JP2023028361A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that can deal with density unevenness by predicting occurrence of density unevenness having periodicity without involving toner consumption.SOLUTION: An image forming apparatus 100 comprises an image forming unit 6 and a control unit 10. The image forming unit 6 has image carriers 65, electrifying devices 63, an exposure device 61, and developing devices 64. The developing device 64 has a developer carrier 641 that carries developer including toner, and attaches the toner to an electrostatic latent image formed on the image carrier 65 by the exposure device 61 to form a toner image. The control unit 10 has an analyzing unit 101 and a changing unit 102. The analyzing unit 101 analyzes a waveform of a developing current that flows from the image carrier 65 toward the developer carrier 641 as a white part current while the image carrier is not exposed by the exposure device 61. The changing unit 102 changes setting of the image forming unit 6 according to a result of the analysis of the waveform performed by the analyzing unit 101.SELECTED DRAWING: Figure 3

Description

The present invention relates to an image forming apparatus.

The image forming apparatus described in Japanese Patent Application Laid-Open No. 2002-200000 continuously detects the development current when forming a patch image of oblique lines, and estimates the density unevenness in the main scanning direction.

JP 2015-175953 A

In the image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 2002-200013, there is a problem that toner is consumed for estimation of density unevenness.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of predicting the occurrence of periodic density unevenness without consuming toner and coping with the density unevenness.

An image forming apparatus of the present invention includes an image forming section and a control section. The image forming section forms an image on a recording medium. The control section controls the operation of the image forming section. The image forming section has an image carrier, a charging device, an exposure device, a developing device, a development power supply, and a current measuring section. The image carrier has a photosensitive layer formed on its surface. The charging device has a charging roller to which a charging voltage is applied, and charges the surface of the image carrier. The exposure device forms an electrostatic latent image by exposing the image carrier charged by the charging device. The developing device has a developer bearing member that bears a developer containing toner, and adheres the toner to the electrostatic latent image formed on the image bearing member to form a toner image. The development power source applies a development voltage to the developer carrier. The current measuring section measures a development current flowing between the developer carrier and the image carrier when the development voltage is applied to the developer carrier. The control unit has an analysis unit and a change unit. The analysis unit analyzes the waveform of the development current that flows from the image carrier toward the developer carrier as white background portion current in a state in which the exposure device does not perform the exposure. The changing section changes the setting of the image forming section according to the analysis result of the waveform by the analyzing section.

According to the present invention, there is provided an image forming apparatus capable of predicting the occurrence of periodic density unevenness without consuming toner and coping with the density unevenness.

1 is a schematic cross-sectional view showing an example of an image forming apparatus according to an embodiment; FIG. 2 is an enlarged cross-sectional view showing an example of a detailed configuration of a developing device; FIG. 2 is a block diagram showing an example of the circuit configuration of the image forming apparatus; FIG. 6 is a flowchart showing an example of processing of a control unit; 5 is a time chart showing an example of changes in the surface potential of a photoreceptor drum and changes in development current; (a), (b), and (c) are waveform diagrams each showing an example of periodic fluctuations of white background portion current.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

A configuration of an image forming apparatus 100 according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view showing an example of an image forming apparatus 100. As shown in FIG. The image forming apparatus 100 is, for example, a tandem color printer.

As shown in FIG. 1, the image forming apparatus 100 includes an operation section 2, a paper feeding section 3, a conveying section 4, a toner supply section 5, an image forming section 6, a transfer section 7, a fixing section 8, and a discharge section 9. Prepare.

The operation unit 2 receives instructions from the user. The operation section 2 includes a liquid crystal display 21 and a plurality of operation keys 22 . The liquid crystal display 21 displays various processing results, for example. The operation keys 22 include, for example, ten keys and a start key.

The paper feed unit 3 has a paper feed cassette 31 and a paper feed roller group 32 . The paper feed cassette 31 can accommodate a plurality of sheets of paper P. As shown in FIG. The paper feed roller group 32 feeds the paper P accommodated in the paper feed cassette 31 to the transport unit 4 one by one. The paper P corresponds to an example of a "recording medium".

The transport section 4 includes rollers and guide members. The transport section 4 extends from the paper feed section 3 to the discharge section 9 . The transport unit 4 transports the paper P from the paper feed unit 3 to the discharge unit 9 so as to pass through the image forming unit 6 and the fixing unit 8 .

The toner supply unit 5 supplies toner to the image forming unit 6 . The toner supply section 5 includes a first mounting section 51Y, a second mounting section 51C, a third mounting section 51M, and a fourth mounting section 51K.

A first toner container 52Y is attached to the first attachment portion 51Y. Similarly, the second toner container 52C is mounted on the second mounting portion 51C, the third toner container 52M is mounted on the third mounting portion 51M, and the fourth toner container 52K is mounted on the fourth mounting portion 51K. The configurations of the first mounting portion 51Y to the fourth mounting portion 51K are the same except for the type of toner container to be mounted.

Toner is stored in the first toner container 52Y to the fourth toner container 52K. In this embodiment, the first toner container 52Y contains yellow toner. Cyan toner is accommodated in the second toner container 52C. The third toner container 52M contains magenta toner. Black toner is accommodated in the fourth toner container 52K.

The image forming section 6 includes an exposure device 61, a first image forming unit 62Y, a second image forming unit 62C, a third image forming unit 62M, and a fourth image forming unit 62K, and forms an image on the paper P. do.

Each of the first to fourth image forming units 62Y to 62K has a charging device 63, a developing device 64, and a photosensitive drum 65. As shown in FIG. A photosensitive layer is formed on the surface of the photosensitive drum 65 . The photoreceptor drum 65 corresponds to an example of an "image carrier".

The charging device 63 and the developing device 64 are arranged along the peripheral surface of the photosensitive drum 65 . In this embodiment, the photoreceptor drum 65 rotates in the direction indicated by arrow R1 in FIG. 1 (clockwise).

The charging device 63 uniformly charges the photosensitive drum 65 to a predetermined polarity by discharging. In this embodiment, the charging device 63 charges the surface of the photosensitive drum 65 to positive polarity. The exposure device 61 irradiates the charged photosensitive drum 65 with laser light. Thereby, an electrostatic latent image is formed on the surface of the photosensitive drum 65 .

The developing device 64 develops the electrostatic latent image formed on the surface of the photosensitive drum 65 to form a toner image. Toner is supplied to the developing device 64 from the toner supply unit 5 . The developing device 64 supplies the surface of the photosensitive drum 65 with the toner supplied from the toner supply unit 5 . As a result, a toner image is formed on the surface of the photosensitive drum 65 .

In this embodiment, the developing device 64 included in the first image forming unit 62Y is connected to the first mounting portion 51Y. Therefore, yellow toner is supplied to the developing device 64 of the first image forming unit 62Y. Therefore, a yellow toner image is formed on the surface of the photosensitive drum 65 of the first image forming unit 62Y.

A developing device 64 included in the second image forming unit 62C is connected to the second mounting portion 51C. Therefore, cyan toner is supplied to the developing device 64 of the second image forming unit 62C. Therefore, a cyan toner image is formed on the surface of the photosensitive drum 65 of the second image forming unit 62C.

A developing device 64 included in the third image forming unit 62M is connected to the third mounting portion 51M. Therefore, magenta toner is supplied to the developing device 64 of the third image forming unit 62M. Therefore, a magenta toner image is formed on the surface of the photosensitive drum 65 of the third image forming unit 62M.

A developing device 64 included in the fourth image forming unit 62K is connected to the fourth mounting portion 51K. Therefore, black toner is supplied to the developing device 64 of the fourth image forming unit 62K. Therefore, a black toner image is formed on the surface of the photosensitive drum 65 of the fourth image forming unit 62K.

The transfer section 7 transfers the toner images formed on the surfaces of the photosensitive drums 65 of the first image forming unit 62Y to the fourth image forming unit 62K onto the paper P in an overlapping manner. In this embodiment, the transfer unit 7 superimposes and transfers each toner image onto the paper P by a secondary transfer method. Specifically, the transfer section 7 has four primary transfer rollers 71 , an intermediate transfer belt 72 , a driving roller 73 , a driven roller 74 and a secondary transfer roller 75 .

The intermediate transfer belt 72 is an endless belt stretched around four primary transfer rollers 71 , a driving roller 73 and a driven roller 74 . The intermediate transfer belt 72 is driven according to the rotation of the drive roller 73 . In FIG. 1, the intermediate transfer belt 72 rotates counterclockwise. The driven roller 74 is rotationally driven as the intermediate transfer belt 72 is driven.

The first to fourth image forming units 62Y to 62K are arranged to face the lower surface of the intermediate transfer belt 72 along the driving direction D of the lower surface of the intermediate transfer belt 72 . In the present embodiment, the first image forming unit 62Y to the fourth image forming unit 62K form the first image forming unit 62Y to the fourth image forming unit 62Y toward the downstream side in the driving direction D on the lower surface of the intermediate transfer belt 72. They are arranged in the order of unit 62K.

Each primary transfer roller 71 is arranged to face each photoreceptor drum 65 via the intermediate transfer belt 72 and is pressed toward each photoreceptor drum 65 . Therefore, the toner images formed on the surface of each photosensitive drum 65 are sequentially transferred onto the intermediate transfer belt 72 .

In this embodiment, a yellow toner image, a cyan toner image, a magenta toner image, and a black toner image are superimposed and transferred onto the intermediate transfer belt 72 in this order. A toner image in which a yellow toner image, a cyan toner image, a magenta toner image, and a black toner image are superimposed is hereinafter referred to as a "laminated toner image".

The secondary transfer roller 75 is arranged to face the drive roller 73 with the intermediate transfer belt 72 interposed therebetween. A secondary transfer roller 75 is pressed toward the driving roller 73 . Thereby, a transfer nip is formed between the secondary transfer roller 75 and the drive roller 73 . When the paper P passes through the transfer nip, the laminated toner image on the intermediate transfer belt 72 is transferred to the paper P. The sheet P onto which the laminated toner image has been transferred is conveyed toward the fixing section 8 by the conveying section 4 .

The fixing section 8 includes a heating member 81 and a pressure member 82 . A heating member 81 and a pressure member 82 are positioned opposite each other to form a fusing nip. The paper P conveyed from the image forming section 6 is pressed while being heated at a predetermined fixing temperature by passing through the fixing nip. As a result, the laminated toner image is fixed on the paper P. As shown in FIG. The paper P is conveyed from the fixing section 8 to the discharge section 9 by the conveying section 4 .

The discharge section 9 has a discharge roller pair 91 and a discharge tray 93 . The discharge roller pair 91 conveys the paper P to the discharge tray 93 through the discharge port 92 . A discharge port 92 is formed in the upper portion of the image forming apparatus 100 .

Next, a detailed configuration of the developing device 64 will be described with reference to FIGS. 1 and 2. FIG. FIG. 2 is an enlarged cross-sectional view showing an example of the detailed configuration of the developing device 64. As shown in FIG. In FIG. 2, the photoreceptor drum 65 is illustrated by a chain double-dashed line for easy understanding.

As shown in FIG. 2, the developing device 64 has a developing roller 641 , a first stirring screw 643 , a second stirring screw 644 and a blade 645 inside a developer container 640 . Specifically, the developing roller 641 is arranged to face the second stirring screw 644 . Blade 645 is arranged to face developing roller 641 .

The developer container 640 is partitioned into a first stirring chamber 640a and a second stirring chamber 640b by a partition wall 640c. The partition wall 640 c extends in the axial direction of the developing roller 641 . The first agitation chamber 640a and the second agitation chamber 640b communicate with each other on the outside of both ends in the longitudinal direction of the partition wall 640c.

A first stirring screw 643 is arranged in the first stirring chamber 640a. A magnetic carrier is accommodated in the first stirring chamber 640a. Nonmagnetic toner is supplied to the first stirring chamber 640a through a toner supply port 640h.

A second stirring screw 644 is arranged in the second stirring chamber 640b. A magnetic carrier is accommodated in the second stirring chamber 640b.

The toner is stirred by the first stirring screw 643 and the second stirring screw 644 and mixed with the carrier. As a result, a two-component developer consisting of carrier and toner is formed.

The first stirring screw 643 and the second stirring screw 644 circulate and stir the developer between the first stirring chamber 640a and the second stirring chamber 640b. As a result, the toner is charged to a predetermined polarity. In this embodiment, the toner is charged to a positive polarity.

The developing roller 641 is composed of a non-magnetic rotating sleeve 641a and a magnet body 641b. The magnet body 641b is fixedly arranged inside the rotary sleeve 641a. The magnet body 641b includes multiple magnetic poles. The developer is attracted to the developing roller 641 by the magnetic force of the magnet body 641b. As a result, a magnetic brush is formed on the surface of the developing roller 641 . The developing roller 641 corresponds to an example of a "developer carrier".

In this embodiment, the developing roller 641 rotates in the direction indicated by arrow R2 (counterclockwise) in FIG. The developing roller 641 conveys the magnetic brush to a position facing the blade 645 by rotating. The blade 645 is arranged so that a gap is formed between it and the developing roller 641 . Accordingly, the thickness of the magnetic brush is defined by blade 645 . The blade 645 is arranged on the upstream side in the rotation direction of the magnetic roller 642 from the position where the developing roller 641 and the photosensitive drum 65 face each other.

The magnetic brush formed on the surface of developing roller 641 is conveyed to a position facing photosensitive drum 65 . As a result, the developing device 64 attaches toner to the electrostatic latent image carried on the photosensitive drum 65 to form a toner image.

The image forming section 6 further includes a development power source 648 and a current measuring section 646 .

A developing power supply 648 applies a predetermined developing voltage to the developing roller 641 . The development voltage includes, for example, a DC component and an AC component. The current measuring section 646 is connected between the developing power supply 648 and the developing roller 641 to measure the developing current flowing between the developing roller 641 and the photosensitive drum 65 .

The charging device 63 has a charging roller 631 . A predetermined charging voltage is applied to the charging roller 631 . The charging voltage includes, for example, a DC component and an AC component.

Next, the circuit configuration of the image forming apparatus 100 will be described with reference to FIGS. 1 to 3. FIG. FIG. 3 is a block diagram showing an example of the circuit configuration of the image forming apparatus 100. As shown in FIG.

As shown in FIG. 3 , the image forming apparatus 100 further includes a control section 10 and a storage section 11 .

The storage unit 11 includes a storage device and stores data and computer programs. The storage unit 11 includes a main storage device such as a semiconductor memory and an auxiliary storage device such as a hard disk drive.

The control unit 10 includes a processor such as a CPU (Central Processing Unit), and controls each component of the image forming apparatus 100 by executing computer programs stored in the storage unit 11 . In particular, the control section 10 controls operations of the operation section 2 and the image forming section 6 . Further, the control unit 10 functions as an analysis unit 101 and a change unit 102 by executing computer programs stored in the storage unit 11 .

The analysis unit 101 analyzes the waveform of the development current that flows from the photosensitive drum 65 toward the development roller 641 as the white background portion current in a state where the exposure device 61 does not expose.

The changing unit 102 changes the setting of the image forming unit 6 according to the analysis result of the waveform by the analyzing unit 101 .

Next, processing of the control unit 10 will be described with reference to FIGS. 1 to 4. FIG. FIG. 4 is a flowchart showing an example of processing of the control unit 10. As shown in FIG.

Step S101: As shown in FIG. 4, the controller 10 analyzes the waveform of the developing current during the aging operation. During the aging operation, the white background portion current from the photosensitive drum 65 to the developing roller 641 is measured as the developing current. When the process of step S101 is completed, the process of the control unit 10 proceeds to step S103.

Step S<b>103 : The control unit 10 determines whether or not the period of the waveform of the white background portion current indicates the period of current fluctuation corresponding to the operation of the charging roller 631 . When the controller 10 determines that a current variation corresponding to the operation of the charging roller 631 has been detected (Yes in step S103), the process of the controller 10 proceeds to step S105. When the control unit 10 determines that the current fluctuation corresponding to the operation of the charging roller 631 has not been detected (No in step S103), the processing of the control unit 10 proceeds to step S107.

Step S105: The controller 10 sets the magnitude of at least one of the DC component and the AC component (DC/AC bias value) of the charging voltage applied to the charging roller 631 according to the amplitude of the waveform of the white background portion current. to change. When the process of step S105 is completed, the process of the control unit 10 ends.

Step S<b>107 : The control unit 10 determines whether or not the period of the white background current waveform indicates the period of current fluctuation corresponding to the operation of the photosensitive drum 65 . If the controller 10 determines that a current variation corresponding to the operation of the photosensitive drum 65 has been detected (Yes in step S107), the process of the controller 10 proceeds to step S105. If the control unit 10 determines that the current variation corresponding to the operation of the photosensitive drum 65 has not been detected (No in step S107), the process of the control unit 10 proceeds to step S109.

Step S<b>109 : The control unit 10 determines whether or not the period of the white background current waveform indicates the period of the current fluctuation corresponding to the operation of the developing roller 641 . If the controller 10 determines that a current variation corresponding to the operation of the developing roller 641 has been detected (Yes in step S109), the process of the controller 10 proceeds to step S111. When the control unit 10 determines that the current fluctuation corresponding to the operation of the developing roller 641 has not been detected (No in step S109), the processing of the control unit 10 ends.

Step S111: The control unit 10 changes the setting of the magnitude of the AC component (Vpp) of the developing voltage applied to the developing roller 641 by the developing power source 648 according to the amplitude of the waveform of the white background portion current. When the process of step S111 is completed, the process of the control unit 10 ends.

Next, the white background portion current will be described with reference to FIGS. 1 to 5. FIG. FIG. 5 is a time chart showing an example of changes in the surface potential of the photosensitive drum 65 and changes in the development current. Here, it is assumed that the DC component of the developing voltage applied to the developing roller 641 by the developing power supply 648 is 130V, for example.

As shown in FIG. 5, when the drive is stopped before time t1, the surface potential of the photosensitive drum 65 is 0 V, and the development current is 0 μA.

The aging operation starts at time t1 prior to the start of printing at time t2. During the aging operation, the surface potential of the photosensitive drum 65 in the non-exposed state indicates 200V, for example. Since the surface potential (200 V) of the photoreceptor drum 65 is higher than the DC component (130 V) of the developing voltage, the blank area current (negative current) flowing from the photoreceptor drum 65 toward the developing roller 641 is measured as the development current. be.

Printing is in progress from time t2 to time t3. During printing, the surface potential of the photosensitive drum 65 in the exposed state indicates, for example, 20V. Since the surface potential (20 V) of the photosensitive drum 65 is lower than the DC component (130 V) of the developing voltage, the developing current (positive current) flowing from the developing roller 641 to the photosensitive drum 65 is measured.

A period from time t3 to time t4 is a period of aging operation after printing. The period of aging operation after printing is longer than the period of aging operation before printing from time t1 to time t2. During the aging operation after printing, the white background current flowing from the photosensitive drum 65 to the developing roller 641 is also measured as the developing current. The control unit 10 analyzes the waveform of the blank area current during the aging operation after printing.

After time t4, the surface potential of the photosensitive drum 65 indicates 0 V and the development current indicates 0 .mu.A, returning to the drive stop state.

Next, with reference to FIGS. 6(a) to 6(c), a specific example of the periodic variation of the white background portion current will be described. 6(a), 6(b), and 6(c) are waveform diagrams each showing an example of periodic fluctuations of the white background portion current.

According to FIG. 6A, the period PA of the white background portion current waveform indicates the period of current fluctuation corresponding to the operation of the charging roller 631 . In this case, the setting of the magnitude of at least one of the DC component and the AC component (DC/AC bias value) of the charging voltage applied to the charging roller 631 is changed according to the amplitude AA of the waveform of the white background portion current. be done. As a result, periodic density unevenness caused by the operation of the charging roller 631 is suppressed.

According to FIG. 6B, the period PB of the waveform of the current in the white background indicates the period of current fluctuation corresponding to the operation of the photosensitive drum 65 . In this case, the setting of the magnitude of at least one of the DC component and the AC component (DC/AC bias value) of the charging voltage applied to the charging roller 631 is changed according to the amplitude AB of the white background current waveform. be done. As a result, periodic density unevenness caused by the operation of the photosensitive drum 65 is suppressed.

According to FIG. 6C, the period PC of the white background portion current waveform indicates the period of current fluctuation corresponding to the operation of the developing roller 641 . In this case, the setting of the magnitude of the AC component (Vpp) of the developing voltage applied to the developing roller 641 by the developing power source 648 is changed according to the amplitude AC of the waveform of the white background portion current. As a result, periodic density unevenness caused by the operation of the developing roller 641 is suppressed.

According to the embodiment, there is provided an image forming apparatus 100 capable of predicting the occurrence of periodic density unevenness without consuming toner and coping with the density unevenness. Moreover, since the analysis target is the developing current during the aging operation, not during printing, the decrease in productivity is suppressed.

The embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to the above-described embodiments, and can be implemented in various aspects without departing from the gist of the present invention. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be omitted from all components shown in the embodiments. In order to facilitate understanding, the drawings mainly show each component schematically, and the number of each component shown in the figure may differ from the actual number for convenience of drawing preparation. Also, each component shown in the above embodiment is an example and is not particularly limited, and various modifications are possible within a range that does not substantially deviate from the effects of the present invention.

INDUSTRIAL APPLICABILITY The present invention can be used in the field of image forming apparatuses.

6 image forming unit 10 control unit 61 exposure device 63 charging device 64 developing device 65 photosensitive drum (image carrier)
100 Image forming apparatus 101 Analysis unit 102 Change unit 631 Charging roller 641 Development roller (developer carrier)
646 Current measuring unit 648 Development power supply P Paper (recording medium)

Claims (4)

an image forming unit that forms an image on a recording medium;
a control unit that controls the operation of the image forming unit;
with
The image forming unit
an image carrier having a photosensitive layer formed on its surface;
a charging device having a charging roller to which a charging voltage is applied and charging the surface of the image carrier;
an exposure device that forms an electrostatic latent image by exposing the image carrier charged by the charging device;
a developing device having a developer carrier that carries a developer containing toner, and forming a toner image by causing the toner to adhere to the electrostatic latent image formed on the image carrier;
a development power supply that applies a development voltage to the developer carrier;
a current measuring unit for measuring a development current flowing between the developer carrier and the image carrier when the development voltage is applied to the developer carrier;
has
The control unit
an analysis unit that analyzes the waveform of the development current that flows from the image carrier toward the developer carrier as white background portion current in a state in which the exposure device does not perform the exposure;
a changing unit that changes the setting of the image forming unit according to the analysis result of the waveform by the analyzing unit;
An image forming apparatus having When the period of the waveform indicates the period of current fluctuation corresponding to the operation of the charging roller, the changing unit changes the magnitude of at least one of the DC component and the AC component of the charging voltage to the waveform. 2. The image forming apparatus according to claim 1, wherein the amplitude is changed. When the period of the waveform indicates the period of the current fluctuation corresponding to the operation of the image carrier, the changing section changes the setting of the magnitude of at least one of the DC component and the AC component of the charging voltage to the waveform. 2. The image forming apparatus according to claim 1, wherein the amplitude is changed according to the amplitude of . The changing unit changes the setting of the magnitude of the AC component of the developing voltage according to the amplitude of the waveform when the period of the waveform indicates the period of current fluctuation corresponding to the operation of the developer carrier. 2. The image forming apparatus according to claim 1, wherein:

Images