image. Next, when charged to the opposite polarity to the charge pattern of the latent image, toner as a developer is supplied from the developing unit, and this toner is attracted to the charge pattern of the latent image and developed. Next, the recording paper is superimposed on the toner image, and a charge having the opposite polarity to the charge held by the toner image is applied from the back surface of the recording paper, and the toner image is electrostatically attracted to the recording paper surface and transferred. Thereafter, heat and pressure are applied to the transfer paper to fix the transferred toner image to form an image.

  Here, as a method for transferring a toner image onto a recording paper, there is a roller transfer that applies a direct current voltage to a conductive roller to be charged, and rolls the recording paper while applying an appropriate pressure, thereby applying a charge to the recording paper. . In roller transfer, a high voltage of about several hundred volts to 6 kilovolts is applied to a conductive roller (hereinafter referred to as a transfer roller).

  In a high voltage power source that generates such a high voltage (hereinafter, high voltage), it is known to generate a high voltage using a transformer (Patent Document 1). In addition, when a plurality of high voltage outputs are required, it is also known that a plurality of high voltages are output from one transformer without providing a plurality of transformers, thereby preventing an increase in mounting area due to the provision of a plurality of transformers. ing.

  That is, for example, in Patent Document 2, a high voltage generated by one step-up transformer 17 is divided by a voltage dividing means (resistor 22 and resistor 23) to transfer a transfer electrode (transfer roller) 8 and a cleaning electrode (cleaning roller) 13. A transfer device including a transfer power supply unit that is supplied to the printer is described.

  However, in the transfer power supply unit described in Patent Document 2, the voltage supplied to the transfer electrode 8 (hereinafter, transfer voltage) and the voltage supplied to the cleaning electrode 13 (hereinafter, cleaning voltage) are voltage dividing means. Therefore, there is a problem that individual adjustment cannot be performed.

  Further, the current flowing through the transfer current path, that is, the transfer current Ipc flowing from the transfer electrode 8 to the photosensitive member 1 as the image carrier is detected by the current detection means (resistor 20), and the detection value is driven to become a predetermined value. By driving the step-up transformer 17 by the circuit 16, the constant current control of the current flowing through the transfer current path can be performed, but the constant current control of the current flowing through the cleaning electrode 13 cannot be performed.

  For this reason, for example, in an image forming apparatus having a plurality of image forming units such as a tandem color image forming apparatus, the current flowing through the transfer current path of each image forming unit cannot be individually adjusted. is there.

  The present invention has been made to solve such a problem, and an object of the present invention is to individually separate the current flowing through the transfer current path of each image forming unit in an image forming apparatus having a plurality of image forming units. It is to be able to adjust.

  An image forming apparatus according to the present invention includes a plurality of image forming units each including an image carrier, a charging unit that charges the image carrier, and a transfer unit that transfers an image formed on the image carrier. A transfer power supply unit that outputs a current to the transfer unit; a charging unit control unit that sequentially and exclusively operates the charging units in the plurality of image forming units; and when the transfer power supply unit is not operating, Using the potential of the image carrier charged by operation as an electromotive force, a transfer current flowing through the transfer power source unit, the transfer unit, and a transfer current path passing through the image carrier, and an output of the transfer power source unit accompanying the transfer current Current / voltage detection means for detecting the voltage on the side, load impedance calculation means for calculating the impedance of the load of each transfer current path from the transfer current and voltage detected by the current / voltage detection means, and the load Based on the impedance calculated by the impedance calculating means, an image forming apparatus and a current adjusting means for adjusting the current output from the transfer power source unit to the transfer unit individually.

  According to the present invention, in an image forming apparatus having a plurality of image forming units, the current flowing through the transfer current path of each image forming unit can be individually adjusted.

1 is a diagram illustrating a configuration of an image forming unit in an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a block diagram illustrating a transfer current path, a transfer power supply unit, and a control unit in the image forming apparatus according to the embodiment of the present invention. In the image forming apparatus according to the embodiment of the present invention, it is a diagram showing the connection relationship between the circuit of the transfer power supply unit for calculating the load impedance of the transfer current path, and the load and the control unit. FIG. 4 is a diagram for explaining one transfer current path in FIG. 3. 6 is a timing chart showing a procedure for calculating the load impedance of each transfer current path in the image forming apparatus according to the embodiment of the present invention. In the image forming apparatus according to the embodiment of the present invention, it is a diagram showing the connection relationship between the circuit of the transfer power supply unit for individually adjusting the current flowing through the load, and the load and the control unit. 6 is a flowchart illustrating a first example of an output current adjustment operation of the transfer power supply unit in the image forming apparatus according to the embodiment of the present invention. It is a timing chart of PWM control in FIG. 12 is a flowchart illustrating a second example of the output current adjustment operation of the transfer power supply unit in the image forming apparatus according to the embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<Configuration of image forming unit in image forming apparatus>
FIG. 1 is a diagram illustrating a configuration of an image forming unit in an image forming apparatus according to an embodiment of the present invention.

  As shown in the figure, an endless recording material conveyance belt (hereinafter referred to as a conveyance belt) 5 is wound around two rollers including a driving roller 6 and a driven roller 7 and rotates clockwise in the drawing. Four image forming units of Y (yellow), M (magenta), C (cyan), and K (black) are arranged along the upper running side of the conveyor belt 5. There is no restriction on the order of arrangement of the toner colors of these image forming units.

  Image carriers 2a to 2d made of drum-shaped photosensitive members constituting the image forming units for the respective colors are provided so as to be rotatable in the directions of arrows A1 to A4 (counterclockwise in the drawing), respectively. The transfer rollers 4a to 4d constituting the corresponding transfer unit are provided so as to be in pressure contact with the image carriers 2a to 2d via the conveying belt 5, and charging around the image carriers 2a to 2d is made of a corona discharge device. Portions 3a to 3d, developing devices 1a to 1d, cleaning devices 8a to 8d, lubricating oil supply devices 9a to 9d, and the like are provided. A fixing device 10 is provided on the right side of the driving roller 6 to fix the composite toner image formed on the recording material. A charging roller can also be used as the charging unit.

  In the developing devices 1a to 1d, different color toners are stored in a negatively charged state together with the carrier. When the image carriers 2a to 2d rotate in the directions of arrows A1 to A4, respectively, the surfaces of the image carriers 2a to 2d are uniformly negatively charged by the charging units 3a to 3d. And an electrostatic latent image is formed.

  After the color toners are developed on the image carriers 2a to 2d, the toner images are transferred to the transfer nips formed in the contact areas between the transfer rollers 4a to 4d and the image carriers 2a to 2d to which a positive voltage and pressure are applied. The image is transferred onto the recording material P that is carried and conveyed by the conveyor belt 5 in and near the area.

  The composite toner image in which the four color toner images are formed on the recording material P in a superimposed manner is fixed on the recording material P by the fixing device 10. The toner remaining on the image carriers 2a to 2d is collected and reused by the cleaning devices 8a to 8d. A certain amount of lubricating oil is supplied onto the image carriers 2a to 2d from the lubricant oil supply devices 9a to 9d, and the static friction coefficients on the surfaces of the image carriers 2a to 2d are kept constant.

<Transfer current path>
FIG. 2 is a block diagram illustrating a transfer current path, a transfer power supply unit, and a control unit in the image forming apparatus according to the embodiment of the present invention.

  As shown in the figure, the output of the transfer power supply unit 20 is connected in common to the transfer rollers 4a to 4d of the image forming units of the respective colors. The input of the transfer power supply unit 20 is connected in common to the image carriers 2a to 2d of the image forming units for the respective colors. That is, a transfer current path is formed from the transfer power supply unit 20 to the transfer power supply unit 20 via the transfer rollers 4a to 4d and the image carriers 2a to 2d.

  The transfer power supply unit 20 generates a high voltage and supplies transfer currents Ia to Id in parallel to the transfer rollers 4a to 4d of the image forming units of the respective colors. The transfer currents Ia to Id return to the transfer power supply unit 20 through a transfer current path passing through the image carriers 2a to 2d. The transfer currents Ia to Id that have returned to the transfer power supply unit 20 are individually detected in the transfer power supply unit 20, converted into a corresponding voltage Vi, and input to the control unit 30.

  The control unit 30 includes a CPU (Central Processing Unit) 31, a ROM (Read Only Memory) 32, and a RAM (Random Access Memory) 33. The CPU 31 uses a program and related data stored in the ROM 32, and the RAM 33 1 is controlled as a work area to control the entire image forming unit shown in FIG. Here, PWM (Pulse Width Modulation) control for the transfer power supply unit 20 and operation control for the charging unit 3a are illustrated. Details of these controls will be described later. Means such as a charging unit control unit and a load impedance calculation unit according to the present invention correspond to the function of the control unit 30.

<Configuration of the part that calculates the impedance of the load>
FIG. 3 is a diagram illustrating a connection relationship between the circuit of the transfer power supply unit for calculating the load impedance of the transfer current path and the load and the control unit in the image forming apparatus according to the embodiment of the present invention.

  In the figure, a portion other than the control unit 30, the loads Za to Zd, and the diodes Da to Dd is a transfer power supply unit 20. The transfer power supply unit includes a drive circuit 21, a step-up transformer 22, and a current detection resistor Ri. The rectifying / smoothing diode and capacitor on the output side of the step-up transformer 22 are omitted.

  Here, the load Za corresponds to the transfer roller 4a and the image carrier 2a. Similarly, the loads Zb, Zc, and Zd correspond to the transfer roller 4b and the image carrier 2b, the transfer roller 4c and the image carrier 2c, the transfer roller 4d, and the image carrier 2d, respectively.

  The output current It output from the secondary winding of the step-up transformer 22 is divided into transfer currents Ia to Id flowing through the loads Za to Zd, respectively. The current that passes through the loads Za to Zd passes from the diodes Da to Dd connected in series to the loads, passes through the ground (GND), returns to the secondary side winding of the step-up transformer 22 through the current detection resistor Ri.

  Since the current flowing through the current detection resistor Ri is the sum of the transfer currents Ia to Id flowing through the loads Za to Zd, it is equal to the output current It output from the secondary winding of the step-up transformer 22.

  Therefore, a voltage Vi proportional to the output current It is generated by the current detection resistor Ri, and is sent to the control unit 30 as a feedback voltage. The control unit 30 controls the on / off duty of the PWM output of the drive circuit 21 so that the voltage Vi becomes a preset target value, whereby the output voltage Vt of the drive circuit 21 (= the boost transformer 22). Variable control of the primary side input voltage).

  Here, if the impedances of the loads Za to Zd are the same, an It / 4 current flows through each load. Therefore, in order to flow a target current (current to be passed through each load) to each load, one load The PWM output of the drive circuit 21 may be controlled so that a current that is four times the target current of the load is output from the step-up transformer 22.

  However, if the impedance of each load is different, there is a difference in the current flowing through each load due to the difference. Therefore, in order to flow the target current through each load, the current flowing through each load is detected and each becomes the target current. Thus, it is necessary to adjust the current flowing through each load.

  Therefore, in the present embodiment, when the impedances of the loads Za to Zd are calculated and a predetermined current is supplied from the transfer power supply unit 20 in parallel to the loads Za to Zd, the current flowing through the loads Za to Zd is changed to the loads Za to Zd. Calculation is performed from the impedance of Zd, and control is performed so that the calculated current becomes the target current.

  First, in addition to the configuration in which the diodes Da to Dd are inserted in the lines of the loads Za to Zd, the impedances of the loads Za to Zd are calculated using the current flowing through the transfer current path due to the charges on the image carriers 2a to 2d.

<Procedure for calculating the impedance of each load>
FIG. 4 is a diagram for explaining one transfer current path in FIG. 3, and FIG. 5 is a timing chart showing a procedure for calculating the load impedance of each transfer current path. The procedure for calculating the impedances of the loads Za to Zd will be described with reference to these drawings.

  As shown in FIG. 4, the load Za has a configuration in which a transfer roller 4a and an image carrier 2a are connected in series. Although not shown, the loads Zb, Zc, and Zd also have a configuration in which the transfer roller 4b and the image carrier 2b are connected in series, a configuration in which the transfer roller 4c and the image carrier 2c are connected in series, and the transfer roller 4d. And the image carrier 2d are connected in series.

  Here, when the image carrier 2a is negatively charged by the charging unit 3a, the image carrier 2a is charged to a potential corresponding to the amount of charge. When the image carrier 2a rotates as indicated by the arrow A1 and the charged portion reaches the transfer portion (contacts the transfer roller 4a), the potential becomes an electromotive force, and even when no high voltage is output from the step-up transformer 22, FIG. As indicated by the one-dot chain arrow in FIG.

  Since this current is due to the electromotive force generated in the load Za, no current flows to the other loads Zb, Zc, Zd by the diodes Db, Dc, Dd. Therefore, since all the current flowing through the load Za flows into the transfer power supply unit, the transfer current Ia flowing through the load Za is equal to the current It flowing through the current detection resistor Ri. Therefore, the transfer current Ia can be grasped by detecting (measuring) It. If the voltage (Vt) of the primary side winding of the step-up transformer 22 is detected at that time, the impedance of the load Za can be calculated from the relationship between the current It and the voltage Vt.

  Similarly, for the loads Zb, Zc, and Zd, the image bearing members 2b, 2c, and 2d are charged by the charging units 3b, 3c, and 3d, and the load is generated by the electromotive force generated by the charging potential on the image carriers 2b, 2c, and 2d. By detecting the current flowing through Zb, Zc, Zd and the voltage (Vt) of the primary side winding of the step-up transformer 22 at that time, the impedance of the loads Zb, Zc, Zd is calculated from the relationship between the current It and the voltage Vt. Can do.

  Specifically, as shown in FIG. 5, the charging units 3 a to 3 d exclusively perform charging outputs Ca to Cd in this order to charge the image carriers 2 a to 2 d.

  When a certain delay time elapses from the timing of the charging outputs Ca to Cd, the charged portions of the image carriers 2a to 2d reach the transfer current path, and the transfer currents Ia to Id flow. By detecting these by the current detection resistor Ri and simultaneously detecting the voltage (Vt) of the primary winding, the loads Za to Zd can be calculated in order.

<Configuration of the part that individually adjusts the current flowing through each load>
FIG. 6 is a diagram showing a connection relationship between the circuit of the transfer power supply unit for individually adjusting the current flowing through each load, and the load and the control unit. In this figure, the same reference numerals as those in FIG. 3 are assigned to the same or corresponding parts as those in FIG.

  As illustrated, the transfer power supply unit includes shunt circuits 23a to 23d for individually adjusting currents flowing through the loads Za to Zd. In addition, the control unit 30 outputs PWM_a to PWM_d for controlling the current flowing through the shunt circuits 23a to 23d.

  The shunt circuit 23a is composed of a series connection circuit of a resistor R1a, a transistor Tra, and a resistor R2a connected between the output side and the input side of the secondary winding of the step-up transformer 22, and a PWM signal is connected to the base of the transistor Tra. Is input, and a load Za is connected to the collector of the transistor Tra.

  In the shunt circuit 23a, by increasing / decreasing the on / off duty of PWM_a, out of the current flowing into the resistor R1a, the shunt current Ia ′ flowing through the resistor R2a through the transistor Tra is increased / decreased to flow to the load Za. The transfer current Ia can be adjusted.

  The shunt circuits 23b, 23c, and 23d are configured similarly to the shunt circuit 23a and operate in the same manner.

<Individual adjustment of output current for each load>
Next, a procedure for individually adjusting the output currents for the loads Za to Zd in the transfer power supply unit shown in FIG. 6 will be described. In the present embodiment, the adjustment is possible even if the target value (target current) of the output current for each load is the same or different.

<< When the target value of the output current for each load is the same >>
FIG. 7 is a flowchart showing a first example of the output current adjustment operation of the transfer power supply unit in the image forming apparatus according to the embodiment of the present invention, that is, the adjustment procedure when the target value of the output current for each load is the same.

  First, transfer output is performed by controlling the drive circuit 21 so that the total (It) of the target value of the output current for each load is output from the step-up transformer 22 (step S1). Next, from the impedances of the loads Za to Zd calculated by the procedure described with reference to FIGS. 4 and 5 and the value of the current It detected when the transfer output is performed in step S1 (step S2), the loads Za to Currents flowing through Zd (transfer currents Ia to Id) are calculated (step S3).

  These currents are derived by Ohm's law as shown in the following equations [1] to [4]. In these equations, Za to Zd are impedances of the loads Za to Zd.

Ia = Zb · Zc · Zd / (Za · Zb · Zc + Za · Zb · Zd + Za · Zc · Zd + Zb · Zc · Zd) · It (1)
Ib = Za · Zc · Zd / (Za · Zb · Zc + Za · Zb · Zd + Za · Zc · Zd + Zb · Zc · Zd) · It (2)
Ic = Za · Zb · Zd / (Za · Zb · Zc + Za · Zb · Zd + Za · Zc ·
Zd + Zb · Zc · Zd) · It (3)
Id = Za · Zb · Zc / (Za · Zb · Zc + Za · Zb · Zd + Za · Zc · Zd + Zb · Zc · Zd) · It (4)

  The minimum value I of the transfer currents Ia to Id is compared with the target value of the output current to determine whether or not they match (step S4). As a result of the determination, if they do not match, that is, lower than the target value (step S4: No), correction is performed so as to increase the output of the step-up transformer 22 (step S5).

  If they are equal (step S4: Yes), the output of the other channel (ch) (other than the minimum value of the transfer currents Ia to Id) exceeds the target value, so the current is adjusted by the shunt circuit. (Step S6).

  FIG. 8 is a timing chart showing the procedure of step S6 in FIG. As shown in the figure, the shunt currents Ia 'to Id' are adjusted exclusively and sequentially for the shunt circuits 23a to 23d. For convenience, the operation of adjusting the four shunt currents Ia 'to Id' is shown here for the sake of convenience. However, adjustment is required for three currents flowing through the load exceeding the target value.

  On the circuit of FIG. 6, for example, in the case of the load Za, by dividing Ia ', the current flowing through the current detector (Ri) is reduced by this Ia'. Therefore, the decrease (i_) in the current detection resistor Ri is detected (step S7), and it is determined whether or not the difference between Ia before the diversion control and the target value is equal to the decrease (i_) (step S8). ).

  If they are not equal (step S8: No), the adjustment of the PWM on / off duty is repeated so as to be equal (step S6). If they are equal (step S8: Yes), the difference is divided and the target current flows to the load.

  Similarly, control is performed for the outputs of other channels so that the current flowing through the load becomes the target value, and when the currents flowing through all other loads are equal to the target value, the processing shown in this figure is terminated. To do.

<When output current target value for each load is different>
FIG. 9 is a flowchart showing a second example of the output current adjustment operation of the transfer power supply unit in the image forming apparatus according to the embodiment of the present invention, that is, the adjustment procedure when the target value of the output current for each load is different. Here, the target values of the output current for the loads Za to Zd are respectively IA to ID.

  As in the case where the target values are equal, first, the transfer circuit 22 controls the drive circuit 21 so that the total of the target values (It) of the output current for each load is output from the step-up transformer 22, and then performs the transfer output. The currents (transfer currents Ia to Id) flowing through the loads are similarly calculated from the impedances of the loads Za to Zd calculated in the above procedure and the value of the current It detected when the transfer output is performed. The illustration of these procedures is omitted.

  Next, the calculated transfer currents Ia to Id are compared with the target values IA to ID, and the process of increasing the output of the step-up transformer 22 is repeated until they become equal. That is, first, it is determined whether or not the transfer current Ia is greater than or equal to the target value IA (step S11). If the transfer current Ia is smaller than the target value IA (step S11: No), the output of the step-up transformer 22 is increased. (Step S12) The transfer currents Ia to Id are calculated again (Step S13), and it is determined whether or not the transfer current Ia is equal to or greater than the target value IA (Step S11).

  When the transfer current Ia becomes equal to the target value IA (step S11: Yes), the transfer current Ib is processed in the same manner as the transfer current Ia. That is, it is first determined whether or not the transfer current Ib is greater than or equal to the target value IB (step S14). As a result of the determination, if the transfer current Ib is smaller than the target value IB (step S14: No), the output of the step-up transformer 22 is increased (step S15), and the transfer currents Ia to Id flowing through the loads corresponding to the output are again set. It is calculated (step S16), and it is determined whether or not the transfer current Ib is equal to or greater than the target value IB (step S14).

  As a result of increasing the output of the step-up transformer 22, if the transfer current Ib becomes equal to the target value IB (step S14: Yes), the process proceeds to step S17. If the transfer current Ib is greater than or equal to the target value IB as a result of the determination in the first step S14 that has shifted from step S11, the process proceeds directly to step S17.

  Here, in the case of the former, that is, in the order of S11: Yes → S14: No → S15 → S16 → S14: Yes → S17, the result of performing the output increase in S15 in order to make the transfer current Ib equal to the target value IB. The transfer current Ia is larger than the target value IA. On the other hand, in the latter case, that is, in the order of S11: Yes → S14: Yes → S17, the transfer current Ib is larger than the target value IB, and the transfer current Ia is equal to the target value IA.

  In steps S17 to S19, the transfer current Ic is processed in the same manner as the transfer current Ib. In steps S20 to S22, the transfer current Id is processed in the same manner as the transfer currents Ib and Ic.

  In Step S20: Yes, the transfer current Ia to Id having the maximum target value is equal to the target value, and the currents flowing through the other loads are larger than the respective target values.

  Therefore, steps S23 to S25 are executed in order to reduce the current flowing through the load that has become larger than the target value. Steps S23 to S25 are the same as steps S6 to S8 in FIG. In other words, the on / off control of the transistors Tra to Trd of each of the shunt circuits 23a to 23d is performed exclusively and sequentially, thereby adjusting the shunt currents Ia 'to Id' in each of the shunt circuits 23a to 23d.

  For example, in the case of the load Za, by dividing Ia '(step S23), the current flowing through the current detection resistor Ri decreases by this Ia'. Therefore, a decrease (i_) in the current detection resistor Ri is detected (step S24), and it is determined whether or not the difference between the transfer current Ia before the diversion control and the target value IA is equal to the decrease (i_). (Step S25).

  If they are not equal (step S25: No), the adjustment of the PWM on / off duty is repeated so as to be equal (step S23). If they are equal (step S25: Yes), the difference is divided and the target current flows to the load.

  Similarly, control is performed for the outputs of other channels so that the current flowing through the load becomes the target value, and when the currents flowing through all other loads are equal to the target value, the processing shown in this figure is terminated. (Step S25: Yes).

  Thus, according to the image forming apparatus according to the embodiment of the present invention, the currents flowing through the loads Za to Zd can be individually adjusted. The calculation of the impedances of the loads Za to Zd and the individual current adjustment are preferably performed before the transfer operation when the set transfer current changes due to changes in the paper type, environmental temperature, or the like.

  In FIG. 9, in S11 to S20, the transfer currents Ia to Id are sequentially compared with the target values and individually processed so as to be equal to or higher than the target values. Of the transfer currents Ia to Id, the target value is Only the maximum load current can be processed to be equal to the target values IA to ID.

  2a to 2d ... image carrier, 3a to 3d ... charging unit, 4a to 4d ... transfer roller, 20 ... transfer power supply unit, 21 ... drive circuit, 22 ... step-up transformer, 23a-23d ... shunt circuit, 30 ... control unit, Ri: current detection resistor, Da to Dd: diode, Za to Zd: load.

JP 2006-65113 A JP-A-11-73032 (FIG. 1)

Claims (6)

A plurality of image forming units each having an image carrier, a charging unit for charging the image carrier, and a transfer unit for transferring an image formed on the image carrier;
A transfer power supply unit that outputs a current to each transfer unit;
Charging unit control means for sequentially and exclusively operating the charging units in the plurality of image forming units;
When the transfer power supply unit is not operating, a transfer current path passing through the transfer power supply unit, the transfer unit, and the image carrier using the potential of the image carrier charged by the operation of the charging unit as an electromotive force Current / voltage detection means for detecting a transfer current flowing through the output current and a voltage on the output side of the transfer power supply unit accompanying the transfer current;
Load impedance calculation means for calculating the impedance of the load of each transfer current path from the transfer current and voltage detected by the current / voltage detection means;
Current adjusting means for individually adjusting the current output from the transfer power supply unit to each transfer unit based on the impedance calculated by the load impedance calculation unit;
An image forming apparatus comprising: The image forming apparatus according to claim 1,
The current adjustment unit calculates a current flowing through each transfer current path based on the impedance of each transfer current path calculated by the load impedance calculation unit when the transfer power supply unit outputs an arbitrary current. Current calculating means for controlling the current output to each transfer section so that the current flowing through each transfer current path calculated by the current calculation means is equal to the target current output to each transfer section; And an image forming apparatus. The image forming apparatus according to claim 2,
The current control unit controls the output voltage of the transfer power supply unit so that a predetermined one of the currents flowing through the transfer current paths calculated by the current calculation unit is equal to a target current. And an individual current control unit that individually controls a current output to each transfer unit so that all currents other than the predetermined one current become a target current. The image forming apparatus according to claim 3.
The image forming apparatus in which the predetermined one current is the smallest current among the currents flowing through the transfer current paths calculated by the current calculation unit. The image forming apparatus according to claim 1,
An element is inserted between the image carrier and the transfer power supply unit in each transfer current path to prevent a current generated by the electric charge on the image carrier from flowing toward another image carrier. Image forming apparatus. The image forming apparatus according to claim 1,
The transfer power supply unit includes a drive circuit that generates a PWM waveform, and a transformer that boosts the output of the drive circuit, and a secondary winding of the transformer constitutes the transfer current path, and The voltage detection unit is an image forming apparatus that detects a current flowing through the secondary side winding and detects a voltage from the primary side winding of the transformer.

Images