JP3702670B2 - Image forming apparatus, writing method of image forming apparatus, image forming method, and control method of image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, etc., which forms a toner image on the surface of a photoreceptor by an electrophotographic method, and transfers the toner image onto a transfer paper, its writing method, and its control method. More specifically, image formation is performed with reference to the position of the transfer paper, and the leading edge position of the toner image formed on the surface of the photosensitive member and the leading edge position of the transfer paper are highly accurate with no slight variation. The present invention relates to an image forming apparatus using a digital method capable of alignment, a writing method thereof, and a control method thereof.
[0002]
[Prior art]
In an electrophotographic image forming apparatus, a charging unit, a writing unit, and a developing unit are provided at the peripheral portion of a rotating photoconductor, and after the surface of the photoconductor is uniformly charged by the charging unit, image exposure is performed by the writing unit. By doing so, a latent image of the image is formed, and the latent image is developed by developing means to form a toner image on the surface of the photoreceptor. On the other hand, the transfer paper fed from the transfer paper storage means or the like is sent to the transfer position, and the toner image is transferred onto the transfer paper at the transfer position. In this transfer, it is required that the leading edge position of the transfer paper and the leading edge position of the toner image coincide with each other. If there is a variation in the coincidence of the tip positions of the two, the image of the tip or rear end will be lost. In addition, in the case of an application in which image formation is performed at a desired position on a transfer sheet on which ruled lines or the like are printed in advance, if the image formation is performed after a position is determined by trial printing, the tip position If there is a variation in the match, a shift occurs at each copy position, and an image cannot be formed at a desired position.
[0003]
The inventors of the present invention have intensively studied the cause of the above-described variation in the coincidence of the tip position, and have found that the following problems occur.
[0004]
When copying using an analog image forming apparatus, the original is placed at a predetermined position on the platen glass, and scanning is performed from one end of the original to the other using a scanning optical system, thereby forming an image. A latent image is formed by irradiating a manuscript image onto a rotating photoconductor via an optical system. Therefore, the scanning start time is the image irradiation start time on the photoconductor, and image formation is triggered by the position detection of the scanning optical system. In general, position detection is performed when the scanning optical system returns (return path), and the scanning start time of the scanning optical system is predicted by predicting the scanning start time of the forward path after reversing the scanning optical system. . On the other hand, it is necessary to synchronize the irradiation start time and the transfer paper conveyance so that the irradiation start position of the image on the photoconductor and the leading edge position of the transfer paper match at the transfer position. Conventionally, a registration roller is provided on the upstream side of the transfer position in order to take the transfer paper transport start timing from such a request, and the transfer paper is temporarily stopped at the position of the registration roller to wait for the trigger. By starting the transfer of the transfer paper by starting the driving of the registration roller based on the above, the exposure start time of the photosensitive member surface from the scanning optical system is synchronized with the transfer paper transfer start time, and the leading edge position of the transfer paper And the position of the leading edge of the toner image on the photoconductor.
[0005]
However, it has been found that there is variation in the transfer paper conveyance start timing when the transfer paper conveyance is started by starting the driving of the registration roller in the above configuration.
[0006]
That is, when the transfer paper starts to be transferred from the registration roller, the transfer paper must be slightly held between the registration rollers in advance. For this purpose, the transfer paper is fed from a roller upstream of the registration roller and abuts against the registration roller so that it slightly enters the nip portion of the registration roller pair to be held and stopped. In this case, if the type or size of the transfer paper is different, the intrusion distance into the nip portion essentially varies. This factor is considered to be due to the difference in the coefficient of friction of the transfer paper. Therefore, even if the transfer paper transfer start time from the registration roller is synchronized with the exposure start time by the scanning optical system, the variation in the transfer paper transfer start position caused by the intrusion distance to the registration roller cannot be eliminated. .
[0007]
Further, the transfer roller does not always start to be transported without any error due to the driving of the registration roller. That is, the transfer paper is transported by the frictional force acting between the registration roller surface and the transfer paper, but at the start of driving, a large frictional force acts between the registration roller surface and the transfer paper. Essentially accompanied by slip. This slipping becomes even easier because paper dust or the like adheres to the surface of the registration roller over a long period of use, and promotes variations in the timing of starting the conveyance.
[0008]
Further, since the frictional force with the transfer paper acts on the registration roller as described above, it gradually wears. For this reason, the resist roller diameter becomes smaller after a long period of use. When the diameter of the registration roller is reduced due to wear, the transfer speed of the transfer paper conveyed by the registration roller driven at the same rotational speed as in the initial stage becomes slower than that in the initial stage. This is understood from the fact that the outer peripheral distance of the registration roller becomes smaller due to wear than in the initial stage. As described above, since the transfer paper is fed from the registration roller at a slower speed, the time to reach the transfer position is also delayed, and the toner image on the photosensitive member cannot be synchronized. In such a situation, the toner image precedes, leading to a problem that the toner image at the front end is missing.
[0009]
On the other hand, when copying using a digital image forming apparatus, the read image data is temporarily stored in the memory, and when printing, the image data is read from the memory and written onto the photosensitive member by a writing means. The latent image is written. Therefore, instead of using the position detection signal of the scanning optical system as a trigger, a separate trigger is provided, and the driving of the registration roller is started in synchronization with the writing start time, so that the leading edge of the toner image and the leading edge of the transfer paper are Alignment is performed. As described above, in the same manner as the analog method described above, the transfer paper is started to be conveyed from the registration roller to synchronize with the toner image on the photoconductor, and the transfer paper alignment is essentially changed. There is no technology.
[0010]
On the other hand, various functions are incorporated in recent image forming apparatuses. As one of them, a margin setting function for providing a margin for a binding margin or the like is provided. As a means for achieving this function, conventionally, a margin is provided by advancing the transfer paper transfer start time from the registration roller. Thus, in order to advance the transfer paper conveyance start time earlier, it is necessary to wait in advance for the transfer paper from the transfer paper storage means to the position of the registration roller. However, while speeding up the first copy and improving the productivity of copying are required, the time for transporting from the transfer paper storage means to the registration roller has been cut to the limit. Is something that cannot be changed. Therefore, the margin setting function can be applied for the first time by setting the normal conveyance start time later than the margin setting conveyance start time. For this reason, incorporating the margin setting function causes a delay in the first copy time in normal copying, and in the case of a large number of copies, this causes a problem of a decrease in copy productivity. End up.
[0011]
Furthermore, as described above, since the transfer paper is started to be conveyed from the registration roller, synchronization is obtained. Therefore, the same variation as described above is generated. Have difficulty.
[0012]
[Problems to be solved by the invention]
  The present invention provides the following(1), (2)The purpose is to solve the problem.
[0013]
(1) A digital image can be used without being constrained by an image forming apparatus that has been adopted so that a transfer sheet on a registration roller is re-fed toward a transfer position on the basis of a writing start time of a latent image by a writing unit. The image forming apparatus, which is preferably applied to the image forming apparatus of the system, is configured so that the high-speed image processing is performed with high accuracy so that the front end of the image is aligned with the front end of the transfer paper with high accuracy and no variation. An object is to provide a writing method of an apparatus and a control method of an image forming apparatus.
[0014]
{Circle around (2)} Transfer paper conveyed in the conveyance path is conveyed while being held between upper and lower rotating rollers. If the drive roller is used for a long time, the drive roller is worn and a phenomenon occurs in which the transfer paper transport amount per rotation of the drive roller is reduced. When such a phenomenon occurs, an image recorded in the form in which the leading edge of the transfer paper and the leading edge of the toner image coincide with each other at the initial stage is recorded in a shifted form. SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus and an image forming method in which an image in which a toner image front end coincides with a transfer paper front end is formed with high accuracy over a long period of time.
[0016]
[Means for Solving the Problems]
  the above(1) and (2)An image forming apparatus intended for
  Form a latent imagePhotoconductor, the photoconductorUpWrite image toMuWriting means, beforeDivingImage to developerThedevelopingDoDeveloping means,Transfer paper storage means, develop the developed image on the photoreceptorTransfer to transfer paperRollCopying means,A transfer path for transferring the transfer paper stored in the transfer paper storage means to a transfer position, and a registration roller provided in the transfer path.In the image forming apparatus provided,Based on a counting unit that counts the number of image formations, a paper detection sensor that detects a transfer paper between the transfer position transferred to the transfer paper by the transfer unit and the registration roller, and a detection signal of the transfer paper by the paper detection sensor Write control means for controlling the start timing of writing to be changed based on the count of the number of images formed by the counting means.An image forming apparatus characterized in that (Invention of Claim 1))
InThis is achieved.
[0020]
  the above(1) and (2)The image forming method aiming at
  A photosensitive member for forming a latent image, a writing unit for writing an image on the photosensitive member, a developing unit for developing the latent image with a developer, a transfer paper storage unit, and a developed image on the developed photosensitive member on a transfer sheet. Transfer means for transferring, transport means for transporting transfer paper stored in the transfer paper storage means to a transfer position through a transport path, and registration rollers provided in the transport pathTheIn the image forming method of the image forming apparatus provided, the transfer position between the transfer position transferred to the transfer paper by the transfer means and the registration rollerTo detect transfer paperPaper detection sensorAnd the write start timing based on the detection signal of the transfer paper by the paper detection sensor,An error in the conveyance time during conveyance from the paper detection sensor to the transfer position is corrected.DecideTo controlWriting control meansAn image forming method (claim)3Invention)
Achieved by:
[0023]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the image forming apparatus of the present invention will be described with reference to the overall configuration diagram shown in FIG. The image forming apparatus of the present embodiment can form an image on both sides of the transfer paper, but the present invention is not limited to such a configuration.
[0024]
The image forming apparatus shown in FIG. 1 is a digital image forming apparatus, and includes an image reading unit A, an image processing unit B (not shown), an image forming unit C, and a transfer paper transport unit D.
[0025]
An automatic document feeder that automatically conveys the document is provided above the image reading unit A. The document placed on the document table 11 is separated and conveyed by the document conveyance roller 12 to the reading position 13a. The image is read. The document after the document reading is completed is discharged onto the document discharge tray 14 by the document transport roller 12.
[0026]
On the other hand, an image of an original when placed on the platen glass 13 includes a first mirror unit 15 including an illumination lamp and a first mirror constituting a scanning optical system, a second mirror positioned in a V shape, and a third mirror. Reading is performed by the reading operation of the second mirror unit 16 composed of a mirror at the speed V of the first mirror unit 15 and the moving exposure at the speed V / 2 in the same direction by the second mirror unit 16.
[0027]
The read image is formed on the light receiving surface of the image sensor CCD, which is a line sensor, through the projection lens 17. The line-shaped optical image formed on the image sensor CCD is sequentially photoelectrically converted into an electric signal (luminance signal) and then A / D converted, and the image processing unit B performs processing such as density conversion and filter processing. Then, the image data is temporarily stored in the memory.
[0028]
In the image forming unit C, on the outer periphery of a drum-shaped photosensitive drum 21 serving as an image forming unit as an image forming unit, a charger 22 serving as a charging unit, a developing device 23 serving as a developing unit, a transfer unit 24 serving as a transfer unit, A separator 25 as a separating unit and a cleaning device 26 as a cleaning unit are arranged in the order of operation. The photoconductor drum 21 is formed by coating a photoconductive compound on a drum base. For example, an organic photoconductor (OPC) is used, and the photoconductor drum 21 is driven and rotated in the clockwise direction in the drawing.
[0029]
After the rotating photosensitive drum 21 is uniformly charged by the charger 22, the exposure optical system 30 performs image exposure based on the image signal called from the memory of the image processing unit B. The exposure optical system 30 serving as a writing means uses a laser diode (not shown) as a light source, passes through a rotating polygon mirror 31, an fθ lens (no symbol), and a cylindrical lens (no symbol), and the optical path is bent by a reflection mirror 32 to perform main scanning. As a result, image exposure is performed at position A on the photosensitive drum 21, and a latent image is formed by rotation (sub-scanning) of the photosensitive drum 21. In this embodiment, the character portion is exposed to form a reverse latent image.
[0030]
The reverse latent image on the photosensitive drum 21 is reversely developed by the developing device 23, and a visible image is formed as a toner image on the photosensitive layer surface of the photosensitive drum 21. The transfer paper transport unit D is provided with paper feed units 41 (A), 41 (B), and 41 (C) in which transfer papers P of different sizes are stored below the image forming unit. A manual paper feed unit 42 for feeding paper is provided, and the transfer paper P selected from any of them is fed along the paper feed path 40 by the guide roller 43, and the inclination of the transferred paper is fed. The transfer paper P is temporarily stopped by a registration roller 44 that corrects the bias and then fed, and the toner image on the photosensitive drum 21 is transferred by the transfer unit 24 at the transfer position B via the pre-transfer roller 43a. The transfer paper P is transferred to the paper P, then neutralized by the separator 25, and the transfer paper P is separated from the surface of the photosensitive drum 21, and is transported to the fixing device 50 by the transport device 45.
[0031]
The fixing device 50 includes a fixing roller 51 and a pressure roller 52. By passing the transfer paper P between the fixing roller 51 and the pressure roller 52, the toner is fused by heating and pressing. . After the fixing of the toner image on one side, the transfer paper P is subjected to double-sided image formation for forming a toner image on the other side according to the mode described below, or is discharged onto the paper discharge tray 64 in a state of single-sided image.
[0032]
When the double-sided image forming mode is selected, the transfer paper P that has finished image fixing on the front surface descends along the reverse conveyance path 60, is once carried into the switchback path 60 a, and is carried out to be unloaded between the front and back surfaces. The transfer paper P is temporarily stopped by a registration roller 44 that performs reversal and is fed again along the paper feed path 40 by the guide roller 43 through the second reverse transport path, and corrects the inclination and bias of the transfer paper. The toner image of the back image formed on the photosensitive drum 21 is transferred to the back surface of the transfer paper P by the transfer device 24 at the transfer position B and then separated and conveyed for fixing. Then, the paper is discharged onto the paper discharge tray 64.
[0033]
When the single-sided image formation mode is selected, the transfer paper P that has been fixed on the front surface image is straightened and discharged onto the paper discharge tray 64, or is discharged after the upper and lower surfaces are reversed by the reverse switching member 62. The paper is discharged onto the paper tray 64.
[0034]
Each of the embodiments described below is an invention related to a transfer position when a toner image is transferred onto a transfer sheet. Therefore, the main part diagram shown in FIG. A position at which writing is performed by the exposure optical system 30, a paper detection position C of a paper detection sensor S 1 that performs transfer paper detection described later, and a transfer position B at which a toner image is transferred onto the transfer paper by a transfer device 24. The relationship part is taken out and shown. In the embodiment of the present invention, the distance (A-B) is 120 mm, the distance (C-B) is 132 mm, and the distance (A-registration roller) is 150 mm. Further, the conveyance speed V by the conveyance means such as a registration roller is set to 350 mm / sec.
[0035]
Example 1
  In the image forming apparatus described with reference to FIG. 1, a paper detection sensor S <b> 1 is provided along the paper feed path 40 on the downstream side of the registration roller 44 and upstream of the transfer position B. The registration roller 44 stops by abutting the leading end portion of the transfer paper conveyed from the paper supply unit 41 serving as transfer paper storage means, and corrects this when the supplied transfer paper is tilted or biased. The paper detection sensor S1 is a sensor that detects the leading end portion of the transfer paper that passes through a registration roller that re-feeds toward the transfer position B. FIG. 3 shows a block diagram of the present embodiment. The exposure optical system 30 serving as a writing means starts writing based on a signal passing through the front end of the transfer paper detected by the paper detection sensor S1. Control is made. That is, when the transfer control unit CPU (1) receives a transfer paper leading edge detection signal from the paper detection sensor S1, the writing control unit CPU (1) calls a previously prepared writing start timing, performs timing setting, waits for timing up, and starts image exposure. Control is performed so that the leading edge of the image matches the leading edge of the transfer paper.
[0036]
By providing the paper detection sensor S1 on the downstream side of the registration roller 44 with such a configuration, the leading edge of the transfer paper that moves in a posture in which the inclination is corrected is detected. The leading edge coincides with the leading edge of the transfer paper with high accuracy at the transfer position B.
[0037]
(Example 2)
  In the image forming apparatus of this embodiment, a paper detection sensor S1 is provided along the paper feed path 40 on the upstream side of the transfer position B where transfer is performed by the transfer device 24, and transfer is performed from the paper detection sensor S1 along the paper feed path 40. The distance (C-B) to the position B is set to be equal to or longer than the distance (A-B) from the writing position A to the transfer position B on the photosensitive drum 21. It is characterized by being.
[0038]
Here, the paper detection sensor S1 is preferably a paper detection sensor for detecting passage of the leading end of the transfer paper to be fed. In addition, it is preferable to provide a registration roller 44 that temporarily stops the transfer paper transported from the paper supply unit 41 serving as transfer paper storage means and transports it again to the transfer position B on the upstream side of the paper detection sensor S1. The exposure optical system 30 as writing means is preferably a laser shown in FIG. 1 or an LED (laser diode).
[0039]
The image forming apparatus has a write control unit CPU (2) as shown in the block diagram of FIG. 4, and when the paper detection sensor S1 detects the leading edge of the transfer paper, the write control unit CPU (2). Calls the write timing from the write timing memory (2), sets the write timing, and starts writing by the exposure optical system 30 when the write timing elapses. Here, the writing timing stored in the memory (2) is the time required for the transfer paper to move by the length obtained by subtracting the length of the distance (AB) from the length of the distance (CB). Applicable.
[0040]
With such a configuration, a highly accurate image leading edge coincident with the leading edge of the transfer paper particularly adapted to the digital recording method can be obtained on the transfer paper on which a large number of prints are made per time at the transfer position B.
[0041]
(Example 3)
  The image forming apparatus according to the present embodiment includes a writing control unit CPU (3) that controls the exposure optical system 30 serving as writing means, and a paper detection sensor S1 is provided in the paper feed path 40 to control writing. The section CPU (3) is characterized in that control is performed so as to determine the writing start timing of the exposure optical system 30 based on a signal obtained by detecting the leading edge of the transfer paper fed by the paper detection sensor S1.
[0042]
The paper feed path 40 is provided with a registration roller 44 that temporarily stops the transfer paper conveyed from the paper feed unit 41 serving as transfer paper storage means, corrects the tilted posture correctly, and re-feeds it toward the transfer device 24. The paper detection sensor S <b> 1 is preferably arranged on the downstream side of the registration roller 44.
[0043]
As shown in the block diagram of FIG. 5, the image forming apparatus is provided with an image data memory (3) for storing image data. The writing control unit CPU (3) detects the leading edge of the transfer paper by the paper detection sensor S1. Then, based on this detection signal, the write timing is called from the write timing memory (3) and set, and when set up, the image data is called from the image data memory (3) and writing is started by the exposure optical system 30. Is made.
[0044]
With such a configuration, especially when the image data memory (3) has a function of storing a large number of image data, a large number of continuous prints for many types of images are made per time, and the leading edge of the image is transferred to the leading edge of the transfer paper. Will be obtained.
[0045]
Example 4
  The image forming apparatus of this embodiment is provided with a paper detection sensor S1 along the paper feed path 40 downstream of the registration roller 44 and upstream of the transfer position B, and is conveyed from a paper feed unit 41 serving as transfer paper storage means. After the incoming transfer paper is abutted against the resist roller 44 and stopped, the paper bending during the transfer of the transfer paper is corrected, and then the paper is re-feeded toward the transfer device 24 as transfer means, and the paper bending is corrected. The leading edge of the transferred transfer paper is detected by the paper detection sensor S1, and writing by the exposure optical system 30 serving as writing means is started after a predetermined time based on a signal detected by the paper detection sensor S1. FIG. 6 is a flowchart showing the writing method according to the present embodiment.
[0046]
With this configuration, the leading edge of the transfer sheet fed after correction of the paper bending is detected, so the leading edge detection accuracy of the transfer sheet is extremely high, and the transfer sheet is highly accurate even when many sheets are printed per hour. The image front end coincidence with the front end is obtained at the transfer position B.
[0047]
(Example 5)
  The image forming apparatus according to this embodiment transfers the toner image formed on the photosensitive drum 21, the exposure optical system 30 that is a writing unit for writing an image on the photosensitive drum 21, and the photosensitive drum 21 onto a transfer sheet. A transfer unit 24 serving as a transfer unit, a paper feed unit 41 serving as a transfer paper storage unit, and a transport unit that transports transfer paper from the paper feed unit 41 to the transfer unit 24 through the paper feed path 40, for example, a guide roller 43, And a writing control unit CPU (5) for controlling the writing of the exposure optical system 30, a paper detection sensor S1 is provided in the paper feed path 40, and the leading edge of the transfer paper conveyed by the conveyance means by the paper detection sensor S1 7 is a block diagram, and FIG. 8 is a flow chart. FIG. 7 is a block diagram. Shows the chart.
[0048]
By such a control method, transfer is performed by the transfer device 24 in a state where the leading edge of the image coincides with the leading edge of the transfer paper conveyed at the transfer position B.
[0049]
(Example 6)
  The present inventionThe image forming apparatus and the image forming method will be described. The transfer paper is conveyed by conveyance means for conveying the transfer paper, for example, the guide roller 43, the registration roller 44, and the pre-transfer roller 43a. These conveyance means nipping and conveying the transfer paper by a rubber roller that rotates oppositely. Things have been done. The roller is worn by long-term use, and the diameter of the roller is reduced to reduce the conveying ability. In the present invention, the roller diameter is set to 20 mm, but becomes 19.8 mm after 500,000 copies due to wear. In the present invention, correction is performed based on such empirical data, and image recording is performed in a form in which the leading edge of the transfer paper and the leading edge of the toner image are synchronized over a long period of time. The transfer speed V of the transfer paper is determined by the roller diameter D at the initial stage of printing.₀For example, after printing a large number of sheets over time, the roller diameter after printing 50,000 sheets is D₁(D₁<D₀), V (D₁/ D₀) In FIG. 2, the time required to transport the transfer paper for the distance (C−B) along the paper feed path 40 from the paper detection position C to the transfer position B is T in the initial stage of printing.₀= [Distance (C−B)] / V is T after 50,000 prints.₁= [Distance (CB)] / [V (D₁/ D₀)]. That is, the time T required for the transfer paper to move the distance (CB) in the initial stage of printing.₀The required time T after printing 50,000 sheets₁= T₀(D₀/ D₁) And T₁> T₀Are in a relationship.
[0050]
The time required for the transfer paper to move the distance (C−B) varies after a large number of sheets are printed as described above, but does not vary in the rotational peripheral speed of the photosensitive drum 21. That is, the time T required to rotate and move from the writing position A to the transfer position B by the exposure optical system 30._ABIs constant.
[0051]
Therefore, the time T (START) from when the leading edge of the transfer paper is detected by the paper detection sensor S1 to when writing by the exposure optical system 30 is started is T (START) = (T_AB-T₀) Is T (START) = (T_AB-T₁)
[0052]
  The present invention is based on the print test results of a large number of sheets, for example, T (START) (1-50000) for printing between 1 sheet and 50,000 sheets, and for printing between 50001 sheets and 100,000 sheets. T (START) (50001 to 100,000),100001T (START) (for printing between 1 and 150,000 sheets)100001(150,000) is prepared in a memory such as a ROM, while the image forming apparatus is provided with a counting means for counting the number of printed sheets. When the leading edge of the transfer paper is detected by the detection sensor S1, the writing control unit calls the time T (START) until writing starts for the number of prints from the data table, and waits for the time T (START) to elapse before the exposure optical system. Control to start writing by 30 is performed. FIG. 9 is a block diagram, and FIG. 10 is a flowchart.
[0053]
The writing control unit CPU (6) turns on the print button of the image forming apparatus (F1) to supply a transfer paper having a designated size among the paper feeding units 41 (A), 41 (B), and 41 (C). One transfer paper is carried out from the paper cassette (F2), and the transfer paper fed by the conveying means along the paper feed path 40 abuts against the temporarily stopped registration roller 44 to correct the paper bending (F3). After that, the paper is fed again toward the transfer unit 24, and when the leading edge of the transferred paper is detected by correcting the paper bending by the paper detection sensor S1 located on the downstream side of the registration roller 44 (F4), The write control unit CPU (6) calls the write timing table TT, and on the other hand, from the number of prints counted by the print number counting means PC, the print timing table TT concerned. Singled out timing corresponding to cement number (F5), carries out a set of appropriate timing picked (F6). When the paper detection sensor S1 detects the leading edge of the paper and checks whether or not the corresponding timing has passed (F7), writing by the exposure optical system 30 is started (F8).
[0054]
At the transfer position B, the toner image is transferred by the transfer unit 24 in such a manner that the front end of the toner image formed on the photosensitive drum 21 matches the front end position of the transfer paper to be transported (F9), and separated and transported. After fixing by the fixing device 50, the transfer paper is discharged onto the paper discharge tray 64 (F10).
[0055]
In the present embodiment, since the leading edge of the transfer sheet fed after correction of paper bending is performed, the detection accuracy of the leading edge of the transfer sheet is extremely high, and the performance fluctuates depending on the number of prints. Since the correction is performed, at the transfer position B, the image leading edge coincides with the leading edge of the transfer paper with high accuracy over a long period of time.
[0057]
(Example 7)
  There are cases where transfer sheets on which image recording has been performed are used as they are, and cases where a plurality of transfer sheets are bound and used in a book format. When the book format is used, a margin portion of ΔL = 10 mm is provided as a binding margin.
[0058]
In FIG. 2, when the transfer speed of the transfer paper transported at the same linear velocity as the peripheral speed of the photosensitive drum is V, the paper detection sensor S1 when there is no binding margin detects the leading edge of the transfer paper, and the writing means. The timing T until the exposure optical system 30 starts writing._AT_A= [Distance (CB) -distance (AB)] / V. The timing T from when the paper detection sensor S1 in the case of providing the binding margin ΔL detects the leading edge of the transfer paper until the exposure optical system 30 starts writing._BT_B= T_A+ (ΔL / V). That is, by delaying the writing start timing by ΔL / V, a margin portion for the binding margin ΔL range is provided on the transfer paper. The present invention provides timing T_A, T_BIs stored in a storage means such as a ROM, and the timing T is determined according to the presence or absence of the binding margin._AOr T_BIs controlled to start writing after the lapse of this timing, FIG. 11 is a block diagram, and FIG. 12 is a flowchart.
[0059]
In this embodiment, the selection is made by the binding margin presence / absence selection button BB provided on the operation table depending on whether printing with a binding margin is desired before printing or whether printing without a binding margin is desired (F11). Next, when the print button of the image forming apparatus is turned on (F12), the writing control unit CPU (7) feeds the transfer paper of the specified size among the paper feed units 41 (A), 41 (B), and 41 (C). A sheet of transfer paper is unloaded from the paper cassette (F13), and is fed along the paper feed path 40 by transport means such as a paper feed roller 43.
[0060]
A check is made as to whether or not the paper detection sensor S1 has detected the leading edge of the transfer paper along the paper feed path 40 (F14). When the leading edge of the paper is detected, the writing control unit CPU (7) determines the writing timing T when there is no binding margin by input from the binding margin selection button BB in F11._AIs set by calling (F16A). If there is a binding margin, write timing T_BIs set by calling (F16B). If there is no binding allowance, the paper detection sensor S1 detects the leading edge of the paper and the timing T_AWhen the timing elapses (F17), writing by the exposure optical system 30 is started, and when there is a binding margin, the paper detection sensor S1 detects the leading edge of the paper and the timing T is reached._BWhen the timing elapses (F17), writing by the exposure optical system 30 is started (F18).
[0061]
At the transfer position B, the toner image formed on the photosensitive drum 21 is transferred onto the transported transfer paper (F19). In this case, when there is no binding margin, transfer is performed with the leading edge of the toner image matching the leading edge of the transfer paper, and when there is a binding margin, the transfer is performed with a margin of ΔL remaining at the leading edge of the transfer sheet. After the transfer, the transfer paper is separated and transported, and after being fixed by the fixing device 50, the transfer paper is discharged onto the paper discharge tray 64 (F20).
[0062]
In this embodiment, when there is no binding margin, printing is performed with the leading edge of the image matching the leading edge of the transfer paper, and when there is a binding margin, the image is printed in a form in which a margin of a preset length is left at the leading edge of the transfer paper. Thus, an image forming apparatus that is extremely convenient to use is provided.
[0063]
【The invention's effect】
  Performance has fluctuated between the initial use and after printing a large number of sheets, and in the initial stage, the transfer paper tip and the tip of the toner image coincided with each other. Accordingly, there is provided an image forming apparatus and an image forming method capable of maintaining and forming an image in which a toner image coincides with the leading edge of a transfer paper with high accuracy.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.
FIG. 2 is a main part view of FIG. 1;
FIG. 3 is a block diagram of the first embodiment.
4 is a block diagram of Embodiment 2. FIG.
FIG. 5 is a block diagram of the third embodiment.
FIG. 6 is a flowchart according to the fourth embodiment.
FIG. 7 is a block diagram of the fifth embodiment.
FIG. 8 is a flowchart according to the fifth embodiment.
FIG. 9 is a block diagram of the sixth embodiment.
10 is a flowchart of Embodiment 6. FIG.
FIG. 11 is a block diagram of the seventh embodiment.
FIG. 12 is a flowchart according to the seventh embodiment.
[Explanation of symbols]
21 Photosensitive drum
22 Charger
23 Developer
24 Transfer device
25 Separator
30 Exposure optics
40 Paper feed path
41 Paper feed unit
43 Guide roller
44 Registration Roller
50 Fixing device
S1 Paper detection sensor

Claims (5)

Photoreceptor to form a latent image, said write No write unit writes an image on the photosensitive member, developing means for manually developed pre hexene image developer, a transfer sheet accommodating means, a developed image on the developed photosensitive body transcription means you transferred onto the transfer sheet, and conveying path for conveying the transfer sheet is housed in the transfer sheet housing means to a transfer position, the image forming apparatus having a registration roller provided in the conveyance path, the image Counting means for counting the number of sheets formed, a paper detection sensor for detecting the transfer paper between the transfer position transferred to the transfer paper by the transfer means and the registration roller, and writing based on the detection signal of the transfer paper by the paper detection sensor An image forming apparatus comprising: a writing control unit that controls a start timing to be changed based on a count of the number of image formations by the counting unit. The image forming apparatus according to claim 1, further comprising a predetermined table for determining the timing change. A photosensitive member for forming a latent image, a writing unit for writing an image on the photosensitive member, a developing unit for developing the latent image with a developer, a transfer paper storage unit, and a developed image on the developed photosensitive member on a transfer sheet. Image forming apparatus comprising: transfer means for transferring; transfer means for transferring transfer paper stored in transfer paper storage means to a transfer position through a transfer path; and registration rollers provided in the transfer path. In the method, the paper detection sensor for detecting the transfer paper between the transfer position transferred to the transfer paper by the transfer means and the registration roller, and the writing start timing based on the detection signal of the transfer paper by the paper detection sensor, An image forming method comprising: a writing control unit that performs control so as to correct and determine an error in a conveyance time during conveyance from the paper detection sensor to the transfer position. 4. The counting unit according to claim 3, further comprising: a counting unit that counts the number of image formations, wherein the writing control unit controls to change a writing start timing based on a count of the number of image formations by the counting unit. Image forming method. 5. The image forming method according to claim 4, further comprising a predetermined table for determining the timing change.

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