JP2016045409A - Image forming apparatus, control method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that has a plurality of charging wires applied with a charging voltage, and to achieve processing on both the charging voltage and a grid voltage to stabilize the processing, and thereby converting a grid voltage into a constant voltage.SOLUTION: A printer calculates a grid current Ig1 flowing in a grid of a reference object. The printer controls a charged voltage creation circuit so that the calculated grid current Ig1 has a predetermined current value (S21 to S27). The printer executes, to a charger, processing of reducing each of grid voltages GRID2 to GRID4 so that the current values of grid currents Ig2 to Ig4 becomes smaller than a predetermined value (S29 to S39). The printer executes processing of changing the grid voltages GRID2 to GRID4 (S27, S31, S35, and S39) before executing processing of changing a charged voltage CHG.SELECTED DRAWING: Figure 4

Description

  The technique disclosed in the present invention is a technique related to a process of supplying a charging voltage to a plurality of charging wires that charge each of a plurality of photosensitive members included in an image forming apparatus.

  2. Description of the Related Art Conventionally, there is an image forming apparatus in which a plurality of charging wires for charging each of a plurality of photoconductors corresponding to each color are provided, and a charging voltage is supplied to one power line in which the plurality of charging wires are connected in parallel ( For example, Patent Document 1). The image forming apparatus disclosed in Patent Document 1 supplies a high charging voltage to a plurality of charging wires from one charging voltage generation circuit. In addition, the image forming apparatus includes a plurality of grids corresponding to the respective charging wires, and a grid constant voltage circuit that controls the grid voltage generated in each of the plurality of grids to be a predetermined value. The image forming apparatus applies a voltage to the charging wire and the grid when forming an image, so that an electric field is formed between the charging wire and the photoconductor to generate a corona discharge, thereby uniformly correcting the surface of the photoconductor. Charge. In addition, for example, the image forming apparatus uses a grid with the smallest generated grid current among a plurality of grids as a reference target, and sets a charging voltage according to the current value of the grid current of the reference target grid. It has changed.

JP 2012-48032 A

  However, for example, foreign substances such as silica contained in the toner may adhere to each of the plurality of charging wires, and the amount and form of the foreign substances may be different for each charging wire. The current will be different for each charged wire. If the discharge current is different, a difference occurs in the surface potential of the photoconductor, which may affect image formation. On the other hand, Patent Document 1 shows that the grid voltage is lowered when the grid current is large. However, if the control of the grid voltage and the current of the charging wire are simultaneously controlled, the processing may become unstable.

  More specifically, for example, it is assumed that the grid current (voltage) of an arbitrary grid other than the reference target grid is reduced due to the adhesion of foreign matter. On the other hand, for example, the image forming apparatus executes control or the like for increasing the reference voltage of the grid constant voltage circuit corresponding to the arbitrary grid so as to control the grid voltage to be a predetermined value. As a result, the grid current of an arbitrary grid increases. On the other hand, as long as the charging voltage applied to the common power supply line is maintained at a constant value, the grid voltage (grid current) of an arbitrary grid increases, and the other power supply line connected to the power supply line In the grid, the grid current fluctuates. Since the other grid includes the reference target grid, the image forming apparatus changes the magnitude of the charging voltage in accordance with the fluctuation of the grid current of the reference target grid. In other words, in the image forming apparatus described above, if the process for the charging voltage using the reference target grid and the process for the grid voltage in an arbitrary grid are independently executed under each condition, the processing results interfere with each other. There is a problem that there is a risk of becoming unstable.

  The present application has been proposed in view of the above-described problems. In a configuration in which a charging voltage is applied to a plurality of charging wires, the processing for charging voltage and grid voltage is made compatible and the processing is stabilized. An object of the present invention is to provide an image forming apparatus capable of making the grid voltage constant, a control method for the image forming apparatus, and a program.

  An image forming apparatus made to solve the above problems includes a plurality of photosensitive members, a plurality of charging wires, and a charging voltage applying unit that is connected to each of the plurality of charging wires and applies a charging voltage to the plurality of charging wires. A grid provided between the photosensitive member and the charging wire, an image forming unit that forms an image on a plurality of photosensitive members, a grid voltage adjusting unit that adjusts the grid voltage of the grid, and a grid current that flows through the grid. A current detection circuit for detecting, and a control unit, wherein the control unit uses at least one grid among a plurality of grids as a reference target, and uses a current detection circuit to detect a grid current flowing in the reference target grid. Current detection processing to detect, charging voltage change processing to change the charging voltage based on the detection result of the current detection processing, and grid voltage change to change the grid voltage In performing a physical, and based on the detection result of the changed current detection processing by executing the grid voltage changing process, it executes the charging voltage changing process.

  In addition, the control unit performs current detection processing on a plurality of current detection circuits, and the current detection processing detects a grid current flowing in at least one grid among other grids excluding the grid to be referred to. In the grid voltage changing process, the grid voltage generated in the other grid is changed based on the detection result of the grid current flowing in the other grid.

  In the grid voltage changing process, the grid voltage is changed for all other grids.

  In addition, the control unit executes a reference target switching process for switching the reference target grid to another grid excluding the reference target grid.

  In addition, the control unit executes a reference target setting process for setting a grid having a minimum grid current as a reference target among the plurality of grids.

  In addition, the control unit repeatedly executes the charging voltage changing process and the grid voltage changing process repeatedly, and repeatedly executes the grid voltage to be changed in the grid voltage changing process while switching the grid.

  The image according to any one of claims 1 to 6, wherein the grid voltage changing process reduces the grid voltage generated in the grid as the grid current flowing in the grid increases. Forming equipment.

  Further, the control unit executes a notification process for notifying an error in response to the magnitude of the grid voltage being smaller than the predetermined value.

  The control unit executes at least one of the grid voltage changing process and the charging voltage changing process according to the timing when the image forming unit does not form an image.

  In addition, an image forming apparatus control method made to solve the above problems is connected to each of a plurality of photosensitive members, a plurality of charging wires, and a plurality of charging wires, and a charging voltage is applied to the plurality of charging wires. A charging voltage applying unit, a grid provided between the photosensitive member and the charging wire, an image forming unit that forms an image on a plurality of photosensitive members, a grid voltage adjusting unit that adjusts a grid voltage of the grid, and a grid A control method for an image forming apparatus comprising a current detection circuit that detects a grid current flowing through the control circuit, and a control unit, wherein at least one of the plurality of grids is a reference target, and the reference target grid A current detection process for detecting a flowing grid current using a current detection circuit; a charging voltage change process for changing a charging voltage based on a detection result of the current detection process; In performing the grid voltage changing process for changing a lid voltage, and based on the detection result of the changed current detection processing by executing the grid voltage changing process, it executes the charging voltage changing process.

  An image forming apparatus program for solving the above problems is connected to a plurality of photosensitive members, a plurality of charging wires, and a plurality of charging wires, and applies a charging voltage to the plurality of charging wires. A charging voltage applying unit, a grid provided between the photosensitive member and the charging wire, an image forming unit that forms an image on a plurality of photosensitive members, a grid voltage adjusting unit that adjusts a grid voltage of the grid, and a grid A program for controlling an image forming apparatus comprising a current detection circuit for detecting a flowing grid current and a control unit, wherein the image forming apparatus has at least one grid as a reference target and the reference Based on the current detection process that detects the grid current flowing in the target grid using the current detection circuit and the detection result of the current detection process, the charging voltage is The charging voltage changing process is performed based on the detection result of the current detection process that has been changed by executing the grid voltage changing process when executing the charging voltage changing process to be changed and the grid voltage changing process to change the grid voltage. Let it run.

  According to the present invention, the control unit executes a current detection process of detecting the grid current flowing through the reference target grid using the current detection circuit. Further, the control unit executes a charging voltage changing process for changing the charging voltage applied to the plurality of charging wires based on the detection result of the current detecting process. Further, the control unit executes a grid voltage changing process for changing the grid voltage generated in each of the plurality of grids. Then, the control unit executes the charging voltage changing process based on the detection result of the current detecting process that is changed by executing the grid voltage changing process when executing each of the above-described processes. Therefore, on the condition that the image forming apparatus follows a processing procedure that, when the grid current is changed by executing the grid voltage changing process, the charging voltage changing process corresponding to the changed grid current is always executed. Two processes are performed. For this reason, in the image forming apparatus, it is possible to eliminate the instability of the process as compared with the case where the grid voltage changing process and the charging voltage changing process are performed independently and freely, and the two processes are compatible. Thus, the charging voltage and the grid voltage can be made constant.

  In addition, the control unit executes current detection processing for a plurality of current detection circuits, and executes current detection processing for detecting a grid current flowing in at least one of the grids other than the reference target grid. To do. Further, the control unit executes a grid voltage change process for changing the grid voltage generated in the other grid based on the detection result of the grid current flowing in the other grid. In such a configuration, the image forming apparatus performs the grid voltage changing process on the grid other than the reference target, so that even if the grid current of the reference target grid is changed, the charging voltage changing process is performed thereafter. By following the processing procedure to be executed, the grid voltage can be made constant.

  In addition, even if the grid current of the grid to be referred to is changed by executing the grid voltage changing process for all the grids other than the reference target, the image forming apparatus executes the charging voltage changing process thereafter. By following the processing procedure, the grid voltage can be made constant.

  In addition, the control unit switches the reference grid. Here, when the reference target grid is fixed, for example, it is assumed that a foreign matter such as silica contained in the toner adheres to the charging wire corresponding to the reference target grid and the grid current decreases. Then, the control unit may increase the charging voltage excessively in accordance with the decrease in the grid current. In other words, when the reference target grid is fixed, the charging voltage change processing depends greatly on the state of the reference target. On the other hand, according to the image forming apparatus, a grid voltage constant voltage can be obtained by switching the grid to be referred to according to appropriate conditions and timing (for example, when the charging voltage exceeds a desired value). It becomes possible to execute the process of conversion more stably.

  In addition, the control unit sets, as a reference target, a grid having a minimum grid current among the plurality of grids. In the grid, for example, the grid current decreases as the amount of foreign matter such as silica attached to the corresponding charging wire increases. Therefore, it can be assumed that the charging wire corresponding to the grid having the smallest grid current is the most dirty of the plurality of charging wires. Therefore, in such a configuration, the photosensitive member can be sufficiently charged by the most dirty charging wire by using the grid having the smallest grid current as a reference object.

  In addition, the control unit repeatedly executes the charging voltage changing process and the grid voltage changing process repeatedly, and repeatedly executes the grid voltage to be changed in the grid voltage changing process while switching the grid. In such a configuration, it is possible to more stably execute the grid voltage constant voltage process by sequentially switching the grids to be subjected to the grid voltage change process.

  Further, the control unit reduces the grid voltage generated in the grid as the grid current flowing in the grid increases. In general, as the grid current increases, the surface potential of the photoconductor increases. Therefore, the controller reduces the surface potential of the photoconductor by reducing the grid voltage as the grid current increases. It is possible to suppress the deterioration of image quality.

  In addition, when the grid voltage is smaller than a predetermined value, for example, a lower limit value of a range allowed to maintain image quality, an error is notified to the user to It is possible to promote cleaning and to request judgment.

  Further, at least one of the grid voltage changing process and the charging voltage changing process is executed according to the timing when the image forming unit does not form an image. In such a configuration, it is possible to suppress the influence of the fluctuation of the grid voltage caused by the grid voltage changing process and the fluctuation of the charging voltage caused by the charged voltage changing process on the image quality.

  Further, according to the control method of the image forming apparatus, it is possible to obtain the same effect as the image forming apparatus according to claim 1. Similarly, according to the program of the image forming apparatus, it is possible to obtain the same effect as the image forming apparatus according to claim 1.

It is sectional drawing which shows schematic structure of the color laser printer of embodiment. FIG. 2 is a schematic block diagram relating to a high-voltage power supply device for a printer. It is a flowchart for demonstrating control operation of constant voltage. It is a flowchart for demonstrating control operation of constant voltage.

  Hereinafter, an embodiment of the present application will be described with reference to the drawings. A laser printer 1 (an example of an image forming apparatus) that is an embodiment of an image forming apparatus according to the present application illustrated in FIG. 1 is a color laser printer that forms a color image on a sheet P or the like by an electrophotographic method. This is a so-called tandem laser printer using toner. In the following description, as shown in FIG. 1, the right side of the drawing is defined as the front side of the laser printer 1 (hereinafter simply referred to as “printer”), and the left side of the drawing is defined as the rear side. 1 is defined as a left side when the front side of the printer 1 is viewed from the front side of the printer 1, and a rear side of the page is defined as a right side. 1 is defined as the upper side of the printer 1 and the lower side of the page is defined as the lower side.

  As shown in FIG. 1, the printer 1 has a substantially box-shaped main body housing 2, and a paper feeding unit 10, an image forming unit 20, and the like are housed inside the main body housing 2. A discharge tray 5 is provided on the upper surface of the main body housing 2 to store the sheets P on which images are formed in a stacked state. The paper feed unit 10 includes a paper feed tray 11 in which the paper P is accommodated and various rollers, and drives the various rollers to feed the paper P to the image forming unit 20. The paper feed tray 11 is configured to be detachable from the lower portion of the main body housing 2.

  The image forming unit 20 includes a transport unit 21, four process cartridges 30C, 30M, 30Y, and 30K, an exposure unit 35, and a fixing unit 50. The transport unit 21 is provided between the paper feed unit 10 and the process cartridge 30C in the vertical direction, and includes a transport belt 23, four transfer rollers 25, and the like. The conveying belt 23 is an endless belt configured by making the belt into an annular shape, and is wound around a driving roller 27 positioned below the rear end side of the image forming unit 20 and a driven roller 29 positioned below the front end side. The upper surface of the conveyor belt 23 extends substantially horizontally just below the process cartridge 30C and the like, and comes into contact with the back surface of the paper P supplied from the paper supply unit 10. The driving roller 27 rotates the transport belt 23 in a predetermined direction. Further, the transport belt 23 is negatively charged by applying a transfer bias to each transfer roller 25, and the sheet P is sucked to the upper surface by electrostatic force, while the sucked sheet P is discharged along the transport path R to the discharge tray. Convey toward 5

  Each of the process cartridges 30C, 30M, 30Y, and 30K corresponds to four colors of cyan (C), magenta (M), yellow (Y), and black (K). Each of the process cartridges 30C and the like accommodates toner of corresponding colors (C, M, Y, K). The four process cartridges 30C and the like are provided in the order of process cartridges 30K, 30Y, 30M, and 30C from the front to the rear of the printer 1.

  The process cartridge 30C includes a photoreceptor drum 31 (an example of a photoreceptor), a charger 41, a toner cartridge 33, and the like. The other process cartridges 30M, 30Y, and 30K have different toner colors, but the other configurations are the same as those of the process cartridge 30C. For this reason, in the following description, the process cartridge 30C will be described as a representative, and description of the other process cartridges 30M, 30Y, and 30K will be omitted as appropriate.

  The photosensitive drum 31 is located above the transfer roller 25 and sandwiches the transport belt 23 between the transfer roller 25 and the up-down direction. The charger 41 is, for example, a scorotron charger in which a charging wire 42 and a grid 43 are accommodated in a shield case 45. The charging wire 42 is made of metal, for example, gold-plated tungsten or tungsten alone. The shield case 45 is formed in a substantially rectangular tube shape that is long in the left-right direction, and an opening is formed in a portion facing the photosensitive drum 31. The grid 43 is configured by stretching a conductive wire in a mesh shape at the opening of the shield case 45. In addition, the charging wire 42 is stretched in the left-right direction in the shield case 45, and is disposed at an upper position on the rear side with respect to the photosensitive drum 31 with an interval. Therefore, the grid 43 is disposed between the photosensitive drum 31 and the charging wire 42.

  The charger 41 uniformly and positively charges the surface of the photosensitive drum 31 during image formation. Specifically, when a voltage is applied to the charging wire 42 and the grid 43, an electric field is formed between the charging wire 42 and the photosensitive drum 31, and corona discharge is generated. When an electric field is formed between the charging wire 42 and the grid 43, a voltage different from that of the charging wire 42 is applied to the grid 43, thereby controlling the strength of the electric field and the amount of charge.

  The exposure unit 35 is provided in the uppermost part inside the main body housing 2 and forms an electrostatic latent image based on image data on the surface of each charged photosensitive drum 31. The toner cartridge 33 supplies the toner to the surface of the photosensitive drum 31 by carrying the contained toner on the surface of the developing roller 47. The photoreceptor drum 31 forms a toner image by supplying toner to the electrostatic latent image formed on the surface. The transport unit 21 transfers the toner image developed on the surface of the photosensitive drum 31 onto the paper P while transporting the paper P toward the fixing unit 50.

  The fixing unit 50 is provided on the downstream side of the transport path R compared to the transport unit 21. The fixing unit 50 includes a heating roller 51 and a pressure roller 52. The heating roller 51 is disposed on the image forming surface side of the paper P, rotates in synchronization with the transport belt 23 and the like, and transports the paper P while heating the toner transferred onto the paper P. The pressure roller 52 sandwiches the paper P between itself and the heating roller 51 and rotates following the paper P while pressing the paper P toward the heating roller 51. Accordingly, the fixing unit 50 conveys the sheet P along the conveyance path R while heating and melting the toner transferred to the sheet P to fix the toner P on the sheet P.

  Next, an electrical configuration related to the present application of the printer 1 will be described with reference to FIG. FIG. 2 shows a schematic block diagram of a high-voltage power supply device 60 mounted on a circuit board (not shown) built in the printer 1 and a connection configuration related to the high-voltage power supply device 60. In the following description, when each component is distinguished for each color, the symbols of each part are suffixed with Y (yellow), M (magenta), C (cyan), K (black), or “1”. -4 "(for example, grid voltages GRID1 to GRID4) are added, and if not distinguished, the subscripts are omitted (for example, indicated as grid voltage GRID).

  The high-voltage power supply device 60 includes an ASIC (application specific IC) 61, a high-voltage power supply circuit 62 connected to the ASIC 61, a ROM 63, and a RAM 64. The ASIC 61 (an example of a control unit) controls the entire printer 1 in addition to the control of the high-voltage power supply circuit 62. The ROM 63 is a storage medium that stores various operation programs executed by the ASIC 61. The RAM 64 stores temporary data in various processes, image data used for printing processes, and the like.

  The high-voltage power supply circuit 62 includes a charging voltage generation circuit 70 (an example of a charging voltage application unit), a grid constant voltage circuit 81 (an example of a grid voltage adjustment unit), and a line current detection circuit 82 (an example of a current detection circuit). ing. Here, the charging voltage generation circuit 70 applies the charging voltage CHG to the power supply line PL to which the chargers 41 (41K to 41C) are connected in parallel. The grid constant voltage circuits 81K to 81C and the line current detection circuits 82K to 82C are provided corresponding to the chargers 41K to 41C.

  The charging voltage generation circuit 70 includes, for example, a PWM signal control circuit 71, a transformer drive circuit 72, a booster circuit 73, and an output voltage detection circuit 78. The charging voltage generation circuit 70 generates a charging voltage CHG to be applied to the charging wires 42K to 42C of the chargers 41K to 41C. Further, grid voltages GRID1 to GRID4 are generated by the charging voltage CHG and the grid constant voltage circuits 81K to 81C. The charging voltage CHG is, for example, about 5.5 kV to 7 kV. The grid voltage GRID is about 700V, for example.

  The PWM signal control circuit 71 includes, for example, a resistor and a capacitor (not shown), smoothes a PWM (Pulse Width Modulation) signal Sp1 from the port PWM1 of the ASIC 61, and converts the smoothed PWM signal Sp1 into a transformer drive circuit. 72. The transformer drive circuit 72 supplies an oscillation current to the booster circuit 73 based on, for example, the smoothed PWM signal Sp1 received from the PWM signal control circuit 71.

  The transformer 74 of the booster circuit 73 includes a primary winding 74a, a secondary winding 74b, and an auxiliary winding 74c. The transformer drive circuit 72 supplies an oscillation current to the primary winding 74 a of the transformer 74. In the transformer 74, the voltage value of the output voltage (charging voltage CHG) output from the secondary winding 74b is changed according to the duty ratio of the transmission current. For example, the transformer 74 generates the charging voltage CHG having a larger voltage value as the duty ratio of the PWM signal Sp1 increases. A rectifier diode 75, a smoothing capacitor 76, and an output resistor 77 are connected to the secondary winding 74b. As a result, the booster circuit 73 boosts and rectifies the voltage generated in the primary winding 74a of the transformer 74, and applies it as the charging voltage CHG to the charging wires 42K to 42C of the chargers 41K to 41C.

  The output voltage detection circuit 78 is connected between the auxiliary winding 74 c of the transformer 74 and the ASIC 61. The output voltage detection circuit 78 has, for example, a smoothing circuit and a voltage dividing resistor (not shown). The output voltage detection circuit 78 detects the output voltage v1 generated in the auxiliary winding 74c as the charging voltage CHG is generated. The output voltage detection circuit 78 smoothes and divides the output voltage v1 and supplies it to the port A / D1 of the ASIC 61 as the output voltage detection signal Sv1.

  Each of the grid constant voltage circuits 81 includes a voltage detection circuit 83 (an example of a current detection circuit) and an operational amplifier OP1. Since the circuit configurations of the grid constant voltage circuits 81K to 81C are the same, in the following description, the grid constant voltage circuit 81K corresponding to K (black) color will be described, and the other grid constant voltage circuits 81Y to 81Y will be described. A description of 81C will be omitted as appropriate. The voltage detection circuit 83K outputs a detection voltage Vgr1 corresponding to the grid voltage GRID1 of the grid 43K from the connection point between the two voltage-dividing resistors R7 and R8 connected in series. The detection voltage Vgr1 is input to the non-inverting input terminal of the operational amplifier OP1. The voltage detection circuit 83K supplies the detection voltage Vgr1 to the port A / D2 of the ASIC 61 as the divided voltage detection signal Sid1. The capacitor C3 forms an RC filter by being connected in parallel with the voltage dividing resistor R8. The ASIC 61 calculates the shunt current Id1 from the resistance value of the voltage dividing resistor R8 and the voltage value of the voltage dividing detection signal Sid1. In addition, the ASIC 61 calculates the grid voltage GRID1 from the voltage division ratio based on the voltage value of the divided voltage detection signal Sid1 and the resistance values of the voltage dividing resistors R7 and R8.

  The inverting input terminal of the operational amplifier OP1 is connected to the port PWM2 of the ASIC 61 via the output resistor R9. The output resistor R9 is grounded to GND via the capacitor C4. The ASIC 61 supplies the PWM signal Spp1 from the port PWM2 to the output resistor R9, and supplies the reference voltage Vth to the inverting input terminal of the operational amplifier OP1 through the output resistor R9. Accordingly, the ASIC 61 is configured to be able to change the voltage value of the reference voltage Vth of the operational amplifier OP1. The output terminal of the operational amplifier OP1 is connected to the inverting input terminal via a resistor R6 and a capacitor C2.

  Voltage dividing resistors R4 and R5 are connected to the output terminal of the operational amplifier OP1. The transistor Q1 is connected to the connection point of the voltage dividing resistors R4 and R5. In addition, in the voltage control line Ln1 connected to the connection point between the voltage dividing resistor R7 and the grid 43K, three resistors R1, R2, R3 for making the grid voltage GRID1 constant are arranged in this order from the positive side. They are connected in series. The transistor Q1 has a collector connected to a connection point between the resistors R1 and R2, and an emitter connected to a connection point between the resistors R2 and R3. In the transistor Q1, the base current is controlled by the output of the operational amplifier OP1, so that the collector-emitter voltage is changed. Further, the operational amplifier OP1 performs feedback control via the voltage control line Ln1 so that the detection voltage Vgr1 detected by the voltage detection circuit 83K becomes the reference voltage Vth.

  Thereby, the operational amplifier OP1 varies the base voltage so that the detection voltage Vgr1 becomes the reference voltage Vth, and varies the grid voltage GRID. In the grid constant voltage circuit 81K, the detection voltage Vgr1 becomes the reference voltage Vth by feedback control of the operational amplifier OP1, and the grid voltage GRID1 is converted to a predetermined voltage value. Therefore, the ASIC 61 can change the voltage value of the grid voltage GRID1, for example, by changing the duty ratio of the PWM signal Spp1. The transistor Q1 is not limited to a bipolar transistor, and may be an FET (Field Effect Transistor), for example.

  The voltage control line Ln1 is connected to a resistor R3 for detecting a line current Ir1 flowing between the transistor Q1 and GND as a line current detection circuit 82K. The line current detection circuit 82K supplies the positive terminal voltage of the resistor R3 to the port A / D3 of the ASIC 61 as the line voltage detection signal Sir1. The ASIC 61 calculates the line current Ir1 from the resistance value of the resistor R3 and the voltage value of the line voltage detection signal Sir1. Further, the ASIC 61 calculates the grid current Ig1 flowing through the grid 43K by adding the line current Ir1 and the shunt current Id1. A capacitor C1 charged with the grid voltage GRID is provided between the voltage control line Ln1 and the grid 43K.

  Next, the control operation in the printer 1 having the charging voltage generation circuit 70 and the four grid constant voltage circuits 81K to 81C configured as described above will be described with reference to FIGS. Here, the control operation related to the constant voltage setting of the grid voltage GRID of the charger 41 according to the present embodiment will be described.

  First, the ASIC 61 performs the control operation shown in FIGS. 3 and 4 at a predetermined timing. As the predetermined timing here, for example, the image forming unit 20 forms an image at the time of a glass turning operation (warming operation), immediately after turning on the power, after a predetermined number of printing operations are completed, or after a part replacement operation. The timing that is not applied is applicable. In the following description, as an example, a description will be given of a case where the process is executed during the rotation operation. As used herein, the term “rotating” refers to an agitating member (in the toner accommodating portion of each toner cartridge 33) for agitating the toner in each of the process cartridges 30C to 30K when the printer 1 receives a print job and starts the printing process. An operation that rotates an agitator or the like. For example, the printer 1 performs a constant voltage process during the rotation operation, and starts the printing process after completion.

  More specifically, first, the ASIC 61 sets initial values of the grid voltages GRID <b> 1 to GRID <b> 4 in step S (hereinafter, may be simply abbreviated as “S”) 11 shown in FIG. 3. For example, the ASIC 61 reads out the initial value stored in the ROM 63 (see FIG. 2) and stores it in the RAM 64 or the like. The magnitude of the initial value is 700V, for example.

  Next, the ASIC 61 controls the charging voltage generation circuit 70 based on the initial value of the grid voltage GRID, and applies the charging voltage CHG to each charger 41 (S13). Each grid constant voltage circuit 81 performs a process of making the grid voltages GRID1 to GRID4 constant by performing feedback control so that the detected voltage Vgr becomes the reference voltage Vth. Next, the ASIC 61 waits after stopping the wait process, for example, the next process for 1 ms, in order to secure the processing time necessary for making the voltage constant (S15).

  Next, the ASIC 61 executes a process (an example of a current detection process) for calculating the grid currents Ig1 to Ig4 based on the shunt currents Id1 to Id4 and the line currents Ir1 to Ir4 flowing in the grid constant voltage circuits 81K to 81C ( S16). The magnitudes of the grid currents Ig1 to Ig4 are, for example, 225 μA when the grid voltages GRID1 to GRID4 have an initial value of 700V. The ASIC 61 compares each of the grid currents Ig1 to Ig4 calculated in S16 with a lower limit value (S17). This lower limit value is further reduced below the lower limit value of the range in which the grid currents Ig1 to Ig4 are allowed, for example, the lower limit value of the range in which the desired image quality can be maintained, by reduction processing of the grid voltages GRID1 to GRID4 described later. It is a value for preventing it from being done.

  Next, when the ASIC 61 determines that all of the grid currents Ig1 to Ig4 are equal to or higher than the lower limit (S17: YES), the ASIC 61 sets any one of the four chargers 41K to 41C. A reference target is set (S19). The ASIC 61 controls the charging voltage generation circuit 70 so that the grid currents Ig1 to Ig4 of the charger 41 to be referred to have a predetermined current value (S21 to S27). In the ASIC 61 of the present embodiment, for example, the charger 41 that minimizes the grid current Ig is set as a reference target. In each of the chargers 41, for example, foreign matters such as silica contained in the toner may adhere to the charging wire 42. In general, the grid current Ig decreases as the amount of foreign matters increases. To do. Therefore, it is assumed that the charger 41 having the smallest grid current Ig is the charger 41 in which the charging wire 42 is most dirty. Note that the method of selecting the charger 41 to be referred to is not limited to the method based on the minimum value of the grid current Ig, and other methods may be used as appropriate according to the configuration of the printer 1 and the like. In the following description, as an example, a case where the charger 41K corresponding to the black (K) toner is selected as the reference charger 41 will be described.

  The ASIC 61 controls the charging voltage generation circuit 70 based on the grid current Ig1 of the reference charger 41K, and controls the grid current Ig1 to have a current value within a predetermined range. First, the ASIC 61 compares the grid current Ig1 with the set range lower limit value A11 (S21). The ASIC 61 increases the charging voltage CHG in response to determining that the grid current Ig1 is equal to or less than the set range lower limit value A11 (S21: NO) (S23). The ASIC 61 executes the process from S15 again. The charging voltage generation circuit 70 applies the increased charging voltage CHG to all the chargers 41.

  Further, when the ASIC 61 determines that the grid current Ig1 is larger than the set range lower limit value A11 (S21: YES), the ASIC 61 compares the grid current Ig1 and the set range upper limit value A12 (S25). In response to determining that the grid current Ig1 is equal to or greater than the set range upper limit value A12 (S25: NO), the ASIC 61 reduces the charging voltage CHG (S27), and executes the processing from S15 again. For example, the setting range lower limit value A11 and the setting range upper limit value A12 are set to a value of ± several percent with respect to 225 μA, which is the initial value of the grid current Ig1. As described above, the ASIC 61 of this embodiment controls the charging voltage generation circuit 70 so that the current value of the grid current Ig1 of the charger 41K to be referred to falls within a predetermined range.

  Next, the ASIC 61 sets the grid voltages GRID2 to GRID4 so that the current values of the grid currents Ig2 to Ig4 are smaller than a predetermined value with respect to the other chargers 41Y, 41M, and 41C except the charger 41K to be referred to. A process of reducing each is executed (S29 to S39). Furthermore, the ASIC 61 executes the control (S21 to S27) of the charging voltage generation circuit 70 again in response to the processing for reducing the grid voltages GRID2 to GRID4 of the other chargers 41Y, 41M, and 41C. To do. Therefore, the printer 1 of this embodiment always executes the process of changing the charging voltage CHG after executing the process of changing the grid voltages GRID2 to GRID4.

  More specifically, when the ASIC 61 determines that the grid current Ig1 is less than the set range upper limit value A12 (not including the set range upper limit value A12) (S25: YES), it corresponds to yellow (Y) toner. It is determined whether or not the grid current Ig2 of the charger 41Y to be operated is less than the predetermined value A2 (S29). In addition, the value which makes the grid voltage GRID1-GRID4 of each charger 41K-41C constant voltage may be the same value, or may be different from each other. Therefore, the predetermined value A2 may be the same value as the setting range upper limit value A12 or may be a different value.

  In response to determining that the grid current Ig2 is larger than the predetermined value A2 (S29: NO), the ASIC 61 executes a process of reducing the grid voltage GRID2 (S31). Specifically, the ASIC 61 is supplied to the inverting input terminal of the operational amplifier OP1 of the grid constant voltage circuit 81Y by changing the duty ratio of the PWM signal Spp2 supplied from the port PWM3 (see FIG. 2) to the output resistor R9. The reference voltage Vth is changed. Further, the ASIC 61 executes the processing from S15 again.

  Similarly, when the ASIC 61 determines that the grid current Ig2 is less than the predetermined value A2 (S29: YES), the grid current Ig3 of the charger 41M corresponding to the toner of Magenta (M) is less than the predetermined value A3. It is determined whether or not (S33). In response to determining that the grid current Ig3 is equal to or greater than the predetermined value A3 (S33: NO), the ASIC 61 executes a process of reducing the grid voltage GRID3 (S35), and executes the process from S15 again.

  Similarly, when the ASIC 61 determines that the grid current Ig3 is less than the predetermined value A3 (S33: YES), the grid current Ig4 of the charger 41C corresponding to the cyan (C) toner is less than the predetermined value A4. It is determined whether or not (S37). When the ASIC 61 determines that the grid current Ig4 is greater than or equal to the predetermined value A4 (S37: NO), the ASIC 61 executes a process of reducing the grid voltage GRID4 (S39), and executes the process from S15 again.

  Then, when the ASIC 61 determines that the grid current Ig4 is less than the predetermined value A4 (S37: YES), the ASIC 61 determines whether or not the printer 1 is in a printable state, for example, a state where the glass turning is finished. (S41). In response to determining that the ASIC 61 is in a printable state (S41: YES), the ASIC 61 starts a printing process (S43).

  Further, in response to determining that the ASIC 61 is not in a printable state (S41: NO), the processing from S15 is executed again. If the ASIC 61 determines that it is not in a printable state, it does not execute the processing from S15 again, and periodically repeats the determination processing in S41 until other processing such as turning the paper ends normally. May be.

  Further, the ASIC 61 changes the grid currents Ig1 to Ig4 and the grid voltages GRID1 to GRID4 directly or indirectly in the above-described processing. For this reason, the ASIC 61 has a case where the grid current Ig and the grid voltage GRID of any one of the plurality of chargers 41K to 41C are smaller than the lower limit value allowed during the constant voltage processing. In this case, an error is notified to the user of the printer 1 or the like. More specifically, when the ASIC 61 determines that any one of the grid currents Ig is equal to or lower than the lower limit value allowed (S17: NO), the lower limit value of the allowable range for each grid voltage GRID. Is executed (S47).

  In response to determining that each grid voltage GRID is larger than the allowable lower limit value (S47: YES), the ASIC 61 starts the processing from S19. On the other hand, when the ASIC 61 determines that each grid voltage GRID is equal to or lower than the lower limit (S47: NO), the ASIC 61 executes an error process (S49). In the error process, for example, a process of displaying an error message on a display unit (not shown) of the printer 1 or a process of lighting a warning sound or a lamp is executed.

  In addition, the ASIC 61 of this embodiment determines the determination result only when the grid voltage GRID corresponding to the grid current Ig determined to be equal to or lower than the lower limit value in S17 among the grid currents Ig1 to Ig4 in S47 is equal to or lower than the lower limit value. Becomes “NO”, and error processing (S49) is executed. That is, the ASIC 61 performs error processing only when the values of both the grid current Ig and the grid voltage GRID of any one of the chargers 41K to 41C are equal to or lower than an allowable lower limit (S49). )I do. Note that the determination criterion for the error is not limited to the above-described conditions, but other conditions, for example, the grid current Ig and the grid voltage GRID (a combination of the grid current Ig2 and the grid voltage GRID3, etc.) of different chargers 41 are not more than a predetermined value. The error condition may be used as the error condition.

The above-described embodiment has the following effects.
The ASIC 61 calculates the grid current Ig1 flowing in the reference target grid 43K by adding the line current Ir1 and the shunt current Id1 (S16). The ASIC 61 controls the charging voltage generation circuit 70 so that the calculated grid current Ig1 becomes a predetermined current value (S21 to S27). Further, the ASIC 61 executes a process for reducing each of the grid voltages GRID2 to GRID4 so that the current values of the grid currents Ig2 to Ig4 become smaller than a predetermined value for the chargers 41Y, 41M, and 41C (S29 to S29). S39). The printer 1 according to the present embodiment always executes the process of changing the charging voltage CHG after executing the process of changing the grid voltages GRID2 to GRID4 (S27, S31, S35, S39). For this reason, the ASIC 61 changes the charging voltage CHG based on the grid current Ig1 to be referred to that has been changed by changing the grid voltages GRID2 to GRID4. As a result, in the printer 1 of the present embodiment, the charging voltage CHG and the grid are changed by stabilizing the processing by achieving both the processing for changing the charging voltage CHG and the processing for changing the grid voltages GRID2 to GRID4. The voltage GRID can be made constant.

  In the ASIC 61, grid currents Ig2 to Ig4 flowing in at least one grid (any one of the grids 43Y, 43M, and 43C) among the other chargers 41Y, 41M, and 41C excluding the charger 41K to be referred to are predetermined. When the value is equal to or greater than a value (predetermined value A2 or the like), processing for changing the grid voltages GRID2 to GRID4 is executed. On the other hand, the ASIC 61 executes a process of changing the charging voltage CHG after changing the grid voltages GRID2 to GRID4. In such a configuration, the printer 1 changes the grid voltages GRID2 to GRID4 of the grids 43Y, 43M, and 43C other than the reference target, even if the grid current Ig1 of the grid 43K that is the reference target is changed. Then, by following the processing procedure for changing the charging voltage CHG, the grid voltages GRID1 to GRID4 can be made constant.

  In addition, the ASIC 61 sets, for example, the charger 41 that minimizes the grid current Ig as a reference target. In such a configuration, for example, the photosensitive drum 31 can be sufficiently charged by the most dirty charging wire 42.

  Further, the ASIC 61 repeatedly executes the processing (S21 to S27) of changing the charging voltage CHG according to a predetermined condition while sequentially switching the grid 43 to be changed of the grid voltage GRID (S29, S33, S37). Thus, the process of making the grid voltage GRID constant can be more stably executed.

  Further, the ASIC 61 reduces the grid voltages GRID2 to GRID4 (S31 and the like) as the grid currents Ig2 to Ig4 increase and become equal to or greater than a predetermined value (a predetermined value A2 and the like). As a result, the ASIC 61 can suppress variations in the surface potential of the photoconductive drum 31 and suppress deterioration in image quality.

  Further, the ASIC 61 performs error processing when the values of both the grid current Ig and the grid voltage GRID of any one of the chargers 41K to 41C are equal to or lower than an allowable lower limit value (S49). ), It is possible to perform processing such as prompting the user to perform wire cleaning.

  In addition, the ASIC 61 performs the control operation illustrated in FIGS. 3 and 4 at a timing when the image forming unit 20 does not form an image, such as a rotation operation. In such a configuration, it is possible to suppress the influence of the change of the grid voltage GRID and the change of the charging voltage CHG on the image quality.

  Incidentally, the printer 1 is an example of an image forming apparatus. The photoconductor drum 31 is an example of a photoconductor. The ASIC 61 is an example of a control unit. The charging voltage generation circuit 70 is an example of a charging voltage application unit. The grid constant voltage circuit 81 is an example of a grid voltage adjustment unit. The line current detection circuit 82 and the voltage detection circuit 83 are examples of a current detection circuit. The process of S21 to S27 shown in FIG. 4 is an example of a charging voltage changing process. The process of S16 illustrated in FIG. 3 is an example of a current detection process. The process of S29 to S39 shown in FIG. 4 is an example of a grid voltage change process.

Needless to say, the present invention is not limited to the above-described embodiment, and various improvements and modifications can be made without departing from the spirit of the present invention.
For example, in the above-described embodiment, the power supply line PL to which the charging voltage generation circuit 70 and each charger 41 (41K to 41C) are connected is not limited to the configuration described above. For example, the charging voltage generation circuit 70 and each charging As long as the power supply line is connected to the container 41, the connection form, material, composition, and the like can be changed as appropriate.
Further, based on the grid current Ig of any charger 41, a process for reducing the grid voltage GRID of another charger 41 may be executed. For example, a process of reducing the grid voltage GRID2 of the other charger 41Y may be executed based on the grid current Ig1 of the reference grid 43K.
Moreover, in the said embodiment, although the reduction process of the grid voltage GRID based on the grid current Ig was performed with respect to all the chargers 41K-41C other than a reference object, any one among the chargers 41K-41C. It may be configured to be executed in the following manner.

  In the above-described embodiment, the ASIC 61 has a grid current that flows in at least one grid (any one of the grids 43Y, 43M, and 43C) among the other chargers 41Y, 41M, and 41C other than the charger 41K to be referred to. When Ig2 to Ig4 are equal to or higher than a predetermined value (predetermined value A2 or the like), the process of changing the grid voltages GRID2 to GRID4 is executed and the process from S15 is executed again, but the present invention is not limited to this. For example, the ASIC 61 starts from S15 only when the grid voltages GRID2 to GRID4 are changed for each of the grids 43Y, 43M, and 43C of all the chargers 41Y, 41M, and 41C other than the charger 41K to be referred to. It may be set to execute the process again. More specifically, when the ASIC 61 executes the steps shown in FIG. 4 as (S29: NO) → S31 → (S33: NO) → S35 → (S37: NO) → S39, the processing from S15 is performed. It is good also as a setting performed again. Further, the ASIC 61 is set to execute the processing of S41 and subsequent steps when it becomes less than a predetermined value (YES) in each determination of S29, S33, and S37. Even in such a configuration, the grid voltage GRID1 is changed by changing the charging voltage CHG with respect to the change of the grid current Ig1 of the reference object accompanying the change of the grid voltages GRID2 to GRID4 other than the reference object while reducing the processing addition. It becomes possible to make GRID4 constant.

  Further, in the above-described embodiment, an example in which one charger 41 is associated with one photosensitive drum 44 has been described, but the present invention is not limited to this. In the present application, a configuration in which a plurality of chargers 41 are associated with one photosensitive drum 44, for example, a printer (image forming unit) that superimposes toner images of each color on one photosensitive drum 44 and then collectively transfers the image onto paper P. (Apparatus).

  In the above-described embodiment, the ASIC 61 may execute a process of switching the charger 41 (grid 43) to be referred to. In this case, the ASIC 61 changes the grid voltage GRID to a constant voltage by switching the grid 43 to be referred to according to appropriate conditions and timing (for example, when the charging voltage CHG exceeds a desired value). Can be executed more stably.

  In addition, the ASIC 61 performs all of the control operations shown in FIGS. 3 and 4 at a timing when the image forming unit 20 does not form an image, such as a rotating operation, but a part of the control operation, for example, the grid voltage GRID2 The process of changing the charging voltage CHG after the process of changing GRID4 (S27, S31, S35, S39) may be performed during printing.

Moreover, in the said embodiment, although ASIC61 was used as a control part, the control part in this application is not limited to when comprised with exclusive hardwares, such as ASIC61, For example, it comprises with the software which operate | moves on CPU. Also good.
In the above embodiment, the printer 1 is described as an example of the image forming apparatus of the present application. However, the present invention is not limited to this, and the scanner function, the copy function, and the facsimile function are implemented alone or in an appropriate combination. It can also be applied to multifunction devices.

DESCRIPTION OF SYMBOLS 1 Laser printer, 20 Image formation part, 31 Photosensitive drum, 42 Charging wire, 43 grid, 61 ASIC, 70 Charging voltage generation circuit, 81 Grid constant voltage circuit, GRID grid voltage, Ig grid current.

Claims (11)

A plurality of photoreceptors;
A plurality of charged wires;
A charging voltage application unit connected to each of the plurality of charging wires and applying a charging voltage to the plurality of charging wires;
A grid provided between the photoreceptor and the charging wire;
An image forming unit that forms an image on the plurality of photoconductors;
A grid voltage adjustment unit for adjusting a grid voltage of the grid;
A current detection circuit for detecting a grid current flowing in the grid;
A control unit,
The controller is
A current detection process that uses at least one grid among the plurality of grids as a reference target and detects a grid current flowing in the reference target grid using the current detection circuit;
A charging voltage changing process for changing the charging voltage based on a detection result of the current detecting process;
When executing the grid voltage changing process for changing the grid voltage,
An image forming apparatus, wherein the charging voltage changing process is executed based on a detection result of the current detecting process changed by executing the grid voltage changing process. The controller is
Performing the current detection process on a plurality of the current detection circuits;
The current detection process detects a grid current flowing in at least one grid among other grids excluding the reference target grid,
The image forming apparatus according to claim 1, wherein the grid voltage changing process changes a grid voltage generated in the other grid based on a detection result of a grid current flowing in the other grid.   The image forming apparatus according to claim 2, wherein the grid voltage changing process changes the grid voltage for all of the other grids. The controller is
4. The image forming apparatus according to claim 1, wherein a reference target switching process is performed to switch the reference target grid to another grid excluding the reference target grid. 5. The controller is
5. The image forming apparatus according to claim 1, wherein a reference target setting process is performed to set a grid having a minimum grid current as the reference target among the plurality of grids. . The controller is
The charging voltage changing process and the grid voltage changing process are alternately and repeatedly executed, and the grid voltage changing process is repeatedly executed while switching a grid to be changed in the grid voltage. The image forming apparatus according to claim 1.   7. The image formation according to claim 1, wherein the grid voltage changing process reduces the grid voltage generated in the grid as the grid current flowing in the grid increases. apparatus. The controller is
8. The image formation according to claim 1, wherein a notification process for notifying an error is executed in response to the magnitude of the grid voltage becoming smaller than a predetermined value. apparatus. The controller is
9. The process according to claim 1, wherein at least one of the grid voltage changing process and the charging voltage changing process is executed according to a timing at which the image forming unit does not form an image. The image forming apparatus according to any one of the above. A plurality of photosensitive members, a plurality of charging wires, a charging voltage applying unit that is connected to each of the plurality of charging wires and applies a charging voltage to the plurality of charging wires, and between the photosensitive member and the charging wires A grid provided on the image forming unit, an image forming unit that forms an image on the plurality of photosensitive members, a grid voltage adjusting unit that adjusts a grid voltage of the grid, a current detection circuit that detects a grid current flowing in the grid, A control unit, and a control method of an image forming apparatus comprising:
A current detection process that uses at least one grid among the plurality of grids as a reference target and detects a grid current flowing in the reference target grid using the current detection circuit;
A charging voltage changing process for changing the charging voltage based on a detection result of the current detecting process;
When executing the grid voltage changing process for changing the grid voltage,
A control method for an image forming apparatus, wherein the charging voltage changing process is executed based on a detection result of the current detecting process that has been changed by executing the grid voltage changing process. A plurality of photosensitive members, a plurality of charging wires, a charging voltage applying unit that is connected to each of the plurality of charging wires and applies a charging voltage to the plurality of charging wires, and between the photosensitive member and the charging wires A grid provided on the image forming unit, an image forming unit that forms an image on the plurality of photosensitive members, a grid voltage adjusting unit that adjusts a grid voltage of the grid, a current detection circuit that detects a grid current flowing in the grid, A program for controlling an image forming apparatus comprising:
In the image forming apparatus,
A current detection process that uses at least one grid among the plurality of grids as a reference target and detects a grid current flowing in the reference target grid using the current detection circuit;
A charging voltage changing process for changing the charging voltage based on a detection result of the current detecting process;
When executing the grid voltage changing process for changing the grid voltage,
A program for causing the charging voltage changing process to be executed based on a detection result of the current detecting process that has been changed by executing the grid voltage changing process.

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