Image forming apparatus

Abstract

To provide an image forming apparatus that can efficiently execute maintenance.SOLUTION: According to an embodiment, an image forming apparatus has a plurality of photoreceptors, an exposure unit, developing units, and a processor. The exposure unit irradiates the surfaces of the plurality of photoreceptors with rays of light according to images formed on the plurality of photoreceptors. The developing units supply toner to the surfaces of the plurality of photoreceptors on which electrostatic latent images are formed by the irradiation of the rays of light from the exposure unit. The processor adjusts, for each of the photoreceptors, a contrast potential for supplying the toner from the developing units to the electrostatic latent images formed on the surfaces of the plurality of photoreceptors, and when a contrast potential having a difference from the other contrast potentials exceeding a reference value is present, notifies a warning.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] Embodiments of the present invention relate to an image forming apparatus.

Background Art

[0002] Conventionally, maintenance of image forming apparatuses such as digital multifunction peripherals is performed by service personnel who visit the installation site. For such image forming apparatuses, it is desired that service personnel visit at an appropriate timing to perform maintenance efficiently.

[0003] On the other hand, an electrophotographic image forming apparatus forms a color image using a developer containing toners of a plurality of colors (for example, yellow, magenta, cyan, and black). An electrophotographic image forming apparatus adjusts, for each color, a contrast potential for developing an electrostatic latent image with toner of each color, so as to equalize the density (toner density) of an image of each color. In an image forming apparatus, if the developers of respective colors have substantially the same charging characteristics, a large difference between contrast potentials of the respective colors rarely occurs when the toner densities of the respective colors are equalized. In other words, in an electrophotographic image forming apparatus, when there is a large difference in contrast potential, some kind of problem often occurs.

[0004] However, conventional image forming apparatuses cannot detect a possibility of a failure or abnormality based on a difference in contrast potential between respective colors. Therefore, conventional image forming apparatuses cannot promote efficient maintenance by notifying of a failure or abnormality suggested by a difference in contrast potential between respective colors.

Prior Art Literature

Patent Literature

[0005]

Patent Literature 1

Summary of the Invention

Problem to be Solved by the Invention

[0006] The problem that this invention aims to solve is to provide an image forming apparatus that can perform maintenance efficiently. [Means for solving the problem]

[0007] According to the embodiment, the image forming apparatus is Control panel and It has multiple photoreceptors, an exposure unit, a developer unit, and a processor. The control panel includes a display unit. The exposure unit irradiates the surface of each of the multiple photoreceptors with light corresponding to the image to be formed on each of the multiple photoreceptors. The developer unit supplies toner to the surface of the multiple photoreceptors on which electrostatic latent images have been formed by the light irradiated by the exposure unit. The processor adjusts the contrast potential for supplying toner from the developer unit to the electrostatic latent images formed on the surface of each of the multiple photoreceptors, and if there is a contrast potential that exceeds a reference value in difference from other contrast potentials, The control panel will indicate that the difference in contrast potential exceeds the reference value. Issue a warning. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows an example of the configuration of a digital multifunction device as an image forming apparatus according to the embodiment. [Figure 2] Figure 2 shows an example of the printer configuration in a digital multifunction device as an image forming apparatus according to the embodiment. [Figure 3] Figure 3 is a block diagram showing an example of the configuration of a control system in a digital multifunction printer as an image forming apparatus according to the embodiment. [Figure 4] Figure 4 is a flowchart illustrating an example of image density adjustment operation in a digital multifunction printer as an image forming apparatus according to this embodiment. [Modes for carrying out the invention]

[0009] This embodiment will be described below with reference to the drawings. First, the configuration of the digital multifunction printer (MFP; Multi-Functional Peripheral) 1 as an image forming apparatus according to this embodiment will be described. Figure 1 is a block diagram showing an example configuration of a digital multifunction printer 1 as an image forming apparatus according to an embodiment. As shown in Figure 1, the digital multifunction device 1 includes a printer 2, an operation panel 3, a scanner 4, and a system controller 5, among other things.

[0010] Printer 2 is an image forming device that forms an image on a recording medium. The printer 2 provided in the digital multifunction device 1 is an image forming device that forms an image on a recording medium using an electrophotographic method. Printer 2 forms an image (toner image) on a recording medium such as paper using toner. The recording medium on which Printer 2 forms an image can be anything on which an image can be formed, and is not limited to paper; it may also be cloth, plastic film, or a sheet.

[0011] Scanner 4 is installed on top of the main unit of the digital multifunction printer 1. Scanner 4 is a device that optically reads images from documents. For example, scanner 4 reads images from documents placed on the document glass. Scanner 4 may also include a component that reads images from documents transported by an automatic document feeder (ADF).

[0012] The control panel 3 is the user interface. The control panel 3 has a display unit, a touch panel, and operation buttons. The control panel 3 displays operation instructions on the display unit. The control panel 3 receives operation instructions from the user via the touch panel and operation buttons. For example, the control panel 3 has a touch panel on the display screen of the display unit and detects the area on the display screen that the user touches.

[0013] The system controller 5 controls the entire digital multifunction device 1. The system controller 5 receives operation instructions input to the control panel 3 and controls the operation of each part. The system controller 5 also receives operation instructions from external devices connected via an interface and controls the operation of each part. For example, if the system controller 5 is instructed to form an image on the recording medium, it controls the printer 2 to perform image formation on the recording medium.

[0014] The following describes the configuration of printer 2. As shown in Figure 1, the printer 2 includes a media supply mechanism 13, a transport mechanism 15, multiple image forming stations SY, SM, SC, SK, an intermediate transfer belt 21, a secondary transfer roller 22, a support roller 23, a toner adhesion amount sensor 24, a transfer belt cleaner 25, and a fuser 26.

[0015] The media supply mechanism 13 has multiple paper feed cassettes 321, 322, and 323. The number of paper feed cassettes can be any number. Each paper feed cassette 321, 322, and 323 stores paper as the recording medium M. The paper used as the recording medium M stored in each paper feed cassette may be of different sizes or different types. Each paper feed cassette 321, 322, and 323 is equipped with a pickup roller 341, 342, and 343, respectively. The pickup rollers 341, 342, and 343 each pick up one sheet of paper as the recording medium from the paper feed cassette 321, 322, and 323. The pickup rollers 341, 342, and 343 each supply the picked-up recording medium M to the transport mechanism 15.

[0016] The conveyance mechanism 15 conveys a recording medium M. The conveyance mechanism 15 includes first conveyance rollers 521, 522, 523, a second conveyance roller 54, and a registration roller 56 on a conveyance path before image formation onto the recording medium M. In the conveyance mechanism 15, the first conveyance rollers 521, 522, 523 convey the recording medium M supplied by pickup rollers 341, 342, 343 to the second conveyance roller 54. In the conveyance mechanism 15, the second conveyance roller 54 further conveys the recording medium M to the registration roller 56.

[0017] The registration roller 56 of the conveyance mechanism 15 conveys the recording medium M to a secondary transfer position in accordance with the timing of transferring an image from an intermediate transfer belt 21 to the recording medium M at the secondary transfer position described later. The conveyance mechanism 15 forms the conveyance path so as to convey the recording medium M, onto which an image has been transferred from the intermediate transfer belt 21, to a fixing device 26. Furthermore, the conveyance mechanism 15 includes a third conveyance roller 58 for discharging a sheet to a paper discharge section, a conveyance mechanism for conveying the recording medium M to a reversing section that reverses the recording medium M, and the like.

[0018] Each of the image forming stations SY, SM, SC, SK forms an image with toner. In the present embodiment, the image forming station SY forms a yellow image. The image forming station SM forms a magenta image. The image forming station SC forms a cyan image. The image forming station SK forms a black image. Each of the image forming stations SY, SM, SC, SK transfers an image formed with toner onto the intermediate transfer belt 21, respectively.

[0019] The intermediate transfer belt 21 is a medium that holds images transferred by the respective image forming stations SY, SM, SC, SK. The intermediate transfer belt 21 is an endless belt as shown in FIG. 1. The intermediate transfer belt 21 moves in a direction indicated by arrow a in FIG. 1. The intermediate transfer belt 21 moves the images transferred by the respective image forming stations SY, SM, SC, SK to a position where a secondary transfer roller 22 and a support roller 23 face each other.

[0020] The secondary transfer roller 22 and the support roller 23 constitute a transfer section (secondary transfer section) that transfers an image from the intermediate transfer belt 21 to a recording medium. The position where the secondary transfer roller 22 faces the support roller 23 is a secondary transfer position where an image is transferred from the intermediate transfer belt 21 to a recording medium. The secondary transfer roller 22 and the support roller 23 sandwich the intermediate transfer belt 21 and the recording medium at the secondary transfer position.

[0021] The support roller 23 supports the intermediate transfer belt 21. The support roller 23 is a drive roller that drives the intermediate transfer belt 21. The secondary transfer roller 22 faces the support roller 23 with the intermediate transfer belt 21 interposed therebetween. The secondary transfer roller 22 transfers (secondary transfer) an image formed of toner on the transfer surface of the intermediate transfer belt 21 onto the surface of a recording medium.

[0022] The toner adhesion amount sensor 24 is a sensor that detects the toner amount (density). The toner adhesion amount sensor 24 detects the adhesion amount of toner on the intermediate transfer belt 21. The toner adhesion amount sensor 24 is disposed to face the transfer surface of the intermediate transfer belt 21. The toner adhesion amount sensor 24 is provided between the image transfer position (primary transfer position) by each image forming station and the secondary transfer position in the movement direction a of the intermediate transfer belt 21. The toner adhesion amount sensor 24 outputs the detected toner adhesion amount to the system controller 5.

[0023] As shown in FIG. 1, the transfer belt cleaner 25 is disposed between the secondary transfer position and the primary transfer position in the movement direction a of the intermediate transfer belt 21. The transfer belt cleaner 25 removes toner on the intermediate transfer belt 21. For example, the transfer belt cleaner 25 removes residual toner on the transfer surface of the intermediate transfer belt 21 after an image is transferred from the intermediate transfer belt 21 to a recording medium.

[0024] The fuser 26 fixes the image formed by the toner transferred to the recording medium onto the recording medium. The fuser 26 is positioned in the transport path of the recording medium after it has passed the secondary transfer position. The fuser 26 has opposing pressure rollers and heating rollers. The fuser 26 applies heat and pressure to the recording medium by transporting it between the opposing heating rollers and pressure rollers. The fuser 26 fixes the toner image transferred to the recording medium by heating under pressure.

[0025] Next, the configurations of each image forming station SY, SM, SC, and SK in the printer 2 as an image forming apparatus according to this embodiment will be described in detail. Figure 2 shows an example configuration of each image forming station SY, SM, SC, and SK in printer 2. Each image forming station SY, SM, SC, and SK includes, as shown in Figure 2, an exposure unit 100, a developer unit 110, a photoreceptor drum 122, a charger 126, a primary transfer roller 128, a photoreceptor cleaner 130, and a static eliminator 132, respectively. In this embodiment, each image forming station SY, SM, SC, and SK has the configuration shown in Figure 2.

[0026] The photoreceptor drum 122 is an image carrier having a photoreceptor layer 124 on its surface. The photoreceptor drum 122 rotates in a direction that matches the movement of the intermediate transfer belt 21 in direction a (the direction indicated by arrow b in Figure 2). Around the photoreceptor drum 122 are a charger 126, an exposure unit 100, a developer unit 110, a primary transfer roller 128, an intermediate transfer belt 21, a photoreceptor cleaner 130, and a static eliminator 132.

[0027] The charger 126 uniformly charges the photoreceptor layer 124 on the surface of the photoreceptor drum 122. For example, the charger 126 uniformly charges the photoreceptor layer 124 on the surface of the photoreceptor drum 122 with a negative polarity.

[0028] The exposure unit 100 forms an electrostatic pattern (electrostatic latent image) on the surface of the photoreceptor drum 122 that corresponds to the image. The exposure unit 100 irradiates the surface of the photoreceptor drum 122 with light L whose emission is controlled based on the image data. For example, the exposure unit 100 irradiates the surface of the photoreceptor drum 122 with light L emitted based on the image data via an optical system such as a polygon mirror. The exposure unit 100 may also include a device that emits multiple laser beams guided to the photoreceptor drums 122 of multiple image forming stations. Alternatively, the exposure unit 100 may be a light-emitting device provided for each of the multiple image forming stations.

[0029] The developer unit 110 develops the electrostatic latent image formed on the surface of the photoreceptor drum 122 with a developer. The developer unit 110 supplies developer D to the surface of the photoreceptor drum 122 that has been exposed by the exposure unit 100. Each developer unit 110 at each image forming station develops the image with its corresponding color. For example, the developer unit 110 at image forming station SY develops the electrostatic latent image on the photoreceptor drum 122 with yellow toner. The developer unit 110 at image forming station SM develops the electrostatic latent image on the photoreceptor drum 122 with magenta toner. The developer unit 110 at image forming station SC develops the electrostatic latent image on the photoreceptor drum 122 with cyan toner. The developer unit 110 at image forming station SK develops the electrostatic latent image on the photoreceptor drum 122 with black toner.

[0030] In the configuration example shown in Figure 2, the developer unit 110 includes a developer container 112, a developer roller 114, a first mixer 116, a second mixer 118, and a toner density sensor 120. The developer container 112 is a container for holding the developer D. The developer D is a mixture of a carrier made of magnetic fine particles and toner. When the developer D is stirred, the toner becomes triboelectrically charged. As a result, the toner adheres to the surface of the carrier by electrostatic force. Inside the developer container 112, a developing roller 114, a first mixer 116, a second mixer 118, and a toner density sensor are arranged.

[0031] The toner density sensor 120 is located inside the developer storage section 112. The toner density sensor 120 detects the toner density in the developer D stored in the developer storage section 112. The toner density is expressed, for example, as the ratio of toner to carrier (toner / carrier) in the developer D in the developer storage section 112. The system controller 5 controls the toner density detected by the toner density sensor 120 so that it reaches a predetermined value.

[0032] The developing roller 114 has, for example, a magnetic material (e.g., a magnet) in which positive and negative electrodes are arranged alternately along the circumference. The developing roller 114 rotates counterclockwise. The first mixer 116 and the second mixer 118 agitate the developer D in the developer container 112. The first mixer 116 and the second mixer 118 also transport the developer D. The second mixer 118, located below the developing roller 114, supplies the developer D to the surface of the developing roller 114.

[0033] The developer D adheres to the surface of the developing roller 114 in a raised state, according to the magnetic field distribution generated by the magnetic material of the developing roller 114. The developing roller 114 rotates while carrying the developer D. The layer of developer D attached to the developing roller 114 is limited to a predetermined thickness by a blade provided so that the gap between the blade and the surface of the developing roller 114 is a predetermined width. The developer D carried by the developing roller 114, which has been limited to a predetermined thickness by the blade, moves to a position (developing position) facing the surface of the photosensitive drum 122.

[0034] A developing roller 114, which carries the developer D, is subjected to a developing bias. The potential of the surface of the developing roller 114 is controlled by the developing bias. The toner in the developer D carried by the developing roller 114 adheres to the electrostatic latent image formed on the surface of the photoreceptor drum 122 due to the potential difference between the potential of the surface of the developing roller 114 and the potential of the electrostatic latent image formed on the surface of the photoreceptor drum 122. As the developing roller 114 rotates in a predetermined direction, the developer D carried by the developing roller 114 approaches the surface of the photoreceptor drum 122 on which the electrostatic latent image is formed. When the toner contained in the developer D carried by the developing roller 114 approaches the surface of the photoreceptor drum 122, it develops the electrostatic latent image on the photoreceptor drum 122. As a result, a toner image obtained by developing the electrostatic latent image with toner is formed on the photoreceptor drum 122.

[0035] Here, the potential difference between the potential of the surface of the developing roller 114 and the potential of the electrostatic latent image formed on the surface of the photoreceptor drum 122 is called the contrast voltage. The contrast voltage is related to the density of toner that moves from the developing roller 114 to the electrostatic latent image on the photoreceptor drum 122. In other words, the density of the toner image formed on the photoreceptor drum 122 is adjusted by controlling the contrast voltage. The contrast voltage is adjusted by controlling the development bias. Alternatively, the contrast voltage may be adjusted by controlling the potential of the electrostatic latent image.

[0036] The image developed with toner on the surface of the photoconductor drum 122 (toner image) moves to a position corresponding to the primary transfer roller 128 as the photoconductor drum 122 rotates. The primary transfer roller 128 faces the photoconductor drum 122 with the intermediate transfer belt 21 in between. The primary transfer roller 128 contacts the surface of the photoconductor drum 122 with the intermediate transfer belt 21 in between. The primary transfer roller 128 transfers the toner image on the surface of the photoconductor drum 122 to the intermediate transfer belt 21 (primary transfer).

[0037] The photoconductor cleaner 130 is positioned downstream of the location where the toner image on the surface of the photoconductor drum 122 is transferred onto the intermediate transfer belt 21, in the circumferential direction of the photoconductor drum 122. The photoconductor cleaner 130 removes the toner on the surface of the photoconductor drum 122. That is, the photoconductor cleaner 130 removes the toner remaining on the surface of the photoconductor drum 122 after the primary transfer of the toner image from the photoconductor drum 122 to the intermediate transfer belt 21 has been performed.

[0038] The static eliminator 132 is positioned downstream of the photoreceptor cleaner 130 in the circumferential direction of the photoreceptor drum 122. The static eliminator 132 irradiates light onto the surface of the photoreceptor drum 122. This allows the static eliminator 132 to remove any remaining charge from the photoreceptor layer 124 on the surface of the photoreceptor drum 122.

[0039] Next, the configuration of the control system in the digital multifunction printer 1, which is an image forming apparatus according to this embodiment, will be described. Figure 3 is a block diagram showing an example of the control system configuration in a digital multifunction printer 1, which is an image forming apparatus according to an embodiment. As shown in Figure 3, the system controller 5 includes a processor 101, ROM 102, RAM 103, storage device 104, and a communication interface (I / F) 105. Furthermore, the processor 101 of the system controller 5 is connected to various parts within the digital multifunction device 1 via various interfaces.

[0040] The processor 101 performs various processes by executing programs. The processor 101 is, for example, a CPU. The processor 101 is connected to ROM 102, RAM 103, storage device 104, and communication interface (I / F) 105, etc. The processor 101 is also connected to various parts of the printer 2, the operation panel 3, and the scanner 4 via the interface.

[0041] ROM102 is a non-rewritable, non-volatile memory. ROM102 operates as program memory for storing programs. RAM103 operates as working memory or buffer memory. The processor 101 performs various processes by executing programs stored in ROM102 or storage device 104 using RAM103.

[0042] The storage device 104 is a rewritable, non-volatile memory. For example, the storage device 104 is composed of a storage device such as an HDD (hard disk drive) or an SSD (solid state drive). The storage device 104 stores data such as control data, control programs, and configuration information. The storage device 104 also stores image data.

[0043] The communication interface 105 is an interface for data communication with external devices. For example, the communication interface 105 communicates with user terminals such as PCs and mobile devices via a network. The communication interface 105 may also be used to receive input such as image printing requests (print jobs) from user terminals such as PCs.

[0044] As shown in Figure 3, the printer 2 has a power supply 140 in addition to the configurations shown in Figures 1 and 2. The power supply 140 supplies voltage to the developer 110, the charger 126, the primary transfer roller 128, and the secondary transfer roller 22, respectively. As shown in Figure 3, the power supply 140 includes a high-voltage power supply 141, a developer bias transformer 142, a charge bias transformer 143, a primary transfer bias transformer 144, and a secondary transfer bias transformer 145. However, the developer bias transformer 142, the charge bias transformer 143, and the primary transfer bias transformer 144 are provided for each image forming station SY, SM, SC, and SK.

[0045] The high-voltage power supply 141 supplies high voltage to various transformers 142, 143, 144, and 145. High voltage refers to voltages ranging from several hundred volts to several kilovolts. The high-voltage power supply 141 generates high voltage from an input voltage of several tens of volts, for example.

[0046] The developing bias transformer 142 supplies the developing bias voltage to the developing unit 110. The developing bias transformer 142 converts the high voltage generated by the high-voltage power supply 141 into a developing bias voltage of a voltage value set by the system controller 5. The developing bias transformer 142 supplies the developing bias voltage specified by the system controller 5 to the developing unit 110.

[0047] The electrostatic bias transformer 143 supplies an electrostatic bias voltage to the charger 126. The electrostatic bias transformer 143 converts the high voltage generated by the high-voltage power supply 141 into an electrostatic bias voltage of a voltage value set by the system controller 5. The electrostatic bias transformer 143 supplies the electrostatic bias voltage specified by the system controller 5 to the charger 126.

[0048] The primary transfer bias transformer 144 supplies the primary transfer bias voltage to the primary transfer roller 128. The primary transfer bias transformer 144 converts the high voltage generated by the high-voltage power supply 141 into a primary transfer bias voltage of a voltage value set by the system controller 5. The primary transfer bias transformer 144 supplies the primary transfer bias voltage specified by the system controller 5 to the primary transfer roller 128.

[0049] The secondary transfer bias transformer 145 supplies a secondary transfer bias voltage to the secondary transfer roller 22. The secondary transfer bias transformer 145 converts the high voltage generated by the high-voltage power supply 141 into a secondary transfer bias voltage of a voltage value set by the system controller 5. The secondary transfer bias transformer 145 supplies a secondary transfer bias voltage of a value specified by the system controller 5 to the secondary transfer roller 22.

[0050] Next, the operation of the image forming process in the printer 2, which is an image forming apparatus according to this embodiment, will be described. The digital multifunction device 1 acquires an image to be formed on the recording medium M and performs image formation processing to print the acquired image onto the recording medium M using the printer 2. For example, when a copy is instructed on the control panel 3, the processor 101 of the system controller 5 executes the process of printing the image of the original document scanned by the scanner 4 onto the recording medium M using the printer 2.

[0051] When the system controller 5's processor 101 performs image formation processing, it takes in the recording medium M stored in the storage compartment via the media supply mechanism 13. The processor 101 then uses the transport mechanism 15 to transport the recording medium M supplied from the media supply mechanism 13 to the front of the registration roller 56 in the printer 2.

[0052] Furthermore, the processor 101 of the system controller 5 generates images to be formed by each image forming station SY, SM, SC, and SK based on the image to be printed on the recording medium M (print image). For example, the processor 101 generates images of each color (yellow, magenta, cyan, and black) to be formed by each image forming station SY, SM, SC, and SK from the print image. Once the processor 101 has generated images of each color from the print image, it causes each image forming station to form the generated images of each color.

[0053] In each image forming station SY, SM, SC, and SK, the charger 126 receives a charging bias voltage from the charging bias transformer 143 to charge the photoreceptor layer 124 of the photoreceptor drum 122. The exposure unit 100 irradiates the photoreceptor drum 122 of each image forming station SY, SM, SC, and SK with light that forms an electrostatic latent image corresponding to the image of each color. In each image forming station SY, SM, SC, and SK, an electrostatic latent image is formed on the photoreceptor layer 124 of the photoreceptor drum 122 by the light irradiated from the exposure unit 100.

[0054] Each image forming station SY, SM, SC, and SK develops the electrostatic latent image on the photoreceptor drum 122 using the toner of the respective color contained in the developer unit 110. In each image forming station SY, SM, SC, and SK, the developing roller 114 rotates while carrying the developer containing the respective color toner supplied from the developer container 112. The developing roller 114, which carries the developer, has a developing bias voltage applied to it from the developing bias transformer 142. The developer unit 110 supplies the toner in the developer carried by the developing roller 114 to the electrostatic latent image based on the potential difference (contrast potential) between the potential on the developing roller 114 and the electrostatic latent image on the photoreceptor drum 122.

[0055] In each image forming station SY, SM, SC, and SK, the photoreceptor drum 122 moves the image (toner image) developed by the developer 110 to a position facing the primary transfer roller 128 (primary transfer position). At the primary transfer position, the photoreceptor drum 122 faces the primary transfer roller 128 across the intermediate transfer belt 21. A primary transfer bias voltage from the primary transfer bias transformer 144 is applied to the primary transfer roller 128. The toner image on the photoreceptor drum 122 is transferred to the intermediate transfer belt 21 by the primary transfer roller to which the primary transfer bias voltage is applied at the primary transfer position. When forming a color image, each image forming station SY, SM, SC, and SK transfers the toner images of each color on the intermediate transfer belt 21 in a superimposed manner. As a result, a color image formed by superimposing the toner images of each color is transferred onto the intermediate transfer belt 21.

[0056] The intermediate transfer belt 21 moves the transferred toner image to a position opposite the secondary transfer roller 22 (secondary transfer position). The registration roller 56 feeds the recording medium M to the secondary transfer position in sync with the position and timing of the image transferred on the intermediate transfer belt 21. As a result, the secondary transfer roller 22 and the support roller 23 transport the recording medium M while sandwiching the overlapping intermediate transfer belt 21 and the recording medium M at the secondary transfer position. A secondary transfer bias voltage from the secondary transfer bias transformer 145 is applied to the secondary transfer roller 22. The toner image on the intermediate transfer belt 21 is transferred to the recording medium M by the secondary transfer roller 22, to which the secondary transfer bias voltage is applied at the secondary transfer position.

[0057] The recording medium M, having passed through the secondary transfer position, is transported to the fuser unit 26. The fuser unit 26 fixes the toner image transferred from the intermediate transfer belt 21 to the recording medium M at the secondary transfer position. The fuser unit 26 applies heat and pressure to the recording medium M on which the toner image has been transferred, fixing the toner image to the recording medium M. The recording medium M, having passed through the fuser unit 26, is discharged from the paper discharge section with the toner image fixed.

[0058] Next, we will describe the image density adjustment in the printer 2, which is an image forming apparatus according to the embodiment. The printer 2 of the digital multifunction device 1 adjusts the density of the image formed on the recording medium M by the image formation process described above. The density of the image formed on the recording medium M changes depending on the amount (density) of toner supplied to the electrostatic latent image from the developing roller 114 when developing the electrostatic latent image on the photoreceptor drum 122.

[0059] The density of the toner supplied to the electrostatic latent image from the developing roller 114 is adjusted by the contrast potential, which is the potential difference between the electrostatic latent image on the photoreceptor drum 122 and the developing roller 114. The processor 101 of the system controller 5 performs image density adjustment, which adjusts the density of the image of each color formed on the recording medium M by controlling the contrast potential for each color. Image density adjustment may be performed periodically or at any time.

[0060] In the digital multifunction printer 1 according to this embodiment, the processor 101 of the system controller 5 detects the difference in contrast potentials of each color after performing image density adjustment. The processor 101 issues a warning if there is a contrast potential whose difference from other contrast potentials exceeds a reference value.

[0061] Figure 4 illustrates an example of image density adjustment operation in the printer 2, which is an image forming apparatus according to this embodiment. The processor 101 of the system controller 5 performs image density adjustment to equalize the toner density of each color image formed by each image forming station SY, SM, SC, and SK. As part of the image density adjustment, the processor 101 transfers the toner images formed by each image forming station SY, SM, SC, and SK onto the intermediate transfer belt 21 (ACT 11).

[0062] In image density adjustment, the toner images formed by each image forming station SY, SM, SC, and SK may be images of a predetermined test pattern or any other image. The toner images of each color formed by each image forming station SY, SM, SC, and SK are transferred to the intermediate transfer belt 21 at their respective primary transfer positions.

[0063] The processor 101 of the system controller 5 transfers the toner images of each color onto the intermediate transfer belt 21, and then the toner density of each color is detected by the toner deposition amount sensor 24 (ACT12). The toner deposition amount sensor 24 detects the density (toner density) of the toner images of each color transferred onto the intermediate transfer belt 21. The toner deposition amount sensor 24 supplies the detection results indicating the toner density of each color to the processor 101.

[0064] The processor 101 determines whether or not to perform density adjustment for each image forming station based on the toner density of each color detected by the toner deposition amount sensor 24 (ACT 13). For example, the processor 101 determines whether or not the toner density of each color detected by the toner deposition amount sensor 24 is within a predetermined density range. The processor 101 determines that it will perform density adjustment for image forming stations of colors where the toner density is not within the predetermined density.

[0065] If there is an image forming station that has determined to perform density adjustment (ACT13, YES), the processor 101 adjusts the contrast potential of the image forming station to be adjusted (ACT14). For example, if the toner density of yellow (magenta, cyan, black) is not at a predetermined density, the processor 101 adjusts the contrast potential at image forming station SY (SM, SC, SK).

[0066] The processor 101 adjusts the contrast potential so that the toner density of the toner image formed by the image forming station reaches a predetermined density. For example, the processor 101 changes the contrast potential by controlling the development bias voltage applied by the development bias transformer 142 to the development roller 114. Alternatively, the system controller 5 may change the contrast potential by controlling the charge bias voltage applied by the charge bias transformer 143 to the charger 126. The system controller 5 may also change the contrast potential by controlling the light that the exposure unit 100 irradiates onto the photoreceptor drum 122.

[0067] When image density adjustment is performed, the processor 101 stores the adjustment results of the contrast potentials at each image forming station SY, SM, SC, and SK in the storage device 104 (ACT 15). For example, if the processor 101 adjusts the contrast potential at image forming station SY, it stores the adjustment result of the yellow contrast potential (the contrast potential corresponding to image forming station SY) in the storage device 104. Similarly, if the processor 101 adjusts the contrast potential at image forming stations SM (SC, SK), it stores the adjustment results of the magenta (cyan, black) contrast potentials in the storage device 104.

[0068] Furthermore, when the contrast potential is adjusted, the processor 101 calculates the difference in contrast potential at each image forming station SY, SM, SC, and SK (ACT16). The processor 101 calculates the difference between the contrast potential of each color (the contrast potential corresponding to each image forming station) and the contrast potential of other colors (the contrast potential corresponding to other image forming stations).

[0069] By calculating the difference in contrast potential for each color, the processor 101 determines whether there is a contrast potential that exceeds a reference value compared to the contrast potential of other colors (ACT17). The reference value compared to the difference in contrast potential is a threshold used to determine whether there is a possibility of a malfunction or abnormality in the digital multifunction device 1. An image forming station containing equipment with a malfunction or abnormality may have a larger difference in contrast potential compared to the contrast potential of other image forming stations.

[0070] For example, in a developer with a faulty toner density sensor, the toner concentration in the developer will not be maintained at the predetermined value. In an image forming station where the toner concentration in the developer is not maintained at the predetermined value, the contrast potential will be significantly altered in order to adjust the toner concentration to the predetermined value. The contrast potential of an image forming station, including one with a faulty toner density sensor, may differ significantly from the contrast potential of other image forming stations. In addition, the contrast potential of an image forming station where the charger, exposure unit, or developing roller is not functioning properly may differ significantly from the contrast potential of other stations.

[0071] If there are no contrast potentials that exceed a reference value when the difference between them exceeds the reference value (ACT17, NO), the processor 101 terminates the image density adjustment. In other words, if the difference in contrast potentials of each color is within the reference value, the processor 101 terminates the series of image density adjustment operations.

[0072] If any contrast potential difference exceeds a reference value (ACT17, YES), the processor 101 issues a warning that the contrast potential difference has exceeded the reference value (ACT18). The warning should prompt verification or maintenance of a malfunction suggested by the contrast potential difference exceeding the reference value. For example, the warning may be a notice of inspection or maintenance, or a message indicating a possible malfunction or abnormality in the digital multifunction printer. The warning may also include a message indicating the image forming station or color whose contrast potential difference exceeds the reference value.

[0073] Furthermore, even if the difference in contrast potential exceeds a standard value, the digital multifunction printer 1 can still form an image with normal density if the toner density of each color is adjusted to a normal value. For this reason, the processor 101 may continue the image formation process even if it issues a warning indicating that the difference in contrast potential has exceeded a standard value. This allows the digital multifunction printer to maintain image formation processing at normal density while simultaneously notifying the user that the difference in contrast potential has increased.

[0074] Furthermore, the processor 101 may notify a service technician or administrator that the difference in contrast potential exceeds a reference value without notifying the user. This allows the digital multifunction device 1 to provide the user with normal image formation processing while prompting service technicians to perform maintenance on abnormalities indicated by the difference in contrast potential.

[0075] For example, the processor 101 notifies a terminal device (external device) held by a service technician via the communication interface 105 that the contrast potential difference has exceeded a reference value. Alternatively, the processor 101 may also notify a system that manages the operating status of the digital multifunction printer via the communication interface 105 that the contrast potential difference has exceeded a reference value. Furthermore, the processor 101 may display on the operation panel 3 that the contrast potential difference has exceeded a reference value when a service technician or administrator logs in.

[0076] Furthermore, the processor 101 may perform the ACT11-15 process as image density adjustment and the ACT16-18 process in response to requests from service personnel, etc. This allows the digital multifunction printer 1 to notify service personnel of the possibility of a malfunction or abnormality based on the difference between the contrast potentials of each color.

[0077] As described above, the image forming apparatus according to the embodiment includes a plurality of photoreceptor drums, a plurality of developing rollers, and a system controller. Each photoreceptor drum carries an electrostatic latent image formed by light from an exposure unit. Each developing roller is positioned opposite each photoreceptor drum. Each developing roller supplies toner to the electrostatic latent image based on the contrast potential, which is the potential difference between it and the electrostatic latent image carried by the opposing photoreceptor drum. The system controller adjusts the contrast potential corresponding to each photoreceptor drum so that the density of the toner image developed on each photoreceptor drum is uniform. The system controller issues a warning if the difference in contrast potentials corresponding to each photoreceptor drum exceeds a reference value.

[0078] With the configuration described above, the image forming apparatus according to the embodiment can notify the user if a difference in contrast potential occurs when image density adjustment is performed, which may indicate a malfunction or abnormality. As a result, the image forming apparatus according to the embodiment allows a service technician to predict the location of a potential malfunction or abnormality based on the difference in contrast potential. Furthermore, by notifying the user that the difference in contrast potential exceeds a standard value, the image forming apparatus can facilitate prompt maintenance of the area where a malfunction or abnormality may have occurred.

[0079] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of symbols]

[0080] 1...Digital multifunction device (image forming apparatus), 2...Printer, 3...Operation panel, 4...Scanner, 5...System controller, 13...Media supply mechanism, 15...Transport mechanism, 21...Intermediate transfer belt (media), 22...Secondary transfer roller, 24...Toner adhesion amount sensor, 100...Explorer, 101...Processor, 104...Storage device, 105...Communication interface, 110...Developer, 112...Developer container, 114...Developer roller, 120...Toner density sensor, 122...Photoconductor drum, 124...Photoconductor layer, 126...Charger, 128...Primary transfer roller, 142...Developer bias transformer, 143...Charging bias transformer.

Claims

1. An operation panel equipped with a display unit, Multiple photoreceptors, An exposure unit that irradiates the surfaces of the plurality of photoreceptors with light corresponding to the image to be formed on the plurality of photoreceptors, A developer that supplies toner to the surfaces of the plurality of photoreceptors on which an electrostatic latent image has been formed by light irradiated by the exposure device, A processor that adjusts the contrast potential for supplying toner from the developer to the electrostatic latent image formed on the surface of the plurality of photoreceptors for each photoreceptor, and when there is a contrast potential whose difference from other contrast potentials exceeds a reference value, it notifies the control panel that the difference in the contrast potential has exceeded a reference value. An image forming apparatus having

2. The processor continues the image forming process even when it notifies the control panel of a warning message indicating that the difference in contrast potential has exceeded a reference value. The image forming apparatus according to claim 1.

3. The system comprises an image forming station that forms a yellow image, an image forming station that forms a magenta image, an image forming station that forms a cyan image, and an image forming station that forms a black image, and the warning includes a message indicating an image forming station whose difference in contrast potential from the other three image forming stations exceeds a reference value. The image forming apparatus according to claim 1 or 2.

4. The processor displays on the control panel that the difference in contrast potential exceeds a reference value when a service technician or administrator logs in. The image forming apparatus according to any one of claims 1 to 3.

Images