JP2000098810A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cope with both the fine adjustment and the coarse adjustment of deviated registration amount without making a detector for reading a registration deviation detection pattern large. SOLUTION: This image forming device is equipped with a pattern forming means for forming a registration deviation detection pattern M consisting of a 1st line segment M1 arranged at a specified angle to a processing direction being the moving direction of the surface of an image carrier and a 2nd line segment M2 arranged symmetrically by putting a virtual line orthogonal to the processing direction between the line segments M1 and M2 as an image on the image carrier, a pattern reading means for reading the line segments M1 and M2 formed on the image carrier in order at a specified position, and a registration deviation detecting means for detecting deviated registration amount based on the read result.

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 an image and outputting the image on a medium such as a recording sheet, such as a copying machine, a printer, a facsimile, and the like.

[0002]

2. Description of the Related Art In recent years, as an image forming apparatus, in order to output a color image at a high speed, for example, as shown in FIG. 11, a black (K) image is formed along an intermediate transfer belt 1 which is an endless belt-shaped image carrier. ), Yellow (Y), magenta (M), and cyan (C) are widely known as a so-called tandem type in which four image output units 2a to 2d corresponding to respective colors are provided. However, in the tandem type image forming apparatus, since one color image is formed by superimposing images of each color on the intermediate transfer belt 1, each image output unit 2
When the image transfer positions in a to 2d are relatively shifted, a registration shift of each color (hereinafter, simply referred to as “registration shift”) occurs, and the output image quality is deteriorated. Therefore, such an image forming apparatus generally has a function for detecting registration deviation and a registration correction function for correcting an image formation position and the like based on the detection result.

Various techniques have been conventionally proposed for realizing the function of detecting a registration shift. For example, as shown in FIG. 12, the start of exposure scanning on the intermediate transfer belt 1 is started. Scan; hereinafter referred to as SOS)
A registration error detection pattern 3 for detecting a registration error of each of the image output units 2a to 2d is formed on the side of the scan and on the end of scanning (hereinafter referred to as EOS). Is read by a detector 4 provided along the intermediate transfer belt 1 to detect a registration deviation amount.

Further, as a registration shift detection pattern formed on the intermediate transfer belt 1 at this time, for example, there is a pattern disclosed in Japanese Patent Application Laid-Open No. 6-118735. As shown in FIG. 13, the registration misregistration detection pattern includes a first chevron mark KK1, KK2 formed by a reference color and a second chevron mark MM formed by a measurement target color different from the reference color.
1, MM2, and the third chevron mark KM formed of both colors
1, KM2.

When such a registration shift detection pattern is formed on the intermediate transfer belt 1, the registration shift detection pattern is provided on each detector 4, and is substantially aligned along the chevron of each mark. Are read in order by a pair of photocells D1 and D2 arranged in a U-shape, and based on the reading time in each of the photocells, calculations are performed using functions shown in equations (1) and (2) described later to obtain a reference color. The amount of registration deviation between the color and the color to be measured is detected.

[0006] Here, the registration shift amount includes a process direction shift amount _Perr and a lateral direction shift amount _Lerr . The process direction deviation amount P _err refers to a registration deviation amount generated in a traveling direction of the surface of the intermediate transfer belt 1 (hereinafter, referred to as a process direction). The lateral direction deviation amount L _err is a direction perpendicular to the traveling direction of the surface of the intermediate transfer belt 1 (hereinafter, referred to as a direction).
(Referred to as lateral direction).

The process direction deviation amount P _err is determined by the first angle mark KK1 and the second angle mark MM by the photocell D1.
Set the detection intervals of the first and third chevron marks KM1 to T
_1A, T _{1 B,} first chevron KK2 by photocell D _2,
Second chevron MM2 and third respectively T _2A the detection interval of the chevron _KM2, and T _2B, when the moving speed of the intermediate transfer belt 1 surfaces is V, determined by the following equation.

_Perr = {(T _2A + T _2B ) − (T _1A + T _1B ) −0.5 × (T _2A −T _1A )} × V (1)

Similarly, the lateral direction shift amount L _err is also obtained by the following equation.

L _err = 0.5 × (T _2A −T _1A ) × V (2)

However, as for the lateral direction shift amount L _err , the magnitude of the detectable shift amount is determined by the photocells D 1 and D 1.
2, the detection range of the lateral deviation L _err is ± SW / 2, where SW is the arrangement interval.
Becomes That is, the lateral deviation L _err generated beyond the arrangement interval of the photocells D1 and D2 cannot be detected. Therefore, the photocells D1, D
Reference numeral 2 is arranged in accordance with the lateral displacement L _err to be detected, that is, the magnitude of the lateral displacement L _err expected to occur.

[0012]

By the way, the amount of registration deviation (process direction deviation amount P _err and lateral direction deviation amount L _err ) that can occur in an image forming apparatus can be roughly classified into slight registration corrections (fine adjustments). ), There is a registration shift amount that requires large registration correction (coarse adjustment). The amount of registration deviation that can be dealt with by fine adjustment is, for example, a deviation that can be caused by a change with time, a temperature change, a disturbance, or the like in each module such as an exposure device, a photoconductor, and an image carrier belt after performing a registration correction once. The amount is a maximum of about ± several hundred μm. On the other hand, the registration deviation amount that requires coarse adjustment is a deviation amount that can occur at the time of assembling or installing the image forming apparatus, at the time of maintenance replacement of the module, and the like, considering the dimensional tolerance of each part and the mounting accuracy thereof. It is about ± several mm.

On the other hand, in the above-described prior art, the magnitude of the lateral deviation L _{err that} can be detected depends on the arrangement interval of the photocells D1 and D2. Therefore, when the arrangement interval of the photocells D1 and D2 corresponds to the detection of only the lateral direction shift amount L _{err that} can be handled by fine adjustment, specifically, a shift amount of about ± several hundred μm is detected. When the photocells D1 and D2 are installed at intervals of about 1 to 2 mm, the lateral direction deviation L _err that requires coarse adjustment cannot be detected.

Further, by increasing the arrangement interval of the photocells D1 and D2, the lateral direction shift amount L
_If both the _err and the lateral deviation L _err that require coarse adjustment can be detected, for example, 10 mm is required to detect a lateral deviation L _err of about ± 5 mm.
A certain arrangement interval is required, resulting in an increase in the size of the detector 4 having these photocells D1 and D2.

Therefore, the present invention provides a registration error detection pattern for detecting a registration error amount by providing a feature.
An object of the present invention is to provide an image forming apparatus capable of coping with both fine adjustment and coarse adjustment without increasing the size of a detector that reads the registration deviation detection pattern.

[0016]

SUMMARY OF THE INVENTION The present invention is directed to an image forming apparatus devised to achieve the above object, comprising: an image carrier which is driven to rotate in a predetermined direction; and an image forming device which forms an image on the image carrier. An image output unit, a first line segment disposed at a predetermined angle to a process direction that is a moving direction of the image carrier surface as an image on the image carrier, and a virtual line orthogonal to the process direction. A pattern forming means for forming, on the image output portion, a registration shift detection pattern composed of a second line segment symmetrically arranged with the first line segment with the image carrier interposed therebetween. A pattern reading unit that sequentially reads the first line segment and the second line segment of the registration misalignment detection pattern formed at a predetermined position, and the first line segment and the second line that are read by the pattern reading unit. Based on minute reading It is characterized in further comprising a misregistration detecting means for detecting a registration deviation amount of the image output unit.

According to the image forming apparatus having the above-described structure, the pattern forming means forms the registration deviation detecting pattern composed of the first line segment and the second line segment on the image carrier, and the pattern reading means forms the first line segment. And the second line segment are sequentially read at a predetermined position. Thus, the registration deviation detecting unit can compare the reading interval between the first line segment and the second line segment by the pattern reading unit with a predetermined value or the like so that the amount of deviation in the registration deviation detecting pattern can be determined. Become. At this time, the pattern reading means need only read at a predetermined position. In addition, if the first line segment and the second line segment are within the range passing through the predetermined position, the registration deviation detecting means can detect the deviation regardless of the magnitude of the deviation amount.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described with reference to the drawings.

[Outline Description] First, an outline of a registration error detection pattern which is a feature of the present invention will be briefly described. In this embodiment, the image output unit forms a registration misregistration detection pattern on the intermediate transfer belt, similarly to the related art. FIG. 1 is a conceptual diagram illustrating an example of a registration shift detection pattern formed in the image forming apparatus according to the present invention.

As shown in the figure, the registration misregistration detection pattern M is orthogonal to the first line segment M1 arranged at a predetermined angle θ with respect to the process direction of the intermediate transfer belt and the process direction of the intermediate transfer belt. And a second line segment M2 symmetrically arranged with the first line segment M1 with the virtual line interposed therebetween. It is assumed that the first line segment M1 and the second line segment M2 are formed by the same image output unit (same color).

The registration misregistration detection pattern M is a detector (not shown) provided at a predetermined pattern detection position, specifically, a position having a predetermined relationship with a registration misregistration detection pattern (shown by a broken line) in an ideal state. ). Therefore, when the intermediate transfer belt moves in the process direction, the registration deviation detection pattern M formed on the intermediate transfer belt is such that the first line segment M1 is at timing A and the second line segment M2 is at timing B. , Respectively. Note that the pattern detection position may be an intermediate position in the lateral direction of the registration error detection pattern in the ideal state.

Here, assuming that the distance from the reference point preset on the intermediate transfer belt to timing A is DA, and the distance from the reference point to timing B is DB, the lateral deviation amount of the registration deviation detection pattern M is L _err corresponds to the difference between DA and DB since the first line segment M1 and the second line segment M2 are symmetrically arranged. That is, DA and DB when the registration deviation detection pattern in the ideal state is read.
Is the difference from DW, the lateral deviation L _err is
It is obtained by the following equation (3).

L _err = {(DB−DA−DW) × 0.5} × tan θ (3)

At this time, if the detector is installed at a laterally intermediate position of the registration deviation detection pattern in the ideal state, the DW is the length of the first line segment M1 or the second line segment M2.
Specified by multiplying by osθ.

On the other hand, the deviation amount P _{err in} the process direction of the registration deviation detection pattern M with respect to the detector is also represented by DA and D.
B. That is, the timing A when the registration deviation detection pattern in the ideal state is read
_Assuming that P _nom is an intermediate timing between the reference point and the timing B and DP _nom is a distance from the reference point to the timing P _nom , the process direction deviation amount P _err is symmetric between the first line segment M1 and the second line segment M2. Are obtained by the following equation (4).

P _err = 0.5 × (DB + DB) −DP _nom (4)

That is, a registration misregistration detection pattern M including a first line segment M1 and a symmetric second line segment M2 is formed, and is read by a detector at a predetermined position.
Equation (3), it is possible to determine the process direction deviation amount P _err and lateral shift amount L _{er r} by (4).

[Explanation of Specific Example] Next, the case where the present invention is applied to an image forming apparatus such as a copying machine will be specifically described. FIG. 2 is a conceptual diagram showing a registration shift detection pattern formed in the image forming apparatus of the present embodiment. In the drawing, it is assumed that a solid line indicates a registration misregistration detection pattern actually formed, and a broken line indicates a registration misregistration detection pattern in an ideal state.

The image forming apparatus of this embodiment has four image output units 2a to 2d arranged along an intermediate transfer belt 1 which is an endless belt-shaped image carrier, similarly to the conventional one. It is a so-called tandem type (see FIG. 11).
However, this image forming apparatus includes a control unit (not shown) including a CPU (Central Processing Unit) for controlling the entire apparatus, and the control unit controls the image output units 2a to 2d. An instruction to form the registration error detection pattern M is given, and the amount of registration error is detected based on the result of reading the registration error detection pattern M.

As described above, the registration deviation detecting pattern M formed by the control unit is composed of the first line segment M1 and the symmetric second line segment M2. However, FIG.
As shown in FIG. 1, the first line segment M1 and the second line segment M2 are each substantially 4 ° with respect to the process direction of the intermediate transfer belt 1.
It has an angle of 5 degrees, and can cope with both a misregistration amount of about several hundred μm that can be handled by fine adjustment and a misregistration amount of, for example, about 5 mm that requires coarse adjustment. For this purpose, it is assumed that the size of the first line segment M1 and the second line segment M2 in the lateral direction is, for example, about 15 mm.

The control unit, as in the prior art, stores the registration deviation detection pattern M between the SOS side on the intermediate transfer belt 1 and the E.
It is assumed that it is formed on the OS side (see FIG. 12). That is, two registration deviation detection patterns M are formed on the intermediate transfer belt 1 in the lateral direction.

The pattern M for detecting registration deviation formed on the intermediate transfer belt 1 in this manner is
It is read by the detectors 4 provided corresponding to the OS side and the EOS side (see FIG. 12).

Each detector 4 is used to improve reading accuracy.
Similar to the conventional one (disclosed in JP-A-6-118735), each of them has a pair of photocells D1 and D1.
It consists of a so-called split (bicell) type detector having D2. However, each of these photocells D1 and D2 is arranged in an approximately figure-eight shape, and one of them is arranged in the process direction along the first line segment M1 by approximately 45 °.
It is assumed that they are installed with an angle of degrees and the other is installed symmetrically with the one along the second line segment M2. In addition,
The detector 4 may be one in which CCDs (Charge Coupled Devices) are arranged symmetrically at a certain angle.

Further, as described above, each of the detectors 4 is installed at a position having a predetermined relationship with the registration deviation detection pattern in the ideal state. More specifically, in each detector 4, the intermediate position between the photocells D1 and D2 matches the lateral intermediate position when the registration error detection pattern to be read is in an ideal state.

In such a detector 4, when the intermediate transfer belt 1 moves in the process direction at the belt speed V, as shown in FIG.
, And the photocell D2 reads the second line segment M2 at the timing B.

Here, the time from the timing (reference timing) at which the reference point on the intermediate transfer belt 1 passes through the photocells D1 and D2 to the timing A is TA, the time from the timing B is TB, and the process direction is TB. The pattern reference timing (center timing of the registration error detection pattern in an ideal state) is P _nom , the lateral size of the registration error detection pattern M is W, and the distance between the photocells D1 and D2 is When SW is set, the lateral displacement L _err and the process displacement P _err of the registration displacement detection pattern M are symmetric with respect to the first line segment M1 and the second line segment M2, and are substantially both in the process direction. Since they are arranged with an angle of 45 degrees, the following equation (5),
It is obtained by an operation using the function shown in (6).

L _err = {V × (TB−TA) −W} × 0.5 (5)

_Perr = {0.5 × (TB + TB) −SW / 2−P _nom } × V (6)

The control unit calculates the process direction deviation amount P
When seeking _err and lateral shift amount L _{er r,} by giving an instruction to the image output unit 2a~2d so as to correct such a result forming position of the image based on, to prevent degradation of output quality I do.

As described above, in the image forming apparatus according to the present embodiment, the first line segment M1
Misregistration detection pattern M including the second line segment M2
Is formed on the intermediate transfer belt 1, and the first line segment M1 and the second line segment M2 are sequentially read by the photocells D1 and D2 provided at predetermined positions, whereby the process in the registration misregistration detection pattern M is performed. Direction deviation amount P
_err and a lateral direction shift amount _Lerr are detected. At this time, in particular, the lateral direction deviation amount L _err
As can be seen from equation (5), the detectable range does not depend at all on the arrangement interval SW of the photocells D1 and D2.

Therefore, in this image forming apparatus, regardless of the size of the arrangement interval SW of the photocells D1 and D2,
It is possible to detect both the amount of registration deviation that can be handled by fine adjustment and the amount of registration deviation that requires coarse adjustment. That is, the detection area of the amount of registration deviation can be expanded without increasing the size of the detector 4.

In addition, in this image forming apparatus, the first line segment M1 and the second line segment M2 in the registration error detection pattern M are formed by the same image output unit (same color). By detecting the amount of registration deviation based on M, not the relative registration deviation between the images formed by the image output units 2a to 2d, but the absolute deviation in the images formed by the image output units 2a to 2d. The displacement can be understood. For this reason, control when performing registration correction according to the detection result of the registration deviation amount can be facilitated, and detection of only one image output unit can be performed independently.

Further, in the image forming apparatus of the present embodiment,
As in the invention described in claim 2, the photocell D1 is installed along the first line segment M1, and the photocell D2 is installed symmetrically along the second line segment M2. In this image forming apparatus, the range of the detectable registration deviation amount does not depend on the arrangement interval SW of the photocells D1 and D2.
For example, it is conceivable to read the first line segment M1 and the second line segment M2 at the same location by using a sensor or the like in which a photodiode and a phototransistor are combined. However, as in the present embodiment, the detector 4 is provided with a pair of photocells D1 and D2, and the photocell D1 uses the first line segment M1.
If the second line segment M2 is read by the photocell D2, the reading accuracy can be improved as compared with the case where the same portion is used, and the detector 4 which has been conventionally used for detecting the registration error can be obtained. Can be used as it is.

[Explanation of Correction of Magnification Deviation in Specific Example] Incidentally, a magnification deviation in the lateral direction may occur in the registration deviation detection pattern formed by the control unit in each of the image output units 2a to 2d. The magnification shift in the lateral direction refers to an image formed on the intermediate transfer belt 1.
This means that a shift (distortion) occurs in the magnification in the lateral direction, and as a result, the image is deformed.

Here, the outline of the lateral magnification shift will be described with reference to FIG. FIG. 3 shows a registration shift detection pattern when a magnification shift in the lateral direction occurs. In the figure, the one-dot chain line indicates the registration error detection pattern MA in the ideal state, the broken line indicates the registration error detection pattern MB in the case where a lateral magnification shift occurs in the ideal state, and the solid line indicates the registration error detection pattern MB. Is a registration deviation detection pattern MC in the case where a lateral positional deviation and a magnification deviation occur.

In this image forming apparatus, as can be seen from equation (5), when calculating the amount of registration deviation in the lateral direction, the center interval W of the registration deviation detection pattern MA in the ideal state is calculated.
Is used to match the lateral size W of the registration deviation detection pattern MA. However, in the registration deviation detection pattern MB in which the magnification deviation has occurred, the center interval W does not match the size W ′ in the lateral direction.
As a result, an error is included in the registration shift amount calculated using the equation (5). That is, in the registration shift detection pattern MC in which both the position shift and the magnification shift occur, even if the registration shift amount is calculated using Expression (5), the actual lateral direction shift amount L _err and the calculation result are obtained. Is different from the lateral direction shift amount L _err 2. The relationship between these is that L _err = α × L, where the shift magnification is α.
_err 2

Therefore, in this image forming apparatus, in order to correct this error, the control unit first calculates the lateral shift amount without considering the magnification shift, and then calculates the temporary scale shift amount from the calculation result. The true lateral deviation L _err is calculated by correcting the already calculated lateral deviation using the provisional magnification deviation, and calculating the true lateral deviation L _err .

The correction by the control unit is performed as follows. In this image forming apparatus, as shown in FIG. 4, two registration misregistration detection patterns are formed on the SOS side and the EOS side on the intermediate transfer belt 1. At this time, the true lateral displacement on the SOS side / EOS side is LS _err / LE _err , and the provisional lateral displacement including the magnification displacement is LS _err 2 / LE, respectively.
_err 2 and the detector 4 on the SOS side and the detector 4 on the EOS side
Is the SE width, the provisional magnification shift amount MagT between the SOS side and the EOS side is obtained by the following equation (7).

MagT = (LE _err 2 −LS _err 2) ÷ SE Width + 1 (7)

Then, based on the provisional magnification deviation MagT and the provisional lateral deviation LS _err 2 / LE _err 2,
The true lateral direction shift amount LS _err / LE _err is obtained by an operation using the functions shown in the following equations (8) and (9).

LS _err = LS _err 2 × MagT (8)

LE _err = LE _err 2 × MagT (9)

The true magnification Mag is given by the following equation (10).
Required by

Mag = (LE _err −LS _err ) ÷ SE Width + 1 (10)

Therefore, in obtaining the lateral deviation L _err , the control unit first obtains TA and T by photocells D1 and D2 on the SOS side and the EOS side as shown in the flowchart of FIG.
B (step 101; hereinafter, step is abbreviated as S), and from the detection result, a provisional lateral direction shift amount LS _err 2 / LE having a magnification effect on the SOS side / EOS side.
_err 2 is calculated (S102).

After calculating LS _err 2 / LE _err 2, the control unit calculates the provisional magnification deviation MagT based on these values using the above-described equation (7) (S 103). Then, the control unit calculates the true lateral direction shift amount LS _err / LE _err by performing correction using the provisional magnification shift amount MagT using the above equations (8) and (9) (S1).
04).

As described above, in the image forming apparatus according to the present embodiment, the SOS side and the E
From the reading result of the registration shift detection pattern with the OS side, the magnification shift MagT of the registration shift detection pattern is calculated, and the correction by the magnification shift MagT is performed to calculate the true lateral direction shift amount LS _err / LE _err. Has become. Therefore, the image forming apparatus can detect the true amount of registration deviation even when a magnification deviation in the lateral direction occurs in the registration deviation detection pattern. That is, it is possible to improve the detection accuracy of the registration deviation amount, particularly in the lateral direction.

[Explanation of Skew Misregistration Correction in Specific Example] In addition, a skew misregistration occurs in a registration misregistration detection pattern formed by the control unit in each of the image output units 2a to 2d in addition to a lateral magnification misalignment. Sometimes.
The skew shift means that an image formed on the intermediate transfer belt 1 has a certain inclination.

Here, an outline of the skew deviation will be described with reference to FIG. FIG. 6 shows a registration shift detection pattern when a skew shift occurs. In the drawing, the one-dot chain line indicates the registration deviation detection pattern MA 'in the ideal state, the broken line indicates the registration deviation detection pattern MB' in the case where a positional deviation in the process direction due to the skew deviation has occurred, and the solid line indicates the solid line. What is shown is a registration misregistration detection pattern MC 'when a misalignment in the process direction occurs due to a misalignment in the lateral direction and a skew.

In this image forming apparatus, when calculating the amount of registration deviation in the process direction, the first line segment and the second line segment in the registration deviation detection pattern are arranged symmetrically, and the intermediate between timing A and timing B is calculated. The fact that the timing P _nom corresponds to the intersection of the first line segment and the second line segment is used. Therefore, in the registration shift detection pattern MC ′ in which both the skew shift and the position shift occur, even if the registration shift amount is calculated using the above-described equation (6), the actual process direction shift amount P _err and the actual process direction shift amount P _err are calculated. An error occurs between the calculated result and the process direction deviation amount P _err2 . This error increases in proportion to the lateral displacement, and no error occurs when the lateral displacement _Lerr is "0". That is, the relationship between them is as follows: when the inclination of the skew is β, _Perr = _Perr2 −β × _Lerr
Becomes

Therefore, in this image forming apparatus, in order to correct this error, the control unit first calculates the process direction shift amount without considering the skew shift, and then calculates the temporary skew shift amount from the calculation result. The true process direction deviation amount P _err is obtained by calculating and correcting the already calculated process direction deviation amount with the provisional skew deviation amount.

The correction by the control unit is performed as follows. As shown in FIG. 7, the true process direction deviation amounts on the SOS side / EOS side are respectively represented by PS _err / PE.
_err and the lateral direction shift amount are respectively LS _err / LE
_Assuming that _err and the tentative process direction shift amount including the error due to the skew shift are PS _err 2 / PE _err 2 respectively,
The provisional skew slope SkewT between the SOS side and the EOS side is
It is obtained by the following equation (11).

SkewT = (PE _err 2 −PS _err 2) ÷ SE Width (11)

Then, the provisional skew inclination SkewT is calculated as follows:
From the provisional process direction shift amount PS _err2 / PE _err 2 and the lateral direction shift amount LS _err / LE _err , the true process direction shift amount PS _err / PE _err is _calculated by the following equation (1).
It is obtained by an operation using the functions shown in 2) and (13).

PS _err = PS _err 2 −LS _err × SkewT (12)

PE _err = PE _err 2 −LE _err × SkewT (13)

The true skew slope Skew is obtained by the following equation (14).

Skew = (PE _err −PS _err ) ÷ SE Width (14)

Therefore, in obtaining the process direction deviation amount P _err , the control unit first sets the TA and T by the photocells D1 and D2 on the SOS side and the EOS side as shown in the flowchart of FIG.
B (S201), and the SOS side /
A provisional process direction shift amount PS _err 2 / PE _err 2 having a skew effect on the EOS side is calculated (S20).
2).

After calculating PS _err 2 / PE _err 2, the control unit calculates a temporary skew deviation amount SkewT using the above equation (11) based on these values (S 20).
3). Then, the control unit calculates the above equations (12) and (13).
Is corrected by the provisional skew shift amount SkewT, thereby real process direction shift amount PS _err / PE _err.
Is calculated (S204).

As described above, according to the image forming apparatus of the present embodiment, the SOS side and the E
The skew deviation amount SkewT of the registration deviation detection pattern is calculated from the result of reading the registration deviation detection pattern with the OS, and the true process direction deviation amount PS _err / PE _err is calculated by correcting the skew deviation amount SkewT. It has become. Therefore, this image forming apparatus can detect the true amount of registration deviation even when a skew deviation occurs in the registration deviation detection pattern. That is, it is possible to improve the detection accuracy of the registration deviation amount, particularly in the process direction.

[Description of Registration Deviation Detection Patterns Formed by Plurality of Image Output Units] Next, the arrangement of the registration deviation detection patterns formed by the control unit on the four image output units 2a to 2d will be described. In this image forming apparatus, four image output units 2 a to 2 d are arranged along the intermediate transfer belt 1. Therefore, the control unit controls each of the image output units 2a to 2
9D, a plurality of registration error detection patterns (patterns A to D) are formed on the intermediate transfer belt 1 as shown in FIG. 9A, for example.
It is arranged so that it is arranged in order in the process direction on the top. At this time, on the intermediate transfer belt 1, the control unit may make the registration misregistration detection patterns of the same color continue, or may arrange the registration misregistration detection patterns of each color alternately.

By arranging a plurality of registration error detecting patterns in the process direction in this way, in this image forming apparatus, a plurality of image output units 2a to 2d are provided. Is provided, the absolute positional deviation in the image formed by each of the image output units 2a to 2d can be sequentially determined for each color.

However, as shown in FIG. 9B, for example, the control unit may arrange the registration misregistration detection patterns such that the registration misregistration detection patterns adjacent to each other are in opposite directions. . In this case, for example, the registration misregistration detection patterns (patterns A to D) are alternately arranged for each color (pattern A is yellow, pattern B is magenta, and pattern C is pattern). The pattern occupation area in the process direction on the intermediate transfer belt 1 can be reduced even if a certain interval is required in consideration of the amount of registration deviation that can be allowed between the cyan and pattern D). Can be. Also,
Along with this, the frequency of the measurement can be given.

Further, when arranging a plurality of registration error detection patterns (patterns A to D) so as to be arranged in the process direction, the control unit, as shown in FIG. It is also conceivable to arrange them with. As the predetermined cycle at this time, for example, each of the image output units 2a to 2a
There is a cycle synchronized with the rotation of the photoconductor drum included in 2d. That is, the control unit arranges an integer number of registration misregistration detection patterns in a half of the photosensitive drum cycle, that is, in one cycle of the photosensitive drum.

With this configuration, even if there is a factor that causes periodic color registration deviation, such as the rotation frequency of the photosensitive drum due to the influence of eccentricity or the like, the image forming apparatus according to claim 7 As in the invention described above, the registration deviation amount can be detected without being affected by the periodic fluctuation in the intermediate transfer belt 1 due to the factor, and as a result, the detection accuracy can be improved. .

[0077]

As described above, according to the image forming apparatus of the present invention, the registration deviation detecting pattern including the first line segment and the second line segment is formed on the image carrier, and the first line segment is formed. The M1 and the second line segment are sequentially read at a predetermined position to detect the registration deviation amount. Therefore, in this image forming apparatus, if the first line segment and the second line segment are within a range passing through the predetermined position, the registration deviation amount can be detected regardless of the magnitude of the deviation amount.
That is, it is possible to expand the detection area of the amount of registration deviation without increasing the size of the pattern reading unit for reading the registration deviation detection pattern.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an example of a registration shift detection pattern formed in an image forming apparatus according to the present invention.

FIG. 2 is a conceptual diagram illustrating another example of a registration shift detection pattern formed in the image forming apparatus according to the present invention.

FIG. 3 is an explanatory diagram showing a specific example of a registration shift detection pattern when a magnification shift in a lateral direction occurs.

FIG. 4 is an explanatory diagram showing an example of a difference in magnification shift in the lateral direction between the SOS side and the EOS side.

FIG. 5 is a flowchart illustrating an example of a processing procedure for correcting a lateral direction shift amount due to a magnification shift of a registration shift detection pattern.

FIG. 6 is an explanatory diagram showing a specific example of a registration shift detection pattern when a skew shift occurs.

FIG. 7 is an explanatory diagram showing an example of a difference in skew deviation between the SOS side and the EOS side.

FIG. 8 is a flowchart illustrating an example of a processing procedure for correcting a process direction shift amount due to a skew shift of a registration shift detection pattern.

FIGS. 9A and 9B are explanatory diagrams (part 1) illustrating a specific example of a plurality of registration error detection patterns arranged in parallel in a process direction; FIG. 9A illustrates a case of arrangement in the same direction; It is a figure showing the case of direction arrangement.

FIG. 10 is a diagram (part 2) illustrating a specific example of a plurality of registration error detection patterns arranged in parallel in the process direction.

FIG. 11 is a schematic diagram illustrating an example of a tandem-type image forming apparatus.

FIG. 12 is an explanatory diagram illustrating an example of a configuration for detecting a registration deviation detection pattern formed on an intermediate transfer belt (image carrier).

FIG. 13 is an explanatory view showing an example of a conventional registration shift detection pattern.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Intermediate transfer belt, 2a-2d ... Image output part, 4 ... Detector, D1, D2 ... Photocell, M ... Registration shift detection pattern, M1 ... 1st line segment, M2 ... 2nd line segment

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Tsutomu Udaka 2274 Hongo, Ebina-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd. Ebina Works F-term (reference) 2H027 DA09 DE02 DE10 EB04 EB06 EC03 EC07 2H030 AA01 AB02 AD17 BB42 BB56

Claims (7)

[Claims] 1. An image carrier that is driven to rotate in a predetermined direction, an image output unit that forms an image on the image carrier, and an image on the image carrier in a moving direction of the surface of the image carrier. A registration misregistration detection pattern including a first line segment arranged at a predetermined angle with a certain process direction and a second line segment arranged symmetrically with the first line segment across a virtual line orthogonal to the process direction. A pattern forming means for forming the image output unit, when the image carrier is rotated, the first line segment and the second line segment of the registration deviation detection pattern formed on the image carrier, A pattern reading unit that sequentially reads at a predetermined position; and a registration deviation detecting unit that detects a registration deviation amount of the image output unit based on a reading result of the first line segment and the second line segment by the pattern reading unit. Specially to prepare An image forming apparatus. 2. The apparatus according to claim 1, wherein the pattern reading unit is provided symmetrically with the first detector provided at a predetermined angle with respect to the process direction, and symmetrically with the first detector across a virtual line along the process direction. The image forming apparatus according to claim 1, further comprising: a second detector that is provided. 3. The method according to claim 1, wherein the pattern forming unit forms a plurality of registration error detection patterns in a lateral direction that is a direction orthogonal to the process direction. It is provided at a plurality of locations corresponding to the pattern. Further, a magnification shift detection for detecting a magnification shift of the registration shift detection pattern in the lateral direction based on a result of reading by the pattern reading means at the plurality of places. 3. The image forming apparatus according to claim 1, further comprising: a unit, wherein the registration deviation detection unit corrects a detection result of the registration deviation amount based on a detection result by the magnification deviation detection unit. 4. The pattern forming means forms a plurality of registration error detection patterns in a lateral direction which is a direction orthogonal to the process direction, and the pattern reading means executes the plurality of registration error detection patterns. It is provided at a plurality of locations corresponding to the pattern, and further detects a skew amount in the lateral direction of the plurality of registration misregistration detection patterns based on a result of reading by the pattern reading means at the plurality of locations. 4. The image forming apparatus according to claim 1, further comprising skew amount detection means, wherein the registration error detection means corrects a detection result of the registration error amount based on a detection result by the skew amount detection means. apparatus. 5. The image forming apparatus according to claim 1, wherein, when a plurality of the image output units are provided, the registration error detection patterns formed by the image output units are arranged in the process direction on the image carrier. 5. The image forming apparatus according to claim 1, wherein the image forming apparatus is arranged. 6. The pattern forming means, when a plurality of registration error detection patterns are arranged in the process direction, form each registration error detection pattern such that adjacent registration error detection patterns are opposite to each other. 6. The image forming apparatus according to claim 1, wherein the image forming apparatus is arranged. 7. A printing apparatus according to claim 1, wherein said plurality of registration error detection patterns are arranged at predetermined intervals when a plurality of registration error detection patterns are arranged in said process direction. 7. The image forming apparatus according to 3, 4, 5 or 6.