JP2007272158A - Image forming apparatus and method for detecting pressurized contact/distancing state of transfer member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect the pressurized contact/distancing state of a transfer member inexpensively without using a photointerrupter. <P>SOLUTION: The image forming apparatus has a secondary transfer roller 28 which is brought into pressurized contact with an intermediate transfer belt 23 to make the intermediate transfer belt 23 perform transfer and can move between a pressurized contact state and a distancing state with respect to the intermediate transfer belt, a contacting/distancing driving device SK which drives the secondary transfer roller 28 to move between the pressurized contact state and the distancing state, and an optical detecting means 33 which is provided to detect the state of a toner image on the intermediate transfer belt 23 in the form of variation in quantity of light transmitting the intermediate transfer belt. The image forming apparatus is configured to detect variation in the toner image on the intermediate transfer belt 23 due to the pressurized contact of the secondary transfer roller 28 against the intermediate transfer belt 23 by the detecting means 33 and then based upon variation in the detection signal S1, detects the pressurized contact state and the distancing state of the secondary transfer roller 28. <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 checking 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 accordingly, resulting in an increase in cost. 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).
JP 2004-264455 A

  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 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.

  The present invention has been made in view of the above-described problems, and provides an image forming apparatus and a detection method capable of detecting the pressure contact / separation state of a transfer member at a low cost without using a dedicated photo interrupter. Objective.

  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 An optical detection means provided to detect the state of the image as a change in the amount of light transmitted through the image carrier, and the upper surface of the image carrier by pressing the transfer member against the image carrier. The change in the toner image is detected by the detection means, and the pressure contact state or the separation state of the transfer member is detected based on the change in the detection signal.

  Preferably, the image carrier is an intermediate transfer belt, and the detecting means is provided with a light emitting portion and a light receiving portion sandwiching the intermediate transfer belt on the downstream side of the transfer member.

  In addition, when the change of the toner image is detected by the detection unit, the toner of the toner image is electrostatically attracted to the transfer member by applying a bias voltage having a polarity opposite to the charge of the toner to the transfer member. .

  In addition, after the detection of the change in the toner image by the detecting means, a bias voltage having the same polarity as the charge of the toner is applied to the transfer member, so that the toner adhering to the transfer member is electrostatically applied to the transfer member. The transfer member is cleaned by suction.

  In addition, a signal indicating an abnormality is output when a 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. To do.

  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 moved and driven by the contact / separation drive member, the contact / separation drive member performs the transfer. The member is driven again.

  Another type of apparatus 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 the state of the toner image on the image carrier is optically displayed. The optical detection means provided to detect the change in reflectance and the image bearing member are brought into a pressure contact state to cause the transfer and move between the pressure contact state and the separated state. A transfer member; and a contact / separation drive member that drives the transfer member to move between a pressure contact state and a separation state, and the detection means moves the transfer member by the contact / separation drive device. The transfer member is mounted such that its position relative to the body changes, and the pressure state or separation state of the transfer member based on the change in the detection signal when the state of the surface of the image carrier is detected by the detection means Configured to detect.

  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. An optical detection means for detecting the state of the toner image on the image carrier as a change in the amount of light transmitted through the front and back of the image carrier. The detection is performed by the means, and the pressure contact state or the separation state of the transfer member is detected based on the change in the detection signal.

  In another form of the method, an optical detection means for detecting the state of the toner image on the image carrier as a change in light reflectance may be provided as the transfer member is moved by the contact / separation driving device. It is attached so that the position with respect to the image carrier changes, and the pressure contact state or the separation state of the transfer member is detected based on the change of the detection signal when the surface state of the image carrier is detected by the detection means. .

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

[First Embodiment]
1 is a diagram showing a schematic configuration of an image forming apparatus 1 according to the first embodiment of the present invention, FIG. 2 is a diagram showing the vicinity of a secondary transfer unit, and FIG. 3 is an example of a configuration of a contact / separation driving device SK. FIG. 4 is a diagram showing an example of the relationship between the toner adhesion amount and the detection signal S1 of the IDC sensor 33, FIG. 5 is a diagram showing an example of a toner pattern, and FIG. 6 is a diagram in the case where pressure contact is normally performed. FIG. 7 is a diagram showing an example of a change in the detection signal S1 of the IDC sensor 33, FIG. 7 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. FIG. 9 and FIG. 10 are flowcharts showing the flow of operations of the image forming apparatus 1. FIG. 9 and FIG.

  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.

  In the first embodiment, the intermediate transfer belt 23 is made of a material that can transmit visible light or infrared light.

  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.

  In addition, a voltage having the same polarity as or opposite to the charge of the toner is selectively applied to the secondary transfer roller 28 in order to control the movement of the toner. This will be described in detail later. A belt cleaner and a waste toner box 32 are provided in the vicinity of the roller 26.

  On the downstream side of the roller 25 and the secondary transfer roller 28, 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 is arranged such that the light emitting portion and the light receiving portion sandwich the intermediate transfer belt 23. Accordingly, the IDC sensor 33 detects the state of the toner image on the intermediate transfer belt 23 as a change in light transmittance by detecting the amount of light that passes through the intermediate transfer belt 23 (transmitted light amount).

  That is, the IDC sensor 33 emits light toward one surface of the intermediate transfer belt 23 by the light emitting portion, transmits the toner image, and transmits the other surface (back surface) of the intermediate transfer belt 23. Is detected. Since the light transmittance of the intermediate transfer belt 23 itself and thus the amount of transmission is constant, the detection signal S1 of the IDC sensor 33 changes according to the density of the toner image.

  Note that the light emission amount of the IDC sensor 33 can also be controlled. Further, the IDC sensor 33 may be a light emitting unit and a light receiving unit that are integrated or separated.

  When the toner image density on the intermediate transfer belt 23 is low, that is, when the toner adhesion amount is small, the amount of transmitted light increases. When the toner image density is high, that is, when the toner adhesion amount is large, the transmitted light amount decreases. . The IDC sensor 33 outputs a detection signal S1 corresponding to the transmitted light amount. That is, for example, when the amount of transmitted light is large, the voltage value of the detection signal S1 increases, and when the amount of transmitted 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 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, control for the secondary transfer roller 28 will be described.

  As shown in FIG. 2, a bias application device 38 for applying a positive or negative bias voltage to the secondary transfer roller 28 is provided.

  That is, the bias applying device 38 includes a positive voltage source 38a, a negative voltage source 38b, and a switching contact 38c. By switching the switching contact 38 c by the control unit 21, a positive or negative bias voltage, that is, a bias voltage having the same polarity or opposite polarity as the charge of the toner is applied to the secondary transfer roller 28.

  In the contact / separation determination control, when the contact / separation state (pressure contact state or separation state) of the secondary transfer roller 28 is detected by the IDC sensor 33, a bias voltage having a polarity opposite to the charge of the toner is applied. The next transfer roller 28 is attracted electrostatically to promote its adhesion. When cleaning the toner adhering to the secondary transfer roller 28 after the detection of the contact / separation state, a bias voltage having the same polarity as the charge of the toner is applied, whereby the toner on the secondary transfer roller 28 is transferred to the intermediate transfer belt. The toner adhering to the secondary transfer roller 28 is removed by electrostatic suction.

  The bias applying device 38 applies a bias voltage for the secondary transfer to the secondary transfer roller 28 when the toner image is secondarily transferred from the intermediate transfer belt 23 to the recording paper PA in the image forming operation. Is possible. As such a bias applying device 38 itself, a device having a known structure or circuit can be used.

  The IDC sensor 33 detects the transmitted light amount of the toner image in the image stabilization operation and in the contact / separation determination control in the image stabilization operation and the image forming operation, and the result is used for various controls. 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. The IDC sensor 33 may also serve as a registration sensor.

  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.

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

  As shown in FIG. 4, the IDC sensor 33 has a sensitivity characteristic that the voltage of the detection signal S <b> 1 decreases as the toner adhesion amount increases, that is, as the amount of the intermediate transfer belt 23 hidden by the toner increases. . Using this sensitivity characteristic, the toner adhesion amount is detected.

  In the contact / separation determination control, a toner pattern, which is a check toner image, is formed on the intermediate transfer belt 23. As shown in FIG. 5, the toner pattern TP has a width that can be detected by the IDC sensor 33 and has a long belt shape along the traveling direction of the intermediate transfer belt 23. Such a toner pattern TP is formed on the intermediate transfer belt 23 so as to pass the detection position KT by the IDC sensor 33. The toner pattern TP is not limited to this example, and toner patterns TP of various shapes or colors can be used.

  In the contact / separation determination control, the toner pattern TP formed on the intermediate transfer belt 23 is passed through the secondary transfer position, and if the secondary transfer roller 28 is in a pressure contact state at that time, the toner is transferred to the secondary transfer roller 28. Since the density of the toner pattern TP decreases due to adhesion to the toner, the IDC sensor 33 detects this.

  That is, the toner pattern TP is formed by the image forming unit 24 and is primarily transferred to the intermediate transfer belt 23, and the toner pattern TP on the intermediate transfer belt 23 is passed through the secondary transfer position in a state where the IDC sensor 33 emits light. After the leading end of the toner pattern TP has passed, the contact / separation driving device SK is driven to move and drive the secondary transfer roller 28, thereby bringing the secondary transfer roller 28 into a pressure contact state or a separation state. Then, the density of the toner pattern TP changes before and after the position where the contact / separation state of the secondary transfer roller 28 is switched. However, the density of the toner pattern TP does not change when the secondary transfer roller 28 is not actually switched despite driving the contact / separation driving device SK. By detecting whether the density of the toner pattern TP has changed by the IDC sensor 33, it is determined whether the contact / separation state of the secondary transfer roller 28 has been normally switched by the contact / separation driving device SK. .

  In FIG. 6, 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. The reason for this is as follows. That is, a nip (width) is usually formed in the secondary transfer portion in order to stabilize the transfer function. Therefore, there is a pressure contact force between the intermediate transfer belt 23 and the secondary transfer roller 28. If the pressing force is applied for a long time, creep may occur on the intermediate transfer belt 23 and the like, and image noise (image unevenness) may occur. Accordingly, the secondary transfer roller 28 is set in a separated state during standby. In image stabilization control, it is common to perform control by forming a check or test toner pattern on the intermediate transfer belt 23. In this case, if the secondary transfer portion is not separated, the secondary transfer roller 28 is contaminated with toner. If the secondary transfer roller 28 becomes dirty, the recording paper PA becomes dirty during the next image forming operation.

  When there is an image stabilization execution request in the standby state, the secondary transfer roller 28 proceeds to an image stabilization operation with the state unchanged. 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.

  That is, in the pressure contact determination control, first, the IDC sensor 33 is caused to emit light, and the detection signal S1 based on the transmitted light amount is monitored. 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.

  A toner pattern TP is formed on the intermediate transfer belt 23 in a state where the IDC sensor 33 emits light, and the secondary transfer roller 28 is brought into pressure contact after the leading end of the formed toner pattern TP passes the secondary transfer position. When the pressure contact of the secondary transfer roller 28 is normally performed, the density of the toner pattern TP is thereby lowered. When this change in density is detected, it is determined that the pressure is normal, and when it is not detected, it is determined that the pressure is abnormal.

  For example, as shown in FIG. 6, the tip of the toner pattern TP passes while the secondary transfer roller 28 is separated, and the IDC sensor 33 detects the density of that portion. In this case, the detection signal S1 is about 0.2 volts. When the secondary transfer roller 28 is switched to the pressure contact state at time t1, the detection signal S1 becomes about 2.2 volts. Further, after the toner pattern TP has passed, the density of the bare surface of the intermediate transfer belt 23 is detected, and the detection signal S1 rises to about 4.3 volts. The threshold value Th1 is set to about 1.2 volts, and since the voltage of the detection signal S1 has changed beyond the threshold value Th1 in the middle of the toner pattern TP, it is determined that the pressure contact state has been switched to normal. .

  That is, when the toner pattern TP passes while the secondary transfer roller 28 is separated, the toner pattern TP is not transferred to the secondary transfer roller 28, so that the high-density toner pattern TP remains as it is and the detection signal S1 is low. Voltage. On the other hand, when the toner pattern TP passes while the secondary transfer roller 28 is in a pressure contact state, the toner pattern TP passes while being transferred to the secondary transfer roller 28, so the density of the toner pattern TP decreases, The voltage of the detection signal S1 increases. In this way, when the pressure contact or separation is normally performed, the voltage of the detection signal S1 changes by a predetermined amount or more before and after that.

  In order to facilitate the transfer of the toner pattern TP to the secondary transfer roller 28, a bias voltage having a polarity opposite to the charge of the toner is applied to the secondary transfer roller 28. As a result, the change in the density of the toner pattern TP appears more remarkably, the detection sensitivity of the IDC sensor 33 is increased, and a more accurate determination can be performed.

  If, as shown in FIG. 7, the detection signal S1 does not exceed 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. Determines that the secondary transfer roller 28 is not 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 higher than the threshold value Th after trials within the set number of times, it is determined that the press-contact operation has been completed.

  After it is determined that the pressure contact is normal in the pressure contact determination control, the cleaning operation of the secondary transfer roller 28 is performed. In the cleaning operation, after the toner pattern TP passes through the secondary transfer roller 28, a bias voltage having the same polarity as the toner charge is applied to the secondary transfer roller 28 by the bias applying device 38. As a result, the toner adhering to the secondary transfer roller 28 is repelled by the bias voltage and transferred to the intermediate transfer belt 23, and the toner adhering to the secondary transfer roller 28 is removed. After performing the cleaning operation, the process proceeds to an image forming operation (printing operation).

  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, separation determination control is performed.

  That is, the toner pattern TP is formed on the intermediate transfer belt 23 with the IDC sensor 33 emitting light. In this embodiment, the toner pattern TP in this case is set to the same toner pattern TP as that in the pressure contact determination control. After the leading end portion of the formed toner pattern TP passes the secondary transfer position, the secondary transfer roller 28 is separated. When the separation of the secondary transfer roller 28 is normally performed, the density of the toner pattern TP so far increases and returns to the original state. When this change is detected, it is determined that the separation is normal, and when it is not detected, it is determined that the separation is abnormal.

  That is, for example, as shown in FIG. 8, the tip of the toner pattern TP passes while the secondary transfer roller 28 is in a pressure contact state, and the IDC sensor 33 detects the density of that portion. In this case, the detection signal S1 is about 2.2 volts. When the secondary transfer roller 28 is switched to the separated state at time t3, the detection signal S1 becomes about 0.2 volts. In addition, after the toner pattern TP has passed, the detection signal S1 rises to about 4.3 volts. The threshold value Th1 is set to about 1.2 volts, and since the voltage of the detection signal S1 has changed beyond the threshold value Th1 in the middle of the toner pattern TP, it is determined that the threshold value Th1 has 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 fall below 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.

  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.

  9 and 10, when there is a request for the image stabilization operation (Yes in # 11), control is performed so as to perform the image stabilization operation (# 12). If there is no request for the image stabilization operation (No in # 11), the secondary transfer roller 28 is set in the separated state (# 13). If there is a request for the image forming operation (Yes in # 14), first, The IDC sensor 33 is caused to emit light (# 15). The toner pattern TP is formed (# 16), and the voltage value V1 of the detection signal S1 of the IDC sensor 33 is acquired (# 17). The secondary transfer roller 28 is brought into a pressure contact state (# 18). The voltage value V2 of the detection signal S1 of the IDC sensor 33 is acquired (# 19). 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 (# 20).

  If YES in step # 20, it is determined that the pressure contact has been normally performed (# 21), and after the secondary transfer roller 28 is cleaned (# 22), image formation is performed (# 23). When the image formation is completed (Yes in # 24), the IDC sensor 33 is caused to emit light (# 25), the toner pattern TP is formed (# 26), and the voltage value V2 of the detection signal S1 of the IDC sensor 33 is acquired (#). 27). The secondary transfer roller 28 is separated (# 28). The voltage value V1 of the detection signal S1 of the IDC sensor 33 is acquired (# 29). 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 (# 30).

  If yes in step # 30, it is determined that the separation has been performed normally (# 31), and if no in step # 30, it is determined that the separation is abnormal (# 32). If no in step # 20, it is determined that there is a pressure contact abnormality (# 33). 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 drive by the contact / separation drive device SK to the output of the abnormal signal is an appropriate time, for example, the toner pattern TP moves to the position of the IDC sensor 33. The time required may be set in consideration of the time required for processing the detection signal S1 of the IDC sensor 33.
[Second Embodiment]
11 is a diagram showing a schematic configuration of an image forming apparatus 1B according to the second embodiment of the present invention, FIG. 12 is a diagram showing the vicinity of the secondary transfer unit, and FIG. 13 is a diagram showing distance characteristics of the IDC sensor 33B. FIG. 14 is a diagram showing an example of a change in the detection signal S2 of the IDC sensor 33B when the pressure contact is normally performed, and FIG. 15 is a change of the detection signal S2 of the IDC sensor 33B when the pressure contact is not normally performed. FIG. 16 is a diagram illustrating an example of a change in the detection signal S2 of the IDC sensor 33B when the separation is normally performed, and FIGS. 17 and 18 are flowcharts illustrating an operation flow of the image forming apparatus 1B. It is.

  In FIG. 11, in the image forming apparatus 1 </ b> B of the second embodiment, the IDC sensor 33 </ b> B is provided at a position above the roller 25 so as to detect the surface state of the intermediate transfer belt 23. In addition, the IDC sensor 33B is attached so as to move toward or away from the surface of the intermediate transfer belt 23 in synchronism with or in conjunction with the contact / separation operation of the secondary transfer roller 28. In the second embodiment, the intermediate transfer belt 23 does not need to transmit light, and may be any one that appropriately reflects light on the surface thereof.

  Since the configuration of other parts of the image forming apparatus 1B is the same as that of the image forming apparatus 1 of the first embodiment, the description thereof is omitted here. Also, parts having the same functions as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted or simplified.

  As shown in FIG. 12, the IDC sensor 33 </ b> B is held at the tip of an arm 57 that is a part of the contact / separation driving device SK, and moves in the vertical direction of the figure by the arm 57. That is, as shown in FIG. 12A, when the secondary transfer roller 28 is in a pressure contact state, the image forming operation is performed, so that the IDC sensor 33B is separated from the intermediate transfer belt 23. As shown in FIG. 12B, when the secondary transfer roller 28 is in the separated state, the IDC sensor 33B approaches the intermediate transfer belt 23 for the image stabilization operation.

  In the second embodiment, a regular reflection type or irregular reflection type sensor that reflects light on the surface of the intermediate transfer belt 23 and detects the amount of reflected light is used as the IDC sensor 33B. That is, as shown in FIG. 13, the voltage value of the detection signal S2 of the IDC sensor 33B exhibits a distance-dependent characteristic that changes according to the distance from the reference position even if the density of the toner image does not change.

  Therefore, for example, as shown in FIG. 12B, when the secondary transfer roller 28 is in a separated state, that is, when the IDC sensor 33B is closest to the intermediate transfer belt 23, the IDC sensor 33B. The distance between the IDC sensor 33B and the intermediate transfer belt 23 is adjusted so that the detection signal S2 is maximum, and the position of the IDC sensor 33B at that time is set as a reference position.

  When detecting the contact / separation state, the IDC sensor 33B detects the bare surface of the intermediate transfer belt 23, and the detection signal S2 at that time is about 3.0 V in the example of FIG.

  On the other hand, as shown in FIG. 12A, when the secondary transfer roller 28 is in the pressure contact state, the IDC sensor 33B moves upward and away from the intermediate transfer belt 23, that is, intermediate from the reference position. Since the distance from the surface of the transfer belt 23 is increased, the detection signal S2 decreases.

  Next, the contact / separation determination control in the second embodiment will be described.

  As described above, when the image forming apparatus 1B is on standby, the secondary transfer roller 28 is in a separated state. When there is a print execution request in this state, the contact / separation driving device SK is driven, the secondary transfer roller 28 is brought into a pressure contact state, and pressure contact determination control is performed accordingly.

  In the pressure determination control, first, the IDC sensor 33B is caused to emit light, and the detection signal S2 based on the amount of reflected light is monitored.

  A toner pattern TP similar to that of the first embodiment is formed on the intermediate transfer belt 23 with the IDC sensor 33B emitting light, and the secondary transfer is performed after the tip of the formed toner pattern TP has passed the secondary transfer position. The roller 28 is pressed. At this time, in order to prevent the toner of the toner pattern TP from adhering to the secondary transfer roller 28, a bias voltage having the same polarity as the charge of the toner is applied to the secondary transfer roller 28 by the bias applying device 38. deep.

  After the toner pattern TP is formed, the detection signal S2 of the IDC sensor 33B during the contact / separation operation of the secondary transfer roller 28 is detected, and the detection signal S2 when the secondary transfer roller 28 is separated is detected by the secondary transfer roller 28. When the detection signal S2 in the pressure contact state is greatly changed, it is determined that the pressure contact is normal, and the process proceeds to an image forming operation.

  For example, as shown in FIG. 14, when the secondary transfer roller 28 is in the separated state, the IDC sensor 33B is at the reference position, so the detection signal S2 is as high as about 2.2 volts. When the secondary transfer roller 28 is switched to the pressure contact state at time t4 and the toner pattern TP passes through the secondary transfer roller 28 in the pressure contact state, the IDC sensor 33B is at a position away from the reference position. S2 is as low as about 0.2 volts. The threshold value Th1 is set to about 1.2 volts, and the voltage of the detection signal S2 changes beyond the threshold value Th1 by switching the secondary transfer roller 28 to the pressure contact state. It is determined that the switch has been made.

  As shown in FIG. 15, the detection signal S2 does not change beyond the threshold value Th1 even if a predetermined time has elapsed even though the contact / separation driving device SK is driven and switched to the pressure contact state. If it is determined that the secondary transfer roller 28 is not in a normal pressure contact state. In that case, a signal indicating an abnormality is output without shifting to the image forming operation. Alternatively, the pressure contact operation of the secondary transfer roller 28 is retried.

  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, separation determination control is performed.

  That is, the IDC sensor 33B emits light while the secondary transfer roller 28 is in a pressure contact state and a bias voltage having the same polarity as the toner charge is applied to the secondary transfer roller 28, and the toner pattern TP is formed on the intermediate transfer belt 23. Form.

  After the front end portion of the toner pattern TP has passed the secondary transfer position, the secondary transfer roller 28 is separated. When the separation of the secondary transfer roller 28 is performed normally, the detection signal S2 in the pressure contact state changes greatly, and in this case, it is determined that the separation is performed normally.

  For example, as shown in FIG. 16, when the secondary transfer roller 28 is in the pressure contact state, the IDC sensor 33B is away from the reference position, so the detection signal S2 is as low as about 0.2 volts. When the secondary transfer roller 28 is switched to the separated state at time t6 and the toner pattern TP passes through the secondary transfer roller 28 in the separated state, the IDC sensor 33B is at the reference position, so the detection signal S2 is about 2 Increased to 2 volts. Since the voltage of the detection signal S2 has changed beyond the threshold value Th1 by switching the secondary transfer roller 28 to the separated state, it is determined that the secondary transfer roller 28 has been 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 S2 does not change beyond 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 it is not. In that case, an abnormal termination notification is made. Or retry contact / separation operation.

  It is determined whether the detection signal S2 is normal or abnormal depending on whether or not the voltage of the detection signal S2 has changed beyond the threshold value Th1, but instead of or along with this, the change of the voltage of the detection signal S2 The determination may be made based on whether or not the amount is equal to or greater than a set amount.

  As described above, according to the contact / separation determination control of the second embodiment, the pressure contact state and the separation state of the secondary transfer roller 28 can be determined using the detection signal S2 of the IDC sensor 33B for IDC. . 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.

  17 and 18, when there is a request for the image stabilization operation (Yes in # 41), control is performed so as to perform the image stabilization operation (# 42). If there is no request for an image stabilization operation (No in # 41), the secondary transfer roller 28 is set in a separated state (# 43). If there is a request for an image forming operation (Yes in # 44), first, The IDC sensor 33 is caused to emit light (# 45). The toner pattern TP is formed (# 46), and the voltage value V1 of the detection signal S2 of the IDC sensor 33 is acquired (# 47). The secondary transfer roller 28 is brought into a pressure contact state (# 48). The voltage value V2 of the detection signal S2 of the IDC sensor 33 is acquired (# 49). During this time, it is determined whether or not the detection signal S2 of the IDC sensor 33 has changed by a predetermined value or more (# 50).

  If yes in step # 20, it is determined that the pressure contact has been normally performed (# 51), and image formation is executed (# 53). When the image formation is completed (Yes in # 54), the IDC sensor 33 is caused to emit light (# 55), the toner pattern TP is formed (# 56), and the voltage value V2 of the detection signal S2 of the IDC sensor 33 is acquired (#). 57). The secondary transfer roller 28 is separated (# 58). The voltage value V1 of the detection signal S2 of the IDC sensor 33 is acquired (# 59). During this time, it is determined whether or not the detection signal S2 of the IDC sensor 33 has changed by a predetermined value or more (# 60).

  If yes in step # 60, it is determined that the separation has been performed normally (# 61), and if no in step # 60, it is determined that the separation is abnormal (# 62). If no in step # 50, it is determined that there is a pressure contact abnormality (# 66). 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 each embodiment described above, the image carrier may be other than the intermediate transfer belt 23, and the transfer member may be other than the secondary transfer roller 28. In addition, the configuration, structure, shape, and dimensions of the whole or each part of the intermediate transfer belt 23, the secondary transfer roller 28, the bias applying device 38, the IDC sensors 33 and 33B, the contact / separation driving device SK, or the image forming devices 1 and 1B, The number, material, processing contents, order, timing, and the like 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 a first embodiment of the present invention. It is a figure which shows the vicinity of a secondary transfer part. It is a figure which shows the example of a structure of a contact / separation drive device. It is a figure which shows the example of the relationship between a toner adhesion amount and the detection signal of an IDC sensor. FIG. 6 is a diagram illustrating an example of a toner pattern. 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. 3 is a flowchart illustrating an operation flow of the image forming apparatus. It is a figure which shows the schematic structure of the image forming apparatus of 2nd Embodiment which concerns on this invention. It is a figure which shows the vicinity of a secondary transfer part. It is a figure which shows the distance characteristic of an IDC sensor. 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. 3 is a flowchart illustrating an operation flow of the image forming apparatus.

Explanation of symbols

1,1B Image forming apparatus 23 Intermediate transfer belt (image carrier)
28 Secondary transfer roller (transfer member)
33,33B IDC sensor (detection means)
38 Bias applying device SK Contact / separation drive device
S1, S2 detection signal TP toner pattern (check toner image)

Claims (13)

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 the amount of light transmitted through the image carrier;
A change in the toner image on the image carrier due to the pressure contact of the transfer member to the image carrier is detected by the detecting means, and a pressure contact state or a separation state of the transfer member is detected based on a change in the detection signal. Configured as
An image forming apparatus. The image carrier is an intermediate transfer belt;
The detection means is provided with a light emitting portion and a light receiving portion sandwiching the intermediate transfer belt on the downstream side of the transfer member.
The image forming apparatus according to claim 1. At the time of detecting a change in the toner image by the detection means, the toner of the toner image is electrostatically attracted to the transfer member by applying a bias voltage having a polarity opposite to the charge of the toner to the transfer member;
The image forming apparatus according to claim 1. After the change of the toner image is detected by the detection means, a bias voltage having the same polarity as the charge of the toner is applied to the transfer member to electrostatically attract the toner adhering to the transfer member to the transfer member. Cleaning the transfer member
The image forming apparatus according to claim 1. Outputting 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 since the transfer member is driven to move by the contact / separation drive member;
The image forming apparatus according to claim 1. When the detection signal of the detection means does not change by a predetermined amount or more even though a predetermined time has passed since the transfer member is driven to move by the contact / separation drive member, the contact / separation drive member moves the transfer member. Drive again,
The image forming apparatus according to claim 1. An image forming apparatus configured to transfer a toner image formed in an electrophotographic process from an image carrier to a transfer material,
Optical detection means provided to detect the state of the toner image on the image carrier as a change in light reflectance;
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;
The detection means is attached so that the position with respect to the image carrier changes as the transfer member is moved by the contact / separation driving device, and the state of the surface of the image carrier is detected by the detection means. It is configured to detect a pressure contact state or a separation state of the transfer member based on a change in detection signal when
An image forming apparatus. When the detection signal changes by a predetermined amount or more, it is determined that the moving drive by the contact / separation drive device has been normally performed.
The image forming apparatus according to claim 7. When the state of the surface of the image carrier is detected by the detection means, the check toner image formed on the image carrier passes through the transfer position, and the transfer member has the same polarity as the toner charge. Apply a bias voltage of
The image forming apparatus according to claim 7 or 8. Outputting 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 since the transfer member is driven to move by the contact / separation drive member;
The image forming apparatus according to claim 7. When the detection signal of the detection means does not change by a predetermined amount or more even though a predetermined time has passed since the transfer member is driven to move by the contact / separation drive member, the contact / separation drive member moves the transfer member. Drive again,
The image forming apparatus according to claim 7. 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 the amount of light transmitted through the front and back of the image carrier,
A change in the toner image on the image carrier due to the pressure contact of the transfer member to the image carrier is detected by the detecting means, and a pressure contact state or a separation state of the transfer member is detected based on a change in the detection signal. ,
A method for detecting a pressure contact / separation state of a transfer member in an image forming apparatus. In an image forming apparatus configured to transfer a toner image formed in an electrophotographic process from an image carrier to a transfer material, separation of a transfer member that causes the transfer by being brought into pressure contact with the image carrier A method for detecting a state,
An optical detection means for detecting the state of the toner image on the image carrier as a change in light reflectance is such that the position relative to the image carrier changes as the transfer member is moved by the contact / separation driving device. And detecting a pressure contact state or a separation state of the transfer member based on a change in a detection signal when the state of the surface of the image carrier is detected by the detection unit.
A method for detecting a separation state of a transfer member in an image forming apparatus.