JP4129589B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus having a duplex mode in which an image is formed on both sides of a recording material.
[0002]
[Prior art]
1. In an electrophotographic image forming apparatus, a toner image is transferred to a recording sheet, and then heat fixing is performed to obtain an image. However, when the image is fixed by heating, the moisture contained in the recording paper is evaporated by heat, so that after the fixing, the shrinkage causes a dimensional change. Although this shrinkage rate varies depending on the type and thickness of the recording paper, it is about 0.1 to 0.5% in length. After that, it takes 15 to 20 minutes to absorb the moisture again and return to its original size. It takes a degree. As the recording paper contracts / extends, the image carried on the recording paper also undergoes a dimensional change.
[0003]
Therefore, in the duplex mode in which image formation is performed on both sides of the recording paper, the image is transferred and fixed on the front surface (first surface), and image formation is performed on the back surface (second surface) with the recording paper contracted. However, when returning to the original size, the image is enlarged, and the magnification is changed on the front and back surfaces.
[0004]
Therefore, for example, in Japanese Patent Laid-Open No. 6-332275, the shrinkage rate is stored in advance for each type of recording paper, and in the double-sided mode, the magnification of the back side image is automatically set by setting the type of recording paper. There has been proposed an image forming apparatus for changing the above. However, this makes it impossible to use a type of recording paper in which the shrinkage rate is not stored in advance.
[0005]
Japanese Patent Application Laid-Open No. 10-149057 discloses an image forming apparatus that measures the shrinkage rate with the first sheet of recording paper and performs image formation on the back side of the second and subsequent sheets at a magnification that matches the shrinkage rate. ing. However, the first recording paper dedicated for measurement and the second and subsequent recording papers imaged on both sides are handled in a mixed manner, increasing the work of selecting only the image-formed recording material, etc. The user had a problem.
2. From the viewpoint of saving resources, recording paper (referred to as backing paper) already formed on one side may be reused for image formation. In some cases, special paper that should be image-formed only on one side is used as recording paper. When such a backing paper or special paper is stored in the paper feeding unit, when the paper feeding unit is manually or automatically selected as a recording paper for image formation and the duplex mode is selected. Therefore, image formation is performed on both sides of the recording paper that should not be image-formed on both sides. In recent image forming apparatuses such as copiers, the paper feed unit has a large number of paper feed trays to store various types of recording paper, and automatically selects the paper feed tray according to the image forming settings. However, since the selection of such a paper feed tray is performed only with the size of the recording paper suitable for image formation, the above-mentioned problem often occurs. If image formation is performed on both sides of the recording paper that the user does not want, naturally the recording paper is wasted.
[0006]
[Problems to be solved by the invention]
The present invention has been made in view of the above problems, and its object is as follows.
1. In the double-sided mode, an image forming apparatus is provided in which the enlargement ratio of the toner images on the front and back surfaces does not change regardless of the type of the recording material, and the user is not troubled manually.
2. Provided is an image forming apparatus that prohibits image formation in a double-sided mode for a recording material that does not want to form an image on both sides and eliminates waste of the recording material.
[0007]
[Means for Solving the Problems]
The above object of the present invention has been achieved by the following constitution.
[0008]
1. A latent image is formed by imagewise exposure to a photoreceptor, and a toner image obtained by developing the latent image is transferred to the first surface of the recording material by a transfer unit, and fixed by a fixing unit. The recording material that has been turned upside down by the reversing means is conveyed again to the transfer area, and a new toner image formed on the photoreceptor is transferred to the second surface of the recording material by the transferring means, and the fixing means is used. In an image forming apparatus capable of image formation in a double-sided mode that is discharged to the outside after fixing,
Between the pre-drum transport roller provided at a position closest to the photoconductor on the upstream side in the transport direction of the recording material with respect to the photoconductor and a registration roller positioned on the upstream side of the pre-drum transport roller; Arranged just before the image is transferred to the recording material Measuring means for measuring the vertical and horizontal dimensions of the recording material;
The shrinkage rate by the fixing means of the recording material is calculated from the longitudinal dimension and the lateral dimension of the recording material measured by the measuring means before and after being fixed by the fixing means, and the magnification according to the shrinkage ratio is calculated. Control means for performing toner image formation on the photoreceptor,
In the duplex mode,
The first recording material is Without transferring the toner image by the transfer means, Used for the calculation of the shrinkage rate,
For the second and subsequent recording materials, a toner image transferred to the first surface is formed on the photoreceptor by normal image formation, and the toner image transferred to the second surface of the same recording material is the first image. Forming a toner image on the photoconductor with a magnification in accordance with the shrinkage calculated by the first recording material;
An image forming apparatus having a measurement mode in which the first recording material and the second and subsequent recording materials are distinguished and discharged to the outside of the apparatus.
[0009]
2. A plurality of discharge trays, wherein the first recording material is discharged to a first discharge tray, and the second and subsequent recording materials are discharged to a second discharge tray; The image forming apparatus described in 1.
[0010]
3. 3. The apparatus according to 1 or 2 above, further comprising a total counter for counting and displaying the number of recording materials discharged outside the apparatus, wherein the first recording material is not included in the count of the total counter. Image forming apparatus.
[0011]
4). 4. The image forming apparatus according to any one of items 1 to 3, wherein the measuring means for measuring the lateral dimension of the recording material is a CCD or a CIS.
[0013]
5 . The measuring means for measuring the longitudinal dimension of the recording material measures the longitudinal dimension by measuring the passing time of the recording material. 4 The image forming apparatus according to any one of the above.
[0014]
6 . Exposure for forming a latent image on the photoconductor is performed by scanning exposure in the horizontal direction with a laser beam while moving the photoconductor in the vertical direction. The combined toner image is formed by changing the magnification of the vertical dimension by changing the moving speed of the photoconductor, and changing the magnification of the horizontal dimension by changing the scanning exposure speed. ~ 5 The image forming apparatus according to any one of the above.
[0015]
7 . The measuring unit also serves as a recording paper misalignment detecting unit, and forms a toner image on the photoconductor in accordance with the recording sheet misalignment detected by the misalignment detecting unit. 6 The image forming apparatus according to any one of the above.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the image forming apparatus of the present invention is applied to a digital electrophotographic copying machine will be described with reference to the drawings. However, the present invention is not limited to this.
[0021]
First, the overall configuration and schematic process of the copying machine will be described with reference to FIG. 1 which is a schematic sectional view of the copying machine.
[0022]
The copying machine of the present embodiment is provided with an automatic document feeder 1 at the top of the copying machine main body, and an image reading device 2, an image forming unit 3, a paper feeding unit 4, a conveying path 5, and A discharge / reversal unit 6 is provided.
[0023]
The automatic document feeder 1 is an apparatus that is provided in the upper part of the copying machine main body, feeds documents one by one, conveys them to the image reading position, and discharges the document after image reading. The automatic document feeder 1 transports a document placed on the document placing table 11 on which the document is placed, a document separating unit 12 that separates the documents placed on the document placing table 11 one by one, and a document separated by the document separating unit 12. A document transport unit 13, a document discharge unit 14 that discharges a document transported by the document transport unit 13, a document discharge table 15 that receives and places the document discharged by the document discharge unit 14, and images on both sides of the document Has a document reversing unit 16 for reversing the front and back of the document when reading.
[0024]
A plurality of documents placed on the document placement table 11 are separated by the document separation unit 12 and conveyed one by one. The document separated and transported by the document separation unit 12 is transported by the document transport unit 13, and the image of the document is read through the slit 21 by the image reading device 2 provided below. The document from which the image has been read is discharged onto the document discharge table 15 by the document discharge unit 14. By the way, when reading images on both sides of a document, the document on which the image on the front side is read is reversed by the document reversing unit 16 and conveyed again by the document conveying unit 13 and then by the image reading unit. The image on the back side of the document is read through the slit 21. Then, the document from which the image on the back side is read is discharged onto the document discharge table 15 by the document discharge unit 14. Such a process is repeated for the number of documents placed on the document placing table 11, and an image of the document is read.
[0025]
Further, the automatic document feeder 1 is configured to be integrally retractable, and the document is directly placed on the platen glass 22 by raising the automatic document feeder 1 and opening the platen glass 22. It is configured to be able to. In the present embodiment, the original image is read while the original is conveyed by the original conveying unit 13. However, the original conveyed by the original conveying unit 13 is stopped on the platen glass 22. You may comprise so that an image may be read above.
[0026]
The image reading device 2 is a unit that reads an image of a document and obtains image data, and is provided at an upper part in the copying machine main body. The image reading device 2 is a slit 21 that is a slit-shaped opening for reading an image of a document conveyed by the document conveying unit 13 of the automatic document feeder 1, and a document table for directly placing a document. A platen glass 22, a lamp 231 that is a light source for irradiating light on a document, and a first mirror 232 that integrates a first mirror 232 that reflects reflected light from the document, and reflects light from the first mirror 232. A V mirror unit 24 in which the second mirror 241 and the third mirror 242 are integrated, and an imaging lens 25 that is an imaging unit for imaging the reflected light from the original on the slit 21 or the platen glass 22 on the CCD 26; A linear CCD 26 is provided as an image reading unit that photoelectrically converts a light image formed by the imaging lens 25 to obtain image data.
[0027]
When the document fed by the automatic document feeder 1 is read by the image reading device 2, the first mirror unit 23 and the V mirror unit 24 have the slit 21 as shown in FIG. It is located below. Then, the document conveyed on the slit 21 by the document conveying unit 13 is irradiated with light by the lamp 231, and the light reflected from the document is a first mirror 232, a second mirror 241, a third mirror 242, an imaging lens. Then, the light enters the CCD 26 via 25. In the CCD, incident light is photoelectrically converted to read an image of a document in the main scanning direction (in the direction perpendicular to the paper surface in FIG. 1), while the document is moved in the sub-scanning direction by the document transport unit 13. The entire image can be read. Image data read by the CCD 26 is appropriately subjected to image processing, and provided to a laser writing system 33 which is an exposure unit described later.
[0028]
When the document is placed directly on the platen glass 22, the first mirror unit 23 and the V mirror unit 24 are moved along the platen glass in the right direction in FIG. Can be read.
[0029]
The image forming unit 3 is a unit that forms an image on a recording sheet that is a sheet-like recording material conveyed at a predetermined process speed Vp based on the image data obtained by the image reading unit 2. The image forming unit 3 of the present embodiment forms an image using an electrophotographic process. The image forming unit 3 has a photoconductive drum 31 having a photoconductive photosensitive layer and carrying a toner image (photosensitive member), a charger 32 for uniformly charging the photosensitive drum 31, and image data read by the CCD 26. A laser writing system 33 that forms a latent image by imagewise laser beam exposure on the photosensitive drum 31; a developing unit 34 that develops the latent image on the photosensitive drum 31 to form a toner image; A transfer unit 35 (transfer means) for transferring the toner image formed on the drum 31 to the recording paper (recording material) conveyed, and separation for separating the recording paper on which the toner image has been transferred from the photosensitive drum 31. And a cleaning unit 37 for removing toner remaining on the photosensitive drum 31 after being transferred, and a fixing unit 38 (fixing unit) for fixing the toner image on the recording paper. Around the photosensitive drum 31, a charger 32, a laser writing system 33, a developing unit 34, a transfer unit 35, a separator 36, and a cleaning unit 37 are arranged.
[0030]
The photosensitive drum 31 is rotated in the direction indicated by an arrow by a drive unit (not shown), and the exposure is started in synchronization with the uniform charging by the charger 32 and the leading edge of the recording paper conveyed from a registration roller 56 described later. A latent image is formed by the laser writing system 33 and developed by the developing device 34, and a toner image based on the image data read by the CCD 26 is formed. The formed toner image is transferred to a recording paper separately conveyed by the transfer device 35. The recording paper on which the toner image has been transferred is separated from the photosensitive drum 31 by the separator 36 and conveyed to the fixing unit 38, where the toner image is fixed on the recording paper by heating and pressing. On the other hand, the photosensitive drum 31 on which the toner image has been transferred to the recording paper is further rotated, and the toner remaining on the photosensitive drum 31 is removed by the cleaning unit 37 and is used for the next image formation.
[0031]
In this embodiment, a pre-drum transport roller 39 for transporting the recording paper fed from the registration roller 56 is provided in the vicinity of the photoconductive drum 31 between the photoconductive drum 31 and the registration roller 56. This contributes to an increase in the conveyance force of the recording paper. Further, between the separator 36 and the fixing unit 38, in order to transport the recording paper separated by the separator 36, a transport roller (not indicated) and a belt (supporting and supporting the back side of the recording paper) Unsigned).
[0032]
The paper feed unit 4 is a paper feed unit that holds a plurality of recording sheets in a stacked state. In the present embodiment, the sheet feeding unit 4 includes a plurality of sheet feeding units 4, that is, a first sheet feeding unit 4 </ b> A, a second sheet feeding unit 4 </ b> B, and a third sheet feeding unit 4 </ b> C. Multiple stages are arranged below the image forming unit 3. As the material of the recording material stored in the paper feeding units 4A to 4C, there are various media such as OHT in addition to recording paper such as plain paper and recycled paper. In addition, there are various recording materials of various materials, such as a back paper and special paper, which should form an image on only one side, and those which can form an image on both sides.
[0033]
The conveyance path 5 is a part of the conveyance unit that conveys the recording material from the paper supply unit 4 to the image forming unit 3, and the recording paper stored in each of the paper supply units 4 </ b> A to 4 </ b> C is transferred to the image forming unit 3. It is configured so that it can be transported.
[0034]
The discharging / reversing unit 6 discharges the recording paper on which the image is formed by the image forming unit 3 onto the recording paper conveyed by the conveying path 5, or reverses the front and back to transfer the photosensitive drum 31. Means for transporting again to the area. The discharging / reversing unit 6 discharges the recording paper on which the toner image has been fixed from the fixing unit 38, the case where the recording paper discharged by the fixing discharging roller 61 is discharged to the outside as it is, and the case where the recording paper is reversed. Switching unit 62 for switching the conveyance path when discharging the sheet to the transfer area in order to form an image on the back side, discharging roller 63 for discharging the recording paper to the outside of the apparatus, and transfer area A reversing unit 65 as a reversing unit for reversing the front and back of the recording paper conveyed again, and a retransmitting unit 66 for reconveying the recording paper reversed by the reversing unit 65 to the image forming unit 3 are provided.
[0035]
When the recording paper on which the image is formed by the image forming unit 3 is discharged as it is, that is, with the image-formed surface facing upward, the switching unit 62 is switched to the position indicated by the alternate long and short dash line in FIG. The paper is discharged to the sorter 64 (outside the machine) by the discharge roller 63. The sorter 64 has ten paper discharge trays 64a, and the recording paper P on which images have been formed can be classified and discharged into the respective paper discharge trays 64a. Further, when the recording paper on which the image is formed is reversed and discharged, that is, when the image-formed surface is discharged downward, the switching unit 62 is switched to the position indicated by the solid line in FIG. The recording paper conveyed by 61 is once conveyed in the direction of the reversing unit 65, and after the recording paper has passed through the switching unit 62, the conveying direction is reversed and discharged by the discharge roller 63 to the sorter 64. On the other hand, when an image is formed on the back side of the recording paper, the switching unit 62 is switched to the position indicated by the solid line in FIG. 1, and the recording paper conveyed by the fixing discharge roller 61 is conveyed in the direction of the reversing unit 65. By performing the switchback by 65, the front and back are reversed and conveyed to the retransmission unit 66.
[0036]
The line sensor 220 as the measuring means of the present invention is disposed between the registration roller 56 and the conveyance roller 39. The position is immediately before the toner image is transferred to the recording paper P, and the size can be measured immediately before the image is formed on the second surface through the fixing unit 38, the reversing unit 65, and the retransmitting unit 66, and an accurate contraction rate is obtained. It is possible and preferable. Further, by setting the position, measurement before and after fixing by the fixing device 38 can be performed at one place and with one measuring means, which is preferable from the viewpoint of cost and error for each measuring means. . Further, as will be described later, the line sensor 220 not only guarantees an accurate toner image magnification on the second surface as a measurement unit, but also functions as a deviation detection unit at the same time. An image can be formed, and a synergistic effect can be expected when a precise image is formed.
[0037]
Next, claims 1 to 7 This invention will be described with reference to FIGS. FIG. 2 is a block diagram showing an example of the electrical configuration of the conveyance unit from the registration roller 56 to the photosensitive drum 31, the line sensor 220 as a measuring unit, and the laser writing system 33 in the copying machine of FIG. is there.
[0038]
In FIG. 2, reference numeral 110 denotes a CPU as control means, which controls the operation of each part of the copier. In the present invention, the shrinkage rate is calculated from the measurement result of the vertical and horizontal dimensions of the recording paper P by the line sensor 220, and the laser. A toner image is formed on the photosensitive member at a magnification corresponding to the shrinkage rate by controlling the writing speed of the writing system 33 and the rotational speed of the photosensitive drum 31 or the conveying roller.
[0039]
That is, the length of the recording sheet P in the conveyance direction when the line sensor 220 as a measuring unit is used when the first side image is formed (before fixing by the fixing unit) and when the second side image is formed (after fixing by the fixing unit). The vertical dimension and the horizontal dimension which is the length in the width direction orthogonal to the conveying direction are measured, and the CPU 110 calculates the shrinkage rate from the measurement result. Then, the CPU 110 controls the exposure speed onto the photosensitive drum 31 (changes the magnification of the horizontal dimension) in accordance with the shrinkage rate, and controls the photosensitive drum 31 or the conveyance rollers (registration roller 56, conveyance roller 39, etc.). The rotation speed is controlled (magnification of vertical dimension is changed), and the magnification of the toner image is changed.
[0040]
In the embodiment of the present invention, the line sensor 220 is a CCD, CIS, or the like, and not only measures the vertical and horizontal dimensions of the recording paper P but also serves as a deviation detection means for the deviation during conveyance of the recording paper P. Also detect. For example, the toner image to be formed in the middle of the recording paper P is not accurately transferred to the transfer area of the recording paper P. Therefore, the deviation in the conveyance direction (vertical deviation) The image is formed at an undesired position due to deviation in a direction orthogonal to the direction (lateral deviation) or deviation from an axis in the conveyance direction (bending deviation), and there is a problem in high-precision image formation. The CPU 110 determines the vertical shift, the horizontal shift, and the bending shift by detecting at which position of the line sensor 220 or at what timing the leading edge of the recording paper P conveyed by the line sensor 220. It will be possible. The CPU 110 controls the recording position by the laser writing system 33 in accordance with this misalignment information, and forms a toner image on the photosensitive drum 31, so that even if the conveyance accuracy of the recording paper P to the transfer area is poor. This makes it possible to transfer the toner image to an accurate position. As described above, immediately before the transfer area, when the toner image is transferred to the first surface of the recording paper P, the conveyance path from the paper feeding unit 4 to the transfer area, and the second surface of the recording paper P When the toner image is transferred to the transfer area, only one line sensor is provided in a portion overlapping with the conveyance path from the re-transmission section 66 to the transfer area. As a result, it is possible to perform both the correction of misalignment and to achieve an image formation with high efficiency and high accuracy as a machine configuration.
[0041]
Reference numeral 120 denotes control for displacing the exposure speed in the main scanning direction (lateral direction in the recording paper P) on the photosensitive drum 31 and the exposure position in accordance with the magnification determined by the CPU 110 and the correction of the deviation during conveyance of the recording paper P. This is a writing control unit to be performed. Reference numeral 33 denotes a laser writing system for writing an image with a laser beam on the photosensitive drum 31 under the control of the writing control unit 120.
[0042]
The processing unit 100 including the CPU 110, the writing control unit 120, and the laser writing system 33 is disposed on the main circuit board of the image forming apparatus.
[0043]
A sensor drive clock generator 210 generates a sensor drive clock for driving the line sensor 220. The sensor drive clock measures the horizontal and vertical dimensions of the recording paper P and detects a deviation. It is configured as follows. Reference numeral 220 denotes a line sensor driven by the sensor drive clock, and includes an LED light source 220a serving as a light emitting unit and a light receiving unit 220b.
[0044]
If the LED light source 220a is a red LED, it is desirable to improve the response. The light receiving unit 220b can use a reading sensor of a facsimile machine. Note that the LED light source 220a and the light receiving unit 220b do not have to have a one-to-one correspondence between the light emitting element and the light receiving element.
[0045]
A sample and hold circuit 230 samples and holds the output of the line sensor 220 in synchronization with the sensor drive clock. A comparator 240 compares the hold result of the sample hold circuit 230 with a predetermined value (recording paper detection level). A counter 250 counts the sensor driving clock when the output of the comparator 240 is in a predetermined state. A serial transmission unit 260 converts the count result of the counter 250 into predetermined serial data and transfers it by serial communication.
[0046]
The sensor drive clock generator 210, the sample hold circuit 230, the comparator 240, the counter 250, and the serial transmitter 260 are arranged in the vicinity of the line sensor 220. M1 is a driving motor for the photosensitive drum 31, and M2 is a driving motor for driving the registration roller 56 and the conveying roller as conveying means for the recording paper P. The rotation speed is changed by a control signal from the CPU 110. The drive is controlled.
[0047]
FIG. 3 is a timing chart showing the operation timing of each component in the duplex mode and measurement mode of the copying machine described with reference to FIGS.
[0048]
First, a double-sided mode is selected from an operation display unit such as a liquid crystal touch panel display of a copying machine, and a measurement mode which is a setting below that is selected (1). The measurement mode is a precision image formation mode in which the shrinkage rate of the recording paper after passing through the fixing means is calculated and reflected in the toner image formation on the second surface in the duplex mode. Therefore, it is possible to select a duplex mode that is not a measurement mode.
[0049]
In this embodiment, it is set to output three sheets of images formed on both the first side and the second side of the recording paper. Next, when the start button of the copying machine is pressed, image formation in the measurement mode is started (2). Since the desired number of recording sheets on which image formation is desired is three sheets, one sheet of measurement recording sheet that is used only for calculating the shrinkage ratio and does not perform toner image transfer is added before that. Then, it is conveyed to the transfer area (3).
[0050]
The first sheet at the top is for measurement used only for measuring the vertical and horizontal dimensions and calculating the shrinkage rate. A line sensor disposed between the registration roller 56 and the conveyance roller 39 is conveyed to the transfer region with the first surface (Table 1) of the first recording paper P facing the photosensitive drum 31. When passing 220, the vertical dimension T1 is detected from the passage time from the front end to the rear end, and the horizontal dimension L1 from the left end to the right end is detected (4, 5). The vertical dimension T1 and the horizontal dimension L1 are dimensions before being fixed by the fixing unit.
[0051]
The first surface (Table 1) of the first sheet, the first surface (Table 2) of the second sheet, the first surface (Table 3) of the third sheet, and the first surface (Table 4) of the fourth sheet are transfer regions. The rotational speed of the photosensitive drum 31 when passing through the rotational speed is the rotational speed A during normal image formation, and the drive motor M1 of the photosensitive drum 31 is driven so as to rotate the photosensitive drum 31 at that speed. (6). Further, the writing control unit 120 controls the horizontal writing speed (main scanning speed) of the laser writing system 33 to be performed at the main scanning speed a during normal image formation (7).
[0052]
In the transfer area, Table 1 is a recording paper dedicated for measurement, so that the toner image is not transferred and is conveyed to the fixing device 38 as it is. In Table 2, Table 3, and Table 4, the toner image is transferred to the fixing unit 38 in the transfer area.
[0053]
Next, the recording paper that has passed through the fixing unit 38 and contracted is reversed by the reversing unit 65, passes through the retransmission unit 66, and this time again with the second surface facing the photosensitive drum 31 again. It is conveyed toward the transfer area (3).
[0054]
When the second surface (back 1) of the first sheet is conveyed from the retransmission unit 66 and passes through the line sensor 220, the vertical and horizontal dimensions after being fixed by the fixing unit are measured in the same manner as described above. The vertical dimension at this time is T2, and the horizontal dimension is L2 (4, 5).
[0055]
From the vertical dimension T1 and horizontal dimension L1 before being fixed by the fixing means and the vertical dimension T2 and horizontal dimension L2 after being fixed, the shrinkage rate is calculated by the CPU as the control means. The contraction rate in the vertical direction is T2 / T1, and the contraction rate in the horizontal direction is L2 / L1. The first sheet for which the measurement of the vertical and horizontal dimensions after fixing is completed passes through the transfer area as it is without transferring the toner image as it is, and is discharged to the discharge tray 1 through the fixing means (8). Since the first sheet is a measurement-dedicated sheet, it is not counted as an image-formed sheet. Therefore, the total counter is not counted (10).
[0056]
On the other hand, the second surface (back 2) of the second sheet, the second surface (back 3) of the third sheet, and the second surface (back 4) of the fourth sheet are formed with a magnification according to the shrinkage rate. In order to transfer the image, image formation is performed at a transfer speed and a writing speed corresponding to the calculated shrinkage rate. That is, the drive motor M1 drives the rotational speed of the photosensitive drum 31 to be the rotational speed A × T2 / T1 obtained by multiplying the rotational speed A at the time of toner image transfer on the first surface by the vertical contraction rate T2 / T1. (6). Further, the main scanning speed to the photosensitive drum 31 by the laser writing system 33 is the main scanning speed a × L2 / L1 obtained by multiplying the main scanning speed a on the first surface by the lateral contraction rate L2 / L1. The write control unit 120 controls (7). Under such control, the second image, the third image, and the fourth image are transferred onto the second surface thereof in the transfer area and conveyed to the fixing means. Are discharged to a discharge tray 2 different from the first recording sheet (9). Since the second, third, and fourth sheets are outputs with desired images formed, they are counted as 1, 2, and 3 in the total counter (10). As the discharge tray 1 or 2, an appropriate one of the ten discharge trays described in FIG. 1 can be selected.
[0057]
As described above, in the measurement mode of the duplex mode, the first sheet of recording paper that is continuously conveyed is used only for obtaining the shrinkage rate, the shrinkage rate is obtained for the first sheet, and the shrinkage rate is obtained. The first image used only for obtaining the second and subsequent toner images on the second surface at a magnification in accordance with the above and for obtaining the shrinkage rate, and the second image on which the toner image is formed By discharging to separate paper discharge trays, it is possible to obtain only the output with the desired image formed without the user performing subsequent sorting operations. Further, since the first sheet is not counted by the total counter, there is an advantage that the number management is easy.
[0058]
next The figure With 4-10 Then, a latent image is formed by imagewise exposure to a photoconductor, and a toner image obtained by developing the latent image is transferred to a first surface of a recording material conveyed from a paper feeding unit by a transfer unit. Then, after fixing by the fixing unit, the recording material reversed by the reversing unit is conveyed again to the transfer area, and a new toner image formed on the photosensitive member is transferred to the second recording material by the transfer unit. In an image forming apparatus capable of image formation in a double-sided mode, which is transferred onto a surface, fixed by the fixing unit, and discharged to the outside of the apparatus, the recording material held by the paper feeding unit is a first surface and a second surface A discriminating unit that discriminates whether or not an image can be formed on both sides of the paper. When the discriminating unit discriminates that the recording material held on the paper feeding unit cannot form an image on both sides, the paper feeding unit The recording material held on the sheet is conveyed to the transfer means. Respect to the image forming apparatus characterized by comprising a prohibiting means for prohibiting the door Give an explanation. FIG. 4 is a diagram illustrating a mode in which a switching member is provided in the paper feeding unit of the copying machine as a determination unit. FIG. 4A is a perspective view showing a state where one of the paper feeding units is pulled out, and FIG. 4B is an enlarged view of a switching member of the paper feeding unit.
[0059]
In the figure, reference numerals 4A to 4C denote the first to third sheet feeding units described in FIG. Each of the three paper feeding units is of a drawer type, and the recording paper is replenished in the drawn state. FIG. 4A shows a state in which the user puts his / her hand on the handle 402 of the third paper feeding unit 4C and pulls it forward (in the direction of the white arrow). In this figure, no recording paper is stored. The third paper feed unit 4C has a part of a paper feed tray 401 that holds a bundle of recording papers. The third paper feeding unit 4C regulates the positions of two adjacent sides of the recording papers in the notch parts. A rear end stopper 403 and a back-side regulating plate 404 are fitted into the fixed position. By changing the positions of the rear end stopper 403 and the back regulating plate 404, recording papers of various sizes can be held in the paper feeding unit.
[0060]
Reference numeral 410 denotes a dial-type switching member as the discrimination means of the present invention. As shown in the enlarged view of FIG. 4B, the user manually rotates the switching member 410 and sets it to a desired mode. In this figure, a state in which “A4 double-sided prohibition” is set in order to store A4 size recording paper on which only one side such as backing paper or special paper forms an image in the third paper feed unit 4C. Represents.
[0061]
As described above, when the user pulls out the paper feed unit when replacing or replenishing the recording paper, the switching member (discriminating means) provided in the paper feed unit is manually operated to set the prohibition of the duplex mode. Thus, it is possible to prevent a problem that the recording paper held in the paper feeding unit is erroneously used for image formation in the duplex mode.
[0062]
FIG. 5 is a block diagram showing a duplex mode prohibiting function of a copying machine having the switching member of FIG. 4 as a discrimination means. Components having the same reference numerals as those in the above-mentioned drawings have the same meaning as described above. Reference numeral 130 denotes an operation display unit such as a liquid crystal touch panel display provided in a place where the user of the copying machine can easily handle, and 420 denotes a conveyance roller that conveys the recording paper held on the paper feed tray 401 toward the image forming unit 3. This is a paper feed drive unit.
[0063]
First, the duplex mode is selected from the operation display unit 130 by a user input. The CPU 110 stores information on whether or not the recording paper held in advance in the paper feed unit can be used for image formation in the duplex mode by manual setting by the user of the switching member 410 that is a discriminating unit of the paper feed unit. . If double-sided mode image formation is possible, the CPU 110 outputs a control signal to each component unit, drives the paper feed drive unit 420 to direct the recording paper of the paper feed unit to the image forming unit 3. After the image forming unit 3 forms an image on the first surface, the reversing unit 65 reverses the recording sheet, and the image forming unit 3 again forms an image on the second surface. And control to discharge to an appropriate discharge tray 64a.
[0064]
On the other hand, when a recording sheet that cannot be used in the duplex mode is held in the sheet feeding unit, the CPU 110 determines that the recording sheet in the sheet feeding unit cannot be used when selecting the duplex mode. The feeding of recording paper from the copy is prohibited. At this time, the CPU 110 has a function of prohibiting means in the present invention. If it is determined that feeding of the recording paper from the paper feeding unit is prohibited, the operation display unit 130 displays that fact and notifies the user whether image formation is possible in the duplex mode. Alternatively, when recording paper having the same size and capable of image formation in the double-sided mode is held in another paper feeding unit, it may be changed to paper feeding from the other paper feeding unit. .
[0065]
FIG. 6 is a flowchart for determining whether or not the duplex mode of the copying machine having the switching member described with reference to FIGS.
[0066]
First, the user inputs image setting conditions from the operation display unit and makes settings (S11). The image forming conditions include the size of the recording paper to be used, the image density, the number of sheets, the presence / absence of selection of the duplex mode, and the like. When the condition setting is completed, the user presses an image formation start button (S12).
[0067]
Next, the CPU of the copying machine automatically determines whether or not a paper feeding unit automatic selection setting for selecting a paper feeding unit that holds a recording sheet that meets the setting condition S11 from among a plurality of paper feeding units. Confirm (S13). If the paper feed unit automatic selection setting is not made and the user designates a paper feed unit in the condition setting S11 (NO), the process proceeds to step S111. If the paper feed unit automatic selection setting has been made (YES), it is determined whether or not the duplex mode is selected in the condition setting S11 (S14). If the duplex mode is not selected (NO), the process proceeds to step S17.
[0068]
If the duplex mode is selected (YES), the switching member, which is a discriminating unit, acquires information on whether or not the recording sheet held by each sheet feeding unit can form an image in the duplex mode (S15). ), Out of a plurality of paper feeding units, a paper feeding unit capable of the duplex mode is selected (S16).
[0069]
Next, the recording paper size information set in the condition setting S11 is acquired (S17). Among the paper feeding units selected in step S16, a paper feeding unit that holds recording paper corresponding to the set recording paper size is selected (S18).
[0070]
Next, in step S19, if there is no corresponding sheet feeding unit (NO), it is determined that image formation cannot be performed under the set conditions, and the image forming impossibility is displayed on the operation display unit. The user is prompted to reset the conditions (S110).
[0071]
If there is a corresponding paper feed unit in step S19 (YES), it is then checked whether the paper feed unit holds a recording paper necessary for image formation (S111). If there is no recording paper (NO), a message requesting replenishment of recording paper is displayed on the operation display unit (S113). When the user completes the replenishment of recording paper to the paper feeding unit (S114), the process is repeated from step S111 again. If there is a recording sheet (YES), image formation is executed according to the set condition (S112).
[0072]
FIG. 7 is a diagram showing an aspect in which a detection unit that detects whether or not images can be formed on both sides of a recording material in the paper feeding unit of the copying machine as a determination unit.
[0073]
FIG. 7A is an overall cross-sectional view of a copying machine having a detecting unit in the paper feeding unit.
The same reference numerals in the figure as those described above represent the same components as described above. 52A and 53A, 52B and 53B, 52C and 53C are transport rollers of the first paper feed unit 4A, the second paper feed unit 4B, and the third paper feed unit 4C, respectively, and P is a recording paper. Reference numerals 43A, 43B, and 43C denote density sensors as detection means for the respective paper feeding units.
[0074]
FIG. 7B shows a partially enlarged view around the density sensor 43A of the first paper feed unit 4A. The uppermost sheet is picked up from a bundle of recording papers P stacked and stored in the paper feed unit, and is measured by a density sensor 43A disposed at an intermediate point between the transport rollers 52A and 53A immediately after the start of transport. The density of the second surface (back surface) of the recording paper P is detected. The density sensor 43A is not particularly limited as long as it can detect the density of the recording paper P, but is a photosensor having a light emitting element and a light receiving element. The density of the second surface of the recording paper P detected by the density sensor 43A is higher than a certain value by comparison with the density recognized as having a toner image (such as the back paper) or the density of the reference blank paper. In the case of density (special paper or the like), it is recognized that the recording paper should not be image-formed on the second side, and image formation in the duplex mode is prohibited. When the duplex mode is selected from the operation display unit, if it is determined that the recording paper of the paper feeding unit cannot form an image in the duplex mode, the rotation of the transport rollers 52A and 53A is stopped, and the image forming unit 3 Is not carried out (duplex mode is prohibited). If the duplex mode is prohibited, the fact is displayed on the operation display unit 130 to notify the user that the image cannot be formed in the duplex mode. Alternatively, when recording paper having the same size and capable of image formation in the double-sided mode is held in another paper feeding unit, it may be changed to paper feeding from the other paper feeding unit. .
[0075]
In the present embodiment, the density sensor 43A is disposed at an intermediate position between the transport rollers 52A and 53A. However, the density sensor 43A can be detected in a state in which the recording paper P is stored in the paper feeding unit before the transport of the recording paper P is started. Such a position may be used.
[0076]
In this embodiment, the density sensor is used as the detection unit. However, the present invention is not limited to this as long as it actually determines whether images can be formed on both sides.
[0077]
In the aspect in which the above-mentioned detection means is provided in the paper feed unit, the copying machine can automatically determine whether or not image formation is possible in the double-sided mode of the recording paper and prohibit it, so that the user does not have to set the type of recording paper. Thus, it is possible to efficiently prevent a problem that the recording paper held in the paper feeding unit is erroneously used in the duplex mode.
[0078]
FIG. 8 is a block diagram showing a duplex mode prohibiting function of a copying machine having the density sensor (detecting means) of FIG. 7 as a discrimination means. Components having the same reference numerals as those in the above-described drawings are synonymous with those described above. Reference numeral 43 denotes a density sensor as detection means for detecting whether or not the recording paper provided in the paper feeding unit can form an image in the duplex mode.
[0079]
When the duplex mode is selected from the operation display unit 130 by a user input, the CPU 110 selects an appropriate one of the sheet feeding units that hold the recording paper having a size corresponding to the set condition. Then, the density sensor 43 is operated to detect whether or not double-sided mode image formation is possible on the recording paper held in the paper feeding unit. At this time, if necessary, the paper feed drive unit 420 is driven to start feeding the recording paper from the paper feed unit, and the recording paper is moved to a position where the density sensor 43 can detect it. When the CPU 110 determines that the detection information from the density sensor 43 serving as the detection unit is capable of image formation in the duplex mode, the CPU 110 outputs a control signal to each component, The recording paper held by the paper feed unit is driven toward the image forming unit 3 by driving 420. In the image forming unit 3, after image formation is performed on the first surface of the conveyed recording paper, the reversing unit 65 reverses the front and back of the recording paper, and the image forming unit 3 again forms the second surface on the second surface. Control is performed so that the image is formed and discharged to an appropriate discharge tray 64a.
[0080]
On the other hand, if it is determined that a recording sheet that cannot be used in the duplex mode is held, the CPU 110 prohibits the feeding of the recording sheet from the sheet feeding unit. At this time, the CPU 110 has a function of prohibiting means in the present invention. When the double-side mode is prohibited, the fact is displayed on the operation display unit 130, and the user is notified of whether image formation is possible in the double-side mode. Alternatively, when recording paper having the same size and capable of image formation in the double-sided mode is held in another paper feeding unit, it may be changed to paper feeding from the other paper feeding unit. .
[0081]
FIG. 9 is a flowchart for determining whether or not the copying machine having the density sensor (detecting means) described in FIGS.
[0082]
In this flowchart, as the condition setting S11 described in the flowchart of FIG. 6, it is assumed that the duplex mode is selected (S21), and the case where the user designates and selects the specific sheet feeding unit is assumed. (Or assuming a copier having only one paper feed unit).
[0083]
First, the duplex mode is selected in the image formation condition setting by the user (S21). The user presses the start button to start image formation (S22).
[0084]
Next, the recording paper of the selected paper feeding unit determines whether or not double-sided mode image formation is possible, and the density of the second side is determined by a density sensor as a detecting means provided in the paper feeding unit. Detect (S23).
[0085]
If it is a backing paper or special paper and the duplex mode cannot be performed (NO), the mode is switched to the simplex mode and image formation is executed (S26). When the double-side mode is prohibited, the user may be prompted to reset the conditions by displaying the operation display section indicating that the double-side mode is disabled without switching the single-side mode.
[0086]
If image formation is possible on both sides (YES), image formation in the duplex mode is executed according to the set conditions (S25).
[0087]
FIG. 10 is a diagram illustrating an example of a setting screen of the operation display unit in a mode in which the determination by the determination unit is performed by input from the operation display unit of the copying machine.
[0088]
FIG. 10A is a basic screen of the operation display unit 130 configured by a liquid crystal touch panel display. Image formation from single-sided original (1) to double-sided (2) Copy mode selection (COPY MODE key), image density selection (COPY DENSITY key), magnification setting (LENS MODE key), recording paper size selection (PAPER) SIZE key) and the like are displayed.
[0089]
When the user presses the PAPER SIZE key 131, a lower layer screen as shown in FIG. 10B is displayed. This shows that the copier has two paper feed units that hold B4 size recording paper and four paper feed units that hold A4 size recording paper. Among the six keys in total, a recording paper that cannot form a double-sided image such as a back paper or special paper is held in the paper feeding unit indicated by the A4 size key 132 in the lower right, and the user can feed the paper. First, the A4 size key 132 is pressed once in order to set the recording paper of the copy to be prohibited from image formation in the duplex mode. Then, the pressed key is darkened as indicated by 132a in FIG. When the A4 size key 132a is pressed again, the display changes to “double-side prohibited” as indicated by 132b in FIG. When the A4 size key 132b displaying the double-side prohibition is pressed again, the double-side prohibition display disappears and the display returns to the display 132a in FIG.
[0090]
By the above method, the user sets in advance from the operation display unit 130 a sheet feeding unit that is prohibited from image formation in the duplex mode, and when the duplex mode is selected thereafter, the set feeding is set. It is possible not to feed the recording paper from the paper section to the transfer means, or to switch to single-side mode image formation.
[0091]
After the setting by the input from the operation display unit 130 is completed, the control is the same as that of the copying machine using the sheet feeding unit switching member described with reference to FIGS. To do.
[0092]
【The invention's effect】
For recording materials that do not change the enlargement ratio of the toner images on the front and back surfaces regardless of the type of recording material in duplex mode, do not require the user to perform manual work, and do not want to form images on both sides. Thus, it is possible to provide an image forming apparatus that prohibits image formation in the duplex mode and eliminates waste of the recording material.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a copying machine.
2 is a block diagram showing an example of an electrical configuration of a transport unit, a line sensor (measuring means), and a laser writing system in the copying machine of FIG. 1. FIG.
3 is a timing chart showing the operation timing of each component in the duplex mode of the copying machine of FIGS. 1 and 2 and in the measurement mode. FIG.
FIG. 4 is a diagram illustrating a mode in which a sheet feeding unit has a switching member as a determination unit of the copying machine of FIG. 1;
FIG. 5 is a block diagram showing a duplex mode prohibiting function of a copying machine having the switching member of FIG. 4 as discrimination means.
6 is a flowchart for determining whether or not a duplex mode of a copying machine having the switching member described with reference to FIGS.
7 is a diagram showing a mode in which a detection unit that detects whether or not images can be formed on both sides of a recording material in a paper feeding unit of the copying machine as a determination unit of the copying machine of FIG. 1;
8 is a block diagram showing a duplex mode prohibiting function of a copying machine having the density sensor (detecting means) of FIG. 7 as a determining means.
FIG. 9 is a flowchart for determining whether or not the duplex mode of the copying machine having the density sensor (detection unit) described in FIGS.
FIG. 10 is a diagram illustrating an example of a setting screen of the operation display unit in a mode in which the determination by the determination unit is performed by input from the operation display unit of the copying machine.
[Explanation of symbols]
1 Automatic document feeder
2 Image reader
3 Image forming section
4 Paper feeder
5 Transport path
6 Discharge / reversing section
31 Photosensitive drum
33 Laser writing system
43 Concentration sensor
52, 53 Conveying roller
56 Registration Roller
64a Output tray
65 Reverse part
66 Retransmission part
110 CPU
130 Operation display
131 PAPER SIZE key
132 A4 size key
220 Line sensor
401 Paper feed tray
410 Switching member

Claims (7)

A latent image is formed by imagewise exposure to a photoreceptor, and a toner image obtained by developing the latent image is transferred to the first surface of the recording material by a transfer unit, and fixed by a fixing unit. The recording material that has been turned upside down by the reversing means is conveyed again to the transfer area, and a new toner image formed on the photoreceptor is transferred to the second surface of the recording material by the transferring means, and the fixing means is used. In an image forming apparatus capable of image formation in a double-sided mode that is discharged to the outside after fixing,
Between the pre-drum transport roller provided at a position closest to the photoconductor on the upstream side in the transport direction of the recording material with respect to the photoconductor and a registration roller positioned on the upstream side of the pre-drum transport roller; Measuring means for measuring the vertical and horizontal dimensions of the recording material disposed at a position immediately before transferring the image to the recording material ;
The shrinkage rate by the fixing means of the recording material is calculated from the longitudinal dimension and the lateral dimension of the recording material measured by the measuring means before and after being fixed by the fixing means, and the magnification according to the shrinkage ratio is calculated. Control means for performing toner image formation on the photoreceptor,
In the duplex mode,
The first recording material is used for the calculation of the shrinkage rate without transferring the toner image by the transfer means ,
For the second and subsequent recording materials, a toner image transferred to the first surface is formed on the photoreceptor by normal image formation, and the toner image transferred to the second surface of the same recording material is the first image. Forming a toner image on the photoconductor with a magnification in accordance with the shrinkage calculated by the first recording material;
An image forming apparatus having a measurement mode in which the first recording material and the second and subsequent recording materials are distinguished and discharged to the outside of the apparatus.   2. A plurality of discharge trays, wherein the first recording material is discharged to a first discharge tray, and the second and subsequent recording materials are discharged to a second discharge tray. The image forming apparatus according to 1.   3. A total counter for counting and displaying the number of recording materials discharged outside the apparatus, wherein the first recording material is not included in the count of the total counter. The image forming apparatus described.   The image forming apparatus according to claim 1, wherein the measuring unit that measures the lateral dimension of the recording material is a CCD or a CIS. Said measuring means for measuring the vertical dimension of the recording material, the image forming according to claim 1, characterized by measuring the vertical dimension by measuring the transit time of said recording medium apparatus. The exposure for forming a latent image on the photoconductor is performed by scanning and exposing the photoconductor in the horizontal direction with a laser beam while moving the photoconductor in the vertical direction. The combined toner image is formed by changing a vertical dimension magnification by changing a moving speed of the photoconductor, and changing a horizontal dimension magnification by changing the scanning exposure speed. The image forming apparatus according to any one of 1 to 5. 7. The measurement device according to claim 1, wherein the measurement unit also serves as a recording paper misalignment detection unit, and forms a toner image on the photoconductor in accordance with the misalignment of the recording paper detected by the misalignment detection unit. The image forming apparatus according to claim 1.

Images