JP2001201896A - Image forming apparatus and signal processing apparatus - Google Patents

Abstract

(57) [Problem] To detect a mounting position of a sensor based on a detection result of a pattern image by a sensor, and form a pattern image with a minimum size at an appropriate position according to the mounting position of the checked sensor. The amount of toner consumption due to registration adjustment or toner density adjustment is reduced. An initial pattern image including a linear first pattern image IPP1 parallel to a main scanning direction on a surface of an image carrier and a second pattern image IPP2 in which a position in a sub scanning direction is displaced stepwise. An IPP is formed and read by the detection sensor 232. The detection time Ts (ms) is calculated using the reading timings T1 to T4 of the detection sensor 232, and this is calculated as the error distance Ls of the mounting position of the detection sensor 232.
(Mm). Based on the error distance Ls, the formation position of the pattern image in the main scanning direction at the time of subsequent registration adjustment or toner density adjustment is corrected.

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 for forming a toner image by electrophotographic image formation, and sets an operation state of an image forming section based on a result of detection of a pattern image by a detection sensor. The present invention relates to an image forming apparatus and a signal processing apparatus that executes a process based on a detection result of a detection target by a detection sensor.

[0002]

2. Description of the Related Art Copiers, laser printers, and the like for forming an electrophotographic image in which an electrostatic latent image formed on the surface of a photoconductor by photoconductive action is visualized into a toner image and then transferred onto a recording medium. Y (yellow),
A toner image is formed with each of a plurality of color toners such as M (magenta), C (cyan) and K (black), and these toner images are superimposed directly on a recording medium or via a toner image carrier. There is a color image forming apparatus configured to form a color image by using a color image forming apparatus. In such a color image forming apparatus, if an error occurs in the transfer position of each color toner image on the recording medium, the quality of the color image deteriorates.

Therefore, in a conventional color image forming apparatus,
As in Japanese Patent No. 2642351, a pattern image for adjustment is formed using each of the toners of a plurality of colors, and the positional relationship between the formed pattern images of each color is confirmed to adjust the image forming timing of each color. In some cases, registration adjustment is performed to match the image forming positions of each color.

[0004]

However, in the conventional color image forming apparatus for performing registration adjustment, if the registration adjustment work is repeatedly performed to improve the image quality,
A large amount of toner is consumed to form a pattern image,
There is a problem that raises running costs. Also, in the case where the sensor for detecting the formation position of the pattern image is provided, the size of the sensor is larger than the size that can be detected by the sensor so that the pattern image can be reliably detected even when an error occurs in the mounting position of the sensor. Generally, a large-sized pattern image is formed, and waste of toner due to registration adjustment becomes serious. Further, in the case where a different sensor is provided for each color toner, all color toners used for forming a color image are used for registration adjustment,
There is a problem that a larger amount of toner is wasted in the registration adjustment. Such a problem also occurs in an image forming apparatus that adjusts the toner density based on the result of the detection of the pattern image by the sensor or in an image forming apparatus that controls the operation state when forming a monochrome image.

An object of the present invention is to confirm a mounting position of a sensor based on a detection result of a pattern image by the sensor,
By forming a pattern image with the minimum size at an appropriate position corresponding to the confirmed mounting position of the sensor, toner consumption due to registration adjustment or toner density adjustment for controlling the operation state of the image forming unit is reduced. Accordingly, an object of the present invention is to provide an image forming apparatus capable of reducing running costs.

[0006]

The present invention has the following arrangement as means for solving the above-mentioned problems.

(1) An image forming apparatus including a detection sensor for optically detecting a pattern image formed on an image carrier by an image forming unit, and controlling an operation state of the image forming unit based on a detection result of the detection sensor. The apparatus is characterized in that the positional relationship between the image carrier and the detection sensor is confirmed based on the detection result of the detection sensor for the initial pattern image formed on the image carrier.

In this configuration, the positional relationship between the detection sensor for optically detecting the pattern image formed on the image carrier and the image carrier is confirmed based on the detection result of the initial pattern image by the detection sensor. You. Therefore, by forming a pattern image used for controlling the operation state of the image forming unit at a position on the image carrier according to the confirmed positional relationship with the detection sensor, the pattern image is accurately detected by the detection sensor. The operation state of the image forming unit is accurately controlled. Further, there is no need to form a pattern image used for controlling the operation state of the image forming section over a wide area on the image carrier, and the amount of toner consumption is reduced.

(2) The initial pattern image has a shape facing the detection sensor at different timings at a plurality of positions in a direction orthogonal to the moving direction of the image carrier.

[0010] In this configuration, the detection timing of the initial pattern image by the detection sensor is different from each other at a plurality of positions in the direction orthogonal to the moving direction of the image carrier. Therefore, from the timing when the detection sensor detects the initial pattern image, the position on the image carrier facing the detection sensor in the direction orthogonal to the moving direction of the image carrier can be easily confirmed.

(3) The initial pattern image has a shape facing the detection sensor at a plurality of positions in a direction orthogonal to the moving direction of the image carrier for different times from each other.

In this configuration, the detection time of the initial pattern image by the detection sensor differs at a plurality of positions in the direction perpendicular to the moving direction of the image carrier. Therefore, the position on the image carrier where the detection sensor faces in the direction orthogonal to the moving direction of the image carrier can be easily confirmed from the time when the detection sensor continuously detects the initial pattern image.

(4) A single pattern image is detected a plurality of times by the detection sensor, and an average value of detection results included in a range of a predetermined level among the plurality of detection results is determined as a detection result of the detection sensor. Features.

In this configuration, the pattern image formed on the image carrier is detected a plurality of times, and the average of the detection results included in a predetermined level range among the plurality of detection results is detected by the detection sensor. The result is determined. Therefore, a stable value within a predetermined level range is always obtained as a result of the detection of the pattern image by the detection sensor.

(5) The range of the predetermined level is a range excluding a maximum detection result and a minimum detection result among a plurality of detection results.

In this configuration, the pattern image formed on the image carrier is detected a plurality of times, and the average of the detection results excluding the maximum detection result and the minimum detection result among the plurality of detection results is a detection sensor. Is determined as a pattern image detection result. Therefore, a stable value excluding a detection result largely different from other detection results is obtained as a detection result of the pattern image by the detection sensor.

(6) The pattern image is a pattern image for registration correction for adjusting the timing of image formation on the image carrier by the image forming unit based on the detection signal of the detection sensor.

In this configuration, registration correction for adjusting the timing of image formation on the image carrier is performed based on the detection result of the pattern image by the detection sensor. Therefore, the timing of image formation on the image carrier is properly determined based on the detection result of the detection sensor.

(7) A single detection target is detected a plurality of times by the detection sensor, and an average value of the detection results included in a range of a predetermined level among the plurality of detection results is determined as the detection result of the detection sensor. And

In this configuration, the detection target is detected a plurality of times, and the average of the detection results included in the range of the predetermined level among the plurality of detection results is determined as the detection result by the detection sensor. Therefore, a stable value within a predetermined level range is always obtained as a detection result of the detection target by the detection sensor.

(8) The range of the predetermined level is a range excluding a maximum detection result and a minimum detection result among a plurality of detection results.

In this configuration, the detection target is detected a plurality of times, and the average of the detection results excluding the maximum detection result and the minimum detection result among the plurality of detection results is determined as the detection result of the detection target by the detection sensor. Is done. Therefore, as the detection result of the detection target by the detection sensor, a stable value excluding a detection result that is significantly different from other detection results is obtained.

[0023]

FIG. 1 is a schematic front sectional view showing the configuration of a digital color copying machine which is a color image forming apparatus according to an embodiment of the present invention. The copier body 1 has a document table 11 and an operation panel (not shown) arranged on the upper surface, and an image reading unit 110, an image forming unit 210, and a paper feeding unit 211 inside.
Is provided. A reversing automatic document feeder (RADF: Reversing Automatic
Document Feeder) 112 is attached. RADF
112 feeds the originals placed on the tray one by one to the upper surface of the original platen 111 in synchronization with the operation of the copying machine main body 1;
After the reading of the document image by the image reading unit 110 is completed, the document on the document table 111 is discharged to a discharge tray.
Also, in the double-sided original mode in which the images on both sides of the original are read, the original on which the one-sided image has been read is turned upside down and fed to the original platen 111 again. The document is discharged to the discharge tray after the process is completed. The RADF 112 is supported so that the upper surface of the document table 111 can be freely opened and closed, and the document can be handled on the upper surface of the document table 111 manually.

The image reading section 110 reads an image of a document placed on a document table 111, a first mirror base 113 having an exposure lamp and a mirror, a second mirror base 114 having a mirror, and a lens 115. And a CCD line sensor (hereinafter, referred to as a CCD) 116 which is a photoelectric conversion element. First mirror base 113
The scanner reciprocates at a constant speed in parallel with the lower surface of the original table 111 made of a transparent glass body, and scans the image surface of the original placed on the upper surface of the original table 111 with light emitted from an exposure lamp. The second mirror base 114 reciprocates at a speed half the moving speed of the first mirror base 113 in parallel with the lower surface of the document table 111, and maintains a constant optical path length from the image surface of the document to the CCD 116. Then, the reflected light of the light of the exposure lamp on the image surface of the document is distributed to the lens 115. The lens 115 transmits the reflected light on the image surface of the original to the CCD 1
An image is formed on 16 light receiving surfaces. The CCD 116 outputs an electric signal obtained by sequentially photoelectrically converting the light image formed on the light receiving surface.
The CCD 116 converts the color images into R (red), G (green), B
This is a three-line sensor that separates colors into three primary colors (blue) and outputs an electrical signal corresponding to the amount of light for each color. C
The electric signal output from the CD 116 is input to an image processing unit (not shown), and after being subjected to A / D conversion processing and image processing, is supplied to the image forming unit 210 as image data.

The image forming section 210 includes a transfer conveyance belt 216 stretched over a driving roller 214 and a driven roller 215.
, Four image forming stations Pa to Pd are arranged above the transfer / conveying belt mechanism 213 including. Paper feed unit 211 located below image forming unit 210
Feeds the stored sheets P one by one prior to the operation in the image forming stations Pa to Pd of the image forming unit 210. The sheet P fed from the sheet feeding unit 211 is rotated by the registration roller 212 so that the image forming station P
image forming unit 21 at a timing synchronized with the operations of a to Pd
Guided within 0. The transfer conveyance belt mechanism 213 conveys the paper P fed by the registration roller 212 by electrostatically adsorbing the peripheral surface of the transfer conveyance belt 216 rotating in the arrow Z direction. The image forming stations Pa to Pd are opposed to the upper surface of the transfer conveyance belt 216, and the paper P is transferred from the image formation stations Pa to Pd while being conveyed in a state of being electrostatically attracted to the peripheral surface of the transfer conveyance belt 216. The toner image is transferred.

The sheet P transported on the upper surface of the transfer / transport belt 216 in the direction of arrow Z is peeled off from the peripheral surface of the transfer / transport belt 216 by the peeler 229 and then the fixing device 217.
Is heated and pressurized, the toner image is melted and the paper P
Firmly settles on the surface of The sheet P that has passed through the fixing device 217 is discharged to the sheet discharge tray 220 via the gate 218 by the sheet discharge roller 219 via the gate 218. The gate 218 guides the sheet P on which an image is formed on the front surface to the switchback conveyance path 221 in a duplex copying mode in which images are formed on both sides of the sheet P. The sheet P guided to the switchback conveyance path 221 is turned upside down and conveyed again to the registration roller 212, and after the toner image is transferred to the back surface by the image forming stations Pa to Pd, the fixing device 217 and the gate 218. Output tray 2 via
It is discharged to 20.

The image forming stations Pa to Pd have substantially the same configuration. As an example, the image forming station Pa includes a photosensitive drum 222a, a charger 223.
a, a scanner unit 227a, a developing device 224a, a transfer unit 225a, and a cleaner 226a. The photosensitive drum 222 a is formed by transferring a part of the peripheral surface of the transfer belt 2.
16 is supported so as to be rotatable in the direction of arrow F so as to face the upper surface of 16. The charger 223a uniformly applies a charge of a single polarity to the peripheral surface of the photosensitive drum 222a by, for example, corona discharge. The scanner unit 227a includes a light source (not shown) such as a semiconductor laser element, a polygon mirror 240a, an fθ lens 241a, and mirrors 242a and 242.
43a, and irradiates the peripheral surface of the photosensitive drum 222a with image light modulated by image data supplied from the image processing unit. Note that the scanner units 227a to 227a
Instead of 27d, an LED head provided with a light emitting diode array and an imaging lens array may be used. The color image forming apparatus has a plurality of image forming stations because the LED head is not only excellent in quietness because there are no moving parts but also small in size, as compared with a laser beam scanner unit. Suitable for.

An electrostatic latent image is formed on the peripheral surface of the photosensitive drum 222a which has been irradiated with the image light from the scanner unit 227a by a photoconductive action. Developing device 224a
Supplies the toner to the peripheral surface of the photosensitive drum 222a, and visualizes the electrostatic latent image formed on the peripheral surface of the photosensitive drum 222a into a toner image. The transfer device 225a is disposed at a position facing the peripheral surface of the photosensitive drum 222a with the transfer / conveying belt 216 interposed therebetween, and transfers the toner image carried on the peripheral surface of the photosensitive drum 222a by corona discharge or the like. At 216, the sheet is transferred to the surface of the sheet P being conveyed by electrostatic force.

Each of the image forming stations Pa to Pd configured as described above forms a toner image of each color of black, cyan, magenta, and yellow. Therefore, image data of each color of black, cyan, magenta, and yellow is supplied from the image processing unit to each of the scanner units 227a to 227d. Further, the developing device 2
Each of 24a to 224d contains toner of each color of black, cyan, magenta, and yellow. As a result, when copying an image of a color original, the peripheral surfaces of the photosensitive drums 222a to 222d are black,
A toner image of each color of cyan, magenta, and yellow is formed, and is transferred in a state where the toner images are electrostatically attracted to the upper surface of the transfer conveyance belt 216 and sequentially superimposed on the surface of the paper P conveyed in the arrow Z direction.

FIG. 2 is a diagram showing a configuration of a pattern image detecting device in the digital color copying machine. In the digital color copying machine according to the embodiment of the present invention, the image forming stations Pa to Pd are set each time the power to the copying machine main body 1 is turned on and each time a predetermined number of copies are completed.
In each of the above, a predetermined resist pattern image is directly formed on the surface of the transfer / conveying belt 216, and each image forming station P is formed based on the detection result of the resist pattern image.
Registration adjustment is performed to adjust the image forming timing in a to Pd so as to prevent the occurrence of color misregistration in a color image. For this purpose, the transfer / transport belt mechanism 213 in the copying machine main body 1 is provided with a pattern image detecting device 230 for detecting a resist pattern image formed on the surface of the transfer / transport belt 216.

The pattern image detecting device 230 includes detection sensors 232R and 232F facing the peripheral surface of the transfer / transport belt 216 below the rollers 214 and 215 in the transfer / transport belt mechanism 213, and the transfer / transport belt 216.
Rollers 231a and 231b contacting the back of
35. Slots 234a, 234 into which pins 213b, 213c protruding from frame 213a of transfer / transport belt mechanism 213 are fitted.
34b are formed, and the lower end is
The upper ends of the springs 233a and 233b locked to 3a are locked.

With this configuration, the base 235 is moved by the elastic force of the springs 233a and 233b to the detection sensor 2
32R, 232F and the rollers 231a, 231b are urged downward, and the portion of the transfer conveyance belt 216 that faces the pattern image detection device 230 is pressed downward by the rollers 231a, 231b, and the roller 231a and the roller 131b A predetermined tension is applied between them. Thereby, the detection sensors 232R, 23
2F is opposed to the flat transfer / transport belt 216 without slack between the roller 231a and the roller 131b. Each of the detection sensors 232R and 232F is an optical sensor including a light emitting element and a light receiving element, and receives light reflected from the surface of the transfer and conveyance belt 216 by the light receiving element.

FIG. 3 is a plan view showing a relationship between a pattern image formed in the digital copying machine and a detection sensor. In the digital copying machine according to this embodiment,
When the power of the copying machine is turned on and after a predetermined number of copies have been made, the resist patterns P1 and P2 shown in FIG. 3 are formed on the transfer / conveying belt 216 at each of the image forming stations Pa to Pd. Based on the detection results of the detected resist patterns P1 and P2 by the detection sensors 232R and 232F, the image forming stations Pa to P
A registration adjustment for adjusting the image formation position is performed for each of d, thereby preventing color shift on the paper.

The resist patterns P1 and P2 are sequentially formed in predetermined regions near both ends in the direction orthogonal to the direction of movement of the transfer / conveying belt 216 on the surface of the transfer / conveying belt 216, and the horizontal line pattern P1 and the oblique line pattern are provided for each color. It consists of two types of patterns P2. This is read by a pair of detection sensors 232R and 232F. A slit plate is arranged in front of the light receiving region of each light receiving element in the detection sensors 232R and 232F, and detects light other than light reflected from the resist pattern as a detection target.
It is conceivable that 32R and 232F are not detected. However, as shown in FIG.
When two types of resist patterns, that is, the horizontal line pattern P1 and the oblique line pattern P2, are detected by the 32R (232F), depending on the shape of the slit, the detection sensor 232R is provided between the horizontal line pattern P1 and the oblique line pattern P2.
There is a possibility that the detection difference bell of (232F) changes and the passage of each resist pattern cannot be accurately detected.

For example, as shown in FIG. 4, a slit plate 400 disposed between the transfer / conveying belt 216 and the detection sensor 232R (232F) has a detection sensor 232R (2
32F), a slit 400a included in the range of the light receiving area 400b is formed.
Has a rectangular shape whose longitudinal direction matches the longitudinal direction of the horizontal line pattern P1. In this case, with the movement of the transfer conveyance belt 216, as shown in FIGS. 4A to 4C, the horizontal line pattern P1 and the oblique line pattern P2 sequentially pass through the lower surface of the detection sensor 232R (232F).

At this time, as shown in FIG. 4B, while the horizontal line pattern P1 passes through the lower surface of the detection sensor 232R (232F), the light receiving area 400b of the detection sensor 232R (232F) is formed by the slit 400a. The entire surface faces the horizontal line pattern P1. On the other hand, as shown in FIG. 3C, the detection sensor 232R (232F)
The light receiving area 400b of the detection sensor 232R (232F) does not face the diagonal pattern P2 in a part of the slit 400a and faces the surface of the transfer conveyance belt 216 while the diagonal pattern P2 passes through the lower surface of the transfer belt 216.

For this reason, the detection sensor 232R (232
In the detection signal of F), as shown in FIG. 3D, the output level of the detection signal of the oblique line pattern P2 is lower than the output level of the detection signal of the horizontal line pattern P1, and the passage of the oblique line pattern P2 is accurate. May not be detected. In such a case, the detection sensor 232R (2
It is conceivable to switch the amplification factor of the 32F) detection signal between the horizontal line pattern P1 and the oblique line pattern P2, but there is a problem that the circuit configuration becomes complicated.

Therefore, in the digital copying machine according to this embodiment, as shown in FIG. 5, the slit 500a of the slit plate 500 is formed by a rhombus having a substantially middle angle between the inclination of the horizontal line pattern P1 and the inclination of the oblique line pattern P2. It has a shape. That is, the angle θ1 between the longitudinal direction (dashed line L1) of the slit 500a and the sub-scanning direction, which is the transport direction of the transfer transport belt 216, is 90 ° between the longitudinal direction of the horizontal line pattern P1 and the sub-scanning direction. Therefore, θ1 = θ2 + (90−θ2) / 2, where θ2 is the angle between the longitudinal direction (dashed line L2) of the oblique line pattern P2 and the sub-scanning direction. By setting the shape of the slit 500a in this way, as shown in FIGS. 6A to 6D, a detection signal having substantially the same output level as the horizontal line pattern P1 and the oblique line pattern P2 is detected by the detection sensor 232R.
(232F).

Note that the shape of the slit 500a is not limited to the shapes shown in FIGS. 5 and 6, but the output level of the detection signal of the detection sensor 232R (232F) for the horizontal line pattern P1 and the detection level for the oblique line pattern P2. Other shapes can be used as long as the output level of the detection signal of the sensor 232R (232F) substantially matches.

Here, each of the image forming stations Pa to P
The laser scanning optical system of the scanner units 227a to 227d at d has optical distortion. This distortion is caused by optical distortion in the Fθ lens group for scanning the photosensitive member surface in the main scanning direction at a constant speed (pitch), bending of an optical system for exposing the photosensitive member surface in the main scanning direction, This is a curve distortion or the like of a line image caused by an inclination or the like. In particular, when a plastic lens is used for cost reduction, optical distortion is conspicuous, and as a result, distortion occurs in the optical characteristics when performing exposure scanning on the photosensitive member.

Therefore, in the digital copying machine according to the embodiment of the present invention, when forming each pattern image at both ends of the transfer conveyance belt 216 in the direction (main scanning direction) orthogonal to the conveyance direction, the scanning optical system is used. A pattern image is formed in a region where the right and left optical distortion characteristics are substantially equal. In a digital copying machine in which a plurality of image forming stations are arranged in parallel, a pattern image is formed in a region where the optical distortion characteristics of the scanner units of each image forming station are substantially equal.
As a result of the experiment, the result of the registration correction was most stable when the pattern image was formed in a region 115 mm left and right from the center on the transfer / conveying belt 216 as the image carrier.

As a result, a pair of pattern images are formed at both ends of the transfer / transport belt 216 with a fixed positional relationship, and the inclination of the image recorded on the transfer / transport belt 216 (the transfer / transport belt in the scanner unit) (The inclination of the laser beam with respect to the main scanning direction) can be surely corrected. Further, each image formed in the plurality of image forming stations is transferred to the transfer / conveying belt 21.
Registration correction when sequentially superimposing on the photoreceptor 6 (correction of the inclination of the laser scanning light with respect to the main scanning direction of the photoreceptor in the laser scanning unit alone, and correction of the overlap position between images recorded and reproduced on the photoreceptor in each recording unit) ) Is performed reliably, the images are accurately superimposed in a predetermined positional relationship, and faithfully reproduced as a color image.

A method of processing a detection signal in the pattern image detecting device of the digital copying machine will be described below. After a resist pattern image of each color is formed on the surface of the transfer / transport belt 216 at the image forming stations Pa to Pd, the transfer / transport belt 216 is rotated and the resist pattern image is detected by the detection sensor 232R (232F) of the pattern image detection device 230. And the transit time of each resist pattern image is detected. This process is repeated a plurality of times, and the detection result of the maximum value among the detection results and the average value of the remaining detection results excluding the detection result of the minimum value are set as the detection results. Then, registration correction of the image forming process in the image forming stations Pa to Pd is performed. In this manner, since the average value excluding the maximum value and the minimum value among the plurality of detection results is used as the detection result, the accuracy of the detection result can be improved.

FIG. 7 is a circuit diagram of the pattern image detecting device. In the pattern image detection device 230,
A light receiving signal of the reflected light of the light emitted from the light emitting element 232a of the detection sensor 232 at the light receiving element 232b is input to the inverting input terminal of the comparator 232d via the amplifier 232c. The amount of reflected light on the surface of the transfer conveyance belt 216 is larger than the amount of reflected light on the resist pattern image. Therefore, the light receiving element 232b that has received the light reflected on the surface of the transfer conveyance belt 216 is at “H”.
If the output voltage at this time is 3 V, the threshold voltage input to the non-inverting input terminal of the comparator 232 d is 2 V, and the output signal of the comparator 232 d is at “L” level. Becomes On the other hand, the light receiving element 232b that has received the light reflected in the resist pattern image outputs a light receiving signal of “L” level. If the output voltage at this time is 1V, the light receiving element 232b is connected to the non-inverting input terminal of the comparator 232d. Since a threshold voltage of 2 V has been input, the output signal of the comparator 232d goes high.

As described above, by inputting the light receiving signal of the light receiving element 232b to the inverting input terminal of the comparator 232d, the "H" level detection signal is output from the pattern image forming apparatus 230 while the resist pattern image is being detected. The detection signal of the “L” level is output from the pattern image forming apparatus 230 in a state where the output is performed and the resist pattern image is not detected.

FIG. 8 is a waveform diagram of a detection signal in the pattern image detecting device. In the digital color copying machine according to the embodiment of the present invention, the pattern image detecting device 2
30 based on the black toner pattern image PPa based on the 30 detection signals.
b, the distance between each of the magenta toner pattern image PPc and the yellow toner pattern image PPd is measured, and registration correction for adjusting the image forming timing in each of the image forming stations Pa to Pd is performed based on the measured results. .

FIG. 8A shows an image forming station Pa.
FIG. 9 is a waveform diagram of a detection signal of the pattern image detection device 230 when the image formation timing in Pd is appropriate. In this case, the center position Ck of the pattern image PPa
Is obtained from the rising timing KT1 and the falling timing KT2 of the detection signal as Ck = (KT1 + KT2) / 2. Similarly, pattern images PPb to PPd
Are obtained by the following equation: Cc = (CT1 + CT2) / 2 Cm = (MT1 + MT2) / 2 Cy = (YT1 + YT2) / 2 The pattern image P obtained in this way
Using each center position of Pa to PPd, the pattern image P
The reference distances ΔT1 to ΔT3 between Pa and each of the pattern images PPb to PPd are ΔT1 = {(KT1 + KT2) / 2} − ／ (CT1 + C
T2) / 2｝ ΔT2 = ｛(KT1 + KT2) / 2｝-｛(MT1 + M
T2) / 2｝ ΔT3 = ｛(KT1 + KT2) / 2｝-｛(YT1 + Y
T2) / 2}.

FIG. 8B shows an image forming station Pa.
FIG. 9 is a waveform diagram of an output signal of the pattern image detection device 230 when an error occurs in the image forming timing in the image forming stations Pb to Pd as compared with the image forming timing in FIG. In this case, the pattern image PPa of the black toner and the other pattern images PPb to PP
Similarly, the distances ΔT1 ′ to ΔT3 ′ with respect to d are ΔT1 ′ = {(KT1 ′ + KT2 ′) / 2} − ｛(CT
1 ′ + CT2 ′) / 2｝ ΔT2 ′ = {(KT1 ′ + KT2 ′) / 2} − ｛(MT
1 ′ + MT2 ′) / 2｝ ΔT3 ′ = {(KT1 ′ + KT2 ′) / 2} − ｛(YT
1 ′ + YT2 ′) / 2｝.

Therefore, the image forming stations Pb to Pb
The resist correction amounts A1 to A3 in Pd are as follows: A1 = ΔT1-ΔT1 ′ A2 = ΔT2-ΔT2 ′ A3 = ΔT3-ΔT3 ′ When the registration correction amounts A1 to A3 are positive values, the image forming timing in the image forming stations Pb to Pd is earlier than the image forming timing in the image forming station Pa. This means that the image forming timing in the image forming stations Pb to Pd is later than the image forming timing in the forming station Pa. As described above, the process of calculating the registration correction amount is executed a plurality of times, and the average of a plurality of calculation results within a predetermined level range is determined as the registration correction amount by excluding the maximum value and the minimum value.

As described above, the pattern images PPa to PPd formed on the transfer belt 216 are detected a plurality of times, and the average of the detection results excluding the maximum detection result and the minimum detection result among the plurality of detection results is calculated. By determining the detection results of the pattern images PPa to PPd by the detection sensor, it is possible to obtain a stable detection result that is always included in a range of a predetermined level, excluding detection results that are significantly different from other detection results.

Note that such an effect is not limited to the detection value of the pattern sensor for registration adjustment in the image forming process, but is generally applied to a signal processing device that detects a detection target using the detection sensor. be able to.

As described above, the transfer conveyance belt 216
When adjusting the image forming timing in each image forming station based on the detection result of the pattern image formed above, it is necessary to accurately detect the pattern image formed in each image forming station by a detection sensor. For this purpose, a pattern image must be formed at a position on the transfer / transport belt where the detection sensor faces. However, the position where the detection sensor opposes on the transfer conveyance belt fluctuates due to errors in assembling and attaching the detection sensor. If the size of the pattern image is determined in consideration of this variation range, the area of the pattern image becomes large, and a large amount of toner is generated for a registration adjustment pattern image that is not an image formed in a normal image forming process. It is wasted and causes the running cost to rise.

Therefore, according to the present invention, a sensor position detecting process for detecting the positional relationship between the image carrier and the detection sensor using the initial pattern image is executed, and the detection sensor in the image carrier is detected based on the detected positional relationship. By forming a pattern image for registration adjustment on the opposing portion, it is not necessary to increase the area of the pattern image, thereby preventing waste of toner.

FIG. 9 is a flow chart showing a processing procedure at the time of sensor position detection processing for detecting the positional relationship between the image carrier and the detection sensor in the digital copying machine. FIG. 10 is a diagram showing an initial pattern image formed on the image carrier during the sensor position detection process, and FIG. 11 is a diagram showing a method of calculating the detection timing of the initial pattern image during the sensor position detection process. It is.

In the sensor position detecting process shown in FIG. 9, first, the surface of the transfer / conveying belt 216 as an image carrier is
The initial pattern image IPP shown in FIG.
1). The initial pattern image IPP has a linear first pattern image IPP1 parallel to the main scanning direction which is a direction orthogonal to the movement direction of the transfer conveyance belt 216, and a position in the sub-scanning direction which is the movement direction of the transfer conveyance belt 216. And a second pattern image IPP2 in which is displaced stepwise.
The first pattern image IPP1 is located on the upstream side of the second pattern image IPP2 in the moving direction of the transfer conveyance belt 216. Therefore, the detection sensor 232 fixed at a position facing the upper surface of the transfer conveyance belt 216
After facing the pattern image IPP1, it faces the second pattern image IPP2.

Next, the initial pattern image IPP is read by the detection sensor 232 (1002). As described above, the detection sensor 232 faces the first pattern image IPP1 and the second pattern image IPP2 in this order, and reads the first pattern image IPP1 and then reads the second pattern image IPP1.
Read 2. Since the first pattern image IPP1 is formed linearly in a direction orthogonal to the moving direction of the transfer / conveying belt 216, even if an error occurs in the mounting position of the detection sensor 232 in the main scanning direction, the detection sensor 232 is not moved. The timing facing the pattern image IPP1 is constant. On the other hand, since the second pattern image IPP2 is formed by displacing the position in the movement direction of the transfer conveyance belt 216 in a stepwise manner, the detection sensor 2 in the main scanning direction is displaced.
The timing at which the detection sensor 232 faces the second pattern image IPP <b> 2 changes according to the mounting position of the 32. Therefore, the detection sensor 232 determines that the first pattern image IPP
1 from the timing of reading the second pattern image IPP
The position of the detection sensor 232 in the main scanning direction can be detected from the time until the timing at which the second sensor 2 is read.

Then, the waveform of the detection signal of the detection sensor 232 in a state where the transfer conveyance belt 216 on which the initial pattern image IPP has been formed is moved is compared with a predetermined threshold value.
As shown in FIG. 11, a timing T1 at which the detection sensor 232 faces the first pattern image IPP1, a timing T2 at which the detection sensor 232 no longer faces the first pattern image IPP1,
A timing T3 facing the pattern image IPP2 and a timing T4 at which the timing no longer faces the second pattern image IPP2 are measured, and using the measured timings T1 to T4, Ts = (T3 + T4) / 2− (T1 + T2) / 2. Calculate the detection time Ts (ms) by Equation 1 (100
3).

The detection time Ts (m
s) is calculated by the following equation: Ls = (Ts × PS−La) / Ld (2)
(Mm) (1004). Here, PS is a process speed (mm / ms) which is a moving speed of the peripheral surface of the transfer / conveyance belt 216, and La is a center position of the first pattern image IPP1 at a proper mounting position of the detection sensor 232 and a second pattern. The distance (mm) from the center position of the image IPP2, and Ld is the displacement amount (mm) in the sub-scanning direction of the second pattern image IPP2.

The above processes 1001 to 1004 are repeatedly executed a predetermined number of times (1005 → 1001), and the average value of a plurality of obtained error distances Ls is calculated (100
6) The measurement accuracy of the error distance Ls can be improved. However, the processing of 1005 and 1006 can be omitted. Further, the accuracy of measurement of the error distance Ls can also be improved by repeatedly executing the processing of 1001 to 1003 a predetermined number of times and substituting the average value of the obtained plurality of detection times Ts into the above equation 2.

The error distance Ls obtained by the above processing
By correcting the formation position of the pattern image in the main scanning direction at the time of the subsequent registration adjustment, the pattern image for the registration adjustment can be reliably detected by the detection sensor 232. That is, by displacing the pattern image forming positions in the image forming stations P1 to P4 by the error distance Ls in the main scanning direction at the time of registration adjustment, the registration adjustment pattern is shifted to a position where the detection sensor 232 faces the transfer conveyance belt 216. An image can be formed.

FIG. 12 is a diagram showing the shape of another initial pattern image formed at the time of the sensor position detection process, and FIG. 13 is a diagram showing a method of calculating the detection timing based on this another initial pattern image. The initial pattern image IPP ′ shown in FIG. 12 includes a straight line parallel to the main scanning direction, which constitutes an end on the upstream side in the sub-scanning direction, a side surface parallel to the sub-scanning direction of the transfer conveyance belt 216, and a main scanning direction. It has a substantially triangular shape surrounded by a broken line whose position in the sub-scanning direction is displaced stepwise according to the position. That is, the initial pattern image IPP 'has a shape in which the length in the sub-scanning direction changes according to the position in the main scanning direction.

When an error in the mounting position of the detection sensor 232 is detected using the initial pattern image IPP ',
As shown in FIG. 13, a timing T11 at which the detection sensor 232 faces the initial pattern image IPP and a timing T1 at which the detection sensor 232 no longer faces the initial pattern image IPP '.
2, the detection time Ts (ms) is calculated according to Ts = T12−T11, and the calculated detection time Ts is substituted into the above equation 2 to convert to the error distance Ls. Note that the formation of the initial pattern image IPP ', the reading of the initial pattern image IPP' by the detection sensor 232, the calculation of the detection time Ts, and the conversion to the error distance Ls are repeated a predetermined number of times, whereby the detection sensor 232 is executed. Position detection accuracy can be improved. The detection time Ts can also be measured by directly measuring the time from timing T11 to timing T12. As described above, by using the initial pattern image IPP ′ having the shape shown in FIG. 12, the arithmetic processing at the time of the sensor position detection processing can be simplified.

The contents of the sensor position detection processing for the detection sensor for detecting the pattern image for registration adjustment have been described above. However, the error in the mounting position in the main scanning direction is also detected for the detection sensor for toner density adjustment by the same processing. By detecting and displacing the formation position of the subsequent pattern image for toner density adjustment based on this detection result, it is not necessary to increase the size of the pattern image, and waste of toner can be prevented.

In an image forming apparatus including a black toner detection sensor for detecting the density of black toner and a color toner detection sensor for detecting the densities of yellow, magenta, and cyan color toners, a black toner detection sensor is provided. And each of the color toner detection sensors,
If the initial pattern image for the sensor position detection process is formed, a large amount of toner is wasted at the time of the sensor position detection process, and the calculation process becomes complicated.

Therefore, as shown in FIG. 14, the black toner detection sensor 232k and the color toner detection sensor 232c
Are unitarily arranged at predetermined intervals Sd in the main scanning direction to form a unit, so that a sensor position detection process using the initial pattern image IPP for either the black toner detection sensor 232k or the color toner detection sensor 232c. Thus, an error in the mounting position may be detected, and for the other remaining sensor, the error in the mounting position may be calculated from the detection result of one sensor and the distance Sd between the two sensors in the unit. Thus, it is possible to obtain an error in the mounting position of a plurality of detection sensors by executing only one sensor position detection process. In addition, the pattern images PPa to PPd for adjusting the toner density in each image forming station according to the error of the mounting position of the detection sensor.
By displacing the formation position of the pattern image PP
a to PPd without increasing the size of the detection sensor 232k,
The pattern images PPa to PPd can be reliably detected by 232c, and the toner density can be accurately adjusted.

The above configuration can be generally applied not only to a color image forming apparatus but also to an image forming apparatus that controls an operation state based on a result of detection of a pattern image by a sensor.

[0067]

According to the present invention, the following effects can be obtained.

(1) The positional relationship between a detection sensor for optically detecting the pattern image formed on the image carrier and the image carrier is confirmed based on the detection result of the initial pattern image by the detection sensor. By forming a pattern image used for controlling the operation state of the image forming unit at a position on the image carrier corresponding to the positional relationship with the confirmed detection sensor, the pattern image can be accurately detected by the detection sensor. Thus, the operation state of the image forming unit can be accurately controlled. Further, it is not necessary to form a pattern image used for controlling the operation state of the image forming section over a wide area on the image carrier, so that waste of toner can be prevented and running cost can be reduced.

(2) The detection timing of the initial pattern image by the detection sensor is made different at a plurality of positions in the direction orthogonal to the moving direction of the image carrier, so that the detection sensor detects the initial pattern image based on the detection timing. Thus, the position on the image carrier facing the detection sensor in the direction orthogonal to the moving direction of the image carrier can be easily confirmed.

(3) By making the detection time of the initial pattern image by the detection sensor different from each other at a plurality of positions in the direction orthogonal to the moving direction of the image carrier, based on the time at which the detection sensor detects the initial pattern image Thus, the position on the image carrier facing the detection sensor in the direction orthogonal to the moving direction of the image carrier can be easily confirmed.

(4) The pattern image formed on the image carrier is detected a plurality of times, and the average of the detection results included in a predetermined level range among the plurality of detection results is determined as the detection result of the pattern image by the detection sensor. By doing
As a result of the detection of the pattern image by the detection sensor, a stable value within a predetermined level range can always be obtained.

(5) The pattern image formed on the image carrier is detected a plurality of times, and the average of the detection results excluding the maximum detection result and the minimum detection result among the plurality of detection results is averaged by the detection sensor. By determining the detection result as an image detection result, a stable value excluding a detection result that is significantly different from other detection results can be obtained as a detection result of the pattern image by the detection sensor.

(6) By performing registration correction for adjusting the timing of image formation on the image carrier based on the result of detection of the pattern image by the detection sensor, the correction on the image carrier is performed based on the detection result of the detection sensor. The image forming timing can be appropriately determined.

(7) The detection target is detected a plurality of times,
By determining the average of the detection results included in the predetermined level range among the plurality of detection results as the detection result by the detection sensor, a stable value within the predetermined level range is always obtained as the detection result of the detection target by the detection sensor. Obtainable.

(8) The detection target is detected a plurality of times,
By determining the average of the detection results excluding the maximum detection result and the minimum detection result among the plurality of detection results as the detection result of the detection target by the detection sensor, other detection results are obtained as detection results of the detection target by the detection sensor. It is possible to obtain a stable value excluding a detection result that is significantly different from the result.

[Brief description of the drawings]

FIG. 1 is a schematic front sectional view showing a configuration of a digital color copying machine which is a color image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a pattern image detecting device in the digital color copying machine.

FIG. 3 is a plan view showing a relationship between a pattern image formed in the digital copying machine and a detection sensor.

FIG. 4 is a diagram illustrating a detection state of a pattern image by a detection sensor in a conventional digital copying machine.

FIG. 5 is a view showing a shape of a slit hole of a detection sensor of the digital copying machine according to the embodiment of the present invention.

FIG. 6 is a diagram illustrating a detection state of a pattern image by a detection sensor in the digital copying machine.

FIG. 7 is a circuit diagram of a pattern image detecting device applied to the digital copying machine.

FIG. 8 is a waveform diagram of a detection signal in the pattern image detection device.

FIG. 9 is a flowchart showing a processing procedure at the time of sensor position detection processing for detecting a positional relationship between an image carrier and a detection sensor in the digital copying machine.

FIG. 10 is a diagram showing an initial pattern image formed on an image carrier during the sensor position detection processing.

FIG. 11 is a diagram showing a calculation method of a detection timing of an initial pattern image in the sensor position detection processing.

FIG. 12 is a diagram showing another shape of the initial pattern image.

FIG. 13 is a diagram illustrating a method of calculating the detection timing of the initial pattern image having another shape.

FIG. 14 is a diagram showing a relationship between a detection sensor and a pattern image according to another embodiment of the present invention.

[Explanation of symbols]

1-Digital Copier (Color Image Forming Apparatus) 216-Transfer Conveying Belt (Image Carrier) 230-Pattern Image Detector 232, 232F, 232R, 232k, 232c-Detection Sensor PPa-PPd-Pattern Image IPP, IPP'- Initial pattern image

Continued on the front page (72) Inventor Tamashii Mashiba 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka F-term (reference) 2H027 DA09 DA21 DA38 DE02 DE07 EB06 EC03 ED04 2H030 AA01 AB02 BB16 BB36 BB44 BB46 BB56

Claims (8)

[Claims] A detection sensor for optically detecting a pattern image formed on an image carrier by an image forming unit;
In an image forming apparatus for controlling an operation state of an image forming unit based on a detection result of a detection sensor, an image carrier and a detection sensor are provided based on a detection result of the detection sensor for an initial pattern image formed on the image carrier. An image forming apparatus for detecting a positional relationship of the image forming apparatus. 2. The image according to claim 1, wherein the initial pattern image has a shape facing the detection sensor at different timings at a plurality of positions in a direction orthogonal to the moving direction of the image carrier. Forming equipment. 3. The image according to claim 2, wherein the initial pattern image has a shape facing the detection sensor at a plurality of positions in a direction perpendicular to the moving direction of the image carrier for different times. Forming equipment. 4. The method according to claim 1, wherein a single pattern image is detected a plurality of times by the detection sensor, and an average value of the detection results included in a predetermined level range among the plurality of detection results is determined as a detection result of the detection sensor. The image forming apparatus according to claim 1. 5. The image forming apparatus according to claim 4, wherein the range of the predetermined level is a range excluding a maximum detection result and a minimum detection result among a plurality of detection results. 6. A pattern image for register correction for adjusting a timing of forming an image on an image carrier by an image forming unit based on a detection signal of a detection sensor. Or the image forming apparatus according to 5. 7. The method according to claim 1, wherein a single detection target is detected a plurality of times by a detection sensor, and an average value of the detection results included in a predetermined level range among the plurality of detection results is determined as a detection result of the detection sensor. Signal processing device. 8. The signal processing apparatus according to claim 7, wherein the range of the predetermined level is a range excluding a maximum detection result and a minimum detection result among a plurality of detection results.