JP2003330334A - Image forming device and image forming control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device which not only always highly accurately adjusts an image position but also ensures a recording position accuracy that satisfies every user without requiring the user to check each output paper. <P>SOLUTION: An amount of displacement and an amount of oblique movement of paper transported to a paper feed path are detected by repeatedly reading the image pixels of CIS 204. In the case where at least either the detected amount of the displacement of paper or the detected amount of the oblique movement of the paper is greater than a first threshold of 5 mm, the image forming device determines that an error has occurred, and stops a printing operation before the paper reaches an image forming part (S106). On the contrary, in the case where at least either the detected amount of the displacement of the recording position of the paper or the detected amount of the oblique movement of the paper is equal to or less than the first threshold (5 mm) and greater than a second threshold of 2 mm, the device determines that an error which is not within a range permissible by a user has occurred. However, the device continues the printing operation. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus and an image forming control method such as an LBP (laser beam printer) and a copying machine using an electrophotographic technique.

[0002]

2. Description of the Related Art FIG. 16 is a view showing the arrangement of a print position adjusting mechanism in a conventional image forming apparatus. In the figure, 1
201 is a photosensitive drum for forming an image. 12
A laser 02 forms a latent image on the photosensitive drum 1201. Reference numeral 1203 is a registration clutch (registration roller) that determines the paper feed timing.

Reference numeral 1204 denotes a paper sensor for detecting the paper being conveyed, which is provided on the side opposite to the photosensitive drum 1201 with respect to the registration clutch 1203. Reference numeral 1205 denotes a deviation amount detection sensor for detecting the deviation amount of the lateral edge in the direction perpendicular to the sheet feeding direction. Further, 1206 indicates a sheet feeding direction. 1207 is an output sheet.

In the print position adjusting mechanism of the conventional image forming apparatus having the above structure, the control circuit (not shown) detects the deviation amount of the paper in the direction perpendicular to the paper feed direction by the deviation detection sensor 1205. , The paper sensor 120
The sheet position in the sheet feeding direction is detected by 4. further,
Based on the obtained information, the transfer timing of the image data to the laser control circuit (not shown) that drives the laser 1202 and the paper feed timing of the registration clutch 1203 are adjusted.

If a deviation amount of a predetermined value or more is detected, the positional accuracy of image recording on the paper is very poor.
The image forming apparatus was stopped as a jam.

[0006]

However, in the above-mentioned conventional image forming apparatus, the image position accuracy in the paper feed (conveyance) direction is determined mainly by the engagement time of the registration clutch. In particular, when performing high-speed printing, there is a problem that the image position accuracy deteriorates in proportion to the printing speed due to the connection time of the registration clutch.

Further, when high-speed printing is performed, there is a problem that the image position accuracy is deteriorated due to a detection deviation of a paper feed timing by a sensor, a mechanical mounting error of parts, durability, and the like.

On the other hand, even if the deviation amount is less than or equal to a predetermined value, the image recording accuracy is often not satisfied depending on the user who prioritizes the image recording position quality.
Therefore, in the conventional method, the user has to check the output paper one by one to check whether the image quality is satisfactory.

Therefore, according to the present invention, not only the paper feed timing can be detected with high accuracy, but also the deterioration of the image position accuracy due to the mounting error of the parts and the durability can be eliminated, and the image position can always be adjusted with high accuracy. It is an object of the present invention to provide an image forming apparatus and an image forming control method capable of obtaining a recording position accuracy that satisfies all users without checking the output sheets one by one.

[0010]

In order to achieve the above object, an image forming apparatus of the present invention is an image forming apparatus for forming an image on a sheet conveyed from a predetermined sheet storage section through a feeding path. , A plurality of read pixels for reading an image, and the plurality of read pixels are arranged in a direction perpendicular to the transport direction of the paper, the passage area of the transported paper, A sheet reading unit arranged, a shift amount detecting unit configured to detect a position shift amount of the conveyed sheet by repeatedly reading the plurality of read pixels of the sheet reading unit; and a predetermined first threshold value. And a second value which is smaller than the first threshold and is input
If the positional deviation amount of the sheet detected by the deviation amount detecting means and the setting means for setting the threshold value is larger than the first threshold value, it is determined that the conveyed sheet is an error, and the image forming operation is performed. The stopping means for stopping and the positional deviation amount of the sheet detected by the deviation amount detecting means are the first
If it is less than or equal to the threshold value of 1 and greater than the second threshold value, it is determined that the conveyed sheet is in error, and the image forming operation is continued without stopping.

Further, the sheet reading means is disposed between the image forming section and a registration roller for conveying the sheet to the image forming section at a predetermined timing.

Further, based on the input image data,
An image forming apparatus for forming an image by irradiating an image bearing member with a laser to form an electrostatic latent image, developing the electrostatic latent image, and transferring the electrostatic latent image onto a sheet, which is detected by the deviation amount detecting means. The laser writing start position in the direction perpendicular to the carrying direction is determined based on the amount of positional deviation of the sheet.

Further, it is characterized in that the amount of positional deviation of the sheet is a lateral shift amount and / or a skew amount in a direction perpendicular to the carrying direction.

Further, the first threshold value is a threshold value for the image forming apparatus to recognize the amount of positional deviation of the conveyed sheet as an error for structural reasons.

Further, the second threshold value is a threshold value for the user to recognize the deviation amount of the image with respect to the sheet as an error.

Further, when continuing the image forming operation without stopping the image forming operation, the continuation means cancels a part of the post-processing of the job being made, discharges the part of the paper, and executes the post-processing. After resetting, the image forming operation of the part of the sheets is started again.

Further, in the image forming control method of the image forming apparatus for forming an image on a sheet conveyed from a predetermined sheet storage section through the feeding path, the image forming control method has a plurality of reading pixels for reading the image. The image forming apparatus is provided with a sheet reading unit arranged in the feeding path, which is a passage area of the conveyed sheet, so that the reading pixels are arranged in a direction perpendicular to the sheet conveying direction. A deviation amount detecting step of detecting a positional deviation amount of the conveyed paper by repeatedly reading out the plurality of read pixels of the paper reading unit, a first threshold value determined in advance, and the first threshold value. If the value is a small value and the positional deviation amount of the sheet detected in the setting step of setting the input second threshold value and the deviation amount detection step is larger than the first threshold value, the sheet is conveyed. The paper is And a stop step of stopping the image forming operation and the positional deviation amount of the sheet detected in the deviation amount detecting step is equal to or less than the first threshold value and larger than the second threshold value, And a continuation step of continuing the image forming operation without stopping the image forming operation.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an image forming apparatus and an image forming control method of the present invention will be described with reference to the drawings.

[Overall Configuration] FIG. 1 is a diagram showing a configuration of an image forming apparatus according to an embodiment. The image forming apparatus includes an image forming apparatus main body 10, a folding device 40, and a finisher 50. In addition, the image forming apparatus main body 1
Reference numeral 0 is composed of an image reader 11 for reading a document image and a printer 13.

The image reader 11 includes a document feeder 1
2 is installed. The document feeder 12 feeds the documents set upward on the document tray 12a one by one in the left direction in the figure from the first page, and conveys them onto the platen glass through a curved path to a predetermined position. The original is read by stopping at the position and scanning the scanner unit 21 from the left side to the right side in this state. After reading, the document is discharged toward the external discharge tray 12b.

The reading surface of the original is the scanner unit 21.
The reflected light from the document is guided to the lens 25 via the mirrors 22, 23 and 24. The light that has passed through the lens 25 is the image sensor 2
An image is formed on the image pickup surface of 6.

While the image of the original is read line by line in the main scanning direction by the image sensor 26, the scanner unit 21 is conveyed in the sub scanning direction to read the entire image of the original. The optically read image is converted into image data by the image sensor 26 and output. The image data output from the image sensor 26 is subjected to predetermined processing in an image signal control unit (image processing circuit) (not shown), and then input as a video signal to an exposure control unit (laser control circuit) (not shown) of the printer 13. To do.

The exposure controller of the printer 13 modulates the laser light output from the laser element (not shown) based on the input image data, and the modulated laser light is scanned by the polygon mirror 27. , Lens 28,
It is irradiated onto the photosensitive drum 31 via 29 and the mirror 30.

An electrostatic latent image corresponding to the scanned laser beam is formed on the photosensitive drum 31. The electrostatic latent image on the photosensitive drum 31 is visualized as a developer image by the developer supplied from the developing device 33. In addition, at the timing synchronized with the start of laser light irradiation, each of the cassettes 34, 3
Sheets are fed from 5, 36, 37, the manual feed section 38, or the double-sided conveyance path, and conveyed to the image forming section via the registration rollers 43.

This paper is composed of the photosensitive drum 31 and the transfer roller 3.
The developer image formed on the photosensitive drum 31 by being conveyed to and from the transfer roller 9 is transferred onto the paper fed by the transfer roller 39. The sheet on which the developer image has been transferred is conveyed to the fixing unit 32, and the fixing unit 32 fixes the developer image on the sheet by heat-pressing the sheet. The paper that has passed through the fixing unit 32 is
The paper is ejected from the printer 13 to the outside (folding device 40) via the flapper and the ejection roller.

Here, when the sheet is ejected with its image forming surface facing downward (face down state),
The sheet that has passed through the fixing unit 32 is temporarily guided into the reversing path 42 by the flapper switching operation, and after the trailing edge of the sheet has passed the flapper, the sheet is switched back and discharged from the printer 13 by the discharge roller.

When a hard paper such as OHP paper is fed from the manual paper feed unit 38 and an image is formed on this paper,
The sheet is discharged by the discharge roller with the image forming surface facing upward (face-up state) without guiding the sheet to the reverse path.

Further, when double-sided recording for forming images on both sides of the sheet is set, the unrecorded sheet is guided to the reversing path 42 by the flapper switching operation and then conveyed to the double-sided conveying path. The paper led to the double-sided transport path
The sheet is conveyed to the position where it is nipped by the double-sided conveyance roller 41 via the double-sided conveyance roller 40, and is temporarily stopped until the next sheet feeding timing. If there is already a sheet to be stopped at the position nipping the double-sided conveyance roller 41 in the double-sided conveyance path, the sheet is stopped at the position nipped to the double-sided conveyance roller 40 located upstream of the double-sided conveyance roller 41.

Here, when the cassette 35 is used in the double-sided conveyance path even when there is no sheet to stop at the position nipped by the double-sided conveyance roller 41, the sheet is conveyed to the position nipped by the conveyance roller 40, Stop the paper.

Then, after being fed from the cassette and conveyed to the image forming section, the single-side printed sheet nipped by the double-sided conveyance roller 41 is re-fed. afterwards,
Single-sided paper feeding When the printed paper is conveyed to the image forming unit, the paper is fed from the cassette. Double-sided recording is performed by alternate sheet feeding in which the above operation is repeated. At this time, up to two sheets of paper are retained in the double-sided conveyance path.

The sheet discharged from the printer 13 is sent to the folding device 40. The folding device 40 performs a process of folding a sheet into a Z shape. For example, when A3 size or B4 size paper and the folding process is designated, the folding device 40 performs the folding process, and in other cases, the paper discharged from the printer 13 passes through the folding device 40. It is sent to the finisher 50. The finisher 50 is provided with an inserter 90 for feeding a special sheet such as a cover sheet or a slip sheet to be inserted into a sheet on which an image is formed. The finisher 50 performs various processes such as bookbinding, binding, and punching. Here, the photosensitive drum is used as the image carrier of the image forming apparatus, but a photosensitive belt may be used. Further, the image forming apparatus includes an operation panel 6
0 is provided.

FIG. 13 is a view showing the arrangement of the operation panel 60 provided in the image forming apparatus. In the figure, reference numeral 400 is a copy start key for instructing the start of copying. 401
Is a reset key for returning to the standard mode. 402
Is a guidance key to be pressed when using the guidance function. Reference numeral 403 is a ten-key pad for inputting numerical values such as the set number of sheets. A clear key 404 clears numerical values. A stop key 405 stops copying during continuous copying. Reference numeral 406 denotes a liquid crystal display unit and a touch panel for displaying the setting of each mode and the status of the printer.

Reference numeral 407 is an interrupt key for interrupting a continuous copy or during use as a fax machine or printer to make an emergency copy. Reference numeral 408 is a personal identification key for managing the number of copies by individual or department. Reference numeral 409 denotes a soft switch for turning on / off the power of the image forming apparatus main body. A function key 410 is used when changing the function of the image forming apparatus. Reference numeral 411 denotes a user mode key for entering a user mode in which the user sets items in advance, such as ON / OFF of the automatic cassette change, change of set time until entering the energy saving mode, and allowable values of lateral deviation amount and skew amount. Is.

[Paper feeding timing and image writing timing] FIG. 2 is a diagram showing a print position adjusting mechanism arranged in a paper conveying path to the photosensitive drum. In the figure, 205
Is a paper transport path. Reference numeral 206 denotes a circulation path for double-sided recording. Reference numeral 31 is the photosensitive drum described above. A laser element 202 forms a latent image on the photosensitive drum 31. The layout of the laser element 202 is drawn for convenience, and differs from the actual layout. Reference numeral 203 denotes a paper carrying roller (registration roller), which temporarily holds the paper sent along the paper carrying path 205 in an abutting state, and then sends it to the photosensitive drum 31 side at a predetermined paper feeding timing. .

An image reading sensor (image sensor) 204 reads an image to detect the position of the sheet, and C
It is composed of a photoelectric conversion element array such as CD or CIS.
In this embodiment, a CIS (contact image sensor) is used. The CIS 204 is arranged on the registration roller 203 side, which is separated from the photosensitive drum 31 by a distance L1. Further, the CIS 204 is a registration roller 203 separated from an image forming point (point a) described later by a distance L2.
It is located on the side. Further, the CIS 204 is arranged at a distance L3 from the BD detector 108, which will be described later, in the direction perpendicular to the paper feeding direction.

Reference numeral 108 denotes a laser element (simply called a laser)
Beam detect (BD) to detect irradiation time of 202
It is a detector. The laser light is reflected by the polygon mirror B
After being irradiated on the D detector 108, the D detector 108 is shaken and is shaken.
When it is irradiated onto the photosensitive drum 1, a latent image is formed on the photosensitive drum 31.

In the figure, point a indicates an image forming point. For example, when the paper is 5 mm past point a, the laser 2
When the image formation by 02 is performed, the rotation of the photosensitive drum 31 and the conveyance of the sheet 107 are performed in synchronization, and as a result,
The output image is formed at a position 5 mm from the leading edge of the paper.

In the figure, point b indicates a transfer point,
Point c indicates a laser writing point. At the laser writing point c, the photosensitive drum 31 is moved by the laser 102.
When the latent image is formed on the toner, the toner is transferred onto the paper at the transfer point b via the developing unit, and the image is formed.

During this image formation, the registration roller 203
The sheet 107 sent out from is conveyed to the photosensitive drum 31 side along the sheet conveying path 205, and is controlled to irradiate the photosensitive drum 31 with a laser beam when the distance L2 has passed after the leading edge is detected by the CIS 204. Is done. Specifically, the timer counts the time when the paper 107 travels the distance L2, and when the time elapses, the photosensitive drum 31 is irradiated with laser light.

In order to adjust the laser writing position with higher accuracy, the timing of the paper feed direction of the paper (for convenience, referred to as the sub-scanning direction) and the direction perpendicular to this paper feed direction (for convenience, referred to as the main scanning direction). ) Timing, and it is necessary to control writing by laser light according to this detection information.

That is, the start time of image formation is determined after the leading edge position of the paper is detected by the CIS 204, and the writing by the laser is started when the paper advances by the distance L2, thereby writing the image in the sub-scanning direction. The position can be adjusted. Therefore, the distance L2 is CIS20.
4 detects the deviation in the direction perpendicular to the paper feed direction after detecting the leading edge of the paper 107, and sets a distance corresponding to the time from setting the timing of writing the laser light in each direction. It is necessary to have at least.

Further, in an ordinary image forming apparatus, the sheet conveyance speed and the rotation speed of the photosensitive drum 31 are set to be equal. This is because the transfer roller 39 is moved from a position (image forming point a) which is advanced from the CIS 204 by a distance L2.
And the distance L1-L2 to the transfer position (transfer point b) on the paper, which is the nip position of the photosensitive drum 31, and the transfer position (transfer point b) from the laser writing position (writing point c) to the paper. Means that the circumference (circulation) distance on the photosensitive drum 31 is equal to.

When the lateral edge position (horizontal registration) of the sheet is detected by the CIS 204, the beam detector (BD)
At a distance L3 from 108 to the lower end of CIS 204, CI
The distance (x + L3) is calculated by adding the distance x from the lower edge of S204 to the lateral edge position of the paper, and the beam detector 108
After the laser light is detected by the method, the laser light is shaken in the main scanning direction by the calculated distance, and then the writing by the laser is started, whereby the writing position of the image in the main scanning direction can be adjusted.

The timing control unit (TCU) 105, which will be described later, adjusts the writing position of the image in the sub-scanning direction and the main-scanning direction by the laser light. That is, the TCU 105 turns on the registration roller 203 to start the conveyance of the sheet, and then the CCU
The writing start timing is output to the laser control circuit 27 based on the detection signal from the IS 204. Laser control circuit 2
Reference numeral 7 drives the laser element 202 in synchronization with the writing timing output from the TCU 105, based on the image data sent from the image processing circuit (not shown).

[CIS Configuration] FIG. 3 is a diagram showing the configuration of the CIS 204. The CIS 204 is the image reading unit 2
05 and the LED light emitting section 206. The image reading unit 205 includes a plurality of chips (1 to n) 211 to 2 in which a light receiving element unit and a shift register are housed in one chip.
17, the selector 215 and the output unit 216. In this embodiment, the number of chips is 7 (n =
7). Each light receiving element in each chip has 1000
Reading pixels are provided.

Of the 7,000 effective pixels to be read in the entire CIS, the chip (1) 2 located at the beginning is read for reading in the sub-scanning direction (leading edge and skew detection which will be described later).
1000 read pixels in 11 are used. On the other hand, for reading in the main scanning direction (lateral edge detection described later),
6000 in the remaining 6 chips (2-6) 212-216
Read pixels are used. Note that the total number of effective pixels of the plurality of chips is an example, and is not particularly limited and may be any number. Also, chip division,
The number of divisions is not limited to 1: (n-1) in this embodiment, and may be any number.

In the image reading unit 205, the selector 215 uses the selector signal from the TCU 105 to cause the selector 215 to select a specific chip, for example, the chip 21 used for detecting the leading edge and the skew feeding.
When only 1 is effectively selected, the image signal detected by the light receiving element portion 211a is the load signal (C
After being read by the shift register 211b once by IS-SH), the clock (CL
According to K), they are sequentially transferred from the shift register 211b to the output unit 216 via the selector 215. Output part 2
Reference numeral 16 converts the transferred serial image signal into parallel data and outputs it as CIS data.

Further, the selector 2 is used by the selector signal from the TCU 105 to select the chip 2 which is used for lateral edge detection.
When 12 to 217 are effectively selected, each light receiving element section 212
The image signals detected by a to 217a are temporarily stored in the shift register 212b by the load signal from the TCU 105.
To 217b, the shift register 212b is sequentially read according to the clock (CLK) from the TCU 105.
˜217b to the output unit 216 via the selector 215. The output unit 216 converts the transferred serial image signal into parallel data and outputs it as CIS data.

On the other hand, the LED light emitting section 206 includes an LED section 22 in which a plurality of LED groups connected in series are connected in parallel.
1 and connected to the cathode side of each LED group, each LE
LED current adjustment circuit 222 that adjusts the current flowing through the D group
Composed of. The LED current adjustment circuit 222 is a TCU.
According to the light amount control data from 105, the LED unit 2
The total LED light emission of 21 is adjusted.

FIG. 4 is a timing chart showing changes in the clock (CLK) of the CIS 204, the load signal (CIS-SH) and the image signal when the leading edge detection, the skew feeding detection and the lateral edge detection are performed. In the case of tip detection and skew detection (A and C in the figure), the light receiving element section 211a used is 1
This is for the chip, and the charge accumulation time repeatedly read by the load signal becomes short. In this case, TCU105
According to the light amount control data from the LED current adjusting circuit 2
By setting the LED current value by 22 to be high and increasing the LED light emission amount, a decrease in the S / N ratio of the read image is prevented. On the other hand, in the case of the lateral edge detection (B in the figure), the number of light receiving element portions 212a to 217a used is 6, and the charge accumulation time repeatedly read by the load signal becomes relatively long.

In this case, according to the light quantity control data from the TCU 105, the LED by the LED current adjusting circuit 222
The S / N ratio of the read image can be maintained even if the current value is set low and the LED emission amount is reduced.

FIG. 5 shows the CIS 20 for the paper passage area.
It is a figure which shows arrangement | positioning of No. 4. CIS 204 is paper 107
The reading pixels are arranged so as to be perpendicular to the transport direction of. In addition, one end of the CIS 204 is located at a substantially central position of the paper 107 passing therethrough, and the other end is located at a position beyond the lateral edge of the paper 107 passing therethrough.
Is placed. The chip (1) 211 is located on the substantially center side of the sheet 107 of the CIS 204, and the chip (7) 217 is located on the side beyond the lateral edge.

FIG. 6 is a diagram showing the leading edge detection area and the lateral edge detection area in the CIS 204. As described above, the leading edge (skew) detection area is included in the light receiving element portion 211a in the CIS 204 located substantially on the center side of the sheet 107.
Corresponding to 000 pixels, the remaining read pixels in the CIS are not used while the leading edge (skew) is being detected (indicated by x in the figure). On the other hand, the lateral edge detection area is CIS204.
6 included in the remaining light receiving element portions 212a to 217a
This corresponds to 000 pixels, and 1000 pixels of the light receiving element portion 211a used for tip detection are not used during horizontal edge detection (indicated by x in the figure).

In this way, for the leading edge detection and the lateral edge detection, processing is performed so as to fetch only the necessary pixel data of the read pixels of the CIS 204, which are suitable for the respective detections, and as much data as is unnecessary for each detection is obtained. I try not to capture it.

FIG. 7 is a diagram showing the maximum detection width of the CIS 204. The maximum paper width used in the image forming apparatus is Lma
x and the minimum paper width is Lmin, the maximum detection width X
Is approximately 1/2 (Lmax-Lmin), and it can be seen that the CIS 204 having such a maximum detection width X may be used.

Here, the usefulness when the CIS is used for the tip (oblique) detection will be described. For example, the paper feed speed (P
S) is 800 mm / S, maximum detection width (X) is 100 m
m, main scanning / sub scanning resolution Ph and Pv are each 0.0
When set to 5 mm, the reading cycle of one sensor line = P
S / Pv = 16 KHz, sensor pixel number = X / Ph = 20
It becomes 00 dots, and VC is
LK = 16 KHz * 2000 dot = 32 MHz. That is, a sensor capable of operating at 32 MHz is required.

However, in the method shown in this embodiment, VCLK = 16 KHz by temporarily setting the number of pixels used for reading in the sub-scanning direction to 1/10 of 200 dots.
* 200dot = 3.2MHz. That is, 3.2
A sensor operable at MHz can be used, and an inexpensive CIS can be adopted. Further, in the reading in the main scanning direction, since the clock VCLK is set to 3.2 MHz, it can be detected only once while the distance of 10 lines advances, but it may be delayed because it is the lateral edge detection.

Further, since a plurality of pixels are used in the main scanning direction as the pixel data used for the leading edge detection and the skew detection, as compared with the conventional single optical sensor or mechanical paper detection sensor, Since the sensor for detecting the leading edge is not required, the image forming apparatus can be made more compact by reducing the number of parts.

Then, by performing the lateral edge detection after the detection of the leading edge detection and the skew feeding detection, different methods can be adopted as the respective detection methods, and the detection accuracy is improved by the adoption of the detection methods suitable for the respective detections. It becomes possible to do.

In particular, in the leading edge detection, utilizing the data of a part of a plurality of pixels in the main scanning direction contributes to the improvement of the detection accuracy. This is because the reading cycle is shorter and the pixel data density in the paper transport direction is higher than in the case where a plurality of all pixels are read with the same reading clock, and as a result, the detection accuracy is improved.

In the sequence, although the leading edge of the sheet is first detected by the CIS, if the leading edge detection and the lateral edge detection are simultaneously performed without first processing the leading edge of the sheet, the lateral edge is detected. For this reason, it is necessary to read a plurality of all pixels of the CIS, and the cycle of tip detection becomes long, so accurate tip detection cannot be performed. Therefore, processing in the order of detecting the lateral edge after detecting the leading edge (detecting the skew feeding) enables more accurate leading edge detection.

Further, by separately performing the leading edge detection and the lateral edge detection, the detection processing can be set to the shortest time at each optimal detection cycle, so that the conveyance distance corresponding to the distance between the registration roller and the image forming section is shortened. Therefore, the device can be made compact.

[Structure of Control Circuit] FIG. 8 is a block diagram showing the structure of the control circuit. The control circuit 51 has an image processing circuit 52, a laser control circuit (V-CNT) 27, and a timing control unit (TCU) 105.
The image processing circuit 52 stores an image memory (P-M) in which image data read by the image sensor 26 is stored.
An EM) 56 and a CPU 57 for processing the image data stored in the image memory 56 are provided.

The laser control circuit 27 includes an image processing circuit 52.
A drive signal is output to the laser element 202 on the basis of a signal output in accordance with the image data. The drive signal is output to the laser element 202 in synchronization with the timing signal from the TCU 105. TCU105 is CIS204
The CIS control signal is output to, and the CIS data read by the CIS 204 is input, and a timing signal is output to the laser control circuit 27 based on the CIS data. This timing signal includes the vertical synchronization signal VSY.
NC, clock VCLK, horizontal sync signal HSYNC, a laser writing signal, a signal for driving the registration roller 203 (registration ON signal), and the like are included.

FIG. 9 is a block diagram showing the structure of the TCU 105. The TCU 105 has a counter (count).
r) 61, registration ON section 62, leading edge detecting section 63, lateral edge detecting section 64, CIS controller 65, CIS leading edge detecting short cycle setting section 66, leading edge error detecting section 67, CIS lateral edge detecting long cycle setting section 68. A side edge error detection unit 69, a sequence end setting unit (SEQ END) 70, and a correction parameter storage unit 71.

The counter 61 is activated by a sequence start signal (SEQ START) and counts clocks having a constant cycle. Cash register ON section 62
Turns on / off the driving of the registration roller 203.
The tip detection unit 63 uses the CIS input from the CIS 204.
The leading edge position of the paper is detected based on the data. The lateral edge detection unit 64 similarly detects the lateral edge position of the sheet based on the CIS data input from the CIS 204.

The CIS controller 65 uses the CIS204
In contrast, load signal (CIS-SH), clock (CI
S-CLK), selector signal, light quantity control data, etc.
Output the S control signal. In the CIS front end detection short cycle setting unit 66, a short cycle TS of the load signal (CIS-SH) input to the CIS 204 when the front end of the sheet is detected is set. On the other hand, in the CIS lateral edge detection long cycle setting unit 68, the long cycle TL of the load signal (CIS-SH) input to the CIS 204 is set when lateral edge detection of the paper is performed. In the present embodiment, this long cycle TL is 6 of the short cycle TS.
It's twice as long.

The leading edge error detecting section 67 includes a leading edge detecting section 63.
If the leading edge position of the paper detected by the outside of the predetermined range (5 mm), the error signal (ER
R) is generated. Similarly, when the lateral edge position of the sheet detected by the lateral edge detecting section 64 is out of the predetermined range (5 mm), the lateral edge error detecting section 69 outputs an error signal (ERR).
To generate. In the sequence end setting unit 70, the count value of the sequence for ending the printing of one sheet is set. The correction parameter storage unit 71 stores the correction values of the laser writing position in the main scanning and sub-scanning directions obtained by the process described later.

FIG. 10 is a block diagram showing the structure of the leading edge detecting portion 63. The leading edge detection unit 63 has a plurality of edge circuits (EDDGE) 81, a timing generation circuit 82, a counter 83, and a skew feed amount setting unit 84. Each edge circuit (EDDGE) 81 includes a light receiving element portion 2 of the CIS 204.
A register signal (REG1 that specifies the pixel position in 11a)
~ REGn) is input together with the CIS data. Then, when "paper out → paper is present" is detected at the pixel position designated in synchronization with the count signal from the counter 83, the edge circuit (EDDGE) 81 thereof detects an edge (EDDGE).
1-n) generate signals.

Timing generation circuit (TIMING) 82
Averages the generated plurality of edge (EDDGE1 to n) signals and outputs a leading edge detection signal (VREQ), and outputs the generated plurality of edges (EDDG).
E1 to n) signal is used to detect the skew feeding amount, and the detected skew feeding amount is larger than the skew feeding amount (REG: 5 mm) preset in the skew feeding amount setting unit 84. , And outputs a skew error signal (skew ERR). Further, when the tip is detected, only a specific pixel may be used, but in the present embodiment, the influence of noise or the like is removed by using a plurality of pixels. Further, since a plurality of pixels are used in the tip detection, the tip detection accuracy is further improved as compared with the conventional single optical sensor or mechanical sensor.

The counter 83 has a load signal (CIS-S
H) and the clock (CIS-CLK), the count signal is output to the plurality of edge circuits (EDDGE) 81.

Since the skew feeding amount of the paper is detected based on the data representing the leading edge of the paper read from the plurality of read pixels by the leading edge detecting means, the skew feeding amount of the paper is calculated and the leading edge position of the paper is detected. They can be executed simultaneously and the processing time can be shortened.

Therefore, the skew feeding can be accurately detected before the image is formed on the sheet, and it is not necessary to output the sheet on which the image of low print quality is formed due to the skew feeding.

[Paper Feed / Image Forming Sequence] FIG. 11 is a timing chart showing the operation of the TCU 105.
The sheet 107 is conveyed to the registration roller 203 along the sheet conveyance path 205, and the registration roller 203 causes the sheet 10 to be conveyed.
The sheet feeding / image forming sequence of the present embodiment starts in the state where 7 is retained. Sequence start signal (S
(EQ START) is input to the counter 61, the counter 61 starts measuring a clock with a constant cycle. When the count value of the counter 61 reaches the timing a, the cash register O
The N section 62 sets the registration signal to the H level and the registration roller 2
Drive 03 on.

Then, when the count value reaches the timing b, the operation of the leading edge detection mode in the CIS 204 is started. In the leading edge detection mode, the TCU 105 outputs a load signal (CIS-SH) to the CIS 204 at the short cycle TS set in the CIS leading edge detection short cycle setting unit 66. As a result, the tip detection unit 63 reads only the CIS data from the light receiving element unit 211a in the CIS 204.

When the leading edge of the sheet is detected when the count value reaches the timing c, the leading edge detection section 63 outputs the leading edge detection signal VREQ to the CIS controller 65 and starts the operation of the CIS 204 in the lateral edge detection mode. Let CIS controller 65 detects the tip detection signal VR
When the vertical synchronizing signal VSYNC corresponding to the EQ is output to the laser control circuit 27, the laser controlling circuit 27 takes the vertical margin into consideration based on the vertical synchronizing signal VSYNC from the CIS controller 65 and writes the position in the sub-scanning direction by the laser. Adjust. FIG. 12 is a diagram showing the writing start position adjustment by the laser. The count value is the timing c '(c'
If the leading edge position of the sheet is not detected even when the condition of &gt; c is reached, the CIS controller 65 outputs a leading edge error signal (leading edge ERR).

In the lateral edge detection mode, the TCU 105
Long cycle TL set in the S horizontal edge detection short cycle setting unit 68
Outputs a load signal (CIS-SH). As a result, the lateral edge detection unit 64 reads only the CIS data from the light receiving element units 212a to 217a in the specific area within the CIS 204.

When the lateral edge position of the paper is detected when the count value reaches the timing d, the CIS controller 6
5 stops the operation of the CIS 204, and the horizontal synchronization signal H
The SYNC and the clock VCLK are supplied to the laser control circuit 27.
Output to. The laser control circuit 27 uses the horizontal synchronization signal HS.
Based on YNC and the clock VCLK, the write start position by the laser in the main scanning direction is set (see FIG. 12).
Even if the count value reaches the timing d '(5 mm), if the lateral edge position is not detected, the lateral edge error signal (lateral edge ERR) is output.

[Skew Error, Horizontal Edge Error Sequence] Assuming that there are two skew errors in this embodiment, the error level is set according to each. Similarly, two lateral edge errors are assumed, and the error level is set according to each.

One of the errors is an error due to the configuration of the image forming apparatus, and the error level is determined in advance so that the image forming apparatus recognizes the positional deviation amount of the conveyed sheet as an error. It is a threshold.

For example, in the present embodiment, when the recording sheet is laterally displaced or skewed by 5 mm or more with respect to the regular conveyance,
Since the edge of the sheet collides with the edge of the transport path, the sheet may be bent or may be folded at the corner. For this reason, the paper is jammed in an unfavorable place, or the paper does not normally pass through the image forming portion, which adversely affects the process unit such as the photoconductor. Therefore, if there is a horizontal misalignment or skew of 5 mm or more, it is desirable to make an error at the time of detection, and in this embodiment, the paper is stopped before reaching the photoconductor.

Another error is an error when the lateral deviation or skew of the recording paper is not within the user's allowable range.
The error level is a permissible value (threshold value) input by the user because the user recognizes the amount of deviation of the image with respect to the sheet as an error.

In this embodiment, the range in which the lateral deviation can be corrected by the writing timing of the laser in the main scanning direction is
It is about 2 mm. This is because the size of the allowable range for image formation with respect to the lateral deviation of the photoconductor itself or the process unit is 2 mm. Therefore, when the lateral deviation of the paper is in the range of 0 mm to 2 mm, the positional deviation of the image on the paper does not occur, but in the case of the lateral deviation of the paper of 2 mm to 5 mm, the paper is 0 mm to 3 mm. The upper image appears as a positional deviation (recording positional deviation) on the recording paper. As a result, the user sets an arbitrary allowable range for the actual image position shift amount of 0 mm to 3 mm,
It is possible to record an image without causing the user to feel lateral displacement.

Similarly, for skew, the image recording position may be corrected by the laser writing timing.
By setting the user's allowable value for the amount of skew feeding, it is possible to record an image without causing the user to feel skew shift.

FIG. 14 is a diagram showing a user setting screen for setting the allowable values of the lateral deviation amount and the skew amount. FIG.
When the user mode key 411 of is set, the user
Allowable values for the amount of lateral deviation and the amount of skew can be set. On this screen, the user sets the allowable values of the lateral shift amount (0 mm to 3 mm) and the skew feeding amount (0 mm to 5 mm) by numerically inputting the numeric keys on the operation unit. The horizontal displacement amount (0 mm to 3 mm) displayed on this screen represents the recording position displacement amount described above.

FIG. 15 is a flow chart showing the procedure for detecting a lateral edge error and a skew error. This flowchart is stored as a program in the ROM in the image forming apparatus, and is executed by the CPU that controls the image forming apparatus. When the power of the image forming apparatus is turned on, first, it is determined whether or not the user mode key 411 is pressed, that is, whether or not the mode is shifted to the user set value input mode regarding the allowable values of the lateral deviation amount and the skew amount. (Step S10
1).

If the user mode key 411 is not pressed and the mode does not shift to the user setting value input mode, the process directly proceeds to step S103. If the user does not input the setting value, the initial value (for example, 1.5 mm) is set. On the other hand, when the user mode key 411 is pressed to shift to the user set value input mode, the input of the set value is waited, and if there is an input, the set value input as the allowable value of the lateral deviation amount / skew amount is registered. (Step S102). In the present embodiment, the set values are the lateral shift amount on the screen, that is, the recording position shift amount 2.0 mm and the skew feed amount 2.0 mm (see FIG. 14).

Then, the system waits for a copy, FAX, or printer job to be input (step S103).
When the job is input, the image forming operation is started (step S104). Paper fed from the paper cassette or double-sided path to the image forming unit has a lateral displacement of 5 mm (first threshold)
It is determined whether or not the following (step S105). As described above, this error level is set in advance for the image forming apparatus to judge an error as a structural reason. If the amount of lateral deviation exceeds 5 mm, an error code corresponding to a paper transport error or a message equivalent thereto is displayed on the operation unit of the image forming apparatus, and the recording sheet is immediately stopped so that the recording sheet does not reach the image forming unit. The printing operation is stopped (step S106). After that, the processing is ended.

On the other hand, when the lateral shift amount is 5 mm or less,
It is determined whether or not the skew amount is 5 mm (first threshold value) or less (step S107). If the skew amount exceeds 5 mm, as in the case of the lateral shift amount, an error code corresponding to a paper transport error is displayed on the operation unit of the image forming apparatus in step S106, and the printing operation is stopped. On the other hand, when the skew amount is 5 mm or less in step S107, the recording position shift amount on the paper is 2 mm (the lateral shift amount is 4 mm).
It is determined whether or not (second threshold value) or less (step S108). As described above, this error level is set to determine an error that the error level is not within the range allowed by the user.

When the recording position deviation amount on the sheet exceeds 2 mm, the recording sheet has a recording abnormality, but since there is no problem in the printing operation itself of the image forming apparatus, the image forming operation is continued. In this case, staple the job
If an operation such as folding or punching is specified, it is canceled (step S109). Then, step S10
Return to the processing of 5. In the processing of step S109, when the sheets are retained in the staple processing tray of the finisher for stapling, the retained sheets are discharged to the stack tray. In addition, identify the error paper,
The error paper is ejected to the processing tray, and the slip sheet is ejected on the error tray so that an incomplete part of a plurality of copies in the print job can be identified. If the finisher has a shift paper discharge function, the discharge destination of the error paper may be shifted without discharging the slip sheet. After the error paper has been ejected, to create a new complete part again,
Printing is started from the first page, and post-processing such as stapling is reset.

On the other hand, in step S108, the recording position deviation amount on the paper is 2 mm or less (horizontal deviation amount is 4 mm or less).
If it is, it is determined whether or not the skew amount is 2 mm (second threshold value) or less (step S110). The amount of skew is 2 m
If it exceeds m, similar processing is performed in step S109. On the other hand, if the skew amount is 2 mm or less in step S110, it is determined whether or not the job is completed after the printing is completed and the paper is ejected (step S111). If the job is in progress, the process returns to step S105 to continue the operation for each recording sheet. On the other hand, when the job is completed, the process returns to step S101.

The above is the description of the embodiments of the present invention, but the present invention is not limited to the configurations of these embodiments, and the functions shown in the claims or the configurations of the embodiments are not limited thereto. Any structure can be applied as long as it can achieve the function it has.

For example, in the above-described embodiment, the user setting regarding the allowable values of the lateral deviation amount and the skew amount is performed by the operation unit (operation panel) of the image forming apparatus, but may be performed by the printer driver. . Further, in the present embodiment, the write timing is not corrected for skew, but some correction may be performed.

Further, in the above-described embodiment, when either one of the lateral deviation amount and the skew feeding amount is larger than the first threshold value, it is determined that an error has occurred, and the image forming operation is stopped.
If it is less than or equal to the first threshold value and greater than the second threshold value, it is determined that an error has occurred, but the image forming operation is continued, but both the lateral deviation amount and the skew amount satisfy the above conditions. If so, the same processing may be performed.

[0095]

According to the present invention, even in high-speed printing,
Not only can the paper feed timing be detected with high accuracy, deterioration of the image position accuracy can be eliminated and the image position can be adjusted with high accuracy, but the user has set an allowable value for the image recording position accuracy. It is possible to record an image that does not cause the recording position shift.

That is, since the user is allowed to input the allowable value (second threshold value) of the recording position accuracy and the image formation is performed based on the allowable value, all the output papers are checked without checking each one. It is possible to obtain the recording position accuracy which is satisfied by the user.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an image forming apparatus according to an embodiment.

FIG. 2 is a diagram showing a print position adjusting mechanism arranged in a paper conveyance path leading to a photosensitive drum.

FIG. 3 is a diagram showing a configuration of a CIS 204.

FIG. 4 is a clock (CLK) and load signal (CI) of the CIS 204 at the time of performing leading edge detection, skew feeding detection, and lateral edge detection.
5 is a timing chart showing changes in (S-SH) and image signals.

FIG. 5 is a diagram showing an arrangement of the CIS 204 with respect to a paper passage area.

FIG. 6 is a diagram showing a leading edge detection area and a lateral edge detection area in the CIS 204.

FIG. 7 is a diagram showing the maximum detection width of the CIS 204.

FIG. 8 is a block diagram showing a configuration of a control circuit.

9 is a block diagram showing a configuration of TCU 105. FIG.

FIG. 10 is a block diagram showing a configuration of a tip detection unit 63.

FIG. 11 is a timing chart showing the operation of the TCU 105.

FIG. 12 is a diagram showing a writing start position adjustment by a laser.

FIG. 13 is a diagram showing a configuration of an operation panel 60 provided in the image forming apparatus.

FIG. 14 is a diagram showing a user setting screen for setting allowable values of a lateral shift amount and a skew feed amount.

FIG. 15 is a flowchart showing a detection processing procedure of a lateral edge error and a skew feeding error.

FIG. 16 is a diagram showing a configuration of a print position adjusting mechanism in a conventional image forming apparatus.

[Explanation of symbols]

27 Laser control circuit 62 cash register section 64 Horizontal edge detector 65 CIS controller 82 Timing generation circuit 105 Timing Control Unit (TCU) 107 sheets 202 laser 203 Registration roller (registration clutch) 204 CIS (contact image sensor) 211a to 217a Light receiving element section 411 User mode key

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 21/14 G03G 15/04 120 H04N 1/00 108 F term (reference) 2H027 DA21 DC00 DE02 DE07 DE10 ED04 EE02 EE06 EK03 EK11 2H072 AA03 AA09 AA16 AA24 AB22 CA01 2H076 AB02 AB67 EA21 3F048 AA02 AA04 AA05 AB01 BA19 BA20 BB02 BB10 CC03 CC05 DA06 DC15 EA02 EB38 5C062 AA05 AB08 AB20 AB32 AB33 AC66 AF66

Claims (14)

[Claims] 1. An image forming apparatus for forming an image on a sheet conveyed from a predetermined sheet storage section through a feeding path, the image forming apparatus having a plurality of read pixels for reading an image, the plurality of read pixels being the sheet. The sheet reading unit disposed in the feeding path, which is a passage region of the sheet to be conveyed, is arranged so as to be aligned in the direction perpendicular to the conveying direction of the sheet, and the plurality of read pixels of the sheet reading unit are repeated. Deviation amount detecting means for detecting the position deviation amount of the conveyed paper by reading, a first threshold value determined in advance, and a second threshold value which is smaller than the first threshold value and is input If the positional deviation amount of the sheet detected by the deviation amount detecting unit is larger than the first threshold value, it is determined that the conveyed sheet is an error and the image forming operation is stopped. Stop Stage and, at the positional deviation amount of the sheet is detected following the first threshold value by the displacement amount detecting means, and greater than the second threshold value, determines that the paper to be the transfer is an error,
An image forming apparatus comprising: a continuation unit that continues the image forming operation without stopping. 2. The sheet reading unit is arranged between a registration roller that conveys a sheet to an image forming unit at a predetermined timing and the image forming unit.
The image forming apparatus described. 3. An image forming an image by irradiating an image carrier with a laser to form an electrostatic latent image on the basis of input image data, developing the electrostatic latent image and transferring the electrostatic latent image to a sheet. 3. The forming apparatus, wherein the writing start position of the laser in the direction perpendicular to the carrying direction is determined based on the amount of positional deviation of the sheet detected by the deviation amount detecting means. The image forming apparatus described. 4. The image forming apparatus according to claim 1, wherein the positional shift amount of the sheet is a lateral shift amount and / or a skew feed amount in a direction perpendicular to the transport direction. 5. The first threshold value is a threshold value for the image forming apparatus to recognize an amount of positional deviation of a sheet being conveyed as an error due to a structural reason.
The image forming apparatus described. 6. The image forming apparatus according to claim 1, wherein the second threshold value is a threshold value for a user to recognize an image shift amount with respect to a sheet as an error. 7. The continuation unit, when continuing the image forming operation without stopping, cancels a part of the post-processing of the job being created, ejects the part of the paper, and executes the post-processing. The image forming apparatus according to claim 1, wherein after the resetting, the image forming operation of the part of the sheets is started again. 8. An image forming control method for an image forming apparatus for forming an image on a sheet conveyed from a predetermined sheet storage section through a feeding path, the image forming control method comprising a plurality of read pixels for reading an image. The image forming apparatus is provided with a sheet reading unit arranged in the feeding path, which is a passage area of the conveyed sheet, so that the reading pixels are arranged in a direction perpendicular to the sheet conveying direction. A deviation amount detecting step of detecting a positional deviation amount of the conveyed paper by repeatedly reading the plurality of read pixels of the paper reading unit; a first threshold value determined in advance; When the value is a small value and the input second threshold value is set, and the positional deviation amount of the sheet detected in the deviation amount detecting step is larger than the first threshold value, the sheet is conveyed. The paper is And a stop step of stopping the image forming operation, and the positional deviation amount of the sheet detected in the deviation amount detecting step is less than or equal to the first threshold value and greater than the second threshold value, An image forming control method, comprising: a continuous step of judging that the conveyed sheet is in error and continuing the image forming operation without stopping. 9. The sheet reading unit is arranged between a registration roller that conveys a sheet to an image forming unit at a predetermined timing and the image forming unit.
The described image forming control method. 10. An image for forming an image by irradiating a laser on an image carrier to form an electrostatic latent image based on inputted image data, developing the electrostatic latent image and transferring the electrostatic latent image to a sheet. 9. A writing start position of a laser, which is applied to a forming apparatus and is determined based on a positional deviation amount of a sheet detected in the deviation amount detecting step, in a direction perpendicular to the transport direction.
Alternatively, the image formation control method according to item 9. 11. The image forming control method according to claim 8, wherein the positional deviation amount of the sheet is a lateral deviation amount and / or a skew amount in a direction perpendicular to the transport direction. 12. The image according to claim 8, wherein the first threshold value is a threshold value for the image forming apparatus to recognize a positional deviation amount of a sheet conveyed due to a configuration reason as an error. Formation control method. 13. The image forming control method according to claim 8, wherein the second threshold value is a threshold value for a user to recognize an amount of deviation of an image with respect to a sheet as an error. 14. In the continuation step, when the image forming operation is continued without being stopped, a part of the post-processing of the job being created is canceled and the part of the paper is discharged, and the post-processing is performed. 9. The image forming control method according to claim 8, wherein the image forming operation of the part of the sheets is started again after resetting.