Image formation control method, and image forming apparatus

Abstract

To prevent developing voltage from adversely affecting the surface potential of an image carrier.SOLUTION: A charging device 42 applies charging voltage to a charging member 421 to electrostatically charge a surface of an image carrier 41. A developing device 43 applies developing voltage to a developing member 431 and supplies developer to the surface of the image carrier 41 from the developing member 431. A current measuring device 42c measures a current flowing in the charging member 421. A control unit 8 selects a target derivation rule from a plurality of candidate derivation rules according to the amplitude of the developing voltage. The control unit 8 applies a measurement from the current measuring device 42c to the target derivation rule to derive a charging control value representing the level of the charging voltage. The control unit 8 causes the charging device 42 to output the charging voltage corresponding to the charging control value.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an image formation control method and an image forming apparatus capable of controlling a charging voltage for charging an image carrier. [Background technology]

[0002] An electrophotographic image forming apparatus includes a drum-shaped photoconductor, a charging device, an exposure device, and a developing device. The charging device charges the surface of the photoconductor.

[0003] The exposure device forms an electrostatic latent image on the charged surface of the photoconductor. The development device develops the electrostatic latent image by supplying a developer to the surface of the photoconductor. The photoconductor is an example of an image carrier.

[0004] The charging device includes a charging roller that is in contact with the surface of the photoconductor, and applies a charging voltage to the charging roller to charge the surface of the photoconductor.

[0005] The developing device includes a developing roller that carries a developer, and supplies the developer to the surface of the photoconductor from the developing roller. The developing device outputs a developing voltage to the developing roller.

[0006] The surface potential of the photoconductor has a positive correlation with the current flowing through the charging roller. It is known that the output level of the charging voltage is controlled in response to a measured value of the current flowing through the charging roller (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2002-207351 A Summary of the Invention [Problem to be solved by the invention]

[0008] Incidentally, the developing voltage is adjusted in order to adjust the density of an output image, improve the image quality of an output image, etc. The developing voltage may include a DC component and an AC component.

[0009] When the distance from the charging roller to the developing roller is short or when the amplitude of the developing voltage is large, the AC component of the developing voltage may interfere with the charging voltage, which may cause a disturbance in the waveform of the actual voltage of the charging roller, and may ultimately cause a change in the average level of the actual voltage of the charging roller.

[0010] If the average level of the actual voltage of the charging roller changes, the surface potential of the photoconductor changes, which may result in deterioration of the image quality of the output image.

[0011] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide an image formation control method and an image forming apparatus capable of preventing the development voltage from adversely affecting the surface potential of an image carrier. [Means for solving the problem]

[0012] According to one aspect of the present invention, there is provided an image forming control method for controlling an image forming apparatus including an image carrier, a charging device, an exposure device, a developing device, and a current measuring device. The charging device has a charging member in contact with the surface of the image carrier, and charges the surface of the image carrier by applying a charging voltage including a DC component and an AC component to the charging member. The exposure device exposes the charged surface of the image carrier to light to form an electrostatic latent image on the surface of the image carrier. The developing device has a developing member disposed opposite the image carrier and carrying a developer, and develops the electrostatic latent image by applying a developing voltage including a DC component and an AC component to the developing member and supplying the developer from the developing member to the surface of the image carrier. The current measuring device measures the current flowing through the charging member. The image forming control method includes a control device selecting a target derivation rule from among a plurality of preset candidate derivation rules according to the amplitude of the development voltage. The image formation control method further includes the control device deriving a charge control value representing a level of the charge voltage by applying a measurement value of the current measurement device to the target derivation rule, and the image formation control method further includes the control device causing the charging device to output the charge voltage corresponding to the charge control value.

[0013] An image forming apparatus according to another aspect of the present invention includes the image carrier, the charging device, the exposure device, the developing device, the current measuring device, and the control device. Effect of the Invention

[0014] According to the present invention, it is possible to provide an image formation control method and an image forming apparatus that can prevent the development voltage from adversely affecting the surface potential of the image carrier. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram showing the configuration of an image forming apparatus according to an embodiment. [Diagram 2] FIG. 2 is a block diagram showing the configuration of a control device in the image forming apparatus according to the embodiment. [Diagram 3] FIG. 3 is a block diagram showing the configuration of a charging bias output circuit and a developing bias output circuit in the image forming apparatus according to the embodiment. [Figure 4] FIG. 4 is a flowchart showing an example of a procedure for setting the charging bias in the image forming apparatus according to the embodiment. [Diagram 5] FIG. 5 is a flowchart showing an example of a procedure for controlling the charging bias output in the image forming apparatus according to the embodiment. [Figure 6] FIG. 6 is a diagram showing the disturbance of the charging bias waveform caused by the change in the amplitude of the developing bias. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the following embodiment is an example of the present invention, and is not intended to limit the technical scope of the present invention.

[0017] [Configuration of image forming device] The image forming apparatus 10 is an apparatus that forms an image on a sheet 9 by an electrophotographic method. The image forming apparatus 10 is, for example, a printer, a copier, a facsimile, or a multifunction machine.

[0018] As shown in FIG. 1, an image forming apparatus 10 includes a sheet supply mechanism 2, a sheet transport mechanism 3, an image forming section 4, a control device 8, a user interface device 800, and the like.

[0019] A sheet supply mechanism 2 feeds sheets 9 one by one onto a transport path 30, and a sheet transport mechanism 3 transports the sheets 9 along the transport path 30. The sheets 9 are image formation media such as paper or a resin sheet.

[0020] The image forming unit 4 executes a print process to form a toner image on the sheet 9 transported along the transport path 30. The image forming unit 4 includes an optical scanning unit 40, a photoconductor 41, a charging device 42, a developing device 43, a transfer device 44, a cleaning device 45, a fixing device 46, and the like.

[0021] The photoconductor 41 is rotated by being driven by a driving mechanism (not shown). The charging device 42 charges the surface of the photoconductor 41.

[0022] The optical scanning unit 40 scans a beam of light over the charged surface of the photoconductor 41 to form an electrostatic latent image on the surface of the photoconductor 41. The developing device 43 supplies toner to the surface of the photoconductor 41 to develop the electrostatic latent image into a toner image.

[0023] The photoconductor 41 is an example of an image carrier that carries the toner image. The optical scanning unit 40 is an example of an exposure device that forms the electrostatic latent image on the surface of the photoconductor 41 by exposing the surface of the photoconductor 41 to light.

[0024] The transfer device 44 transfers the toner image on the photoconductor 41 onto the sheet 9 moving along the transport path 30. The cleaning device 45 removes waste toner remaining on the surface of the photoconductor 41.

[0025] The fixing device 46 fixes the toner image formed on the sheet 9 to the sheet 9 by applying heat and pressure.

[0026] The charging device 42 includes a charging roller 421 that rotates while being in contact with the surface of the photoconductor 41. The charging device 42 charges the surface of the photoconductor 41 by applying a charging bias VC1 to the charging roller 421. The charging bias VC1 includes a DC component and an AC component.

[0027] The developing device 43 is disposed opposite the photoconductor 41 and includes a developing roller 431 that carries and rotates toner. The developing device 43 supplies toner from the surface of the developing roller 431 to the surface of the photoconductor 41 by applying a developing bias VD1 to the developing roller 431. The toner is an example of a developer. In this embodiment, the developing device 43 performs development by a two-component development method that uses the toner and a magnetic carrier mixed with the toner.

[0028] The charging bias VC1 is a charging voltage based on the potential of the photoconductor 41. The developing bias VD1 is a developing voltage based on the potential of the photoconductor 41. The charging roller 421 is an example of a charging member. The developing roller 431 is an example of a developing member that carries a developer.

[0029] The user interface device 800 includes an operation unit that accepts user operations and a display unit that displays information.

[0030] The control device 8 controls various electric devices included in the image forming apparatus 10. For example, the control device 8 controls the charging device 42, the developing device 43, the user interface device 800, and the like.

[0031] The control device 8 includes a central processing unit (CPU) 80, a random access memory (RAM) 81, a secondary storage device 82, a communication device 83, and a signal interface 84 (see FIG. 2).

[0032] The CPU 80 executes various control and data processing operations by executing computer programs. The RAM 81 temporarily stores the computer programs executed by the CPU 80 and various data.

[0033] The secondary storage device 82 is a computer-readable non-volatile storage device. The secondary storage device 82 stores the computer programs executed by the CPU 80 and various data. For example, one or both of a flash memory and a hard disk drive are adopted as the secondary storage device 82.

[0034] The communication device 83 executes communication with other devices such as a host device through a network. The CPU 80 executes communication with other devices through the communication device 83. The host device is an information processing device that requests the image forming apparatus 10 to perform a print process.

[0035] The signal interface 84 converts the detection signals of the various sensors into digital detection data. The detection data is transmitted to the CPU 80.

[0036] The CPU 80 includes a plurality of processing modules that are realized by executing the computer programs, including a main control unit 8a and a print control unit 8b (see FIG. 2).

[0037] The main control unit 8a executes a process of receiving various requests and a control for causing other modules to execute processes according to the requests.

[0038] For example, the main control unit 8a accepts a print request through the user interface device 800 or the communication device 83. Furthermore, the main control unit 8a causes the print control unit 8b to execute processing in response to the print request.

[0039] The print control unit 8b controls the sheet supply mechanism 2 and the sheet transport mechanism 3 to control the supply and transport of the sheet 9. Furthermore, the print control unit 8b causes the image forming unit 4 to execute the print process in synchronization with the transport of the sheet 9.

[0040] The surface potential of the photoconductor 41 has a positive correlation with the current flowing through the charging roller 421. As will be described later, the print control unit 8b controls the output level of the charging bias VC1 in response to a measurement value of the current flowing through the charging roller 421.

[0041] Incidentally, the developing bias VD1 is adjusted to adjust the density of an output image, or to improve the image quality of an output image, etc. In this embodiment, the developing bias VD1 includes a DC component and an AC component.

[0042] When the distance from charging roller 421 to developing roller 431 is short, or when the amplitude of developing bias VD1 is large, the AC component of developing bias VD1 may interfere with charging bias VC1. Interference of developing bias VD1 with charging bias VC1 may cause a disturbance in the AC waveform of the actual bias voltage of charging roller 421, which may result in a change in the average level of the actual voltage of charging roller 421.

[0043] 6 shows an example of the waveforms of the developing bias VD1 and the actual charging bias VC2. The actual charging bias VC2 is the actual bias voltage of the charging roller 421 when the charging bias VC1 is output to the charging roller 421.

[0044] In FIG. 6, a first period T1 is a period during which a developing bias VD1 that does not include an AC component is output, a second period T2 is a period during which a developing bias VD1 of a relatively small amplitude is output, and a third period T3 is a period during which a developing bias VD1 of a relatively large amplitude is output.

[0045] In FIG. 6, the waveform of the charging bias VC1 output to the charging roller 421 is indicated by a virtual line (two-dot chain line).

[0046] As shown in Fig. 6, the waveform of the actual charging bias VC2 may be disturbed due to interference with the developing bias VD1, which includes an AC component. The second period T2 and the third period T3 in Fig. 6 show that the waveform of the actual charging bias VC2 is more likely to be disturbed as the amplitude of the developing bias VD1 increases.

[0047] Disturbance in the waveform of the actual charging bias VC2 tends to cause a change in the average level of the actual charging bias VC2.

[0048] If the average level of the actual charging bias VC2 changes, the surface potential of the photoconductor 41 changes, which may result in a deterioration in the quality of the output image.

[0049] In the image forming apparatus 10, the print control unit 8b executes a charging bias setting process and a charging bias output control, which will be described later. These processes include a process for preventing the developing bias VD1 from adversely affecting the surface potential of the photoconductor 41.

[0050] The charging bias setting process and the charging bias output control are an example of a process for realizing an image formation control method. The image formation control method is a method for controlling the image forming apparatus 10.

[0051] Here, with reference to FIG. 3, the configurations of the charging device 42 and the developing device 43 required for the charging bias setting process and the charging bias output control will be described.

[0052] As shown in FIG. 3, the charging device 42 includes a charging bias output circuit 420 , and the developing device 43 includes a developing bias output circuit 430 .

[0053] The charging bias output circuit 420 applies a charging bias VC1 including a DC component and an AC component to the charging roller 421. The charging bias output circuit 420 includes a DC power supply circuit 42a and an AC power supply circuit 42b.

[0054] The DC power supply circuit 42a receives the first DC level signal SV11 and generates a DC charging voltage V11 that corresponds to the level of the first DC level signal SV11.

[0055] The AC power supply circuit 42b receives the first amplitude signal SV12 and generates an AC charging voltage V12 having an amplitude corresponding to the level of the first amplitude signal SV12 and a predetermined frequency.

[0056] Furthermore, the AC power supply circuit 42b outputs a voltage obtained by superimposing the AC charging voltage V12 on the DC charging voltage V11 as a charging bias VC1.

[0057] The charging bias output circuit 420 further includes a current measuring circuit 42c. The current measuring circuit 42c measures the DC current flowing from the charging bias output circuit 420 to the charging roller 421.

[0058] The current measurement circuit 42c outputs a current measurement signal SA1 indicating a measurement value of the current to the control device 8. The current measurement circuit 42c is an example of a current measurement device.

[0059] The developing bias output circuit 430 applies a developing bias VD1 including a DC component and an AC component to the developing roller 431. The developing bias output circuit 430 includes a DC power supply circuit 43a and an AC power supply circuit 43b.

[0060] The DC power supply circuit 43a receives the second DC level signal SV21 and generates a DC developing voltage V21 that corresponds to the level of the second DC level signal SV21.

[0061] The AC power supply circuit 43b receives the second amplitude signal SV22 and generates an AC developing voltage V22 having an amplitude corresponding to the level of the second amplitude signal SV22 and a predetermined frequency.

[0062] Furthermore, the AC power supply circuit 43b outputs a voltage obtained by superimposing the AC developing voltage V22 on the DC developing voltage V21 as a developing bias VD1.

[0063] In this embodiment, the print control unit 8b outputs the first DC level signal SV11 and the first amplitude signal SV12 to the charging bias output circuit 420 through the signal interface 84. Furthermore, the print control unit 8b outputs the second DC level signal SV21 and the second amplitude signal SV22 to the developing bias output circuit 430 through the signal interface 84.

[0064] [Charge bias setting process] Next, an example of the procedure of the charging bias setting process will be described with reference to the flowchart shown in FIG.

[0065] The print control unit 8b executes the charging bias setting process when the amplitude parameter of the developing bias parameter is changed.

[0066] The developing bias parameters include a DC voltage parameter and the amplitude parameter. The DC voltage parameter represents a level of a DC component of the developing bias VD1. The amplitude parameter represents an amplitude of the developing bias VD1.

[0067] The print control unit 8b may execute the charging bias setting process when an adjustment start operation on the user interface device 800 is detected.

[0068] When the printing process is performed, the print control section 8b outputs to the developing bias output circuit 430 the second DC level signal SV21 and the second amplitude signal SV22, whose levels correspond to the developing bias parameters.

[0069] In the following description, S101 and S102 represent identification codes of a plurality of steps in the charging bias setting process. In the charging bias setting process, the process of step S101 is executed first.

[0070] <Process S101> In step S101, the print control unit 8b acquires the amplitude parameter of the developing bias VD1. After executing the process of step S101, the print control unit 8b executes the process of step S102.

[0071] <Process S102> In step S102, the print control unit 8b selects a target formula from among a plurality of preset candidate formulas according to the amplitude parameter of the developing bias VD1, and records target selection data representing the selection result in the secondary storage device .

[0072] The plurality of candidate formulas are an example of a plurality of candidate derivation rules. The plurality of candidate derivation rules are rules for deriving a voltage level of a DC component and an amplitude of an AC component in the charging bias VC1 from a current measurement value of the current measurement circuit 42c.

[0073] Each of the plurality of candidate formulas is a formula for deriving the level and amplitude of the DC component of the charging bias VC1 using the current measurement value representing the level of the current measurement signal SA1 as a variable. Each of the plurality of candidate formulas is associated with a plurality of amplitude sections representing the range of the amplitude of the developing bias VD1.

[0074] Each of the plurality of candidate formulas is set based on data of a charging characteristic test that is performed in advance. The charging characteristic test is a test that measures the relationship between the charging bias VC1 for each of the plurality of amplitude sections of the developing bias VD1, the current measurement value, and the surface potential of the photoconductor 41.

[0075] Each of the plurality of candidate equations represents the relationship between the current measurement value and the charging bias VC1 when the surface potential of the photoconductor 41 becomes the target potential for each amplitude section.

[0076] The print control unit 8b selects, from the plurality of candidate formulas, one that corresponds to the amplitude represented by the amplitude parameter as the target formula.

[0077] Derivation rule data representing the plurality of amplitude sections and the plurality of candidate formulas is stored in advance in the secondary storage device 82. In step S102, the print control unit 8b acquires the derivation rule data from the secondary storage device 82, and selects the symmetric formula based on the derivation rule data and the amplitude parameters.

[0078] After executing the process of step S102, the print control unit 8b ends the charging bias setting process.

[0079] [Charge bias output control] Next, an example of a procedure for controlling the charging bias output will be described with reference to the flowchart shown in FIG.

[0080] The print control unit 8b executes the charging bias output control when the print process is executed. As described above, the print control unit 8b also executes the control of the developing bias output circuit 430 based on the developing bias parameter in parallel with the charging bias output control.

[0081] In the following description, S201 to S204 represent identification codes of a plurality of steps in the charging bias output control. In the charging bias output control, first, the process of step S201 is executed.

[0082] <Process S201> In step S201, the print control unit 8b acquires a current measurement value that is a measurement value of a current by the current measuring circuit 42c.

[0083] In the first step S201 executed before the charging bias VC1 is output, the print control unit 8b sets a predetermined reference value as the current measurement value.

[0084] In this embodiment, the current measurement value is a value that indicates the level of the current measurement signal SA1. After executing the process of step S201, the print control unit 8b executes the process of step S202.

[0085] <Process S202> In step S202, the print control unit 8b derives a charging bias control value by applying the current measurement value to the equation.

[0086] The charging bias control value includes a level and an amplitude value of a DC component of the charging bias VC1 The charging bias control value is an example of a charging control value that indicates the level of the charging bias VC1.

[0087] The print control unit 8b specifies the symmetric formula based on the target selection data recorded in the secondary storage device 82. After executing the process of step S202, the print control unit 8b executes the process of step S203.

[0088] <Process S203> In step S203, the print control unit 8b executes the charging bias control, which is a process of causing the charging bias output circuit 420 to output the charging bias VC1 corresponding to the charging bias control value.

[0089] In this embodiment, the print control unit 8b outputs a second DC level signal SV21 and a second amplitude signal SV22 corresponding to the charging bias control value to the charging bias output circuit 420. As a result, the charging bias output circuit 420 applies a charging bias VC1 of a level corresponding to the second DC level signal SV21 and the second amplitude signal SV22 to the charging roller 421.

[0090] After executing the process of step S203, the print control unit 8b executes the process of step S204.

[0091] <Process S204> In step S204, the print control unit 8b determines whether or not the print process is completed.

[0092] When the print control unit 8b determines that the print process has not been completed, the print control unit 8b repeats the process from step S101 again. On the other hand, when the print control unit 8b determines that the print process has been completed, the print control unit 8b ends the charging bias output control.

[0093] By executing the charging bias setting process and the charging bias output control, the symmetrical equation is selected in consideration of the interference of the developing bias VD1 with the charging bias VC1. As a result, even if the interference of the developing bias VD1 with the charging bias VC1 occurs, the level of the charging bias VC1 is set so that the average level of the actual voltage of the charging roller 421 is maintained at the target level.

[0094] By employing the image forming apparatus 10, deterioration of the image quality of the output image caused by interference of the developing bias VD1 with the charging bias VC1 is prevented. In other words, the developing bias VD1 is prevented from adversely affecting the surface potential of the photoconductor 41.

[0095] [First application example] A first application example of the image forming apparatus 10 will be described below.

[0096] In this application example, the derivation rule data includes the plurality of amplitude sections and a plurality of candidate conversion tables.

[0097] In step S102 of the charging bias setting process, the print control unit 8b in this application example selects one of the plurality of candidate conversion tables that corresponds to the amplitude represented by the amplitude parameter as a target conversion table.

[0098] Each of the plurality of candidate conversion tables is a conversion table such as a lookup table that uses the current measurement value as an input value and the level and amplitude of the DC component of the charging bias VC1 as an output value. The plurality of candidate conversion tables are an example of the plurality of derivation rules.

[0099] In the present application example, the print control unit 8b derives the charging bias control value by applying the current measurement value to the target conversion table in the charging bias output control step S202.

[0100] When this application example is adopted, the same effects as when the image forming apparatus 10 is adopted can be obtained.

[0101] [Second application example] Next, a second application example of the image forming apparatus 10 will be described.

[0102] In this application example, the plurality of candidate formulas are a plurality of DC voltage derivation formulas that derive the level of the DC component of the charging bias VC1 using the current measurement value as a variable. The print control unit 8b derives the level of the DC component of the charging bias VC1 based on one selected from the plurality of DC voltage derivation formulas.

[0103] On the other hand, the amplitude derivation formula for deriving the amplitude of the charging bias VC1 using the current measurement value as a variable is a common formula regardless of the amplitude of the developing bias VD1. That is, the print control unit 8b derives the amplitude of the charging bias VC1 based on the amplitude derivation formula regardless of the amplitude of the developing bias VD1.

[0104] In this application example, the plurality of conversion tables may be used instead of the plurality of candidate formulas. When this application example is used, the same effects as when the image forming apparatus 10 is used can be obtained. [Explanation of symbols]

[0105] 8: Control device 10: Image forming device 40: Optical scanning unit (exposure device) 41: Photoconductor (image carrier) 42: Charging device 42a: DC power supply circuit 42b: AC power supply circuit 42c: Current measurement circuit 43: Developing device 43a: DC power supply circuit 43b: AC power supply circuit 420: Charging bias output circuit 421: Charging roller (charging member) 430: Development bias output circuit 431: Developing roller (developing material) 800: User interface devices

Claims

1. An image carrier; a charging device having a charging member in contact with a surface of the image carrier, the charging device applying a charging voltage including a DC component and an AC component to the charging member to charge the surface of the image carrier; an exposure device for forming an electrostatic latent image on the surface of the image carrier by exposing the charged surface of the image carrier; a developing device which has a developing member disposed opposite to the image carrier and carrying a developer, and which develops the electrostatic latent image by applying a developing voltage including a DC component and an AC component to the developing member and supplying the developer from the developing member to a surface of the image carrier; a current measuring device that measures a current flowing through the charging member, A control device selects a target derivation rule from a plurality of preset candidate derivation rules according to the amplitude of the development voltage; the control device derives an electrostatic control value representing a level of the electrostatic voltage by applying the measurement value of the current measuring device to the target derivation rule; the control device causes the charging device to output the charging voltage corresponding to the charging control value.

2. 2. The image formation control method according to claim 1, wherein the control device derives a voltage level of a DC component and an amplitude of an AC component of the charging voltage as the charging control value.

3. 3. The image formation control method according to claim 1, wherein each of the plurality of candidate derivation rules is a mathematical expression or a conversion table.

4. An image carrier; a charging device having a charging member in contact with a surface of the image carrier, the charging device applying a charging voltage including a DC component and an AC component to the charging member to charge the surface of the image carrier; an exposure device for forming an electrostatic latent image on the surface of the image carrier by exposing the charged surface of the image carrier; a developing device which has a developing member disposed opposite to the image carrier and carrying a developer, and which develops the electrostatic latent image by applying a developing voltage including a DC component and an AC component to the developing member and supplying the developer from the developing member to a surface of the image carrier; a current measuring device that measures a current flowing through the charging member; 3. An image forming apparatus comprising: a control device that realizes the image forming control method according to claim 1.

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