JPH0455864A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent a stuck part by coloring powder from being formed in a non-image part and to prevent the winding of a paper in a fixing device by making a part which is at least closer to a leading edge side in a paper moving direction than a formed image the non-image part in the case of superposing and forming the image on the same side of the paper. CONSTITUTION:This device is provided with a paper supply means 55 which repetitively supplies the paper P to which the image is transferred without inverting from a surface to a back surface to an image carrier 27 after the latent image formed on the image carrier 27 is developed, and a control means 131 for actuating a non-image part forming means 121 so that a specified area at the time of transferring the developed image M to the surface of the paper may be the non-image part L when the means 55 acts. When the means 55 acts, the non-image part forming means 121 is actuated according to the command of the means 131 so that at least the part on the leading edge side in the paper moving direction A may be the non-image part L. Thus, the stuck part by the coloring powder does not exist at the leading edge part and the winding of the paper in the fixing device is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an image forming apparatus applied to, for example, a type copying machine.

(Prior Art) This type of electrostatic copying machine has an image scanning unit that illuminates an image on a document and guides the reflected light to a photoreceptor, and an electrostatic latent image is formed by light from this image scanning unit. an image forming section including the photoreceptor for reproducing an image of a document; and a feeding/discharging section for supplying paper to the image forming section and discharging the paper on which the image obtained by the image forming section has been output. There is.

The image scanning section includes an illumination device that illuminates the document placed on the document table, and an optical device that transmits reflected light from the document.

The image forming section includes a photoconductor that is movably (rotatably) formed and that sequentially generates electrostatic latent images corresponding to the light transmitted by the image scanning section, and a charging device that charges the photoconductor. , a developing device that visualizes the electrostatic latent image formed on the photoreceptor, a transfer device that transfers the developed image to paper, a fixing device that fixes the image transferred to the paper, and the photoreceptor in their initial state. It is equipped with a cleaning device that returns the

The feeding/discharging section includes a paper cassette that stores paper, a paper feeding device that supplies the paper to the image forming section, and a discharging section that discharges the paper on which the image has been transferred.

In such an electrostatic image forming apparatus, an image on a document is created by supplying a developer such as colored powder (toner) to an electrostatic latent image generated on the surface of a photoconductive photoreceptor through a developing device. The image is visualized, transferred to a sheet of paper by a transfer device, and heated and pressed by a fixing device to be fixed to the sheet of paper.

(Problem to be Solved by the Invention) By the way, if there are many black bones in the original image, the amount of toner that adheres when the image is transferred to paper inevitably increases. If such a large amount of toner is attached to the leading edge of the sheet in the moving direction, the toner will be welded and wrapped around the fixing roller when the sheet passes through the fixing device, causing a jam.

For example, in the case of automatic same-side copying in which images are output twice on the same side of paper P, as shown in FIG.
When the first image is transferred to the paper P by a transfer device (not shown), the toner 505 attached to the leading edge of the paper P in the paper movement direction due to the above process is fixed by the fixing device 507. It passes through rollers 509 and 51.1 and is heated under pressure to form a band-shaped fixed portion 513.

The paper P discharged from the fixing device 507 passes through the switching gate 5
14 and the same-plane stack section 5 through the same-plane conveyance path 515.
17, and then the same-side copy transport paths 519 and 5 are moved as shown by broken lines in order to enter the second copying process.
21, the paper is again fed to the lower part of the photoreceptor 503, and the paper P
The second image is duplicately copied on the same side of the image.

During this second copying operation, new toner adheres to the band-shaped fixed portion 513 at the leading edge of the paper P through the above-described process, and this toner is transferred to the original band-shaped fixed portion by the fixing device E507 as a new band-shaped fixed portion. It may be superimposed on 513. Band-shaped fixed portion 5 of paper P generated in this way
13 is welded to the fixing roller 509 on the upper side when passing through the fixing device 507, and the paper P tends to get wrapped around it, causing a jam. Such a problem is caused by the peeling claw 523.5 provided on the fixing device 507 to prevent wrapping.
This is likely to occur when the tip of the 25 is worn out and flattened.

Furthermore, if the document is scanned while the platen cover that holds the document against the document table is left open, the light irradiated onto areas other than the document will not be imaged on the photoreceptor. As a result, unnecessary charges around the original image are not removed, and a large amount of toner adheres to areas other than the original image during development, resulting in paper wrapping jam in the fixing device as described above. become.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to prevent the colored powder transferred to the paper from becoming entangled due to welding when the paper passes through a fixing device.

[Structure of the invention]

(Means for Solving the Problem) In order to solve the above-mentioned problem, the present invention provides a non-image portion forming means for forming a non-image portion at a desired portion of an image carrier where a latent image corresponding to a document is formed. and to the paper to which the latent image formed on the image carrier is transferred after being visualized,
a sheet feeding means that repeatedly feeds the image carrier without reversing the front and back sides; and at least the leading edge side in the sheet movement direction when the sheet feeding means operates to transfer the visualized image to the surface of the sheet. The apparatus further includes a control means for operating the non-image portion forming means so that a predetermined area of the area becomes a non-image portion.

(Function) When the paper supplying means that supplies the paper to the image carrier without reversing the front and back sides of the paper is operated, the non-image portion forming means, in response to a command from the control means, forms a non-image portion at least at the leading edge side in the paper movement direction. There is no fixed portion of colored powder in this leading end portion, and the paper is prevented from being wrapped around the fixing device.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a structural block diagram of a copying machine as an image forming apparatus of the present invention, FIG. 2 is a front sectional view of the copying machine, and FIG. 3 is a perspective view of its appearance. On the top surface of the copying machine main body 1, there are a platen glass 3 serving as a document table supporting a document tray, and
An openable and closable platen cover 5 is provided as a document presser for pressing the document against the platen glass 3.

Inside the copying machine main body 1, there are an image scanning section 7 that scans the document sheet on the platen glass 3 in the direction of the arrow, and an image scanning section 7.
An image forming section 9 which exposes the light transmitted by the image forming section 9 and transfers and fixes it onto the paper P, and a paper supply device 11 which supplies the paper P to the image forming section 9 and discharges the transferred paper P are provided. .

At the top of the main body of the copying machine, there is provided an original supply device 13 that supplies an original onto a platen glass 3 and discharges the original after scanning.

The image scanning unit 7 includes an exposure lamp 15. which is provided in a first carriage (not shown). a mirror 17, a mirror 19, 2 provided on a second carriage (not shown), and a lens 23. It is constituted by a mirror 25, and the first. When the second carriage scans in the direction of arrow A, the original image produced by the original is bent by the mirror 17, etc., and forms a slit-like image on a photoreceptor 27 as an image carrier (described later) in the image forming part 9 as an exposure part 29. It is designed to be imaged.

Image formation 1159 is performed by photoconductor 27 rotating in the direction of arrow B.
, a charging device 31 that charges the photoreceptor 27, and a developing device 3 that attaches colored powder such as toner to the electrostatic latent image formed by slit exposure in the exposure section 29 to form a visible image.
3. A transfer device 37 that transfers the toner to the paper P fed by the aligning roller 35 of the paper supply device 11 and in close contact with the photoreceptor 27; a peeling device 39 that peels the paper P from the photoreceptor 27; a toner remaining on the photoreceptor 27; a cleaning device 43 that scrapes off the toner with a cleaning blade 41; a static eliminator 45 that removes residual charges on the photoreceptor 27;
The fixing device 47 heats and fixes the toner on the paper P separated from the paper P.

The paper feed device 11 is a paper feed device that feeds paper P in a paper feed cassette 49 that is detachably installed in the copying machine main body 1 to the photoreceptor 27, and discharges the paper P on which the original image has been transferred and fixed. 51, and a paper supply unit that transports the ejected paper P to the paper refeeding stack section 53 for same-sided copying or double-sided copying, and feeds the paper P to the aligning roller 35 either as is or with the front and back reversed. Paper refeeding device 5 as
5.

The paper feed device 51 includes a take-out roller 59 that descends and rotates to take out a sheet of paper P from the paper feed cassette 49, a paper guide 61 that guides the taken-out paper P to the aligning roller 35, and a paper guide 61 that guides the taken out paper P to the aligning roller 35. an aligning roller 35 that feeds the paper P to the photoconductor 27 with its leading edge aligned at right angles to the feeding direction; a conveyor belt 63 that feeds the paper P from the peeling device to the fixing device 47; a paper discharge roller 65; A first switching gate 69 for sending the paper P from the roller 65 to either the paper discharge tray 157 or the paper refeeding device 55
It is composed of

The refeeding device 55 includes a stack conveyance path 71, a plurality of conveyance rollers 73, a take-out roller 75 that takes out the sheets P in the re-feed stack unit 53 one by one, and aligns the sheets P from the take-out roller 75. The first pass 77 transports the paper P to the roller 35 (with the front and back reversed), and the aligning roller 35 makes a U-turn on the paper P taken out from the take-out roller 75.
a second bus 79 for sending the paper P taken out from the take-out roller 75 to either the first bus 77 or the second bus 79; A plurality of conveying rollers 83 for conveying
, 85.87, and the paper P passing under the second switching gate 81
Forward rotation to take into the second pass 79 or second pass 7
and a reversing roller 89 that performs reverse rotation in order to send out the paper P in 9 to transport rollers 85 and 87.

On the other hand, the document supply device 13 includes a take-out roller 93 for taking out documents stacked on a document tray 91, a supply roller 95 for taking out a single document document, and a separation roller 97.
and a registration roller 99 for aligning the leading edge of the original.
．． 101 and set the document tray on the platen glass 3.
Or the conveyor belt 10 for retracting the set original paper
3, a switching gate 1041 and a reversing roller 105, 107, for reversing the document tray as the document tray moves backward.
109, and a discharge roller 113 for discharging the document on the platen glass 3 to the document discharge tray 111.

An erasing array 1 is provided between the charging device 31 around the photoreceptor 27 and the exposure section 29 as an example of a non-image area forming means 121 that makes it impossible to form a latent image on a predetermined portion of the photoreceptor 27.
23 is provided. The erasing array 123 is activated by the controller 131 when the same side mode, which forms an image overlappingly on one side of the sheet P, is instructed by turning on the same side copy key 127 of the operation panel 125 shown in FIG. The light emitting element lights up for a predetermined period of time according to the command. As a result, the photoreceptor 2
7 is removed by a predetermined width, and the image M is formed on the paper P shown in FIG. 4 in the paper movement direction (arrow A direction).
The tip side portion becomes a non-image portion by a predetermined width W.

In the erasing array 123, as shown in FIG. 5, a plurality of light-shielding cells 133 are arranged in the longitudinal direction of the photoreceptor 27, and a light-emitting element made of, for example, a light-emitting diode is provided inside the light-shielding cell 133, and a light-shielding element is provided inside the light-shielding cell 133. A condensing lens 135 is provided at the tip of the cell 133.

As shown in FIG. 3, the operation panel 125 includes a copy key 137, a number setting key 139 for setting the number of copies, and
In addition to the magnification setting key 140, a same-side copy key 127 for performing a same-side copy, a double-sided copy key 141 for performing a double-sided copy, an erase mode key 143 for specifying an erase operation by the non-image portion forming means 121, An erasure range setting key 145 and the like for setting and changing the width W of the non-image area are provided.

Setting and changing the width W of the non-image area, which is the active area of the erasing array 123, is performed according to the procedure shown in the flowchart of FIG.

The control means 131 is provided with an erasing range memory 147 whose memory size corresponds to the effective photosensitive area of the photoreceptor 27, and the erasing mode key 143 is used to call up an adjustment mode for adjusting the erasing range (step S1). , Step S2) calls up an erasing width adjustment mode for the leading edge of the paper P, and then it is determined whether or not to change the erasing width (Step S3). If the erase width is to be changed here, the erase range memory 147 is rewritten by operating the erase range setting key 145 (step S4); if not changed, the previous adjustment value is used, and in each of these states the erase range memory 147 is rewritten (step S4). 123 is in a standby state.

The image forming operation when the width W of the non-image area is set as shown in FIG. 6 will be explained based on the flowchart in FIG. 7.

When the paper feed cassette 49 is set at a predetermined position in the copying machine main body 1, the number of copies is set using the number setting key 139 (step 511), and the copy key 137 is pressed (step 512), the control means A document feed command is issued from 131, and the document from the document tray 91 is taken out by the take-out roller 93, and the document is sent to the supply roller 99, separation roller 97, registration rollers 99, 101, and conveyance belt 10.
3 operates to set the document tray at a predetermined position on the platen glass 3. Further, a paper feeding command is issued from the control means 131 to the paper feeding device 51, the paper P in the paper feeding cassette 49 is taken out by the take-out roller 59, and the paper is fed from the aligning roller 35 to the lower part of the photoreceptor 27.

A scanning command is output from the control means 131 to the image scanning section 7, and the first. The second carriage performs scanning movement, and the original image on the set original tray is transferred to the rotating photoreceptor 2.
7 is exposed in the form of a slit. Here, if the erase mode key 143 is not pressed (step 813), the memory contents of the erase range memory 147 are not transferred and the erase array 123 does not operate, so that a normal latent image with no non-image area is generated. It is formed on the photoreceptor 27. Toner is attached to this photoreceptor 27 by the developing device 33 to form a visible image, and this visible image is transferred onto the paper P by the transfer device W37. Thereafter, the paper P is peeled off from the photoconductor 27 by the peeling device 39 and sent to the fixing device 47 by the conveyor belt 63, and the toner on the paper P is fixed to the paper P by fixing rollers 47a and 47b to form a normal image. is performed (step 51)
4) Excreted.

When the erase mode key 143 is pressed (step 513) and the same side copy key is pressed (step 15), the contents of the erase range memory 147 are transferred to the register 159 of the non-image portion forming means 121 according to a command from the control means 131. (Step 516), all the light emitting elements of the erasing array 123 are turned on, and the photoreceptor 27 is irradiated over its entire length in the axial direction. This irradiation is performed by the clock 16 of the control means 131.
According to No. 1, the irradiated portion of the photoreceptor 27 is discharged for a period of time corresponding to the leading end portion of the image M formed on the paper P, and is not charged even when exposed by the exposure section 29. An image is formed with a non-image area over the width W on the leading edge side of the paper P (step 517).
).

In the case of this same-side copying, the paper P that has been copied for the first time leaves the paper discharge roller 65, passes through the first switching gate 69 facing upward, is transported within the stack conveyance path 71, and is transferred to the copy side. The paper is stored in the paper refeeding stack section 53 with the paper facing upward. The first copy is completed for the set number of sheets (step 51).
8) and the original paper on the platen glass 3 is the paper ejection roller 1]
3, the paper is ejected onto the ejection tray 111, and the document tray,
The original sheet for second copying on 91 is set on platen glass 3 (step S19, 520).

Then, according to a command from the control means 131, the second switching gate 8
As shown in FIG. 2, the sheet P maintains a posture facing the second bus 79, and the take-out roller 75 of the sheet refeeding stack section 53 rotates while descending, so that the leading edge of the sheet P is now the rear end in the direction of travel. The paper P then passes under the second switching gate 81 and is fed into the second bus 79 by a reversing roller 89 rotating in the direction of arrow R in FIG. Then, the reversing roller 89 starts rotating in the opposite direction to the arrow R, and the paper P makes a U-turn, and the leading edge of the first copy becomes the leading edge again, and the conveying rollers 85 and 87 move the paper P so that the copy surface is facing up. The paper is fed from the aligning roller 35 to the photoreceptor 27 while remaining as follows.

As a result, steps 313 to 318 are repeated again, and the image M of the second original document is duplicately copied onto the paper P by the normal image forming operation.

In such a same-side copying operation, there is a non-image area on the leading edge side of the paper moving direction compared to the image M, so when passing through the fixing rollers 47a and 47b, the non-image area side is on the leading edge side. The paper P is prevented from being wrapped around the paper P due to toner adhesion at this portion, and the fixing operation is performed normally.

The above-mentioned erasing array 1 is used as the non-image area forming means 121.
Instead of the charging device 23, the charging device 31 already installed in the image forming section 9 can be used. That is, it is sufficient to prevent the charging device 31 from charging the photoreceptor 27 for a predetermined period of time, so that the latent image is not formed over a predetermined width over the entire length of the photoreceptor 27. In this embodiment, the setting and changing operation of the width W of the non-image area, which is a non-operating area where charging is not performed, is also performed according to the flowchart shown in FIG. 6, and the image forming operation is also performed according to the flowchart shown in FIG. 7. This is done according to a flowchart.

According to this embodiment, in addition to the effect of the above embodiment that it is possible to form a non-image area that is effective in preventing the paper P from wrapping around,
Since the existing charging device 31 can be used as the non-image portion forming means 121, there is no need to add a dedicated member for forming the non-image portion.

Further, when the platen cover 5 is open, the platen cover sensor 129 may detect this, and based on this detection signal, the non-image area forming means 121 may be operated to form the non-image area. .

Next, a case will be described in which images are formed on both the front and back sides of the paper P. In this case, the second switching gate 81 is switched to the position where the first bus 77 is opened and the second bus 79 is closed, as shown in FIG. In this case, after the copying operation of the first side is completed, the copy side becomes the top side and the paper re-feeding stack unit 53
The paper P stored therein is sent out into the first pass 77 by the take-out roller 75 with the rear end thereof being the leading edge in the direction of travel, and is exposed to light from the aligning roller 35 with the copy surface facing downward. The paper is fed to the lower part of the body 27, transferred to the second surface, and fixed under pressure by fixing rollers 47a and 47b.

In double-sided copying mode, when copying the first side, the paper P
When the above-mentioned band-shaped fixed portion is formed at the rear end in the moving direction of the paper P, this band-shaped fixed portion becomes the leading edge of the paper P and passes through the fixing rollers 47a and 47b during the copying operation of the second side. During the fixing operation for the second side, there is a risk that the band-shaped fixing portion will be welded and the paper P will be wrapped around it.

Therefore, in this double-sided copying, the erasing range memory 147 is set in accordance with the flowchart of FIG. 6 so that the trailing edge of the paper P becomes the non-image area. Then, the image forming operation is performed in step 51 as shown in FIG.
Up to 3 are the same as the same-sided copy, and double-sided copy key 1
41 is pressed (step 521), and the paper feed sensor 163, which is a type of reflective photosensor provided on the paper guide 61, detects the removal of paper from the paper feed cassette 49 and operates (step 522). Control means 131
The contents of the erase memory 147 are transferred to the register 159 of the non-image portion forming means 121 (step 523).
), the erasing operation by the non-image portion forming means 121 is performed according to the clock 161 for a time period corresponding to the trailing edge portion of the image M formed on the paper P, and an electrostatic latent image is formed on this portion of the photoreceptor 27. As a result, an image is formed on the first side of the paper P with a non-image portion over the width W at the rear end side of the paper P (step 524).

When copying the second side of paper P, the paper feed sensor 16
No. 3 does not perform a detection operation, so a normal image forming operation is performed.

According to this embodiment using double-sided copying, since the portion of the paper P that becomes the leading edge when copying the second side is a non-image portion, no toner sticking portion is formed in this portion.
Therefore, in the copying operation of the second side, the non-image portion passes through the fixing device 47 as the leading edge, so the paper P does not wrap around the fixing roller 47b, and is fixed and ejected. Paper operations occur normally.

In each of the above embodiments, the non-image area is formed at the trailing edge or leading edge of the paper, but the invention is not limited to this.
The non-image portion may be formed in a frame shape over the entire circumference.

〔Effect of the invention〕

As described above, according to the present invention, when overlapping images are formed on the same side of a sheet of paper, at least a portion closer to the leading edge in the paper moving direction than the image to be formed becomes a non-image portion, and there is no colored powder. Since no sticking portion is generated, it is possible to prevent the paper from wrapping around the fixing device.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the configuration of a copying machine showing an embodiment of the present invention, Fig. 2 is a front cross-sectional view of the copying machine, Fig. 3 is an overall perspective view of the copying machine, and Fig. 4 is formed on a document. FIG. 5 is a perspective view showing an example of an erasing array;
Fig. 6 is a flowchart for setting the erasing range, Fig. 7 is a flowchart for explaining the operation, Fig. 8 is a cross-sectional view of the main parts of a copying machine showing double-sided copying operation, and Fig. 9 is a toner using a conventional device. FIG. 3 is an explanatory diagram showing a state of formation of a fixed portion. 3...Platen glass (document table) 5...Platen cover (document holder) 27...Photoreceptor (image carrier) 55...Paper refeeding device (paper supply means)] 21... Non-image area forming means 123...erasing array

Claims (5)

[Claims] (1) A non-image area forming means for forming a non-image area at a desired part of an image carrier where a latent image corresponding to a document is formed; a paper supply means that repeatedly supplies the image bearing member with respect to the paper to be transferred after being visualized, without reversing the front and back sides of the paper; and when the paper supply means operates, the visualized image is transferred onto the surface of the paper. An image forming apparatus comprising: a control means for operating the non-image portion forming means so that at least a predetermined area on the leading edge side in the sheet movement direction becomes a non-image portion during transfer. (2) Claim 1, wherein the non-image area forming means is capable of changing the width of the non-image area in the sheet movement direction.
The image forming apparatus described above. (3) Claim 1, wherein the non-image area forming means comprises a light-emitting member that removes the charge on the image carrier.
or the image forming apparatus according to 2. (4) The image forming apparatus according to claim 1 or 2, wherein the non-image area forming means is configured so as not to charge the image carrier for a predetermined period of time. (5) A claim characterized in that a detection means is provided for detecting that a document presser that presses the document against the document table is released, and the non-image portion forming means is operated based on the detection operation of the detection means. 5. The image forming apparatus according to 1, 2, 3 or 4.