JP2006106327A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain not only satisfactory transportability of a recording sheet in the vicinity of a separating/destaticizing means after transfer but also a good toner image by a relatively simple and inexpensive configuration. <P>SOLUTION: First transporting ribs and second transporting ribs are disposed. The first transporting ribs are formed so that front ends of a sawtooth-like electrode plate destaticizing part don't project to a recording sheet transporting surface, and are formed by partially cutting out the front ends of the sawtooth-like electrode plate destaticizing part and are formed so as to overlap a transporting guide between transfer and fixing. The second transporting ribs are formed so that the front ends of the sawtooth-like electrode plate destaticizing part don't project to the recording sheet transporting surface, and are formed without cutting out the front ends of the sawtooth-like electrode plate destaticizing part. Spaces are provided in the vicinities of the front ends of the sawtooth-like electrode plate destaticizing part, where the first and the second transporting ribs don't exist. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a printer, a facsimile, and a copying machine using an electrophotographic process.

  In image forming apparatuses such as printers, facsimiles, and copiers using an electrophotographic process, a toner image is formed on an image carrier such as a photosensitive drum, the toner image is transferred to a recording sheet, and the toner image is transferred. The recorded recording sheet fixes the toner image by the fixing device, and then the recording sheet is discharged out of the main body by the discharge device.

  In the image forming apparatus, the separation / static discharge device for transferring the toner image from the image carrier to the recording sheet and separating the image carrier from the recording sheet includes a sawtooth electrode plate made of a conductive thin plate. ing.

  The sawtooth electrode plate provided in the separation / static discharge device is disposed in the vicinity where the image carrier and the recording sheet are separated, and the recording sheet after the toner image transfer is recorded when separated from the image carrier and after the separation. The excess charge on the sheet is removed.

  In recent years, with the speeding up of image forming apparatuses, it has been desired to increase the charge removal efficiency of the separation / charge removal apparatus.

  If the recording sheet is not sufficiently neutralized, the recording sheet is wound around the image carrier by electrostatic adsorption, and JAM occurs, or the toner image on the recording sheet is disturbed due to excess charge, resulting in a defective image. . For this reason, the sawtooth electrode plate needs to provide a space in the vicinity of the charge removal portion of the sawtooth electrode plate or make the sawtooth electrode plate closer to the recording sheet in order to make the recording sheet uniform and increase the neutralization efficiency. Thus, the sawtooth electrode plate 22 is arranged in the vicinity of the normal line N direction of the photosensitive drum on the line connecting the center of the image carrier and the transfer roller center, preferably at a position of ± 1 mm with respect to this normal line.

  When a serrated electrode plate is placed near the normal line, the conveyed recording sheet and the serrated electrode plate are caught, and the toner image on the recording sheet is disturbed, the recording sheet is damaged, or a jam occurs. There is.

  In particular, the front end of the recording sheet and the flap portion of the envelope are easily caught.

  In order to solve such problems, the following techniques have been conventionally devised.

  According to the technique described in Japanese Patent Application Laid-Open No. 10-142950, there is provided a moving member that moves the charge removal member from the charge removal position to the retracted position as the recording sheet moves.

  According to the technique described in Japanese Patent Application Laid-Open No. 11-15288, when the recording sheet passes through the transfer rotation member, the charge removal member moves from the charge removal position to the retracted position in conjunction with the transfer rotation member. is there.

  According to the technique disclosed in Japanese Patent Application Laid-Open No. 2003-15429, the static eliminator is variable in the vertical direction.

Further, as shown in FIGS. 8 and 9, there are some which are provided with a conveying rib so that a part of the serrated electrode plate is notched and the recording sheet is not caught on the charge eliminating portion of the serrated electrode plate.
Japanese Patent Laid-Open No. 10-142950 Japanese Patent Laid-Open No. 11-15288 JP 2003-15429 A

  Although the above-described prior art is effective for preventing the recording sheet from being caught on the sawtooth electrode plate, it is desired to be improved / improved in the following points.

  The technique described in Japanese Patent Application Laid-Open No. 10-142950 requires a mechanism for moving the charge removal member from the transfer position to the retracted position in conjunction with the recording sheet, which complicates the apparatus and becomes expensive. Further, since the charge removal member operates in conjunction with the recording sheet to be passed, the operation control of the charge removal member becomes more difficult as the speed of the image forming apparatus increases.

  In addition, it is desirable to take measures against entry and catching into the conveyance guide downstream of the transfer member when the charge removal member is retracted.

  The technique described in Japanese Patent Application Laid-Open No. 11-15288 requires a mechanism for moving the charge removal member from the charge removal position to the retracted position in conjunction with the transfer rotation member, which complicates the apparatus and makes it expensive.

  In addition, it is desirable to take measures against entry and catching into the conveyance guide downstream of the transfer member when the charge removal member is retracted.

  The technique described in Japanese Patent Application Laid-Open No. 2003-15429 requires a mechanism and control capable of changing the static eliminating member in the vertical direction, and the apparatus becomes complicated and expensive.

  In addition, it is desirable to take measures against entry and catching into the conveyance guide downstream of the transfer member when the charge removal member is retracted.

  When the sawtooth electrode plate is partly cut out as shown in FIG. 8 and FIG. 9 and the recording sheet is provided with a conveying rib so that the recording sheet is not caught on the charge removal portion of the sawtooth electrode plate, the recording sheet and the sawtooth electrode plate Therefore, it is necessary to set the difference h between the height of the conveying rib and the height of the serrated electrode plate shown in the enlarged view of FIG. 4 to an appropriate size. If the height of the conveying rib is increased in the direction approaching the image carrier side and an attempt is made to secure the difference h from the sawtooth electrode plate, the recording sheet and the conveying rib rub against each other strongly. appear. Also, if the sawtooth electrode plate is moved away from the image carrier and the difference h from the conveying rib height is to be secured, the recording sheet will not be sufficiently neutralized and recorded on the image carrier by electrostatic adsorption. The sheet is wound, JAM is generated, and the toner image on the recording sheet is disturbed due to excessive charge.

  Further, in order to reduce the difference h between the height of the conveying rib and the sawtooth electrode plate, when the number of conveying ribs is increased to prevent the recording sheet from being caught as shown in FIGS. The number of notches in the electrode plate increases, the charge removal portion of the sawtooth electrode plate decreases, the charge removal capability decreases, the recording sheet winds around the image carrier due to electrostatic adsorption, JAM occurs, The toner image on the recording sheet is disturbed by the extra charge.

  In order to improve / improve the above-mentioned problems, the present invention is formed so that the tip of the sawtooth electrode plate neutralization portion does not protrude to the recording sheet conveyance surface, and a part of the tip of the sawtooth electrode plate neutralization portion is cut away. The first conveyance rib formed so as to overlap the conveyance guide between the transfer and fixing, and the tip of the sawtooth electrode plate neutralization section are formed so as not to protrude to the recording sheet conveyance surface, and the sawtooth electrode plate neutralization A second conveying rib formed so as not to cut out the tip of the portion, and a space is provided in the vicinity of the tip of the serrated electrode plate neutralizing portion without the first and second conveying ribs. An object of the present invention is to provide an image forming apparatus capable of obtaining a stable recording sheet transportability and a good toner image with a simple and inexpensive configuration.

  According to the first aspect of the present invention, an image carrier that forms a toner image, a transfer unit that transfers the toner image formed on the image carrier onto the recording sheet, and a downstream side of the transfer unit are disposed, and discharge of the recording sheet is performed. Separation / static elimination means to be performed, an insulating wall made of an electrical insulating material arranged between the transfer means and the separation / static elimination means, and a separation means arranged on the downstream side of the separation means to transfer the recording sheet to the fixing means- A saw blade that is a separation / static discharge means in the vicinity of the normal direction of the image carrier on the line connecting the center of the image carrier and the transfer means center, and includes a conveyance guide between fixing members and a fixing unit that fixes the toner image on the recording sheet. A serrated electrode plate is formed so that the tip of the serrated electrode plate neutralizing portion does not protrude to the recording sheet conveying surface, and a part of the tip of the serrated electrode plate neutralizing portion is notched, between transfer and fixing. It is formed so as to overlap with the transport guide, and The first conveying rib made of a typical insulating material and the tip of the sawtooth electrode plate neutralizing portion are formed so as not to protrude to the recording sheet conveying surface, and the tip of the sawtooth electrode plate neutralizing portion is not cut out. And a second transport rib made of an electrically insulating material is disposed, and a space is provided in the vicinity of the tip of the sawtooth electrode plate neutralizing section without the first and second transport ribs. To do.

  The invention according to claim 2 is characterized in that the tip position of the sawtooth electrode plate neutralizing section is at a position of ± 1 mm with respect to the image carrier normal line on the line connecting the center of the image carrier and the center of the transfer means. To do.

  The invention according to claim 3 is characterized in that the tip position of the serrated electrode plate neutralizing section is arranged 0.5 to 1 mm lower than the transport surfaces of the first and second transport ribs.

  The invention according to claim 4 is characterized in that the insulating wall, the first conveying rib, and the second conveying rib are integrally formed.

  As described above, according to the present invention, the tip of the sawtooth electrode plate neutralization portion is formed so as not to protrude to the recording sheet conveying surface, and a part of the tip of the sawtooth electrode plate neutralization portion is cut away. The first conveying rib formed so as to overlap the conveyance guide between the transfer and fixing, and the tip of the sawtooth electrode plate neutralizing portion are formed so as not to protrude to the recording sheet conveying surface, and the sawtooth electrode plate neutralizing portion It is relatively easy to arrange a second conveying rib formed so as not to cut off the tip, and to provide a space near the tip of the sawtooth electrode plate neutralizing unit without the first and second conveying ribs. In addition, it is possible to provide an image forming apparatus that can obtain a good recording sheet conveyance property and a good toner image with a low-cost configuration.

Example 1
A first embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings.

  FIG. 3 is a schematic sectional view showing the image forming apparatus according to the present embodiment.

  As shown in FIG. 3, a laser beam printer 1 will be described as an image forming apparatus in this embodiment. The laser beam printer 1 includes a feeding cassette 2 on which recording sheets P are stacked, a process cartridge attachment / detachment cover 3 for attaching / detaching and jamming a process cartridge, a feeding roller 4 for feeding the recording sheets P, and a recording sheet. Separation pad 5 for separating P one by one, intermediate conveyance roller 6 which is an intermediate conveyance means for conveying the fed recording sheet P into the laser beam printer main body, intermediate conveyance roller 6a facing this, conveyance means A registration roller 7, a registration roller 7 a facing the registration roller 7, a registration shutter 8 serving as a skew correction unit of the recording sheet, a registration roller 7, a registration roller 7 a, and a registration shutter 8. Registries that protect the unit , A photo interrupter 20 as detection means for detecting the leading and trailing edges of the recording sheet P sent from the registration roller unit, the registration sensor lever 21, and the registration roller unit. A pre-transfer upper guide 10 and a pre-transfer lower guide 19 for guiding the recording sheet P to the transfer section, a process cartridge 11 including a photosensitive drum 11a, a transfer roller 12 as a transfer means for transferring an image to the recording sheet P, and a transfer A sawtooth electrode plate 22 for separating and discharging the subsequent recording sheet, a transfer-fixing conveyance guide 25 for guiding the separated and discharging recording sheet to the fixing unit, a laser scanner unit 13 and a fixing unit including a fixing heater. Heater unit 14, fixing pressure roller 15, and recording sheet after fixing A discharge conveying rollers 16 and the discharge conveying roller 16a to transport the, and a discharge roller 17 and the discharge roller 17a to discharge the recording sheet P to the outside of the laser beam printer 1 main body, and a sheet discharge stacking unit 18.

  A plurality of recording sheets P are stacked on the feeding cassette 2. When a print command is received, one recording sheet P in the feeding cassette 2 is fed by the feeding roller 4 and the separation pad 5. Separately feed.

  The fed recording sheet P is sent to the intermediate conveyance roller 6 and the intermediate conveyance roller 6a. Further, the recording sheet P transported by the intermediate transport roller 6 passes through the sheet transport path and abuts against the sheet contact portion 8a of the registration shutter 8 in the registration unit.

  The recording sheet P rotates in a direction in which the registration shutter 8 is retracted while being in contact with the sheet contact portion 8a, and is conveyed to the nip between the registration roller 7 and the registration roller 7a to perform skew correction.

  The recording sheet P after skew correction is abutted against the registration sensor lever 21. The recording sheet P is rotated in a direction in which the registration sensor lever 21 is retracted while contacting the registration sensor lever 21.

  The recording sheet P having the registration sensor lever 21 rotated is transported through a sheet transport path formed by the pre-transfer upper guide 10 and the pre-transfer lower guide 19 and enters the nip of the photosensitive drum 11 a facing the transfer roller 12. Be transported.

  Laser light L is irradiated onto the photosensitive drum 11a from the laser scanner unit 13 together with the print command, and a toner image is formed on the photosensitive drum 11a. The toner image formed on the photosensitive drum 11 a is transferred to the recording sheet P at the nip between the photosensitive drum 11 a and the transfer roller 12.

  The transferred recording sheet P is separated and discharged by the sawtooth electrode plate 22.

  As shown in FIG. 7, the serrated electrode plate 22 is arranged in the vicinity of the normal line N direction of the photosensitive drum on the line connecting the photosensitive drum center and the transfer roller center, and along the sawtooth electrode plate mounting surface 26 made of an insulating material. Has been placed.

  Next, the recording sheet P to which the toner image has been transferred is sent to a fixing unit composed of a fixing pressure roller 15 and a fixing heater unit 14, and is heated and pressed. As a result, the toner image is fixed on the recording sheet P. The recording sheet P on which the toner image is fixed is conveyed along a discharge guide by a discharge conveyance roller 16 and a discharge conveyance roller 16a, and discharged and stacked on the sheet discharge stacking unit 18 by the discharge roller 17 and the discharge roller 17a.

  Next, the separation / static discharge device of the present invention will be described with reference to FIGS. 1, 2, 4, 5, and 6.

  FIG. 1 is a perspective view of the separation / static discharge device, and FIG. 2 is a rear view of the separation / static discharge device as viewed from the downstream side in the sheet passing direction, and includes a sawtooth electrode plate 22, a first conveying rib 23 with a transfer portion, and a transfer portion. The second conveyance rib 24 without a gap is shown. The first conveyance rib 23 with a transfer portion is partially cut away from the neutralization portion of the sawtooth electrode plate 22, and the second conveyance rib 23 without a transfer portion is serrated. The static eliminating portion of the electrode plate 22 is not cut out.

  FIG. 4 is a schematic cross-sectional view of the first transport rib 23 portion having a delivery portion.

  The first conveying rib 23 is provided with an angle in the direction in which the recording sheet is lifted so that the leading end of the discharging sheet is lowered by a distance h from the first conveying rib surface so that the leading end of the recording sheet P that has been conveyed and the discharging unit are not caught. And the front end of the recording sheet S is not caught on the transfer-fixing conveyance guide 25. The distance h from the first transport rib surface is set to 0.5 to 1 mm.

  Particularly, when the leading edge of the recording sheet is curled toward the transfer roller, the transfer-fixing conveyance guide 25 and the first conveyance rib overlap each other because the transfer-fixing conveyance guide 25 may be caught on the upstream side of the conveyance guide between the transfer and fixing. .

  FIG. 5 is a schematic cross-sectional view of the second transport rib 24 portion without a delivery portion.

  As in the case of the first transport rib, an angle is provided in the direction in which the recording sheet is lifted, and the charge eliminating portion is lowered by a distance i from the second transport rib surface so that the leading end of the transported recording sheet P and the charge eliminating portion are not caught. The tip is placed. The distance i from the second transport rib surface is set to 0.5 to 1 mm.

  FIG. 6 is a schematic cross-sectional view of a portion where there is no conveyance rib, and a wide space is secured at the tip of the static elimination portion of the sawtooth electrode plate 22 to improve static elimination efficiency.

  As shown in FIG. 4 and FIG. 5, the transferred recording sheet P leading end abuts on the first transport rib surface 23a and the second transport rib surface 24a, and along the first transport rib surface 23a and the second transport rib surface 24a. Be transported. Thereafter, the leading edge of the recording sheet P is transported along the transport surface 23 b on the downstream side of the first transport rib and transported to the transfer-fixing transport guide 25. Since the first conveyance rib 23 having the transfer portion overlaps the transfer-fixing conveyance guide 25, the leading edge of the recording sheet P is not caught on the transfer-fixing conveyance guide 25.

  As described above, in the image forming apparatus of the present invention, the saw-tooth electrode plate, which is a separation / static discharge unit disposed on the downstream side of the transfer roller, is hooked to the static eliminating unit and the recording sheet to the transfer-fixing conveyance guide A photosensitive drum center and a transfer roller center are provided by including a first conveying rib that is a transfer portion that prevents the tip from being caught, and a second conveying rib that prevents the electrode needle from being caught without cutting the sawtooth electrode plate. A serrated electrode plate can be placed in the vicinity of the normal direction of the photosensitive drum on the line connecting the two, and the excess charge on the recording sheet after separation and after separation is removed, and the recording sheet is transported and a good toner image. Can be obtained.

It is a perspective view of the isolation | separation and static elimination means part which shows embodiment of this invention. It is a rear view of the isolation | separation and static elimination means part which shows embodiment of this invention. It is a schematic sectional drawing which shows embodiment of this invention. It is a schematic sectional drawing of the 1st conveyance rib part which shows embodiment of this invention. It is a schematic sectional drawing of the 2nd conveyance rib part which shows embodiment of this invention. It is a schematic sectional drawing which shows the space near the front-end | tip of static elimination part which shows embodiment of this invention. It is a schematic sectional drawing which shows the normal line on a drum-transfer roller center line, and a sawtooth-shaped electrode plate position. It is a perspective view of the isolation | separation and static elimination means part which shows a prior art example. It is a rear view of the isolation | separation and static elimination means part which shows a prior art example. It is a perspective view of the isolation | separation and static elimination means part which shows a prior art example. It is a rear view of the isolation | separation and static elimination means part which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser beam printer 2 Feed cassette 3 Process cartridge attachment / detachment cover 4 Feed roller 5 Separation pad 6 Intermediate conveyance roller 6a Intermediate conveyance roller 7 Registration roller 7a Registration roller 8 Registration shutter 8a Sheet contact part 8b Resin part 8c Sheet metal 8d Bending portion 9 Registration cover 10 Pre-transfer upper guide 11 Process cartridge 11a Photosensitive drum 12 Transfer roller 13 Laser scanner unit 14 Fixing heater unit 15 Fixing pressure roller 16 Discharge transport roller 16a Discharge transport roller 17 Discharge roller 17a Discharge roller 18 Sheet Discharge stacking unit 19 Pre-transfer upper guide 20 Photo interrupter 21 Registration sensor lever 22 Sawtooth electrode plate 23 First transport rib 23a First transport rib Conveying surface 23b Conveying surface of first conveying rib 24 Second conveying rib 24a Conveying surface of second conveying rib 25 Transfer-fixing conveying guide 26 Saw-tooth electrode plate mounting surface G Grease L Laser light N Center of photosensitive drum and transfer roller Normal line of photosensitive drum on connecting line P Recording sheet

Claims (4)

An image carrier for forming a toner image;
Transfer means for transferring the toner image formed on the image carrier onto the recording sheet;
Separation / static discharge means arranged on the downstream side of the transfer means for discharging the recording sheet;
An insulating wall made of an electrical insulating material disposed between the transfer means and the separation / static elimination means;
A transfer-fixing conveyance guide that guides the recording sheet to the fixing unit, arranged downstream of the separating unit;
Fixing means for fixing the toner image on the recording sheet,
A sawtooth electrode plate as a separation / static discharge means is arranged in the vicinity of the normal direction of the image carrier on the line connecting the center of the image carrier and the center of the transfer means,
The tip of the sawtooth electrode plate neutralization unit is formed so as not to protrude to the recording sheet conveyance surface, and a part of the tip of the sawtooth electrode plate neutralization unit is cut away so as to overlap the conveyance guide between transfer and fixing. A first transport rib formed of an electrically insulating material;
The tip of the sawtooth electrode plate neutralization section is formed so as not to protrude to the recording sheet conveying surface, and the tip of the sawtooth electrode plate neutralization section is formed not to be cut out, and is made of an electrically insulating material. A second transport rib,
An image forming apparatus characterized in that a space is provided in the vicinity of the tip of the sawtooth-shaped electrode plate neutralizing section without the first and second transport ribs. The tip position of the sawtooth electrode plate neutralization unit is
2. The image forming apparatus according to claim 1, wherein the image forming apparatus is located at a position of ± 1 mm with respect to an image carrier normal line on a line connecting the center of the image carrier and the center of the transfer means.   The image forming apparatus according to claim 1, wherein a tip position of the sawtooth electrode plate neutralizing unit is disposed 0.5 to 1 mm lower than a conveying surface of the first and second conveying ribs.   The image forming apparatus according to claim 1, wherein the insulating wall, the first transport rib, and the second transport rib are integrally formed.

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