JP2007272154A - Image forming apparatus and detecting method for pressure-contact/separation state of transfer member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect the pressure-contact/separation state of a transfer member at a low cost without using a photointerrupter. <P>SOLUTION: The image forming apparatus has: a secondary transfer roller 28 which is pressed against an intermediate transfer belt 23 to make the intermediate transfer belt 23 perform transfer and can move between pressure-contact state and separation state of the intermediate transfer belt; a contact/separation driving device SK which drives the secondary transfer roller 28 to move between the pressure contact state and the separation state; an optical sensor 33 which is provided to detect the state of a toner image on the intermediate transfer belt 23 as variation in light reflectivity; and a shutter member 56 which opens and closes an opening part for detection by the sensor 33 and performs the opening/closing operation in synchronism with the moving operation of the secondary transfer roller 28 between the pressure-contact state and the separation state. The image forming apparatus is configured to detect the pressure-contact state or the separation state of the secondary transfer roller 28 on the basis of variation of a detection signal S1 of the sensor 33 accompanying the opening/closing operation of the shutter member 56. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, an MFP, a facsimile, or a composite machine thereof, which employs various image forming methods such as an electrophotographic method, an electrostatic recording method, an ionography, and a magnetic recording method, and The present invention relates to a method for detecting a pressure contact / separation state of a transfer member in an image forming apparatus. The present invention is used, for example, to detect the pressure contact / separation state of the secondary transfer roller to the intermediate transfer belt.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a copier having an electrophotographic process, a printer, a facsimile machine, a multifunction machine, or a multi-function machine called MFP (Multi Function Peripherals), an electrostatic latent image formed on a photosensitive drum is used. The image is developed to form a toner image, the toner image is primarily transferred to an intermediate transfer belt, further transferred to a recording paper, and then fixed to the image to form an image. In order to perform the secondary transfer of the toner image from the intermediate transfer belt to the recording paper, a secondary transfer roller that is in pressure contact with the intermediate transfer belt as an image carrier is provided.

  In such an image forming apparatus, the secondary transfer roller is movable between the pressure contact state and the separation state with respect to the intermediate transfer belt. While it is in a pressure contact state during normal image formation (printing), it is generally in a separated state when image formation is not performed.

  In addition, a toner pattern of each color for test is formed on the intermediate transfer belt under various image forming conditions, and the state of the formed toner pattern is detected by an optical sensor (IDC sensor: Image Density Control Sensor). Generally, the formation conditions are adjusted. Also in this case, in order to prevent the secondary transfer roller and the like from being stained with toner, the secondary transfer roller is generally separated.

  A contact / separation drive device is provided for the movement of the secondary transfer roller. In order to detect whether the contact / separation drive device has switched to the separated state or the pressure contact state, it is conventionally necessary to use a photo A dedicated optical sensor such as an interrupter is used.

  However, if a photo interrupter is used to detect pressure contact / separation, the number of parts increases and the cost increases. On the other hand, a device that uses a photo interrupter for detecting the arrival and passage timing of recording paper as a transfer material for detecting the pressure contact / separation of the secondary transfer roller without using a dedicated photo interrupter is proposed. (Patent Document 1).

On the other hand, in order to prevent the detection surface of the IDC sensor from becoming dirty due to scattering of toner or the like, it has been proposed to provide a shutter plate that covers the detection surface when detection of the IDC sensor is not required (Patent Document 2).
JP 2004-264455 A JP-A-2001-100597

  However, in the apparatus of Patent Document 1 described above, since the detection of the arrival and passage timing of the recording paper and the detection of the pressure contact / separation of the secondary transfer roller are combined with one photo interrupter, the arrival of the recording paper and It is necessary to use a special pre-transfer sensor flag for detecting the passage timing, which may be restricted by the operation of detecting the jam of the recording paper.

  In the apparatus of Patent Document 2, the operation state of the shutter plate is recognized by a change in the signal of the IDC sensor, but a dedicated photo interrupter or the like is used for detecting the pressure contact / separation of the secondary transfer roller. Will be.

  In recent years, there is a high demand for downsizing as well as a cost reduction of the apparatus, and there is a great merit when a dedicated photo interrupter for detecting the pressure contact / separation of the secondary transfer roller can be omitted.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus and a detection method capable of detecting a pressure contact / separation state of a transfer member at a low cost without using a photo interrupter. To do.

  An apparatus according to the present invention is an image forming apparatus configured to transfer a toner image formed in an electrophotographic process from an image carrier to a transfer material, and is in a pressure contact state with the image carrier. A transfer member capable of moving between the pressure contact state and the separation state, causing the transfer to move, a contact / separation drive member for driving the transfer member to move between the pressure contact state and the separation state, and toner on the image carrier Optical detection means provided to detect the state of the image as a change in light reflectance, and opening and closing of the opening for detection of the detection means, and movement between the pressure contact state and the separation state of the transfer member A shutter member whose opening / closing operation is performed in synchronization with the operation, and based on a change in a detection signal of the detection means accompanying the opening / closing operation of the shutter member, Configured to detect interval state.

  Preferably, a surface of the shutter member facing the detection unit has a reflection characteristic different from that of the image carrier with respect to visible light or infrared light.

  Alternatively, the surface of the shutter member facing the detection means has optical characteristics that absorb visible light or infrared light.

  In addition, when a predetermined time has elapsed after the transfer member is driven to move by the contact / separation drive member, a signal indicating an abnormality is output when the detection signal of the detection unit does not change by a predetermined amount or more. Output.

  In addition, when the detection signal of the detection means does not change by a predetermined amount or more even though a predetermined time has elapsed after the transfer member is driven to move by the contact / separation drive member, the contact / separation drive member The transfer member is moved again.

  In the image forming apparatus configured to transfer the toner image formed in the electrophotographic process from the image carrier to the transfer material, the method according to the present invention is performed by pressing the transfer to the image carrier. A method of detecting a pressure contact / separation state of a transfer member for performing an optical detection unit for detecting a state of a toner image on the image carrier as a change in light reflectance, and for detecting the detection unit A shutter member that opens and closes the opening of the transfer member and performs the opening and closing operation in synchronization with the movement operation of the transfer member between the pressure contact state and the separation state, and the detection means detects the opening and closing operation of the shutter member. Based on the signal change, the pressure contact state or the separation state of the transfer member is detected.

  According to the present invention, the pressure contact / separation state of the transfer member can be detected at low cost without using a photo interrupter.

  FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus 1 according to an embodiment of the present invention, FIG. 2 is a diagram illustrating an open / closed state of a shutter 56 of an IDC sensor 33, and FIG. 3 is a configuration of a contact / separation driving device SK. FIG. 4 is a diagram showing a difference in reflectance between the intermediate transfer belt 23 and the shutter 56, and FIG. 5 is a diagram showing an example of a change in the detection signal S1 of the IDC sensor 33 when the pressure contact is normally performed. 6 is a diagram showing an example of a change in the detection signal S1 of the IDC sensor 33 when the pressure contact is not normally performed, and FIG. 7 is a change of the detection signal S1 of the IDC sensor 33 when the separation is normally performed. FIG. 8 is a flowchart showing an operation flow of the image forming apparatus 1.

  In FIG. 1, an image forming apparatus 1 is an electrophotographic digital multi-function peripheral, which has a built-in tandem print engine, forms an image of each color on an intermediate transfer belt 23, and transfers it to a recording paper PA in a batch. Output a full-color image.

  That is, the image output device 1 has Y (yellow), M (magenta), C (cyan), and K (black) image forming units 24Y, M, C, and K arranged in a row in a tandem format. Yes. Each of the image forming units 24Y, 24M, 24C, 24K exposes the surface of the photosensitive drum 41 in accordance with the photosensitive drum 41, the charging charger 42 for uniformly charging the surface of the photosensitive drum 41, and the image data of each color. Thus, the exposure unit 43 that forms an electrostatic latent image, the developing unit 44 that develops the electrostatic latent image with toner of each color to form a toner image, and the photosensitive drums 41 across the intermediate transfer belt 23. The transfer roller 22 disposed at a position, a cleaner 45 that collects and cleans toner remaining on the surface of the photosensitive drum 41, and the like.

  In the present specification and drawings, the symbols corresponding to the colors Y, M, C, and K may be suffixed with the symbols Y, M, C, and K, respectively.

  The intermediate transfer belt 23 is stretched between the rollers 25 and 26 so as to be along the upper portions of the photosensitive drums 42Y, 42M, 42C, and 42K, and travels in the direction of the arrow M1 in FIG. Each of the transfer rollers 22Y, 22M, 22C, and 22K is in contact with the respective photosensitive drums 42Y, 42M, 42C, 42K, and the intermediate transfer belt 23, and the intermediate positions from the respective photosensitive drums 42Y, 42M, 42C, 42K. The transfer belt 23 is movable between a separation position where the transfer belt 23 is separated (also referred to as separation or retraction). As the intermediate transfer belt 23 comes into pressure contact with the photosensitive drums 42Y, 42M, 42C, and 42K, the toner images of the respective colors on the photosensitive drum 42 are sequentially primary-transferred onto the intermediate transfer belt 23 sequentially. As a result, a full-color toner image is formed on the intermediate transfer belt 23 in which toner images of four colors Y, M, C, and K are superimposed.

  The toner image primarily transferred to the intermediate transfer belt 23 is secondarily transferred by the secondary transfer roller 28 onto the recording paper PA that is a transfer material fed from the paper feed cassette 27 toward the nip portion. Thereafter, the recording paper PA is fixed by the fixing unit 29 and discharged to the paper discharge tray 30. The secondary transfer roller 28 is driven to move by contact / separation driving devices (contact / separation mechanisms) of various types or configurations, and the position of the secondary transfer roller 28 is switched between the pressure contact state and the separation state with respect to the intermediate transfer belt 23. A belt cleaner and a waste toner box 32 are provided in the vicinity of the roller 26.

  In the vicinity of the roller 25, an optical IDC sensor (Image Density Control Sensor) 33, which is a detecting means for detecting the density of the toner image on the intermediate transfer belt 23, is provided. The IDC sensor 33 detects the state of the toner image on the intermediate transfer belt 23 as a change in light reflectance. That is, the IDC sensor 33 irradiates light from the opening toward the surface of the intermediate transfer belt 23, and detects the amount of light reflected and returned to the opening. It is also possible to control the light emission amount of the IDC sensor 33. Further, the light emitting portion may be a projector that is separate from the IDC sensor 33.

  When the density of the toner image on the intermediate transfer belt 23 is low, that is, when the toner adhesion amount is small, a large amount of light reflected by the intermediate transfer belt 23 returns to increase the amount of light, and when the density of the toner image is high, that is, the toner. When the amount of adhesion is large, the light is blocked by the toner and the amount of reflected light decreases. The IDC sensor 33 outputs a detection signal S1 corresponding to the amount of reflected light. That is, for example, when the amount of reflected light is large, the voltage value of the detection signal S1 increases, and when the amount of reflected light is small, the voltage value of the detection signal S1 decreases.

  In this way, the IDC sensor 33 detects the state of the surface of the intermediate transfer belt 23. Depending on the density of the toner image detected by the IDC sensor 33, image adjustment is performed by controlling the amount of light by the exposure unit 43, controlling the charging voltage, controlling the developing conditions in the developing unit 44, and the like. Such a series of operations for image adjustment is an image stabilization operation. Actually, Y, M, C, and K toner patterns (toner patches) for image adjustment with different image forming conditions are formed, and the density thereof is detected by the IDC sensor 33.

  In the present embodiment, the IDC sensor 33 is provided at a position upstream of the secondary transfer roller 28 with respect to the traveling direction of the intermediate transfer belt 23 with the detection surface facing the intermediate transfer belt 23.

  The IDC sensor 33 is provided with a shutter 56 for opening and closing the opening of the detection surface. The shutter 56 is for preventing toner powder scattered from the intermediate transfer belt 23 and the like from adhering to the surface of the IDC sensor 33 and becoming dirty. When the IDC sensor 33 does not detect the toner pattern, the shutter 56 is used. It is inserted between the opening 33 and the intermediate transfer belt 23 to close the opening.

  The shutter 56 is opened and closed in synchronization with the movement of the secondary transfer roller 28 between the pressed state and the separated state, that is, in conjunction with the movement. In the present embodiment, the shutter 56 is opened when the secondary transfer roller 28 is separated, and the shutter 56 is closed when the secondary transfer roller 28 is pressed. This will be described in detail later.

  In the drawing, one IDC sensor 33 is shown, but two or more IDC sensors 33 may be provided. Various positions or methods other than those described here can also be adopted as the attachment position and attachment method of the IDC sensor 33.

  The control unit 21 includes a CPU 2, a memory, a control circuit, a communication interface, a magnetic storage device, and the like. The control unit 21 receives image data read by the document reading device 35 or image data output from a personal computer (not shown). While performing image processing, it controls the operation of each part of the image forming apparatus 1. In the following, in particular, the control and detection of the pressure contact and separation of the secondary transfer roller 28 from the intermediate transfer belt 23 by the control unit 21 and the contact separation determination control therefor will be described in detail. The contact / separation determination control includes pressure contact determination control for determining normality / abnormality of pressure contact and separation determination control for determining normal / abnormality of distance.

  Note that the image forming means or the image forming method, the configuration or structure of each part in the image forming apparatus 1 are not limited to the examples described above. Further, the image forming apparatus 1 may be a color or monochrome copying machine, a printer, a facsimile, or a complex machine thereof.

  Next, the shutter 56 and its opening / closing operation will be described.

  2A shows a state where the shutter 56 is closed, and FIG. 2B shows a state where the shutter 56 is opened.

  2A and 2B, the IDC sensor 33 is provided inside an appropriate casing 37 attached to one end on the back side of the conveyance guide member 36 of the recording paper PA. An opening 37a is provided in the casing 37, and light emitted upward from the IDC sensor 33 in the drawing irradiates the surface of the intermediate transfer belt 23 through the opening 37a, and this is reflected and is similarly opened. And return to the IDC sensor 33. The casing 37 is made of a metal material or synthetic resin, and an appropriate surface treatment is applied to the surface as necessary.

  The shutter 56 is held in a part of the contact / separation driving device SK, and moves in conjunction with the movement of the secondary transfer roller 28, so that the opening of the IDC sensor 33, that is, the opening 37a of the casing 37 in the example shown in FIG. Open and close. When the secondary transfer roller 28 is pressed, the shutter 56 is closed as shown in FIG. 2A, and when the secondary transfer roller 28 is separated, the shutter 56 is opened as shown in FIG. 2B.

  Normally, when the image forming operation is performed, the secondary transfer roller 28 is in a pressure contact state, and when the image stabilization operation by the IDC sensor 33 is performed, the secondary transfer roller 28 is in a separated state. Note that the shutter 56 does not necessarily have to be directly held by a part of the contact / separation driving device SK, and may be provided with a mechanism that opens and closes in conjunction with the pressure contact / separation operation.

  In the shutter 56, the surface on the side facing the IDC sensor 33, that is, the back surface of the shutter 56 has a reflection characteristic different from that of the intermediate transfer belt 23 with respect to visible light or infrared light.

  That is, for example, as shown in FIG. 4, the surface of the secondary transfer roller 28 has a reflectance characteristic CH1 of about 10 to 5% with respect to a wavelength (about 400 to 900 nm) from visible light to infrared light. On the other hand, the back surface of the shutter 56 has a reflectance characteristic CH2 of about 2%. Accordingly, a level difference occurs in the detection signal S1 between when the shutter 56 is opened and the front surface of the secondary transfer roller 28 is detected and when the shutter 56 is closed and the back surface is detected. The pressure contact / separation state of the secondary transfer roller 28 is detected using the level difference of the detection signal S1.

  In order to reduce the reflectance of the back surface of the shutter 56, a material having such characteristics is used as the material of the shutter 56, or surface treatment with such characteristics is performed, or a pattern having such characteristics is formed. For example, various methods can be adopted. Further, the rear surface of the shutter 56 may have optical characteristics that absorb visible light or infrared light. When the surface treatment is performed on the shutter 56, a synthetic resin or a metal material can be used as the material of the shutter 56 itself.

  Here, an example of the contact / separation driving device SK will be described.

  As shown in FIG. 3, the contact / separation driving device SK includes a holder 51 and a slider 52 that is movably held by the holder 51. The slider 52 supports the rotation shaft of the secondary transfer roller 28 and slides with respect to the holder 51 to move the secondary transfer roller 28 between the separation position (state shown in FIG. 3) and the pressure contact position. Support as possible. The holder 51 is provided with a spring 53, and the slider 52 is urged toward the press contact position by the spring 53.

  In order to return the secondary transfer roller 28 to the separated position, a lever 54 that can be rotated around an axis whose positional relationship is determined with respect to the holder 51 and a cam 55 that is rotated by a motor (not shown) are provided. The lever 54 has a slot provided in one arm 54a engaged with the protrusion of the slider 52, and the other arm 54b is pressed against the rotating cam 55, thereby rotating the lever 54. To do.

  In the state shown in FIG. 3, the arm 54 b is pushed by the cam 55, whereby the lever 54 rotates clockwise to move the slider 52 against the urging force of the spring 53, thereby the secondary transfer roller. 28 is a separation position. When the cam 55 rotates and the arm 54b becomes free, the secondary transfer roller 28 is pushed by the urging force of the spring 53 and is brought into a pressure contact position.

  Although not shown in FIG. 3, the shutter 56 is connected to, for example, the lever 54, and is configured to move in the left-right direction in the drawing along with the rotation of the lever 54. The operation and the opening / closing operation of the shutter 56 are performed in synchronization. The configuration of the contact / separation driving device SK and the opening / closing mechanism of the shutter 56 are not limited to those described here. The shutter 56 and a mechanism for interlocking this with the contact / separation driving device SK and the like correspond to the shutter member in the present invention.

  Next, the contact / separation determination control (contact / separation detection operation) of the secondary transfer roller 28 by the IDC sensor 33 will be described.

  In FIG. 5, time is taken on the horizontal axis, and the level (voltage V) of the detection signal S1 of the IDC sensor 33 is shown on the vertical axis.

  In the image forming apparatus 1 of the present embodiment, the secondary transfer roller 28 is in a separated state during standby, and therefore the shutter 56 is in an open state. When an image stabilization execution request is made in this state, the secondary transfer roller 28 and the shutter 56 are left as they are, and the process proceeds to an image stabilization operation. However, when a print execution request is made in this state, the contact / separation driving device SK is driven to transfer the toner image formed on the intermediate transfer belt 23 onto the recording paper PA, and the secondary transfer roller 28 is driven. Is in a pressure contact state. In accordance with this, pressure determination control for determining whether or not the secondary transfer roller 28 is in pressure contact is performed.

  In the pressure determination control, the IDC sensor 33 is caused to emit light when the shutter 56 is in the open state, and the reflected light is received to monitor the detection signal S1. Note that the light emission amount of the IDC sensor 33 at this time is the light emission amount set by the image stabilization operation.

  Then, since the shutter 56 shifts from the open state to the closed state with the IDC sensor 33 emitting light, a change in the amount of reflected light during this period appears in the detection signal S1.

  That is, for example, as shown in FIG. 5, when the secondary transfer roller 28 is separated, that is, when the shutter 56 is open, the detection signal S1 is about 4.3 volts, and the secondary transfer roller 28 is in a pressure contact state at time t1. That is, when the shutter 56 is switched to the closed state, the detection signal S1 drops to about 0.2 volts. A change in the voltage of the detection signal S1 is detected, and it is determined whether or not the switching to the pressure contact state has been normally performed.

  In FIG. 5, when the threshold value Th1 is set to about 2.4 volts and the voltage of the detection signal S1 changes beyond the threshold value Th1, it is determined that the contact / separation state has been switched normally. . Accordingly, in this example, since the detection signal S1 has changed from about 4.3 volts to about 0.2 volts, it is determined that the pressure contact state has been normally switched. Therefore, after that, an image forming operation (printing operation) is performed.

  If the detection signal S1 does not fall below the threshold value Th1 even after a predetermined time has elapsed even though the contact / separation driving device SK is driven and switched to the pressure contact state, the secondary transfer roller 28 Is determined not to be in a normal pressure contact state. In that case, without making a transition to the image forming operation, a signal indicating an abnormality is output, for example, an abnormal end notification is performed. Alternatively, it is determined that the contact / separation operation has not been completed, and the contact / separation driving device SK is driven again, and the movement of the secondary transfer roller 28 is repeated. If the detection signal S1 becomes lower than the threshold value Th after trials within the set number of times, it is determined that the press contact operation is completed and the process proceeds to an image forming operation.

  Further, as shown in FIG. 6, even if the voltage of the detection signal S1 becomes equal to or lower than the threshold value Th1 after the transition to the pressure contact state, if the threshold value Th1 is not exceeded in the previous separated state, it is also abnormal. Treat as there is.

  When the image forming operation is finished, the contact / separation driving device SK is driven to change the secondary transfer roller 28 from the pressure contact state to the separation state, contrary to the above. In this case, since the shutter 56 is shifted from the closed state to the open state while the IDC sensor 33 emits light, a change in the amount of reflected light during this time appears in the detection signal S1 as well.

  That is, for example, as shown in FIG. 7, when the secondary transfer roller 28 is in a pressure contact state, that is, the shutter 56 is closed, the detection signal S1 is about 0.2 volts, and the secondary transfer roller 28 is separated at time t3. That is, when the shutter 56 is switched to the open state, the detection signal S1 rises to about 4.3 volts. A change in the voltage of the detection signal S1 is detected, and it is determined whether or not the switch is normally switched to the separated state.

  After confirming that the secondary transfer roller 28 is normally switched to the separated state, the image forming operation is completed.

  If the detection signal S1 does not rise above the threshold Th1 even though the contact / separation driving device SK is driven and switched to the separated state, the secondary transfer roller 28 is normally separated. Judge that there is no. In that case, an abnormal termination notification is made. Alternatively, retry the contact / separation operation. Further, even if the voltage of the detection signal S1 becomes equal to or higher than the threshold value Th1 after shifting to the separated state, if it is not lower than the threshold value Th1 in the previous pressure contact state, it is also processed as abnormal.

  In the contact / separation determination control described above, it is determined whether the detection signal S1 is normal or abnormal depending on whether the voltage of the detection signal S1 has changed beyond the threshold value Th1, but instead of this, At the same time, determination may be made based on whether or not the amount of change in the voltage of the detection signal S1 is equal to or greater than a set amount. That is, a threshold Th2 is set for the amount of change in the voltage of the detection signal S1, and the change in the voltage of the detection signal S1 is greater than or equal to the threshold Th2 before and after switching of the contact / separation state by the contact / separation driving device SK. Is determined to be normal.

  In order to obtain the voltage value of the detection signal S1, for example, the detection signal S1 is converted into digital data by an AD converter and stored in a memory. At this time, data is stored for the detection signal S1 only once at a predetermined timing, multiple times at predetermined intervals, or multiple times at predetermined timing. Further, average value data in a predetermined period may be stored.

  As described above, according to the contact / separation determination control of the present embodiment, it is possible to reliably and accurately determine the pressure contact state and the separation state of the secondary transfer roller 28 using the detection signal S1 of the IDC sensor 33 for IDC. Can do. Since a dedicated photo interrupter is not used as in the prior art, the configuration is simple and the cost is reduced accordingly.

  Next, contact / separation determination control will be described with reference to a flowchart.

  In FIG. 8, when the secondary transfer roller 28 is in the separated state and the shutter 56 is open (# 11), and there is a request for the image stabilization operation (Yes in # 12), the image stabilization operation is performed. Control is performed (# 13). If there is no request for an image stabilization operation (No in # 12) and there is a request for an image forming operation (Yes in # 14), first, the IDC sensor 33 is caused to emit light (# 15). The voltage value V1 of the detection signal S1 of the IDC sensor 33 is acquired (# 16). The secondary transfer roller 28 is brought into a pressure contact state, and the shutter 56 is closed (# 17). The voltage value V2 of the detection signal S1 of the IDC sensor 33 is acquired (# 18). During this time, it is determined whether or not the detection signal S1 of the IDC sensor 33 has changed by a predetermined value or more (# 19).

  If yes in step # 19, it is determined that the pressure contact has been normally performed (# 20), and image formation is executed (# 21). When the image formation is completed (Yes in # 22), the IDC sensor 33 is caused to emit light (# 23), and the voltage value V2 of the detection signal S1 of the IDC sensor 33 is acquired (# 24). The secondary transfer roller 28 is separated and the shutter 56 is opened (# 25). The voltage value V1 of the detection signal S1 of the IDC sensor 33 is acquired (# 26). During this time, it is determined whether or not the detection signal S1 of the IDC sensor 33 has changed by a predetermined value or more (# 27).

  If yes in step # 27, it is determined that the separation has been performed normally (# 28), and if no in step # 27, it is determined that the separation is abnormal (# 29). If no in step # 19, it is determined that there is a pressure contact abnormality (# 30). Depending on the contents of each determination, a signal indicating that is output and control corresponding to that is performed, or that effect is displayed on the operation panel or the like.

  In the embodiment described above, the predetermined time from the driving by the contact / separation driving device SK until the output of the signal indicating abnormality is an appropriate time, for example, the time required for the shutter 56 to actually move, the IDC sensor What is necessary is just to set in consideration of the time required for performing the process by 33.

  An image carrier other than the intermediate transfer belt 23 may be used, and a transfer member other than the secondary transfer roller 28 may be used. In addition, the configuration, structure, shape, dimensions, number, material of the whole or each part of the intermediate transfer belt 23, the secondary transfer roller 28, the IDC sensor 33, the casing 37, the shutter 56, the contact / separation driving device SK, or the image forming apparatus 1. The contents, order, timing, and the like of the processing can be appropriately changed in accordance with the spirit of the present invention.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. It is a figure explaining the opening-and-closing state of the shutter of an IDC sensor. It is a figure which shows the example of a structure of a contact / separation drive device. It is a figure which shows the difference in the reflectance of an intermediate transfer belt and a shutter. It is a figure which shows the example of the change of the detection signal of an IDC sensor in the case of normal pressure welding. It is a figure which shows the example of the change of the detection signal of an IDC sensor in case pressure welding is not normal. It is a figure which shows the example of the change of the detection signal of an IDC sensor in the case of normal separation. 3 is a flowchart illustrating an operation flow of the image forming apparatus.

Explanation of symbols

1 Image forming apparatus 23 Intermediate transfer belt (image carrier)
28 Secondary transfer roller (transfer member)
33 IDC sensor (detection means)
37a Opening 56 Shutter (shutter member)
SK Contact / separation drive device (contact / separation drive member)
S1 detection signal

Claims (6)

An image forming apparatus configured to transfer a toner image formed in an electrophotographic process from an image carrier to a transfer material,
A transfer member capable of moving between the pressed state and the separated state while performing the transfer by being in a pressed state with respect to the image carrier;
A contact / separation drive member for moving and driving the transfer member between a pressure contact state and a separation state;
Optical detection means provided to detect the state of the toner image on the image carrier as a change in light reflectance;
A shutter member that opens and closes an opening for detection of the detection means and performs the opening and closing operation in synchronization with the movement operation of the pressure contact state and the separation state of the transfer member,
A pressure contact state or a separation state of the transfer member is detected on the basis of a change in a detection signal of the detection means accompanying the opening / closing operation of the shutter member;
An image forming apparatus. The surface of the shutter member facing the detection means has a reflection characteristic different from that of the image carrier with respect to visible light or infrared light.
The image forming apparatus according to claim 1. The surface of the shutter member facing the detection means has an optical characteristic of absorbing visible light or infrared light.
The image forming apparatus according to claim 1. Outputs a signal indicating an abnormality when the detection signal of the detection means does not change more than a predetermined amount even though a predetermined time has elapsed after the transfer member is driven to move by the contact / separation drive member. ,
The image forming apparatus according to claim 1. The transfer member is moved by the contact / separation drive member when the detection signal of the detection means does not change by a predetermined amount or more even though a predetermined time has elapsed after the transfer member is driven to move by the contact / separation drive member. Drive again,
The image forming apparatus according to claim 1. In an image forming apparatus configured to transfer a toner image formed in an electrophotographic process from an image carrier to a transfer material, the transfer member is pressed against the image carrier when the transfer is performed. A method for detecting a separation state,
Optical detection means for detecting the state of the toner image on the image carrier as a change in light reflectance, and opening and closing an opening for detection of the detection means, and the pressure contact state and the separation state of the transfer member A shutter member that opens and closes in synchronization with the moving operation is provided,
Detecting a pressure contact state or a separation state of the transfer member based on a change in a detection signal of the detection means accompanying the opening / closing operation of the shutter member;
A method for detecting a pressure contact / separation state of a transfer member in an image forming apparatus.