JP3769973B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic system or an electrostatic recording system capable of forming an image on both front and back surfaces of a recording material, for example, a tandem color having endless recording material conveying means such as a transfer belt The present invention relates to an image forming apparatus that can be suitably used in a copying machine, a color printer, or the like.
[0002]
[Prior art]
As shown in FIG. 4, in a tandem type color copying machine or the like, a recording material fed by a sheet feeding unit 101 from within a sheet feeding cassette 101a to 101d is transferred to an endless annular transfer belt (recording material by a timing roller 161. The image forming means 106 forms an image on the recording material while the recording material is carried by the transfer belt 105 and conveyed by the transfer belt 105, and the recording material is unloaded from the transfer belt 105 and sorted. The recording material is discharged to the recording material discharge unit 103.
[0003]
In such a copying machine, there is provided a reversing unit 109 for inverting the recording material so that an image can be formed on both sides of the recording material. When performing duplex copying, an image is formed on one side. Then, the recording material carried out from the transfer belt 105 is reversed by the reversing means 109 and returned to the paper feeding side via the circulation path 110, and again fed to the transfer belt 105 by the timing roller 161, and the recording material. An image is formed on the back side of the image.
[0004]
[Problems to be solved by the invention]
However, in the conventional color copying machine, when performing double-sided copying, the recording material formed on one side and transported from the transfer belt 105 is returned to the paper feeding side by the circulation path 110. In addition, it is necessary to equip the circulation path 110 separately, so that there is a problem that the apparatus becomes larger and the structure becomes complicated, and the cost increases.
[0005]
The present invention solves the above-described problems of the prior art, and can surely form images on both sides of the recording material, as well as reducing the size and structure of the apparatus, thereby reducing the cost. An object is to provide an image forming apparatus.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention comprises a recording material conveying means having first and second positions, formed endlessly and driven to circulate, and carrying and conveying a recording material, and the recording material conveying means Forming an image on a recording material provided oppositely between the first position and the second position and conveyed from the first position toward the second position by the recording material conveying means Means, a first feeding means for feeding the recording material arranged at a predetermined position upstream of the first position of the recording material conveying means, and a downstream of the second position of the recording material conveying means. Reversing means for reversing the unloaded recording material; and second feeding means for feeding the recording material reversed by the reversing means downstream of the second position in the circulation direction of the recording material conveying means; An image forming apparatus provided with
[0007]
In the image forming apparatus of the present invention, the recording material on which an image is formed on one surface is fed downstream of the second position at the downstream end of the image forming area in the endless recording material conveying means, and the recording material conveying means Thus, the image can be conveyed to the image forming area and an image can be formed on the other surface. Therefore, it is not necessary to provide a separate circulation path or the like for returning the recording material on which the image is formed on one surface to the first position at the upstream end of the image forming area in the recording material conveying means. Can be omitted.
[0008]
Note that the recording material returned to the image forming area by the recording material conveying means forms an image on the other side by the image forming means, so that an image can be reliably formed on both surfaces of the recording material.
[0009]
In the present invention, it is preferable to employ a configuration that further includes a cleaning unit for removing adhered contaminants and residual charges of the recording material conveying unit.
[0010]
That is, when this configuration is adopted, contaminants such as toner and oil and residual charges are removed from the recording material conveying means, so that adverse effects due to the contaminants and residual charges are avoided, and high quality images are formed. can do.
[0011]
Further, in the present invention, a fixing unit for fixing an image formed on the recording material is provided between the second position and the reversing unit, and the recording material conveying unit is configured to form an image on one surface. The recording material unloaded from the downstream of the second position is reversed by the reversing means without fixing the image, or between the second position and the reversing means, Fixing means for fixing an image formed on the recording material is provided, and the recording material on which the image is formed on one surface and carried out from the downstream of the second position of the recording material conveying means is fixed to the image. It is possible to suitably employ a configuration in which the image is fixed by the means and reversed by the reversing means.
[0012]
As described above, since the fixing unit can be provided on the downstream side or the upstream side of the reversing unit in accordance with the apparatus structure, the fixing unit can be reliably installed while ensuring the flexibility of design. Further, the image formed on the recording material can be fixed by the fixing means, and an image in a stable state can be formed.
[0013]
In the present invention, it is preferable that the second feeding unit has a configuration having a timing roller that feeds the recording material to the recording material conveying unit at a predetermined timing.
[0014]
That is, when this configuration is adopted, for example, the recording material can be placed so as not to cover the seam of the recording material conveying means, and adverse effects due to the seam can be avoided.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic sectional view showing a main part of image formation in an electrophotographic full-color copying machine to which an image forming apparatus according to an embodiment of the present invention is applied.
[0016]
As shown in the figure, this image forming apparatus has four image forming means Pc, Pm, Py, Pk in the apparatus, a sheet feeding unit 1 on the lower side, and a fixing device (fixing means) 2 on the left side. Is arranged. Further, a sorter 3 is arranged on the left side of the fixing device 2. The sorter 3 has a staple function and a shift tray function.
[0017]
Between the fixing device 2 and the sorter 3, a paper reversing unit 9 for reversing and discharging the paper is provided. In addition to reversing the paper, the paper reversing means 9 also serves as a means for switching whether to discharge the paper to the sorter 3 or to guide the paper to a return path area 5R of the transfer belt 5 described later for back side copying. Yes.
[0018]
An endless annular transfer belt 5 (recording material conveying means) that carries and conveys paper is stretched between a plurality of rollers (not shown) below the conveyance path from the paper supply unit 1 to the fixing device 2. ing.
[0019]
The transfer belt 5 is formed by joining both end portions of a film sheet made of a resin having semi-conductive (or conductive) characteristics in an endless manner by means such as fusion, and is driven by a driving roller (not shown). Circulation driven at a constant speed in the direction of the arrow.
[0020]
The transfer belt 5 has an upper side (image forming means side) configured as a forward path region 5G and a lower side (paper feeding unit side) configured as a return path region 5R. Is carried to the image forming means Pc, Pm, Py, Pk sequentially. In this embodiment, the upstream end is configured as the first position and the downstream end is configured as the second position with respect to the circulation direction in the forward path region 5G of the transfer belt 5. Further, an area between the first position and the second position of the transfer belt 5 is configured as an image forming area.
[0021]
A first adsorbing means (first supporting means) 51 is provided at an upstream end of the forward belt region 5G in the transfer belt 5 with respect to the belt rotation direction, and an upstream end of the backward region 5R is provided at the upstream end of the forward belt region 5G. A second adsorbing means (second carrying means) 52 is provided, and the adsorbing means 51 and 52 are configured so that the paper can be adsorbed and carried electrostatically on the transfer belt 5 reliably.
[0022]
A neutralization charger 53 is provided on the downstream side of the image forming means Pk in the forward path region 5G of the transfer belt 5, and the sheet adsorbed on the transfer belt 5 can be separated by the neutralization charger 53. It is configured.
[0023]
Further, a cleaner means 54 for removing the toner adhering to the belt 5 and an oil collecting means for recovering and removing the fixing oil adhering to the belt 5 are provided at a turn-back portion of the transfer belt 5 from the forward path area 5G to the return path area 5R. In addition to 55, there are provided static eliminating means (not shown) for removing residual charges, and these means constitute a cleaning means.
[0024]
The image forming units Pc, Pm, Py, and Pk have substantially the same configuration, and photosensitive drums 6c, 6m, 6y, and 6k are arranged as image carriers that are rotationally driven in the directions of the arrows in the drawing. Yes. Although not shown, a charging charger that uniformly charges each photosensitive drum, a developing device that develops an electrostatic latent image formed on each photosensitive drum, and the like are developed around the photosensitive drum. A transfer charger for transferring the toner image to the paper and a cleaner for removing the toner remaining on the photosensitive drum are sequentially arranged in the rotation direction of each photosensitive drum. Note that cyan toner is used for the developing unit of the image forming unit Pc, magenta toner is used for the developing unit of the image forming unit Pm, yellow toner is used for the developing unit of the image forming unit Py, and image forming unit. Each of the Pk developing devices stores black toner.
[0025]
Image exposure devices 7c, 7m, 7y, and 7k are provided above the photosensitive drums 6c, 6m, 6y, and 6k. These image exposure devices 7c, 7m, 7y, and 7k are composed of a semiconductor laser, a polygon mirror, an fθ lens, and the like. Upon receiving an electric digital image signal, a laser beam modulated in accordance with this signal is supplied to a charging charger. The photosensitive drums 6c, 6m, 6y, and 6k are scanned between the developing units in the direction of the generatrix to expose the drum surface, and electrostatic latent images are formed on the photosensitive drums.
[0026]
An image signal corresponding to the cyan component of the color image is formed in the image exposure device 7c of the image forming means Pc, and an image signal corresponding to the magenta component of the color image is formed in the image exposure device 7m of the image forming means Pm. An image signal corresponding to the yellow component of the color image is input to the image exposure device 7y of the means Py, and an image signal corresponding to the black component of the color image is input to the image exposure device 7k of the image forming means Pk.
[0027]
The paper feed unit 1 includes a plurality of paper feed ports 1a to 1d in which paper feed cassettes and manual trays for storing different sizes of paper are set, and a paper feed unit for feeding paper one by one from each paper feed port. Paper rollers 11a to 11d.
[0028]
Further, a first sheet for feeding a sheet fed by the sheet feeding unit 1 to a position upstream of the forward path region 5G on the transfer belt 5 between the sheet feeding unit 1 and the transfer belt 5 at a predetermined timing. A timing roller 61 is provided, and a sheet reversed by the sheet reversing unit 9 is fed between the sheet reversing unit 9 and the transfer belt 5 to a position upstream of the return path region 5R on the transfer belt 5 at a predetermined timing. A second timing roller 62 is provided.
[0029]
In the present embodiment, the first feeding unit is configured by the sheet feeding unit 1 and the first timing roller 61 and the second feeding unit is configured by the sheet reversing unit 9 and the second timing roller 62 and the like. A sending means is configured.
[0030]
FIG. 2 is a plan view showing a part of the operation panel 200 of the full-color copying machine of FIG. As shown in the figure, the copying machine can set various copy modes and start a copy operation by using the operation panel 200, and can notify the setting state of the copy mode and the apparatus state by display.
[0031]
That is, the number setting unit 201 is a key group for setting the number of copies or clearing the set number of copies.
[0032]
A print key 202 is a key for starting a copying operation, a copy interruption key 203 is a key for interrupting a copying operation in operation, and a density setting key 204 is a key for adjusting the density of an image to be copied. The magnification setting key 205 is a key for setting the scaling ratio of the image to be copied, and the color mode selection key 206 is used to set whether the color of the image to be copied is printed in full color or black. It is a key to do.
[0033]
A double-sided key 207 is a key for setting whether to print an image to be copied on only one side or both sides of a sheet, and a cassette selection key 208 is used for the first to fourth feed cassettes. This is a key for selecting which cassette paper is used for the copying operation.
[0034]
The number display section 210 is a display section that displays the set number of sheets or the number of remaining copies during the copying operation, and the magnification display section 211 is a display section that displays the set variable magnification, and the liquid crystal display section 212. Is a multi-purpose display unit that displays a large amount of information such as various copy modes and apparatus states other than the sheet size scaling factor.
[0035]
FIG. 3 is a block diagram showing an overall control system of the full-color copying machine shown in FIGS.
[0036]
This full-color copying machine has an image reader (IR) that reads image information of a document as a function of a copying machine, in addition to the main image forming portion and panel portion described in FIGS. An automatic document feeder (ADF) that feeds and conveys images sequentially to the image reading unit of the image reader is provided. These drive units are controlled by the control means shown in FIG. Is called.
[0037]
In the control unit of FIG. 3, a system controller 301 is a control unit that performs overall control of the entire image forming apparatus.
[0038]
The ADF control unit 302 feeds and conveys the originals one by one to the image reading unit of the image reader, and controls the original feeding device to discharge the originals to the original output unit when the image reading is completed. It is a control unit.
[0039]
The IR control unit 303 is a control unit that performs scanning speed control and position control of a scanner for reading a document image.
[0040]
The image processing control unit 304 is a control unit that performs an operation instruction of the multi-memory image control unit 312 according to a copy sequence and a copy mode. Specifically, the image signal processed in the scanner image processing unit 311 is recorded in units of pages of the document, and the stored image unit of the document in page units is selected in the order according to the copy sequence, etc. A control for sending an image signal to the gradation processing unit 313 and a control for rotating the image direction by 90 degrees or 180 degrees according to a copy mode or the like are performed.
[0041]
The panel control unit 305 is a control unit that performs key input processing and display of the operation panel 200 as described with reference to FIG.
[0042]
The main body control unit 306 controls the paper feeding unit 1 described in FIG. 1, the control of the fixing device 2, the control of the transfer belt 5, the control of the photosensitive drums 6c, 6m, 6y, 6k and their peripheral devices, and the paper reversing means. 9, a control unit that performs control of the first and second suction means 51 and 52, control of the first and second timing rollers 61 and 62, and the like.
[0043]
The sorter control unit 307 is a control unit that performs paper conveyance / discharge control, bin movement, shift tray position control, and staple operation control in the sorter 3.
[0044]
The image input unit 310 includes a sensor unit including a CCD for reading an image of a document and a circuit unit for digitizing the signal. In this embodiment, the circuit configuration is such that CMYK components are processed simultaneously in parallel.
[0045]
The scanner image processing unit 311 includes a circuit that performs a scaling process, an image shift process, and an erase process on a digitized image signal in accordance with a copy mode or the like.
[0046]
The multi-memory image processing unit 312 includes a memory that stores image information, and a circuit that performs image rotation or image compression / decompression.
[0047]
The gradation processing unit 313 is configured by a circuit that performs conversion to gradation data according to the circuit configuration (e.g., conversion from 8 gradations to 3 gradations).
[0048]
The frame memory 314 is configured by a circuit that temporarily stores a plurality of pages of image signals at the time of duplex copying and outputs a necessary page of image signals at a necessary timing.
[0049]
The registration correction unit 315 delays the image signals corresponding to the CMYK components of the color image by a time corresponding to a timing shift in which the sheet sequentially passes under the image forming units Pc, Pm, Py, and Pk. It consists of a circuit. With this circuit, image signals of CMYK components can be simultaneously processed in parallel from the image input unit 310 to the gradation processing unit 313 or the frame memory 314.
[0050]
The image exposure device 316 corresponds to the reference numerals 7c, 7m, 7y, and 7k in FIG. 1, and each CMYK component is electrostatically charged on the photoreceptors 6c, 6m, 6y, and 6k according to the corresponding image signal. It consists of a circuit that forms a latent image.
[0051]
Next, a copying operation in this copying machine will be described.
[0052]
First, in the image reading unit, the image information of the document read by the image reader is digitized, and the electric digital image signal is input to the image exposure devices 7c, 7m, 7y, and 7k for each CMYK component, The photosensitive drums 6c, 6m, 6y, and 6k are irradiated with a laser beam modulated in accordance with the signal to expose the drum surface, and the CMYK components for the respective components of the photosensitive drums 6c, 6m, 6y, and 6k are exposed. An electrostatic latent image is formed. Further, the electrostatic latent images on the drums 6c, 6m, 6y, and 6k are developed by the developing device, and toner images for each of the CMYK components are formed.
[0053]
On the other hand, in the paper supply unit 1, a sheet (recording material) is conveyed from a predetermined sheet supply cassette or the like to the first timing roller 61, and the sheet is transferred to each photosensitive drum 6 c by the first timing roller 61. , 6m, 6y, and 6k, the toner images are fed to the forward path region 5G on the transfer belt 5 and electrostatically adsorbed and supported on the transfer belt 5 by the first adsorbing means 51. Then, as the transfer belt 5 moves, the sheet sequentially passes under the photosensitive drums 6c, 6m, 6y, and 6k of the image forming units Pc, Pm, Py, and Pk and is conveyed toward the fixing unit 2. At the same time, the toner images for each of the CMYK components are sequentially superimposed and transferred onto the paper by the transfer charger of each image forming unit, and a color image is synthesized.
[0054]
The paper thus passing through the image forming means Pk is neutralized by the neutralizing charger 53 and separated from the transfer belt 5, and then the composite image is fixed by the fixing device 2.
[0055]
During single-sided copying, the paper that has passed through the fixing device 2 is discharged to the sorter 3 by the paper reversing means 9.
[0056]
Further, at the time of duplex copying, the sheet that has passed through the fixing unit 2 is reversed by the sheet reversing unit 9 without being discharged to the sorter 3 and then sent to the second timing roller 62. In the image forming unit, toner images are formed on the photosensitive drums 6c, 6m, 6y, and 6k corresponding to the image to be formed on the back side of the sheet.
[0057]
The sheet conveyed to the second timing roller 62 is returned to the return belt region 5R on the transfer belt 5 by the second timing roller 62 at a timing that matches the toner images of the photosensitive drums 6c, 6m, 6y, and 6k. The sheet is electrostatically attracted onto the transfer belt by the second attracting means 52. As the transfer belt 5 moves, the paper is guided from the return path area 5R to the forward path area 5G, and further sequentially passes through the photosensitive drums 6c, 6m, 6y, and 6k, and the color image is formed on the back side. And fixed by the fixing device 2.
[0058]
The paper on which images are formed on both sides in this way is discharged to the sorter 3 by the paper reversing means 9.
[0059]
As described above, in the copying machine of the present embodiment, when performing double-sided copying, the reversed paper is fed to the lower return path region 5R of the transfer belt 5 and the paper is fed by the transfer belt 5. Since the image is returned to the image forming area, there is no need to provide a separate circulation path for returning the reversed paper to the image forming area of the transfer belt 5, thereby simplifying the structure and reducing the size of the apparatus. In addition, the cost can be reduced.
[0060]
Further, in the present invention, the cleaning means including the cleaner means 54, the oil collecting means 55, the charge eliminating means (not shown) and the like is provided at the folded portion of the transfer belt 5 from the forward path area 5G to the return path area 5R. Contaminants such as oil and oil and residual charges are reliably removed from the transfer belt 5, and adverse effects due to the contaminants can be avoided and high quality images can be formed.
[0061]
In the above embodiment, the transfer belt seam is different in thickness from other portions, and when the sheet is fed to the transfer belt so that the paper is applied to the seam, the transfer from the photosensitive drum to the paper is surely prevented. May have adverse effects. Therefore, in the present invention, the sheet is fed to the forward path area 5G and the return path area 5R of the transfer belt 5 at a timing at which the first and second timing rollers 61 and 62 avoid the seam, or at a timing at which adverse effects due to the seam are avoided. It is also possible to feed.
[0062]
In the above embodiment, the fixing device 2 is provided between the transfer belt 5 and the paper reversing unit 9, and the paper on which single-sided copying has been performed is passed through the fixing device 2 to fix the image, and then double-sided copying is performed. Therefore, the sheet is reversed by the sheet reversing means 9 and fed to the transfer belt return path region 5R. In the present invention, a fixing device is provided between the sheet reversing means 9 and the sorter 3. It is configured so that the sheet on which the one-sided copy is made is not passed through the fixing device, but the sheet is reversed by the sheet reversing means 9 and fed to the return path region 5R of the transfer belt 5 for the two-sided copy. Also good. In this case, the paper is returned by the transfer belt 5 without fixing the image on one side, and there is a concern about the adverse effect on the image. For example, by adopting a suction belt as the transfer belt, Adverse effects can be avoided.
[0063]
Furthermore, since the fixing device 2 can be arranged at any position on the upstream side and downstream side of the reversing means 9 in accordance with the apparatus structure in this way, sufficient design flexibility can be ensured.
[0064]
In the present invention, the second timing roller is not necessarily provided, and the sheet is fed to the return path area of the transfer belt at the timing by the reversing roller provided in the reversing unit. Also good.
[0065]
The present invention is equally applicable to image forming apparatuses having various configurations such as an electrophotographic system and an electrostatic recording system other than those described above.
[0066]
【The invention's effect】
As described above, according to the image forming apparatus of the present invention, the recording material on which an image is formed is fed downstream of the second position downstream of the image forming area in the endless recording material conveying means. Since the recording material conveying means can convey the image to the image forming area and form an image on the other side, a circulation path for returning the recording material on which the image is formed on one surface to the image forming area of the recording material conveying means is provided. There is no need to provide them separately, and accordingly, the structure can be simplified and the apparatus can be downsized, and the cost can be reduced. Further, since the recording material retransmitted to the image forming area by the recording material conveying means forms an image on the other side by the image forming means, there is an effect that images can be reliably formed on both surfaces of the recording material.
[0067]
In the present invention, in the case where the cleaning means for removing the adhering contaminants and charges on the recording material conveying means is provided, contaminants such as toner and oil and residual charges are removed from the recording material conveying means. There is an advantage that a high-quality image can be formed by avoiding adverse effects due to objects and residual charges.
[0068]
In the present invention, the fixing means can be provided on the downstream side or the upstream side of the reversing means in accordance with the apparatus structure, so that the fixing means can be reliably provided while ensuring the flexibility of design. Furthermore, the fixing unit can fix the image formed on the recording material, and a stable image can be formed.
[0069]
Further, in the present invention, when the timing roller is provided in the second feeding unit, it is possible to place the recording material so as not to cover the seam of the recording material conveying unit, and the adverse effect due to the seam can be avoided. There is an advantage that an image of higher quality can be formed.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing a main part of image formation in a full-color copying machine to which an image forming apparatus according to an embodiment of the present invention is applied.
FIG. 2 is a plan view showing a part of an operation panel in the copier according to the embodiment.
FIG. 3 is a block diagram showing an overall control system in the copying machine of the embodiment.
FIG. 4 is a schematic cross-sectional view showing a main part of image formation in a conventional full-color copying machine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Paper feed part 5 ... Transfer belt (recording material conveyance means)
5G: Outward area (image forming area)
9: Reversing means 61, 62 ... Timing rollers Pc, Pm, Py, Pk ... Image forming means

Claims (5)

A recording material transporting means having first and second positions, formed endlessly and driven to circulate, and carrying and transporting a recording material;
An image is formed on the recording material that is provided between the first position and the second position of the recording material conveying unit and is conveyed by the recording material conveying unit from the first position toward the second position. Image forming means for forming
First feeding means for feeding a recording material arranged at a predetermined position upstream of a first position of the recording material conveying means;
Reversing means for reversing the recording material carried from the downstream of the second position of the recording material conveying means;
An image forming apparatus comprising: a second feeding unit that feeds the recording material reversed by the reversing unit downstream of a second position in the circulation direction of the recording material conveying unit. The image forming apparatus according to claim 1, further comprising a cleaning unit for removing contaminants and residual charges on the recording material conveying unit. Fixing means for fixing an image formed on the recording material is provided between the second position and the reversing means,
2. The recording material having an image formed on one surface and transported from the downstream of the second position of the recording material conveying means is reversed by the reversing means without fixing the image. 2. The image forming apparatus according to 2. A fixing unit for fixing an image formed on the recording material is provided between the second position and the reversing unit,
The recording material having an image formed on one surface and transported from the downstream of the second position of the recording material conveying means is configured to fix the image by the fixing means and to invert by the inversion means. Item 3. The image forming apparatus according to Item 1 or 2. The image forming apparatus according to claim 1, wherein the second feeding unit includes a timing roller that feeds the recording material to the recording material conveying unit at a predetermined timing.

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