JP2021162754A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that, at the occurrence of an abnormality in contact and separation mechanisms, can specify the cause of the abnormality.SOLUTION: An image forming apparatus 100 uses contact and separation mechanisms to bring photoconductor drums 201Y, 201M, 201C into contact with an intermediate transfer belt 217 and separate the photoconductor drums from the intermediate transfer belt. When an abnormality occurs in the contact and separation mechanisms, the image forming apparatus 100 forms a cyan image on the photoconductor drum 201C, while using the contact and separation mechanisms to repeatedly perform the contact and separation of the photoconductor drums 201Y, 201M, 201C with respect to the intermediate transfer belt 217. The image on the photoconductor drum 1201C is transferred to the intermediate transfer belt 217. The image transferred to the intermediate transfer belt 217 is detected by a toner patch sensor 153. The image forming apparatus 100 determines a failed portion of the contact and separation mechanisms based on a result of detection performed by the toner patch sensor 153.SELECTED DRAWING: Figure 1

Description

The present invention relates to an image forming apparatus such as an electrophotographic method and an electrostatic recording method.

A tandem type is widely used as an image forming apparatus for forming a color image. The tandem image forming apparatus includes a plurality of photosensitive drums corresponding to different colors and an intermediate transfer body. A color image is formed on the intermediate transfer body by forming an image of a color corresponding to each photosensitive drum and sequentially superimposing and transferring an image of each color from each photosensitive drum on the intermediate transfer body. An image is formed on the sheet by transferring the color image from the intermediate transfer body to the sheet. Such an image forming apparatus can operate in two operation modes: a color mode in which a color image is formed by a plurality of photosensitive drums and a monochrome mode in which a monochrome image is formed only by the photosensitive drums used for forming a black image. Is.

When forming a monochrome image, it is not necessary to keep the photosensitive drum on which a chromatic color image other than black is formed in an image-forming state. Therefore, the image forming apparatus switches the operation mode according to the content of the instructed job. In the monochrome mode, it is preferable to keep the non-operating color photosensitive drum away from the intermediate transfer body. Therefore, the image forming apparatus often includes a contact separation mechanism between the chromatic color photosensitive drum and the intermediate transfer body. .. The contact separation mechanism provides a position sensor capable of detecting the contact separation state at at least one of the positions in order to detect whether the photosensitive drum is in the contact position or the separation position with respect to the intermediate transfer body. It is common to have.

If the position sensor does not return a correct detection result, the controller of the image forming apparatus cannot grasp the accurate contact separation state between the photosensitive drum and the intermediate transfer body. In this case, the image forming apparatus may stop operating because normal image forming may not be possible. The state in which the position sensor does not return a correct detection result is a state in which the output of the position sensor does not change even if the controller instructs contact or separation.

Possible causes for the position sensor to be in such a state are an abnormality in the position sensor body, an abnormality in the mechanical mechanism of the contact separation mechanism, and an abnormality in the drive source. Examples of the abnormality of the position sensor main body include an electrical position sensor failure, a position sensor dropout, and an abnormality of a signal line for transmitting a detection result. Examples of abnormalities in the mechanical mechanism and the drive source of the contact separation mechanism include damage to the members of the contact separation mechanism itself, failure of the drive source, and abnormality in the transmission path of the driving force. In Patent Document 1, for such an abnormal state of the contact separation mechanism, a method of detecting the contact separation state of the contact separation mechanism from the shading of an image when image formation is performed, regardless of the position sensor. Has been proposed.

JP-A-2009-294435

The technique of Patent Document 1 only detects the contact separation state of the contact separation mechanism in which an abnormality has occurred. That is, it is not determined whether the location where the abnormality occurs is on the position sensor side, or on the mechanical mechanism or drive source side of the separation contact mechanism. Therefore, even if the user or the operator can detect the abnormality of the contact separation mechanism, it is difficult to identify the cause of the abnormality. This causes a long time to recover from the abnormal state when an abnormality occurs in the contact separation mechanism, which causes an increase in downtime until the recovery.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of identifying the cause when an abnormality occurs in the contact separation mechanism.

The image forming apparatus of the present invention includes a first image forming means for forming an image on the first image carrier, a second image forming means for forming an image on the second image carrier, the first image carrier and the above. A transfer body on which the image is transferred from each of the second image carriers and a position facing the first image carrier across the transfer body are provided, and the first image carrier is transferred to the transfer body. A first transfer means for transferring an image and a second transfer means provided at a position facing the second image carrier across the transfer body and transferring an image from the second image carrier to the transfer body. By moving the first detection means for detecting the image formed on the transfer body and the first transfer means, the contact state in which the first image carrier and the transfer body are in contact with each other and the above-mentioned It detects that the contact separation mechanism for switching between the first image carrier and the transfer body in a separated state and the first transfer means are in one of the contact state and the separated state. When the second detecting means does not detect the one state even if the contact separation mechanism is operated so that the first image carrier and the transferred body are in the one state. In addition, the contact separation mechanism is operated so as to be in the contact state and the contact separation mechanism is operated so as to be in the separation state, respectively, by the first image forming means. An image is formed on the first image carrier, the image formed on the first image carrier by the first transfer means is transferred to the transfer body, and the first image transferred to the transfer body is transferred. It is characterized by comprising a control means for determining whether the contact separation mechanism has a failure or the second detection means has a failure based on the detection result by the detection means.

According to the present invention, it is possible to identify the cause when an abnormality occurs in the contact separation mechanism.

The block diagram of the image forming apparatus. (A) and (b) are explanatory views of the contact separation state. Explanatory drawing of the controller. The flowchart which shows the abnormality detection processing at the time of contact separation operation. Explanatory drawing of the state when there is an abnormality in the contact separation mechanism. The flowchart which shows the abnormality determination processing of the contact separation mechanism. (A) and (b) are illustrations of a display screen. The figure of the start screen of the abnormality determination processing.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Configuration of image forming apparatus)
FIG. 1 is a configuration diagram of an image forming apparatus of the present embodiment. The image forming apparatus 100 includes an image forming unit 200Y, 200M, 200C, 200K, a transfer unit, a sheet feeding unit, and a fixing device 140 in order to form an image on a sheet. The image forming apparatus 100 includes an operation panel 160 as a user interface. The operation panel 160 includes an input key and a touch panel as an input device, and a display as an output device.

The image forming units 200Y, 200M, 200C, and 200K of the present embodiment form images of yellow (Y), magenta (M), cyan (C), and black (K). Therefore, the image forming units 200Y, 200M, 200C, and 200K each include photosensitive drums 201Y, 201M, 201C, and 201K on which images of different colors are formed. Y at the end of the code indicates yellow, M indicates magenta, C indicates cyan, and K indicates black. Hereinafter, when the colors are distinguished and described, Y, M, C and K are added to the end of the reference numerals, and when the colors are not distinguished, the Y, M, C and K at the end of the reference numerals are omitted.

The photosensitive drum 201 is a drum-shaped photoconductor having a photosensitive layer on its surface, and is an image carrier that supports a toner image. The photosensitive drum 201 rotates clockwise in the figure about the drum axis. The image forming unit 200 includes a charging roller 202, an exposure device 203, a developing device 204, and a drum cleaner 205 around the photosensitive drum 201. The charging roller 202 uniformly charges the surface of the rotating photosensitive drum 201. The exposure device 203 scans the surface of the charged photosensitive drum 201 with a laser beam modulated based on image data representing an image of the corresponding color. As a result, an electrostatic latent image corresponding to the color image corresponding to the surface of the photosensitive drum 201 is formed. The developer 204 develops an electrostatic latent image on the surface of the photosensitive drum 201 with a developer. As a result, a yellow toner image is formed on the photosensitive drum 201Y. A magenta toner image is formed on the photosensitive drum 201M. A cyan toner image is formed on the photosensitive drum 201C. A black toner image is formed on the photosensitive drum 201K.

The transfer unit includes an intermediate transfer belt 217, primary transfer rollers 211Y, 211M, 211C, 211K, and a secondary transfer roller 120. The intermediate transfer belt 217 is an endless belt, and is a transfer body on which toner images of each color are superimposed and transferred from the photosensitive drum 201. A plurality of primary transfer rollers 211Y, 211M, 211C, 211K are provided corresponding to the photosensitive drums 201Y, 201M, 201C, 201K. The primary transfer rollers 211Y, 211M, 211C, 211K are arranged at positions facing the corresponding photosensitive drums 201Y, 201M, 201C, 201K with the intermediate transfer belt 217 interposed therebetween. The intermediate transfer belt 217 rotates counterclockwise in the drawing, and the toner image is sequentially transferred from the photosensitive drums 201Y, 201M, 201C, and 201K according to the rotation. As a result, a full-color toner image is formed on the intermediate transfer belt 217. The transferred toner image is conveyed to the secondary transfer roller 120 by the rotation of the intermediate transfer belt 217. At the time of transfer, the primary transfer rollers 211Y, 211M, 211C, 211K are urged toward the photosensitive drums 201Y, 201M, 201C, 201K via the intermediate transfer belt 217. The toner remaining on the photosensitive drum 201 after transfer is removed by the drum cleaner 205.

The sheet feeding unit includes a paper feed cassette 101, a pickup roller 102, a resist roller 105, and a paper ejection roller 108. The paper cassette 101 accommodates a sheet on which an image is formed. The pickup roller 102, the resist roller 105, and the paper ejection roller 108 are arranged along a transfer path through which the sheet is conveyed. A secondary transfer roller 120 and a fixing device 140 are also provided in the transport path.

The pickup roller 102 feeds the sheet from the paper cassette 101 to the transport path. The pickup roller 102 conveys the fed sheet to the resist roller 105. A paper feed sensor 103 is provided on the downstream side of the pickup roller 102 in the sheet transport direction. The detection result of the paper feed sensor 103 is used to determine whether or not the sheet has been fed by the pickup roller 102. The resist roller 105 corrects the skew of the sheet with respect to the transfer direction, and transfers the sheet to the secondary transfer roller 120 according to the timing at which the toner image formed on the intermediate transfer belt 217 is transferred to the secondary transfer roller 120. do. A resist sensor 104 is provided on the upstream side of the resist roller 105. The resist roller 105 conveys the sheet at a timing when the tip of the sheet and the tip of the toner image on the intermediate transfer belt 217 coincide with each other at the position of the secondary transfer roller 120 according to the timing when the resist sensor 104 detects the sheet. do. For example, when the sheet is detected early with respect to the toner image, the resist roller 105 stops the sheet for a predetermined time and then restarts the sheet transfer.

The secondary transfer roller 120 transfers the full-color toner image formed on the intermediate transfer belt 217 to the sheet. The sheet on which the toner image is transferred is conveyed to the fixing device 140 by the secondary transfer roller 120. A belt cleaner 216 is provided in the vicinity of the intermediate transfer belt 217, and the toner remaining on the intermediate transfer belt 217 after transfer is removed by the belt cleaner 216.

The fuser 140 fixes the toner image on the sheet by heating and melting the toner transferred to the sheet and pressurizing the toner. The sheet on which the toner image is fixed is conveyed to the paper ejection roller 108 by the fixing device 140. The paper ejection roller 108 ejects the sheet to the ejection tray 109.

A toner patch sensor 153, which is a diffuse reflected light sensor, is provided in the vicinity of the intermediate transfer belt 217. The toner patch sensor 153 is arranged on the downstream side of the photosensitive drums 201Y, 201M, 201C, and 201K in the rotation direction of the intermediate transfer belt 217. The toner patch sensor 153 includes an LED (Light Emitting Diode) that emits infrared light as a light source, and a sensor that receives diffuse reflection light from the surface of the intermediate transfer belt 217 of infrared light generated from the LED. The toner patch sensor 153 can read the toner image formed on the intermediate transfer belt 217.

The primary transfer rollers 211Y, 211M, and 211C are configured to be movable so as to be in contact with and separated from the intermediate transfer belt 217. When the primary transfer rollers 211Y, 211M, 211C come into contact with the intermediate transfer belt 217, the intermediate transfer belt 217 comes into contact with the photosensitive drums 201Y, 201M, 201C. The primary transfer rollers 211Y, 211M, 211C are separated from the intermediate transfer belt 217, so that the intermediate transfer belt 217 is separated from the photosensitive drums 201Y, 201M, 201C. As the contact separation mechanism for that purpose, the image forming apparatus 100 includes a tension roller 212, 213, a transfer roller positioning member 214, a tension roller positioning member 215, and a contact separation position sensor 218.

FIG. 2 is an explanatory diagram of a contact separation state between the photosensitive drums 201Y, 201M, 201C and the intermediate transfer belt 217. FIG. 2A shows a contact state. FIG. 2B shows a separated state. When the image forming apparatus 100 operates in the color mode for forming a color image, the photosensitive drums 201Y, 201M, 201C and the intermediate transfer belt 217 are in contact with each other. In the contact state, the contact separation position sensor 218 does not detect the transfer roller positioning member 214, so that the contact state is turned off. When the image forming apparatus 100 operates in the monochrome mode for forming a monochrome image, the photosensitive drums 201Y, 201M, 201C and the intermediate transfer belt 217 are separated from each other. In the separated state, the contact separation position sensor 218 is turned on to detect the transfer roller positioning member 214.

As described above, in the color mode, the photosensitive drums 201Y, 201M, and 201C used for forming a chromatic image are brought into contact with the intermediate transfer belt 217 together with the photosensitive drum 201K. In the monochrome mode, the photosensitive drums 201Y, 201M, and 201C used for forming a chromatic image are separated from the intermediate transfer belt 217, and only the photosensitive drum 201K used for forming a black image is in contact with the intermediate transfer belt 217. become.

(controller)
FIG. 3 is an explanatory diagram of a controller that controls the operation of the image forming apparatus 100. The controller 300 includes a CPU (Central Processing Unit) 301, a ROM (Read Only Memory) 302, and a RAM (Random Access Memory) 303. Further, the controller 300 includes an EEPROM (Electrically Erasable Programmable Read-Only Memory) 304. The CPU 301 controls the operation of the image forming apparatus 100 by executing a control program stored in the ROM 302. The RAM 303 provides a work area when the CPU 301 executes processing.

The CPU 301 is connected to the network communication unit 306, the operation panel 160, and the I / O 305. The I / O 305 includes various motors that are drive sources for driving each part in the image forming apparatus 100, various sensors arranged in the image forming apparatus 100, and a control unit that controls each part in the image forming apparatus 100. , And the image processing unit 313 are connected. The CPU 301 controls the operation of each component in the image forming apparatus 100 via the I / O 305 to form an image.

The network communication unit 306 is a network interface for communicating with an external device such as a personal computer via a predetermined network. The CPU 301 receives a print operation start instruction from an external device via the network communication unit 306. The CPU 301 can also receive a print operation start instruction from the operation panel 160. Upon receiving the print operation start instruction, the CPU 301 starts the image forming operation on the sheet. The CPU 301 can notify the user and the operator of various notification contents by the operation panel 160.

The CPU 301 rotates and drives the pickup roller 102 by driving the paper feed motor 324 via the I / O 305. As a result, the pickup roller 102 starts feeding the sheet from the paper feed cassette 101 to the transport path. The CPU 301 rotates the resist roller 105 by driving the resist motor 325 via the I / O 305. The CPU 301 rotates the paper ejection roller 108 and the fixing roller provided in the fuser 140 by driving the paper ejection motor 326 via the I / O 305.

The CPU 301 rotates the photosensitive drum 201, the charging roller 202, and the developing device 204 by driving the drum motor 322 via the I / O 305. The CPU 301 rotates the primary transfer roller 211, the tension roller 212, and 213 by driving the transfer belt motor 321 via the I / O 305. The intermediate transfer belt 217 is rotated by the rotation of these roller groups that are rotationally driven by the transfer belt motor 321.

The CPU 301 moves the positions of the transfer roller positioning member 214 and the tension roller positioning member 215 by driving the contact separation motor 323 via the I / O 305. By moving the transfer roller positioning member 214 and the tension roller positioning member 215, the intermediate transfer belt 217 and the photosensitive drums 201Y, 201M, 201C are in contact with each other (FIG. 2A) or separated from each other (FIG. 2 (A)). b)). In the separated state, the detection result of the contact separation position sensor 218 is turned on. By driving the contact separation motor 323 by a predetermined amount with reference to the separation state, the photosensitive drums 201Y, 201M, 201C and the intermediate transfer belt 217 can be brought into contact with each other.

The CPU 301 causes the LED of the toner patch sensor 153 to emit light via the I / O 305, and acquires the sensor output. The intermediate transfer belt 217 has a small surface roughness and is sufficiently smooth, and even if infrared light is irradiated from the LED, diffuse reflection light is not detected by the sensor. Therefore, when the toner patch sensor 153 detects the surface of the intermediate transfer belt 217, the sensor output becomes low. On the other hand, since the surface roughness of the portion of the intermediate transfer belt 217 on which the toner image is formed becomes large, when infrared light is irradiated from the LED, diffuse reflection light of a light amount corresponding to the density of the toner image is generated. Occurs. Therefore, when the toner patch sensor 153 detects the toner image formed on the surface of the intermediate transfer belt 217, the sensor output becomes high. The sensor output of the toner patch sensor 153 is an analog signal, which is converted into a digital signal of 0 to 1023 level by the CPU 301.

The CPU 301 instructs the PWM control units 310Y, 310M, 310C, and 310K to process via the I / O 305. The PWM control unit 310 controls the voltage applied to the corresponding charging roller 202, the developing device 204, and the primary transfer roller 211 and the laser light output from the exposure device 203 by PWM (Pulse Width Modulation) control. .. The CPU 301 controls the voltage applied to the secondary transfer roller 120 by the PWM control unit 311 via the I / O 305. The CPU 301 controls the temperature of the fuser 140 by the PWM control unit 312 via the I / O 305. The CPU 301 causes the image processing unit 313 to perform predetermined image processing via the I / O 305. The image processing unit 313 processes the image data, and corrects, for example, the amount of laser light output by the PWM control unit 310 to the exposure device, the timing of irradiation, and the like.

(Image formation processing)
When the image forming apparatus 100 receives a job from an external device via the network communication unit 306, the CPU 301 interprets the job and starts the image forming process. First, the CPU 301 rotationally drives the pickup roller 102 to feed the sheets in the paper feed cassette 101 one by one to the transport path. The CPU 301 can confirm whether or not the normal paper feeding operation has been performed based on the detection result of the paper feeding sensor 103. Further, the CPU 301 prepares for image formation in time for the sheet to arrive at the secondary transfer roller 120, and starts image formation.

The CPU 301 performs the contact separation processing of the intermediate transfer belt 217 prior to the preparation for image formation. The CPU 301 puts the photosensitive drums 201Y, 201M, 201C and the intermediate transfer belt 217 before the start of the job in a separated state as shown in FIG. 2B.
When the content of the job instructs the formation of a color image, the CPU 301 first drives the contact separation motor 323 by a predetermined amount in order to operate in the color mode. As a result, the transfer roller positioning member 214 and the tension roller positioning member 215 move to the positions shown in FIG. 2A. As a result, the photosensitive drums 201Y, 201M, 201C and the intermediate transfer belt 217 are in contact with each other. After that, the CPU 301 rotates the photosensitive drums 201Y to 201K and the intermediate transfer belt 217.
When the content of the job dictates the formation of a monochrome image, the CPU 301 maintains the distance between the photosensitive drums 201Y, 201M, 201C and the intermediate transfer belt 217 in order to operate in the monochrome mode, and the photosensitive drum 201K and the intermediate are intermediate. The transfer belt 217 is rotated.
During this contact separation process, an abnormality detection of the contact separation mechanism described later is performed.

Next, image formation preparation is started in order from the component forming the most upstream yellow image in the rotation direction of the intermediate transfer belt 217. The parts that form the color image located downstream of the parts that form the yellow image are ready for image formation by shifting the timing by the time according to the distance between the photosensitive drums and the rotation speed of the intermediate transfer belt 217. Will be done.

Image formation preparation is performed as follows. First, the CPU 301 uniformly charges the surface of the photosensitive drum 201 by applying a charging bias to the charging roller 202 by the PWM control unit 310. At the timing when the fully charged position of the photosensitive drum 201 reaches a position close to the developing device 204, the CPU 301 applies a developing bias to the developing device 204 by the PWM control unit 310. The image formation preparation is completed by the above processing.

Image formation is performed as follows. When the image formation preparation is completed, the CPU 301 issues an image output instruction to the PWM control unit 310, causes the exposure device 203 to start irradiating the laser beam, and forms an electrostatic latent image on the photosensitive drum 201. The CPU 301 issues an instruction to the PWM control unit 310, develops an electrostatic latent image by the developing device 204, and forms a toner image on the photosensitive drum 201. The toner image formed on the photosensitive drum 201 is transferred to the intermediate transfer belt 217 by applying a primary transfer voltage at the position of the primary transfer roller 211. The toner image transferred to the intermediate transfer belt 217 is transferred to the secondary transfer roller 120.

In parallel with the image formation, the CPU 301 confirms whether or not the sheet transported along the transport path is detected by the resist sensor 104. The CPU 301 adjusts the timing according to the detection result of the resist sensor 104 and causes the resist roller 105 to convey the sheet to the secondary transfer roller 120. The CPU 301 transfers the toner image to the sheet by applying a secondary transfer voltage to the sheet and the toner image that have reached the secondary transfer roller 120. The sheet on which the toner image is transferred is fixed with the toner image by the fixing device 140 and discharged to the discharge tray 109 by the paper ejection roller 108.

When the job is completed, the CPU 301 sets the output of each PWM control unit 310 to zero to stop the image formation, and stops the photosensitive drum 201 and the intermediate transfer belt 217. After that, the CPU 301 separates the photosensitive drums 201Y, 201M, 201C from the intermediate transfer belt 217. That is, the CPU 301 drives the contact separation motor 323 by the same amount as at the time of contact to move the transfer roller positioning member 214 and the tension roller positioning member 215 to the separation positions shown in FIG. 2 (b). The abnormality detection of the contact separation mechanism performed during the separation operation will be described later. The above basic image forming operation is an example, and the present invention is not limited to the above configuration.

(Abnormality detection during contact separation operation)
FIG. 4 is a flowchart showing an abnormality detection process during the contact separation operation between the photosensitive drums 201Y, 201M, 201C and the intermediate transfer belt 217 executed by the CPU 301. The processing in the state where no abnormality has occurred will be described first, and then the processing when an abnormality has occurred will be described.

In the normal state where no abnormality has occurred, the processing is as follows. As described above, the contact separation mechanism abuts or separates the photosensitive drums 201Y, 201M, 201C and the intermediate transfer belt 217 according to the content of the job. The CPU 301 confirms whether to instruct contact or separation based on the content of the job (S401).

When instructing contact (S401: Y), the CPU 301 first confirms whether or not the detection result of the contact separation position sensor 218 is ON (S402). That is, the CPU 301 confirms whether or not the photosensitive drums 201Y, 201M, 201C and the intermediate transfer belt 217 are separated from each other.

When the detection result of the contact separation position sensor 218 is off (S402: N), the position of the positioning member is uncertain, so the contact separation position sensor 218 is once turned back on and then the contact operation is performed. There is a need. Therefore, the CPU 301 reversely rotates the contact separation motor 323 (S403). When operating normally, the photosensitive drums 201Y, 201M, and 201C are separated from each other within a predetermined time from the start of the reverse rotation of the contact separation motor 323, and reach a position where the output of the contact separation position sensor 218 is turned on. .. The predetermined time is, for example, 10 seconds. The CPU 301 determines whether or not the output of the contact separation position sensor 218 is turned on within 10 seconds after the contact separation motor 323 is rotated in the reverse direction (S404: N, S405). When the output of the contact separation position sensor 218 is turned on within 10 seconds (S405: Y), the same process (S406) as when the output of the contact separation position sensor 218 is turned on first is performed.

When the detection result of the contact separation position sensor 218 is off (S402: N), the CPU 301 rotates the contact separation motor 323 in the forward direction (S406). When the contact separation motor 323 is rotated in the forward direction while the contact separation position sensor 218 is on, the photosensitive drums 201Y, 201M, and 201C come into contact with each other within a predetermined time to operate normally. The position where the output of 218 is turned off is reached. The predetermined time is, for example, 10 seconds. The CPU 301 determines whether or not the output of the contact separation position sensor 218 is turned off within 10 seconds after the contact separation motor 323 is rotated in the forward direction (S407: N, S408).

In the present embodiment, the positions of the photosensitive drums 201Y, 201M, and 201C when the contact separation motor 323 is rotated forward for 1 second from the position where the output of the contact separation position sensor 218 is turned off are the positions where the contact state is reached. be. Therefore, when the output of the CPU 301 and the contact separation position sensor 218 is turned off (S408: Y), the motor is driven for 1 second from that point (S409), and then the contact separation motor 323 is stopped (S414). Under such control of the CPU 301, the contact separation mechanism brings the photosensitive drums 201Y, 201M, 201C and the intermediate transfer belt 217 into contact with each other.

When the CPU 301 instructs the separation based on the content of the job (S401: N), the CPU 301 first confirms whether or not the output of the contact separation position sensor 218 is off (S410). When the output of the contact separation position sensor 218 is on (S410: N), the CPU 301 does not drive the contact separation motor 323 because the photosensitive drums 201Y, 201M, 201C and the intermediate transfer belt 217 are already separated from each other. (S414). When the output of the contact separation position sensor 218 is off (S410: Y), the CPU 301 reversely rotates the contact separation motor 323 (S411).

When operating normally, the photosensitive drums 201Y, 201M, and 201C are separated from each other within a predetermined time from the start of the reverse rotation of the contact separation motor 323, and reach a position where the output of the contact separation position sensor 218 is turned on. .. The predetermined time is, for example, 10 seconds. The CPU 301 determines whether or not the output of the contact separation position sensor 218 is turned on within 10 seconds after the contact separation motor 323 is rotated in the reverse direction (S412: N, S413). When the output of the contact separation position sensor 218 is turned on within 10 seconds (S413: Y), the CPU 301 stops the contact separation motor 323 (S414). Under such control of the CPU 301, the contact separation mechanism separates the photosensitive drums 201Y, 201M, 201C and the intermediate transfer belt 217.

If an error occurs, the processing is as follows. The "abnormality" here means an abnormality of the sensing system and an abnormality of the mechanical / drive system. The abnormality of the sensing system is an abnormality in which the contact state and the separation state cannot be detected, and is an abnormality of the contact separation position sensor 218 main body and the line connecting the contact separation position sensor 218 and the CPU 301. The mechanical / drive system abnormality is such that the drive mechanism for moving the primary transfer rollers 211Y, 211M, 211C, such as the transfer roller positioning member 214 and the tension roller positioning member 215, does not move.

In either case, the CPU 301 acquires a fixed value output from the contact separation position sensor 218. Therefore, even if the contact separation motor 323 is rotated by any of the processes of S403, S406, and S411, the output of the contact separation position sensor 218 does not change. When the output of the contact separation position sensor 218 does not change even when the contact separation motor 323 is rotated for a predetermined time, the CPU 301 has a contact separation mechanism (S404: N), (S407: N), (S412: N). Detects the occurrence of abnormalities. The CPU 301 that has detected the occurrence of the abnormality of the contact separation mechanism executes the contact separation mechanism abnormality determination process (S415).

(Attachment separation mechanism abnormality judgment processing)
FIG. 5 is an explanatory diagram of a state when there is an abnormality in the contact separation mechanism. FIG. 5 shows a combination of the output (detection value) of the contact separation position sensor 218, the possibility of contact separation operation, and the toner image formed on the intermediate transfer belt 217 in an abnormal state. FIG. 5 shows the shape of the toner image and the detection result by the toner patch sensor 153 as the toner image. FIG. 6 is a flowchart showing an abnormality determination process of the contact separation mechanism. FIG. 7 is an exemplary view of a display screen displayed on the operation panel 160 during the contact separation mechanism abnormality determination process.

As shown in FIG. 5, there are two types of detection values of the contact separation position sensor 218, "on-fixed" and "off-fixed", for abnormalities in the sensing system. Further, the contact separation mechanism takes two states, "a state in which the contact separation operation is possible" and "a state in which the contact separation operation is impossible", depending on the presence or absence of a mechanical / drive system failure. Therefore, there are four 2 × 2 patterns as cases. Based on these four patterns of abnormal states, the abnormality determination process of the contact separation mechanism will be described. The abnormality determination process determines the faulty part that caused the abnormality of the contact separation mechanism.

In the abnormality determination process of the contact separation mechanism, the CPU 301 first rotates the contact separation motor 323 in the forward direction (S601). The contact separation motor 323 continues to rotate until the determination of the failure location is completed. Next, the CPU 301 rotationally drives the drum motor 322C and the transfer belt motor 321 to form the cyan toner image on the intermediate transfer belt 217 (S602), and executes the cyan image formation preparation (S603). When image formation becomes possible, the CPU 301 irradiates the exposure device 203C with a laser beam at a predetermined maximum output corresponding to the solid image so that a toner image (solid image) having a high image density is formed (S604). ). The output level of the laser beam does not have to be the maximum output, as long as the toner patch sensor 153 can identify an image having a constant gradation. Here, the cyan image is formed by the distance between the photosensitive drum 201C and the primary transfer roller 211C used for forming the cyan image in the separated state, the photosensitive drums 201Y and 201M and the primary transfer rollers 211Y and 211M. This is because it is larger than the distance of.

The cyan toner image formed on the photosensitive drum 201C and transferred onto the intermediate transfer belt 217 is conveyed to the detection position of the toner patch sensor 153 by the rotation of the intermediate transfer belt 217. The CPU 301 detects the toner image for a certain period of time by the toner patch sensor 153 at the timing when the toner image is conveyed to the detection position of the toner patch sensor 153, and saves the detection result in the RAM 303 (S605). When the detection of the toner image is completed, the CPU 301 ends the output of the laser beam from the exposure device 203C (S606) and stops the cyan image formation (S607). The CPU 301 stops the drum motor 322C and the transfer belt motor 321 (S608). After that, the CPU 301 stops the contact separation motor 323 (S609).

The cyan toner image formed on the intermediate transfer belt 217 in this way has a different shape depending on the location where the failure occurs. That is, when the mechanism / drive system operates normally and the contact separation operation is actually performed, the contact separation motor 323 continues to rotate, so that the photosensitive drums 201Y, 201M, 201C and the intermediate transfer belt 217 are separated from each other. , The contact operation and the separation operation are repeated. Therefore, the cyan toner image on the photosensitive drum 201C is repeatedly transferred / non-transferred onto the intermediate transfer belt 217.
The toner image formed on the intermediate transfer belt 217 as a result is No. 5 in FIG. As shown in 1 and 3, a striped pattern is formed in which a portion where the toner image is formed and a portion where the toner image is not formed are repeated. The detection result of the toner patch sensor 153 that detects such a toner image is a repeating pattern in which the output value is high and low. Each of the high and low periods corresponds to the period of contact and the period of separation. The number of times the stripes of the striped pattern are repeated is arbitrary, but it is sufficient that the portion where the toner image is formed and the portion where the toner image is not formed are formed at least once.

If an abnormality occurs in the mechanism / drive system and the contact separation operation cannot be performed normally, the photosensitive drums 201Y, 201M, 201C and the intermediate transfer belt 217 are in contact with each other even if the contact separation motor 323 continues to rotate. Alternatively, it remains separated. In this case, the cyan toner image on the photosensitive drum 201C is either not transferred at all on the intermediate transfer belt 217, or is continuously transferred. That is, the image on the intermediate transfer belt 217 is not an image of a pattern (cycle) corresponding to the period of operation so as to be in the contact state and the period of operation to be in the separated state.
If the toner image is not transferred at all, the No. 5 in FIG. 2 and No. As shown in 4 (lower), no toner image is formed on the intermediate transfer belt 217. Therefore, the detection result of the toner patch sensor 153 is low and the output value is almost constant. When the toner image continues to be transferred, No. 5 in FIG. As shown in 4 (upper row), a toner image is formed on the intermediate transfer belt 217 without interruption. Therefore, the detection result of the toner patch sensor 153 is high and the output value is almost constant.

What is common when an abnormality occurs in the mechanical / drive system is that there is almost no change in the image density in the toner image detected by the toner patch sensor 153, that is, there is almost no change in the output value. Is. Therefore, the presence or absence of an abnormality in the mechanical / drive system can be determined by whether or not the output value of the toner patch sensor 153 changes by a predetermined value or more. If there is no change, it is determined that the mechanism / drive system is out of order. In the present embodiment, when there is a change of 400 levels or more in the detection result (output value) of the toner patch sensor 153, it is considered that there is a change in image density of a predetermined value or more.

From the above, the CPU 301 determines whether or not the output value of the toner patch sensor 153 acquired in the process of S605 has changed by a predetermined value or more (S610). When the output value changes by a predetermined value or more (S610: Y), the CPU 301 determines that the sensing system has failed, not the mechanical / drive system failure (S611). In this case, the CPU 301 displays the screen illustrated in FIG. 7A on the operation panel 160 and ends the process. When the output value of the toner patch sensor 153 does not change by a predetermined value or more (S610: N), the CPU 301 determines that the mechanical / drive system is out of order (S612). In this case, the CPU 301 displays the screen illustrated in FIG. 7B on the operation panel 160 and ends the process. The CPU 301 notifies the user or the operator of the component determined to be a failure by displaying the determination result of the failure portion on the operation panel 160.

The timing for performing the abnormality determination process of the contact separation mechanism is not limited to the time when an abnormality occurs in the detection result of the contact separation position sensor 218. The abnormality determination process of the contact separation mechanism may be started based on the instruction of the user or the operator.

FIG. 8 is an exemplary view of the start screen of the abnormality determination process of the contact separation mechanism displayed on the operation panel 160. The start screen includes a group of buttons for starting the diagnostic operation of the image forming apparatus 100 at a predetermined timing. The user or operator instructs the image forming apparatus 100 to start the diagnostic process by operating a predetermined button from the start screen. The CPU 301 can display the start screen on the operation panel 160 even when no abnormality has occurred. When the button 801 for performing the abnormality determination process of the contact separation mechanism is operated by the operation panel 160, the CPU 301 executes the process of FIG.

As described above, the image forming apparatus 100 of the present embodiment stops its operation when an abnormality of the contact separation mechanism is detected. The abnormality is detected when the contact separation mechanism is operated and the detection result of the contact separation position sensor 218 does not change within a predetermined time. After that, the image forming apparatus 100 puts the photosensitive drum 201C into a state in which the photosensitive drum 201C can form an image in a controlled state in which the contact separating operation is repeated by the contact separating mechanism. The image forming apparatus 100 forms an image so that a toner image having a constant gradation is formed on the intermediate transfer belt 217 for a predetermined time. The toner image formed on the intermediate transfer belt 217 is detected by the toner patch sensor 153.

When the output value, which is the detection result of the toner patch sensor 153, changes by a predetermined value or more, there are a region where the toner image is formed and a region where the toner image is not formed on the intermediate transfer belt 217. Therefore, it is determined that the contact separation itself is performed. In this case, it is determined that the sensing system of the contact separation mechanism is out of order.
If the output value, which is the detection result of the toner patch sensor 153, does not change by a predetermined value or more, it means that the toner image is not formed on the intermediate transfer belt 217, or the toner image is formed all the time. Therefore, it is determined that the contact separation itself is not performed. In this case, it is determined that the mechanism / drive system of the contact separation mechanism is out of order.

The contact separation position sensor 218 is configured to be turned off in the contact state and turned on in the distance state, but the reverse may be true. That is, it suffices if one of the contact state and the separation state can be detected.

As described above, the image forming apparatus 100 of the present embodiment can determine the failure location by performing the abnormality determination process after the abnormality of the contact separation mechanism is detected or at an arbitrary timing. By notifying the determination result, the user or the operator can reduce the time and effort required to identify the faulty part, and the downtime until recovery can be reduced. Moreover, since it is not necessary to increase the number of sensors or the like for identifying the faulty part, the cost does not increase.

Claims (10)

A first image forming means for forming an image on the first image carrier,
A second image forming means for forming an image on the second image carrier,
A transfer body to which the image is transferred from each of the first image carrier and the second image carrier, and
A first transfer means, which is provided at a position facing the first image carrier across the transfer body and transfers an image from the first image carrier to the transfer body.
A second transfer means, which is provided at a position facing the second image carrier with the transfer body interposed therebetween and transfers an image from the second image carrier to the transfer body.
A first detection means for detecting an image formed on the transfer body, and
By moving the first transfer means, there are a contact state in which the first image carrier and the transfer body are in contact with each other and a separated state in which the first image carrier and the transfer body are separated from each other. With a contact separation mechanism that switches to
A second detecting means for detecting that the first transfer means is in one of the contact state and the separated state,
When the second detection means does not detect the one state even if the contact separation mechanism is operated so that the first image carrier and the transfer body are in the one state, the contact state. In each of the state in which the contact separation mechanism is operated so as to be such that the contact separation mechanism is operated and the state in which the contact separation mechanism is operated so as to be in the separation state, the first image supporting body is subjected to the first image forming means. An image is formed, the image formed on the first image carrier by the first transfer means is transferred to the transfer body, and the detection result of the image transferred to the transfer body is obtained by the first detection means. Based on the above, the control means for determining whether the contact separation mechanism is faulty or the second detection means is faulty is provided.
Image forming device. The control means forms an image having a constant gradation on the first image carrier by the first image forming means, and the image formed on the first image carrier by the first transfer means is used as the transfer body. The image is transferred to the transfer body, and the failed portion is determined based on whether or not there is a change of a predetermined value or more in the detection result of the image transferred to the transfer body by the first detection means.
The image forming apparatus according to claim 1. The control means has a pattern corresponding to a period in which the detection result by the first detection means is operated so as to be in the contact state and a period in which the detection result is operated so as to be in the separated state, or is constant. It is characterized in that the location of failure is determined based on whether or not it is.
The image forming apparatus according to claim 1 or 2. The control means repeats the state of operating the contact separation mechanism so as to be in the contact state and the state of operating the contact separation mechanism so as to be in the separation state, and the first image forming means. The image forming apparatus according to any one of claims 1 to 3, wherein an image is formed on the first image carrier. In the control means, when the detection result of the second detection means does not change within a predetermined time after the first transfer means is moved by the contact separation mechanism, an abnormality has occurred in the contact separation mechanism. It is characterized by detecting
The image forming apparatus according to any one of claims 1 to 4. The control means forms an image having a constant gradation on the first image carrier by the first image forming means, and the image formed on the first image carrier by the first transfer means is used as the transfer body. When there is a change of a predetermined value or more in the detection result of the image transferred to the transfer body by the first detection means, it is determined that the second detection means is out of order, and the first detection is performed. It is characterized in that it is determined that the contact separation mechanism has failed when the detection result by the means does not change by a predetermined value or more.
The image forming apparatus according to any one of claims 1 to 5. The control means is said to have a pattern corresponding to a period in which the detection result by the first detection means is operated so as to be in the contact state and a period in which the detection result is operated so as to be in the separated state. 2. It is characterized in that it is determined that the detection means is out of order, and when the detection result by the first detection means is constant, it is determined that the contact separation mechanism is out of order.
The image forming apparatus according to claim 6. The first image forming means forms a chromatic image on the first image carrier, and the first image forming means forms a chromatic image.
The second image forming means forms a black image on the second image carrier, and the second image forming means forms a black image.
When the control means forms a color image, the first image carrier is brought into contact with the transfer body by the contact separation mechanism, and when a monochrome image is formed, the first image is brought into contact with the contact separation mechanism. The carrier and the transfer body are separated from each other.
The image forming apparatus according to any one of claims 1 to 7. A plurality of the first image carriers are provided, and the first image carrier is provided.
A plurality of the first transfer means are provided corresponding to the first image carrier.
When the control means does not detect the one state even if the contact separation mechanism is operated so that the first image carrier and the transfer body are in the one state. An image of the first image carrier having the largest distance from the corresponding first transfer means in the separated state while abutting and separating the first image carrier and the transfer body by the contact separation mechanism. Is formed, and the image formed on the first image carrier is transferred to the transfer body by the first transfer means.
The image forming apparatus according to any one of claims 1 to 8. The control means is characterized in that it notifies a component determined to be a failed portion.
The image forming apparatus according to any one of claims 1 to 9.

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