JP2002023450A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of at least 3 or more units of detecting means being required in order to detect color deviation including a scanning curve since the detecting means of an optical method provided with a semiconductive laser and a driving circuit are provided exclusively on a light emitting side in the conventional color deviation detecting means of a tandem method image forming device. SOLUTION: In the device, an exposing means, a means to move an optical path in order to have a laser beam utilized for detection of the color deviation, an image carrier where the laser beam can be transmitted and a light receiving means to receive the laser light that has been transmitted through the image carrier are provided. In this case, the color deviation quantity can be detected with high precision an at a low cost constitution by utilizing the same laser beam for image formation and color deviated quantity detection and the toner quantity necessary for the detection can be decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus having a plurality of photoconductors, which detects a color shift.
The present invention relates to a technique for accurately performing color matching on a recording medium.

[0002]

2. Description of the Related Art Conventionally, as a color shift detection in a tandem type image forming apparatus, an optical detection unit using a laser or the like has been mainly used for the purpose of performing high-accuracy detection.

FIG. 13 is a block diagram showing a conventional color misregistration detection system. The laser beam 5 from the exposing means 1 is
A latent image is formed on the transfer belt, and the image is developed and transferred to the transfer belt or the intermediate transfer unit 13. The timing at which the transferred registration pattern passes through the color misregistration detection unit 14 is detected, and the amount of misregistration is calculated from the difference between the detected timings of each color, and is corrected. The transport direction is indicated by A.

[0004]

However, in the above-mentioned conventional configuration, an expensive semiconductor laser and a drive circuit for emitting the laser are required as a light emitting source. Since strict positional accuracy is required, it is necessary to increase the assembly processing accuracy of each member. In addition, adjustment man-hours are required, which causes a problem such as a high cost ratio to a product. Further, as a configuration of the detecting means, one light receiving unit is paired with one light emitting source, and in this case, the detection range is limited to the light emitting source. Had a problem that it could not be detected.

In order to solve such a problem, the present invention constitutes a low-cost detection means, detects all color misregistration errors including scanning curvature with high accuracy, and shortens the detection correction time. An object of the present invention is to provide an image forming apparatus capable of realizing a reduction in toner consumption.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an exposure unit, a unit for moving an optical path from the exposure unit, an image carrier that transmits light from the exposure unit, and an exposure unit. By performing high-accuracy registration detection with a configuration having a light-receiving unit that detects light from the camera, color shift correction can be performed accurately and in a short time, and an image with high print quality can be obtained. .

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention comprises an exposure means, means for changing the optical path of the exposure means, and a transparent image carrier, and a light source for detecting a color shift is exposed. Cost reduction can be measured by sharing with means.

According to a second aspect of the present invention, there is provided means for changing the optical path of the exposure means, and a mirror can be used for changing the optical path and a moving distance such as a stepping motor can be managed for controlling the mirror position by the number of steps. Accordingly, it is possible to design with an inexpensive configuration and a large optical tolerance, perform accurate color misregistration correction, and obtain an image with high print quality.

According to a third aspect of the present invention, there is provided means for storing the number of steps of a stepping motor, which is a mirror moving means, and for managing a mirror moving distance.
It is possible to perform high-precision detection and correct color misregistration, thereby obtaining an image with high print quality.

According to a fourth aspect of the present invention, there is provided means for changing the optical path of the exposure means, and driving means for forming an image. A mirror is used for changing the optical path, and a clutch and a driving means are used for controlling the mirror position. By using, accurate color shift correction can be performed with an inexpensive configuration, and an image with high print quality can be obtained.

The invention according to claim 5 of the present invention has means for changing the optical path of the exposure means, and by installing only a plurality of light receiving parts, all the colors including the scanning curve can be formed inexpensively. By detecting a shift error component, an image with high print quality can be obtained.

According to a sixth aspect of the present invention, a light receiving element capable of sufficiently responding to the scanning speed of the light by the exposure means and having a maximum light receiving area is used in the light receiving portion, so that the tolerance in optical design is reduced. A large design is possible, accurate color misregistration correction can be performed, and an image with high print quality can be obtained.

According to the seventh aspect of the present invention, it is possible to accurately detect a deviation from a reference by using an exposure unit serving as a reference color for color deviation correction as an exposure unit used as a light source for color deviation detection. Thus, accurate color shift correction can be performed, and an image with high print quality can be obtained.

According to an eighth aspect of the present invention, the exposing means used as a light source for detecting a color misregistration uses an exposing means serving as a reference color for color misregistration correction, and a registration pattern of another color is formed at a predetermined angle. By detecting the number, the time required for color misregistration detection can be reduced, and the toner consumption can be significantly reduced.

According to the ninth aspect of the present invention, the amount of toner consumption can be suppressed by using a registration pattern having a predetermined thickness using an exposure unit.

Hereinafter, an embodiment of the present invention will be described. FIG. 1 is a side view showing a mechanism for changing an optical path of an exposure unit according to an embodiment of the present invention. In the figure, the transport direction is A
I will show you.

In FIG. 1, at the time of image formation, a laser beam 5 from the exposure means 1 forms a latent image on the photosensitive means 9 and is developed to transfer the image onto a transmissive conveying belt or an intermediate transfer means 13. Similarly, laser beams 6, 7, and 8 are emitted from the exposure units 2, 3, and 4, respectively.
A latent image is formed on 0, 11 and 12, and is developed and the image is transferred onto a transmissive conveyor belt or intermediate transfer means 13. When the detection is performed, as shown in FIG. 2, the movable mirror 15 is moved by the distance X in a state where the registration pattern has already been formed on the transmissive transport belt or the intermediate transfer body 13.

The laser beam 6 emitted from the exposure means 2 is reflected by a moving mirror 15 and further reflected by a fixed mirror 16, passes through a transmissive conveyor belt or an intermediate transfer body 13, and is irradiated on a light receiving sensor 17.

The timing at which the transferred registration pattern blocks the laser beam 6 is detected, the amount of deviation is calculated from the difference between the detected timings of the respective colors, and correction is performed.

In this way, the color shift can be detected by using the exposure means without separately providing the conventional color shift detector 14 having an expensive laser.

FIG. 2 is a diagram showing a configuration for changing the optical path of the exposure means using the stepping motor according to one embodiment of the present invention. When the movable mirror 15 is moved by the distance X shown in FIG. 2, a stepping motor 18 is used for a driving portion. By using a stepping motor, the moving distance can be managed by the number of steps, so that an inexpensive configuration and a design with a large optical tolerance can be achieved.

The moving mirror 15 moves by a distance X from a standby position for forming an image to a position for detecting a color misregistration pattern each time, and monitors the output of the light receiving sensor for each detection. Adjustments need to be made. Therefore, when moving, the laser light 6 is once received by the light receiving sensor 17 and the distance to the detection position, that is, the number of steps is stored. Thereafter, the stepping motor 18 is rotated by a predetermined number of steps corresponding to the distance X, and the moving mirror 1 is rotated.
5 is moved to the position at the time of detection. With this method, it is not necessary to perform position adjustment every time detection is performed, and time can be reduced.

When an image is formed and when a color misregistration pattern is detected, a driving means for moving the movable mirror 15 and a driving means for image formation are switched between transmitting and non-transmitting to the moving mirror 15. By using a clutch or the like, an inexpensive image forming apparatus can be realized by sharing an existing driving force.

FIG. 3 is a diagram showing a sensor arrangement according to an embodiment of the present invention. The laser light emitted from the exposure means for detecting the color shift pattern draws a straight line in the scanning direction. Focusing on this, a plurality of light receiving sensors are arranged on a scanning straight line as shown in FIG.

FIG. 4 is a diagram showing sensor output values according to one embodiment of the present invention. In the related art, one light-emitting element requires one light-receiving sensor. However, by adopting the above-described method, any number of light-receiving sensors can be arranged at an arbitrary position on a scanning straight line. be able to. When the color misregistration pattern passes over the plurality of light receiving sensors, the voltage waveform of the sensor output changes as shown in FIG.

FIG. 5 is a diagram showing a sensor arrangement according to an embodiment of the present invention. Specifically, when the black toner passes over the light-receiving sensor 19 shown in FIG. 5, the output of the sensor changes, and t19k is calculated from the start and end of the change.
Is calculated. Similarly, t20k is calculated when passing over the light receiving sensor 20, and tnk is calculated when passing over the sensor n. The same line that should normally pass at the same time, from the time difference detected by each sensor,
The position of the toner, that is, the color shift of the toner can be detected.

By using a plurality of light-receiving sensors as described above, the scanning curvature which is difficult to detect in the conventional configuration can be improved.
Can be detected.

Since the light-receiving sensor only needs to have a laser incident on the light-receiving surface, the use of a sensor having a large light-receiving area can expand the allowable mounting range.

FIG. 6 is a view showing a mechanism for changing the optical path of the exposure means according to one embodiment of the present invention. As shown in FIG. 6, it is possible to mount the light receiving sensor with a width less than twice (distance D) the width of the light receiving sensor. Specifically, in the case of a 5 mm square sensor, there is an allowable mounting range up to a range of less than 10 mm.

If an exposure means other than the reference color is selected for detection, it is necessary to convert the exposure means into a shift of the reference color, which causes an accumulation of errors. Therefore, as shown in FIG. 6, in performing correction from among all colors to the exposure means used for detection, by selecting an exposure means of a reference color, detection lines of other colors can be detected with high accuracy. It becomes possible. Specifically, Black is used as a reference for both monochrome and color printing.

Further, the deviation in the main scanning direction, the deviation in the sub-scanning direction, the deviation in magnification, and the deviation in skew can be reduced by a predetermined angle of 45 degrees.
Detection can be performed with a predetermined number of color shift patterns.

FIG. 7 is a diagram showing a color misregistration pattern position and a sensor output timing according to an embodiment of the present invention. As shown in FIG. 7, an image formed on the conveyor belt or the intermediate transfer body 13 is detected using laser light from the exposure unit. Light receiving sensor 19 and light receiving sensor 2 arranged in the scanning direction
0,. . . , And light enters the light receiving sensor n in this order.

FIG. 9 is a diagram showing sensor output values of a color misregistration pattern of each color according to an embodiment of the present invention. In FIG. 9, while detecting a BLACK pattern, in order,
,... Are repeated.

In the scanning, the time when the light enters the left end of the light receiving sensor 19 is t19b, and the time when the light is off the right end is t19b.
e.

From t19b to t19e, the sensor output goes high. 45 degree BRAC on the way
When the K pattern is on the sensor and the laser beam is blocked, the time t corresponding to the width W19k of the pattern in the scanning direction is obtained.
The output becomes low by w19k. Similarly, the output of the light receiving sensor 20 is low only for the time tw20k corresponding to the width W20k, and the output of the light receiving sensor n is low only for the time twnk corresponding to the width Wnk.

Similarly, when detecting the Cyan pattern,
When detecting the pattern of Magenta in the order of ',', ',..., And in detecting the pattern of Yellow, in the order of'','','',.
Scanning is repeated in the order of ''',''',''', ....

The deviation of the main scanning is detected for each color from the time when the laser beam starts to be incident on one sensor until the time when the laser light is blocked by the toner, and the time difference between the reference color and the other colors in the main scanning direction is detected. The shift amount is calculated.

More specifically, the time from when light starts to enter the light receiving sensor 19 by scanning until the light is started to be blocked by the black toner is t19k. The time until the start of blocking is represented by t19c '.

At this time, the time corresponding to the shift amount of Black and Cyan in the main scanning direction is expressed by (Equation 1) t19k-t19c '.

Scan and 'scan, scan and' scan. . . Similarly, the time difference corresponding to the shift amount in (1) can be expressed as (Equation 2) t19k-t19c '(Equation 3) t19k-t19c' (Equation 4) t19kp-t19cp '.

By multiplying the average value of these values by a prescribed scanning speed, the amount of deviation between Black and Cyan in the main scanning direction can be calculated.

Similarly, Black and Magenta
Can be calculated from the following equation: (Equation 5) t19k-t19m ″ (Equation 6) t19k-t19m ″ (Equation 7) t19k-t19m ″ (Equation 8) t19kp-t19mp ′ '.

The amount of deviation between Black and Yellow in the scanning direction can be calculated from the following equation: (Equation 9) t19k-t19y '''(Equation 10) t19k-t19y''' (Equation 11) t19k-t19y '''(Equation 12) t19kp-t19yp'''

If the pattern cannot be detected in one scan due to the state of the image forming apparatus, the calculation can be performed by excluding the scan start p and the scan end p.

The shift in the sub-scanning direction is calculated by calculating the toner passing time.

FIG. 8 is a layout diagram of a sensor and a color misregistration pattern according to an embodiment of the present invention. As shown in FIG. 8, the time t19k at which the black toner starts to pass on the scanning line
From time b, a time t19ke until the passage is completed is detected. Thereafter, an intermediate value t19k between the two times is calculated by the following equation.

(Equation 13) t19k = (t19kb + t19ke) / 2 Similarly, Cyan, Magenta, Yellow
Can be calculated as in the following equation.

(Equation 14) t19c = (t19cb + t19ce) / 2 (Equation 15) t19m = (t19mb + t19me) / 2 (Equation 16) t19y = (t19yb + t19ye) / 2 If there is no color shift in the sub-scanning direction, Black Cyan, Magenta, Y
The “ellow” pattern is detected at specified intervals.

The time interval between the black toner and the cyan toner is calculated by using the above equation as (Equation 17) t19c−t19k. By comparing this with the specified time interval, the color shift amount in the sub-scanning direction is detected. can do.

Black and Magenta, Black
Similarly, for Yellow and Yellow, the color shift amount can be detected from (Equation 18) t19m-t19k (Equation 19) t19y-t19k.

Further, the magnification deviation can be quantified by calculating the distance from the toner on the light receiving sensor 19 to the toner on the sensor n for each color. The t1
Assuming that a time t19ke at which the scanning light deviates from the light receiving sensor 19 during the scanning of 9k and a time tnkb at which the scanning light starts to enter the sensor n, a time interval thk between the toner of the light receiving sensor 19 and the sensor n is calculated by the following equation. Is done.

(Equation 20) thk = tnkb-t19ke This is the magnification serving as the reference for Black.

Similarly, Cyan, Magenta,
For Yellow, thc, thm, and thy can be calculated as follows.

(Equation 21) thc = tncb-t19ce (Equation 22) thm = tnmb-t19me (Equation 23) thy = tnyb-t19ye Thus, from (Equation 20) and (Equation 21), the magnification of Cyan to Black is given by the following equation: It is represented by

(Equation 24) (tncb-t19ce) / (tnkb-t19ke) Similarly, for Genta for Black and Yellow for Black, (Equation 25) (tnmb-t19me) / (tnkb-t19ke) (Equation 26) (Tnyb-t19ye) / (tnkb-t19ke). In this manner, the magnification for the reference color can be detected, and the image quality can be improved by performing the correction.

FIG. 10 is a diagram showing a color shift pattern and the direction of scanning light according to an embodiment of the present invention. FIG. 11 is a diagram showing sensor output values according to one embodiment of the present invention. FIG.
FIG. 3 is a diagram illustrating the sizes of detection light and color misregistration patterns according to an embodiment of the present invention. The deviation of the skew is detected as follows. If the skew does not occur, the width of the toner in the main scanning direction is detected as W0. As shown in FIG. 10, when a skew of angle θ1 occurs, the width Wθ1
(= W0 · cos θ1). This W0 and Wθ
From the difference of 1, it is possible to calculate the tilt angle θ1.
Similarly, in the case of the angle θ2, the skew angle θ2 can be calculated from the difference from W0. The sensor output waveform at the time of actual detection changes as shown in FIG. 11, and is calculated at times TW0, TWθ1, and TWθ2 corresponding to the respective widths.

As described above, the detection line is one line of 45 degrees / one of a plurality of light receiving sensors.
It is possible to detect color misregistration in the main scanning direction, the sub-scanning direction, the magnification, and the skew using only the color.

Further, in the conventional color misregistration detecting section, since the irradiation beam is as large as several hundred μm, it is necessary to make the toner larger than the beam diameter. FIG. 12A shows a conventional relationship between the beam diameter and the toner.

(Equation 27) (100 μm) ≦ D1 ≦ W1 By using the laser light from the exposure means such as LSU, the irradiation range is about several tens of μm, and it is necessary to detect the toner position by blocking the laser light. Should have more toner. Therefore, the width of the toner used for detection is several tens of μm.
Defined in FIG. 12B shows the relationship between the beam diameter and the toner according to an embodiment of the present invention.

(Equation 28) D2 ≦ W2 (≦ 100 μm) By using a pattern having a specified width according to the laser beam used for detection, the toner consumption can be remarkably suppressed.

[0061]

As described above, according to the present invention, an exposure means such as an LSU, a means for moving an optical path from the exposure means, a photosensitive means on which an image is formed by light from the exposure means, a transmission means, Image bearing member such as a transfer belt or an intermediate transfer member, and light receiving means for receiving the light emitted from the exposure means and passing through the transfer means, by detecting the color misregistration pattern with high accuracy. In addition, color shift correction can be performed accurately and in a short time, and an image with high print quality can be obtained.

[Brief description of the drawings]

FIG. 1 is a side view showing a mechanism for changing an optical path of an exposure unit according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration in which an optical path of an exposure unit is changed using a stepping motor according to an embodiment of the present invention.

FIG. 3 is a sensor layout according to an embodiment of the present invention.

FIG. 4 is a diagram showing a sensor output value according to an embodiment of the present invention;

FIG. 5 is a sensor layout according to an embodiment of the present invention.

FIG. 6 is a diagram showing a mechanism for changing an optical path of an exposure unit according to an embodiment of the present invention.

FIG. 7 is a diagram showing a color shift pattern position and a sensor output timing according to the embodiment of the present invention;

FIG. 8 is a layout diagram of a sensor and a color shift pattern according to an embodiment of the present invention.

FIG. 9 is a diagram showing sensor output values of a color shift pattern of each color according to the embodiment of the present invention;

FIG. 10 is a diagram showing a color shift pattern and a direction of scanning light according to the embodiment of the present invention.

FIG. 11 is a diagram showing a sensor output value according to an embodiment of the present invention.

FIG. 12 is a diagram showing detection light and the size of a color misregistration pattern according to an embodiment of the present invention;

FIG. 13 is a configuration diagram showing a conventional color misregistration detection method.

[Explanation of symbols]

 1, 2, 3, 4 Exposure means 5, 6, 7, 8 Laser light 9, 10, 11, 12 Photosensitive means 13 Intermediate transfer means 14 Color shift detection unit 15 Moving mirror 16 Fixed mirror 17 Light receiving sensor 18 Stepping motor 19, 20 Light receiving sensor

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) G03G 15/04 (72) Inventor Seio Watanabe 1006 Oojidoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. ( 72) Inventor Kohei Suyama 1006 Kadoma, Kazuma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. BA66 BA68 BA71 BA83 BA90 BB29 BB30 CA22 CA23 CA39 DA03 DA09 2H027 DE02 DE07 EA02 EB04 EC03 EC04 EC06 EC09 EE04 EE08 2H030 AA01 AB02 AD16 BB02 BB12 BB56 2H076 AB02 EA06 EA16

Claims (9)

[Claims] 1. An image forming apparatus comprising: an exposure unit; a unit for changing an optical path of the exposure unit; and a transmissive image carrier, wherein a light source for detecting a color shift is shared with the exposure unit. 2. The apparatus according to claim 1, further comprising means for changing an optical path of the exposure means, wherein a mirror is used for changing the optical path, a stepping motor is used for controlling the mirror position, and a moving distance can be managed by the number of steps. Image forming apparatus. 3. The image forming apparatus according to claim 1, further comprising means for storing the number of steps of a stepping motor, which is a means for moving the mirror, and for managing a moving distance of the mirror. 4. An image forming apparatus comprising: means for changing an optical path of the exposure means; and driving means for forming an image.
2. The image forming apparatus according to claim 1, wherein a clutch and said driving means are used for mirror position control. 5. An image forming apparatus according to claim 1, further comprising means for changing an optical path of said exposure means, wherein only a plurality of light receiving portions are provided. 6. An image forming apparatus according to claim 1, wherein a light receiving element capable of sufficiently responding to a scanning speed of light by an exposure means and having a maximum light receiving area is used for said light receiving section. 7. An image forming apparatus according to claim 1, wherein an exposing means used as a reference color for color misregistration correction is used as the exposing means used as a light source for detecting the color misregistration. 8. A method of detecting a registration pattern of another color at a predetermined angle and a predetermined number by using an exposure unit serving as a reference color for color registration correction as an exposure unit used as a light source for the color registration detection. The image forming apparatus according to claim 1. 9. An image forming apparatus according to claim 1, wherein a registration pattern having a predetermined thickness is used by using said exposure means.