Image forming apparatus

Abstract

To provide an image forming apparatus that can perform printing even when trouble occurs in an electrification voltage AC component generation circuit.SOLUTION: An image forming apparatus comprises: an image forming unit including an electrifying unit that electrifies a photoreceptor, an electrification voltage application unit that applies, to the electrifying unit, a first electrification voltage in which an AC component is superimposed on a DC component or a second electrification voltage including only the DC component in a switchable manner, an exposure unit that forms an electrostatic latent image on the photoreceptor, a developing unit that supplies toner to the photoreceptor to form a toner image corresponding to the electrostatic latent image, a developing voltage application unit that applies at least a developing voltage including the DC component to the developing unit, a transfer unit that transfers the toner image to a recording medium, and a fixing unit that fixes the toner image to the recording medium; and a control unit that controls the image forming unit. The DC component in the first electrification voltage and the DC component in the developing voltage when the electrification voltage application unit applies the first electrification voltage to the electrifying unit, are respectively set to different values from the DC component in the second electrification voltage and the DC component in the developing voltage when the electrification voltage application unit applies the second electrification voltage to the electrifying unit.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] This disclosure relates to image forming apparatuses. [Background technology]

[0002] In a conventional image forming device equipped with a general high-voltage output AC component generating circuit that applies a high-voltage output in which an AC component is superimposed on a DC component to a contact charging section, if a malfunction such as an output defect occurs in the charging output AC component generating circuit, a service call becomes necessary and printing becomes impossible until the device is repaired.

[0003] In relation to such problems, an image forming apparatus has been disclosed that, even if the voltage to be applied to a charging member that charges an image carrier cannot be determined properly in a conventional image forming apparatus, detects the value of the current flowing from the charging member to the image carrier, calculates the value of the AC voltage to be applied to the charging member based on the detected current value, and if the calculated AC voltage value is abnormal, reapplies a voltage different from the reference voltage to the charging member, and if the recalculated AC voltage value is not abnormal, charges the image carrier using the charging member with the recalculated AC voltage value, thereby maintaining a good applied voltage and enabling stable image formation (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-133686 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if a malfunction occurs in the charging voltage AC component generation circuit to the extent that it cannot be corrected by adjusting the charging voltage of the AC voltage, such as a failure of the charging output AC component generation circuit, the user will be unable to print until repairs are completed by a service technician.

[0006] This disclosure has been made in consideration of the above circumstances, and its purpose is to provide an image forming apparatus that is capable of printing even if a malfunction occurs in the AC component generation circuit of the charging voltage. [Means for solving the problem]

[0007] The image forming apparatus according to this disclosure includes an image forming unit including a photosensitive member, a charging unit that charges the photosensitive member, a charging voltage applying unit that applies a predetermined charging voltage to the charging unit, an exposure unit that forms an electrostatic latent image on the photosensitive member, a developing unit that supplies toner to the photosensitive member to form a toner image corresponding to the electrostatic latent image, a developing voltage applying unit that applies a predetermined developing voltage to the developing unit, a transfer unit that transfers the toner image to a recording medium, and a fixing unit that heat-fixes the toner image to the recording medium, and a control unit that controls the image forming unit, and the charging voltage applying unit is characterized in that a first charging voltage in which an AC component is superimposed on a DC component or a second charging voltage which is a DC component only is switchably applied to the charging section, the developing voltage application section applies a developing voltage of at least a DC component to the developing section, and the DC component of the first charging voltage and the DC component of the developing voltage when the charging voltage application section applies the first charging voltage to the charging section are set to values ​​different from the DC component of the second charging voltage and the DC component of the developing voltage when the charging voltage application section applies the second charging voltage to the charging section. [Effects of the Invention]

[0008] According to this disclosure, it is possible to realize an image forming apparatus that is capable of printing even if a malfunction occurs in the AC component generation circuit of the charging voltage. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view showing the appearance of a digital multifunction peripheral according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view showing the internal configuration of the digital multifunction peripheral of FIG. [Figure 3] FIG. 2 is a block diagram showing a schematic configuration of the digital multifunction peripheral of FIG. 1. [Figure 4] 2 is an explanatory diagram showing a schematic configuration of a first visible image forming unit of the digital multifunction peripheral of FIG. 1. FIG. [Figure 5] 2 is an example of the circuit configuration of a charging voltage application unit and an AC circuit abnormality detection unit of the digital multifunction peripheral of FIG. 1. [Figure 6] 10 is a flowchart showing an example of a process for switching the charging method of the charging voltage application unit of the digital multifunction peripheral of FIG. [Figure 7] 2 is an example of an error message displayed on the display unit of the digital multifunction peripheral of FIG. 1. [Figure 8] 8A and 8B show examples of the charging voltage of the charging voltage application unit and the developing voltage of the developing voltage application unit of the digital multifunction peripheral of Fig. 1. Fig. 8A shows an example of the developing voltage and charging voltage when an AC component is superimposed, and Fig. 8B shows an example of the developing voltage and charging voltage when no AC component is superimposed. [Figure 9] FIG. 10 is a block diagram showing a schematic configuration of a digital multifunction peripheral according to a second embodiment of the present disclosure. [Figure 10] 10 is a flowchart showing an example of a process for switching the charging method of a charging voltage application unit of a digital multifunction peripheral according to a second embodiment of the present disclosure. [Figure 11] 11 is a flowchart showing an example of a process for switching the charging method of a charging voltage application unit of a digital multifunction peripheral according to a third embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] In this disclosure, an "image forming device" is a device that forms and outputs an image, such as a copier or multifunction device with a copying function, such as a printer that uses an electrophotographic method to form an image with toner, or an MFP (Multifunctional Peripheral) that also includes functions other than copying. In the first embodiment, the “developing section” of this disclosure is realized by the developing unit 61.

[0011] Further, preferred embodiments of this disclosure will be described.

[0012] The image forming apparatus according to this disclosure may further include an AC circuit abnormality detection unit that detects an abnormality in the AC component generation circuit of the charging voltage application unit, and the control unit may be configured to switch the charging voltage application unit from the first charging voltage to the second charging voltage and apply the same to the charging unit when the AC circuit abnormality detection unit detects an abnormality in the AC component generation circuit of the charging voltage application unit.

[0013] In this way, if the AC circuit abnormality detection unit detects an abnormality in the AC component generation circuit of the charging voltage application unit, the charging voltage application unit switches from the first charging voltage to the second charging voltage and applies it to the charging unit, thereby realizing an image forming device that is able to print even if a malfunction occurs in the AC component generation circuit of the charging voltage.

[0014] In the image forming apparatus according to this disclosure, the DC component of the second charging voltage may be set to a value obtained by adding the difference in surface potential of the photosensitive member that occurs with or without the superposition of an AC component to the DC component of the first charging voltage.

[0015] The "difference in the surface potential of the photosensitive body resulting from the presence or absence of the superimposition of the AC component" is the reduction in the surface potential of the photosensitive body (from the surface potential of the photosensitive body when the AC component is superimposed) that occurs when the charging section is applied with the second charging voltage when the AC component is not superimposed.

[0016] In this way, in a DC charging method in which an AC component is not superimposed, by taking into consideration that a voltage reduced from the applied voltage is charged onto the surface of the photosensitive member, the charging voltage application unit switches from the first charging voltage to the second charging voltage and applies it to the charging unit, an image forming device can be realized that is capable of printing even if a malfunction occurs in the AC component generation circuit of the charging voltage.

[0017] In the image forming apparatus according to this disclosure, when the sum of the difference in surface potential of the photosensitive member caused by the presence or absence of superimposition of an AC component and the DC component of the first charging voltage exceeds the maximum value of the DC component that the charging voltage application unit can output, the DC component of the second charging voltage may be set to the maximum value of the DC component, and the value obtained by subtracting the sum exceeding the maximum value of the DC component from the DC component of the developing voltage may be set as the value of the DC component of the developing voltage when the charging voltage application unit applies the second charging voltage to the charging unit.

[0018] In this way, even if the sum obtained by adding the difference in surface potential of the photosensitive member that occurs depending on whether or not an AC component is superimposed to the DC component of the first charging voltage exceeds the maximum value of the DC component that the charging voltage application unit can output, the DC component of the second charging voltage is set to the maximum value of the DC component, and the value obtained by subtracting the sum that exceeds the maximum value of the DC component from the DC component of the developing voltage is set as the value of the DC component of the developing voltage when the charging voltage application unit applies the second charging voltage to the charging unit, thereby realizing an image forming apparatus that is capable of printing even if a malfunction occurs in the AC component generation circuit of the charging voltage.

[0019] The image forming apparatus according to this disclosure may further include an image quality adjustment unit that adjusts image quality using an image density sensor that detects the image density of the toner image, and the control unit may be configured to switch from the first charging voltage to the second charging voltage and apply it to the charging unit if the image density sensor detects the image density of the toner image during the image quality adjustment and confirms that image quality has deteriorated, and if the image quality adjustment does not improve the deterioration.

[0020] In this way, if the image density sensor detects the image density of the toner image during image quality adjustment and confirms that the image quality has deteriorated, and if the deterioration in image quality does not improve even after image quality adjustment, the charging voltage application unit switches from the first charging voltage to the second charging voltage and applies it to the charging unit, thereby realizing an image forming device that is capable of printing even if a malfunction occurs in the AC component generation circuit of the charging voltage.

[0021] In the image forming apparatus according to this disclosure, the image forming unit has a function of color printing for forming a color image using toner images of all colors (black, cyan, magenta, and yellow) and a function of monochrome printing for forming a monochrome image using the black toner image, and the control unit, when the AC circuit abnormality detection unit detects an abnormality in the AC component generation circuit of the charging voltage application unit, if the abnormality in the AC component generation circuit of the charging voltage application unit relates to the black toner image, may be configured to cause the charging voltage application unit related to the black toner image to switch from the first charging voltage to the second charging voltage and apply it to the charging unit during monochrome printing, and to cause the charging voltage application unit related to the all-color toner images to switch from the first charging voltage to the second charging voltage and apply it to the charging unit during color printing; on the other hand, when the abnormality in the AC component generation circuit of the charging voltage application unit relates to the cyan, magenta, or yellow toner images, to cause the charging voltage application unit related to the all-color toner images to switch from the first charging voltage to the second charging voltage and apply it to the charging unit.

[0022] In this way, if the abnormality in the AC component generation circuit of the charging voltage application unit is related to the black toner image, during monochrome printing, the charging voltage application unit related to the black toner image will switch from the first charging voltage to the second charging voltage and apply it to the charging unit, and during color printing, the charging voltage application unit related to the toner images of all colors will switch from the first charging voltage to the second charging voltage and apply it to the charging unit, so that monochrome / color printing can be continued, albeit with lower image quality. On the other hand, if the abnormality in the AC component generation circuit of the charging voltage application unit relates to the cyan, magenta, or yellow toner images, the charging voltage application unit for all color toner images switches from the first charging voltage to the second charging voltage and applies it to the charging unit, so that color printing can continue although at a lower image quality, and monochrome printing can be performed at the same high image quality as before. Therefore, it is possible to realize an image forming apparatus that is capable of printing even if a malfunction occurs in the AC component generating circuit of the charging voltage.

[0023] This disclosure will be described in further detail below with reference to the accompanying drawings. Note that the following description is illustrative in all respects and should not be construed as limiting this disclosure.

[0024] [Embodiment 1] <Digital MFP 1 Configuration> Hereinafter, an overview of a digital multifunction peripheral 1 as an example of an image forming apparatus according to a first embodiment of the present disclosure will be described with reference to FIGS.

[0025] FIG. 1 is a perspective view showing the appearance of a digital multifunction peripheral 1 according to a first embodiment of the present disclosure. FIG. 2 is a cross-sectional view showing the internal configuration of the digital multifunction peripheral 1 of FIG.

[0026] The digital multifunction peripheral 1 has a copying function, a scanning function, and a facsimile function, and is a device that digitally processes image data read from an original and outputs the processed image data.

[0027] The digital multifunction device 1 has a copy (duplication) function, a print function, and a fax function as printing modes, and the control unit 10 (Figure 3) selects a printing function in response to an operation input from the operation unit 162 (Figure 3) or a print job received from an external device such as a personal computer.

[0028] <Internal configuration of Digital MFP 1> In FIG. 2, the digital multifunction printer 1 is a color multifunction printer and includes an optical system unit 50, first to fourth visible image forming units 51 to 54, an intermediate transfer belt 55, a secondary transfer unit 56, a fixing section 2, an internal paper feed unit 57, a manual paper feed unit 58, and a paper output tray 75.

[0029] The digital multifunction peripheral 1 forms a toner image using the first to fourth visible image forming units 51 to 54, the intermediate transfer belt 55, and the secondary transfer unit 56.

[0030] The optical system unit 50 is arranged so that beams from four laser light sources 64 reach four sets of photosensitive drums 59, 65, 66, and 67.

[0031] The first visible image forming unit 51 includes a photosensitive drum 59, a charging roller 60, an optical system unit 50, a developing unit 61a, and a primary transfer unit 62a.

[0032] A charging roller 60, a developing unit 61a, and a cleaning unit 63 are arranged around a photosensitive drum 59 which serves as an image carrier.

[0033] These units form a toner image on the photosensitive drum 59 and transfer the toner image to the intermediate transfer belt 55 .

[0034] The photosensitive drum 59 is an image carrier on whose surface a toner image is formed, is supported so as to be rotatable about its axis, and includes a cylindrical, columnar, or thin film sheet-like (preferably cylindrical) conductive substrate (not shown), and a photosensitive layer formed on the surface of the conductive substrate.

[0035] The photosensitive drum 59 rotates counterclockwise toward the paper surface of FIG. 2 at a peripheral speed of, for example, 163 mm / s by a photosensitive drum drive gear (not shown) attached to the photosensitive drum 59 which is engaged with the motor gear.

[0036] The primary transfer unit 62a is disposed so as to be in pressure contact with the photosensitive drum 59 via the intermediate transfer belt 55.

[0037] The second to fourth visible image forming units 52 to 54 have the same configuration as the first visible image forming unit 51, and therefore, a description thereof will be omitted.

[0038] The developing units 61a, 61b, 61c, and 61d of the units 51 to 54 contain toner of each color, black (K), cyan (C), magenta (M), and yellow (Y), respectively.

[0039] Hereinafter, the developing units 61a, 61b, 61c, and 61d of the respective colors may be referred to as the developing unit 61 as a representative. Furthermore, the primary transfer units 62a, 62b, 62c, and 62d of the respective colors may be collectively referred to as the primary transfer unit 62.

[0040] The intermediate transfer belt 55 has the toner images of each color transferred thereon, and the color toner images of each color are superimposed on the surface thereof. The intermediate transfer belt 55 is driven to rotate by tension rollers 68 and 69 . The secondary transfer unit 56 is disposed in contact with the tension roller 68 side of the intermediate transfer belt 55 .

[0041] The secondary transfer unit 56 applies a high voltage of the opposite polarity to the toner charging polarity to the transfer area using the transfer roller 621a or the like, thereby transferring the color toner image formed on the intermediate transfer belt 55 onto the recording medium 31 fed from the internal paper feed unit 57 and the manual paper feed unit 58 by feed rollers 73 and 74, respectively.

[0042] Thereafter, the recording medium 31 onto which the color toner image has been transferred is transported to the position of the fixing unit 2 .

[0043] Further, a waste toner box 70 is disposed on the tension roller 69 side in contact with the intermediate transfer belt 55, and collects toner remaining on the surface of the intermediate transfer belt 55 after the secondary transfer.

[0044] The fixing unit 2 is disposed downstream of the secondary transfer unit 56. The fixing unit 2 is composed of a fixing belt 71 and a pressure roller 72 . The pressure roller 72 is pressed against the fixing belt 71 at a predetermined pressure by a pressure mechanism (not shown). Further, downstream of the fixing unit 2, a paper discharge tray 75 is provided.

[0045] Next, the schematic configuration of the digital multifunction peripheral 1 will be described with reference to FIG. FIG. 3 is a block diagram showing a schematic configuration of the digital multifunction peripheral 1 of FIG.

[0046] As shown in FIG. 3, the digital multifunction peripheral 1 includes a control unit 10, an image data acquisition unit 11, an image forming unit 12, a memory unit 13, an image processing unit 14, a communication unit 15, an operation panel 16, a voltage application unit 17, and a power supply 18.

[0047] Each component of the digital multifunction peripheral 1 will be described below.

[0048] The control unit 10 controls the digital multifunction peripheral 1 in an integrated manner, and is composed of a CPU, RAM, ROM, various interface circuits, and the like.

[0049] The control unit 10 monitors and controls all loads such as the detection of each sensor, motor, clutch, operation panel 16, etc., in order to control the overall operation of the digital multifunction peripheral 1.

[0050] The image data acquisition unit 11 detects and reads an original placed on a platen or an original transported from an original tray, and generates image data. It also acquires image data generated by an external information processing device (not shown) or a facsimile machine (not shown).

[0051] The image forming unit 12 is a part that prints out the image data generated by the image processing unit 14 onto paper.

[0052] The storage unit 13 is an element or storage medium that stores information, control programs, etc., necessary to realize various functions of the digital multifunction peripheral 1. For example, a semiconductor element such as a RAM or a ROM, a hard disk, a flash storage unit, an SSD, or other storage medium may be used.

[0053] The program and the data may be stored in different devices, such as by configuring the area for storing data as a hard disk drive and the area for storing the program as a flash memory unit.

[0054] The image processing unit 14 converts the image of the document read by the image data acquisition unit 11 into an appropriate electrical signal to generate image data.

[0055] The communication unit 15 is a part that communicates with computers, mobile information terminals, external information processing devices, facsimile machines, etc. via a network, etc., and transmits and receives various information such as e-mails and faxes to and from these external communication devices.

[0056] The operation panel 16 is a unit equipped with a liquid crystal display (LCD), and includes a display unit 161 and an operation unit 162.

[0057] The display unit 161 is a part that displays various information to the user. The display unit 161 is a display device such as a monitor or line display, which is configured by, for example, a CRT display, a liquid crystal display, or an EL display, and which displays electronic data such as the processing status of the operating system and application software. The control unit 10 displays the operation and status of the digital multifunction peripheral 1 through the display unit 161.

[0058] The operation unit 162 includes, for example, a touch panel, and is also a part that receives commands such as printing from the user.

[0059] The voltage application unit 17 is a part that applies voltage, and includes a charging voltage application unit 171 , a development voltage application unit 172 , a transfer voltage application unit 173 , an AC circuit abnormality detection unit 174 , and a charging method switching unit 175 .

[0060] The charging voltage application unit 171 applies a predetermined charging voltage Vo to the charging roller 60. The developing voltage application section 172 applies a predetermined developing voltage Vb to the developing roller 611a. The transfer voltage application unit 173 applies a predetermined transfer voltage Vt to the transfer roller 621a. The AC circuit abnormality detection unit 174 is a part that detects an abnormality in the AC circuit of the voltage application unit 17. The charging method switching unit 175 is a part that switches the voltage application method of the charging voltage application unit 171 .

[0061] The power supply 18 supplies power to each part of the digital multifunction peripheral 1, and may be, for example, an AT power supply, an ATX power supply, or an SFX power supply.

[0062] The power supply 18 includes a charging power supply 181 , a developing power supply 182 , and a transfer power supply 183 .

[0063] <Operation of the first visible image forming unit 51 of the digital multifunction peripheral 1> Next, the operation of the first visible image forming unit 51 of the digital multifunction peripheral 1 will be described with reference to FIG.

[0064] FIG. 4 is an explanatory diagram showing a schematic configuration of the first visible image forming unit 51 of the digital multifunction peripheral 1 of FIG.

[0065] In the following description, the first visible image forming unit 51 will be taken as an example, but the same applies to the other second to fourth visible image forming units 52 to .

[0066] In FIG. 4, the photosensitive drum 59 rotates in a rotation direction R1 (counterclockwise on the paper). The charging roller 60 rotates in a rotation direction R2 (clockwise on the paper surface) in response to the rotation of the photosensitive drum 59. In the first embodiment, the charging roller 60 is driven by the photosensitive drum 59, but it does not have to be driven.

[0067] During image formation, the surface of the photosensitive drum 59 is uniformly charged by the charging roller 60 . In the first embodiment, a charging roller system is employed to charge the surface of the photosensitive drum 59 uniformly and with as little ozone generation as possible.

[0068] As shown in FIG. 4, the charging roller 60 is pressed against the surface of the photosensitive drum 59 with a predetermined pressure suitable for charging by a biasing force (not shown) such as a spring, and rotates following the rotation of the photosensitive drum 59.

[0069] The charging voltage application unit 171 applies a predetermined charging voltage Vo from a charging power source 181 (high-voltage power supply circuit) to the core metal 601 of the charging roller 60, thereby charging the surface of the photosensitive drum 59 with a predetermined voltage (for example, -0V to -800V).

[0070] The optical system unit 50 exposes the surface of the charged photosensitive drum 59 with a beam from the laser light source 64, thereby reducing the surface potential VL of the photosensitive drum 59 after exposure to, for example, -100 V or less, and forming an electrostatic latent image.

[0071] Although this disclosure can be applied to both the normal development method and the reversal development method, the first embodiment will be described using the reversal development method.

[0072] The laser light from the optical system unit 50 is irradiated onto the photosensitive drum 59 through a polygon mirror and various lenses (not shown).

[0073] The laser light source 64 is controlled based on image information, and an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 59 .

[0074] The developing unit 61a develops the electrostatic latent image on the photosensitive drum 59 to form a toner image. The electrostatic latent image formed on the photosensitive drum 59 is visualized by the developing unit 61a with a developer 612a containing toner and carrier, thereby forming a toner image.

[0075] As shown in FIG. 4, the developing unit 61a is a developing unit arranged opposite the photosensitive drum 59, and the developing roller 611a as a developer carrier is rotatably mounted on a rotation axis parallel to the rotation axis of the photosensitive drum 59.

[0076] The developing unit 61a is a hollow container-like member made of, for example, a hard synthetic resin, etc. As described above, the developing unit 61a contains a two-component developer containing toner and carrier, but it may also contain a one-component developer containing only toner.

[0077] The developing roller 611a is a magnetic roller formed by arranging magnet members with different polarities substantially alternately in the circumferential direction. The developing roller 611a attracts the developer 612a contained in the developing unit 61a by its magnetic force. The attracted developer 612a is regulated to a predetermined thickness by a developer regulating member (not shown) and is transported to the developing nip portion where the developing roller 611a and the photosensitive drum 59 are close to each other.

[0078] The developing voltage application unit 172 applies a predetermined developing voltage Vb from a developing power source 182 (high voltage power supply circuit) to the core metal 613a of the developing roller 611a, thereby charging the core metal 613a with the predetermined voltage.

[0079] The developing voltage Vb is set to a value lower than the surface potential Vd (-600V) of the non-exposed portion of the photosensitive drum 59, and higher than the surface potential VL (-100V) of the exposed portion.

[0080] As a result, toner charged to the same polarity as the charge polarity of the photosensitive drum 59 (negative polarity in the first embodiment) is attracted to the surface potential VL of the exposed portion of the photosensitive drum 59 to form a toner image (reverse development).

[0081] On the other hand, the surface potential Vd of the non-exposed portion of the photosensitive drum 59 is lower than the developing voltage Vb of the developing roller 611a, so that the toner is prevented from adhering to the non-exposed portion.

[0082] A voltage of the opposite polarity to that of the toner is applied to the core 622a of the transfer roller 621a of the primary transfer unit 62a from the transfer power supply 183 (high-voltage power supply circuit), and the toner image developed on the photosensitive drum 59 is transferred onto the intermediate transfer belt 55 in the transfer area where the primary transfer unit 62a and the photosensitive drum 59 are close to each other.

[0083] In the first embodiment, the primary transfer unit 62a is configured using the transfer roller 621a, but it may also be configured using a belt or a wire.

[0084] The other second to fourth visible image forming units 52 to 54 operate in the same manner, and transfer toner images onto the intermediate transfer belt 55 in sequence.

[0085] The toner image on the intermediate transfer belt 55 is transported to a secondary transfer unit 56 . As shown in FIG. 2, the recording medium 31 is supplied from a feed roller 73 of the internal paper feed unit 57 or a feed roller 74 of the manual paper feed unit 58 via a transport path RT1 or RT2, respectively. Then, a voltage of the opposite polarity to that of the toner is applied by the secondary transfer unit 56 , and the toner image is transferred onto the recording medium 31 .

[0086] The recording medium 31 carrying the toner image is transported to the fixing section 2, where it is sufficiently heated by the fixing belt 71 and pressure roller 72, causing the unfixed toner image to melt and adhere to the recording medium 31, and the recording medium 31 is then discharged via the conveying path RT4 to the discharge rollers ER onto the discharge tray 75.

[0087] In the case of double-sided printing, after the recording medium 31 has passed through the fixing unit 2 and image formation on the front side has been completed, the recording medium 31 is turned over via the transport path RT3 and image formation on the back side is carried out.

[0088] After the transfer, residual toner that has not been transferred onto the intermediate transfer belt 55 adheres to the photosensitive drum 59 . This residual toner is scraped off by a cleaning blade 63a attached to the cleaning unit 63 and collected inside the cleaning unit 63 as waste toner.

[0089] The charge removal unit 76 removes the charge from the surface of the photosensitive drum 59 . The position of the charge removing unit 76 may be anywhere after transfer and before charging.

[0090] The cleaning roller 77 is disposed in a position facing the charging roller 60 and cleans the surface of the charging roller 60 .

[0091] FIG. 5 shows an example of the circuit configuration of the charging voltage application unit 171 and the AC circuit abnormality detection unit 174 of the digital multifunction peripheral 1 of FIG.

[0092] As shown in FIG. 5, the charging voltage application section 171 of this disclosure uses an AC charging method. In the AC charging method, a voltage in which an AC component is superimposed on a DC component (DC voltage+AC voltage) is applied to the charging section, thereby keeping the surface potential VL of the photosensitive drum 59 constant.

[0093] For example, when the surface potential VL of the photosensitive drum 59 is set to -500 V, it is known that the DC component voltage applied to the charging section is charged to the surface of the photosensitive drum 59 at almost the same voltage, so it is necessary to apply a DC component of -500 V. Generally, it is necessary to apply an AC voltage of approximately 1500 Vpp.

[0094] It is known that the AC charging method can make the surface potential VL of the photosensitive drum 59 more uniform than the DC charging method in which only a DC voltage is applied to the charging section.

[0095] In the circuit of FIG. 5, a voltage of a direct current component is output from a DC output circuit. The AC component voltage is output from the charging power supply 181 as a reference sine wave, a triangular wave, a Vpp control signal, and an AC transformer. Then, a charging voltage Vo is output, which is a voltage of an AC component superimposed on a voltage of a DC component.

[0096] Furthermore, the circuit of the charging voltage application unit 171 is connected to the circuit of the AC circuit abnormality detection unit 174, which detects the output state of the AC component.

[0097] <Switching Process of Charging Method of Charging Voltage Application Unit 171 of Digital Multifunction Peripheral 1 According to Embodiment 1 of the Present Disclosure> Next, a process for switching the charging method of the charging voltage application unit 171 of the digital multifunction peripheral 1 according to the first embodiment of the present disclosure will be described. FIG. 6 is a flowchart showing an example of a process for switching the charging method of the charging voltage application unit 171 of the digital multifunction peripheral 1 of FIG.

[0098] In step S1 of FIG. 6, the charging voltage application unit 171 charges the charging unit by an AC charging method in which an AC component voltage is superimposed on a DC component voltage (step S1).

[0099] Next, in step S2, the control unit 10 determines whether or not an abnormality in the AC circuit has been detected (step S2).

[0100] When AC circuit abnormality detection unit 174 detects a state in which no AC component is being output, it transmits an abnormality signal (for example, a High signal) to control unit 10.

[0101] If no abnormality in the AC circuit is detected (if the determination in step S2 is No), the control unit 10 returns the process to step S1.

[0102] On the other hand, if an abnormality in the AC circuit is detected (if the judgment in step S2 is Yes), in step S3, the control unit 10 causes the display unit 161 to display a message indicating that the AC circuit has failed and asking whether or not to switch to a low-quality printing mode (step S3).

[0103] FIG. 7 shows an example of an error message displayed on the display unit 161 of the digital multifunction peripheral 1 of FIG. In the example of FIG. 7, the message "ERROR: E0-01 Warning! The AC circuit may have failed. Contact a service technician. Would you like to switch to low-quality print mode and print?" is displayed on the display unit 161. Additionally, "Switch" and "Cancel" buttons will appear below the message.

[0104] Next, in step S4, the control unit 10 determines whether or not it is OK to switch to the low-quality print mode (step S4).

[0105] If switching to the low-quality print mode is OK (if the determination in step S4 is Yes), in step S5, the control unit 10 switches the charging method from AC to DC (step S5), and ends the process.

[0106] Regarding the application of voltage to the developing unit 61, there are an AC method in which a voltage in which an AC component is superimposed on a DC component is applied to the developing unit, and a DC method in which a voltage consisting of only a DC component is applied to the developing unit 61.

[0107] However, in the case of the developing unit 61, the presence or absence of the superimposition of the AC component only affects the amount of toner consumed and the difference in the image boundary edge, so the application of the developing unit 61 can be either a DC or AC method.

[0108] Furthermore, when an abnormality is detected in the generation circuit of the AC component of the charging voltage application unit, the developing unit 61 may or may not be switched from an AC system to a DC system.

[0109] On the other hand, if switching to low-quality printing mode is not OK (if the judgment in step S4 is No), in step S6, the control unit 10 causes the display unit 161 to display a message indicating that a service technician is required due to a failure in the AC circuit (step S6), and ends the processing.

[0110] Fig. 8 shows an example of the charging voltage Vo of the charging voltage application unit 171 and the developing voltage of the developing voltage application unit 172 of the digital multifunction peripheral 1 of Fig. 1. Fig. 8(A) shows an example of the developing voltage and charging voltage Vo when an AC component is superimposed, and Fig. 8(B) shows an example of the developing voltage and charging voltage Vo when no AC component is superimposed.

[0111] In the case where an AC component is superimposed, in the example of Figure 8(A), the upper limit of the setting for the charging DC is -850V, the development DC is set to -450V, and the charging DC is set to -600V, and the potential difference Δ between the development DC and the charging DC is 150V.

[0112] Incidentally, it is known that in the DC charging method, when the surface potential VL of the photosensitive drum 59 is set to -500V, a voltage that is reduced by approximately 500V from the applied voltage is charged onto the surface of the photosensitive drum 59. Therefore, if the reduced voltage is set to 500V, a voltage of -500V must be added to the -500V, and the DC component of the charging voltage Vo must be applied at -1000V.

[0113] On the other hand, in the case of an AC charging method, for example, when the surface potential VL of the photosensitive drum 59 is set to -500 V, it is known that the DC component voltage applied is charged almost unchanged on the surface of the photosensitive drum 59. Therefore, it is necessary to apply -500 V.

[0114] Here, if an additional -500V is to be applied to the -600V charged DC, it is necessary to apply -1100V. However, since the upper limit of the setting for the charging DC is -850V, the DC component of the charging voltage Vo is set to the upper limit of -850V, and then the charging DC is set to -350V, assuming a 500V reduction in the applied voltage (an addition of -500V). Then, the potential difference Δ between the development DC and the charging DC is 150V, so the development DC becomes −200V.

[0115] In this way, if the AC circuit abnormality detection unit 174 detects an abnormality in the AC component generation circuit of the charging voltage application unit 171, the charging method is switched from AC to DC and applied to the charging unit, thereby realizing a digital multifunction printer 1 that is capable of printing even if a malfunction occurs in the AC component generation circuit of the charging voltage.

[0116] (Variation) As a modification of the first embodiment, a setting as to whether or not to automatically switch to a low-quality print mode when an AC circuit fails may be accepted in advance. When a setting to automatically switch to the low-quality print mode is accepted, a message to that effect may be displayed on the display unit 161 when switching to the low-quality print mode or during operation in the low-quality print mode.

[0117] In this way, if the AC circuit abnormality detection unit 174 detects an abnormality in the AC component generation circuit of the charging voltage application unit 171, the charging method is automatically switched from AC to DC based on the settings and applied to the charging unit, so that a digital multifunction printer 1 can be realized that enables printing without compromising user convenience even if a malfunction occurs in the AC component generation circuit of the charging voltage.

[0118] [Embodiment 2] Next, a process for switching the charging method of the charging voltage application unit 171 of the digital multifunction peripheral 1 according to the second embodiment of the present disclosure will be described with reference to FIGS.

[0119] FIG. 9 is a block diagram showing a schematic configuration of a digital multifunction peripheral 1 according to the second embodiment of the present disclosure. The digital multifunction peripheral 1 according to the second embodiment of this disclosure is the same as the digital multifunction peripheral 1 according to the first embodiment of this disclosure, except that it does not include an AC circuit abnormality detection unit and further includes an image quality adjustment unit 19.

[0120] The image quality adjustment unit 19 includes an image density sensor 191 . The image density sensor 191 is a reflective sensor that shines light onto a test toner patch formed on the intermediate transfer belt 55 during image quality adjustment, and reads the image density from the reflected light. The image quality adjustment unit 19 adjusts the image quality based on the image density of the toner patch read by the image density sensor 191 .

[0121] The other configurations of the digital multifunction peripheral 1 according to the second embodiment of this disclosure are the same as those of the first embodiment (FIGS. 1, 2, 4, and 5), and therefore will not be described.

[0122] <Switching Process of Charging Method of Charging Voltage Application Unit 171 of Digital Multifunction Peripheral 1 According to Second Embodiment of the Present Disclosure> Next, a process of switching the charging method of the charging voltage application unit 171 of the digital multifunction peripheral 1 according to the second embodiment of the present disclosure will be described. FIG. 10 is a flowchart showing an example of a charging method switching process of the charging voltage application unit 171 of the digital multifunction peripheral 1 according to the second embodiment of the present disclosure.

[0123] In step S11 of FIG. 10, the control unit 10 executes image quality adjustment at a predetermined timing, such as after the device main body is started up (step S11).

[0124] Specifically, the control unit 10 controls the image forming unit 12 to form a test toner patch on the intermediate transfer belt 55, and controls the image density sensor 191 to shine light on the toner patch and perform image quality adjustment based on the image density of the toner patch read from the reflected light.

[0125] In the next step S12, the control unit 10 determines whether or not deterioration in image quality is confirmed even after the image quality adjustment (step S12).

[0126] If no deterioration in image quality is confirmed (if the determination in step S12 is No), the control unit 10 ends the process.

[0127] On the other hand, if deterioration in image quality is confirmed even after image quality adjustment (if the judgment in step S12 is Yes), in step S13, the control unit 10 causes the display unit 161 to display a message indicating the possibility of device failure and whether or not to switch to low-image-quality printing mode (step S13).

[0128] Next, in step S14, the control unit 10 determines whether or not it is OK to switch to the low-quality print mode (step S14).

[0129] If switching to the low-quality print mode is OK (if the determination in step S14 is Yes), in step S15, the control unit 10 switches the charging method from AC to DC (step S15), and ends the process.

[0130] In this case, after the charging method is switched to DC, the control unit 10 may perform image quality adjustment again.

[0131] On the other hand, if switching to low-quality printing mode is not OK (if the judgment in step S14 is No), in step S16, the control unit 10 causes the display unit 161 to display a message indicating that the device is malfunctioning and that a service technician is required to take action (step S16), and then ends the process.

[0132] In this way, if the image density sensor 191 detects the image density of the toner image during image quality adjustment and finds that the image quality has deteriorated, and if the image quality adjustment does not improve the deterioration, the charging method is switched from AC to DC and applied to the charging unit, thereby realizing a digital multifunction printer 1 that is capable of printing even if a malfunction occurs in the AC component generation circuit of the charging voltage.

[0133] [Embodiment 3] Next, a process for switching the charging method of the charging voltage application unit 171 of the digital multifunction peripheral 1 according to the third embodiment of the present disclosure will be described with reference to FIG.

[0134] The schematic configuration of the digital multifunction peripheral 1 according to the third embodiment of this disclosure is the same as that of the first embodiment (FIGS. 1 to 5), and therefore a description thereof will be omitted.

[0135] In the first embodiment, regardless of whether the machine is monochrome or color, when an abnormality in the AC circuit is detected, the charging method is switched from AC to DC to perform low-quality printing, or a message is displayed on the display unit 161 indicating that the machine is broken and that a service technician needs to take action.

[0136] On the other hand, in the third embodiment, the process when an abnormality in the AC circuit is detected in any of the first to fourth visible image forming units 51 to 54 corresponding to the toners of the colors black (K), cyan (C), magenta (M), and yellow (Y) will be described.

[0137] FIG. 11 is a flowchart showing an example of a charging method switching process of the charging voltage application unit 171 of the digital multifunction peripheral 1 according to the third embodiment of the present disclosure. It is assumed that the process of FIG. 11 is performed for the voltage application section 17 of each of the first to fourth visible image forming units 51 to .

[0138] In step S21 of FIG. 11, the charging voltage application unit 171 charges the charging unit by an AC charging method in which an AC component voltage is superimposed on a DC component voltage (step S21).

[0139] Next, in step S22, the control unit 10 determines whether or not an abnormality in the AC circuit has been detected (step S22).

[0140] If no abnormality in the AC circuit has been detected (if the determination in step S22 is No), the control unit 10 returns the process to step S21.

[0141] On the other hand, if an abnormality in the AC circuit is detected (if the determination in step S22 is Yes), in step S23, the control unit 10 determines whether or not there is an abnormality in the AC circuit of the black (K) unit (step S23).

[0142] If there is an abnormality in the AC circuit of the black (K) unit (if the judgment in step S23 is Yes), in step S24, the control unit 10 causes the display unit 161 to display a message indicating that the AC circuit has failed and asking whether or not to switch to low-quality printing mode for both monochrome and color printing (step S24).

[0143] Next, in step S25, the control unit 10 determines whether or not it is OK to switch to the low-quality print mode for monochrome printing (step S25).

[0144] If switching to low-quality printing mode is OK for both monochrome and color printing (if the judgment in step S25 is Yes), in step S26, the control unit 10 switches the charging method of the black (K) unit from AC to DC when printing monochrome, and switches the charging method of all color units from AC to DC when printing color (step S26), and then ends the processing.

[0145] On the other hand, if switching to low-quality printing mode is not OK for both monochrome and color printing (if the judgment in step S25 is No), in step S27, the control unit 10 causes the display unit 161 to display a message indicating that a service technician is required due to a failure in the AC circuit (step S27), and ends the processing.

[0146] Furthermore, (although not shown) the determination of whether or not the switching in step S25 is OK may be made separately for monochrome / color printing, and the charging method may be switched.

[0147] On the other hand, if there is an abnormality in the AC circuits of the cyan (C), magenta (M), and yellow (Y) color units in step S23 (if the judgment in step S23 is No), in step S28, the control unit 10 causes the display unit 161 to display a message indicating that the AC circuit has failed and asking whether or not to switch to a low-quality print mode for color printing (step S28).

[0148] Next, in step S29, the control unit 10 determines whether or not it is OK to switch to the low-quality print mode for color printing (step S29).

[0149] If switching to the low-quality print mode for color printing is OK (if the determination in step S29 is Yes), in step S30, the control unit 10 switches the charging method of the units for all colors from AC to DC (step S30), and ends the process.

[0150] On the other hand, if switching to low-quality printing mode for color printing is not OK (if the judgment in step S29 is No), in step S27, the control unit 10 causes the display unit 161 to display a message indicating that a service technician is required due to a failure in the AC circuit (step S27), and ends the process.

[0151] In this way, if the abnormality in the AC component generation circuit of the charging voltage application unit 171 is related to the black (K) toner image used in monochrome printing, the charging method of the black (K) unit is switched from AC to DC and applied to the charging unit during monochrome printing, and the charging method of all color units is switched from AC to DC and applied to the charging unit during color printing, so that monochrome / color printing can continue, albeit with lower image quality.

[0152] If the charging method of the cyan (C), magenta (M), and yellow (Y) units is left as AC and only the charging method of the black (K) unit is switched to DC, it is expected that the image quality will be worse for printed images that use a higher proportion of black (K) toner. Therefore, to avoid mixing AC and DC, the charging method of all color units is switched to DC (the same applies to step S30).

[0153] On the other hand, if the abnormality in the AC component generation circuit of the charging voltage application unit 171 relates to the toner images of each color of cyan (C), magenta (M), or yellow (Y), the charging method of the units of all colors is switched from AC to DC and applied to the charging unit, so that color printing can continue although with lower image quality, and monochrome printing can be performed with high image quality as before.

[0154] Therefore, it is possible to realize a digital multifunction peripheral 1 that is capable of printing even if a problem occurs in the circuit that generates the AC component of the charging voltage.

[0155] Preferred aspects of the present disclosure include any combination of the above-described aspects. In addition to the above-described embodiments, various modifications of this disclosure are possible. These modifications should not be interpreted as not belonging to the scope of this disclosure. This disclosure should include all modifications within the scope of the claims and their equivalents. [Explanation of symbols]

[0156] 1: digital multifunction peripheral, 2: fixing unit, 10: control unit, 11: image data acquisition unit, 12: image forming unit, 13: storage unit, 14: image processing unit, 15: communication unit, 16: operation panel, 17: voltage application unit, 18: power supply, 19: image quality adjustment unit, 31: recording medium, 50: optical system unit, 51: first visible image forming unit, 52: second visible image forming unit, 53: third visible image forming unit, 54: fourth visible image forming unit, 55: intermediate transfer belt, 56: secondary transfer unit, 57: internal paper feed unit, 58: manual paper feed unit, 59, 65, 66, 67: photosensitive drum, 60: charging roller, 61, 61a, 61b, 61c, 61d: development units, 62, 62a, 62b, 62c, 62d: primary transfer unit, 63, 63a: cleaning blade, 64: laser light source, 68, 69: tension roller, 70: waste toner box, 71: fixing belt, 72: pressure roller, 73, 74: feed roller, 75: paper output tray, 76: static elimination unit, 77: cleaning roller, 161: display unit, 162: operation unit, 171: charging voltage application unit, 172: developing voltage application unit, 173: transfer voltage application unit, 174: AC circuit abnormality detection unit, 175: charging method switching unit, 181: charging power supply, 182: developing power supply, 183: transfer power supply, 191: image density sensor, 601, 613a, 622a: core metal, 611a: developing roller, 612a: Developer, 621a: Transfer roller, ER: Discharge roller, R1, R2: Rotation direction, RT1, RT2, RT3, RT4: Conveyance path, Vb: Development voltage, Vd, VL: Surface potential, Vo: Charging voltage, Vt: Transfer voltage

Claims

1. an image forming unit including a photosensitive member, a charging unit that charges the photosensitive member, a charging voltage applying unit that applies a predetermined charging voltage to the charging unit, an exposure unit that forms an electrostatic latent image on the photosensitive member, a developing unit that supplies toner to the photosensitive member to form a toner image corresponding to the electrostatic latent image, a developing voltage applying unit that applies a predetermined developing voltage to the developing unit, a transfer unit that transfers the toner image to a recording medium, and a fixing unit that heat-fixes the toner image to the recording medium; a control unit that controls the image forming unit, the charging voltage application unit switchably applies to the charging unit a first charging voltage in which an AC component is superimposed on a DC component or a second charging voltage in which only a DC component is present; the developing voltage application unit applies a developing voltage having at least a DC component to the developing unit; an image forming apparatus characterized in that a DC component of the first charging voltage and a DC component of the developing voltage when the charging voltage application unit applies the first charging voltage to the charging unit are set to values ​​different from a DC component of the second charging voltage and a DC component of the developing voltage when the charging voltage application unit applies the second charging voltage to the charging unit.

2. further comprising an AC circuit abnormality detection unit that detects an abnormality in a generation circuit of an AC component of the charging voltage application unit; 2. The image forming apparatus according to claim 1, wherein, when the AC circuit abnormality detection unit detects an abnormality in the AC component generation circuit of the charging voltage application unit, the control unit switches the charging voltage application unit from the first charging voltage to the second charging voltage and applies the same to the charging unit.

3. 2. The image forming apparatus according to claim 1, wherein the DC component of the second charging voltage is set to a value obtained by adding the difference in surface potential of the photosensitive member that occurs with or without the superposition of an AC component to the DC component of the first charging voltage.

4. 3. The image forming apparatus according to claim 2, wherein, when a sum obtained by adding a difference in surface potential of the photosensitive member caused by the presence or absence of superimposition of an AC component to the DC component of the first charging voltage exceeds a maximum value of the DC component that the charging voltage application unit can output, the DC component of the second charging voltage is set to the maximum value of the DC component, and the value obtained by subtracting the sum exceeding the maximum value of the DC component from the DC component of the developing voltage is set as the value of the DC component of the developing voltage when the charging voltage application unit applies the second charging voltage to the charging unit.

5. an image quality adjustment unit that adjusts image quality using an image density sensor that detects the image density of the toner image; 2. The image forming apparatus according to claim 1, wherein the control unit switches the charging voltage application unit from the first charging voltage to the second charging voltage and applies the same to the charging unit when the image density sensor detects the image density of the toner image during the image quality adjustment and confirms that the image quality has deteriorated, and when the image quality adjustment does not improve the deterioration of the image quality.

6. the image forming unit has a color printing function of forming a color image using the toner images of all colors, black, cyan, magenta, and yellow, and a monochrome printing function of forming a monochrome image using the black toner image, 3. The image forming apparatus according to claim 2, wherein, when the AC circuit abnormality detection unit detects an abnormality in the AC component generation circuit of the charging voltage application unit, if the abnormality in the AC component generation circuit of the charging voltage application unit relates to the black toner image, the control unit switches the charging voltage application unit related to the black toner image from the first charging voltage to the second charging voltage and applies it to the charging unit during monochrome printing, and switches the charging voltage application unit related to the toner images of all colors from the first charging voltage to the second charging voltage and applies it to the charging unit during color printing; on the other hand, if the abnormality in the AC component generation circuit of the charging voltage application unit relates to the toner images of cyan, magenta, or yellow, the control unit switches the charging voltage application unit related to the toner images of all colors from the first charging voltage to the second charging voltage and applies it to the charging unit.

Images