JP2004090284A - Image forming apparatus with automatic margin adjustment function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To align an image formed on an image carrier, e.g. a photosensitive drum, accurately with a position in the main scanning direction of a recording material. <P>SOLUTION: The image forming apparatus 100 comprises a corona charger and an image processing section movable to an optional position in the main scanning direction of an image, a secondary transfer section 5b for transferring an image formed at a photosensitive drum 1 and an intermediate transfer belt 5 to a recording material P, a roller 91 for carrying the recording material to the secondary transfer section, a sensor 101 disposed near the secondary transfer section in order to detect the end part in the main scanning direction of a recording material being carried by the roller, a section for operating the average value of the end part position of a plurality of consecutive recording materials detected by means of the sensor, and a section for controlling the corona charger and the image processing section to adjust the image writing position in the main scanning direction for subsequent recording materials in accordance with the average end part position of the recording material calculated at the end part average value operating section. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus for forming an image on a recording material, and in particular, an image on an image carrier is recorded by a transfer unit from a position where the image is written on an image carrier for carrying an image to be transferred to the recording material. The present invention relates to an image forming apparatus capable of accurately changing an image writing position of an image carrier in accordance with a position of a recording material even if a distance to a transfer position at which the image is transferred to a material is long.
[0002]
[Prior art]
The image forming apparatus includes a copying machine, a facsimile, a printer, and a multifunction peripheral. In the conventional image forming apparatus, the position of the recording material and the image writing position in the main scanning direction of the image are aligned as follows.
[0003]
Generally, first, when an image is formed on the first surface of a recording material, whether the storage portion (cassette) of the recording material is aligned with the image forming portion in the main scanning direction (horizontal registration correction) Alternatively, the image writing start position is adjusted (fixed value is input).
[0004]
When an image is formed on the second side of the recording material alone or on the first and second surfaces, the recording material on which the image has been formed on the first surface is temporarily stored in a tray before the image is formed on the second surface. In a tray-type double-sided paper feeding type image forming apparatus which is aligned in the tray and conveyed again to form a second image, the tray is aligned with the image forming unit in the same manner as a cassette. Then, the position of the recording material and the position of the image are adjusted after the accuracy at the time of alignment is further increased.
[0005]
Further, particularly, image alignment at the time of double-sided copying, which is often performed in a digital image forming apparatus, is often performed based on the end surface (paper edge) of a recording material. Unlike the image forming apparatus using the above-described tray, the image forming apparatus is configured to form an image on both sides without using a tray, so that it is not necessary to temporarily store a recording material in the tray, Excellent productivity. Then, the image forming apparatus forms an image on the first side of the recording material, and then forms an image on the second side by using a flag-type sensor or the like during conveyance of the recording material (double-sided conveyance). The edge of the recording material is detected, and a position for forming an image on the second surface of the recording material (image writing position in the main scanning direction) is corrected based on the information on the edge position. This correction is performed by using the characteristic that the position of the image in the main scanning direction (writing start position) can be easily changed in the digital image forming apparatus.
[0006]
[Problems to be solved by the invention]
The problem in the image formation on the first side will be described. The recording material conveyed to form an image on the first side is positioned at the position of the recording material in the cassette by taking the cassette in and out, even if horizontal registration adjustment or image position adjustment has been performed according to the cassette. The position may be shifted according to a shift, a shift of a replenishing position at the time of replenishment of the recording material, or a position shift of a position in the transport direction of the recording material which changes depending on a state of the recording material.
[0007]
If such a positional shift or change occurs, the position of the recording material shifts with respect to the image forming position, and as a result, an image defect such as loss of a blank space occurs. In addition, when the recording material has no blank space, the image is transferred to a portion other than the recording material, and the device may become dirty, or the dirt may stain the next recording material.
[0008]
The problem in the image formation on the second side will be described. In the case of a tray-type image forming apparatus having a double-sided conveyance configuration, when a recording material is once stored in a tray and aligned, and then sheet feeding is started again, a conveyance defect such as a pickup defect may occur. Further, in this image forming apparatus, since the recording material on which an image is formed on only one surface is collectively conveyed toward double-sided image formation, productivity may be significantly reduced depending on a document or an operation mode. .
[0009]
A description will be given of a problem of alignment between a recording material and an image performed on the basis of an end surface (paper end) of the recording material in a digital image forming apparatus. Since the image writing start position is determined after the paper edge position detection, there is an operational restriction that the paper edge detection operation must be performed before the image writing start.
[0010]
In addition, there are conventionally image forming apparatuses having a large-diameter photosensitive drum, and image forming apparatuses having an intermediate transfer belt which have been frequently seen in recent years. In this type of image forming apparatus, the distance from the position where the image is written on the photosensitive drum or the intermediate transfer belt to the transfer position where the image is transferred onto the recording material is much longer than that of a normal image forming apparatus.
[0011]
For this reason, in the image forming apparatus having a long distance from the writing position to the transfer position, it is necessary to perform the paper edge detection operation on the upstream side from the image transfer unit because of the long distance. Skewed and skewed, the deviation of the paper end position is increased. As a result, there is a problem that the paper edge detection position and the paper edge position in the image transfer unit are largely deviated.
[0012]
In some image forming apparatuses, a sheet is conveyed or an image is formed on a recording material of any size with one end of the recording material as a reference position. In the image forming apparatus of the one-side reference conveyance, the recording material is conveyed by a skew feeding roller toward an abutting surface common to all sizes, which hits an edge of the paper. For this reason, the image forming apparatus of this type is characterized in that the end of the recording material is always conveyed at a fixed position, so that the position of the image end and the end of the recording material can be easily adjusted.
[0013]
However, in the image forming apparatus of the one-side reference conveyance, the position of the roller in contact with (holding) the recording material in the main scanning direction differs depending on the paper size as compared with the normal (center) reference conveyance of the recording material. Differently, there may be a difference in the conveying force between the back side and the near side of the recording material.
[0014]
Further, in order to accurately assure the position of the end of the recording material, it is necessary to provide an abutting surface on one side (reference side) of the recording material conveyance path. In many cases, when the recording material is abutted against the abutting surface, the position of the roller in contact with (holding) the recording material in the main scanning direction differs depending on the paper size. Variations occur for each material size.
[0015]
For this reason, the image forming apparatus of the one-sided reference conveyance has a problem that a conveyance failure such as a skew of the recording material is likely to occur. In addition, although the operation of assuring the end position of the recording material by abutting the recording material against the abutting surface can be performed relatively easily, the recording material abuts against the abutting surface. There is also a problem that the material rubs against the abutting surface, and the essential paper conveyance ability and the conveyance accuracy are reduced.
[0016]
Further, before the image transfer position, the side end and the front end of the image forming range are read by the image reading sensor, and the end and the front end of the recording material conveyed toward the transfer unit in accordance with the read image position. An image forming apparatus or a recording material transporting apparatus that adjusts the position of the recording medium has been partially put to practical use. Since the image forming apparatus or the recording material transporting device always corrects the recording material position in accordance with the image position, the position of the image and the recording material can be adjusted with extremely high accuracy.
[0017]
However, in this type of image forming apparatus or recording material transporting device, the sensor for reading the image position is expensive, and the configuration for controlling the position of the recording material after reading is increased in size corresponding to the transport length. However, there is a problem that the cost is greatly increased due to the complicated configuration.
[0018]
Further, it is necessary to read the image position by the distance required for correcting the position of the recording material upstream of the image transfer unit, and the image position after reading may be shifted by the distance.
[0019]
In other words, reading the image position on the photosensitive drum and the transfer belt near the image transfer unit is the most preferable because the positioning accuracy is high.
[0020]
ADVANTAGE OF THE INVENTION This invention can match the position of the image formed on the image carrier, such as a transfer belt and a photosensitive drum, and the recording material with high precision in the main scanning direction with an inexpensive structure and a highly versatile method. It is an object to provide an image forming apparatus.
[0021]
[Means for Solving the Problems]
In order to achieve the above object, an image forming apparatus according to the present invention includes an image writing unit that can arbitrarily move a position of an image in a main scanning direction, and an image that includes the image writing unit and forms an image on a recording material. Forming means, image transferring means for transferring an image formed by the image forming means to the recording material, conveying means for conveying the recording material to the image transferring means, and disposed near the image transferring means End detecting means for detecting an end of the recording material conveyed by the conveying means in the main scanning direction, and end positions of a plurality of continuous recording materials detected by the end detecting means Edge average value calculation means for calculating the average value of the image, and an image in the main scanning direction with respect to the subsequent recording material in accordance with the average edge position of the recording material calculated by the edge average value calculation means. Set the writing position It includes an image position adjustment control means for adjusting and controlling the writing means.
[0022]
The image forming apparatus of the present invention includes a reversing conveyance unit that conveys a recording material on which an image is recorded by the image transfer unit and the recording material is turned upside down to the image transfer unit, and the edge detection unit is turned upside down. The end portion of the recording material is detected in the main scanning direction, and the end portion average value calculating means is configured to calculate an average of the end positions of the plurality of continuous recording materials which are reversed by the end portion detecting means. The image position adjustment control unit calculates a value for the subsequent front-back reversed recording material according to the average end position of the reversed front-back recording material calculated by the end average value calculating unit. On the other hand, the position of the image in the main scanning direction is moved by controlling the image writing means.
[0023]
The image forming apparatus of the present invention includes a reversing conveyance unit that conveys a recording material on which an image has been recorded by the image transfer unit and has been turned over to the image transfer unit, and the reversal conveyance unit includes A skew conveyance section for skew conveyance of the recording material, and a guide section for receiving and guiding a side portion of the recording material, which is conveyed by the skew conveyance section and turned upside down, and the guide section includes the guide section, The recording material can be moved in a direction intersecting the transport direction of the recording material according to the size of the recording material.
[0024]
The image forming apparatus according to the present invention includes a storage unit that stores a final average value of the end position of the recording material calculated by the end average value calculation unit, and the image position adjustment control unit restarts the apparatus. The position of the image with respect to the first recording material in the main scanning direction at the time is controlled based on the final average value stored in the storage means.
[0025]
The image forming apparatus according to the present invention includes a plurality of loading units disposed on the upstream side of the transporting unit and on which the recording material is loaded, wherein the recording material calculated by the edge average value calculating unit is provided. A storage unit for storing a final average value of an end position for each of the loading units, wherein the image position adjustment control unit stores the first recording material on which an image is to be formed when the apparatus is restarted. The image writing means is controlled based on the corresponding final average value stored in the storage means.
[0026]
The image forming apparatus according to the present invention includes a plurality of loading units disposed on the upstream side of the transporting unit and on which the recording material is loaded, wherein the recording material calculated by the edge average value calculating unit is provided. Storage means for storing the final average value of the end position for each recording material of the loading means, wherein the image position adjustment control means, when the loading means is switched, corresponding to the switched loading means, The image writing means is controlled based on the final average value stored in the storage means.
[0027]
In the image forming apparatus according to the present invention, the edge average value calculating unit excludes a value of an edge position equal to or more than a predetermined value from the calculation of the average value.
[0028]
In the image forming apparatus according to the aspect of the invention, the transport unit transports the recording material with reference to a center.
[0029]
In the image forming apparatus according to the aspect of the invention, the end detection unit is disposed between the conveyance unit and the image transfer unit.
[0030]
In the image forming apparatus of the present invention, the edge detecting means is a fixed line sensor disposed in a region corresponding to a range corresponding to an edge of the entire size of the recording material.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.
[0032]
(Image Forming Apparatus of First Embodiment)
FIG. 1 is a schematic main sectional view of a copying machine which is a full-color image forming apparatus according to a first embodiment of the present invention.
[0033]
A full-color image forming apparatus 100 shown in FIG. 1 is a copying machine including a digital color image reader unit A and toner storage units 4y, 4m, 4c, and 4Bk at an upper part, and a digital color image printer unit B at a lower part. .
[0034]
The reader unit A exposes and scans a document D placed on a platen glass 31 by a user with an exposure lamp 32, condenses a reflected light image from the document D on a full-color CCD sensor 34 by a lens 33, and outputs a color image. A decomposed image signal is obtained. The color-separated image signal is subjected to image processing by a video processing unit (not shown) through an amplification circuit (not shown), and is sent to a printer unit B via an image memory (not shown).
[0035]
The printer unit B is divided into image forming units (image forming stations) of yellow (y), magenta (m), cyan (c), and black (Bk) from the right in FIG. . The four photosensitive drums 1y, 1m, 1c, 1Bk for each station, which are image carriers, are rotatably supported in the direction of the arrow in the figure. Around the photosensitive drum, a pre-exposure lamp (not shown), corona chargers 2y, 2m, 2c, 2Bk, laser exposure optical systems (scanner units) 3y, 3m, 3c, 3Bk, and potential sensors (not shown) Each of the developing units 24y, 24m, 24c, and 24Bk, a not-shown on-drum light amount detection unit, a not-shown transfer device, and cleaning units 6y, 6m, 6c, and 6Bk are arranged.
[0036]
In the laser exposure optical system, an image signal from the reader unit A is subjected to image processing by an image processing unit (not shown) in FIG. 1, and is converted into an optical signal of each color (for each station) by a laser output unit (not shown). The laser light converted into an optical signal is reflected by a polygon mirror, projected through a lens and a return mirror onto the surface of each photosensitive drum.
[0037]
At the time of image formation in the printer section B, the photosensitive drum is rotated in the direction of the arrow, the photosensitive drum after having been neutralized by the pre-exposure lamp is uniformly charged by a charger, and a light image E is irradiated for each separation color, and a latent image is formed. To form
[0038]
Next, the developing device develops the latent image on the photosensitive drum, and forms a toner image based on a resin and a pigment on the photosensitive drum. The toner in the developing unit is supplied from the toner storage units (hoppers) 4y, 4m, 4c, and 4Bk of the respective colors arranged on the right side of the leader unit A so as to keep the toner ratio (or toner amount) in the developing unit constant. It will be replenished at any time.
[0039]
The toner image formed on the photosensitive drum is transferred to the intermediate transfer belt 5 at the transfer section of each station, and the toner images formed on the photosensitive drum at each station on the intermediate transfer belt are superimposed on all four colors.
[0040]
The image processing unit 115, the photosensitive drums 1y, 1m, 1c, and 1Bk, the corona chargers 2y, 2m, 2c, and 2Bk, the laser exposure optical systems (scanner units) 3y, 3m, 3c, and 3Bk, and the intermediate transfer belt 5 include: 5 is an example of an image forming unit.
[0041]
The intermediate transfer belt 5 is circulated by a driving roller 5a. At a position facing the drive roller 5a, a sensor 50 for detecting a position shift and a density of an image for each station is disposed. With this sensor 50, it is possible to perform control to feed back image density, toner supply amount, image writing timing, image writing start position, and the like to each image forming unit as needed.
[0042]
On the other hand, the recording material P is selectively sent out one by one from each of the storage sections 71, 72, 73 by the respective sheet feeding means 81, 82, 83. The skew of the recording material is corrected by, for example, a registration roller 91 that is a conveying unit. Then, the recording material is conveyed to, for example, a secondary transfer unit 5b, which is an image transfer unit that transfers the toner image on the intermediate transfer belt 5 at a desired timing.
[0043]
In the secondary transfer section 5b, the toner image is transferred onto the recording material. The recording material passes through the conveying units 60 and 61, and the toner image is fixed by the heat roller fixing device 9, and is discharged to the discharge tray 10. On the other hand, the intermediate transfer belt after the secondary transfer is cleaned of the transfer residual toner by the transfer cleaner unit 14 and circulates again to the primary transfer process of each image forming unit (each station).
[0044]
When images are formed on both sides of the recording material, the conveyance path switching guide 19 switches immediately after the recording material passes through the fixing device 9. The recording material is guided by the transport path switching guide 19, passes through the transport vertical path 21a, and is once guided to the reversing path 21b. Then, the sheet is retreated in the direction opposite to the direction in which the sheet is sent, and is sent to the double-sided conveying path 21c. That is, the recording material is transported by switchback.
[0045]
Thereafter, the recording material passes through the two-sided conveying rollers 52, 53, and 54, the skew correction and timing are performed by the two-sided conveying roller 55, and is conveyed to the registration roller 91 at a desired timing. The image is transferred to the other surface by the image forming process.
[0046]
One of the features of the full-color image forming apparatus 100 is that the distance from the first image writing section to the image transfer section is very long.
[0047]
That is, the image forming apparatus 100 includes four photosensitive drums 1y, 1m, 1c, and 1Bk. Writing of an image starts from the first photosensitive drum 1Bk. Therefore, when the peripheral speed of the photosensitive drum, the circulation speed of the intermediate transfer belt 5, and the transport speed of the recording material are the same, the image forming apparatus 100 performs the intermediate transfer of the toner image from the exposure position F of the photosensitive drum 1Bk. The toner image is transferred onto the recording material being conveyed upstream of the secondary transfer unit 5b by a distance equal to the distance (L1) from the position where the image is transferred to the belt 5 to the secondary transfer unit 5b. Will be transcribed.
[0048]
Therefore, in order to adjust the position of the image in accordance with the position of the recording material, for example, an edge detection unit, which will be described later, is located at a distance L1 upstream from the secondary transfer portion 5b. A detection sensor 101 must be provided to detect the position of the recording material. However, even if the position of the recording material is detected at the position of the distance L1, the position often shifts while the recording material is conveyed by the distance L1. Therefore, even if the position of the recording material is detected at the position of the distance L1, it becomes meaningless.
[0049]
Therefore, in the image forming apparatus of the present embodiment, the recording material end detection sensor 101 is disposed near the upstream side of the secondary transfer portion 5b, and detects the displacement of, for example, three recording materials and averages the displacement. The position at which the photosensitive drum is exposed is adjusted based on the calculated value, and the average value is used as the estimated positional deviation amount of the recording material to be sent thereafter. Therefore, in the image forming apparatus of the present embodiment, the position can be accurately adjusted even when the distance L1 is long.
[0050]
In the case where one photosensitive drum is an image forming apparatus, a recording material end detection sensor is provided at a position corresponding to a distance (L2) from an exposure position of the photosensitive drum to an image being transferred onto the recording material. Then, the position of the recording material is detected, and the position at which the photosensitive drum is exposed is adjusted. The distance L2 is a distance (L3) corresponding to the distance (L3) from the exposure position F to the transfer position G of the photosensitive drum to the intermediate transfer belt 5 in the image forming apparatus according to the present embodiment, and thus is far greater than the distance L1. The distance is short. For this reason, in the image forming apparatus having one photosensitive drum, the distance between the time when the recording material is detected by the recording material end detection sensor and the time when the toner image is transferred by the photosensitive drum is short. The position of the image can be adjusted by using the detected value as it is, without causing any positional deviation.
[0051]
However, if the distance L2 is long even when the number of photosensitive drums is one, the distance between the time when the recording material is detected by the recording material edge detection sensor and the time when the toner image is transferred by the photosensitive drum is not long. The recording material may be misaligned. Such a problem can be dealt with by calculating the average value of the positional deviation as described above. A specific example is a full-color image forming apparatus according to a second embodiment described later.
[0052]
Hereinafter, a control method and a configuration of the full-color image forming apparatus 100 according to the present embodiment in which an average value of the above-described positional shifts is obtained and the positions of the recording material and the image on the photosensitive drum are adjusted will be described.
[0053]
In the full-color image forming apparatus 100 of the present embodiment, the position of the recording material and the image on the photosensitive drum are adjusted with reference to the performance of a normal double-sided printing machine and the like, and from various printed materials and the level of user claims. The goal is to make the accuracy within about ± 0.75 mm, which is less than half the value of the conventional image forming apparatus.
[0054]
First, a recording material edge detection sensor 101 for detecting the edge of the recording material upstream of the secondary transfer portion 5b is disposed below the registration roller 91 in FIG. As shown in FIG. 2, the recording material edge detection sensor 101 uses a CCD line sensor extending in the main scanning direction.
[0055]
The length of the recording material end detection sensor 101 is such that the full-color image forming apparatus 100 of the present embodiment can detect all the recording materials having a width of 100 mm to 330 mm which can form an image. An object of about 210 mm is used. The recording material end detection sensor 101 is a popular line sensor generally used for a reading section of a small facsimile compatible with A4, and has a resolution of about 200 dpi (0.12 mm). And it is a low price and widespread product. That is, a special sensor is not used for the recording material end detection sensor 101. In addition, the line sensor originally has an image reading ability, and has a performance enough to satisfy the ability to read the end of the recording material.
[0056]
Next, the operation and control of aligning the image start position with the edge of the recording material using the recording material edge detection sensor 101 will be described mainly with reference to the configuration of the image forming apparatus shown in FIG. A description will be given based on the recording material end detection sensor 101, the flowchart in FIG. 3, and the control block diagram in FIG.
[0057]
First, after the operation mode is determined by the user, the image forming apparatus 100 starts a copying operation (S301). The recording material edge detection sensor 101 first detects the position of the edge (paper edge position) of the first three recording materials in the transport direction (S302). Next, an average value of the three detection data obtained by the recording material edge detection sensor 101 is obtained by, for example, an edge average value calculation unit 111 that is edge average value calculation means (S303). The calculation at this time is preferably averaging or a method of estimating a subsequent value from a change in the numerical values of the first, second, and third sheets. However, in this embodiment, the averaging is simply performed.
[0058]
This average value is used as the predicted positional deviation amount of the fourth and subsequent recording materials (S304), and is recognized (S305), and the writing position of the image of the fourth and subsequent recording materials is determined, and the current writing is performed. The operation for changing the position is started (S306).
[0059]
On the other hand, the reader unit A exposes and scans the original D placed on the original platen glass 31 by the user with the exposure lamp 32, and condenses the reflected light image from the original D on the full color CCD sensor 34 by the lens 33. A color separation image signal is obtained. This color separation image signal is input to the image processing unit 115. The color separation image signal may be sent from an external network 116. For example, the control unit 112, which is an image position adjustment control unit, inputs a signal of the predicted shift amount to the image processing unit 115. The corona chargers 2y, 2m, 2c, and 2Bk, the laser exposure optical systems (scanner units) 3y, 3m, 3c, and 3Bk, and the image processing unit 115 are examples of an image writing unit.
[0060]
The image processing unit 115 controls the full-color CCD sensor 34 to adjust the position where the light image E by the laser exposure optical systems 3y, 3m, 3c, 3Bk exposes the photosensitive drums 1y, 1m, 1c, 1Bk. Adjust the image forming position in the scanning direction. The photosensitive drum is exposed by adjusting the image forming position in the main scanning direction.
[0061]
Further, when an image is formed on a recording material, the edge average value calculation unit 111 calculates the average value of the positional deviations of the three recording materials again, and according to the calculated value, the control unit 112 determines the writing position. To change. This operation is repeated until the recording material runs out.
[0062]
The position adjustment in the sub-scanning direction is performed by controlling the timing at which the registration roller 91 starts feeding the recording material.
[0063]
Next, main phenomena of positional deviation of the recording material, causes of the positional deviation, and how to detect the positional deviation will be described.
[0064]
The image forming apparatus 100 according to the present embodiment predicts the end position of the succeeding recording material from the end position along the transport direction of the preceding recording material, and determines the image position of the succeeding recording material. The reason why the edge position of the recording material and the image position can be relatively accurately adjusted will be described.
[0065]
FIGS. 4A, 5A, 6A, and 7A are graphs showing changes in the margin amount of the recording material when the image writing position is fixed. FIGS. 4B, 5B, 5C, 6B, and 7B show the loading (cross-sectional) state of the recording material in the cassette corresponding to each graph. FIG.
[0066]
The state of the recording material in the image forming apparatus is mainly divided into four states shown in FIGS. 4B, 5B, 5C, 6B, and 7B. . Therefore, the change of the margin amount is divided into four, that is, FIG. 4 (a), FIG. 5 (a), FIG. 6 (a) and FIG. 7 (a). Further, the value of the margin amount shown here is a value that can be directly replaced with the variation amount of the end position of the recording material because the image writing position is fixed.
[0067]
The graph in FIG. 4A shows a change in the value during normal continuous paper feeding. As can be seen from the graph of FIG. 4A, the fluctuation of the end position of the recording material during normal continuous conveyance is very small, and may be about 0.5 mm or less even when the recording material is suddenly shifted. I understand. In other words, the end positions of the first few recording materials are accurately detected, and the control of the detection and the writing position adjustment is continued during the operation, so that the subsequent end positions of the recording materials are relatively controlled. It can be seen that the prediction can be made with high accuracy and the position of the image can be matched with the position of the recording material.
[0068]
Next, as shown in FIGS. 5 (b) and 5 (c), the graph of FIG. 5 (a) shows that the number of sheets of the recording material is small due to the spring pressure of the spring for pressing the recording material in the cassette. Then, the recording material is pressed to the back side, and when the number of sheets is large, the pressing force is insufficient and the margin changes due to the supply from the near side.
[0069]
Also in this case, since the amount of change in the position of the edge of the recording material gradually changes, the control for detecting the edge of the recording material and adjusting the image writing position near the image transfer portion as needed during operation. It can be understood that by performing the above, it is possible to easily adjust the end position of the image to the end position of the recording material.
[0070]
Finally, the graphs of FIGS. 6A and 7A show the margins generated when the user adds a recording material in the middle, as shown in FIGS. 6B and 7B. Changes.
[0071]
As shown in FIG. 6B, the graph of FIG. 6A shows only two recording materials at the boundary between the lower recording material and the upper recording material when the recording materials are added. , The change in margin caused by the displacement.
[0072]
As shown in FIG. 7 (b), the graph of FIG. 7 (a) shows the frictional state of the contact surface between the lower recording material and the upper recording material when the recording material is added. This indicates a change in blank space caused by a shift of the recording material added later due to a difference or the like.
[0073]
In order to cope with the change of the margin as shown in the graphs of FIGS. 6A and 7A, a method of handling the data of the detected end position of the recording material is determined in advance.
[0074]
This will be described in detail below.
[0075]
As shown in the graph of FIG. 6A, when the detected values of the edge positions of the recording material are significantly different from each other by one or two or more than the specified value, the average edge value calculation in the control block diagram shown in FIG. When calculating the average value of the recording material end positions, the unit 111 does not use a value that is significantly different from the above-described specified value. In this embodiment, the specified value is set to about 0.6 mm, but this value can be freely changed and set.
[0076]
That is, in the control block diagram shown in FIG. 8, a specified value (for example, 0.6 mm) is stored in the end position abnormal value detecting unit 113 in advance. Then, the end position value of the recording material detected by the recording material end detection sensor 101 is sequentially compared with a specified value by the end position abnormal value detection unit 113. When the value of a certain end position exceeds a specified value, the end position abnormal value detection unit 113 notifies the end average value calculation unit 111 to cut the value. As a result, the edge average value calculation unit 111 calculates the average value of the edge positions without using the value of the edge position exceeding the specified value, and then accurately calculates the prediction of the edge position thereafter. be able to. The specified value stored in the end position abnormal value detection unit 113 in advance can be changed.
[0077]
As shown in the graph of FIG. 7A, when the detected value of the edge position of the recording material continuously changes from the original state, the edge average value calculation unit in the control block diagram shown in FIG. Numeral 111 recalculates the position of the recording material end, and the control unit 112 moves the image writing position for the succeeding recording material in accordance with the recalculated value.
[0078]
That is, in the control block diagram shown in FIG. 8, a specified value (for example, 0.6 mm) is stored in the end position abnormal value detecting unit 113 in advance. Then, the end position value of the recording material detected by the recording material end detection sensor 101 is sequentially compared with a specified value by the end position abnormal value detection unit 113. When the value of a certain end position exceeds a specified value, the end position abnormal value detection unit 113 notifies the end average value calculation unit 111 to cut the value. The end-average-value calculating unit 111 determines that the loaded state of the recording materials in the cassette has changed as a whole when three consecutive cuts are received, and deletes the three values. Do not calculate the average value. Then, the control unit 112 adjusts an image writing position (an exposure position) via the image processing unit 115 based on the average value.
[0079]
By the way, when the average value is calculated as described above, when two end portions are largely displaced as shown in FIG. 6A, the two end images are not used as the adjustment data of the image position. Only the margin (image position and recording material position) is shifted, but the control unit 112 can adjust the image position and the recording material position with respect to the subsequent recording material.
[0080]
Also, as shown in FIG. 7A, when the shift amount of the end position greatly changes, the value is reflected in the adjustment of the image writing position at the time of the third sheet (P) when the end position starts to shift. The margins (the position of the image and the position of the recording material) of the first three sheets + α are shifted, but thereafter, both positions are controlled by the edge average value calculation unit 111 so as to match again. .
[0081]
The edge average value calculation unit 111 performs these two calculation methods, so that sudden displacement of the recording material does not affect image position control for the succeeding recording material. ing. That is, the image forming apparatus according to the present embodiment can perform the alignment control between the image and the recording material by minimizing the state in which the image position and the recording material position are shifted from each other in the main scanning direction. I can do it.
[0082]
Apart from these factors, the displacement of the end of the recording material is caused by a slight displacement of the cassette caused by inserting and removing the cassette when replenishing the recording material. This may occur, for example, when the cassette is emptied during conveyance and an automatic cassette change for conveying the recording material from another cassette or a multi-tray for storing recording materials of the same size is performed.
[0083]
The image forming apparatus according to the present embodiment performs so-called normal control for newly detecting the end position from the first three sheets at the time of inserting and removing the cassette. , 73 and the end position for each size of the recording material in the multi-tray 71 are stored for each cassette, for example, an average value storage unit 114 for each cassette. That is, the average value for each cassette is stored in the average value storage unit 114 for each cassette as needed, and the control unit 112 adjusts the image position based on the stored value when the cassette is inserted or removed.
[0084]
That is, when the automatic cassette change is performed, the image writing position can be moved by the control unit 112 applying the average value stored in the average value storage unit 114 for each cassette as data for each cassette.
[0085]
Further, data of the image writing position for each cassette at the end of the operation (average value for each cassette) is stored in the average value storage unit 114 for each cassette, and when the operation is started again, the value stored for each cassette is stored. By applying this method, the probability that the image position from the first recording material and the position of the recording material in the main scanning direction can be accurately adjusted from any cassette can be further increased.
[0086]
Further, the image forming apparatus of the present embodiment stores the data of the image writing position of the cassette which is always used at the end of the operation of the image forming apparatus in the storage means, for example, the average value storage section 117, and operates again. When starting the recording, the probability that the image position and the position of the recording material in the main scanning direction are accurately adjusted from the first recording material can be further increased by applying the stored value. I have.
[0087]
To summarize the above, in an image forming apparatus in which the distance from the image writing to the image transfer unit is long, the position of the recording material in the cassette, which could not be conventionally handled, or which was very expensive even if it was handled, The line sensor mainly detects the edge of the recording material, because the image position can be automatically adjusted according to the position of the recording material that is deviated due to the fluctuation of the recording material, insertion / removal of the cassette, replacement of the cassette, etc. This can be achieved with an inexpensive configuration by adding one 101.
[0088]
Next, a configuration in which the position of the image and the position of the end of the recording material at the time of double-sided copying are matched will be described.
[0089]
Among the causes of the deviation of the end position of the recording material at the time of double-sided copying, most of the deviations are caused when the recording material is transported while being inverted.
[0090]
That is, in FIG. 1, the displacement of the recording material at the time of double-sided copying occurs when the recording material is switchback-conveyed in the direction of the double-sided conveyance path 21c from the conveyance vertical path 21a to the reversal path 21b by the reversing roller 51. When slippage occurs in the reversing roller 51, when there is a difference between pure conveying forces (conveying force in the width direction of the recording material) between the back side and the near side by the reversing roller 51, the conveying force is changed due to a difference in density of the toner image. It occurs when there is a difference.
[0091]
This shift is different from the case where the recording material is initially supplied from the cassette, and the direction and the amount of displacement of the recording material are not stable. It is very difficult to calculate and predict the position.
[0092]
Therefore, in the image forming apparatus 100 of the present embodiment, the recording material is temporarily moved to one side in the main scanning direction shown in FIG. The recording material receiving plate 102, whose position can be adjusted for each size of the recording material, is abutted by two-sided conveying rollers 53, 54, and 55 which are oblique feed rollers. This makes it possible to align the positions of the ends of the recording material conveyed toward the second-side transfer, so that the recording material is at the same position as when supplied from the cassette or more than when supplied from the cassette. The paper is conveyed to the secondary transfer portion 5b with its edges aligned. For example, the recording material receiving plate 102 which is a guide portion and the double-sided transport rollers 53, 54 and 55 which are skew transport portions are examples of reversing transport means.
[0093]
Therefore, the image forming apparatus 100 detects the edge of the recording material by the same recording material edge detection sensor 101 that has detected the position of the recording material on the first surface, and performs recording on the subsequent second surface. By setting a dedicated image writing position for the material, the image position on the second surface and the end position of the recording material can be accurately matched.
[0094]
In other words, even if the image forming apparatus 100 uses the same recording material edge detection sensor 101 as the sensor for detecting the recording material on the first surface and the recording material on the second surface, the image forming apparatus 100 does not move in the main scanning direction during the duplex conveyance path. With the receiving plate 102 for receiving the recording material from above, the image position of the first and second surfaces can be aligned with the recording material position only by correcting the deviation of the recording material in the main scanning direction at the time of reversal. It is.
[0095]
The position of the receiving plate 102 can be easily adjusted for each size by a small stepping motor. Therefore, the cost of the image forming apparatus is hardly increased.
[0096]
In the image forming apparatus of the present embodiment, since the recording material is conveyed by the double-sided conveyance rollers 53, 54, and 55 on the basis of the center, not only the conveyance of the recording material but also the oblique feeding is performed. Is stable, and the oblique conveyance is performed on the double-sided conveyance path, so that even if a conveyance delay occurs, it can be sufficiently corrected before the registration rollers 91, so that the conveyance capacity is almost completely reduced. It has almost no problem.
[0097]
Therefore, the image forming apparatus according to the present embodiment accurately controls the alignment of the image on one side and both sides of the recording material and the recording material with an inexpensive configuration in which only the line sensor 101 and the receiving plate 102 are added. It can be performed in a wide area.
[0098]
Further, the present embodiment has a feature that the image position and the recording material position cannot be aligned only at the very beginning of the operation. In this regard, a device for an adjustment mode (trial mode) for positioning is used. By setting to, the position of the final output material can be almost matched.
[0099]
(2nd Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG.
[0100]
FIG. 10 is a schematic sectional view of a full-color image forming apparatus 200 according to the second embodiment. The copying machine, which is the image forming apparatus 200 of the second embodiment, also includes a digital color image reader unit A at the top and a digital color image printer unit B at the bottom.
[0101]
The reader unit A exposes and scans the original D placed on the original platen glass 231 by the user with the exposure lamp 232, condenses the reflected light image from the original D to the full-color CCD sensor 234 by the lens 233, and Obtain a decomposed image signal. The color-separated image signal passes through an amplifier circuit (not shown), is subjected to image processing by a video processing unit (not shown), and is sent to a printer unit B via an image memory (not shown).
[0102]
For example, a photosensitive drum 201 which is an image forming unit which is an image carrier of the printer unit B is rotatably supported in the direction of an arrow. Around the photosensitive drum 201, a pre-exposure lamp 211, a corona charger, an image writing unit and an image forming unit such as a laser exposure optical system 203, a potential sensor 212, and four developing units 204y and 204c of different colors. 204m, 204Bk, on-drum light amount detection means 213, an image transfer unit such as a transfer device 205, and a cleaning device 206 are arranged.
[0103]
The image signal from the reader unit A in the laser exposure optical system 203 is converted into an optical signal in a laser output unit (not shown). The laser light converted into the optical signal is reflected by the polygon mirror 203a, and is projected on the surface of the photosensitive drum 201 through the lens 203b and the mirror 203c.
[0104]
At the time of image formation by the printer unit B, the photosensitive drum 201 is rotated in the direction of the arrow, is discharged by the pre-exposure lamp 211, and is uniformly charged by, for example, the charger 202 which is an image forming unit and an image writing unit. Then, a light image E is radiated for each separation color to form a latent image.
[0105]
Next, the latent image is developed on the photosensitive drum 201 by predetermined developing units 204y, 204c, 204m, and 204Bk, and a toner image based on a resin and a pigment is formed on the photosensitive drum 201. The developing units 204y, 204c, 204m, and 204Bk are adapted to selectively approach the photosensitive drum 201 in accordance with each separation color by the operation of the eccentric cams 224y, 224c, 224m, and 224Bk.
[0106]
The toner image on the photosensitive drum 201 is conveyed from the recording material cassette 207, is attracted to the transfer device 205, and is transferred to the recording material supplied to a position facing the photosensitive drum 201. The transfer device 205 includes a transfer drum 205a, a transfer charger 205b, an adsorption charger 205c which electrostatically adsorbs a recording material to a recording material supporting sheet 205f described later, an adsorption roller 205g opposed to the adsorption charger 205c, and an inner charging device. Device 205d, an outer charger 205e, and the like. A recording material carrying sheet 205f made of a dielectric material is integrally stretched in a cylindrical shape in a peripheral opening area of the transfer drum 205a which is rotatably supported by a shaft. The recording material supporting sheet 205f of the image forming apparatus 200 of the present embodiment uses a dielectric sheet such as a polycarbonate film.
[0107]
As the transfer drum 205a of the drum-shaped transfer device 205 is rotated, the toner image on the photosensitive drum 201 is transferred onto the recording material carried on the recording material carrying sheet 205f by the transfer charger 205b. In this manner, a desired number of color images are transferred to the recording material conveyed (rotated) while electrostatically attracted to the recording material carrying sheet 205f, thereby forming a full-color image.
[0108]
In the case of full-color image formation, the recording material on which the transfer of the four color toner images has been completed in this manner is separated from the transfer drum 205a by the action of the separation claw 208a, the separation push-up roller 208b, and the separation charger 205h. The toner image is fixed by the heat roller fixing device 209, and is finally discharged to the discharge tray 210. On the other hand, the photosensitive drum 201 after the transfer is prepared for the image forming process again after the residual toner on the surface is cleaned by the cleaning device.
[0109]
When images are formed on both sides of the recording material, the conveyance path switching guide 219 switches immediately after the recording material passes through the fixing device 209. The recording material is guided by the transport path switching guide 219, is once guided to the reversing path 221a via the transport vertical path 220, and is then driven by the reverse rotation of the reversing roller 221b, with the rear end when fed in, leading. , And is sent out to the two-sided conveyance path 258. That is, the recording material is transported by switchback.
[0110]
Thereafter, the recording material stops at the conveyance roller 256, and the timing is adjusted to the position of the toner image on the photosensitive drum 201, and then the image is formed on the other surface again by the above-described image forming process.
[0111]
Further, a fur brush is used to prevent scattering of powder such as toner on the recording material supporting sheet 205f of the transfer drum 205a and adhesion of toner or oil on the recording material supporting sheet 205f to the recording material supporting sheet 205f. The recording material is provided by a backup brush 215 facing the fur brush 214 via the recording material supporting sheet 205f and the oil removing roller 216 via the oil removing roller 216 and the recording material supporting sheet 205f. The carrier sheet 205f is cleaned. Such cleaning is performed before or after image formation. Also, it is performed as needed when a jam (paper jam) occurs.
[0112]
Further, the image forming apparatus 200 of the present embodiment rotates the eccentric cam 225 at a desired timing to operate the cam follower 205i integrated with the transfer drum 205a, so that the recording material supporting sheet 205f and the photosensitive drum 201 And the gap can be set arbitrarily. For example, during standby or when the power is off, the transfer drum 205a and the photosensitive drum 201 are separated.
[0113]
As shown in FIG. 10, also in the image forming apparatus 200 of the present embodiment, the distance (L4) from the image writing unit to the image transfer unit is long. That is, from the exposure position F of the photosensitive drum 201 exposed by the light image E reflected by the mirror 203c to the transfer charger 205b for transferring a toner image to a recording material, four developing units 204y, 204c, and 204m. , 204Bk. For this reason, the distance (L4) from the exposure position F, which is the image writing position, to the transfer charger 205b is longer than the distance (corresponding to L2 described above) when there is one developing device.
[0114]
For this reason, when the peripheral speed of the photosensitive drum 201, the peripheral speed of the transfer drum 205a, and the transport speed of the recording material are the same, the image forming apparatus 200 is upstream of the transfer charger 205b by a distance equal to the distance L4. The toner image is transferred to the recording material being conveyed on the side. Therefore, in order to adjust the position of the image according to the position of the recording material, a recording material end detection sensor is disposed at a position of a distance L4 upstream from the transfer charger 205b, and the recording is performed. The position of the material must be detected.
[0115]
However, even if the position of the recording material is detected at the position of the distance L4, the position often shifts while the recording material is conveyed by the distance L4. Specifically, even if the recording material end detection sensor is installed near the transport roller 254 at the position of the distance L4, the recording material is thereafter transported to the transfer charger 205b by a transport means such as the transport roller 255. Since the sheet passes through the registration roller section and the suction roller 205g, the position of the end portion may be deviated therebetween. Further, when the conveying speed of the recording material is higher than the peripheral speed of the photosensitive drum 201, the recording material end detection sensor must be disposed further upstream than the distance L4, and the recording material is further increased. It often shifts. For this reason, even if the position of the recording material is detected at the position of the distance L4, it becomes meaningless.
[0116]
Therefore, the image forming apparatus 200 of the present embodiment also has the recording material edge detection sensor 101 disposed near the upstream side of the transfer charger 205b, and detects, for example, the displacement of three recording materials and averages them. The position at which the photosensitive drum is exposed is adjusted based on the calculated value, and the average value is used as the estimated positional deviation amount of the recording material to be sent thereafter. Therefore, also in the image forming apparatus of the present embodiment, the position can be accurately adjusted even if the distance L4 is long.
[0117]
The configuration and operation of the image forming apparatus 200 according to the second embodiment relating to the control for aligning the recording material and the image position are the same as the configuration and operation relating to the control of the image forming apparatus 100 according to the first embodiment. Description and illustration are omitted.
[0118]
Further, in the case of the image forming apparatus of the present embodiment, the end of the recording material is detected at a position where the recording material is attracted to the transfer drum 5a, that is, at a position where the recording material does not shift at all to the transfer portion thereafter. Therefore, the image forming apparatus according to the first embodiment is characterized in that the accuracy of the alignment is slightly better.
[0119]
Further, the image forming apparatus according to the first embodiment also includes the image forming apparatus according to the first embodiment in the double-sided conveyance path 258 so that the position of the recording material and the image in the main scanning direction can be aligned at the time of double-side transfer. Similarly to the above, a receiving plate (not shown) and a skew feeding roller are arranged.
[0120]
As described above, the alignment method and configuration in the image forming apparatus according to the first embodiment can be applied to the image forming apparatus according to the second embodiment, so that the versatility is very high. It turns out that.
[0121]
As described above, in the image forming apparatuses 100 and 200 of the first and second embodiments, when the image is transferred to the first side and when the image is transferred to the second side, the image forming apparatuses 100 and 200 are placed near the secondary transfer unit 5b and the charge transfer unit 205b. Because the end position of the recording material is detected and the image position is adjusted, the distance from the detection of the end position to the transfer is short, and the end position of the recording material during continuous operation has little fluctuation. Highly accurate image alignment can be performed.
[0122]
In addition, the image forming apparatuses 100 and 200 according to the first and second embodiments are used as sensors for detecting the end position of a recording material, and are fixed-line reading line sensors that have been rapidly becoming popular and inexpensive in recent years. Is used, the end position can be detected with a resolution of at least about 200 dpi for all sizes of the recording material, and very accurate image alignment can be performed together with fine correction of the image position. It can be performed.
[0123]
According to the image forming apparatuses 100 and 200 of the first and second embodiments, during the transfer of the image on the second side, one side of the recording material is placed on the two-sided conveyance paths 21c and 258 according to the size of the recording material. In order to convey the recording material by correcting the end position deviation at the time of reverse conveyance of the recording material, which is the largest cause of the deviation of the end position of the recording material, because the recording material is conveyed in a state where the recording material is brought into contact with the recording material. Regardless of single-side transfer or double-side transfer at only one location near the secondary transfer section 5b and the transfer charger 205b, the position of the recording material and the image can be accurately adjusted.
[0124]
The image forming apparatuses 100 and 200 according to the first and second embodiments correct the image end position with respect to the subsequent recording material position according to the change in the end position of the recording material. Even for a minute change in the end position of the recording material to be conveyed, or an extremely rare sudden change, it is possible to reduce the change by calculating the average value of the end positions by the end average value calculating means. The position of the recording material and the position of the image can be accurately adjusted with a simple and inexpensive configuration.
[0125]
In the image forming apparatuses 100 and 200 according to the first and second embodiments, the average value storage unit 114 for each cassette stores the final average value of the end position of the recording material calculated by the end average value calculation unit 111 in each storage unit. 71, 72, 73 and the recording material cassettes 207, 207, so that the recording material can be changed even if the storage unit or the cassette changes during the operation of continuously forming an image on the recording material. , And the position of the recording material and the image position can be accurately adjusted.
[0126]
In the image forming apparatuses 100 and 200 according to the first and second embodiments, even if there is a recording material whose end position is suddenly shifted, the end abnormal value detecting unit 113 detects the end material and the end average value calculating unit 111. It is possible to calculate the average value by excluding the value of the end position which is equal to or more than the predetermined value, so that the recording material position and the image position can be accurately matched with a simple and inexpensive configuration. Can be.
[0127]
In the image forming apparatuses 100 and 200 according to the first and second embodiments, the center of the main scanning direction is set as a reference for all sizes of the recording material in the image forming apparatus, and the conveyance is performed together. The recording material can be accurately aligned with the image position while realizing the conveyance of the recording material.
[0128]
For the above reasons, the image forming apparatuses 100 and 200 according to the first and second embodiments realize an inexpensive and simple configuration, and do not need to increase the apparatus size. Further, the position of the recording material and the position of the image can be adjusted with high accuracy without lengthening the transport path.
[0129]
【The invention's effect】
The image forming apparatus of the present invention detects the end position of the recording material in the vicinity of the image transfer unit and adjusts the image position. Therefore, the distance from the detection of the end position to the transfer is short, and the image forming apparatus is in continuous operation. Since the fluctuation of the end position of the recording material at the time is small, it is possible to perform highly accurate image alignment control.
[0130]
In the image forming apparatus of the present invention, when performing image transfer on the second surface, the recording material is conveyed in a state where one side of the recording material is abutted against the guide portion of the reversing conveyance means. In order to convey the recording material after correcting the end position deviation at the time of reversal conveyance of the recording material, it is possible to perform the single-sided transfer or the double-sided transfer by detecting only one location near the image transfer unit. The position of the image can be accurately adjusted.
[0131]
According to the image forming apparatus of the present invention, since the position of the edge of the recording material is corrected based on the change in the position of the edge of the recording material, the position of the edge of the recording material continuously conveyed is corrected. The average value of the end positions can be calculated by the end average value calculating means even for a minute change in the position of the portion or a sudden change that occurs very rarely, so that the change can be reduced and the cost is simple. With such a configuration, the position of the recording material and the position of the image can be accurately adjusted.
[0132]
In the image forming apparatus of the present invention, the storage means stores the final average value of the end position of the recording material calculated by the end average value calculation means for each stacking means, so that the recording material is continuously recorded on the recording material. Even if the stacking unit changes during the operation of forming an image, it is possible to cope with a change in the position of the recording material, and the position of the recording material and the image position can be accurately matched.
[0133]
According to the image forming apparatus of the present invention, even when there is a recording material whose end position is suddenly shifted, the average value is calculated by excluding a value of the end position which is equal to or more than a predetermined value by the end average value calculating means. Therefore, the position of the recording material and the image position can be accurately matched with a simple and inexpensive configuration.
[0134]
According to the image forming apparatus of the present invention, the center of the main scanning direction in the image forming apparatus is used as a reference for all sizes in the image forming apparatus, and the conveyance is performed together. Thus, the recording material and the image position can be accurately adjusted.
[0135]
The image forming apparatus of the present invention realizes an inexpensive and simple configuration, and further does not require an increase in the size of the apparatus. Further, the position of the recording material and the position of the image can be adjusted with high accuracy without lengthening the transport path.
[Brief description of the drawings]
FIG. 1 is a schematic main cross-sectional view of a copying machine that is a full-color image forming apparatus according to a first embodiment of the present invention.
FIG. 2 is a perspective view of a recording material end detection sensor incorporated in the image forming apparatus of FIG. 1;
FIG. 3 is a flowchart illustrating an operation of adjusting the position of a recording material and the position of an image in the image forming apparatus.
FIG. 4 is a diagram for explaining end position fluctuation during normal continuous paper feeding.
(A) It is a graph which shows the change of an end part position.
FIG. 4B is a diagram illustrating a state of the recording material placed in the storage unit.
FIG. 5 is a diagram for explaining end position fluctuation when a recording material is pressed to the back side.
(A) It is a graph which shows the change of an end part position.
FIG. 4B is a diagram illustrating a state when the number of recording materials placed in the storage unit is large.
FIG. 4C is a diagram illustrating a state where the number of recording materials placed in the storage unit is small.
FIG. 6 illustrates end position fluctuations when only two recording materials at a boundary surface between a lower recording material and an upper recording material when the recording materials are added are displaced. FIG.
(A) It is a graph which shows the change of an end part position.
FIG. 4B is a diagram illustrating a state of the recording material placed in the storage unit.
FIG. 7 is a diagram for explaining end position fluctuation when a recording material added later is totally displaced.
(A) It is a graph which shows the change of an end part position.
FIG. 4B is a diagram illustrating a state of the recording material placed in the storage unit.
FIG. 8 is a control block diagram of the image forming apparatus of FIG. 1;
FIG. 9 is a plan view of a skew feeding roller and a recording material receiving plate.
FIG. 10 is a schematic main cross-sectional view of a copying machine that is a full-color image forming apparatus according to a second embodiment of the present invention.
[Explanation of symbols]
P Recording material
A Leader part
B Printer section
D manuscript
1. Photosensitive drum (image forming means)
2 Corona charger (image writing means, image forming means)
3. Laser exposure optical system (image writing means, image forming means)
4 Developing device
5 Intermediate transfer belt (image forming means)
5b Secondary transfer unit (image transfer unit)
21a Transport vertical path
21b Reverse path
21c Double-sided conveyance path
34 Full Color CCD Sensor
51 reversing roller
52 Double-sided conveying roller
53 Double-sided conveyance roller (reversal conveyance means, skew conveyance section)
54 Double-sided conveyance roller (reversing conveyance means, skew conveyance section)
55 Double-sided conveyance roller (reversal conveyance means, skew conveyance section)
71 Storage section
72 storage
73 storage
91 Registration roller (transportation means)
100 Image forming apparatus
101 Recording Material Edge Detection Sensor (Edge Detection Means)
102 Receiving plate for recording material (reverse transport means, guide section)
111 Edge Average Value Calculation Unit (Edge Average Value Calculation Means)
112 control unit (image position adjustment control means)
113 Edge abnormal value detector
114 Average value storage unit for each cassette (storage means)
115 Image Processing Unit (Image Writing Means)
116 External network
117 Average value storage (storage means)
200 Image forming apparatus
201 Photosensitive drum (image forming means)
202 Charger (image writing unit, image forming unit)
203 Laser exposure optical system (image writing unit, image forming unit)
204y developing unit
204c developing unit
204m developing unit
204Bk developing unit
205 transfer device
205a transfer drum
205b Charge transfer device (image transfer means)
205g suction roller
234 Full color CCD sensor
255 transport roller (transport means)
258 Double-sided conveyance path

Claims (10)

Image writing means capable of arbitrarily moving the position of the image in the main scanning direction,
Image forming means for forming an image on a recording material having the image writing means,
Image transfer means for transferring the image formed by the image forming means to the recording material,
Conveying means for conveying the recording material to the image transfer means,
An end detection unit disposed near the image transfer unit and detecting an end of the recording material conveyed by the conveyance unit in the main scanning direction;
Edge average value calculating means for calculating an average value of the edge positions of a plurality of continuous recording materials detected by the edge detecting means,
An image for controlling the image writing unit in the main scanning direction with respect to the subsequent recording material by adjusting the image writing unit in accordance with the average edge position of the recording material calculated by the edge average value calculation unit. Position adjustment control means,
An image forming apparatus having an automatic margin adjustment function, comprising: An image forming apparatus further includes a reversing conveyance unit that conveys a recording material on which an image is recorded by the image transfer unit and which is turned upside down to the image transfer unit,
The edge detecting means detects an edge of the recording material turned over in the main scanning direction,
The edge average value calculation means calculates an average value of the edge positions of the plurality of continuous recording materials that have been turned upside down and detected by the edge detection means,
The image position adjustment control means controls a main image of a subsequent inverted recording material in accordance with the average end position of the reversed recording material calculated by the edge average value calculating means. 2. The image forming apparatus according to claim 1, wherein the position in the scanning direction is moved by controlling the image writing unit. An image forming apparatus further includes a reversing conveyance unit that conveys a recording material on which an image is recorded by the image transfer unit and which is turned upside down to the image transfer unit,
The reversing conveyance unit includes a skew conveyance unit configured to skewly convey the recording material reversed, and a guide unit configured to receive and guide a side portion of the recording material conversed by the skew conveyance unit. And having
3. The automatic margin adjustment function according to claim 1, wherein the guide section is movable in a direction intersecting with a transport direction of the recording material in accordance with a size of the recording material. 4. An image forming apparatus comprising: Storage means for storing a final average value of the end position of the recording material calculated by the end average value calculation means,
The image position adjustment control unit controls the image writing unit based on the final average value stored in the storage unit for the position in the main scanning direction of the image with respect to the first recording medium when the apparatus is restarted. An image forming apparatus having an automatic margin adjustment function according to claim 1. A plurality of loading means disposed on the upstream side of the transport means and loaded with the recording material,
Storage means for storing a final average value of the end position of the recording material calculated by the end average value calculation means for each of the loading means,
The image position adjustment control unit writes the image based on the final average value stored in the storage unit, which corresponds to the loading unit on which a recording material on which an image is first formed is loaded when the apparatus is restarted. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus controls the unit. A plurality of loading means disposed on the upstream side of the transport means and loaded with the recording material,
Storage means for storing a final average value of the end position of the recording material calculated by the end average value calculation means for each recording material of each loading means,
The image position adjustment control unit, when the loading unit is switched, controls the image writing unit based on the final average value stored in the storage unit corresponding to the switched loading unit. An image forming apparatus having the automatic margin adjustment function according to claim 1. The margin according to any one of claims 1, 2, 4, and 6, wherein the edge average value calculation unit excludes a value of an edge position equal to or more than a predetermined value from the calculation of the average value. An image forming apparatus having an automatic adjustment function. The image forming apparatus according to claim 1, wherein the conveyance unit conveys the recording material with reference to a center. The image forming apparatus according to claim 1, wherein the edge detection unit is disposed between the conveyance unit and the image transfer unit. 4. 10. The system according to claim 1, wherein said edge detecting means is a fixed line sensor disposed in an area corresponding to a range corresponding to an edge of the entire size of said recording material. An image forming apparatus having the automatic margin adjustment function according to any one of the preceding claims.

Images