JP3509325B2 - Paper jam removal structure in image forming apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a laser printer, when a toner image formed on an image bearing member such as a photosensitive drum is transferred to the recording sheet, The present invention relates to a structure for removing a paper jam caused by sticking to an image carrier.

[0002]

2. Description of the Related Art As one of paper jams that occurs during the operation of an image forming apparatus such as a copying machine, when a toner image formed on an image carrier is transferred to the recording sheet, the recording sheet is used. The so-called pop jam that sticks to (POP
JAM: Paper On the Photorec
eptor JAM).

Conventionally, as a structure for removing this pop jam, in a small black-and-white copying machine or a laser printer, etc., which has a relatively simple structure, the device frame is made to have a large crocodile-shaped opening, and the image is carried from the opening. It is general that the recording sheet stuck to the body can be removed.

On the other hand, in a color copying machine, since it is necessary to repeatedly transfer a large number of color toner images from an image carrier to a recording sheet, a position facing the image carrier with the toner image transfer position interposed therebetween. Is provided with a transfer drum that rotates in synchronization with the image carrier, and the recording sheet is repeatedly fed to the transfer position of the toner image while being electrostatically attracted to the transfer drum. Therefore, in a color copying machine equipped with such a transfer drum, since the trailing edge of the recording sheet relating to pop jam is stuck to the transfer drum,
A structure is adopted in which the transfer drum is pulled out in the axial direction from the position facing the image carrier, and the recording sheet relating to the pop jam is taken out of the apparatus together with the transfer drum.

[0005]

However, although the structure for removing the pop jam by opening the device frame like an alligator like the former is relatively easy to apply to a small copying machine or a laser printer, etc. However, there is a problem in that it is difficult to apply it to a large-scale copying machine or the like, which has many peripheral devices of the image carrier and is heavy.

Further, in the latter case where the transfer drum is pulled out in the axial direction to remove the pop jam, when the rear end of the recording sheet relating to the pop jam is not stuck to the transfer drum, the recording sheet concerned. Only the transfer drum is pulled out while leaving the inside of the device. Therefore, when the structure in which the recording sheet is attracted to the transfer drum at the same time as the transfer of the toner image to the recording sheet is adopted, the rear end of the recording sheet related to the pop jam is not stuck to the transfer drum yet. The pop jam could not be removed by simply pulling out the transfer drum in the axial direction. In addition, when the recording sheet related to the pop jam is left in the apparatus in this way,
The user of such a copying machine cannot remove the recording sheet unless he / she pushes his / her hand deep inside the apparatus.
The removal work becomes very dangerous, and in some cases, the recording sheet cannot be removed.

The present invention has been made in view of such a problem, and an object of the present invention is to take out a recording sheet relating to a pop jam from the apparatus with a simple structure, and further take out the taking-out work. It is an object of the present invention to provide a paper jam clearance structure capable of easily performing the above.

[0008]

That is, according to the present invention, when a toner image formed on an image bearing member is transferred to a recording sheet, a paper jam caused by the recording sheet winding around the image bearing member is eliminated. And a structure for performing the above operation, and is arranged so as to be drawn out in the axial direction of the image carrier on the upstream side of the transfer position of the toner image in the conveying direction of the recording sheet, and is wound around the image carrier at the time of such drawing. An engaging member that presses the rear end of the recording sheet in the pull-out direction is provided, and the engaging member is provided at a position downstream of the transfer position in the recording sheet conveying direction and close to the image carrier. A sheet-like sheet restraining member that is pulled out together with the sheet holding member extending toward the image carrier on the far side in the pull-out direction is provided at the position facing the sheet restraining member. With drawn together members,
A sheet guide member for guiding the recording sheet on which the toner image has been transferred is provided.

According to such a technical means, when the engaging member is pulled out in the axial direction of the image carrier when the pop jam occurs, the engaging member is located on the recording sheet rather than the transfer position of the toner image. Since it is provided on the upstream side in the transport direction,
The engaging member presses the rear end portion of the recording sheet attached to the image carrier in the pull-out direction. On the other hand, since the front end of the recording sheet is still attached to the image carrier, a rotational force with the engaging member as a fulcrum is generated in the recording sheet whose rear end is pressed in the pull-out direction, and the front end of the recording sheet is Curvature is generated from the front side edge in the pull-out direction and is gradually separated from the image carrier.

At this time, a plate-like sheet restraining member that is pulled out together with the engaging member is disposed at a position downstream of the transfer position in the conveying direction of the recording sheet and close to the image carrier. In addition, since the sheet pressing member projects from the front side in the pull-out direction toward the image carrier, the recording sheet that is curved from the front side edge of the sheet pressing member is bent from the curved portion. Crawl down. Therefore, when the engaging member is pulled out to the front side, the leading end of the recording sheet is separated from the image carrier and enters the lower side of the sheet holding member in a bent state to face the sheet holding member. It is sandwiched between the sheet guide member and the sheet guide member.

As a result, when the engagement member, the sheet pressing member, and the sheet guiding member are pulled out toward the front side in the axial direction of the image carrier, the recording sheet in which the pop jam has occurred has its rear end acting as the engaging member. The sheet is taken out of the image forming apparatus in a state where it is caught and is sandwiched between the sheet restraining member and the sheet guiding member.

Here, the sheet guide member may be a mere plate-like member, but when a transfer drum is arranged facing the image carrier as in a color copying machine, such transfer is performed. The drum can be used as a sheet guide member. Therefore, when the present invention is applied to a color copying machine, the transfer drum may be pulled out in the axial direction of the image carrier together with the engaging member and the sheet pressing member.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The paper jam removing structure of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows an example of a color laser printer to which the present invention is applied. In the figure, reference numeral 20 is a photoconductor drum (image carrier), 21 is a charging corotron for precharging the surface of the photoconductor drum 20, and 22 is an electrostatic latent image on the photoconductor drum 20 charged by the charging corotron 21. A laser beam scanner 23 for writing the image, and four developing devices 23K, 23C, 23M, and 23Y in which toner images of black (K), cyan (C), magenta (M), and yellow (Y) are stored are freely rotatable. , 24 is a rotary developing unit that is appropriately switched and selected, 24 is a transfer pretreatment corotron for performing charge processing of toner on the photoconductor drum 20, and 24a is attached to the photoconductor drum 20 when a pop jam occurs. Recording sheet 3
Jam detection sensor for detecting 0, 25 for the photosensitive drum 2
Reference numeral 26 denotes a cleaner for removing the residual toner on 0, and 26 is a waste toner recovery tank provided integrally with the cleaner.

On the other hand, reference numeral 31 indicates that the recording sheet 30 is wound and held on the peripheral surface, and the photosensitive drum 2 is attached to the recording sheet 30.
This is a transfer drum that sequentially multiple-transfers toner images of respective color components on 0. The transfer drum 31 comprises a drum frame and a drum sheet made of, for example, polyvinylidene fluoride, stretched over the drum frame, and the recording sheet 30 is electrostatically adsorbed by charging the drum sheet.

Further, on the transfer drum 31, a transfer corotron 42 for transferring the toner image on the photoconductor drum 20 to the recording sheet 30 side, and a destaticizing corotron 43 for destaticizing the recording sheet 30 after the transfer process of the final color are completed. A cleaning static eliminator corotron 44 for removing charges on the drum sheet 35 after the final color transfer process, a cleaning brush 45 for cleaning paper dust and the like adhering to the drum sheet after the final color transfer process, An inner pressing roll 46 that pushes up the drum sheet from the inside when the sheet 30 is peeled off, and a peeling claw 47 that peels the recording sheet 30 from the transfer drum 31 are provided.

Further, reference numeral 48 is a sheet supply system for guiding the recording sheet 30 supplied from a sheet feeding cassette (not shown) to the transfer drum 31, and this sheet supply system 48
The recording sheet 30 is directly fed to the position where the photosensitive drum 20 and the transfer drum 31 face each other. That is, the transfer corotron 42 is the recording sheet 3
It also plays a role of adhering 0 to the transfer drum 31, and when the toner image on the photosensitive drum 20 is transferred to the recording sheet 30 side, the recording sheet is adsorbed to the transfer drum 31 at the same time.

Further, reference numeral 50 is a fixing device for inserting the recording sheet 30 after the transfer process and fixing the unfixed toner image on the recording sheet 30, and a heating roll 51 having a heater built therein and the heating roller 51. The pressure roller 52 is arranged in pressure contact with the roller 51.

In the color printer of the present embodiment configured as described above, the laser beam scanner 22 exposes the photosensitive drum 20 on the basis of image information provided from a host computer (not shown) or the like, and the photosensitive drum 20 is exposed. An electrostatic latent image corresponding to black K is written on the top. On the other hand, in the rotary developing unit 23, the black developing device 2
3K is set at a position facing the photoconductor drum 20, and the electrostatic latent image is developed by the black developing device 23K with a slight delay from the writing timing. The black K toner image thus formed is transferred to the recording sheet 30 sent from the sheet supply system 48 at a predetermined timing, and the recording sheet 30 is attracted to the transfer drum 31 in accordance with this transfer. . After that, the transfer drum rotates while holding the recording sheet. Further, when the developing process by the black developing device 23K is completed, the developing device is replaced until the transfer drum 31 completes one rotation cycle, and the yellow developing device 23Y is exposed by the 90 ° rotation of the rotary developing unit 23. It is set at a position facing the body drum 20.

After that, these operations are repeated every one rotation cycle of the transfer drum 31, and the toner images of yellow Y, magenta M, and cyan C are held on the transfer drum 31 from the photoconductor drum 20 each time. The image is transferred to the recording sheet 30, and a superposed toner image is formed on the recording sheet 30 by four color toner images. Then, the recording sheet 30 on which the cyan C toner image has been transferred is peeled off from the transfer drum 31 as it is, and is discharged to a discharge tray (not shown) via the fixing device 50.

Next, the structure for removing pop jams in this color printer will be described. When a so-called pop jam occurs in which the front end of the recording sheet 30 to which the toner image is transferred sticks to the photoconductor drum 20, in this color printer, the transfer drum 31 is pulled out from the position facing the photoconductor drum 20 in the axial direction and popped. The recording sheet 30 related to the jam is taken out of the apparatus together with the transfer drum 31.

FIG. 2 shows a transfer drum unit 3 in which a transfer drum 31 is rotatably held. In the unit 3, in addition to the transfer drum 31, the fixing device 50, a peeling claw 47 (not shown), Sheet supply system 48 (not shown)
Etc. are integrally incorporated. In the figure, the transfer drum unit 3 is housed in the frame of the printer,
That is, the state is shown in which the photoconductor drum 20 and the transfer drum 31 face each other, and from this state, the transfer drum unit 3 can be pulled out from the frame of the printer along the direction of the arrow in the figure. There is. The transfer drum 31 is swingably supported with respect to the front frame 32 and the rear frame 33, and when the transfer drum unit 3 is pulled out of the frame, the transfer drum 3 is previously supported.
1 and the photoconductor drum 20 can be separated from each other.

On the upper portion of the transfer drum unit 3, a plate-like sheet restraining member 34 is attached so as to straddle the front frame 32 and the rear frame 33. The sheet restraining member 34 is arranged substantially parallel to the peripheral surface of the transfer drum, and as shown in FIG. 1, the disposing position of the sheet suppressing member 34 is higher than that of the facing position of the transfer drum 31 and the photoconductor drum 20. 30 on the downstream side in the transport direction, that is, on the downstream side of the transfer position of the toner image on the recording sheet 30,
It is a position close to the photoconductor drum 20. Further, the sheet pressing member 34 is formed in a triangular shape in which the rear side (the rear frame 33 side) of the transfer drum 31 in the pulling-out direction is protruded toward the photosensitive drum 20 from the front side (the front frame 32 side). And the sheet restraining member 3
4 and the photoconductor drum 20 are separated by the front frame 32.
Is gradually narrowed as it approaches the rear frame 33.

Further, a hook (engaging member) 35 is erected on the rear frame 33 of the transfer drum unit 3. The hook 35 is arranged upstream of the position where the transfer drum 31 and the photoconductor drum 20 face each other in the conveying direction of the recording sheet 30, that is, in the broken line circle A shown in FIG. The hook 35 crosses the recording sheet conveying path indicated by the alternate long and short dash line when the sheet 3 is pulled out. Therefore, when the transfer drum unit 3 is pulled out when a pop jam has occurred, the hook 35 engages with the rear end portion of the recording sheet 30 having the pop jam from the side thereof.

3 and 4 show a state in which the recording sheet conveyed from the sheet supply system 48 causes a pop jam, and FIG. 3 shows the photosensitive drum 20 and the transfer drum 31 observed from above. FIG. 4 is a plan view showing the photosensitive drum 2.
3 is a cross-sectional view showing the recording sheet 30 stuck to 0. FIG. When such a pop jam occurs, the jam detection sensor 24a provided on the downstream side of the transfer position of the toner image detects the recording sheet 30 attached to the photoconductor drum 20, so that the photoconductor drum 20 and the transfer drum 31 are separated from each other. The rotation is immediately stopped, and the recording sheet 30 is stopped at a position where the leading edge of the recording sheet 30 slightly passes a position facing the sheet pressing member 34 (see FIG. 4). On the other hand, the rear end of the recording sheet 30 is not yet attracted to the transfer drum 31, and when the recording sheet 30 is observed from the front frame 32 side of the transfer drum unit 3, it is erected on the rear frame 33 as shown in FIG. The hook 35 and the rear end of the recording sheet 30 overlap each other. Although FIG. 4 shows a state where the transfer drum 31 and the photoconductor drum 20 are in contact with each other, as shown in FIGS. 6 and 7, the hook 35 is provided when the transfer drum 31 and the photoconductor drum 20 are separated from each other. It suffices that the rear edge of the recording sheet 30 and the rear edge of the recording sheet 30 overlap.

On the other hand, FIG. 5 shows a state in which the transfer drum unit 3 is partially pulled out in order to remove the recording sheet 30 in which the pop jam has occurred. Since the recording sheet 30 in which the pop jam has occurred is not adsorbed on the transfer drum 31 at all, when the transfer drum unit 3 is pulled out, the recording sheet 30 remains attached to the photosensitive drum 20 and the front frame 3 of the transfer drum unit 3.
It moves from the 2 side to the rear frame 33 side. When the amount of pulling out the transfer drum unit 3 further increases, the recording sheet 30 tries to get over the rear frame 33 and stay in the printer. However, as shown in FIG. 5, at this time, the hooks erected on the rear frame 33 are provided. 35 is the recording sheet 30
It engages with the rear end from the side.

As a result, a pressing force acts on the rear end of the recording sheet 30 from the hook 35, and a rotational force in the direction of arrow B in FIG. 5 is generated on the recording sheet 30. As a result, the leading end of the recording sheet 30 attached to the photoconductor drum 20 is curved from the front side of the transfer drum 31 in the pull-out direction, and as shown in FIG. 6, from the front side of the photoconductor drum 20. It is gradually peeled off. On the other hand, as shown in FIG. 7, at this stage, the leading end of the recording sheet 30 is not completely peeled off from the photoconductor drum 20, and the inner edge of the recording sheet 30 is still stuck to the photoconductor drum 20. Up to.

When the transfer drum unit 3 is further pulled out from the state shown in FIG. 5, the leading end of the recording sheet is completely peeled off from the photosensitive drum 20 as shown in FIG. In addition, the photosensitive drum 20 of the sheet pressing member 34
Since the amount of protrusion to the front frame 32 side gradually increases from the rear frame 33 side,
The recording sheet 31 that is curved from the front side edge goes under the sheet restraining member 34 from the curved portion as the amount of bending increases. Therefore, immediately before the transfer drum unit 3 is completely pulled out from the frame of the printer, the leading end of the recording sheet 30 is completely peeled off from the photosensitive drum 20, and as shown in FIG.
4 and the transfer drum 31 are sandwiched.

As a result, the rear end of the recording sheet 30 separated from the photosensitive drum 20 is engaged with the hook 35, while the front end thereof is transferred to the transfer drum 31 and the sheet pressing member 3.
Since the recording sheet 30 is sandwiched between the transfer drum unit 3 and the transfer drum unit 3, the recording sheet 30 is also pulled out together with the transfer drum unit 3 to the outside of the printer frame. The sheet 30 can be removed.

In the above description, the recording sheet 30 sent from the sheet supply system 48 is pop jammed. However, the recording sheet 30 already adsorbed on the transfer drum 31, for example, the first color has already been adsorbed. If a pop jam occurs on the recording sheet 30 on which the second color toner image is being transferred after the transfer of the toner image of No. 2 is completed, the rear end of the recording sheet 30 is electrostatically attracted to the transfer drum 31. Therefore, the recording sheet 30 relating to the pop jam can be easily taken out of the printer frame simply by pulling out the transfer drum unit 3.

On the other hand, even if the recording sheet 30 is already adsorbed on the transfer drum 31, when the adsorbing force on the transfer drum 31 is weak, the recording sheet 30 is peeled off from the transfer drum 31 as the transfer drum unit 3 is pulled out, and the photosensitive drum 20.
There is a concern that it will be left behind inside the printer frame while it is stuck to the printer. However, as the transfer drum unit 3 is pulled out, the hook 35 provided upright on the rear frame 33 is always engaged with such a recording sheet 30. Therefore, even in such a case, the same operation as described above is performed. The recording sheet 30 related to the pop jam can be taken out of the printer frame.

In the present invention, the sheet restraining member 34 is used.
2 is not limited to the triangular shape as shown in FIG. 2, and as long as the amount of protrusion with respect to the photoconductor drum 20 gradually increases from the front frame 32 side toward the rear frame 33 side, FIG. ) And (b). However, the axial length x of the portion that projects most toward the photoconductor drum 20
However, the width is preferably 1/2 or less of the width of the minimum size recording sheet used in this printer.

Further, as shown in FIG. 11, the present invention can be carried out in exactly the same manner by using an endless transfer belt 60 instead of the transfer drum 31. Even in such a case, the sheet restraining member 34 and the hook 35 are attached to the transfer belt 6
By pulling it out in the axial direction of the photosensitive drum 20 together with 0,
The recording sheet 30 having the pop jam is taken out of the printer frame together with the transfer belt 60.

Further, FIG. 12 shows an example in which the present invention is applied to an ordinary black-and-white copying machine. As shown in the figure, while the transfer corotron 61 is provided with the hook 35 on the upstream side in the conveying direction of the recording sheet 30 with respect to the transfer position of the toner image where the transfer corotron 61 faces the photoconductor drum 20, the recording sheet 30 is transferred with respect to the transfer position. The sheet restraining member 34 is provided on the downstream side of the sheet conveying direction. A sheet conveying belt 62 that guides the recording sheet on which the toner image is transferred is provided at a position facing the sheet pressing member 34 with the recording sheet conveying path interposed therebetween.
Was set up. Even in the black-and-white copying machine configured as described above, when the pop jam occurs, the sheet restraining member 34, the hook 35, and the sheet conveying belt 62 are pulled out from the apparatus frame body toward the front side to pop the sheet. The leading edge of the jammed recording sheet 30 is peeled off from the photoconductor drum 20 and sandwiched between the sheet pressing member 34 and the sheet conveying belt 62. Can be taken out of the body.

[0034]

As described above, according to the paper jam removing structure of the present invention, the engaging member provided on the downstream side of the transfer position of the toner image and the upstream side of the transfer position of the toner image. By pulling out the three members of the sheet pressing member and the sheet guiding member, which are axially front side of the image carrier,
Since the recording sheet having the pop jam is taken out of the frame of the image forming apparatus together with these sheet pressing members,
The pop jam can be reliably removed with a simple configuration and operation, and the risk that the user puts his / her hand inside the device frame to perform the jam removal process can be avoided.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a color printer to which a paper jam removing structure of the present invention is applied.

FIG. 2 is a perspective view showing a transfer drum unit according to an embodiment.

FIG. 3 is a plan view of a photosensitive drum and a transfer drum showing a state in which a pop jam has occurred.

4 is a sectional view taken along line IV-IV of FIG.

FIG. 5 is a plan view of the photosensitive drum and the transfer drum, showing a state in which the transfer drum unit is pulled out partway to remove the pop jam.

6 is a sectional view taken along line VI-VI of FIG.

7 is a sectional view taken along the line VII-VII in FIG.

FIG. 8 is a plan view of the photosensitive drum and the transfer drum, showing a state immediately before the transfer drum unit is completely pulled out.

9 is a sectional view taken along line IX-IX in FIG.

FIG. 10 is a plan view showing another example of the sheet restraining member.

FIG. 11 is a schematic view showing an embodiment of a color printer using an endless transfer belt instead of the transfer drum.

FIG. 12 is a schematic view showing an example in which the present invention is applied to a monochrome copying machine.

[Explanation of symbols]

20 ... Photosensitive drum (image bearing member), 30 ... Recording sheet,
31 ... Transfer drum (sheet guide member), 34 ... Sheet restraining member, 35 ... Hook (engaging member)

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Claims (2)

(57) [Claims] 1. A structure for removing a paper jam generated when a toner image formed on an image bearing member is transferred to a recording sheet when the recording sheet is wound around the image bearing member. The recording sheet is arranged so that it can be pulled out in the axial direction of the image carrier on the upstream side of the transfer position of the image in the conveying direction of the recording sheet. While an engaging member for pressing is provided on the downstream side of the transfer position in the conveying direction of the recording sheet and in a position close to the image carrier, the engaging member is pulled out together with the engaging member, and from the front side in the pulling-out direction. Is provided with a plate-shaped sheet restraining member whose inner side projects toward the image carrier, and at a position facing the sheet restraining member, the sheet restraining member is pulled out together with the engaging member and A paper jam removing structure comprising a sheet guide member for guiding a recording sheet onto which a toner image has been transferred. 2. The paper jam removing structure according to claim 1, wherein the sheet guide member is a transfer conveyance body that electrostatically attracts and rotates a recording sheet at a toner image transfer position.