JP4100369B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus provided with a mechanism that detects metal adhering to a recording sheet by a metal sensor and prevents damage to internal components when the recording sheet is conveyed.

Conventionally, a copying machine or a printer has a built-in mechanism for transporting a recording medium for printing, and the recording medium is transported inside the apparatus by the mechanism.
However, if a metal such as a clip or a staple adheres to the recording medium to be transported, a component (for example, a photoconductive drum in the case of a laser printer) that is in the transport path with the metal during the transport of the recording medium Or the intermediate transfer belt) may be damaged.

In order to prevent this, a mechanism that prevents the damage of the components by providing a metal sensor in the middle of the transport path and stopping the transport of the record medium when the metal adhering to the record medium is detected. For example, a mechanism has been proposed in which the conveyance path of the recording medium is changed and the recording medium is discharged without forming an image to prevent damage to the components. (For example, see Patent Document 1)
JP-A-8-91602

  However, when a mechanism for stopping the conveyance of a recording medium when an adhering metal is detected is applied to, for example, a network printer in which one printer is shared by a plurality of computers, the components inside the network printer are damaged. However, there is a problem in that the network printer is stopped and the printing process is delayed, so that the usability is not good.

  In addition, when a mechanism that changes the transport path of the recording medium and ejects it when the adhered metal is detected is applied to the printer, the recording medium to which the metal adheres is ejected in addition to the normal transport path. For this reason, there is a problem in that it is necessary to provide a transport path for the printer, which leads to an increase in the size of the printer.

  SUMMARY An advantage of some aspects of the invention is that it provides a compact and easy-to-use compact image forming apparatus that does not damage internal components due to metal-attached recording paper.

  In order to achieve the above object, the invention according to claim 1 forms an image at a conveying means for conveying the recording medium along the conveying path and an image forming position on the conveying path. An image forming apparatus comprising: an image forming unit; a metal detecting unit that is disposed upstream of the image forming position in the transport path and detects metal adhering to the recording medium; The distance changing means for changing the distance between the image forming means and the recording medium at the forming position, and the metal detecting means detects the metal adhering to the recording medium. And a control means for increasing the distance between the recording medium and the recording medium.

According to the image forming apparatus configured as described above, when a metal such as a clip or a staple attached to the recording medium is detected, the distance between the image forming unit and the recording medium at the image forming position is changed. Thus, it is possible to prevent the image forming unit from being damaged by the metal. Further, it is possible to discharge the recording medium to which the metal is attached without stopping the image forming apparatus, and the usability of the image forming apparatus is improved. Furthermore, since it is not necessary to provide a separate delivery path for the recording medium to which the metal is attached, it is possible to prevent the image forming apparatus from becoming large.
In addition, the image forming means forms an electrostatic latent image forming means for forming an electrostatic latent image, and development for forming a developer image by attaching a developer to the electrostatic latent image formed by the electrostatic latent image forming means. And a transfer means for transferring the developer image carried on the image carrier to a recording medium, and the control means uses the distance changing means to control the image carrier. And the distance between the transfer means and the transfer means.
In this way, when the metal adhering to the recording medium is detected, the control unit changes the distance between the image carrier and the transfer unit, so that the image carrier and the transfer unit are not damaged by the metal.
In addition, a pair of conveyance auxiliary rollers are provided between the transfer unit and the fixing unit arranged on the conveyance path, and further, the apparatus includes a conveyance auxiliary roller control unit that controls the conveyance auxiliary roller. When the metal adhering to the recording medium is detected, the conveyance auxiliary roller sandwiches the recording medium and conveys the recording medium. When the metal is not detected, the conveyance auxiliary roller separates from the recording medium and the recording medium is recorded. I am trying not to carry out.
In this way, when the metal is not attached to the recording medium, the conveyance auxiliary roller is separated, so that the conveyance auxiliary roller contacts the unfixed developer image and disturbs the developer image. Disappears. On the other hand, when metal is attached, the recording medium can be conveyed by the conveyance auxiliary roller.
That is, in an image forming apparatus that performs image formation by transferring a developer image to a recording medium, the developer carrying member and the transfer means rotate while abutting to rotate, and simultaneously transfer the developer image. If the distance between the image carrier and the transfer means is changed when the metal detection means detects the metal adhering to the recording medium, which is caused by conveying the recording medium, the recording medium cannot be conveyed. The case is gone.

  By the way, when detecting the metal adhering to the recording medium and changing the distance between the image forming means and the recording medium at the image forming position, it is not necessary to detect the metal and immediately increase the distance. According to a second aspect of the present invention, the control unit may control the distance between the image forming unit and the recording medium to be increased before the metal reaches the image forming position of the image forming unit.

  In this way, it is possible to secure a sufficient processing time for moving the image forming unit from the image forming position by a predetermined distance from the detection of the metal by the metal detecting unit.

Further, a developing means is provided for each of the plurality of color developers, and the image carrier is an intermediate transfer body that carries a developer image developed by the plurality of developing means, and the transfer means is an intermediate transfer member. In the case of an image forming apparatus configured to transfer an image formed on a body to a recording medium, as described in claim 3 , the control means includes an intermediate transfer body, a transfer means, It is better to change the distance.

  In this way, it is generally possible to prevent damage to the intermediate transfer member, which is a component that has a longer life than a photosensitive drum, and thus the life of the image forming apparatus can be extended.

In addition, in an image forming apparatus provided with a fixing unit that fixes a developer image transferred onto a recording medium onto the recording medium, if a metal adheres to the recording medium, the image carrier of the image forming unit In addition to the intermediate transfer member, the fixing means may be damaged. Therefore, in order to prevent this problem, the image forming apparatus is further covered with a nip releasing means for releasing the holding state of the recording medium by the fixing means and a metal detecting means as described in claim 4. It is preferable to provide a nip release control means for releasing the nipping state of the recording medium when the metal adhering to the recording medium is detected.

With this configuration, the fixing unit is not damaged by the metal, and the life of the fixing unit can be extended.
On the other hand, the nip releasing control means, as claimed in claim 5, the metal adhering to the recording medium by the metal detecting means is detected, whether the developer image is transferred onto the recording medium If the developer image is not transferred to the recording medium, the nip releasing means releases the nipping state of the recording medium. If the developer image is transferred to the recording medium, the nip releasing means Therefore, it is preferable that the sandwiched state of the recording medium is not released.

  With this configuration, when the developer image is not formed on the recording medium, the nip is released to release the state where the recording medium is held by the fixing unit, and the fixing unit is damaged by metal. Can be prevented. On the other hand, when the developer image is formed on the recording medium, the developer image is fixed without releasing the nip, and the contamination by the unfixed developer can be prevented.

According to a sixth aspect of the present invention, when the control unit increases the distance between the image carrier and the transfer unit, the auxiliary roller control unit controls the conveyance auxiliary roller so as to sandwich the recording medium. It may be.

  In this case, even if the distance between the image carrying unit and the transfer unit is increased because the metal adheres to the recording medium, the conveyance auxiliary roller sandwiches the recording medium and conveys the recording medium. To do. Therefore, the recording medium to which the metal is attached can be transported without damaging the image carrier and the transfer means.

In the image forming apparatus provided with the conveyance auxiliary roller in the conveyance path, as described in claim 7 , the conveyance unit is provided on the upstream side of the image forming position for conveying the recording medium. A pair of front conveyance rollers is provided, and the distance between the front conveyance roller and the conveyance auxiliary roller along the conveyance path is smaller than the length in the conveyance direction of the smallest recording medium capable of forming an image. The conveying means may be configured as described above.

  With this configuration, the metal detection unit detects the metal adhering to the recording medium, and the transfer unit can change the distance between the image carrier unit and the transfer unit, so that the recording medium can be conveyed. Even if it disappears, the recording medium can be conveyed by the front conveyance roller and the conveyance auxiliary roller.

Further, according to the eighth aspect of the present invention, as a conveying unit, a pair of rear conveyance rollers for conveying the recording medium is provided on the downstream side of the fixing unit, and a conveyance path between the rear conveyance roller and the conveyance auxiliary roller. The conveying means may be configured such that the distance along the direction becomes smaller than the length in the conveying direction of a recording medium having a minimum size capable of forming an image.

  With this configuration, even if the metal detection unit detects the metal adhering to the recording medium and the fixing unit releases the nip release unit, the fixing unit can no longer transport the recording medium. The recording medium can be conveyed by the auxiliary roller and the rear conveying roller.

Further, in the image forming apparatus according to any one of claims 1 to 8 , when the metal adhering to the recording medium is detected by the metal detecting means as described in claim 9 , the image is formed. It is preferable to provide image forming operation prohibiting means for prohibiting the image forming operation of the forming means.

With this configuration, the developer and ink are not wasted when the metal adheres to the recording medium.
By the way, in the image forming apparatus according to any one of claims 1 to 9 , when the metal is detected in the recording medium by the metal detection unit, the recording medium is unloaded. After discharging, it is preferable that image formation can be resumed. For this purpose, as described in claim 10 , image re-formation command means for instructing the image forming means to form the same image again on a new recording medium is provided. Good.

  With this configuration, even when metal is attached to the recording medium, the recording medium is unloaded and the image forming process for the same image is performed on the new recording medium. It is not stopped and the usability of the image forming apparatus is improved.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view showing a schematic configuration of a color laser printer 1 to which the present invention is applied, and FIG. 2 is an explanatory view showing the arrangement positions of components in a transport unit 9 described later.

  In FIG. 1, a color laser printer 1 is a so-called horizontal type tandem color laser printer in which four image forming units 20 described later are arranged in a horizontal direction. A transport unit 9 for transporting a recording paper 3 as a recording medium, an image forming unit 4 for forming an image on the fed recording paper 3, and a paper for discharging the recording paper 3 on which the image is formed A paper discharge unit 6 and a control unit 90 that controls the operation of the color laser printer 1 are provided.

  The transport unit 9 is disposed from the bottom in the main body casing 2 to the upper rear part, and can be detached from the front side of the main body casing 2 (in FIG. 1, the right direction in the drawing is referred to as the front and the left direction is referred to as the rear). A paper feed tray 12 mounted on the paper feed tray, a paper feed roller 83 provided above one end (upper front side) of the paper feed tray 12, and a paper feed roller 83 above the paper feed roller 83 and recording on the paper feed roller 83. A pair of sheets provided on the downstream side in the conveyance direction of the paper 3 (hereinafter, the downstream side in the conveyance direction of the recording paper 3 may be abbreviated as the downstream side in the conveyance direction, and the upstream side in the conveyance direction of the recording paper 3 may be abbreviated as an upstream side in the conveyance direction). A front conveyance roller 14 and a downstream side of the front conveyance roller 14, and a pair of conveyance auxiliary rollers 64, a fixing unit 8, and a paper discharge roller 11 between a secondary transfer unit 18 and a fixing unit 8 described later. A pair of rear conveying rollers, Between the paper roller 83 and the front conveying roller 14, a metal sensor 66 for detecting a metal adhering to the recording paper 3, a.

  As shown in FIG. 2, the front conveyance roller 14 and the conveyance auxiliary roller 64 have a length La between the two rollers along the conveyance path that is smaller than the length in the conveyance direction of the recording paper 3. It is arranged to become. Further, the conveyance auxiliary roller 64 and the rear conveyance roller 65 are arranged such that the length Lb along the conveyance path between the two rollers is smaller than the length in the conveyance direction of the recording paper 3. . Further, the secondary transfer unit 18 and the fixing unit 8 are conveyed by a contact portion between the intermediate transfer belt driving roller 75 and the secondary transfer roller 63 and a contact portion between the heating roller 81 and the pressure roller 82. The length Lc along the path is arranged to be smaller than the length of the recording paper 3 in the transport direction.

  The conveyance auxiliary roller 64 includes a so-called nip mechanism in which a conveyance auxiliary roller nip release solenoid 86 (see FIG. 3) moves the rotation shaft of one of the rollers to separate the contact portions of the paired rollers. ing.

  The metal sensor 66 has a detection width that is the same as the lateral width of the transport path, and is a magnetic sensor formed by winding a coil or an ultra-small magnetic sensor chip (for example, MI-IC- manufactured by Aichi Steel Corporation). 2DL) is used so as to cover the width of the transport path.

  The recording paper 3 is stacked in the paper feed tray 12, and the uppermost recording paper 3 is fed toward the front transport roller 14 one by one by the rotation of the paper feed roller 83. Then, the sheet is sequentially fed from the front conveying roller 14 between the intermediate transfer belt 74 (image carrier in the present invention) and the secondary transfer roller 63 (transfer position).

  A guide member 15 disposed in the vertical direction is provided between the paper feed roller 83 and the front transport roller 14, and the recording paper 3 fed by the paper feed roller 83 is a guide member. 15 is sequentially sent between the intermediate transfer belt 74 and the secondary transfer roller 63 (secondary transfer position), and is then sent to the fixing unit 8 by the conveyance auxiliary roller 64, and further, the rear conveyance roller 65 and the paper discharge roller 11. Is conveyed to the paper discharge tray 10.

  The image forming unit 4 transfers the images formed by the four image forming units 20Y, 20M, 20C, and 20K that form images and the image forming units 20 to the intermediate transfer belt 74 in the intermediate portion in the main casing 2. And a secondary transfer unit 18 that transfers the image transferred to the intermediate transfer belt 74 to the recording paper 3.

  Each image forming unit 20 includes a photosensitive drum 62, a charger 31 that charges the photosensitive drum 62 around the photosensitive drum 62, and an electrostatic latent image formation that forms an electrostatic latent image on the photosensitive drum 62. A scanner unit 41 as a means and a developing unit 51 as a developing means for forming a developer image by attaching a developer to the photosensitive drum 62 are arranged. In FIG. 1, each image forming unit 20 has the same structure except that the color of the developer is different. Therefore, the reference numerals for the respective constituent elements are described only for the black (K) image forming unit 20K, and other images. About the formation unit 20, the description of the code | symbol is abbreviate | omitted.

  The charger 31 is, for example, a scorotron charger for positive charging that generates corona discharge from a charging wire made of tungsten or the like and uniformly charges the surface of the photosensitive drum 62 to positive polarity.

The scanner unit 41 includes a laser generator that generates laser light for forming an electrostatic latent image on the surface of the photosensitive drum 62, a lens (none of which are shown), and the like.
In the scanner unit 41, laser light emitted from the laser light emitting unit is scanned and irradiated on the photosensitive drum 62 to form an electrostatic latent image on the surface of the photosensitive drum 62.

The developing unit 51 includes a developer hopper 56 as a developer container, a supply roller 32 as a developer supply means, and a development roller 52.
The developer hopper 56 accommodates yellow (Y), magenta (M), cyan (C), and black (K) developers for each image forming unit 20.

  That is, in the four image forming units 20 described above, the image forming unit 20Y in which the developer hopper 56 contains yellow (Y) developer and the developer hopper 56 contains magenta (M) developer. Image forming unit 20M, image forming unit 20C in which cyan (C) developer is stored in developer hopper 56, and image forming unit 20K in which developer (hopper) 56 stores black (K) developer. It is configured.

  The supply roller 32 is disposed on the developer hopper 56 obliquely forward and downward, and a roller portion made of a conductive sponge member is coated on a metal roller shaft. The supply roller 32 is rotatably supported so as to rotate in a direction opposite to the developing roller 52 at a nip portion facing and contacting the developing roller 52.

  The developing roller 52 is rotatably disposed below the supply roller 32 at a position facing and in contact with the supply roller 32. The developing roller 52 is formed by covering a metal roller shaft with a roller portion made of an elastic member such as a conductive rubber material.

  The primary transfer unit 17 is provided inside the main casing 2 so as to face the photosensitive drum 62 on the opposite side of the developing unit 51. The primary transfer unit 17 includes an intermediate transfer belt driving roller 75, an intermediate transfer belt driven roller 76, an intermediate transfer belt 74 that is an endless belt, and a primary transfer roller 61.

  The intermediate transfer belt driving roller 75 is disposed in front of the photosensitive drum 62 of the image forming unit 20 </ b> Y on the most upstream side with respect to the circumferential direction of the intermediate transfer belt 74 and on the upper front side of the paper feed roller 83. . Further, the intermediate transfer belt driven roller 76 is disposed behind the photosensitive drum 62 of the black image forming unit 20K on the most downstream side with respect to the circumferential direction of the intermediate transfer belt 74.

  The intermediate transfer belt 74 is wound between an intermediate transfer belt driving roller 75 and an intermediate transfer belt driven roller 76. The intermediate transfer belt 74 is disposed such that the outer surface around which the intermediate transfer belt 74 is wound faces and contacts all the photosensitive drums 62 of the image forming units 20.

  The intermediate transfer belt driven roller 76 is driven by the drive of the intermediate transfer belt driving roller 75, and the intermediate transfer belt 74 is interposed between the intermediate transfer belt driven roller 75 and the intermediate transfer belt driven roller 76 in each image forming unit 20. The photosensitive drum 62 rotates counterclockwise so as to rotate in the same direction as the photosensitive drum 62 on the contact surface facing the photosensitive drum 62.

  Further, the primary transfer roller 61 is disposed inside the intermediate transfer belt 74 wound so as to face the photosensitive drum 62 of each image forming unit 20 with the intermediate transfer belt 74 interposed therebetween. . The primary transfer roller 61 is rotatably provided in the counterclockwise direction so that the primary transfer roller 61 rotates in the same direction as the circumferential movement direction of the intermediate transfer belt 74 on the contact surface facing the intermediate transfer belt 74.

  At the time of transfer, a transfer bias having a predetermined current value is applied between the photosensitive drum 62 and the intermediate transfer belt 74 from a power source (not shown), and the photosensitive drum 62 carries the transfer bias by this transfer bias. The developer image is transferred (primary transfer) to the intermediate transfer belt 74.

The secondary transfer unit 18 includes an intermediate transfer belt drive roller 75, a secondary transfer roller 63, an intermediate transfer belt 74, and a cleaning mechanism 100.
The secondary transfer roller 63 is disposed so as to face the intermediate transfer belt driving roller 75 with the intermediate transfer belt 74 interposed therebetween. The secondary transfer roller 63 is formed by covering a metal roller shaft with a roller portion made of an elastic member such as a conductive rubber material.

  The secondary transfer roller 63 is provided to be rotatable in the clockwise direction so that the secondary transfer roller 63 rotates in the same direction as the circumferential movement direction of the intermediate transfer belt 74 on the contact surface facing the intermediate transfer belt 74. Sometimes, a transfer bias having a predetermined current value is applied between the secondary transfer roller 63 and the intermediate transfer belt 74 from a power source (not shown), and the developer image carried on the intermediate transfer belt 74 is transferred to the recording paper 3. (Secondary transfer).

  The cleaning mechanism 100 is configured to remove and collect the developer remaining on the intermediate transfer belt 74 after being secondarily transferred to the recording paper 3 by adsorbing it with an electrostatically charged roller.

  Further, the secondary transfer unit 18 moves the rotation shaft of the secondary transfer roller 63 by a secondary transfer unit nip release solenoid 84 (see FIG. 3) so that the secondary transfer roller 63 and the intermediate transfer belt 74 are in contact with each other. A so-called nip mechanism for separating the portions is provided.

  The fixing unit 8 is disposed in front of the image forming unit 20 and above the secondary transfer unit 18 on the downstream side in the transport direction. The fixing unit 8 includes a heating roller 81 and a pressure roller 82. The heating roller 81 is made of a metal base tube having a release layer formed on the surface thereof, and a halogen lamp is provided along the axial direction thereof. Then, the surface of the heating roller 81 is heated to the fixing temperature by the halogen lamp. Further, the pressure roller 82 is disposed to face the heating roller 81 so as to be pressed by the heating roller 81.

  Further, the fixing unit 8 moves the rotation shaft of the pressure roller 82 by a fixing unit nip release solenoid 85 (see FIG. 3), and separates the contact portion between the pressure roller 82 and the heating roller 81. A nip mechanism is provided.

The developer image secondarily transferred onto the recording paper 3 by the fixing unit 8 is heated and pressurized and fixed on the surface of the recording paper 3.
The paper discharge unit 6 is disposed on the downstream side in the transport direction of the fixing unit 8 in the upper part of the main body casing 2. The paper discharge unit 6 is provided with a pair of paper discharge rollers 11 for discharging the recording paper 3 on which image fixing has been completed, and a downstream side of the paper discharge rollers 11. A paper discharge tray 10 for accumulating the recording paper 3 discharged from the paper roller 11 is provided.

  Next, while explaining the electrical configuration of the color laser printer 1 with reference to FIG. 3, the process until the color laser printer 1 forms a color image on the recording paper 3 by the above-described cooperative operation of each unit in the apparatus. explain. FIG. 3 is a block diagram schematically showing the electrical configuration of the color laser printer 1.

  As shown in FIG. 3, the color laser printer 1 includes a control unit 90 (including a CPU, ROM, RAM, I / O, driver, etc.) that controls each part of the apparatus, an image forming unit 20, and a secondary transfer nip release solenoid. 84, a fixing unit nip release solenoid 85, a conveyance auxiliary roller nip release solenoid 86, each roller drive motor 87, and a metal sensor 66. The control unit 90 is configured to perform an image forming operation.

  Each roller drive motor 87 receives a drive signal from the control unit 90 and drives each roller provided in the image forming unit 4, the paper discharge unit 6, the fixing unit 8, and the transport unit 9 via a gear. Motor.

  In the image forming operation, the control unit 90 of the color laser printer 1 performs initial setting of each unit to be controlled at the time of image formation by a main control processing unit (program), and then charges the surface of the photosensitive drum 62 with a charger. An electrostatic latent image is formed on the surface of the photosensitive drum 62 by being uniformly charged by the laser 31 and irradiating a laser beam modulated in accordance with image information from the scanner unit 41. Next, a developer is applied to the surface of the photosensitive drum 62 by the developing unit 51, and the electrostatic latent image on the surface of the photosensitive drum 62 is visualized. Then, the photosensitive drum 62 is rotated to move the visualized visible image (developer image) to the primary transfer position.

  Next, the control unit 90 rotates the intermediate transfer belt driving roller 75 to rotate the intermediate transfer belt 74, and a primary bias between each photosensitive drum 62 and the intermediate transfer belt 74 by a power source (not shown). A voltage is applied to transfer the visible image (developer image) on the photosensitive drum 62 to the intermediate transfer belt 74 (primary transfer).

  Further, the control unit 90 supplies the visible image (developer image) transferred to the intermediate transfer belt 74 to the secondary transfer unit 18 so that the recording paper 3 is supplied to the secondary transfer unit 18 at the same time. The recording roller 3 is fed by operating the paper roller 83 and the front conveyance roller 14. In the secondary transfer unit 18, a secondary transfer bias voltage is applied between the secondary transfer roller 63 and the intermediate transfer belt 74 by a power source (not shown), and a visible image (developer image) is transferred to the recording paper 3. To do.

  Next, the control unit 90 causes the fixing unit 8 to sandwich and convey the recording paper 3 between the heating roller 81 and the pressure roller 82, and heat and press the visible image (developer image) on the recording paper 3 to record the recording paper. 3 to fix. Then, the rear conveyance roller 65 and the paper discharge roller 11 are operated to discharge the recording paper 3 to the paper discharge tray 10 above the main body casing 2, and the image forming operation is completed.

  By the way, in the color laser printer 1 of this embodiment, when the metal sensor 66 detects a metal such as a clip or a staple attached to the recording paper 3, the intermediate transfer belt 74 and the fixing unit 8 are damaged by the metal. Do not operate.

  The operation will be described below with reference to FIGS. 4, 5 and 6. 4 is a flowchart of a main process executed by the control unit 90, FIG. 5 is a flowchart of an interrupt process during metal detection called during the main process, and FIG. 6 is a schematic enlarged view of the transport unit 9.

  The control unit 90 starts processing when the color laser printer 1 is powered on, and after performing initial processing necessary for the operation of the color laser printer 1 in S110, the process proceeds to S115. In S115, it is determined whether or not image data has been received. If there is a reception (Yes in S115), the process proceeds to S120. If there is no reception (No in S115), the reception of the image data is repeated.

  In S120, it is determined whether or not one page of image data has been received. If the reception has been completed (Yes in S120), the process proceeds to S125. If the reception has not been completed (No in S120). ) Return to S115 and repeat the reception of the image data.

In S125, the received image data for one page is developed into data for each color for image formation by each image forming unit 20. Then, the process proceeds to S130.
In S130, an interrupt at the time of metal detection is enabled, and an interrupt process is executed when the metal adhering to the recording paper 3 is found by the metal sensor 66. Then, the process proceeds to S135.

  In S135, the normal printing process described above is performed, and if the metal sensor 66 does not detect the metal, the process proceeds to S140 at the end of the normal printing process, and the interrupt at the time of metal detection is set to disable. The interruption is prohibited, and the process returns to S115 to wait for reception of the next image data.

  On the other hand, when the metal sensor 66 detects the metal adhering to the recording paper 3 during the period from enabling the interrupt in S130 to disabling the interrupt in S140, the interrupt process shown in FIG. 5 is executed.

  In the interrupt processing of S210, first, in S215, in order to prohibit another interrupt from being generated during execution of the interrupt processing, the interrupt is disabled, and the process proceeds to S220.

In S220, the image forming process below exposure by the scanner unit 41 is stopped, and the process proceeds to S225.
Note that when the metal is detected by the metal sensor 66, even if an image is further formed and the developer image is carried on the intermediate transfer member 74, it is only collected by the cleaning mechanism 100. Therefore, the image formation is stopped in S220, and the burden on the cleaning mechanism 100 is reduced as much as possible.

  In S225, the time required for the recording paper 3 to pass through a distance obtained by subtracting the transfer margin corresponding to the margin of the recording paper from the distance between the metal sensor 66 and the secondary transfer portion 18 (that is, {(metal sensors 66 to 2). The recording paper 3 is transported by driving the paper feed roller 83 and the front transport roller 14 for the time obtained by (distance between next transfer portions 18−transfer margin) / conveying speed of the recording paper 3}. Then, the process proceeds to S230.

  Note that while the recording paper 3 passes through a distance obtained by subtracting a transfer margin corresponding to the margin of the recording paper from the distance between the metal sensor 66 and the secondary transfer unit 18, the metal detected by the metal sensor 66 is secondary. Since it does not reach the transfer position, it is preferable to transfer the developer image on the intermediate transfer belt 74 to the recording paper 3 as much as possible to reduce the burden on the cleaning mechanism 100.

  In addition, a transfer margin is provided in order to avoid a situation where a metal contacts the secondary transfer portion 18 and damages the intermediate transfer belt 74 and the secondary transfer roller when the recording paper 3 is transferred to the full size at the time of transfer. It is.

In S230, before the nip mechanism of the secondary transfer unit 18 is operated in S235 described later, the conveyance auxiliary roller nip release solenoid 86 of the nip mechanism of the conveyance auxiliary roller 64 is operated, and the recording paper 3 is sandwiched by the conveyance auxiliary roller 64. 6 (a) shows the movement of the conveyance auxiliary roller 64 at this time, and sandwiches the recording paper 3 passing through the secondary transfer unit 18,
It is conveyed to the fixing unit 8. Then, the process proceeds to S235.

In S235, after the nip mechanism of the auxiliary conveyance roller 64 is operated in S230, the secondary transfer unit nip release solenoid 84 of the nip mechanism of the secondary transfer roller 63 of the secondary transfer unit 18 is operated to perform the secondary transfer. The roller 63 is separated from the intermediate transfer belt 74 (the movement of the secondary transfer roller 63 is shown in FIG. 6A), and the process proceeds to S240. By this separation operation, the portion of the recording paper 3 to which the metal has adhered passes through the secondary transfer portion 18 without damaging the intermediate transfer belt 74.

Note that after the separation operation of the secondary transfer portion 18 is performed, the developer image remaining on the intermediate transfer belt 74 is collected by the cleaning mechanism 100.
In S240, the transfer margin is added to the distance between the secondary transfer unit 18 and the fixing unit 8 and the recording paper 3 passes the distance obtained by subtracting the fixing margin (that is, {(secondary transfer unit 18 to fixing unit). 8), the front conveyance roller 14 and the conveyance auxiliary roller 64 are driven to convey the recording sheet 3 to the fixing unit for the time obtained by (distance between 8 + transfer margin−fixing margin) / conveying speed of the recording sheet 3). Then, the process proceeds to S245.

In S245, the fixing unit nip release solenoid 85 of the nip mechanism of the fixing unit 8 is activated to separate the pressure roller 82 from the heating roller 81 (FIG. 6A shows the movement of the pressure roller 82 at this time. ), And the process proceeds to S250. By this separation operation, the recording paper 3 to which the metal has adhered passes through the fixing unit 8 without damaging the heating roller 81 and the pressure roller 82.

  Note that the developer image formed on the recording paper 3 before the metal is detected on the recording paper 3 by the metal sensor 66 by the processing in S240 and S245 is fixed by the fixing unit 8. In the fixing unit 8, the separation operation is performed immediately before the metal reaches the fixing unit.

  In S250, only the time until the recording paper 3 passes through the fixing unit 8 and is discharged by the paper discharge roller 11 (that is, the time obtained by (recording paper 3 / recording paper 3 conveyance speed)), The conveyance auxiliary roller 64, the rear conveyance roller 65, and the paper discharge roller 11 are operated to discharge the recording paper 3 to the paper discharge tray 10. Then, the process proceeds to S255.

  In S255, the operation of the secondary transfer unit nip release solenoid 84 of the nip mechanism of the secondary transfer roller 63 of the secondary transfer unit 18 is released, the secondary transfer roller 63 is brought into contact with the intermediate transfer belt 74, and the process proceeds to S260. To do.

  In S260, the operation of the fixing unit nip release solenoid 85 of the nip mechanism of the pressure roller 82 of the fixing unit 8 is released, the pressure roller 82 is brought into contact with the heating roller 81, and the process proceeds to S265.

  In S265, the operation of the conveyance auxiliary roller nip release solenoid 86 of the conveyance auxiliary roller 64 nip function is canceled so that the conveyance auxiliary roller 64 does not pinch the recording paper 3, and the process proceeds to S270.

In S270, in order to enable the interrupt process when the metal sensor 66 detects the metal, the interrupt is enabled, the interrupt process is terminated, and the process proceeds to the main process.
In the main process, after the interruption process is completed, the process returns to the point A and S135 is executed. In S135, the image forming process that was canceled during the interrupt process is executed again, the image is re-formed, and the normal print process is executed. Accordingly, after the recording paper 3 with the metal attached is discharged, reprinting is automatically executed.

  Note that the processing in S215 to S220 corresponds to the image forming operation prohibiting means in the present invention, the processing in S235 and S255 corresponds to the control means, the processing in S245 and 260 corresponds to the nip release control means, The process in S135 after the execution of the interrupt process in S210 corresponds to the image re-formation command unit, and the processes in S230 and S265 correspond to the conveyance auxiliary roller control unit.

  As described above, in the color laser printer 1 according to the present embodiment, when the metal sensor 66 detects that metal is attached to the recording paper 3, the secondary transfer roller 63 is moved to the intermediate transfer belt 74 by the secondary transfer unit 18. Further, since the pressure roller 82 is separated from the heating roller by the fixing unit 8, when the recording sheet 3 passes through the secondary transfer unit 18 and the fixing unit 8, it adheres to the recording sheet 3. It is possible to prevent the intermediate transfer belt 74, the secondary transfer roller 63, the heating roller 81, and the pressure roller 82 from being damaged by the metal present.

In addition, when metal is detected, the image forming process is stopped, so that an unnecessary developer is not used.
Further, since the reprinting is automatically executed after the recording paper 3 to which the metal is attached is discharged, even when the color laser printer 1 is shared by a plurality of computers, it does not stop and is easy to use. Will improve.

  By the way, in this embodiment, when the metal adhering to the recording paper 3 is detected, the fixing unit nip releasing solenoid 85 of the nip mechanism of the fixing unit 8 is operated in S245, and the pressure roller 82 is moved from the heating roller 81. The heating roller 81 and the pressure roller 82 are prevented from being damaged by the metal adhering to the recording paper 3 apart from each other. In this case, the recording paper is detected until the metal formation is detected and the image formation is stopped. When the developer image is formed on the sheet 3, the developer image is not fixed. Therefore, there is a possibility that the already-printed recording paper in the discharge tray 10 or the discharge tray 10 may be stained after the discharge. .

In order to prevent this, the processes of S245 and S260 are not performed, and the pressure roller 82 is not separated from the heating roller 81 (FIG. 6B shows the state of the transport unit 9 at that time). . In this way, the developer image is fixed by the fixing unit 8 even when metal is attached to the recording paper 3, so that the heating roller 81 and the pressure roller 82 are deteriorated. There is no possibility that the already printed recording paper in the paper tray 10 or the paper discharge tray 10 is soiled.

  As mentioned above, although the Example of this invention was described, it cannot be overemphasized that embodiment of this invention can take various forms, as long as it belongs to the technical scope of this invention, without being limited to the said Example at all. Nor.

  For example, the present invention may be applied to a color laser printer that employs a direct tandem system in which a developer image formed on a photosensitive drum is directly transferred to a recording sheet 3 that is conveyed by a conveyance belt. Further, the present invention may be applied to a four-cycle color laser printer that superimposes four color developer images on an intermediate transfer member and then transfers them onto a recording sheet.

  In this case, in the case of the direct tandem system, the photosensitive drum corresponds to the image carrier of the present invention, and in the case of the 4-cycle system, the intermediate transfer body corresponds to the image carrier of the present invention.

  Moreover, not only a color laser printer but a monochrome laser printer may be used. In the monochrome laser printer, the photosensitive drum corresponds to the image carrier of the present invention.

In addition to the laser printer, a so-called LED printer in which exposure is performed by an LED (light emitting diode) may be used.
Furthermore, as long as the apparatus uses an image forming apparatus, the present invention is not limited to a printer. For example, a copying apparatus including an original reading apparatus that electronically reads an original or a facsimile apparatus including a communication unit may be used. By applying the invention, the same effects as described above can be obtained.

  In addition, even in a printer using an inkjet method or a thermal method as an image forming unit, the present invention is applied to prevent damage to the nozzle or the heating mechanism by moving the inkjet nozzle unit or the heating mechanism from the recording paper. It becomes possible to do.

  In this embodiment, the nip is released by moving the secondary transfer roller 63 in the secondary transfer unit 18 and moving the pressure roller 82 in the fixing unit 8. In the transfer section for transferring the image, an image carrier (developer drum in the direct tandem system or monochrome laser system, and an intermediate transfer body in the 4-cycle system) carrying the developer may be moved. In the fixing unit 8, the heating roller 81 may be moved.

1 is an explanatory diagram illustrating a schematic configuration of a color laser printer 1 of Example 1. FIG. FIG. 2 is a diagram illustrating a positional relationship of each device regarding a conveyance path of the color laser printer 1. 2 is a block diagram schematically illustrating an electrical configuration of the color laser printer 1. FIG. It is a flowchart of the main process which the control part 90 performs. It is a flowchart of the interruption process at the time of the metal detection which transfers from a main process. FIG. 3 is an enlarged view of a portion related to a conveyance path of the color laser printer 1.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Color laser printer, 2 ... Main body casing, 3 ... Recording paper, 4 ... Image formation part, 6 ... Paper discharge part, 8 ... Fixing part, 9 ... Conveyance part, 10 ... Paper discharge tray, 11 ... Paper discharge roller, DESCRIPTION OF SYMBOLS 12 ... Paper feed tray, 14 ... Front conveyance roller, 15 ... Guide member, 17 ... Primary transfer part, 18 ... Secondary transfer part, 20, 20Y, 20M, 20C, 20K ... Image forming unit, 31 ... Charger, 32 ... Supply roller, 41 ... Scanner unit, 51 ... Developing unit, 52 ... Developing roller, 55 ... Developing casing, 56 ... Developer hopper, 61 ... Primary transfer roller, 62 ... Photosensitive drum, 63 ... Secondary transfer roller, 64 ... Auxiliary conveyance roller, 65 ... Rear conveyance roller, 66 ... Metal sensor, 74 ... Intermediate transfer belt, 75 ... Intermediate transfer belt drive roller, 76 ... Intermediate transfer belt driven roller, 81 ... Heating roller, 8 DESCRIPTION OF SYMBOLS ... Pressure roller, 83 ... Paper feed roller, 84 ... Secondary transfer part nip release solenoid, 85 ... Fixing part nip release solenoid, 86 ... Conveyance auxiliary roller nip release solenoid, 87 ... Each roller drive motor, 90 ... Control part, 100 ... Cleaning mechanism

Claims (10)

Transport means for transporting the recording medium along the transport path;
Image forming means for forming an image at an image forming position on the transport path;
An image forming apparatus comprising:
A metal detecting means disposed on the upstream side of the image forming position in the transport path for detecting metal adhering to the recording medium;
Distance changing means for changing the distance between the image forming means and the recording medium at the image forming position;
Control means for increasing the distance between the image forming means and the recording medium by the distance changing means when the metal adhering to the recording medium is detected by the metal detecting means;
Equipped with a,
The image forming unit includes:
An electrostatic latent image forming means for forming an electrostatic latent image;
Developing means for forming a developer image by attaching a developer to the electrostatic latent image formed by the electrostatic latent image forming means;
An image carrier for carrying a developer image;
Transfer means for transferring the developer image carried on the image carrier to the recording medium;
With
The control means includes
The distance changing means changes the distance between the image carrier and the transfer means,
The transport unit includes a pair of transport auxiliary rollers provided between the transfer unit and the fixing unit in the transport path,
In the apparatus, when the metal adhering to the recording medium is detected by the metal detection means, the conveyance auxiliary roller sandwiches the recording medium and conveys the recording medium. A conveyance auxiliary roller control means for controlling the conveyance auxiliary roller so as to control the conveyance auxiliary roller so that the conveyance auxiliary roller is separated from the recording medium and does not convey the recording medium when metal is not detected. ,
An image forming apparatus comprising: The control means includes
When the metal adhering to the recording medium is detected by the metal detecting means, the distance between the image forming means and the recording medium is increased until the metal reaches the image forming position. The image forming apparatus according to claim 1. The developing means is provided for each developer of a plurality of colors,
The image carrier is an intermediate transfer member that carries the developer image developed by the plurality of developing units,
The transfer means transfers the image formed on the intermediate transfer member to the recording medium,
The image forming apparatus according to claim 1 , wherein the control unit changes a distance between the intermediate transfer member and the transfer unit by the distance changing unit. A fixing unit that is disposed on the downstream side of the image forming position in the transport path, sandwiches the recording medium, and fixes the developer image transferred onto the recording medium onto the recording medium;
A nip releasing means for releasing the recording medium held by the fixing means;
A nip release control means for releasing the nipping state of the recording medium by the nip releasing means when the metal adhering to the recording medium is detected by the metal detecting means;
The image forming apparatus according to claim 1, further comprising: The nip release control means determines whether or not the developer image is transferred to the recording medium when the metal adhering to the recording medium is detected by the metal detection means. Is not transferred to the recording medium, the nip releasing means releases the nipping state of the recording medium, and if the developer image is transferred to the recording medium, the nip releasing means Does not release the sandwiched state of the recording medium,
The image forming apparatus according to claim 4 . The conveyance auxiliary roller control means includes:
The conveyance auxiliary roller is controlled so that the conveyance auxiliary roller pinches the recording medium when the distance between the image carrier and the transfer unit is increased by the control unit. The image forming apparatus according to claim 1 . The conveying means is
A pair of front transport rollers provided on the upstream side of the image forming position in the transport path for transporting the recording medium;
The distance along the conveyance path between the front conveyance roller and the conveyance auxiliary roller is smaller than the length in the conveyance direction of the recording medium having a minimum size capable of forming an image . The image forming apparatus according to claim 6 . The conveying means is
A pair of rear conveyance rollers provided on the downstream side of the fixing unit in the conveyance path for conveying the recording medium;
Distance along the conveying path of the conveying auxiliary roller and said rear conveyance roller, imageable minimum size of the features is smaller than the length of the conveying direction of the recording medium according to claim 1 wherein Item 8. The image forming apparatus according to Item 7 . An image forming operation prohibiting unit for prohibiting an image forming operation of the image forming unit when the metal detecting unit detects a metal adhering to the recording medium;
The image forming apparatus according to any one of claims 1 to 8, characterized in that it comprises a. When the metal adhering to the recording medium is detected by the metal detecting means, an image re-formation instructing means for instructing the image forming means to form the same image on a new recording medium again.
The image forming apparatus according to any one of claims 1 to 9, characterized in that it comprises a.

Images