JP2010266762A - Image forming apparatus - Google Patents

Abstract

An object of the present invention is to protect a sensor that does not require a dedicated drive source, has a simple mechanism for opening and closing a shutter, does not require time for opening and closing the shutter, and can suppress causes of failure and cost increase. An image forming apparatus including a shutter is provided.
A recording medium on which a toner image primarily transferred onto an intermediate transfer belt 61 is secondarily transferred is rotated forward so that the recording medium is conveyed to a secondary transfer position, and an intermediate transfer belt 61. In contrast to the sensor 51 for inspecting the toner image, the sensor 51 is shielded from the intermediate transfer belt 61 when the shutter is closed, and the sensor 51 is exposed to the intermediate transfer belt 61 when the shutter is open. The shutter 40 is moved from the shutter closed state to the shutter open state by receiving the reverse rotational force of the reverse rotation when the medium conveying roller 13 rotates reversely. Constitute.
[Selection] Figure 2

Description

  The present invention relates to a conveyance roller for conveying a recording medium on which a toner image primarily transferred onto an intermediate transfer belt is secondarily transferred to a position where the toner image is secondarily transferred, and a sensor for inspecting the toner image on the intermediate transfer belt. The present invention relates to an image forming apparatus provided with a protective shutter.

  In recent years, electrophotographic image forming apparatuses capable of forming multicolor images, such as color copiers and color printers, have been developed. For example, a toner image for each color is formed on a latent image carrier such as a photoconductive drum for each color, and the toner images for each color are sequentially superimposed on an intermediate transfer belt, which is an intermediate transfer body, and primarily transferred. Well known is an intermediate transfer type color image forming apparatus that forms a multicolor image and then secondary-transfers the multicolor image onto a recording sheet conveyed by a conveyance roller and fixes it to form an image. Yes.

  In this intermediate transfer type color image forming apparatus, automatic registration adjustment is performed in order to prevent color misregistration of a multicolor image formed on the intermediate transfer belt. In this automatic registration adjustment, it is checked whether or not there is a shift between the colors of the image primarily transferred from the photosensitive drum for each color.

  In order to check the presence or absence of this deviation, it is necessary to detect a registration mark, which is a toner image indicating an inspection reference pattern formed on the intermediate transfer belt, and a reflective optical sensor is usually used for this detection. It is done. This automatic registration adjustment is performed when the image forming apparatus is not performing an original image forming operation.

  On the other hand, when the image forming apparatus is performing an original image forming operation, a cycle in which a toner image is formed and removed is frequently repeated on the intermediate transfer belt. Therefore, when the image forming apparatus is performing an original image forming operation, toner may be scattered on the reflective optical sensor, and the detection surface of the optical sensor may become dirty. Alternatively, there is a risk that paper dust or the like of the recording paper to be secondarily transferred adheres to the detection surface of the reflective optical sensor and becomes dirty.

  Therefore, when the reflective optical sensor is provided with a shutter and the reflective optical sensor is not used, the shutter is closed to prevent the reflective optical sensor from becoming dirty. Is adopted.

  This shutter opening / closing control can be performed by using a solenoid or the like. In addition, a method that is performed in conjunction with other operations in the image forming apparatus has been proposed (see, for example, Patent Document 1).

  In Patent Document 1, in an intermediate transfer type image forming apparatus, a reflective optical sensor that detects a registration mark, which is a toner image indicating a reference pattern for inspection, is provided with a shutter, and this shutter opening / closing operation is performed in a secondary manner. A configuration is described in which the secondary transfer unit having a transfer function is linked to the separating operation with respect to the intermediate transfer belt.

  In the configuration described in Patent Document 1, the shutter provided in the reflective optical sensor is opened at the same time as the secondary transfer unit is separated from the intermediate transfer belt. The registration mark, which is a toner image showing the reference pattern for inspection, is detected. The configuration described in Patent Document 1 has an advantage that a new drive source for opening and closing the shutter is not required.

JP 2006-3399 A

  By the way, in the configuration using a solenoid or the like for controlling the opening and closing of the shutter, it is necessary to newly install a solenoid or the like in order to open and close the shutter. Further, the configuration described in Patent Document 1 has an advantage that a dedicated drive source for opening and closing the shutter is not required.

  However, in the configuration described in Patent Document 1, since the secondary transfer unit is heavier than the shutter for protecting the optical sensor, it takes time to move the secondary transfer unit in and out of contact. In addition, since it is necessary to link the operation of separating and contacting the secondary transfer unit from the intermediate transfer belt and the operation of opening and closing the shutter, the mechanism becomes complicated, resulting in failure and cost increase.

  Accordingly, the present invention has been made to solve such a problem, and a dedicated drive source is used to open and close a protective shutter for a sensor that inspects a toner image on an intermediate transfer belt. An image forming apparatus including a shutter for protecting a sensor that is not required, has a simple mechanism for opening and closing the shutter, does not require time for the opening and closing operation of the shutter, and can suppress factors of failure and cost increase. Is what you want to offer.

  An image forming apparatus according to the present invention includes a medium conveying roller that conveys a recording medium on which a toner image primarily transferred onto an intermediate transfer belt is secondarily transferred to a position where the toner image is secondarily transferred by rotating the recording medium, and an intermediate transfer An image provided with a shutter that exposes the sensor to the intermediate transfer belt when the shutter is in a closed state and shields the sensor from the intermediate transfer belt when the shutter is open. Forming device.

  In this image forming apparatus, the above-described shutter is characterized in that the reverse of the reverse rotation force of the medium conveyance roller causes the reverse rotation force to be transmitted to shift from the shutter closed state to the shutter open state.

  Therefore, according to the above-described image forming apparatus, a dedicated drive source can be made unnecessary for opening and closing the shutter for protecting the sensor whose inspection target is the toner image on the intermediate transfer belt. Further, it is not necessary to interlock the opening / closing operation of the shutter with the separation / contact operation of the secondary transfer unit with respect to the intermediate transfer belt.

  Accordingly, the mechanism for opening and closing the shutter can be simplified, and the shutter opening and closing operation does not take time, and therefore, the cause of failure and cost increase in the image forming apparatus can be suppressed.

  In the above image forming apparatus, the sensor and the shutter are arranged in the vicinity of the position where the secondary transfer is performed and upstream of the position where the secondary transfer is performed with respect to the rotation direction of the intermediate transfer belt. It is preferable to install.

  In the above image forming apparatus, generally, a secondary transfer unit is used for secondary transfer of a toner image onto a recording medium. The secondary transfer unit is usually provided with a secondary transfer roller, and a nip formed as a contact portion between the secondary transfer roller and the intermediate transfer belt is subjected to the secondary transfer. Corresponds to position.

  Therefore, at the nip portion, that is, at the position where the secondary transfer is performed, the moving direction of the intermediate transfer belt and the conveyance direction of the recording medium conveyed toward the position where the secondary transfer is performed by the medium conveying roller. The intermediate transfer belt and the medium transport roller are disposed so as to be the same.

  Then, the medium transport roller that transports the recording medium to the secondary transfer position is positioned on the near side with respect to the recording medium transport direction, and operates by receiving the reverse rotational force of the medium transport roller. The position at which the shutter that is to be protected and the sensor that is the object of protection of the shutter is disposed at the front side with respect to the conveyance direction of the recording medium, that is, the position at which secondary transfer is performed with respect to the rotation direction of the intermediate transfer belt It is reasonable to set the position closer to the front.

  By doing so, there are the following advantages. If the sensor and shutter are disposed at a position behind the secondary transfer position with respect to the rotation direction of the intermediate transfer belt, the toner image on the intermediate transfer belt to be inspected by the sensor is The state after passing through the secondary transfer roller of the secondary transfer unit.

  Therefore, the toner image on the intermediate transfer belt is peeled off from the intermediate transfer belt by the transfer operation of the secondary transfer roller. Therefore, in order to prevent the toner image from being peeled off from the intermediate transfer belt by the secondary transfer roller, the secondary transfer unit needs to be separated from the intermediate transfer belt.

  On the other hand, if the sensor and shutter are disposed at a position before the secondary transfer position with respect to the rotation direction of the intermediate transfer belt as in the image forming apparatus described above, the sensor The toner image on the intermediate transfer belt to be inspected is in a state before passing through the secondary transfer roller of the secondary transfer unit.

  Therefore, the toner image on the intermediate transfer belt is not peeled off from the intermediate transfer belt by the transfer operation of the secondary transfer roller. Therefore, the sensor can inspect the toner image that has not been peeled off. Therefore, the toner image can be inspected without separating the secondary transfer unit from the intermediate transfer belt.

  In the above image forming apparatus, it is preferable that the shutter is configured as follows. That is, the shutter is composed of a shutter mounting piece, a shutter door piece, a rotating means, and an urging member.

  Among these, the shutter mounting piece is configured to be rotatable by the rotation of the rotation shaft with the rotation shaft provided at the base end portion of the shutter mounting piece as a fulcrum. The shutter door piece is provided at the tip of the shutter mounting piece. The shutter door piece is configured to be in a position where the sensor is shielded when the shutter is closed, and in a position where the sensor is exposed when the shutter is open.

  The turning means is means for turning the turning shaft in response to transmission of the reverse rotational force from the medium transport roller. The urging member is configured to urge the shutter mounting piece so that the shutter door piece is directed to a position where the shutter shields the sensor from the intermediate transfer belt.

  According to the above-described image forming apparatus, the mechanism for opening and closing the shutter can be simplified, and the opening and closing operation of the shutter does not require time. Therefore, it is possible to suppress failure and cost increase in the image forming apparatus. it can.

  Further, it is preferable that the shutter rotating means is configured as follows. That is, the shutter rotating means is fixed to the one-way gear that is provided on the medium conveying roller and reversely rotates integrally with the medium conveying roller when the medium conveying roller rotates reversely, and the rotating shaft of the shutter mounting piece. The above-described one-way gear and the rotation gear that is screwed together are configured.

  In this way, the mechanism for opening and closing the shutter can be further simplified, and the opening and closing operation of the shutter does not require time, and therefore, it is possible to suppress failure and cost increase factors in the image forming apparatus. it can.

  In the above image forming apparatus, it is preferable to do the following. That is, the medium transport roller is driven by a motor capable of forward / reverse rotation and stop restraint. By doing so, the shutter can be operated as follows.

  That is, when the medium transport roller rotates in the reverse direction, the shutter moves from the shutter closed state to the shutter open state, and the medium transport roller enters the stop restrained state, so that the shutter open state is maintained, and the medium transport roller rotates in the reverse direction. Alternatively, by entering a state that is neither the stop restraint state, the shutter is returned to the closed state by urging, and the shutter closed state is maintained.

  By doing so, the shutter can be opened and closed reliably, and the opening and closing operation of the shutter does not take time, and therefore, it is possible to suppress the failure and the cost increase in the image forming apparatus.

  In the above image forming apparatus, it is preferable that the medium transport roller is as follows. That is, the medium conveyance roller can be controlled to drive the rotation angle during reverse rotation by the motor.

  Then, during the reverse rotation of the medium conveying roller, the medium conveying roller is driven and controlled so that the rotation shaft of the shutter rotates by the rotation angle necessary for the shutter to shift from the shutter closed state to the shutter open state. To do.

  By doing so, it is possible to save time for opening and closing the shutter.

  In the above image forming apparatus, the sensor is generally constituted by a reflective optical sensor. In addition, it is preferable that this sensor is disposed close to the intermediate transfer belt. Alternatively, the toner image that is usually the inspection target of the sensor is a registration mark that indicates a reference pattern for inspection.

  According to the present invention, a medium conveying roller that conveys a recording medium on which a toner image primarily transferred onto an intermediate transfer belt is secondarily transferred to a position where the toner image is secondarily transferred, and a toner image on the intermediate transfer belt are to be inspected. In the image forming apparatus provided with the shutter for protecting the sensor, the shutter can be shifted from the shutter closed state to the shutter open state by the reverse rotation of the medium transport roller.

  Therefore, a dedicated drive source can be dispensed with to open and close the shutter for protecting the sensor that inspects the toner image on the intermediate transfer belt. Further, it is not necessary to interlock the opening / closing operation of the shutter with the separation / contact operation of the secondary transfer unit with respect to the intermediate transfer belt.

  Accordingly, the mechanism for opening and closing the shutter can be simplified, and the shutter opening and closing operation does not take time, and therefore, the cause of failure and cost increase in the image forming apparatus can be suppressed.

1 is a configuration diagram illustrating a configuration of an image forming apparatus according to an embodiment. FIG. 3 is a configuration diagram showing a peripheral structure of an intermediate transfer belt unit of the image forming apparatus in the embodiment. FIG. 3 is an enlarged view of the shutter and its periphery when the shutter is closed in the image forming apparatus according to the embodiment. FIG. 3 is an enlarged view of the shutter and its surroundings in the shutter open state of the image forming apparatus in the embodiment. FIG. 4A is an explanatory diagram in the shutter closed state, and FIG. 4B is an explanatory diagram in the shutter open state, showing a relationship between the shutter and the optical sensor of the image forming apparatus in the embodiment.

  Next, an image forming apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram showing the configuration of the image forming apparatus. In FIG. 1, an image forming apparatus 100 according to this embodiment is an apparatus that forms multicolor and single color images on a predetermined sheet (recording paper) in accordance with image data transmitted from the outside. The image forming apparatus 100 includes an apparatus main body 110 and an automatic document processing apparatus 120 provided on the apparatus main body 110.

  The automatic document processing apparatus 120 includes a document placing table 92 and an illumination unit 90. The document placing table 92 is made of transparent glass and is provided on the upper part of the apparatus main body 110. The illumination unit 90 has a function of providing light for reading a document.

  The automatic document processing apparatus 120 has a function of automatically conveying a document on a document placing table 92. Further, the document processing device 120 is configured to be rotatable in the direction of arrow M, and the document can be manually placed by opening the document placing table 92.

  The apparatus main body 110 in the image forming apparatus 100 includes an exposure unit 1, a developing device 2, a photosensitive drum 3, a cleaner unit 4, a charger 5, an intermediate transfer unit 6, a secondary transfer unit 10, a fixing unit 7, and a paper feed cassette 81. , And a paper discharge tray 91 and the like.

  The image data handled by the image forming apparatus 100 is color image data using each color of black (B), cyan (C), magenta (M), and yellow (Y). Accordingly, among the above-described components, the developing device 2, the photosensitive drum 3, the charger 5, and the cleaner unit 4 are each four in order to form four types of latent images corresponding to these colors. These constitute four image stations of black, cyan, magenta, and yellow.

  The photosensitive drum 3 is composed of a rotating drum, and an electrostatic latent image is formed on the circumferential surface thereof as described below. The charger 5 is a charging means for uniformly charging the surface of the photosensitive drum 3 to a predetermined potential. In addition to the charger type as shown in FIG. 1, a contact type roller type or brush type charger is used. Sometimes used.

  The exposure unit 1 is configured as a laser scanning unit (LSU) provided with a laser emitting portion, a reflection mirror, and the like. The exposure unit 1 includes a polygon mirror that scans a laser beam, a lens that guides the laser light reflected by the polygon mirror to the photosensitive drum 3, and optical elements such as a mirror.

  In addition, as the exposure unit 1, for example, an EL or LED writing head in which light emitting elements are arranged in an array may be used. The exposure unit 1 has a function of forming an electrostatic latent image corresponding to the image data on the surface thereof by exposing the charged photosensitive drum 3 according to the input image data.

  The developing device 2 has a function of developing the electrostatic latent images formed on the respective photosensitive drums 3 with toners of four colors (Y, M, C, K). The cleaner unit 4 has a function of removing and collecting toner remaining on the surface of the photosensitive drum 3 after development and image transfer.

  The intermediate transfer unit 6 includes an intermediate transfer belt 61, an intermediate transfer belt driving roller 62, an intermediate transfer belt driven roller 63, an intermediate transfer roller 64, and an intermediate transfer auxiliary roller 64a. Among these, the intermediate transfer belt drive roller 62, the intermediate transfer belt driven roller 63, and the intermediate transfer roller 64 are used to stretch and drive the intermediate transfer belt 61. Each intermediate transfer roller 64 has a function of applying a transfer bias for transferring the toner image on the photosensitive drum 3 onto the intermediate transfer belt 61.

  The intermediate transfer belt 61 is provided so as to come into contact with the respective photosensitive drums 3, and the intermediate transfer belt 61 transfers the toner images of the respective colors formed on the photosensitive drum 3 to the intermediate transfer belt 61. In this way, a color toner image (multicolor toner image) is formed on the intermediate transfer belt 61 by sequentially transferring the toner images on the intermediate transfer belt 61. The intermediate transfer belt 61 having such a function is formed in an endless manner using, for example, a film having a thickness of about 100 μm to 150 μm.

  In the above intermediate transfer unit 6, the transfer of the toner image from the photosensitive drum 3 to the intermediate transfer belt 61 is performed by the intermediate transfer roller 64 that is in contact with the back side of the intermediate transfer belt 61. A high voltage transfer bias (a high voltage having a polarity (+) opposite to the toner charging polarity (−)) is applied to the intermediate transfer roller 64 in order to transfer the toner image.

  The intermediate transfer roller 64 is a roller whose base is a metal (for example, stainless steel) shaft having a diameter of 8 to 10 mm and whose surface is covered with a conductive elastic material (for example, EPDM, urethane foam, or the like). By this conductive elastic material, a high voltage can be uniformly applied to the intermediate transfer belt 61. In this embodiment, a roller-shaped transfer electrode is used as the transfer electrode, but a brush or the like may also be used.

  As described above, the toner images formed on the respective photosensitive drums 3 in accordance with the respective hues are stacked on the intermediate transfer belt 61. The toner images stacked in this way are conveyed to the secondary transfer unit 10 by the rotation of the intermediate transfer belt 61 and transferred onto the recording paper.

  The secondary transfer unit 10 includes a secondary transfer roller 10a, and the toner image formed on the intermediate transfer belt 61 is transferred onto the recording paper by the secondary transfer roller 10a. At this time, the intermediate transfer belt 61 and the transfer roller 10 are pressed against each other at a nip formed by the contact between the intermediate transfer belt 61 and the transfer roller 10, and the transfer roller 10 transfers the toner onto a recording sheet. Voltage is applied (a high voltage having a polarity (+) opposite to the charging polarity (−) of the toner).

  In the secondary transfer unit 10, in order to obtain the nip constantly, either the transfer roller 10 or the intermediate transfer belt drive roller 62 is formed of a hard material (metal or the like). At the same time, the other is formed of a soft material such as an elastic roller (such as an elastic rubber roller or a foaming resin roller).

  In the intermediate transfer unit 6, the toner attached to the intermediate transfer belt 61 by contacting the photosensitive drum 3 or the transfer roller 10 is not transferred onto the recording paper and remains on the intermediate transfer belt 61. The toner that has been used becomes a cause of toner color mixing in the next step.

  Therefore, the toner remaining on the intermediate transfer belt 61 is removed and collected by the intermediate transfer belt cleaning unit 65. The intermediate transfer belt cleaning unit 65 includes a cleaning member that contacts the intermediate transfer belt 61 and cleans the intermediate transfer belt 61.

  For example, a cleaning blade is used as the cleaning member. As described above, the cleaning blade comes into contact with the intermediate transfer belt 61 to clean the intermediate transfer belt 61. Further, the back side of the portion of the intermediate transfer belt 61 with which the cleaning blade comes into contact is supported by an intermediate transfer belt driven roller 63.

  The fixing unit 7 includes a fixing roller 71 and a pressure roller 72. The fixing unit 7 has a function of fixing an unfixed toner image formed on the recording paper by heating and melting and fixing it on the recording paper. In the fixing unit 7, the fixing roller 71 and the pressure roller 72 are rotated with the recording paper interposed therebetween, and the recording paper is conveyed toward the conveying roller 12b as shown in FIG.

  The paper feed cassette 81 is a tray for storing recording paper used for image formation, and is provided below the exposure unit 1 of the apparatus main body 110. Alternatively, a manual paper feed cassette 82 that manually feeds paper can be used. A paper discharge tray 91 provided above the apparatus main body 110 is a tray for collecting printed recording sheets face down.

  In the apparatus main body 110, recording paper fed from the paper feed cassette 81 and the manual paper feed cassette 82 is passed through the secondary transfer roller 10a of the secondary transfer unit 10 and the fixing unit 7 described above. A substantially vertical sheet conveyance path S for conveying the sheet to the discharge tray 91 is provided.

  Further, in the vicinity of the sheet conveyance path S from the sheet feeding cassette 81 or the manual sheet feeding cassette 82 to the sheet discharge tray 91, pickup rollers 11a and 11b, a plurality of conveying rollers 12a to 12d, a PS roller 13, and a PS roller An auxiliary roller 13a, a secondary transfer roller 10a, a fixing unit 7 and the like are provided. Of these, the PS roller 13 corresponds to the medium transport roller described above.

  The PS roller 13, the PS auxiliary roller 13a, and the transport rollers 12a to 12d are small rollers for promoting and assisting the transport of the recording paper, and a plurality of the rollers are provided along the paper transport path S.

  Among these, the PS roller 13 is provided with a motor (not shown) that rotates the PS roller 13 to convey the recording paper. When the PS roller 13 rotates forward, the recording paper is transferred to the secondary roller. It is conveyed toward the secondary transfer roller 10a of the transfer unit 10.

  The PS auxiliary roller 13a is in pressure contact with the PS roller 13, and is conveyed by the recording paper passing between the PS auxiliary roller 13a and the PS roller 13 provided in a pair with the PS roller 13. Done.

  The pickup roller 11 a is provided near the end of the paper feed cassette 81 and has a function of picking up recording paper from the paper feed cassette 81 one by one and feeding it to the paper transport path S. Similarly, the pickup roller 11 b is provided near the end of the manual paper feed cassette 82 and has a function of picking up recording paper from the manual paper feed cassette 82 one by one and feeding it to the paper transport path S.

  The above is the description of the overall configuration of the image forming apparatus 100. Next, features of the present invention will be described. FIG. 2 shows the mechanism structure of the characteristic portion of the present invention, and shows the peripheral structure of the intermediate transfer belt unit 6. Around the intermediate transfer belt unit 6, a secondary transfer unit 10, a PS roller 13, a PS auxiliary roller 13a, a shutter 40, and an optical sensor 51 are disposed.

  In FIG. 2, as described above, the intermediate transfer belt 61 of the intermediate transfer belt unit 6 transfers the toner images of the respective colors formed on the photosensitive drum 3 sequentially and overlaid on the intermediate transfer belt 61. It has a function of forming a color toner image (multicolor toner image) on the intermediate transfer belt 61.

  Further, the secondary transfer unit 10 includes a secondary transfer roller 10 a that forms a nip portion in contact with the intermediate transfer belt 61 of the intermediate transfer belt unit 6, and the intermediate transfer belt 10 a is formed by the secondary transfer roller 10 a. 61 has a function of transferring a toner image formed on the recording sheet 61 onto a recording sheet.

  In the secondary transfer unit 10, when the image forming apparatus 100 is performing an original image forming operation, as described above, the transfer roller 10 of the secondary transfer unit 10 is connected to the intermediate transfer belt of the intermediate transfer belt unit 6. The pressure contact state is in pressure contact with 61. Further, when the image forming apparatus 100 is not performing the original image forming operation, the transfer roller 10 of the secondary transfer unit 10 is in a separated state in which it is separated from the intermediate transfer belt 61 of the intermediate transfer belt unit 6.

  The secondary transfer unit 10 can be rotated with the secondary transfer unit support shaft 10b as a fulcrum. The movement between the pressure contact state and the separated state causes the secondary transfer unit 10 to move to the secondary transfer unit support shaft 10b. It is performed by rotating around the fulcrum.

  The PS roller 13 and the PS auxiliary roller 13a have a function of conveying the recording sheet to the nip portion between the intermediate transfer belt 61 of the intermediate transfer belt unit 6 and the secondary transfer roller 10a of the secondary transfer unit 10. Have.

  By the way, in the color image forming apparatus 100 of the intermediate transfer type that secondarily transfers the toner image primarily transferred to the intermediate transfer belt 61 to the recording paper, the multicolor image formed on the intermediate transfer belt 61 does not cause color misregistration. In order to do so, automatic registration adjustment is performed. In this automatic registration adjustment, it is checked whether there is a shift between the colors of the image primarily transferred from the photosensitive drum 3 for each color.

  In order to check the presence or absence of this deviation, it is necessary to detect a registration mark, which is a toner image indicating a reference pattern for inspection, formed on the intermediate transfer belt 61. Usually, a reflective optical sensor 51 is used for this detection. Is used. The optical sensor 51 is a reflective optical sensor composed of an LED 51a and a phototransistor 51b (see FIGS. 3 to 5).

  The automatic registration adjustment described above is performed when the image forming apparatus 100 is not performing an original image forming operation. When the image forming apparatus 100 is not performing an original image forming operation, the secondary transfer unit 10 is in a state of being separated from the intermediate transfer belt 61 as described above.

  In contrast, when the image forming apparatus 100 is performing an original image forming operation, a cycle in which a toner image is formed and removed on the intermediate transfer belt 61 is frequently repeated. Therefore, when the image forming apparatus 100 is performing an original image forming operation, toner may be scattered on the reflective optical sensor 51 and the detection surface of the optical sensor 51 may become dirty. Alternatively, there is a possibility that paper dust or the like of recording paper to be secondarily transferred adheres to the detection surface of the reflective optical sensor 51 and becomes dirty.

  Therefore, when the reflective optical sensor 51 is provided with the shutter 40 and the reflective optical sensor 51 is not used, the reflective optical sensor 51 is soiled by closing the shutter 40. Is preventing.

  The shutter 40 uses a mechanism that opens when the PS roller 13 rotates in reverse to receive transmission of the reverse rotational force. Next, the shutter 40 will be described.

  FIG. 3 is an enlarged view showing the shutter 40 and its periphery in FIG. 2 in an enlarged manner, and shows a state in which the shutter 40 is closed. FIG. 4 is an enlarged view showing a state in which the shutter 40 is closed as in FIG.

  2 to 4, the shutter 40 and the sensor 51 protected by the shutter 40 are in the vicinity of the secondary transfer unit 10 that performs secondary transfer and with respect to the rotation direction of the intermediate transfer belt 61. Arranged upstream of the secondary transfer unit 10.

  This is due to the following reason. That is, in the image forming apparatus 100 described above, the moving direction of the intermediate transfer belt 61 and the PS at the nip portion between the intermediate transfer belt 61 of the intermediate transfer belt unit 6 and the secondary transfer roller 10a of the secondary transfer unit 10 are described. The intermediate transfer belt 61 and the PS roller 13 are disposed so that the recording paper is conveyed toward the nip portion by the roller 13 in the same direction.

  That is, the PS roller 13 that conveys the recording paper to the secondary transfer unit 10 is disposed upstream of the secondary transfer unit 10 with respect to the recording paper conveyance direction, and transmits the reverse rotational force of the PS roller 13. The shutter 40 that operates in response to this and the position of the sensor 51 that is protected by the shutter 40 are located upstream of the secondary transfer unit 10 with respect to the conveyance direction of the recording paper, and the intermediate transfer. This is because it is reasonable to set the position upstream of the secondary transfer unit 10 with respect to the rotation direction of the belt 61.

  2 to 4, the shutter 40 includes a shutter door piece 41, a shutter attachment piece 42, a shutter rotation shaft 42a, a coil spring 43, a rotation gear 44, a rotation gear attachment piece 45, and a shutter holding case 46. It consists of

  In FIG. 3 showing the closed state of the shutter 40, the shutter holding case 46 has a substantially F shape, and a vertical wall 46a corresponding to a horizontal straight line portion of the F shape and an inclined line of the F shape. And an inclined wall 46b corresponding to this portion, and is attached to the intermediate transfer unit 6 so that the F-shaped opening surface faces the intermediate transfer belt 61.

  The shutter holding case 46 is attached to the intermediate transfer unit 6 such that the vertical wall 46 a is substantially perpendicular to the intermediate transfer belt 61 and substantially faces the secondary transfer unit 10.

  The shutter door 41 has a plate shape substantially parallel to the intermediate transfer belt 61, and the right end, which is the end facing the secondary transfer unit 10, is the upper end of the vertical wall 46 a facing the intermediate transfer belt 61. Abut.

  The left end of the shutter door piece 41 is the tip of the shutter mounting piece 42 having a shape extending in a direction away from the surface of the intermediate transfer belt 61 substantially perpendicularly to the intermediate transfer belt 61 and facing the intermediate transfer belt 61. Are combined.

  The base end which is the other end of the shutter mounting piece 42 has an L-shape bent toward the secondary transfer unit 10, and the end of the bent base end has a shutter rotation. The moving shaft 42a is fixed. The shutter rotation shaft 42 a is rotatably supported by a rotation gear attachment piece 45, and the rotation gear attachment piece 45 is fixed to the inner surface near the lower end portion of the vertical wall 46 a of the shutter holding case 46. Has been.

  Further, between the end of the inclined wall 46b of the shutter holding case 46 and the shutter mounting piece 42, the shutter mounting is performed so that the right end of the shutter door piece 41 is in contact with the upper end of the vertical wall 46a. A coil spring 43 is provided to press and bias the piece 42 in the direction of the vertical wall 46a.

  A rotation gear 44 is fixed to the shutter rotation shaft 42a fixed to the base end portion of the shutter mounting piece 42 by the shutter rotation shaft 42a. Therefore, when the rotating gear 44 rotates counterclockwise in FIG. 3, the shutter rotating shaft 42a rotates in the same manner, and the shutter mounting piece 42 is in the direction opposite to the secondary transfer unit 10 direction. It moves and inclines, the right end of the shutter door piece 41 moves away from the upper end of the vertical wall 46a of the shutter holding case 46, and the shutter 40 is in an open state.

  The rotating gear 44 is screwed with a one-way gear 49 attached to the PS roller 13. The one-way gear 49 rotates integrally with the PS roller 13 only when the PS roller 13 rotates in one direction. The case where the PS roller 13 rotates in one direction is a case where the PS roller 13 rotates in the reverse direction.

  That is, the one-way gear 49 rotates integrally with the PS roller 13 only when the PS roller 13 rotates in the reverse direction, and does not follow the PS roller 13 when the PS roller 13 rotates in the forward direction, and therefore does not rotate at all. . As described above, the PS roller 13 to which the one-way gear 49 is attached rotates forward when the recording sheet is conveyed to the secondary transfer unit 10.

  Therefore, when the recording paper does not need to be conveyed to the secondary transfer unit 10, that is, when the image forming apparatus 100 is not performing the original image forming operation, no problem occurs even if the PS roller 13 is rotated in the reverse direction. Therefore, when the image forming apparatus 100 is not performing the original image forming operation, the PS gear 13 is rotated in the reverse direction so that the rotating gear 44 transmits the reverse rotational force from the PS roller 13 through the one-way gear 49. In response, the rotation gear 44 rotates and the shutter 40 can be opened.

  Inside the shutter holding case 46, there is provided a reflective optical sensor 51 constituted by the LED 51a and the phototransistor 51b used for the automatic registration adjustment described above. The optical sensor 51 is supported by a sensor holding piece 52, and the sensor holding piece 52 is fixed to the inner surface of the vertical wall 46 a of the shutter holding case 46.

  Accordingly, as shown in FIG. 5A, the optical sensor 51 is shielded against the intermediate transfer belt 61 when the shutter 40 is closed, and as shown in FIG. 5B when the shutter 40 is closed. As described above, the optical sensor 51 is exposed to the intermediate transfer belt 61.

  The PS roller 13 is rotationally driven by a motor (not shown) as described above. A stepping motor is used as this motor. This stepping motor is a motor capable of forward / reverse rotation, stop restraint, and unconstrained. That is, the stepping motor rotates in the forward direction by flowing a pulse current, and rotates in the reverse direction by flowing a pulse current having a polarity opposite to the normal rotation.

  In addition, the stepping motor enters a stop restraint state in which the stopped state is maintained by flowing a continuous current, and enters a non-restraint state by preventing a current from flowing through the motor. Further, the stepping motor can control the rotation angle by changing the number of pulses of the pulse current when rotating forward and backward.

  Therefore, when the PS roller 13 rotates in reverse at a predetermined rotation angle, as described above, the rotation gear 44 rotates counterclockwise in FIG. 3 and the shutter rotation shaft 42a rotates. The shutter mounting piece 42 moves and tilts, and the shutter door piece 41 moves away from the vertical wall 46a and the shutter 40 is opened.

  Then, when the PS roller 13 is in the stop restrained state, the rotation gear 44 is also in the stop restrained state and continues in the stopped state, so that the state where the shutter 40 is opened is continued. After that, the PS roller 13 is in a state that is neither in the reverse rotation state nor the stop restraint state, that is, in the unrestrained state or by rotating in the forward direction, the stop restraint state of the rotating gear 44 is released. Due to the bias of the coil spring 43, the shutter mounting piece 42 is pressed in the direction of the vertical wall 46a, moves in the direction of the vertical wall 46a, and the shutter 40 is closed.

  According to the image forming apparatus 100 described above, the shutter 40 can shift from the shutter closed state to the shutter open state by receiving the transmission of the reverse rotational force by the reverse rotation of the PS roller 13.

  Therefore, a dedicated drive source can be dispensed with for opening and closing the protective shutter 40 of the optical sensor 51 that inspects the toner image on the intermediate transfer belt 61. Further, it is not necessary to link the opening / closing operation of the shutter 40 with the separation / contact operation of the secondary transfer unit 10 relative to the intermediate transfer belt 61.

  Further, the shutter 40 shifts from the shutter closed state to the shutter open state by the reverse rotation of the PS roller 13, and maintains the shutter open state by the PS roller 13 being in the stop restrained state, and the PS roller 13 enters a state that is neither the reverse rotation nor the stop restrained state, and the shutter close state can be maintained by returning to the shutter closed state by the bias of the coil spring 43.

  Therefore, the mechanism for opening and closing the shutter 40 can be simplified, and the opening and closing operation of the shutter 40 does not require time, and therefore, the failure and the cost increase in the image forming apparatus 100 can be suppressed.

  In the image forming apparatus 100, the optical sensor 51 and the shutter 40 are secondary in the vicinity of the secondary transfer unit 10 in which secondary transfer is performed and with respect to the rotation direction of the intermediate transfer belt 61. It is arranged in front of the transfer unit 10.

  Therefore, the toner image on the intermediate transfer belt 61 to be inspected by the optical sensor 51 is in a state before passing through the secondary transfer roller 10 a of the secondary transfer unit 10. Therefore, the toner image on the intermediate transfer belt 61 is not peeled off from the intermediate transfer belt 61 by the transfer operation of the secondary transfer roller 10a.

  Therefore, the optical sensor 51 can inspect the toner image that is not peeled off. Therefore, even if the secondary transfer unit 10 is not separated from the intermediate transfer belt 61, the optical sensor 51 can inspect the toner image that is not peeled off.

DESCRIPTION OF SYMBOLS 1 Exposure unit 2 Developer 3 Photoconductor drum 4 Cleaner unit 5 Charger 6 Intermediate transfer unit 7 Fixing unit 10 Secondary transfer unit 10a Secondary transfer roller 10b Secondary transfer unit support shafts 11a and 11b Pickup roller,
12a to 12d Conveying roller 13 PS roller 13a PS auxiliary roller 40 Shutter 41 Shutter door piece 42 Shutter mounting piece 42a Shutter rotating shaft 43 Coil spring 44 Rotating gear 45 Rotating gear mounting piece 46 Shutter holding case 46a Vertical wall 46b Inclined wall 49 One-way gear 51 Optical sensor 51a LED
51b Phototransistor 52 Sensor holding piece 61 Intermediate transfer belt 62 Intermediate transfer belt drive roller 63 Intermediate transfer belt driven roller 64 Intermediate transfer roller 64a Intermediate transfer auxiliary roller 65 Intermediate transfer belt cleaning unit 71 Fixing roller 72 Pressure roller 81 Paper feed cassette 82 Manual paper feed cassette 90 Illumination unit 91 Paper discharge tray 92 Document placing table 100 Image forming apparatus 110 Apparatus main body 120 Automatic document processing apparatus

Claims (9)

A medium conveying roller that conveys the recording medium on which the toner image primarily transferred onto the intermediate transfer belt is secondarily transferred to the position where the toner image is secondarily transferred by rotating the recording medium forwardly;
With respect to a sensor for inspecting the toner image on the intermediate transfer belt, the sensor is shielded from the intermediate transfer belt when the shutter is closed, and the sensor is exposed to the intermediate transfer belt when the shutter is open. An image forming apparatus comprising:
2. The image forming apparatus according to claim 1, wherein the shutter moves from the shutter closed state to the shutter open state by receiving the reverse rotational force of the reverse rotation when the medium conveying roller rotates reversely. The image forming apparatus according to claim 1.
The sensor and the shutter are arranged near the position where the secondary transfer is performed and upstream of the position where the secondary transfer is performed with respect to the rotation direction of the intermediate transfer belt. An image forming apparatus provided. The image forming apparatus according to claim 1 or 2,
The shutter is
A shutter mounting piece that can be rotated by rotation of the rotation shaft with a rotation shaft provided at the base end as a fulcrum;
A shutter door piece provided at a tip of the shutter mounting piece, in the position where the sensor is shielded in the shutter closed state, and in a position where the sensor is exposed in the shutter open state;
A rotating means for receiving the transmission of the reverse rotational force from the medium conveying roller and rotating the rotating shaft;
And an urging member that urges the shutter mounting piece so that the shutter door piece is directed to a position where the sensor shields the sensor from the intermediate transfer belt. The image forming apparatus according to claim 3.
The rotating means of the shutter is
A one-way gear that is provided in the medium conveying roller and rotates in the reverse direction integrally with the medium conveying roller when the medium conveying roller rotates in the reverse direction;
An image forming apparatus comprising: a rotation gear fixed to the rotation shaft of the shutter mounting piece and screwed with the one-way gear. The image forming apparatus according to claim 4.
The medium transport roller is driven by a motor capable of forward and reverse rotation and stop restraint,
The shutter is
When the medium transport roller rotates in the reverse direction, the shutter moves from the shutter closed state to the shutter open state,
When the medium conveying roller is in a stop restrained state, the shutter opening state is maintained,
An image forming apparatus that maintains the shutter closed state by returning to the shutter closed state by the biasing when the medium conveying roller is in neither the reverse rotation nor the stop restrained state. The image forming apparatus according to claim 5.
The medium conveying roller is
The motor can control the rotation angle during the reverse rotation,
The image forming apparatus that is driven and controlled so that the rotation shaft of the shutter is rotated by a rotation angle necessary for the shutter to shift from the shutter closed state to the shutter open state during the reverse rotation. . The image forming apparatus according to claim 1,
The sensor is an image forming apparatus configured with a reflective optical sensor. The image forming apparatus according to claim 1,
The image forming apparatus, wherein the sensor is disposed in proximity to the intermediate transfer belt. The image forming apparatus according to claim 1,
The image forming apparatus, wherein the toner image to be inspected by the sensor is a registration mark indicating a reference pattern for inspection.

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