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 an image forming apparatus such as a digital multi-function peripheral has been performed by a service technician who visits the installation location. For such an image forming apparatus, it is desirable that a service technician visit at an appropriate timing and 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, black). The electrophotographic image forming apparatus adjusts the contrast potential for developing an electrostatic latent image with each color toner so as to equalize the density (toner density) of the image of each color. In an image forming apparatus, if the developers of each color have substantially the same charging characteristics, the difference in the contrast potential of each color is less likely to increase in a state where the toner densities of each color are equalized. In other words, in an electrophotographic image forming apparatus, when the difference in the contrast potential is large, there are often some malfunctions.

[0004] However, a conventional image forming apparatus cannot detect that there is a possibility of a failure or an abnormality based on the difference in the contrast potential of each color. For this reason, a conventional image forming apparatus cannot promote efficient maintenance by notifying a failure or an abnormality suggested by the difference in the contrast potential of each color.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The problem to be solved by the present invention is to provide an image forming apparatus capable of efficiently performing maintenance.

Means for Solving the Problem

[0007] According to an embodiment, an image forming apparatus includes a plurality of photoreceptors, an exposure device, a developing device, and a processor. The exposure device irradiates the surfaces of the plurality of photoreceptors with light corresponding to an image to be formed on the plurality of photoreceptors, respectively. The developing device supplies toner to the surfaces of the plurality of photoreceptors on which electrostatic latent images are formed by the light irradiated by the exposure device. The processor adjusts, for each photoreceptor, a contrast potential for supplying toner to the electrostatic latent images formed on the surfaces of the plurality of photoreceptors from the developing device, and notifies a warning when there is a contrast potential whose difference from other contrast potentials exceeds a reference value.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0009] Hereinafter, this embodiment will be described with reference to the drawings. First, the configuration of a digital multi-function peripheral (MFP) 1 as an image forming apparatus according to an embodiment will be described. FIG. 1 is a block diagram showing a configuration example of a digital multifunction peripheral 1 as an image forming apparatus according to an embodiment. As shown in FIG. 1, the digital multifunction peripheral 1 includes a printer 2, an operation panel 3, a scanner 4, and a system controller 5.

[0010] The printer 2 is an image forming apparatus that forms an image on a recording medium. The printer 2 included in the digital multifunction peripheral 1 is an image forming apparatus that forms an image on a recording medium by an electrophotographic method. The printer 2 forms an image (toner image) on a recording medium such as paper with toner. The recording medium on which the printer 2 forms an image may be any medium on which an image can be formed, and is not limited to paper, and may be cloth, a plastic film, or a sheet.

[0011] The scanner 4 is installed on the upper part of the main body of the digital multifunction peripheral 1. The scanner 4 is a device that optically reads an image of a document. For example, the scanner 4 reads an image of a document set on the document table glass. Further, the scanner 4 may be configured to include a device that reads an image of a document conveyed by an automatic document feeder (ADF).

[0012] The operation panel 3 is a user interface. The operation panel 3 includes a display unit (display), a touch panel, and operation buttons. The operation panel 3 displays operation guidance and the like on the display unit. The operation panel 3 receives operation instructions from the user via the touch panel and operation buttons. For example, the operation panel 3 is provided with a touch panel on the display screen of the display unit, and detects a part touched by the user on the display screen of the display unit.

[0013] The system controller 5 controls the entire digital multi-function peripheral 1. The system controller 5 receives the operation instructions input to the operation panel 3 and controls the operations of each part. Also, the system controller 5 receives the operation instructions from an external device connected via an interface and controls the operations of each part. For example, when image formation on a recording medium is instructed, the system controller 5 controls the printer 2 to cause the printer 2 to perform image formation on the recording medium.

[0014] Hereinafter, the configuration of the printer 2 will be described. As shown in FIG. 1, the printer 2 includes a medium supply mechanism 13, a conveyance mechanism 15, a plurality of 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 fixing device 26.

[0015] The medium supply mechanism 13 includes a plurality of paper feed cassettes 321, 322, 323. The number of paper feed cassettes may be any number. Each of the paper feed cassettes 321, 322, 323 stores paper as the recording medium M. The paper as the recording medium M stored in each paper feed cassette may accommodate papers of different sizes or different types. Pickup rollers 341, 342, 343 are respectively arranged in the paper feed cassettes 321, 322, 323. The pickup rollers 341, 342, 343 take out one sheet of paper as the recording medium from the paper feed cassettes 321, 322, 323 one by one. The pickup rollers 341, 342, 343 supply the taken-out recording medium M to the conveyance mechanism 15.

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

[0017] The registration roller 56 of the transport mechanism 15 transports the recording medium M to the secondary transfer position according to the timing of transferring the image from the intermediate transfer belt 21 to the recording medium M at the secondary transfer position described later. The transport mechanism 15 configures the transport path to transport the recording medium M with the image transferred from the intermediate transfer belt 21 to the fixing device 26. Further, the transport mechanism 15 includes a third transport roller 58 for discharging the paper to the paper discharge unit, and a transport mechanism for transporting the recording medium M to the inversion unit that inverts the recording medium M.

[0018] Each image forming station 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 image forming station SY, SM, SC, SK transfers the image formed with toner to the intermediate transfer belt 21.

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

[0020] The secondary transfer roller 22 and the support roller 23 constitute a transfer unit (secondary transfer unit) that transfers an image from the intermediate transfer belt 21 to the recording medium. The position where the secondary transfer roller 22 and the support roller 23 face each other is the secondary transfer position where the image is transferred from the intermediate transfer belt 21 to the 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 driving 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 transfers) the image formed by the toner on the transfer surface of the intermediate transfer belt 21 onto the surface of the 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 the 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 transfer position (primary transfer position) of the image by each image forming station and the secondary transfer position in the moving 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 moving direction a of the intermediate transfer belt 21. The transfer belt cleaner 25 removes the toner on the intermediate transfer belt 21. For example, the transfer belt cleaner 25 removes the remaining toner on the transfer surface of the intermediate transfer belt 21 after the image is transferred from the intermediate transfer belt 21 to the recording medium.

[0024] The fixing device 26 fixes the image formed by the toner transferred onto the recording medium onto the recording medium. The fixing device 26 is disposed on the conveyance path of the recording medium after it passes through the secondary transfer position. The fixing device 26 has a pair of opposing pressure roller and heating roller. The fixing device 26 applies heat and pressure to the recording medium by conveying it between the opposing heating roller and pressure roller. The fixing device 26 fixes the toner image transferred onto the recording medium by heating in a pressurized state.

[0025] Next, the configurations of the respective image forming stations SY, SM, SC, and SK in the printer 2 as an image forming apparatus according to the embodiment will be described in detail. FIG. 2 is a diagram showing a configuration example of the respective image forming stations SY, SM, SC, and SK in the printer 2. As shown in FIG. 2, the respective image forming stations SY, SM, SC, and SK each include an exposure device 100, a developing device 110, a photosensitive drum 122, a charger 126, a primary transfer roller 128, a photosensitive cleaner 130, and a discharger 132, etc. In the present embodiment, it is assumed that the respective image forming stations SY, SM, SC, and SK each have a configuration as shown in FIG. 2.

[0026] The photosensitive drum 122 is an image carrier having a photosensitive layer 124 on its surface. The photosensitive drum 122 rotates in a direction (the direction indicated by arrow b in FIG. 2) in accordance with the movement of the intermediate transfer belt 21 in the moving direction a. Around the photosensitive drum 122, a charger 126, an exposure device 100, a developing device 110, a primary transfer roller 128, the intermediate transfer belt 21, a photosensitive cleaner 130, and a discharger 132 are disposed.

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

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

[0029] The developing device 110 develops the electrostatic latent image formed on the surface of the photoreceptor drum 122 with a developer. The developing device 110 supplies the developer D to the surface of the photoreceptor drum 122 exposed by the exposure device 100. The developing devices 110 of each image forming station develop an image with the corresponding color. For example, the developing device 110 of the image forming station SY develops the electrostatic latent image on the photoreceptor drum 122 with yellow toner. The developing device 110 of the image forming station SM develops the electrostatic latent image on the photoreceptor drum 122 with magenta toner. The developing device 110 of the image forming station SC develops the electrostatic latent image on the photoreceptor drum 122 with cyan toner. The developing device 110 of the image forming station SK develops the electrostatic latent image on the photoreceptor drum 122 with black toner.

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

[0031] The toner density sensor 120 is disposed inside the developer container 112. The toner density sensor 120 detects the toner density in the developer D contained in the developer container 112. The toner density is represented by, for example, the ratio of toner to carrier (toner / carrier) in the developer D in the developer container 112. The system controller 5 controls such that the toner density detected by the toner density sensor 120 becomes a predetermined value.

[0032] The developing roller 114 has, for example, a magnetic body (such as a magnet) in which positive and negative electrodes are alternately arranged along the circumference. The developing roller 114 rotates counterclockwise. The first mixer 116 and the second mixer 118 stir the developer D in the developer container 112. Also, the first mixer 116 and the second mixer 118 convey the developer D. The second mixer 118 disposed below the developing roller 114 supplies the developer D to the surface of the developing roller 114.

[0033] On the surface of the developing roller 114, the developer D adheres in a standing state according to the magnetic field distribution generated by the magnetic body of the developing roller 114. The developing roller 114 rotates while carrying the developer D. The layer of the developer D attached to the developing roller 114 is limited to a predetermined thickness by a blade provided so that the distance from the surface of the developing roller 114 becomes a predetermined width. The developer D carried by the developing roller 114 moves to a position (developing position) facing the surface of the photosensitive drum 122.

[0034] The developing roller 114 that carries the developer D has a developing bias applied thereto. 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 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 photosensitive 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 photosensitive drum 122 on which the electrostatic latent image is formed. The toner contained in the developer D carried by the developing roller 114 develops the electrostatic latent image on the photosensitive drum 122 when it approaches the surface of the photosensitive drum 122. Thereby, a toner image obtained by developing the electrostatic latent image with toner is formed on the photosensitive 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 photosensitive drum 122 is referred to as the contrast voltage. The contrast voltage is related to the concentration of the toner that moves from the developing roller 114 to the electrostatic latent image on the photosensitive drum 122. That is, the concentration of the toner image formed on the photosensitive drum 122 is adjusted by controlling the contrast voltage. The contrast voltage is adjusted by controlling the developing bias. Also, the contrast voltage may be adjusted by controlling the potential of the electrostatic latent image.

[0036] The image (toner image) developed with toner on the surface of the photosensitive drum 122 moves to a position corresponding to the primary transfer roller 128 by the rotation of the photosensitive drum 122. The primary transfer roller 128 faces the photosensitive drum 122 with the intermediate transfer belt 21 interposed therebetween. The primary transfer roller 128 abuts on the surface of the photosensitive drum 122 with the intermediate transfer belt 21 interposed therebetween. The primary transfer roller 128 transfers the toner image on the surface of the photosensitive drum 122 to the intermediate transfer belt 21 (primary transfer).

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

[0038] The static eliminator 132 is disposed downstream in the circumferential direction of the photoreceptor drum 122 from the position of the photoreceptor cleaner 130. The static eliminator 132 irradiates light onto the surface of the photoreceptor drum 122. Thereby, the static eliminator 132 removes the charges remaining in the photoreceptor layer 124 on the surface of the photoreceptor drum 122.

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

[0040] The processor 101 realizes various processes by executing programs. The processor 101 is, for example, a CPU. The processor 101 is connected to the ROM 102, the RAM 103, the storage device 104, the communication interface (I / F) 105, and the like. Further, the processor 101 is connected to each part within the printer 2, the operation panel 3, and the scanner 4 via interfaces.

[0041] The ROM 102 is a non-rewritable non-volatile memory. The ROM 102 operates as a program memory for storing programs. The RAM 103 operates as a working memory or a buffer memory. The processor 101 executes various processes by using the RAM 103 to execute the programs stored in the ROM 102 or the storage device 104.

[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 setting information. The storage device 104 also stores image data and the like.

[0043] The communication I / F 105 is an interface for performing data communication with an external device. For example, the communication I / F 105 communicates with user terminals such as a PC and a mobile terminal via a network. The communication I / F 105 may be configured to input a print request (print job) of an image from a user terminal such as a PC.

[0044] As shown in FIG. 3, in addition to each configuration shown in FIGS. 1 and 2, the printer 2 has a power supply 140. The power supply 140 supplies voltages to the developing device 110, the charger 126, the primary transfer roller 128, and the secondary transfer roller 22, respectively. As shown in FIG. 3, the power supply 140 has a high voltage power supply 141, a developing bias transformer 142, a charging bias transformer 143, a primary transfer bias transformer 144, and a secondary transfer bias transformer 145. However, the developing bias transformer 142, the charging bias transformer 143, and the primary transfer bias transformer 144 are provided for each of the image forming stations SY, SM, SC, and SK.

[0045] The high voltage power supply 141 supplies high voltages to the various transformers 142, 143, 144, and 145. The high voltage is, for example, a voltage from several hundred volts to several kV. The high voltage power supply 141 generates a high voltage from an input voltage of, for example, several tens of volts.

[0046] The developing bias transformer 142 supplies a developing bias voltage to the developing device 110. The developing bias transformer 142 converts the high voltage generated by the high voltage power supply 141 into a developing bias voltage having 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 device 110.

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

[0048] The primary transfer bias transformer 144 supplies a 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 having 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 having a voltage value set by the system controller 5. The secondary transfer bias transformer 145 supplies the secondary transfer bias voltage having 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 as an image forming apparatus according to the embodiment will be described. The digital multi-function device 1 obtains an image to be formed on a recording medium M and executes an image forming process of printing the obtained image on the recording medium M by the printer 2. For example, when copying is instructed on the operation panel 3, the processor 101 of the system controller 5 executes a process of printing the image of the document read by the scanner 4 on the recording medium M by the printer 2.

[0051] When the processor 101 of the system controller 5 executes the image forming process, it takes in the recording medium M stored in the storage section by the medium supply mechanism 13. The processor 101 causes the transport mechanism 15 to transport the recording medium M supplied from the medium supply mechanism 13 in the printer 2 to before the registration roller 56.

[0052] Also, the processor 101 of the system controller 5 generates images formed by the respective image forming stations SY, SM, SC, SK based on the image (printing image) to be printed on the recording medium M. For example, the processor 101 generates images of the respective colors (yellow, magenta, cyan, black) formed by the respective image forming stations SY, SM, SC, SK from the printing image. When the processor 101 generates images of the respective colors from the printing image, it causes the generated images of the respective colors to be formed on the respective image forming stations.

[0053] In each of the image forming stations SY, SM, SC, SK, the charger 126 charges the photosensitive layer 124 of the photosensitive drum 122 by receiving a charging bias voltage from the charging bias transformer 143. The exposure device 100 irradiates light that forms an electrostatic latent image corresponding to the images of the respective colors on the photosensitive drums 122 of the respective image forming stations SY, SM, SC, SK. In each of the image forming stations SY, SM, SC, SK, an electrostatic latent image is formed on the photosensitive layer 124 of the photosensitive drum 122 by the light irradiated from the exposure device 100.

[0054] Each of the image forming stations SY, SM, SC, and SK develops the electrostatic latent image on the photosensitive drum 122 with the toner of the color accommodated in the developing device 110. In each of the image forming stations SY, SM, SC, and SK, the developing roller 114 rotates while carrying the developer containing the toner of each color supplied from the developer accommodating portion 112. The developing roller 114 carrying the developer is applied with the developing bias voltage from the developing bias transformer 142. The developing device 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 photosensitive drum 122.

[0055] In each of the image forming stations SY, SM, SC, and SK, the photosensitive drum 122 moves the image (toner image) developed by the developing device 110 to the position (primary transfer position) facing the primary transfer roller 128. At the primary transfer position, the photosensitive drum 122 faces the primary transfer roller 128 with the intermediate transfer belt 21 interposed therebetween. The primary transfer roller 128 is applied with the primary transfer bias voltage from the primary transfer bias transformer 144. The toner image on the photosensitive 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 of the image forming stations SY, SM, SC, and SK transfers the toner images of each color onto the intermediate transfer belt 21 in an overlapping manner. Thereby, a color image in which the toner images of each color are overlapped is transferred onto the intermediate transfer belt 21.

[0056] The intermediate transfer belt 21 moves the transferred toner image to a position (secondary transfer position) facing the secondary transfer roller 22. The registration roller 56 feeds the recording medium M to the secondary transfer position in accordance with the position and timing of the image transferred onto the intermediate transfer belt 21. As a result, the secondary transfer roller 22 and the support roller 23 convey the overlapping intermediate transfer belt 21 and the recording medium M in a state of sandwiching them 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 onto 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 that has passed through the secondary transfer position is conveyed to the fixing device 26. The fixing device 26 fixes the toner image transferred from the intermediate transfer belt 21 to the recording medium M at the secondary transfer position. The fixing device 26 applies heat and pressure to the recording medium M onto which the toner image has been transferred to fix the toner image to the recording medium M. The recording medium M that has passed through the fixing device 26 is discharged from the paper discharge unit with the toner image fixed thereon.

[0058] Next, the image density adjustment in the printer 2 as the image forming apparatus according to the embodiment will be described. The printer 2 of the digital multi-functional device 1 adjusts the density of the image formed on the recording medium M by the image forming process as described above. The density of the image formed on the recording medium M varies depending on the amount (density) of toner supplied from the developing roller 114 to the electrostatic latent image when developing the electrostatic latent image on the photosensitive drum 122.

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

[0060] After executing the image density adjustment, the processor 101 of the system controller 5 in the digital multifunction peripheral 1 according to this embodiment detects the difference in contrast potential for each color. When there is a contrast potential whose difference from other contrast potentials exceeds a reference value, the processor 101 issues a warning.

[0061] FIG. 4 illustrates an operation example of image density adjustment in the printer 2 as an image forming apparatus according to the embodiment. The processor 101 of the system controller 5 executes image density adjustment to equalize the toner density of the images of each color formed by each image forming station SY, SM, SC, SK. As the image density adjustment, the processor 101 transfers the toner images formed by each image forming station SY, SM, SC, SK onto the intermediate transfer belt 21 (ACT11).

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

[0063] After transferring the toner images of each color onto the intermediate transfer belt 21, the processor 101 of the system controller 5 detects the toner density of each color with the toner adhesion amount sensor 24 (ACT12). The toner adhesion amount sensor 24 detects the density (toner density) of the toner images of each color transferred onto the intermediate transfer belt 21. The toner adhesion amount sensor 24 supplies a detection result indicating the toner density of each color to the processor 101.

[0064] The processor 101 determines whether to perform density adjustment for each image forming station based on the toner density of each color detected by the toner adhesion amount sensor 24 (ACT13). For example, the processor 101 determines whether the toner density of each color detected by the toner adhesion amount sensor 24 is a predetermined density (within a predetermined density range). The processor 101 determines to perform density adjustment for the image forming station of the color for which it is determined that the toner density is not the predetermined density.

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

[0066] The processor 101 changes (adjusts) the contrast potential so that the toner density of the toner image formed by the image forming station becomes the predetermined density as the density adjustment. For example, the processor 101 changes the contrast potential by controlling the developing bias voltage applied by the developing bias transformer 142 to the developing roller 114. Also, the system controller 5 may change the contrast potential by controlling the charging bias voltage applied by the charging bias transformer 143 to the charger 126. Further, the system controller 5 may change the contrast potential by controlling the light irradiated by the exposure unit 100 to the photosensitive drum 122.

[0067] When performing image density adjustment, the processor 101 stores the adjustment results of the contrast potential at each image forming station SY, SM, SC, SK in the storage device 104 (ACT15). For example, when the processor 101 adjusts the contrast potential at the image forming station SY, it stores the contrast potential of yellow (the contrast potential corresponding to the image forming station SY) as the adjustment result in the storage device 104. Similarly, when the processor 101 adjusts the contrast potential at the image forming station SM (SC, SK), it stores the adjustment results of the contrast potential of magenta (cyan, black) in the storage device 104.

[0068] Also, when the processor 101 adjusts the contrast potential, it calculates the difference in the contrast potential at each image forming station SY, SM, SC, 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] After calculating the difference in the contrast potential of each color, the processor 101 determines whether there is a contrast potential whose difference from the contrast potential of other colors exceeds a reference value (ACT17). The reference value for comparison with the difference in the contrast potential is a threshold value for determining that there may be a problem such as a failure or an abnormality in the digital multi-function device 1. The image forming station including a device with a failure or an abnormality may have a larger difference in the contrast potential compared to the contrast potential of other image forming stations.

[0070] For example, in a developing device with an abnormality in the toner density sensor, the toner density in the developer cannot be maintained at a predetermined value. In an image forming station where the toner density in the developer is not maintained at a predetermined value, the contrast potential is greatly changed to adjust the toner density to a predetermined density. The contrast potential of an image forming station including a developing device with an abnormality in the toner density sensor may be significantly different from the contrast potential of other image forming stations. Also, the contrast potential of an image forming station where a charger, an exposure device, a developing roller, etc. are not operating normally may be significantly different from other contrast potentials.

[0071] When there is no contrast potential whose difference from other contrast potentials exceeds the reference value (ACT17, NO), the processor 101 ends the image density adjustment. That is, when the difference in the contrast potential for each color is within the reference value, the processor 101 ends the series of operations for image density adjustment.

[0072] When there is a contrast potential whose difference exceeds the reference value (ACT17, YES), the processor 101 notifies a warning that the difference in the contrast potential exceeds the reference value (ACT18). The warning to be notified may be anything that prompts verification or maintenance of the malfunction suggested by the fact that the difference in the contrast potential exceeds the reference value. For example, the warning may be a guide for inspection or maintenance, or a message notifying that there may be a failure or abnormality in the digital multi-function machine. Also, the warning may include a message indicating the image forming station or color whose difference from other contrast potentials exceeds the reference value.

[0073] In addition, even when the difference in contrast potential exceeds the reference value, if the toner density of each color is adjusted to a normal value, the digital multi-function peripheral 1 can form an image with a normal density. Therefore, even when the processor 101 notifies a warning indicating that the difference in contrast potential has exceeded the reference value, it may continue the operation of the image forming process. As a result, the digital multi-function peripheral can notify that the difference in contrast potential has become large while maintaining the image forming process at a normal density.

[0074] Further, the processor 101 may notify a service technician or an administrator without notifying the user that the difference in contrast potential exceeds the reference value. As a result, the digital multi-function peripheral 1 can prompt maintenance for abnormalities suggested by the difference in contrast potential to the service technician while providing a normal image forming process to the user.

[0075] For example, the processor 101 notifies, via the communication I / F 105, a terminal device (external device) held by the service technician that the difference in contrast potential has exceeded the reference value. Also, the processor 101 may notify, via the communication I / F 105, a system that manages the operating state of the digital multi-function peripheral that the difference in contrast potential has exceeded the reference value. Further, the processor 101 may display on the operation panel 3 that the difference in contrast potential has exceeded the reference value when the service technician or the administrator logs in.

[0076] Note that the processor 101 may execute the processes of ACT11-15 as image density adjustment and execute the processes of ACT16-18 in response to a request from a service technician or the like. As a result, the digital multi-function peripheral 1 can notify the possibility of a failure or an abnormality based on the difference between the contrast potentials of each color in response to a request from the service technician.

[0077] As described above, the image forming apparatus according to the embodiment includes a plurality of photosensitive drums, a plurality of developing rollers, and a system controller. Each photosensitive drum carries an electrostatic latent image formed by light from an exposure device. Each developing roller is provided facing each photosensitive drum. Each developing roller supplies toner to the electrostatic latent image by a contrast potential that is the potential difference from the electrostatic latent image carried by the facing photosensitive drum. The system controller adjusts the contrast potential corresponding to each photosensitive drum so that the density of the toner image developed on each photosensitive drum becomes uniform. The system controller notifies a warning when the difference in the contrast potential corresponding to each photosensitive drum exceeds a reference value.

[0078] With the above-described configuration, when the image forming apparatus according to the embodiment performs image density adjustment, it can notify that there is a difference in the contrast potential that may cause a failure or an abnormality. As a result, according to the image forming apparatus according to the embodiment, a service technician can predict a part that may cause a failure or an abnormality from the difference in the contrast potential. In addition, the image forming apparatus can promote prompt maintenance of a part where a failure or an abnormality may have occurred by notifying that the difference in the contrast potential has exceeded the reference value.

[0079] Although some embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and its equivalent scope.

Description of Reference Numerals

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

Claims

1. A plurality of photoreceptors, An exposure device that irradiates the surfaces of the plurality of photoreceptors with light corresponding to the images formed on the plurality of photoreceptors, A developing device that supplies toner to the surfaces of the plurality of photoreceptors on which electrostatic latent images are formed by the light irradiated by the exposure device, A processor that adjusts the contrast potential for each photoreceptor to supply toner to the electrostatic latent images formed on the surfaces of the plurality of photoreceptors from the developing device, and notifies a warning when there is a contrast potential whose difference from other contrast potentials exceeds a reference value, An image forming apparatus having the above.

2. The developing device has a plurality of developing rollers facing each photoreceptor, The processor adjusts the contrast potential for each photoreceptor by adjusting the voltage applied to the plurality of developing rollers, The image forming apparatus according to Claim 1.

3. Having a sensor that detects the toner density on a medium onto which a toner image formed on the surfaces of the plurality of photoreceptors with the toner supplied from the developing device is transferred, The processor adjusts the contrast potential corresponding to each photoreceptor so that the toner density detected by the sensor becomes a desired density, and calculates the difference between the respective contrast potentials after the adjustment of the contrast potentials corresponding to all the photoreceptors is completed, The image forming apparatus according to any one of Claims 1 and 2.

4. Having an interface for communicating with an external device, When there is a contrast potential whose difference from other contrast potentials exceeds a reference value, the processor notifies a warning to the external device via the interface, The image forming apparatus according to any one of Claims 1 to 3.

5. Having a memory that stores the adjustment results of the contrast potential for each photoreceptor, When there is a contrast potential whose difference from other contrast potentials exceeds a reference value, the processor displays a warning indicating that there is a contrast potential whose difference from other contrast potentials exceeds a reference value on a display device, The image forming apparatus according to Claim 4.

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