JP2023038973A - Image forming apparatus, and determination method - Google Patents

Abstract

To provide an image forming apparatus and a determination method that can improve the accuracy of determining the arrival of an execution timing of removal processing of removing water content from a surface of an image carrier.SOLUTION: An image forming apparatus comprises: a photoreceptor drum 31; an electrifying roller 32 that electrifies the photoreceptor drum 31 in response to the application of a first voltage equal to or more than a reference voltage; a developing roller 44 that supplies toner to an opposite area R1; a detection processing unit that detects the density of a specific toner image that is formed by the toner supplied to the opposite area R1 in a specific area on the photoreceptor drum 31 having passed through an opposite position P1 to the electrifying roller 32 to which a second voltage less than the reference voltage is applied; and a determination processing unit that, based on a result of detection performed by the detection processing unit, determines whether an execution timing of removal processing of removing water content from a surface of the photoreceptor drum 31 has arrived.SELECTED DRAWING: Figure 3

Description

The present invention relates to an electrophotographic image forming apparatus and a determination method executed by the image forming apparatus.

2. Description of the Related Art An image forming apparatus that forms an image by electrophotography includes an image carrier such as a photosensitive drum and a charging member such as a charging roller. The charging member is provided facing the image carrier, and charges the image carrier in response to application of a first voltage equal to or higher than a predetermined reference voltage.

In this type of image forming apparatus, discharge products generated by the discharge generated between the image carrier and the charging member may adhere to the surface of the image carrier. When the discharge product adhering to the surface of the image carrier absorbs moisture, the potential of the surface of the image carrier charged by the charging member is lowered, and the toner image formed on the surface is disturbed, which is called image deletion. A problem occurs.

On the other hand, when a second voltage lower than the reference voltage is applied to the charging member, a removing process for removing moisture from the surface of the image carrier is executed based on the current flowing through the charging member. An image forming apparatus that determines whether or not is known as a related technology (see Patent Document 1).

JP 2019-49635 A

However, when the second voltage is applied to the charging member, the current flowing through the charging member is very small, measured in microamperes. In addition, noise may enter the path of the current. Therefore, in the image forming apparatus according to the related art described above, it is not possible to determine with high accuracy whether or not it is time to execute the removal process.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus and a determination method capable of improving the accuracy of determination of arrival of execution timing of removal processing for removing moisture from the surface of an image carrier.

An image forming apparatus according to one aspect of the present invention includes an image carrier, a charging member, a developing member, a detection processing section, and a determination processing section. An electrostatic latent image is formed on the image carrier. The charging member is provided facing the image carrier, and charges the image carrier in response to application of a first voltage equal to or higher than a predetermined reference voltage. The developing member is provided facing the image carrier, and supplies toner to a region facing the image carrier. The detection processing unit is configured to form a specific area formed in a specific area passing through a position facing the charging member to which a second voltage less than the reference voltage is applied on the image carrier by the toner supplied to the facing area. Detect the density of the toner image. The determination processing unit determines whether or not it is time to perform removal processing for removing moisture from the surface of the image carrier, based on the detection result of the detection processing unit.

A determination method according to another aspect of the present invention includes an image carrier on which an electrostatic latent image is formed, and a first voltage that is equal to or higher than a predetermined reference voltage and that is provided facing the image carrier. an image forming apparatus comprising: a charging member that charges the image carrier in accordance with an image carrier; and a developing member that faces the image carrier and supplies toner to a region facing the image carrier, It includes a detection step and a determination step. In the detecting step, the specific toner is formed in a specific area passing through a position facing the charging member to which a second voltage less than the reference voltage is applied on the image carrier by the toner supplied to the facing area. Image density is detected. In the determination step, it is determined whether or not it is time to perform a removal process for removing moisture from the surface of the image carrier, based on the detection result obtained in the detection step.

According to the present invention, it is possible to improve the accuracy of determining the arrival of the execution timing of the removal process for removing moisture from the surface of the image carrier.

FIG. 1 is a cross-sectional view showing the configuration of an image forming apparatus according to an embodiment of the invention. FIG. 2 is a block diagram showing the system configuration of the image forming apparatus according to the embodiment of the invention. FIG. 3 is a cross-sectional view showing the configuration of the image forming unit of the image forming apparatus according to the embodiment of the invention. FIG. 4 is a flow chart showing an example of determination processing executed by the image forming apparatus according to the embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the following embodiment is an example that embodies the present invention, and does not limit the technical scope of the present invention.

[Configuration of Image Forming Apparatus 100]
First, the configuration of an image forming apparatus 100 according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG.

For convenience of explanation, the vertical direction in the installation state (the state shown in FIG. 1) in which the image forming apparatus 100 can be used is defined as the up-down direction D1. A front-rear direction D2 is defined with the left side of the image forming apparatus 100 shown in FIG. 1 as the front side. Further, the horizontal direction D3 is defined with reference to the front of the image forming apparatus 100 in the installed state.

The image forming apparatus 100 is a multifunction machine having a plurality of functions such as a scanning function for reading an image of a document, a printing function for forming an image based on image data, a facsimile function, and a copying function. The present invention may be applied to image forming apparatuses such as printers, facsimiles, and copiers capable of forming images by electrophotography.

As shown in FIGS. 1 and 2, the image forming apparatus 100 includes an ADF (Auto Document Feeder) 1, an image reading section 2, an image forming section 3, a paper feeding section 4, an operation display section 5, a storage section 6, and A control unit 7 is provided.

The ADF 1 conveys a document to be read by the scanning function. The ADF 1 includes a document set section, a plurality of transport rollers, a document presser, and a paper discharge section.

The image reading section 2 realizes the scanning function. The image reading unit 2 includes a platen, a light source, a plurality of mirrors, an optical lens, and a CCD (Charge Coupled Device).

The image forming section 3 realizes the printing function. Specifically, the image forming section 3 forms a color or monochrome image on a sheet supplied from the paper feeding section 4 according to the electrophotographic method.

The paper feeding unit 4 supplies sheets to the image forming unit 3 . The paper feed unit 4 includes a paper feed cassette, a manual feed tray, and a plurality of transport rollers.

The operation display unit 5 is a user interface of the image forming apparatus 100 . The operation display unit 5 includes a display unit such as a liquid crystal display for displaying various information according to control instructions from the control unit 7, and operation keys or a touch panel for inputting various information to the control unit 7 according to user operations. It has an operation part such as

The storage unit 6 is a nonvolatile storage device. For example, the storage unit 6 is a storage device such as non-volatile memory such as flash memory and EEPROM (registered trademark), SSD (Solid State Drive), or HDD (Hard Disk Drive).

The control unit 7 controls the image forming apparatus 100 as a whole. As shown in FIG. 2, the control unit 7 includes a CPU 11, a ROM 12, and a RAM 13. The CPU 11 is a processor that executes various kinds of arithmetic processing. The ROM 12 is a non-volatile storage device in which information such as control programs for causing the CPU 11 to execute various processes is stored in advance. The RAM 13 is a volatile or nonvolatile storage device used as a temporary memory (work area) for various processes executed by the CPU 11 . The CPU 11 comprehensively controls the image forming apparatus 100 by executing various control programs stored in advance in the ROM 12 .

Note that the control unit 7 may be a control unit provided separately from the main control unit that controls the image forming apparatus 100 in an integrated manner. Also, the control unit 7 may be configured by an electronic circuit such as an integrated circuit (ASIC).

[Configuration of Image Forming Unit 3]
Next, the configuration of the image forming section 3 will be described with reference to FIGS. 1 to 3. FIG. Here, FIG. 3 is a sectional view showing the configuration of the image forming unit 24. As shown in FIG. Note that in FIG. 3 , the energizing path between the charging roller 32 and the first voltage applying section 37 and the energizing path between the developing roller 44 and the second voltage applying section 38 are indicated by dashed lines.

As shown in FIG. 1, the image forming section 3 includes a plurality of image forming units 21 to 24, an optical scanning device 25, an intermediate transfer belt 26, a secondary transfer roller 27, a fixing device 28, and a paper discharge tray 29. . In addition, as shown in FIGS. 2 and 3, the image forming section 3 has a density sensor 30 .

The image forming unit 21 forms a Y (yellow) toner image. The image forming unit 22 forms a C (cyan) toner image. The image forming unit 23 forms an M (magenta) toner image. The image forming unit 24 forms a K (black) toner image. As shown in FIG. 1, the image forming units 21 to 24 are arranged along the front-rear direction D2 of the image forming apparatus 100 in the order of yellow, cyan, magenta, and black from the front side of the image forming apparatus 100 .

As shown in FIG. 3, the image forming unit 24 includes a photosensitive drum 31, a charging roller 32, a developing device 33, a primary transfer roller 34, and a drum cleaning section . Further, each of the image forming units 21 to 23 has the same configuration as the image forming unit 24. FIG. The four photosensitive drums 31 corresponding to the image forming units 21 to 24 are an example of a plurality of image carriers of the invention. Also, the four primary transfer rollers 34 corresponding to the image forming units 21 to 24 are examples of the plurality of transfer members of the present invention.

An electrostatic latent image is formed on the surface of the photosensitive drum 31 . For example, the photosensitive drum 31 has a photosensitive layer 31A made of an organic photosensitive material. The photosensitive drum 31 rotates in the rotation direction D4 shown in FIG. 3 by receiving a rotational driving force supplied from a motor (not shown). Thereby, the photosensitive drum 31 conveys the electrostatic latent image formed on the surface. The photosensitive layer 31A may be made of other photosensitive material such as amorphous silicon.

The charging roller 32 is provided facing the photoreceptor drum 31 and charges the photoreceptor drum 31 in response to application of a predetermined first voltage. Here, the first voltage is a voltage equal to or higher than a predetermined reference voltage. The reference voltage is the lowest voltage applied to the charging roller 32 that can cause discharge between the photosensitive drum 31 and the charging roller 32 . The charging roller 32 is an example of the charging member of the invention.

Specifically, the charging roller 32 is provided in contact with the photosensitive drum 31 . Also, the charging roller 32 is rotatably supported by the housing of the image forming unit 24 . The charging roller 32 is driven to rotate by the rotation of the photosensitive drum 31 . The charging roller 32 charges the surface of the photosensitive drum 31 to a predetermined positive charging potential in response to the application of the first voltage. In other words, the first voltage is a voltage that can charge the surface of the photosensitive drum 31 to the charging potential.

It should be noted that the charging member of the present invention may be a member provided apart from the photosensitive drum 31 . Also, the charging member of the present invention may be a member having a shape different from the roller shape.

The surface of the photosensitive drum 31 charged to the charging potential by the charging roller 32 is irradiated with light based on image data emitted from the optical scanning device 25 . As a result, an electrostatic latent image is formed on the surface of the photoreceptor drum 31 including an exposed area irradiated with the light emitted from the optical scanning device 25 and a non-exposed area not irradiated with the light.

The developing device 33 develops the electrostatic latent image formed on the surface of the photoreceptor drum 31 using developer containing toner and carrier.

As shown in FIG. 3 , the developing device 33 includes a housing 41 , a first conveying member 42 , a second conveying member 43 , a developing roller 44 and a regulation member 45 .

The housing 41 accommodates the first conveying member 42 , the second conveying member 43 , the developing roller 44 and the regulating member 45 . Further, the housing 41 has a circulating transport path through which the developer circulates. The circulation transport path includes a first transport path 41A (see FIG. 3) and a second transport path 41B (see FIG. 3) extending along the horizontal direction D3.

The first conveying member 42 conveys the developer contained in the first conveying path 41A in one of the left and right directions D3. Further, the first conveying member 42 agitates the developer to triboelectrically charge the toner and the carrier. For example, the toner is positively charged by triboelectrification with the carrier. For example, the first conveying member 42 is a screw-shaped member that is rotatable around a rotation axis extending in the left-right direction D3 in the first conveying path 41A.

The second conveying member 43 conveys the developer contained in the second conveying path 41</b>B in a direction opposite to the conveying direction of the first conveying member 42 . Further, the second conveying member 43 agitates the developer to triboelectrically charge the toner and the carrier. For example, the second conveying member 43 is a screw-shaped member that is rotatable around a rotation axis extending in the left-right direction D3 in the second conveying path 41B.

The developing roller 44 is provided facing the photoreceptor drum 31 and supplies the developer containing the toner and the carrier to a region R1 facing the photoreceptor drum 31 (see FIG. 3). Developing roller 44 is an example of the developing member of the present invention.

Specifically, the developing roller 44 supplies the toner charged to the same polarity as the charging roller 32 .

As shown in FIG. 3 , the developing roller 44 is provided facing the second conveying member 43 and the photosensitive drum 31 . The developing roller 44 scoops up the developer from the second conveying path 41B. The developer drawn up by the developing roller 44 forms a magnetic brush on the outer peripheral surface of the developing roller 44 due to the magnetic force of the magnetic poles provided inside the developing roller 44 . The developing roller 44 is rotatably supported by the housing 41 and rotates in the rotational direction D6 shown in FIG. 3 by receiving a rotational driving force supplied from a motor (not shown). As a result, the developing roller 44 conveys the magnetic brush formed on the outer peripheral surface to the facing area R1 (see FIG. 3). A predetermined developing bias voltage is applied to the developing roller 44 . As a result, the toner contained in the magnetic brush conveyed to the counter region R1 is supplied to the exposure region contained in the electrostatic latent image conveyed to the counter region R1, and the electrostatic latent image is developed (visualized). ) is done.

The regulating member 45 regulates the layer thickness of the magnetic brush formed on the outer peripheral surface of the developing roller 44 . As shown in FIG. 3, the regulating member 45 is downstream in the rotational direction D6 from the opposing region between the second conveying member 43 and the developing roller 44 and upstream in the rotational direction D6 from the opposing region R1. provided on the side. The regulating member 45 is provided to face the outer peripheral surface of the developing roller 44 so that a predetermined gap is formed between the regulating member 45 and the outer peripheral surface of the developing roller 44 .

The developing device 33 may include a magnet roller that draws up the developer from the second conveying path 41B and supplies the toner contained in the drawn-up developer to the developing roller 44 . In this case, the developing roller 44 may supply the toner to the facing area R1. Further, the developer may be a one-component developer that does not contain the carrier.

The primary transfer roller 34 transfers the toner image formed on the surface of the photosensitive drum 31 by the developing device 33 onto the intermediate transfer belt 26 . The primary transfer roller 34 moves between a contact position (see FIG. 3) where it contacts the inner peripheral surface of the intermediate transfer belt 26 and a separation position where it moves upward from the contact position and separates from the intermediate transfer belt 26. possible. When the four primary transfer rollers 34 corresponding to the image forming units 21 to 24 are moved to the separated positions, the tension of the intermediate transfer belt 26 is relaxed and the intermediate transfer belt 26 is separated from the four photosensitive drums 31 . The toner image formed on the photoreceptor drum 31 is transferred to the intermediate transfer belt 26 at the primary transfer position P2 (see FIG. 3) where the photoreceptor drum 31 and the intermediate transfer belt 26 are in contact with each other.

The drum cleaning section 35 cleans the surface of the photosensitive drum 31 . As shown in FIG. 3, the drum cleaning section 35 includes a cleaning member 35A and a conveying member 35B. The cleaning member 35A is a blade-shaped member provided in contact with the surface of the photoreceptor drum 31 . The cleaning member 35A removes deposits adhering to the surface of the photoreceptor drum 31 . The conveying member 35B conveys the deposits removed from the surface of the photosensitive drum 31 by the cleaning member 35A to a storage container (not shown).

The image forming section 3 includes a toner container 36 (see FIG. 1) corresponding to each of the image forming units 21-24. Further, the image forming section 3 includes a first voltage applying section 37 (see FIGS. 2 and 3) and a second voltage applying section 38 (see FIGS. 2 and 3) corresponding to each of the image forming units 21 to 24. .

Here, the toner container 36, the first voltage applying section 37, and the second voltage applying section 38 corresponding to the image forming unit 24 will be described. Note that FIG. 2 shows the first voltage applying section 37 and the second voltage applying section 38 corresponding to the image forming unit 24 .

The toner container 36 contains the K (black) toner. The toner container 36 supplies the K (black) toner to the developing device 33 .

The first voltage applying section 37 is a power supply that applies either the first voltage or a second voltage lower than the reference voltage to the charging roller 32 . The first voltage and the second voltage are positive DC voltages.

The second voltage applying section 38 applies the developing bias voltage to the developing roller 44 of the developing device 33 . The development bias voltage is a voltage containing a positive DC component and an AC component.

The optical scanning device 25 emits light based on image data toward the surface of the photosensitive drum 31 of each of the image forming units 21-24.

The intermediate transfer belt 26 is an endless belt member onto which the toner images formed on the surfaces of the photosensitive drums 31 of the image forming units 21-24 are transferred. The intermediate transfer belt 26 is stretched with a predetermined tension by a drive roller, a tension roller, and four primary transfer rollers 34 . The intermediate transfer belt 26 rotates in the rotation direction D5 shown in FIGS. 1 and 3 as the driving roller rotates with a rotational driving force supplied from a motor (not shown). The four photosensitive drums 31 corresponding to the image forming units 21 to 24 are arranged at regular intervals along the rotation direction D5 of the intermediate transfer belt 26 (see FIGS. 1 and 3). Therefore, the four primary transfer positions P2 (see FIG. 3) corresponding to the image forming units 21 to 24 are also arranged at regular intervals along the rotation direction D5 of the intermediate transfer belt . The intermediate transfer belt 26 is an example of a transfer-receiving body of the present invention. Also, the rotation direction D5 is an example of the movement direction of the present invention.

A secondary transfer roller 27 transfers the toner image transferred onto the surface of the intermediate transfer belt 26 onto a sheet supplied from the paper feed unit 4 .

The fixing device 28 fixes the toner image transferred onto the sheet by the secondary transfer roller 27 onto the sheet.

A sheet on which the toner image is fixed by the fixing device 28 is discharged to the discharge tray 29 .

The density sensor 30 is used to detect the density of the toner image transferred onto the outer peripheral surface of the intermediate transfer belt 26 . For example, the density sensor 30 includes a light emitting portion that emits light toward the outer peripheral surface of the intermediate transfer belt 26 and a light receiving portion that receives the light emitted from the light emitting portion and reflected by the outer peripheral surface of the intermediate transfer belt 26. is a reflective photosensor. As shown in FIG. 3, the density sensor 30 is arranged downstream of the image forming unit 24 in the rotational direction D5 of the intermediate transfer belt 26 and upstream of the secondary transfer roller 27 in the rotational direction D5. be.

The density sensor 30 is used to determine whether or not it is time to execute adjustment processing for adjusting predetermined image forming conditions. For example, the image forming condition is the developing bias voltage applied to the developing roller 44 . The image forming condition is any one of the first voltage applied to the charging roller 32, the intensity of light emitted from the optical scanning device 25, and the primary transfer voltage applied to the primary transfer roller 34. good too.

Note that the density sensor 30 may not be used for determining whether or not the execution timing of the adjustment process has come.

By the way, in the image forming apparatus 100 , discharge products generated by the discharge generated between the photoreceptor drum 31 and the charging roller 32 may adhere to the surface of the photoreceptor drum 31 . When the discharge product adhering to the surface of the photoreceptor drum 31 absorbs moisture, the potential of the surface of the photoreceptor drum 31 charged by the charging roller 32 decreases, and the toner image formed on the surface is disturbed. A problem occurs.

On the other hand, a removal process for removing moisture from the surface of the photosensitive drum 31 based on the charging current flowing through the charging roller 32 when the second voltage lower than the reference voltage is applied to the charging roller 32. An image forming apparatus that determines whether or not to execute is known as a related art.

However, when the second voltage is applied to the charging roller 32, the charging current flowing through the charging roller 32 is minute and measured in units of microamperes. In addition, noise may enter the path of the charging current. Therefore, in the image forming apparatus according to the related art described above, it is not possible to determine with high accuracy whether or not it is time to execute the removal process.

On the other hand, in the image forming apparatus 100 according to the embodiment of the present invention, it is possible to improve the accuracy of determining the arrival of the execution timing of the removal process, as described below.

[Configuration of control unit 7]
Next, the configuration of the control unit 7 will be described with reference to FIG.

As shown in FIG. 2 , the control section 7 includes a processing execution section 61 , a detection processing section 62 and a determination processing section 63 .

Specifically, the ROM 12 of the control unit 7 stores in advance a determination program for causing the CPU 11 to function as a processing execution unit 61 , a detection processing unit 62 and a determination processing unit 63 . The CPU 11 functions as the above-described units by executing the determination program stored in the ROM 12 .

The determination program is recorded in a computer-readable recording medium such as a CD, DVD, and flash memory, and may be read from the recording medium and stored in a storage device such as the storage unit 6 . Also, the processing execution unit 61, the detection processing unit 62, and the determination processing unit 63 may be configured by an electronic circuit such as an integrated circuit (ASIC).

In the following description, unless otherwise specified, each part included in the image forming unit 24 among the image forming units 21 to 24 and each part provided corresponding to the image forming unit 24 will be described as an example. The following description similarly applies to each of the image forming units 21-23.

The process execution unit 61 executes the removal process of removing moisture from the surface of the photoreceptor drum 31 . The removal process is a process different from the adjustment process.

For example, the removing process is a polishing process for polishing the surface of the photosensitive drum 31 using the toner supplied from the developing device 33 and the cleaning member 35A of the drum cleaning unit 35 . By the polishing treatment, the moisture-absorbed discharge products are removed from the surface of the photosensitive drum 31 . Therefore, moisture is removed from the surface of the photoreceptor drum 31 .

For example, the polishing process is performed in the following procedure. First, the primary transfer roller 34 is moved from the contact position to the separation position, and the intermediate transfer belt 26 is separated from the photosensitive drum 31 . Next, the image forming unit 24 is driven. As a result, the photosensitive drum 31 rotates in the rotation direction D4, and the developing roller 44 rotates in the rotation direction D6. Next, the developing bias voltage is applied to the developing roller 44 by the second voltage applying section 38 . As a result, the toner is supplied from the developing roller 44 to the surface of the photosensitive drum 31 . The cleaning member 35A polishes the surface of the photosensitive drum 31 supplied with the toner. It should be noted that voltage application by the first voltage application unit 37 and light emission by the optical scanning device 25 are stopped during execution of the polishing process.

The removing process may be a process of heating the surface of the photosensitive drum 31 using a heater capable of heating the surface.

The detection processing unit 62 passes through a position P1 (see FIG. 3) facing the charging roller 32 on the photosensitive drum 31 to which the second voltage is applied by the toner supplied to the facing region R1 (see FIG. 3). A density of a specific toner image formed in a specific area is detected.

Specifically, the detection processing section 62 forms the four specific toner images corresponding to the image forming units 21-24.

For example, the detection processing section 62 forms the specific toner image corresponding to the image forming unit 24 in the following procedure.

First, the detection processing section 62 drives the image forming unit 24 and the intermediate transfer belt 26 . As a result, the photosensitive drum 31 rotates in the rotation direction D4, the developing roller 44 rotates in the rotation direction D6, and the intermediate transfer belt 26 rotates in the rotation direction D5.

Next, the detection processing section 62 applies the first voltage to the charging roller 32 using the first voltage applying section 37 . As a result, the surface of the photosensitive drum 31 is charged to the charging potential. This process is performed to form a boundary between the downstream end in the rotation direction D4 and the area downstream of the end in the rotation direction D4 in the specific toner image.

Next, the detection processing section 62 switches the voltage applied to the charging roller 32 by the first voltage applying section 37 from the first voltage to the second voltage. Further, the detection processing unit 62 stops applying the second voltage at the timing when a predetermined specific time has elapsed from the start of application of the second voltage. The specific time is shorter than the calculated time obtained by dividing the interval between two primary transfer positions P2 (see FIG. 3) adjacent to each other along the rotational direction D5 by the transport speed of the toner image on the intermediate transfer belt 26. be.

Here, when the discharge product does not adhere to the surface of the photoreceptor drum 31 , no discharge occurs between the charging roller 32 to which the second voltage is applied and the photoreceptor drum 31 . Therefore, the potential of the specific region becomes zero.

On the other hand, when the discharge product adheres to the surface of the photoreceptor drum 31 , discharge may occur between the charging roller 32 to which the second voltage is applied and the photoreceptor drum 31 . Specifically, when the discharge product adhering to the surface of the photoreceptor drum 31 absorbs moisture, discharge occurs between the charging roller 32 and the photoreceptor drum 31 . The amount of charge transferred from the charging roller 32 to the photoreceptor drum 31 due to this discharge increases as the water content of the discharge product adhering to the surface of the photoreceptor drum 31 increases. That is, the higher the water content in the discharge product adhering to the surface of the photosensitive drum 31, the higher the potential of the specific region.

The specific area is conveyed to the counter area R1 (see FIG. 3) by the photosensitive drum 31. As shown in FIG. In the facing area R<b>1 , the specific area is developed with the toner supplied from the developing roller 44 . It should be noted that voltage application by the second voltage application unit 38 and light emission by the optical scanning device 25 are stopped during execution of the process for forming the specific toner image.

Here, when the potential of the specific region is zero, the toner adheres to the specific region and the specific region is colored with the toner. That is, the specific toner image having the same shape as the specific area is formed.

On the other hand, when the potential of the specific region exceeds zero, an electrostatic force repulsive to each other acts between the positively charged specific region and the positively charged toner, so that the potential of the specific region increases. Less of the toner adheres to that specific area than if it were zero. That is, the specific toner image is formed which has the same shape as the specific region and has a lower density than when the potential of the specific region is zero. The amount of the toner adhering to the specific region decreases as the potential of the specific region increases.

Then, the detection processing section 62 transfers the specific toner image to the intermediate transfer belt 26 using the primary transfer roller 34 . Thereby, the specific toner image is formed on the intermediate transfer belt 26 .

The detection processing section 62 simultaneously executes the above steps in the image forming units 21-24. As a result, the four specific toner images corresponding to the image forming units 21 to 24 are simultaneously transferred onto the intermediate transfer belt 26 . Further, the four specific toner images corresponding to the image forming units 21 to 24 are formed on the intermediate transfer belt 26 side by side along the rotation direction D5 of the intermediate transfer belt 26. FIG. Here, in the image forming apparatus 100 , the first voltage is applied to the charging roller 32 until immediately before the second voltage is applied to the charging roller 32 . Also, the specific time is set to a time shorter than the calculated time. Therefore, of the four specific toner images transferred onto the intermediate transfer belt 26, two specific toner images adjacent in the rotation direction D5 do not overlap.

After that, the detection processing section 62 uses the density sensor 30 to sequentially detect the density of each of the specific toner images.

Based on the result of detection by the detection processing unit 62, the determination processing unit 63 determines whether or not it is time to execute the removal processing.

Specifically, when the density of the specific toner image detected by the detection processing section 62 is lower than a predetermined reference density, the determination processing section 63 determines that the execution timing of the removal processing has arrived.

For example, when the density value indicating the density of the specific toner image detected by the detection processing unit 62 is lower than the reference density value corresponding to the reference density, the determination processing unit 63 determines that the execution timing of the removal processing has arrived. It is determined that In this case, the density value is a value that increases as the density of the specific toner image increases.

The reference density is a density lower than the density of the specific toner image formed in the specific area where the potential is zero. The reference density may be unchangeably determined when the image forming apparatus 100 is manufactured, or may be arbitrarily set according to a predetermined setting operation.

Further, the determination processing unit 63 determines for each photosensitive drum 31 whether or not the execution timing of the removal processing has come.

The process execution unit 61 executes the removal process when the determination processing unit 63 determines that the execution timing has arrived.

Here, when the judgment processing unit 63 judges that the execution timing of the removal processing has arrived, the processing execution unit 61 performs the removal at the execution time based on the difference between the density of the specific toner image and the reference density. Execute the process. Accordingly, it is possible to adjust the execution time of the removing process according to the amount of moisture on the surface of the photoreceptor drum 31 .

Note that the process execution unit 61 may execute the removal process for a predetermined execution time regardless of the difference between the density of the specific toner image and the reference density.

[Determination process]
The determination method of the present invention will be described below with reference to FIG. Here, steps S11, S12, .

The determination process is executed when a predetermined specific timing arrives. For example, the specific timing is the timing when the image forming apparatus 100 is powered on. Note that the specific timing is the timing at which printing processing for forming an image based on image data ends, and the operation mode of the image forming apparatus 100 shifts from a power saving mode in which power consumption is lower than that of the normal mode to the normal mode. It may be the timing at which the operation is performed, the timing at which a predetermined operation is accepted, or the like.

<Step S11>
First, in step S11, the control section 7 drives the image forming units 21 to 24 and the intermediate transfer belt .

<Step S12>
In step S12, the controller 7 applies the first voltage to each of the charging rollers 32 of the image forming units 21-24.

<Step S13>
In step S13, the controller 7 switches the voltage applied to each of the charging rollers 32 of the image forming units 21 to 24 from the first voltage to the second voltage. Further, the control unit 7 stops applying the second voltage at the timing when the specific time has passed since switching to the second voltage.

As a result, the specific toner image is formed on each of the photosensitive drums 31 of the image forming units 21-24.

<Step S14>
In step S14, the controller 7 transfers the specific toner image formed on the photosensitive drum 31 of each of the image forming units 21 to 24 onto the intermediate transfer belt 26. FIG.

<Step S15>
In step S<b>15 , the controller 7 uses the density sensor 30 to sequentially detect the density of each specific toner image transferred onto the intermediate transfer belt 26 . Here, the processing from step S11 to step S15 is an example of the detection step of the present invention, and is executed by the detection processing section 62 of the control section 7. FIG.

<Step S16>
In step S16, the control unit 7 determines for each specific toner image whether the density of the specific toner image detected in step S15 is lower than the reference density. Here, the process of step S16 is an example of the determination step of the present invention, and is executed by the determination processing section 63 of the control section 7. FIG.

Here, if the controller 7 determines that the density of any one or more of the specific toner images is lower than the reference density (Yes side of S16), the process proceeds to step S17. Further, if the density of any of the specific toner images is not lower than the reference density (No side of S16), the control section 7 terminates the determination process.

<Step S17>
In step S17, the control unit 7 executes the removing process for each of the photosensitive drums 31 corresponding to the specific toner images whose density is determined to be lighter than the reference density. Here, the processing of step S17 is executed by the processing execution unit 61 of the control unit 7. FIG.

As described above, in the image forming apparatus 100, the toner supplied to the opposing region R1 (see FIG. 3) causes the photosensitive drum 31 to face the charging roller 32 to which the second voltage is applied at the position P1 (see FIG. 3). ), the density of the specific toner image formed in the specific area is detected. Then, it is determined whether or not the execution timing of the removal process has come based on the detection result of the density of the specific toner image. With this configuration, it is determined whether or not the execution timing of the removal process has come based on the measurement result of the charging current flowing through the charging roller 32 when the second voltage is applied to the charging roller 32. Compared to , it is possible to improve the determination accuracy of the arrival of the execution timing of the removal processing by the amount that there is no determination error due to noise mixture.

Further, in the image forming apparatus 100, a density sensor 30 capable of detecting the density of the toner image transferred to the intermediate transfer belt 26 is used to detect the density of each of the plurality of specific toner images corresponding to the image forming units 21-24. is detected. Therefore, the number of density sensors 30 can be reduced compared to the configuration in which the density sensors 30 are provided in each of the image forming units 21-24.

Further, when the second voltage is applied to the charging roller 32, it is determined whether or not the execution timing of the removal process has come based on the measurement result of the charging current flowing through the charging roller 32. In the technique, when measuring a plurality of charging currents corresponding to a plurality of photoreceptor drums 31 using one ammeter, the charging roller 32 is adjusted so that each of the charging currents flows through the ammeter at different timings. It is necessary to shift the voltage application timing to each. On the other hand, according to the technique of the present invention, even when the density of a plurality of specific toner images corresponding to a plurality of photosensitive drums 31 is detected using one density sensor 30, the image forming units 21 to 24 It is not necessary to shift the timing of forming the specific toner image in each. That is, even if the image forming units 21 to 24 each execute the process of forming the specific toner images at the same time, the four specific toner images formed are transferred to different positions on the intermediate transfer belt 26, so that the density A sensor 30 allows the density of each of said specific toner images to be identifiably detected. Therefore, it is possible to simplify the processing content of the determination processing as compared with the conventional method.

The developing roller 44 may supply the toner charged to a polarity opposite to the charging polarity of the charging roller 32 . In this case, when the density of the specific toner image detected by the detection processing section 62 is higher than a predetermined density, the determination processing section 63 may determine that the execution timing of the removal processing has arrived.

The present invention may also be applied to an image forming apparatus that directly transfers toner images formed on each of the plurality of photosensitive drums 31 onto a sheet. That is, the transfer-receiving material of the present invention may be a sheet.

Also, the present invention may be applied to a monochrome printer having one photosensitive drum 31, one charging roller 32, and one developing roller 44. FIG.

1 ADF
2 Image reading unit 3 Image forming unit 4 Paper feeding unit 5 Operation display unit 6 Storage unit 7 Control unit 24 Image forming unit 25 Optical scanning device 26 Intermediate transfer belt 27 Secondary transfer roller 28 Fixing device 29 Paper discharge tray 30 Density sensor 31 Photoreceptor drum 32 Charging roller 33 Developing device 34 Primary transfer roller 35 Drum cleaning unit 36 Toner container 37 First voltage application unit 38 Second voltage application unit 44 Development roller 61 Processing execution unit 62 Detection processing unit 63 Judgment processing unit 100 Image formation Device

Claims (6)

an image carrier on which an electrostatic latent image is formed;
a charging member provided facing the image carrier and charging the image carrier in response to application of a first voltage equal to or higher than a predetermined reference voltage;
a developing member provided to face the image carrier and supplying toner to a region facing the image carrier;
Detecting density of a specific toner image formed in a specific area passing through a position facing the charging member to which a second voltage less than the reference voltage is applied on the image bearing member by the toner supplied to the facing area. a detection processing unit that
a determination processing unit that determines whether or not it is time to perform a removal process for removing moisture from the surface of the image carrier based on the detection result of the detection processing unit;
An image forming apparatus comprising: The developing member supplies the toner charged to the same polarity as the charging polarity of the charging member,
The determination processing unit determines that the execution timing of the removal processing has arrived when the density of the specific toner image detected by the detection processing unit is lower than a predetermined reference density.
The image forming apparatus according to claim 1. a processing execution unit configured to execute the removal processing for an execution time based on a difference between the density of the specific toner image and the reference density when the determination processing unit determines that the execution timing of the removal processing has arrived; ,
The image forming apparatus according to claim 2. a plurality of the image carriers arranged along the moving direction of the transfer receiving body;
a plurality of transfer members provided corresponding to the plurality of image bearing members for transferring the specific toner image formed on the image bearing members to the transfer receiving member;
a density sensor used to detect the density of each of the specific toner images transferred onto the transfer material;
with
The detection processing unit uses the density sensor to detect the density of each of the specific toner images,
The determination processing unit determines whether or not the execution timing of the removal processing has arrived for each of the image carriers.
The image forming apparatus according to any one of claims 1 to 3. The density sensor is used to determine whether or not it is time to execute an adjustment process different from the removal process, which is a process for adjusting predetermined image forming conditions.
The image forming apparatus according to claim 4. an image carrier on which an electrostatic latent image is formed; and a charging member provided facing the image carrier and charging the image carrier in response to application of a first voltage equal to or higher than a predetermined reference voltage. and a developing member that is provided to face the image carrier and supplies toner to a region facing the image carrier, wherein:
Detecting density of a specific toner image formed in a specific area passing through a position facing the charging member to which a second voltage less than the reference voltage is applied on the image bearing member by the toner supplied to the facing area. a detection step for
a determination step of determining whether or not it is time to perform a removal process for removing moisture from the surface of the image carrier, based on the detection result of the detection step;
Judgment method including.

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