JP2020067512A - Image forming apparatus - Google Patents

Abstract

To prevent unnecessary consumption of developer when detection of abnormality in an exposure device is performed based on digital patches and analog patches formed in different methods with/without exposure.SOLUTION: A control unit forms digital patches (S2), and when the digital patches have a low density (Yes in S3), executes "sensor diagnostic processing" (S4). When a density sensor is abnormal (Yes in S5), the control unit ends "exposure abnormality detection processing" without executing "exposure diagnostic processing" (S10) and does not form analog patches, and thereby can prevent unnecessary consumption of developer. When the density sensor is normal (No in S5), the control unit executes "substrate diagnostic processing" on high-voltage substrates (S6 to S8). When at least one of the high-voltage substrates is abnormal (Yes in S9), the control unit ends the "exposure abnormality detection processing" without executing the "exposure diagnostic processing" and does not form the analog patches, and thereby can prevent unnecessary consumption of developer resulting from abnormality in the high-voltage substrates.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an image forming apparatus using an electrophotographic technique such as a printer, a copying machine, a facsimile or a composite machine.

  In an electrophotographic image forming apparatus, an exposure apparatus forms an electrostatic latent image on a photosensitive drum charged by a charging apparatus, and the developing apparatus develops the electrostatic latent image into a toner image. The developing device can perform development using, for example, a developer containing toner and carrier. Then, the toner image on the photosensitive drum is primarily transferred to the intermediate transfer belt by the primary transfer device, and then secondarily transferred from the intermediate transfer belt to the recording material. The recording material on which the toner image is transferred is conveyed to the fixing device, and is heated and pressed by the fixing device, so that the toner image is fixed on the recording material. As described above, in the image forming apparatus, an image is formed through various processes such as charging, exposure, development, and transfer. Therefore, if an abnormality occurs in any of these processes, an image defect may occur. Conventionally, when a streak-shaped image defect occurs on a recording material, a toner image for detection (hereinafter referred to as a detection image) is formed on the intermediate transfer belt by a different method, and based on these detection images. Therefore, the abnormality of the exposure apparatus is detected (Patent Document 1). The detection image is a digital patch formed in the exposed area of the area charged by the "exposure" method, and an analog patch formed over the entire area charged by the "no exposure" method. There is.

JP, 2015-132642, A

  By the way, conventionally, like the device described in Patent Document 1, when the density of the digital patch detected by the density sensor is low, it is determined that the streak image is generated and the analog patch is formed. However, if the density sensor is abnormal in the first place, it is determined that the streak image has occurred even though the actual density of the digital patch is normal, and an analog patch is formed, and the developer (mainly toner ) Was wasted. Alternatively, if the density sensor is normal, but an abnormality occurs in any of the high-voltage boards that apply voltage to the charging device and the developing device (or the primary transfer device), the density of the digital patch may become low. is there. In that case, if an analog patch is generated despite the occurrence of an abnormality in the high-voltage board, the developer (toner or carrier) may be unnecessarily consumed according to the magnitude relationship of the voltage applied by each high-voltage board. It was

  In view of the above problems, the present invention provides an image forming apparatus capable of suppressing wasteful consumption of developer when detecting an abnormality of an exposure apparatus based on detection images formed by different methods with and without exposure. To aim.

  An image forming apparatus according to the present invention includes an image carrier, a charging device that charges the image carrier by applying a charging voltage, an exposure device that exposes the image carrier to form an electrostatic latent image, and a developing device. A developing device capable of developing an electrostatic latent image of the image bearing member into a toner image by a developer by applying a voltage, an intermediate transfer member that contacts and rotates with the image bearing member, and the image bearing member by applying a transfer voltage. Transfer device capable of transferring the toner image to the intermediate transfer body, a density sensor for detecting the density of the toner image on the intermediate transfer body, and a first toner for detection formed by performing exposure by the exposure device. When the density of the image is less than the first density and the density of the second toner image for detection formed without performing the exposure by the exposure device is the second density or more, the abnormality of the exposure device is detected. Control means capable of executing abnormality detection mode The control means forms the first toner image during execution of the abnormality detection mode, and detects the abnormality of the density sensor when the density of the first toner image is less than the first density. When the density sensor is abnormal, the abnormality detection mode is ended without forming the second toner image.

  An image forming apparatus according to the present invention includes an image carrier, a charging device that charges the image carrier by applying a charging voltage, an exposure device that exposes the image carrier to form an electrostatic latent image, and a developing device. A developing device capable of developing an electrostatic latent image of the image bearing member into a toner image by a developer by applying a voltage, an intermediate transfer member that contacts and rotates with the image bearing member, and the image bearing member by applying a transfer voltage. Transfer device capable of transferring the toner image to the intermediate transfer member, a density sensor for detecting the density of the toner image on the intermediate transfer member, a charging high voltage substrate for applying a charging voltage to the charging device, and the developing device. A developing high voltage substrate for applying a developing voltage to the device, a transfer high voltage substrate for applying a transfer voltage to the transfer device, and a density of a first toner image for detection formed by performing exposure by the exposure device is less than a first density And the exposure apparatus And a control means capable of executing an abnormality detection mode for detecting an abnormality of the exposure device when the density of the second toner image for detection formed without performing the exposure is higher than the second density. The control means performs abnormality detection of the charging high-voltage substrate, the developing high-voltage substrate, and the transfer high-voltage substrate after forming the first toner image during execution of the abnormality detection mode, and if at least one is abnormal, The abnormality detection mode is terminated without forming the second toner image.

  An image forming apparatus according to the present invention includes an image carrier, a charging device that charges the image carrier by applying a charging voltage, an exposure device that exposes the image carrier to form an electrostatic latent image, and a developing device. A developing device capable of developing an electrostatic latent image on the image carrier into a toner image by a developer by applying a voltage, a density sensor for detecting the density of the toner image on the image carrier, and exposure by the exposure device. When the density of the first toner image for detection formed by the above is less than the first density, and the density of the second toner image for detection formed without performing the exposure by the exposure device is the second density or more. A control unit capable of executing an abnormality detection mode for detecting an abnormality of the exposure apparatus, wherein the control unit forms the first toner image when the abnormality detection mode is executed, When the concentration of is less than the first concentration, Performs abnormality detection of the degree sensor, when the density sensor is abnormal, and ends the abnormality detection mode without forming the second toner image, it is characterized.

  An image forming apparatus according to the present invention includes an image carrier, a charging device that charges the image carrier by applying a charging voltage, an exposure device that exposes the image carrier to form an electrostatic latent image, and a developing device. A developing device capable of developing an electrostatic latent image on the image bearing member into a toner image by a developer by applying a voltage, a density sensor for detecting the density of the toner image on the image bearing member, and a charging voltage applied to the charging device. The charging high-voltage substrate to be applied, the developing high-voltage substrate to apply a developing voltage to the developing device, the density of the first toner image for detection formed by performing the exposure by the exposure device is less than the first density, and Control means capable of executing an abnormality detection mode for detecting an abnormality of the exposure device when the density of the second toner image for detection formed without performing the exposure by the exposure device is equal to or higher than the second density. , The control means is When the mode is executed, after the formation of the first toner image, the abnormality detection of the charging high-voltage substrate and the development high-voltage substrate is performed. If at least one is abnormal, the second toner image is not formed and the abnormality detection mode is set. The feature is that it ends.

  According to the present invention, it is possible to suppress wasteful consumption of a developer when detecting an abnormality of an exposure device based on a first toner image and a second toner image formed by different methods with and without exposure. it can.

FIG. 1 is a schematic diagram showing the configuration of an image forming apparatus of this embodiment. Schematic which shows a density sensor. The figure explaining a control part. The circuit diagram which shows a high voltage board. The flowchart which shows the exposure abnormality detection processing of this embodiment. The flowchart which shows a sensor diagnostic process. The flowchart which shows a board | substrate diagnostic process. The flowchart which shows exposure diagnosis processing. FIG. 6 is a schematic diagram showing a configuration of an image forming apparatus according to another embodiment. The flowchart which shows the exposure abnormality detection processing of other embodiment.

<Image forming device>
The configuration of the image forming apparatus of this embodiment will be described with reference to FIG. The image forming apparatus 100 shown in FIG. 1 is a tandem type full-color printer in which image forming units PY, PM, PC, and PK of yellow, magenta, cyan, and black are arranged along the intermediate transfer belt 5.

  In the image forming portion PY, a yellow toner image is formed on the photosensitive drum 1Y and transferred to the intermediate transfer belt 5. In the image forming unit PM, a magenta toner image is formed on the photosensitive drum 1M and transferred to the intermediate transfer belt 5. In the image forming units PC and PK, cyan toner images and black toner images are formed on the photosensitive drums 1C and 1K, respectively, and are transferred onto the intermediate transfer belt 5. The four-color toner images transferred to the intermediate transfer belt 5 are conveyed to the secondary transfer portion T2 as the intermediate transfer belt 5 moves, and are transferred to a recording material S (sheet material such as paper or OHP sheet). Next is transcribed. The recording materials S are taken out one by one from a paper feed cassette (not shown) and conveyed to the secondary transfer portion T2.

  The image forming units PY, PM, PC, and PK have substantially the same configuration except that the colors of toners used in the developing devices 4Y, 4M, 4C, and 4K are different from yellow, magenta, cyan, and black. Therefore, in the following, the yellow image forming portion PY will be described as a representative example, and description of the other image forming portions PM, PC, PK will be omitted.

  In the image forming portion PY, a charging device 2Y, an exposure device 3Y, a developing device 4Y, a primary transfer roller 6Y, and a cleaning blade 7Y are arranged so as to surround the photosensitive drum 1Y as an image carrier. The photosensitive drum 1Y is an electrophotographic photosensitive member having a photosensitive layer formed on a conductive substrate, and is rotated in the direction of arrow R1 in FIG. 1 at a predetermined process speed.

  The charging device 2Y is, for example, a corona discharger or a charging roller, which charges the photosensitive drum 1Y to a uniform negative-polarity dark part potential by applying a charging voltage. The exposure device 3Y generates a laser beam obtained by ON-OFF modulating scanning line image data in which separated color images of respective colors are developed from a laser light emitting element, and scans this with a rotating mirror to charge the surface of the photosensitive drum 1Y. Write the electrostatic latent image of the image.

  The developing device 4Y includes a developing container 41Y that can store a developer, and a developing sleeve 42Y that holds the developer in the developing container 41Y and can rotate. The developing sleeve 42Y as a developer carrying member conveys the developer to the developing area facing the photosensitive drum 1Y. Then, by applying the developing voltage to the developing sleeve 42Y, the electrostatic latent image on the photosensitive drum 1Y can be developed into a toner image by the developer. In this embodiment, a two-component developer containing a non-magnetic toner and a magnetic carrier is used as the developer. The non-magnetic toner is obtained by encapsulating a colorant, a wax component, etc. in a resin such as polyester or styrene, and pulverizing or polymerizing the powder. The magnetic carrier is obtained by applying a resin coat to the surface layer of a core made of resin particles obtained by kneading ferrite particles or magnetic powder.

  The primary transfer roller 6Y is arranged to face the photosensitive drum 1Y with the intermediate transfer belt 5 interposed therebetween, and forms a primary transfer portion T1 of the toner image between the photosensitive drum 1Y and the intermediate transfer belt 5. At the primary transfer portion T1, a toner image can be primarily transferred from the photosensitive drum 1Y to the intermediate transfer belt 5 by applying a primary transfer voltage to the primary transfer roller 6Y. The cleaning blade 7Y removes the toner remaining on the photosensitive drum 1Y after the primary transfer.

  The intermediate transfer belt 5 as an intermediate transfer member is supported by being stretched around rollers such as a tension roller 61, a secondary transfer inner roller 62, and a drive roller 63, and driven by the drive roller 63 to rotate in the direction of arrow R2 in FIG. To be done. The tension roller 61 is a roller that presses the intermediate transfer belt 5 outward from the inner peripheral surface side of the intermediate transfer belt 5 to stretch it.

  The secondary transfer portion T2 is a toner image transfer nip portion to the recording material S formed by contacting the inner secondary transfer roller 62 with the intermediate transfer belt 5 supported by the outer secondary transfer roller 64. In the secondary transfer portion T2, a secondary transfer voltage is applied to the inner secondary transfer roller 62, so that the toner image is secondarily transferred from the intermediate transfer belt 5 to the recording material S. The toner remaining on the intermediate transfer belt 5 after the secondary transfer is removed by the belt cleaning device 18.

  The recording material S to which the toner image is secondarily transferred at the secondary transfer portion T2 is conveyed to the fixing device 16. Although not shown, the fixing device 16 fixes the toner image on the recording material S by applying pressure by a roller or belt facing each other and heat by a heat source such as a heater. The recording material S on which the toner image is fixed by the fixing device 16 is ejected outside the machine body.

<Density sensor>
In the present embodiment, as shown in FIG. 1, the density sensor 9 moves in the moving direction of the intermediate transfer belt 5 between the primary transfer portion T1 and the secondary transfer portion T2 of the black image forming portion PK, and the intermediate transfer portion T2. It is provided so as to face the outer peripheral surface of the belt 5. Specifically, the density sensor 9 is arranged at a position that substantially faces the tension roller 61 via the intermediate transfer belt 5.

  The density sensor 9 will be described with reference to FIG. The density sensor 9 is a reflection type optical sensor, and as shown in FIG. 2, it is arranged so that the reflected light of the patch toner image F formed on the intermediate transfer belt 5 can be detected. The density sensor 9 includes a light emitting unit 91 such as an LED, a light receiving unit 92 such as a photodiode, and a light amount control unit 93 that controls the amount of light emitted from the light emitting unit 91. The light emitting section 91 irradiates the intermediate transfer belt 5 with light such as infrared light at an angle of 45 degrees with respect to the normal line of the intermediate transfer belt 5. The light receiving section 92 is arranged at a position symmetrical to the light emitting section 91 with respect to the normal line of the intermediate transfer belt 5, and the intermediate transfer in which the patch toner image F is not formed, which is obtained by irradiating the light by the light emitting section 91. Regularly reflected light is received from the surface of the belt 5 and the patch toner image F. Since the specularly reflected light from the intermediate transfer belt 5 mainly enters the light receiving unit 92, when the patch toner image F is formed on the intermediate transfer belt 5, the amount of reflected light received by the light receiving unit 92 decreases. Since the output level (voltage value) of the density sensor 9 is proportional to the amount of reflected light, the density of the patch toner image F can be grasped based on the output level of the density sensor 9.

  The light amount control unit 93 adjusts the voltage applied to the light emitting unit 91 to control the light emission amount of the light emitting unit 91. By changing the emitted light amount of the light emitting unit 91, the reflected light amount of the same object irradiated with light can be made different. For example, when the amount of light emitted from the light emitting section 91 is increased, the amount of reflected light of the same object also increases in proportion thereto. The light amount control unit 93 operates the light emitting unit 91 with an emission light amount suitable for detecting the density of the patch toner image F.

  In the case of the present embodiment, the amount of light emitted from the light emitting unit 91 is adjusted so that the amount of reflected light on the surface of the intermediate transfer belt on which the patch toner image F is not formed reaches the target level. Specifically, the light emitting unit 91 emits light so that the output level of the density sensor 9 according to the average amount of reflected light for one round of the surface of the intermediate transfer belt 5 is, for example, “3.3 ± 0.05 (V)”. The amount of light is adjusted. By adjusting the amount of light emitted from the light emitting section 91 based on the average amount of reflected light in this way, the density of the patch toner image F is detected even if the gloss of the surface of the intermediate transfer belt 5 changes due to repeated use (that is, durability). It is possible to adjust the emitted light amount suitable for this.

<Control part>
As shown in FIG. 1, the image forming apparatus 100 includes a control unit 10. The control unit 10 will be described with reference to FIG. In addition to the illustrated components, the control unit 10 includes, for example, various motors that drive the photosensitive drums 1Y to 1K, the developing sleeves 42Y to 42K, the driving roller 63, a power source that applies a voltage to the secondary transfer inner roller 62, and fixing. Various devices such as the device 16 are connected. However, since they are not the gist of the invention, their illustration and description are omitted.

  The control unit 10 as a control unit includes, for example, a CPU (Central Processing Unit) 101 that performs various controls of the image forming apparatus 100 such as an image forming operation, and a memory 102. The memory 102 includes a ROM (Read Only Memory) and a RAM (Random Access Memory), and stores various programs and data for controlling the image forming apparatus 100. The CPU 101 can execute an image forming job (program) stored in the memory 102 and operate the image forming apparatus 100 to form an image. In the case of the present embodiment, the CPU 101 can execute the “exposure abnormality detection process” (see FIGS. 5 and 10 described later) stored in the memory 102. It should be noted that the memory 102 can temporarily store the calculation processing result and the like accompanying the execution of various programs.

  The density sensor 9 described above is connected to the control unit 10 via an input / output interface. As described above, the density sensor 9 detects the reflected light of the patch toner image formed on the intermediate transfer belt 5 and the reflected light of the surface of the intermediate transfer belt on which the patch toner image is not formed. The control unit 10 transmits the emitted light amount signal (voltage value) to the light amount control unit 93 (see FIG. 2) of the density sensor 9 so that the reflected light amount of the reflected light reaches a predetermined light amount level. Along with this, the control unit 10 receives a reflected light amount signal (voltage value) obtained by irradiation of light from the density sensor 9, and detects the density of the patch toner image based on this. The control unit 10 determines the density of the patch toner image based on the difference amount between the reflected light amount of the surface of the intermediate transfer belt on which the patch toner image is not formed and the reflected light amount of the patch toner image formed on the intermediate transfer belt 5. To detect.

  Further, the operation unit 70 and the display unit 80 are connected to the control unit 10 via a signal input / output interface. The operation unit 70 is, for example, an operation panel or an external terminal that allows a user to execute various programs and input various data. In the case of the present embodiment, the user can use the operation unit 70 to input execution of an image forming job or an exposure abnormality detection process (see FIGS. 5 and 10 described later).

  The display unit 80 can display an apparatus status display including an error display of an image forming operation, a notification of an abnormal portion, and the like, and a menu display that presents various programs executable by the user, such as a liquid crystal screen or For example, an external display. A virtual operator may be displayed on the display unit 80 by the control unit 10, and the virtual operator may be used to accept an operation of starting execution of various programs and an operation of inputting various data by the user. In addition, in the case of the present embodiment, when notifying the user of an abnormal point, it may be possible to notify by not using the display on the display unit 80 but, for example, blinking light by an LED or generating a warning sound by a speaker.

  Further, the developing high-voltage substrates 200Y to 200K, the charging high-voltage substrates 300Y to 300K, and the primary transfer high-voltage substrates 400Y to 400K are connected to the control unit 10 via the input / output interface. The developing high-voltage boards 200Y to 200K are power supply devices for applying a developing voltage to the developing sleeves 42Y to 42K. The charging high voltage substrates 300Y to 300K are power supply devices for applying a charging voltage to the charging devices 2Y to 2K. The primary transfer high voltage substrates 400Y to 400K are power supply devices for applying a primary transfer voltage to the primary transfer rollers 6Y to 6K. The CPU 101 outputs an output setting signal (setting value) and an ON / OFF signal at a predetermined timing in image formation to control each voltage. In the case of the present embodiment, the CPU 101 can detect the abnormality of each high-voltage board by monitoring the output determination signal output from each high-voltage board. The output setting signal is, for example, a PWM signal of “3.4 V, 50 kHz” and outputs a signal according to the target voltage value. The ON / OFF signal is, for example, a transformer drive clock signal of “50 kHz / 25% High duty”. The output determination signal is a signal that allows the control unit 10 to detect either “High” or “Low” as described later.

<High-voltage board>
The developing high voltage substrates 200Y to 200K, the charging high voltage substrates 300Y to 300K, and the primary transfer high voltage substrates 400Y to 400K will be described with reference to FIG. However, since the developing high voltage substrates 200Y to 200K, the charging high voltage substrates 300Y to 300K, and the primary transfer high voltage substrates 400Y to 400K have the same configuration, the developing high voltage substrate 200Y will be described below as an example.

  As shown in FIG. 4, the developing high voltage substrate 200Y is mainly composed of a constant voltage control circuit 201, a high voltage rectifying section 202, a voltage detecting section 203, and an output determining section 204. An output setting signal and an ON / OFF control signal are input from the control unit 10 to the constant voltage control circuit 201. When the ON signal is given, the constant voltage control circuit 201 supplies the transmission output voltage to the transformer TM. The AC voltage generated by the transformer TM is rectified and smoothed by the high voltage rectification unit 202, and is output as a high voltage development output (high voltage development value) of the DC voltage.

  The voltage detection unit 203 divides the high voltage output of development and “+3.4 V” by three resistors R201, R202, and R203 to generate a voltage (called a development voltage detection value: “0 to 3.0 V” in this embodiment). ) Is output. Further, the voltage corresponding to the development high voltage output is fed back to the constant voltage control circuit 201 via the resistor R201. By this feedback, the constant voltage control circuit 201 automatically controls the transmission output voltage to the transformer TM so that the developing high voltage output converges to a desired value ("-450V" to "-700V" in this embodiment). To do.

  The output determination unit 204 is composed of a comparator IC 201 and a resistor R204, and outputs an output determination signal when the development voltage detection value is input. For example, when the development high voltage output is "0V", the development voltage detection value is "3.0V", and this voltage is input to the + terminal of the IC201. On the other hand, the voltage input to the-terminal is "2.3V". Therefore, the output terminal of the IC 201 is open, the output determination signal is “3.0V”, and the control unit 10 detects “High”. On the other hand, when the development high voltage output is "-550V", the development voltage detection value is "1.5V", which is lower than the voltage at the-terminal. Therefore, the output of the IC 201 is "0V", and the control unit 10 detects "Low". In the present embodiment, the control unit 10 detects "High" when the developing high-voltage output is "0 V", although the developing voltage is controlled to be applied (ON signal is output). In that case, the control unit 10 determines that some abnormality has occurred in the high-voltage developing substrate 200Y.

  By the way, for example, when an abnormality occurs in the exposure device 3Y, it becomes difficult to properly write the electrostatic latent image on the charged photosensitive drum 1Y, and as a result, even if the development device 4Y develops the desired toner image. Cannot be generated. Therefore, the image forming apparatus 100 forms a digital patch and an analog patch on the intermediate transfer belt 5 in order to detect an abnormality of the exposure device 3Y, and detects the abnormality of the exposure device based on the density of the toner image for detection. Has been adopted. The digital patch is formed by a so-called digital developing method, and the analog patch is formed by a so-called analog developing method.

  In the digital developing system, the charging device 2Y charges the surface potential of the photosensitive drum 1Y so that the surface potential of the photosensitive drum 1Y becomes lower in absolute value, and the exposure device 3Y charges the surface potential of the photosensitive drum 1Y as an absolute value, based on the voltage applied to the developing sleeve 42Y. An electrostatic latent image is formed so that it becomes higher at. Then, the electrostatic latent image formed on the photosensitive drum 1Y by the developing device 4Y (in other words, the area exposed by the exposing device 3Y) is developed into a toner image. In the case of the digital developing method, for example, the voltage applied to the developing sleeve 42Y is "-550V", the surface potential of the photosensitive drum 1Y is "-700V", and the electrostatic latent image by the exposure device 3Y is "-450V". A digital patch of the solid image is formed. On the other hand, in the analog developing method, the charging device 2Y charges the surface potential of the photosensitive drum 1Y so that the surface potential of the photosensitive drum 1Y becomes large in absolute value with reference to the voltage applied to the developing sleeve 42Y, but the exposure device 3Y exposes the photosensitive drum 1Y. No (that is, no electrostatic latent image is formed). In this case, the developing device 4Y forms a toner image on the entire charged area of the photosensitive drum 1Y. In the case of the analog developing method, for example, the voltage applied to the developing sleeve 42Y is set to "-700V" and the surface potential of the photosensitive drum 1Y is set to "-600V" to form an analog patch. In both the digital developing method and the analog developing method, the primary transfer voltage applied to the primary transfer roller 6Y is about "+500 to + 1500V".

  As described above, conventionally, when the density sensor 9 is abnormal, an analog patch may be formed although the actual density of the digital patch is normal. However, if the actual density of the digital patch is normal, the exposure device 3Y is operating normally. Therefore, it is the developer (mainly the toner) that forms the analog patch and detects the abnormality of the exposure device 3Y. ) Is a waste of. Further, in the past, after the formation of the digital patch, the analog patch may be formed even if the developing high-voltage substrate 200Y or the charging high-voltage substrate 300Y is abnormal. However, if an abnormality occurs in the developing high voltage substrate 200Y or the charging high voltage substrate 300Y, the voltage applied to the developing sleeve 42Y becomes higher in absolute value than, for example, "-700V", and the surface potential of the photosensitive drum 1Y becomes "-". The absolute value may be lower than "600V". In other words, the potential difference between the developing sleeve 42Y for forming the analog patch and the surface potential of the photosensitive drum 1Y becomes wider than the desired potential difference (so-called fog potential). In this case, the analog patch may not be properly formed, and the developer (mainly toner) may be unnecessarily discharged from the developing device 4Y to the photosensitive drum 1Y. Alternatively, when an abnormality occurs in the developing high voltage substrate 200Y or the charging high voltage substrate 300Y, the voltage applied to the developing sleeve 42Y becomes lower in absolute value than, for example, “−700V”, and the surface potential of the photosensitive drum 1Y becomes “−”. The absolute value may be lower than "600V". In this case, if the surface potential of the photosensitive drum 1Y is extremely lower than the potential of the developing sleeve 42Y (for example, the potential of the developing sleeve 42Y "0V", the surface potential of the photosensitive drum 1Y "-600V"), the developing device 4Y from the photosensitive drum. Carriers can be mainly exhaled for 1Y. On the other hand, if the surface potential of the photosensitive drum 1Y is extremely higher than the potential of the developing sleeve 42Y (for example, the developing sleeve 42Y potential "-700V", the photosensitive drum 1Y surface potential "0V"), the developing device 4Y to the photosensitive drum 1Y. On the other hand, the toner can be mainly discharged. Here, the case where the toner has a negative charging characteristic has been described as an example.

  Therefore, in this embodiment, when the abnormality detection of the exposure apparatus is performed based on the digital patch and the analog patch, the analog patch is not formed when the density sensor 9 is abnormal. This suppresses wasteful consumption of the developer due to the abnormality of the density sensor 9. Then, when the density sensor 9 is normal, it is confirmed that there is no abnormality in each high-voltage board, and then the analog patch is formed. This suppresses wasteful consumption of the developer due to the abnormality of each high-voltage board. This will be described below.

<Exposure abnormality detection processing>
The exposure abnormality detection processing of this embodiment will be described with reference to FIGS. 1 to 3 and FIGS. 5 to 8. The exposure abnormality detection process (abnormality detection mode) shown here is executed by the control unit 10 in response to a user input from the operation unit 70 or every time an image is formed on, for example, 10,000 recording materials S. .

  As shown in FIG. 5, the control unit 10 transmits a light emission amount signal to the light amount control unit 93 (see FIG. 2) to adjust the light emission amount of the density sensor 9 (S1). For example, the amount of light emitted from the density sensor 9 is adjusted to a value such that the amount of light reflected from the surface of the intermediate transfer belt 5 is “2.3V”. Then, the control unit 10 applies digital patches for each color of yellow, magenta, cyan, and black so as to be aligned at a predetermined position on the intermediate transfer belt 5 that can be detected by the density sensor 9 and in the moving direction of the intermediate transfer belt 5. Form (S2). As described above, in the digital patch of each color, the voltage applied to the developing sleeves 42Y to 42K is “−550V”, the surface potential of each of the photosensitive drums 1Y to 1K is “−700V”, and the exposure devices 3Y to 3K are static. The latent image is formed to be "-450V". The density of the digital patch (first toner image) of each color thus formed is read by the density sensor 9. The amount of reflected light from the digital patch becomes smaller as the amount of applied toner increases. Therefore, the output level of the density sensor 9 also decreases as the density of the digital patch increases.

  The control unit 10 determines whether the output level of the density sensor 9 proportional to the amount of reflected light is larger than a predetermined value (for example, 1.8 V) (S3). When the output level of the density sensor 9 is equal to or lower than the predetermined value (No in S3), that is, when the density of the digital patch is equal to or higher than the predetermined density (first density), the control unit 10 ends the "exposure abnormality detection process". To do. In this case, since the density of the digital patch formed with "exposure" is an appropriate density, it is assumed that the exposure apparatuses 3Y to 3K are normal, and the "exposure abnormality detection process" is not performed without performing the "exposure diagnosis process" (S10). To finish.

  On the other hand, when the output level of the density sensor 9 is higher than the predetermined value (Yes in S3), that is, when the density of the digital patch is less than the predetermined density (less than the first density), the control unit 10 controls the density sensor 9 "Sensor diagnosis process" is executed (S4). Then, the control unit 10 determines whether or not the concentration sensor 9 is abnormal as a result of executing the "sensor diagnosis process" (S5). When the density sensor 9 is abnormal (Yes in S5), the control unit 10 ends the "exposure abnormality detection process" without executing the "exposure diagnosis process" (S10), that is, without forming an analog patch. When the density sensor 9 is normal (No in S5), the controller 10 executes the "substrate diagnosis process" (S6 to S8) for each of the developing high voltage substrate, the charging high voltage substrate, and the primary transfer high voltage substrate. The “sensor diagnosis processing” and the “board diagnosis processing” will be described later (see FIGS. 6 and 7). The "substrate diagnostic process" for each of the developing high-voltage substrate, the charging high-voltage substrate, and the primary transfer high-voltage substrate may be performed only on the high-voltage substrate having a color whose output level of the density sensor 9 is higher than a predetermined value. The order of execution of the "sensor diagnosis processing", the development high-voltage board, the charging high-voltage board, and the primary transfer high-voltage board is not particularly limited.

  The reason why the density of the digital patch is low may be that the density sensor 9 is abnormal in the first place. Alternatively, when each high voltage substrate such as the development high voltage substrate 200Y to 200K, the charging high voltage substrate 300Y to 300K, and the primary transfer high voltage substrate 400Y to 400K is abnormal (failure), the density of the digital patch is actually low. Become. That is, if the developing high-voltage substrates 200Y to 200K are abnormal, the voltage applied to the developing sleeves 42Y to 42K does not become "-550V" (approximately 0V), and the surface potentials of the photosensitive drums 1Y to 1K are "-700V" or static. The absolute value is lower than "-450V" of the latent image. In this case, the toner does not move from the developing devices 4Y to 4K to the photosensitive drums 1Y to 1K (that is, the development is not performed), so that the density of the digital patch becomes thin.

  If the charging high-voltage substrates 300Y to 300K are abnormal, the surface potential of the photosensitive drums 1Y to 1K does not become "-700V" (approximately 0V), and the voltage "-550V" applied to the developing sleeves 42Y to 42K, or electrostatic. It becomes lower in absolute value than "-450V" of the latent image. In this case, the toner moves from the developing devices 4Y to 4K to the photosensitive drums 1Y to 1K, but the toner hardly moves to the electrostatic latent image, so that the density of the digital patch becomes thin.

  If the primary transfer high-voltage substrates 400Y to 400K are abnormal, the toner on the photosensitive drums 1Y to 1K does not move toward the intermediate transfer belt 5 (that is, the primary transfer is not performed). Therefore, the digital patch primary-transferred to the intermediate transfer belt 5 is performed. The concentration of is reduced.

  Returning to the description of FIG. 1, the control unit 10 determines whether or not there is an abnormality in each of the developing high-voltage substrates 200Y to 200K, the charging high-voltage substrates 300Y to 300K, and the primary transfer high-voltage substrates 400Y to 400K (S9). When there is no abnormality in each of the high-voltage boards (No in S9), the control unit 10 executes the "exposure diagnosis processing" (S10), and ends the "exposure abnormality detection processing". In this case, the cause of the low density of the digital patch is not the abnormality of the density sensor 9 or each high-voltage board, but the charged amount of toner in the developer. However, in that case, if the analog patch (second toner image) is formed in the same toner state (toner charge amount) as the digital patch, the abnormality of the exposure devices 3Y to 3K can be detected based on these. On the other hand, if at least one of the high-voltage boards is abnormal (Yes in S9), the control unit 10 does not execute the "exposure diagnosis process", that is, does not form an analog patch, and ends the "exposure defect detection process". To do.

<Sensor diagnosis processing>
The sensor diagnosis process (see S4 of FIG. 5) will be described with reference to FIG. As shown in FIG. 6, the control unit 10 sets the emitted light amount signal to “0 V” for the light amount control unit 93 of the density sensor 9 (S11). Accordingly, the control unit 10 acquires the reflected light amount signal (Soff) obtained by the irradiation of light from the density sensor 9 after 150 msec (S12), for example (S13). Subsequently, the control unit 10 sets the emitted light amount signal to "3.3V" for the light amount control unit 93 of the density sensor 9 (S14). Accordingly, the control unit 10 acquires the reflected light amount signal (Son) obtained by the irradiation of light from the density sensor 9 after 150 msec (S15), for example (S16). The control unit 10 obtains a light amount difference (absolute value of Son-Soff) between the obtained two reflected light amounts, and determines whether or not the obtained light amount difference is “0.1 V” or more (S17). When the calculated light amount difference is “0.1 V” or more (Yes in S17), the control unit 10 determines that the density sensor 9 is operating normally, and ends the “sensor diagnosis process”. On the other hand, when the calculated light amount difference is less than “0.1 V” (No in S17), the control unit 10 determines that the density sensor 9 is abnormal, and displays a message indicating that the density sensor 9 is abnormal on the display unit 80. (S18).

<Board diagnosis processing>
The board diagnosis process (see S6 to S8 in FIG. 5) will be described with reference to FIG. 3 and FIG. However, since the substrate diagnosis processing for the developing high-voltage board, the charging high-voltage board, and the primary transfer high-voltage board may share the same operation, the substrate diagnosis processing for the yellow developing high-voltage board 200Y will be described here as an example.

  As shown in FIG. 7, the control unit 10 outputs an “ON signal” to the developing high-voltage board 200Y (S21). Accordingly, the control unit 10 acquires the output determination signal output from the developing high-voltage board 200Y in response to the output of the "ON signal", for example, after 100 msec (S22), and whether the output determination signal is "High". It is detected whether it is "Low" (S23). When the control unit 10 detects that the output determination signal is "Low" (No in S23), the development high-voltage substrate 200Y is determined to be operating normally, and the "substrate diagnosis process" ends. On the other hand, when the control unit 10 detects that the output determination signal is “High” (Yes in S23), the display unit 80 displays a message indicating that the development high-voltage board 200Y is abnormal, indicating that the development high-voltage board 200Y is abnormal. Then (S24), the "board diagnosis process" is terminated.

  When the developing high-voltage board 200Y is abnormal, if the developing sleeve 42Y continues to operate in a state where the potential of the developing sleeve 42Y is excessively higher than the surface potential of the photosensitive drum 1Y, a large amount of magnetic carriers are discharged to the photosensitive drum 1. There is a possibility that In this case, the amount of the developer in the developing device 4Y is reduced, and recovery is difficult. Therefore, when the control unit 10 displays a message indicating the abnormality of the developing high-voltage board 200Y on the display unit 80, the control unit 10 may simultaneously display, on the display unit 80, a message prompting replacement of the developing device 4Y. If the charging high-voltage board 300Y is abnormal, the toner in the developing device 4Y may be depleted, so the control unit 10 causes the display unit 80 to simultaneously display, for example, a message prompting replacement of the developing device 4Y. It may be displayed.

<Exposure diagnosis processing>
Next, the exposure diagnosis process (see S10 of FIG. 5) will be described with reference to FIG. As shown in FIG. 8, the control unit 10 transmits a light emission amount signal to the light amount control unit 93 (see FIG. 2) to adjust the light emission amount of the density sensor 9 (S31). For example, the amount of light emitted from the density sensor 9 is adjusted to a value such that the amount of light reflected from the surface of the intermediate transfer belt 5 is “2.3V”. Then, the control unit 10 forms a yellow analog patch at a predetermined position on the intermediate transfer belt 5 that can be detected by the density sensor 9 (S32). As described above, the analog patch is formed by setting the voltage applied to the developing sleeve 42Y to "-750V" and the surface potential of the photosensitive drum 1Y to "-600V". The density of the analog patch thus formed is read by the density sensor 9.

  The control unit 10 determines whether the output level of the density sensor 9 proportional to the amount of reflected light is higher than a predetermined value (for example, 1.8V) (S33). When the output level of the density sensor 9 is higher than the predetermined value (Yes in S33), that is, when the density of the analog patch is lower than the predetermined density (second density), the control unit 10 causes the exposure apparatus 3Y to operate normally. Therefore, the "exposure diagnosis process" is terminated. On the other hand, when the output level of the density sensor 9 is equal to or lower than the predetermined value (No in S33), that is, when the density of the analog patch is equal to or higher than the predetermined density (second density or higher), the control unit 10 causes the exposure device 3Y to malfunction. Then, the “exposure diagnosis process” is terminated. At that time, the control unit 10 displays a message indicating the abnormality of the exposure apparatus 3Y on the display unit 80 (S34). That is, in this case, the image can be correctly formed by the analog developing method, but the image cannot be correctly formed by the digital developing method involving the exposure process. In this way, the control unit 10 can form an analog patch of a color in which the density of the digital patch is low, and detect the abnormality of the exposure device 3Y based on the digital patch and the analog patch.

  As described above, in the present embodiment, when the "exposure abnormality detection process" that detects an abnormality in the exposure apparatuses 3Y to 3K based on the digital patch and the analog patch is performed, the abnormality of the density sensor 9 is detected and the density sensor is detected. If 9 is abnormal, an analog patch will not be formed. As a result, wasteful consumption of the developer due to the abnormality of the density sensor 9 can be suppressed. Then, when the density sensor 9 is normal, the analog high-voltage boards 200Y to 200K, the charging high-voltage boards 300Y to 300K, and the high-voltage boards of the primary transfer high-voltage boards 400Y to 400K are confirmed to be normal before forming the analog patch. I chose According to this, when the density of the digital patch is low due to the abnormality of each high-voltage board, the analog patch is not formed. If the analog patch is not formed, the toner or carrier is unlikely to be discharged from the developing devices 4Y to 4K onto the photosensitive drums 1Y to 1K. That is, when the abnormality of the exposure devices 3Y to 3K is detected, it is possible to suppress the wasteful consumption of the toner and the carrier due to the abnormality of the high voltage substrate.

<Other Embodiments>
In the above embodiment, the case where the density sensor 9 capable of detecting the density of the toner image such as a digital patch or an analog patch formed on the intermediate transfer belt 5 is provided is described as an example, but the present invention is not limited to this. . For example, as shown in FIG. 9, a plurality of density sensors 90Y to 90K may be provided so that the densities of the toner images formed on the photosensitive drums 1Y to 1K can be detected. Specifically, the density sensors 90Y to 90K are arranged on the downstream side of the developing position of the developing sleeves 42Y to 42K and on the upstream side of the primary transfer portion T1 with respect to the rotation direction of the photosensitive drums 1Y to 1K (arrow R1 direction).

  In the case of the above configuration, in the above-mentioned "substrate diagnosis process" (see S6 to S8 in Fig. 5), the "substrate diagnosis process" (S8 in Fig. 5) does not have to be performed for the primary transfer high-voltage substrates 400Y to 400K. This is because the digital patch or the analog patch whose density is detected by the density sensors 90Y to 90K is formed on the photosensitive drums 1Y to 1K as described above, and thus is not easily affected by the abnormality of the primary transfer high-voltage substrates 400Y to 400K. Because. The "exposure abnormality detection process" in the case of the above configuration will be described with reference to FIG. 10 and FIGS. Here, a case is shown where it is executed in response to a user input from the operation unit 70. When executed in response to a user input from the operation unit 70, the “sensor diagnosis process” (see FIG. 6) does not have to be performed for the density sensors 90Y to 90K. This is because when the user feels that the density of the image formed on the recording material S is low, the operation unit 70 is operated to execute the “exposure abnormality detection process”.

  As shown in FIG. 10, the control unit 10 arranges yellow, magenta, cyan, and cyan at a predetermined position on the intermediate transfer belt 5 that can be detected by the density sensors 90Y to 90K and in a line in the moving direction of the intermediate transfer belt 5. A digital patch is formed for each color of black (S2). The control unit 10 executes the "substrate diagnosis process" (S6, S7) for each of the developing high voltage substrates 200Y to 200K and the charging high voltage substrates 300Y to 300K. The control unit 10 determines whether or not there is an abnormality in each of the high-voltage developing boards 200Y to 200K and the charging high-voltage boards 300Y to 300K (S9). When there is no abnormality in each of the high-voltage boards (No in S9), the control unit 10 executes the "exposure diagnosis processing" (S10), and ends the "exposure abnormality detection processing". On the other hand, if at least one of the high-voltage boards is abnormal (Yes in S9), the control unit 10 does not execute the "exposure diagnosis process", that is, does not form an analog patch, and ends the "exposure defect detection process". To do.

  In the above-described embodiment, the toner images of the respective colors are primarily transferred from the photosensitive drums 1Y to 1K of the respective colors to the intermediate transfer belt 5, and then the composite toner images of the respective colors are secondarily transferred onto the recording material S at once. Although the image forming apparatus has been described, the present invention is not limited to this. For example, the above-described embodiment can be applied even to an image forming apparatus of a direct transfer system in which the photosensitive drums 1Y to 1K of each color are directly transferred to the recording material S.

1Y (1M, 1C, 1K) ... Image carrier (photosensitive drum), 2Y (2M, 2C, 2K) ... Charging device, 3Y (3M, 3C, 3K) ... Exposure device, 4Y (4M, 4C, 4K) ... Developing device, 5 ... Intermediate transfer member (intermediate transfer belt), 6Y (6M, 6C, 6K) ... Transfer device (primary transfer roller), 9 (90Y to 90K) ... Density sensor, 10 ... Control means (control section), 70 ... Operation part, 80 ... Display part, 100 ... Image forming apparatus, 200Y (200M, 200C, 200K) ... Development high voltage substrate, 300Y (300M, 300C, 300K) ... Charging high voltage substrate, 400Y (400M, 400C, 400K) … Transfer high voltage substrate (primary transfer high voltage substrate)

Claims (9)

An image carrier,
A charging device that charges the image carrier by applying a charging voltage,
An exposure device that exposes the image carrier to form an electrostatic latent image;
A developing device capable of developing the electrostatic latent image of the image bearing member into a toner image by a developer by applying a developing voltage;
An intermediate transfer member that contacts the image carrier and rotates,
A transfer device capable of transferring the toner image of the image carrier to the intermediate transfer member by applying a transfer voltage;
A density sensor for detecting the density of the toner image on the intermediate transfer member;
The density of the first toner image for detection formed by exposure by the exposure device is less than the first density, and the density of the second toner image for detection formed without exposure by the exposure device is less than the first density. A control unit capable of executing an abnormality detection mode for detecting an abnormality of the exposure apparatus when the density is two or more,
The control means forms the first toner image during execution of the abnormality detection mode, and detects the abnormality of the density sensor when the density of the first toner image is less than the first density. Is abnormal, the second toner image is not formed and the abnormality detection mode is terminated,
An image forming apparatus characterized by the above. A charging high voltage substrate for applying a charging voltage to the charging device,
A high-voltage developing substrate for applying a developing voltage to the developing device;
A transfer high voltage substrate for applying a transfer voltage to the transfer device;
The control means performs abnormality detection of the charging high-voltage substrate, the developing high-voltage substrate, and the transfer high-voltage substrate when the density sensor is normal during execution of the abnormality detection mode, and when at least one is abnormal, Ending the abnormality detection mode without forming the second toner image,
The image forming apparatus according to claim 1, wherein: Equipped with a display,
The control means, when executing the abnormality detection mode, displays, on the display unit, one of the density sensor, the charging high-voltage substrate, the developing high-voltage substrate, and the transfer high-voltage substrate that have an abnormality.
The image forming apparatus according to claim 2, wherein: An image carrier,
A charging device that charges the image carrier by applying a charging voltage,
An exposure device that exposes the image carrier to form an electrostatic latent image;
A developing device capable of developing the electrostatic latent image of the image bearing member into a toner image by a developer by applying a developing voltage;
An intermediate transfer member that contacts the image carrier and rotates,
A transfer device capable of transferring the toner image of the image carrier to the intermediate transfer member by applying a transfer voltage;
A density sensor for detecting the density of the toner image on the intermediate transfer member;
A charging high voltage substrate for applying a charging voltage to the charging device,
A high-voltage developing substrate for applying a developing voltage to the developing device;
A transfer high-voltage substrate for applying a transfer voltage to the transfer device,
The density of the first toner image for detection formed by exposure by the exposure device is less than the first density, and the density of the second toner image for detection formed without exposure by the exposure device is less than the first density. A control unit capable of executing an abnormality detection mode for detecting an abnormality of the exposure apparatus when the density is two or more,
When the abnormality detection mode is executed, the control unit detects an abnormality of the charging high-voltage substrate, the developing high-voltage substrate, and the transfer high-voltage substrate after forming the first toner image, and if at least one is abnormal, Ending the abnormality detection mode without forming the second toner image,
An image forming apparatus characterized by the above. An image carrier,
A charging device that charges the image carrier by applying a charging voltage,
An exposure device that exposes the image carrier to form an electrostatic latent image;
A developing device capable of developing the electrostatic latent image of the image bearing member into a toner image by a developer by applying a developing voltage;
A density sensor for detecting the density of the toner image on the image carrier,
The density of the first toner image for detection formed by exposure by the exposure device is less than the first density, and the density of the second toner image for detection formed without exposure by the exposure device is less than the first density. A control unit capable of executing an abnormality detection mode for detecting an abnormality of the exposure apparatus when the density is two or more,
The control means forms the first toner image during execution of the abnormality detection mode, and detects the abnormality of the density sensor when the density of the first toner image is less than the first density. Is abnormal, the second toner image is not formed and the abnormality detection mode is terminated,
An image forming apparatus characterized by the above. A charging high voltage substrate for applying a charging voltage to the charging device,
A developing high voltage substrate for applying a developing voltage to the developing device;
The control unit detects an abnormality of the charging high-voltage substrate and the developing high-voltage substrate when the density sensor is normal during execution of the abnormality detection mode, and when at least one is abnormal, the second toner image is detected. Ends the abnormality detection mode without forming
The image forming apparatus according to claim 5, wherein Equipped with a display,
The control means displays, on the display unit, one of the density sensor, the charging high-voltage board, and the developing high-voltage board that has an abnormality when the abnormality detection mode is executed.
The image forming apparatus according to claim 6, wherein An image carrier,
A charging device that charges the image carrier by applying a charging voltage,
An exposure device that exposes the image carrier to form an electrostatic latent image;
A developing device capable of developing the electrostatic latent image of the image bearing member into a toner image by a developer by applying a developing voltage;
A density sensor for detecting the density of the toner image on the image carrier,
A charging high voltage substrate for applying a charging voltage to the charging device,
A high-voltage developing substrate for applying a developing voltage to the developing device;
The density of the first toner image for detection formed by exposure by the exposure device is less than the first density, and the density of the second toner image for detection formed without exposure by the exposure device is less than the first density. A control unit capable of executing an abnormality detection mode for detecting an abnormality of the exposure apparatus when the density is two or more,
When the abnormality detecting mode is executed, the control unit detects an abnormality of the charging high-voltage substrate and the developing high-voltage substrate after the formation of the first toner image, and if at least one is abnormal, the second toner image is detected. Ends the abnormality detection mode without forming
An image forming apparatus characterized by the above. An operation unit capable of inputting execution of the abnormality detection mode is provided,
The control means executes the abnormality detection mode according to an input from the operation unit,
9. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

Images