JPH1035021A - Color imaging system with a plurality of recording heads - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color imaging system in which gap and overlap are eliminated from partial images being formed by adjacent recording heads at the time of printing with second and subsequent colors. SOLUTION: The imaging system comprises two recording heads 1, 2 arranged on the upstream side, and a recording head 5 arranged on the downstream side. Recording head groups 1, 2 on the upstream side are secured to a supporting member 3 while a recording head group 5 on the downstream side is secured to a supporting member 6 movable with respect to the supporting member 3. The supporting member 3 is movable with respect to a member 20 oscillating about a shaft 25. A section 9 for detecting resist marks 8 printed on the opposite sides of a recording member 30 is disposed on the upstream side of the recording heads 1, 2. An operating section 10 detects oblique advance of the recording member 30 based on information received from the detecting section 9 and controls the position of the supporting member 6, the position of the supporting member 3, and the orientation of the oscillating member 20 based on the detection results.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus for forming a wide image using a plurality of recording heads.

[0002] The recording heads to which the present invention is applied include:
Examples include an ion head and an electrostatic head that form an electrostatic latent image on a recording medium, a multi-nozzle inkjet head that forms an image by flying ink, and a thermal head that forms an image on thermal paper.

[0003]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 6-227027 discloses an image forming apparatus in which a plurality of recording heads are arranged in a main scanning direction while being divided into several groups in a sub-scanning direction, and recording paper is reciprocated to superimpose each color image. Is disclosed. With this apparatus, a large-screen color image can be obtained while using a single-size recording head that is easy to manufacture.

Japanese Patent Application Laid-Open No. 4-298355 discloses that a plurality of recording heads are divided into several groups in the sub-scanning direction, and recording heads adjacent to each other in the main scanning direction are overlapped by one dot or more, and the recording paper is reciprocated. Discloses an image forming apparatus that superimposes each color image. In this device, generation of a gap in the main scanning direction is prevented.

Japanese Patent Publication No. 1-52753 discloses an image forming apparatus that tracks a registration mark formed on a recording medium and translates and rotates a recording head. In this apparatus, even if the recording medium is skewed, each color image can be superimposed following the registration mark.

Japanese Patent Application Laid-Open No. Hei 7-266630 discloses that two recording heads are arranged in the main scanning direction, and the recording heads are similarly translated and rotated to cope with skew of a recording medium.
A device capable of superimposing each color image is disclosed.

Japanese Patent Application Laid-Open No. Hei 7-266630 discloses that the center of rotation of a recording head is set at an intermediate portion between the main scanning direction and the sub-scanning direction in order to make the difference in density between adjacent boundaries of the recording heads arranged in the main scanning direction inconspicuous. Discloses a method of providing the same. Thereby, even if the recording head swings in accordance with the skew of the recording paper, the gap between the two recording heads and the recording paper becomes equal, and the boundary can be made inconspicuous.

Japanese Patent Application Laid-Open No. 7-266630 discloses an image forming apparatus in which two recording heads are arranged in the main scanning direction while being shifted in the sub-scanning direction, and registration marks are printed at both ends of the image to notify the printing positions of the second and subsequent colors. Has been disclosed.

[0009]

Problems to be Solved by the Invention Japanese Patent Laid-Open No. Hei 6-22702
No. 7 and JP-A-4-298355, a plurality of recording heads are arranged in the main scanning direction while being divided into several groups in the sub-scanning direction, and a registration mark and an image are printed together in the first color. However, in this case, the following points cannot be dealt with.

(1) If the recording paper is skewed during the recording of the first color, adjacent recording heads that are separated in the sub-scanning direction and adjacent in the main scanning direction have a gap in the skewed direction. Or overlap, and dark streaks can be seen.

(2) In this state, if the prints of the second and subsequent colors are moved by moving the position of the recording head while tracking the registration mark or the print position is adjusted while shifting the print position by an electric signal, an overlapping portion is formed. However, the image overlaps twice as much as the other portions, and appears as a dark streak.

The present invention has been made by paying attention to this point. An object of the present invention is to print an image and a registration mark together in the first color so that even if skew occurs, the nth color (n: In the case of an integer of 2 or more, before printing, the skew amounts of the first color and the nth color are detected based on the distance between the registration marks, and the upstream and downstream recording head groups are moved mechanically or printed by electrical signals. The purpose of the present invention is to provide a color image forming apparatus using a plurality of print heads that makes adjacent print head boundaries inconspicuous by shifting the print head.

Japanese Patent Publication No. 1-52753 and JP-A-7-26
In the apparatus of No. 6630, when the recording head is moved in the main scanning direction by the registration mark detection signal during printing, the recording heads separated in the sub-scanning direction are also moved. It is not possible to cope with the point that gaps and overlapping portions occur in the parts. In other words, there is a time difference between the dots printed by the upstream recording head and the dots printed by the downstream recording head with respect to the dots on the same line in the main scanning direction. In other words, the dots on the same line in the main scanning direction are printed on the recording paper after the area corresponding to the upstream recording head is printed by the upstream recording head, A range corresponding to the downstream printhead is printed by the downstream printhead at intervals of time until the printhead reaches the printhead. Therefore, when the upstream recording head and the downstream recording head are simultaneously moved in the main scanning direction according to the skew of the recording paper, a partial image printed by the upstream recording head and the downstream recording head Gaps and overlaps occur with the partial image to be printed.

The present invention has been made in view of this point, and an object of the present invention is to provide a recording head in the main scanning direction by a registration mark detection signal during printing even when a recording head separated in the sub-scanning direction is used. An object of the present invention is to provide a color image forming apparatus using a plurality of recording heads in which a gap or an overlap does not occur at a boundary between adjacent recording heads even when the recording head is moved.

The apparatus disclosed in Japanese Patent Application Laid-Open No. Hei 7-266630 can cope with a case where two heads are used. However, when three or more recording heads are arranged, the boundary becomes plural and the center of rotation is set. Can not.

The present invention has been made in view of this point, and an object of the present invention is to provide a color image forming apparatus using a plurality of recording heads in which a density difference does not occur at a boundary between adjacent recording heads. It is.

In the apparatus disclosed in JP-A-7-266630, the two recording heads for printing the registration marks are separated in the sub-scanning direction. Since the corresponding paper feed fluctuation amount is included, it is not possible to determine whether the paper is skewed or the paper feed fluctuation at the time of registration mark printing when detecting the second color.

The present invention has been made by paying attention to this point. It is an object of the present invention to use a plurality of recording heads which do not include fluctuations in paper feed when printing registration marks at the left and right ends. It is an object to provide an image forming apparatus. Further, even if the registration marks formed at both ends of the image are separate recording heads, the skew generated in the first color when recording the registration mark or the skew generated before the start of the recording of the second color. It is an object of the present invention to provide a color image forming apparatus using a plurality of recording heads capable of judging whether a color image is formed.

[0019]

According to the present invention, there is provided a color image recording apparatus which divides a plurality of recording heads into two or more groups in a sub-scanning direction, performs recording in a main scanning direction, and superimposes each color image. Means for shifting the recording position of the entire upstream recording head in the main scanning direction while maintaining the mutual recording position of the upstream recording head group; and downstream recording while maintaining the mutual recording position of the downstream recording head group. Means for shifting the recording position of the entire head group in the main scanning direction with respect to the upstream recording head group, and a swing mechanism in which the upstream recording head group and the downstream recording head group are mounted so as to be rotatable in the main scanning direction. Moving means, a registration mark provided on the recording medium, a detection means for detecting the registration mark, an arithmetic means for calculating the conveyance state of the recording medium from the position of the registration mark, and a calculation means for calculating the conveyance state of the recording medium. Calculating means for calculating the amount of shift in the main scanning direction of the print position of the entire upstream print head group and the amount of shift in the main scan direction of the entire print position of the downstream print head group with respect to the upstream print head group; The registration mark is printed at the time of recording of the first color, and the recording of the nth color is performed at the printing position of the first color based on the conveyance state of the recording paper calculated from the registration mark detected at the recording of the nth color (n is an integer of 2 or more). The recording position of the entire upstream recording head group is shifted in the main scanning direction so as to overlap, and the recording position of the entire downstream recording head group is so set that the end of the downstream recording head group substantially coincides with the end of the upstream recording head group. Are shifted in the main scanning direction.

According to the present invention, there is provided another color image recording apparatus which divides a plurality of recording heads into two or more groups in the sub-scanning direction, performs recording in the main scanning direction, and superimposes each color image. Means for shifting the recording position of the entire upstream recording head group in the main scanning direction while maintaining the mutual recording position of the group; and the entire downstream recording head group while retaining the mutual recording position of the downstream recording head group. Means for shifting the recording position in the main scanning direction with respect to the upstream recording head group, and oscillating means capable of mounting the upstream recording head group and the downstream recording head group and rotating in the main scanning direction. A registration mark provided on a recording medium, detection means for detecting the registration mark, calculation means for calculating a conveyance state of the recording medium from the position of the registration mark, and recording upstream of the conveyance state of the recording medium. A first-color recording unit for calculating a shift amount in the main scanning direction of the print position of the entire print group and a shift amount in the main scan direction of the print position of the entire downstream print head group with respect to the upstream print head group. At this time, a registration mark is printed so that the recording of the n-th color (n is an integer of 2 or more) overlaps the printing position of the first color based on the conveyance state of the recording paper calculated from the registration mark detected at the time of recording. The recording position of the entire upstream recording head group is shifted in the main scanning direction, and the recording position of the entire downstream recording head group is shifted in the main scanning direction with a time delay when the recording medium moves from the upstream head group to the downstream head group. The feature is to shift to.

The above color image forming apparatus is preferably
Both ends of the image are recorded by the recording heads at both ends of the most upstream group, and the registration marks are recorded by the most upstream recording head provided outside the image.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] A first embodiment of a color image forming apparatus using a plurality of recording heads according to the present invention will be described with reference to FIGS.

[Configuration] As shown in FIGS.
The image forming apparatus has two recording heads 1 and 2 arranged on the upstream side and one recording head 5 arranged on the downstream side. Each of the recording heads 1, 2, and 5 has a number of pixel forming portions arranged in the main scanning direction, and each of the pixel forming portions prints one pixel. For example, a nozzle corresponds to a nozzle in an ink jet head. I do. The pixel forming portions of the upstream recording heads 1 and 2 and the pixel forming portion of the downstream recording head 5 are adjacent to each other without overlapping in the main scanning direction. Is activated to print.

Although the image forming apparatus of this embodiment has a total of three recording heads, the number is not limited to this, and the number of recording heads on the upstream side is three or more. The number of the downstream recording heads may be two or more. In view of such circumstances, in the present specification, the upstream recording head is generally referred to as an upstream recording head group, and the downstream recording head is generally referred to as a downstream recording head group. When the upstream print head and the downstream print head are collectively referred to, they are simply referred to as a print head group.

The upstream recording head groups 1 and 2 are fixed to a supporting member 3, and the downstream recording head group 5 is fixed to a supporting member 6. The support member 6 is provided movably with respect to the support member 3. In other words, one end of the support member 6 contacts the elastic member 14 fixed to the support member 3,
The other end is in contact with the drive shaft of the drive source 7 fixed to the support member 3, and is moved in the longitudinal direction of the support member 3 by the advance / retreat operation of the drive shaft of the drive source 7. The drive source 7 is formed of, for example, a stepping motor whose drive shaft moves forward and backward according to the number of input steps.

The support member 3 is provided so as to be movable with respect to a swing member 20 which is swingably provided around a shaft 25. That is, one end of the support member 3 is
Abuts on the elastic member 13 fixed to the
It is in contact with the drive shaft of the drive source 4 fixed to 0, and is moved in the longitudinal direction of the swinging member 20 by the reciprocating operation of the drive shaft of the drive source 4. The drive source 4 is formed of, for example, a stepping motor whose drive shaft advances and retreats according to the number of input steps.

As shown in FIGS. 2 and 3, the swing member 2
Numeral 0 is opposed to the platen member 28 at a predetermined interval, and the recording member 30 is passed through the gap between them. Swing member 2
One end of the 0 and the platen member 28 are both connected to the shaft 25, and the other end is fixed to each other via a connecting portion 29, whereby the relative posture between the two is kept unchanged. .

As shown in FIG. 1, one end of the end of the swinging member 20 located on the opposite side of the shaft 25 abuts against the elastic member 18 fixed to the apparatus main body, and the other side has an opposite side. The drive member 17 is in contact with the drive shaft of the drive source 17 fixed to the main body of the apparatus.
The platen member 28 and the platen member 28 are integrally swung about the shaft 25. The drive source 17 is composed of, for example, a stepping motor whose drive shaft advances and retreats according to the number of input steps.

Upstream of each of the recording heads 1 and 2, a detecting section 9 for detecting the registration marks 8 printed on both sides of the recording member 30 is provided one by one. The detection unit 9 is configured by, for example, a line sensor such as a CCD. The image forming apparatus determines the recording member 30 based on the information from the detection unit 9.
, A drive control unit 11 for controlling the drive source 4 in accordance with a command from the calculation unit 10, and a calculation unit 10.
Control unit 1 for controlling drive source 7 in accordance with a command from
2. It has a drive control unit 19 that controls the drive source 17 according to a command from the arithmetic unit 10. The platen 28
Is cylindrical and is configured to rotate as the recording member 30 passes.

[Operation] A color image is formed by printing images of a plurality of colors on the recording member 30 in order.

When forming the first color image, the first color image is printed on the recording member 30 and the registration marks 8 are printed on both sides of the recording member 30. The registration mark 8
It serves as an index of the printing position when forming an image of a specific color after the second color. In the present specification, such image formation of a specific color after the second color is referred to as image formation of the nth color. Here, n is an integer of 2 or more, usually 4 or less.

At the time of forming the n-th color image, prior to printing,
The registration mark 8 is detected by the detection member 9, and the skew state at the time of forming the first color image and the skew state at the time of forming the nth color image are checked by the arithmetic unit 10 based on the information.

If skew is detected during the formation of the first color image, the support member 6 is moved in the main scanning direction to eliminate the gap and overlap between partial images printed by adjacent recording heads. One correction operation is performed.

When the skew of the n-th color image is detected, the swinging member 20 is swung to make the main scanning direction of the recording head group coincide with the main scanning direction of the first color image. The operation is performed.

Thereafter, the support member 3 is appropriately moved in the main scanning direction with reference to the registration mark 8, and the n-th color image is printed on the recording member 30.

Hereinafter, the skew determination will be described with reference to FIGS.

As shown in FIGS. 4 and 5, when there is no skew during the formation of the first color image, no gap or overlap occurs at the boundary between the images printed by the adjacent recording heads.

On the other hand, as shown in FIGS. 6 and 7, when there is a skew during the formation of the first color image, a gap or overlap exists at the boundary between the images printed by the adjacent recording heads. Occurs.

The presence / absence and skew angle of the skew when forming the first color image and the presence / absence and skew angle of the skew when forming the nth color image are represented by n
And time difference Δt when the both sides of the tip of the registration mark 8 at the time of image formation of the color passes through the detection unit 9, and the distance L _x between the opposite sides of the registration mark 8, the feeding speed of the recording member 30 V
and _p, is determined based on the distance L ₀ on both sides of the resist 8 when the skew is not.

If L _x = L ₀ , it is determined that there is no skew in both the first color image formation and the nth color image formation (see FIG. 4).

If L _x = (L ₀ ² + (V _p Δt) ² ) ^1/2, it is determined that there is no skew when forming the first color image, but there is skew when forming the nth color image. , The skew angle θ _n at the time of image formation for the n-th color is θ _n = arcsin (V _p Δt
/ L _x ) (see FIG. 5).

If L _x <(L ₀ ² + (V _p Δt) ² ) ^1/2 , it is determined that there is skew when forming the first color image, but there is no skew when forming the n color image. , The skew angle θ ₁ at the time of image formation of the first color is θ ₁ = arctan (V _p Δt
/ L _x ) (see FIG. 6).

If L _x > (L ₀ ² + (V _p Δt) ² ) ^1/2 , it is determined that there is a skew in both the image formation of the first color and the image formation of the n-th color. The skew angle θ ₁ at the time of forming an image of a color is θ ₁ = arccos (L _x / V _p Δt · (1
− ((L _x ² − (V _p Δt) ² ) / 2L ₀ L _x ) ² )
The skew angle θ _n at the time of forming an image of ^1/2 , nth color is θ _n = ar
^{_{ccos ((L x 2 - (}} V p Δt) 2) / 2L 0 L x)
(See FIG. 7).

As described above, when the image of the n-th color is formed,
Before the upstream recording head groups 1 and 2 start printing, the arithmetic unit 10 obtains the skew angle θ ₁ for forming the _first color image and the skew angle θ _n for forming the n-th color image. the first correction operation in accordance with the value of ₁ is performed, followed by a second correction operation according to the value of theta _n is performed. The order in which the first correction operation and the second correction operation are performed is not limited to this, and the first correction operation may be performed after the second correction operation.

Hereinafter, the correction operation and the subsequent printing operation will be described with reference to FIGS. FIG. 11 is a flowchart of a series of the operation.

As shown in FIG. 8, when skew occurs during the formation of the first color image, a gap or overlap occurs between partial images printed by adjacent recording heads. The width δ _{1 of the} gap is equal to the width δ ₂ of the overlap, and the skew angle θ at that time
_{Using 1} and the distance Y between the upstream recording head group and the downstream recording head group, δ ₁ = δ ₂ = Ytan θ ₁ .

In the first correction operation, as shown in FIG. 9, in order to eliminate the overlap with the gap, the width δ (= δ ₁₎
= Δ ₂ ), the downstream print head group 5 is moved relative to the upstream print head groups 1 and 2 in the main scanning direction. The relative movement of the recording head group 5 is performed by moving the support member 6 using the drive source 7.

As shown in FIG. 10, when skew occurs during the formation of the nth color image, the main scanning direction of the first color image and
An error occurs between the print head group and the main scanning direction.

In the second correction operation, in order to make the main scanning direction of the image of the first color coincide with the main scanning direction of the recording head group,
An angle equal to skew angle theta _n, group recording head 1 and 2 and 5 are rotated. That is, the recording head groups 1, 2 and 5 have a skew angle θ with respect to a direction in which the main scanning direction is orthogonal to the paper feeding direction.
Tilt by an angle equal to _n . The recording head groups 1, 2, and 5 are rotated by rotating the swing member 20 using the drive source 4.

After the first correction operation and the second correction operation are completed, the printing position of the n-th color image is adjusted based on the registration mark 8 printed when forming the first color image, and the n-th color image is adjusted. The printing of the image is started. During the formation of the nth color image, the registration mark 8 is tracked by the detection unit 9, and the printing position of the nth color image is adjusted one by one according to the position of the registration mark 8. To adjust the printing position, the support member 3 on which the recording head groups 1, 2 and 5 are mounted is driven by the driving source 4.
It is performed by moving using.

[Effect] Since the downstream recording head group 5 is moved mechanically, the occurrence of gaps and overlaps of about several microns is also prevented. Therefore, the image forming apparatus of the present embodiment can be applied to the fields of printing and photography where high definition images are required.

Since the relative positional relationship between the swinging member 20 and the platen member 28 is kept unchanged without being affected by the rotation of the recording head groups 1, 2 and 5, recording in the main scanning direction is performed. The intervals between the head groups 1, 2, and 5 and the recording paper 30 are always kept constant, and an image having a uniform density is formed.

Further, the recording heads 1 and 2 on both sides of the upstream recording head group are located on the same straight line extending in the main scanning direction, and the registration marks are recorded on the recording heads 1 and 2 on both sides.
Therefore, printing is always performed at the same position on both sides of the recording member without being affected by fluctuations in the paper feed speed.

[Second Embodiment] A second embodiment of a color image forming apparatus using a plurality of recording heads according to the present invention will be described with reference to FIGS. In the second embodiment, the print position adjustment of the downstream recording head group for the first correction operation in the first embodiment is performed by shifting data.

[Configuration] As shown in FIG. 12, the upstream recording head groups 1 and 2 and the downstream recording head group 21 are fixed to the support member 3, and the support member 3 is movable to the swing member 20. It is provided in. The support member 3 has one end in contact with the elastic member 13 fixed to the swing member 20 and the other end in contact with the drive shaft of the drive source 4 fixed to the swing member 20. The pivoting member 20 is moved in the longitudinal direction by the reciprocating operation of the shaft. As a result, the upstream recording head groups 1 and 2 and the downstream recording head group 21 are appropriately moved in the main scanning direction while maintaining their relative positional relationship unchanged. The drive source 4 is formed of, for example, a stepping motor whose drive shaft advances and retreats according to the number of input steps.

Each of the recording heads 1, 2, and 21 has a number of pixel forming portions arranged in the main scanning direction. Each of the pixel forming portions prints one pixel. The nozzle corresponds. The pixel forming portions of the upstream recording heads 1 and 2 and the pixel forming portion of the downstream recording head 21 partially overlap with each other in the main scanning direction. When the printing is performed, the recording head 21 on the downstream side prints by selectively operating a part of a predetermined range of the pixel forming portion.

As in the first embodiment (see FIGS. 2 and 3), the oscillating member 20 faces the platen member 28 at a predetermined interval, and the recording member 30 is provided between the two members. Passed. The swinging member 20 and the platen member 28 have one end connected to the shaft 25 and the other end fixed to each other via a connecting portion 29, so that the relative posture between the two remains unchanged. I'm dripping.

As shown in FIG. 12, one end of the end of the swing member 20 located on the opposite side of the shaft 25 abuts against the elastic member 18 fixed to the apparatus main body, and the opposite side has an end. The drive member 17 is in contact with the drive shaft of the drive source 17 fixed to the main body of the apparatus.
The platen member 28 and the platen member 28 are integrally swung about the shaft 25. The drive source 17 is composed of, for example, a stepping motor whose drive shaft advances and retreats according to the number of input steps.

Upstream of each of the recording heads 1 and 2, a detection unit 9 for detecting the registration marks 8 printed on both sides of the recording member 30 is provided. The detection unit 9 is configured by, for example, a line sensor such as a CCD. The image forming apparatus determines the recording member 30 based on the information from the detection unit 9.
, A drive control unit 11 for controlling the drive source 4 in accordance with a command from the calculation unit 10, and a calculation unit 10.
Control unit 1 that controls drive source 17 in accordance with an instruction from
9, a control unit 22 that controls the printing range of the downstream recording head group 21 by shifting data in accordance with a command from the arithmetic unit 10.

[Operation] A color image is formed by printing a plurality of color images sequentially on the recording member 30.

At the time of forming the first color image, the first color image is printed on the recording member 30, and at the same time, the registration marks 8 serving as indicators of the printing position at the time of forming the nth color image are printed on both sides of the recording member 30. You.

At the time of forming the n-th color image, prior to printing,
The registration mark 8 is detected by the detection member 9, and the skew state at the time of forming the first color image and the skew state at the time of forming the nth color image are checked by the arithmetic unit 10 based on the information.

When the skew of the first color image is detected, the data in the print range of the downstream recording head group 21 is shifted in the main scanning direction, and the partial image of the partial image printed by the adjacent recording head is shifted. A first correction operation for eliminating the gap and overlap between them is performed.

When the skew of the n-color image is detected, the swing member 20 is swung to make the main scanning direction of the recording head group coincide with the main scanning direction of the first color image. The operation is performed.

Thereafter, the support member 3 is appropriately moved in the main scanning direction with reference to the registration mark 8, and an n-th color image is printed on the recording member 30.

The determination of skew in the arithmetic unit 10 is performed in the same manner as in the first embodiment. Since this has already been described, its description is omitted.

At the time of forming the n-th color image, the skew angle θ ₁ at the time of forming the _first color image and the oblique angle θ at the time of forming the n-th color image before the upstream recording head groups 1 and 2 start printing. line angle theta _n is determined, the first correction operation according to the value of theta ₁ is performed,
Followed by a second correction operation according to the value of theta _n is performed.
The order of the first correction operation and the second correction operation is not limited to this, and the first correction operation may be performed after the second correction operation.

Hereinafter, the correction operation and the subsequent printing operation will be described with reference to FIGS. FIG. 13 and FIG.
In FIG. 4, one pixel forming portion is schematically represented by one circle, a pixel forming portion that performs a printing operation is indicated by a black circle, and a pixel forming portion that does not perform a printing operation is indicated by a white circle.

As shown in FIG. 13, the print areas of the upstream print head 1 and the downstream print head 21 overlap the width H ₁ , and the upstream print head 2 and the downstream print head 21 are overlapped. print range is wide H ₂ overlap.

If skew occurs during the formation of the first color image, a gap or overlap occurs between partial images printed by adjacent recording heads. Gap width δ ₁ and overlap width δ ₂
Using the skew angle θ _{1 at} that time and the distance Y between the upstream recording head group and the downstream recording head group, δ ₁ = δ ₂
= Y tan θ ₁ .

In the first correction operation, as shown in FIG. 14, the width δ (= δ
₁ = δ ₂ ), the operating image forming unit in the downstream recording head group 21 is changed. That is, the range of the operating image forming unit in the downstream recording head group 21 is shifted in the main scanning direction. The control unit 22 changes the pixel forming unit that operates as described above.

Following the first correction operation, a second correction operation is performed. The second correction operation is performed in the same manner as in the first embodiment. That is, in the second correction operation, to match the main scanning direction in the main scanning direction and the recording head group of the first color image, an angle equal to the skew angle theta _n, group recording head 1, 2, and 21 is rotated You. Recording head groups 1, 2, and 21
Is performed by rotating the swinging member 20 using the drive source 4.

After the first correction operation and the second correction operation are completed, the printing position of the n-th color image is adjusted based on the registration mark 8 printed at the time of forming the first color image, and the n-th color image is adjusted. The printing of the image is started. During the formation of the nth color image, the registration mark 8 is tracked by the detection unit 9, and the printing position of the nth color image is adjusted one by one according to the position of the registration mark 8. The adjustment of the printing position is performed by moving the support member 3 on which the recording head groups 1, 2 and 21 are mounted using the driving source 4.

[Effect] Since a mechanism for mechanically moving the downstream recording head group is not required, the number of components can be reduced accordingly. Therefore, the image forming apparatus of the present embodiment is realized at lower cost than the apparatus of the first embodiment.

[Third Embodiment] A third embodiment of a color image forming apparatus using a plurality of recording heads according to the present invention will be described with reference to FIG. In the third embodiment,
In the first embodiment, the print position adjustment of the downstream recording head group related to the first correction operation and the print position adjustment of the recording head group related to registration tracking during printing are performed by shifting data.

[Structure] As shown in FIG. 15, the upstream recording head groups 31 and 32 and the downstream recording head group 38 are fixed to the swinging member 20, and their relative positional relationship remains unchanged. Is kept. Recording heads 31, 32 and 38
Have a large number of pixel forming portions arranged in the main scanning direction, and each of the pixel forming portions prints one pixel, and for example, corresponds to a nozzle in an ink jet head. Each of the recording heads 1, 2, and 21 has a number of pixel forming units arranged in the main scanning direction.
Each of them prints one pixel, and for example, corresponds to a nozzle in an ink jet head. The pixel forming portions of the upstream recording heads 31 and 32 and the pixel forming portion of the downstream recording head 38 partially overlap with each other in the main scanning direction. A part of the range is selectively operated for printing.

As in the first embodiment (see FIGS. 2 and 3), the oscillating member 20 faces the platen member 28 at a predetermined interval, and the recording member 30 is provided between the two members. Passed. The swinging member 20 and the platen member 28 have one end connected to the shaft 25 and the other end fixed to each other via a connecting portion 29, so that the relative posture between the two remains unchanged. I'm dripping.

As shown in FIG. 15, one end of the end of the swinging member 20 located on the opposite side of the shaft 25 abuts against the elastic member 18 fixed to the apparatus main body, and the opposite side has The drive member 17 is in contact with the drive shaft of the drive source 17 fixed to the main body of the apparatus.
The platen member 28 and the platen member 28 are integrally swung about the shaft 25. The drive source 17 is composed of, for example, a stepping motor whose drive shaft advances and retreats according to the number of input steps.

Upstream of each of the recording heads 31 and 32,
One detecting unit 9 for detecting the registration marks 8 printed on both sides of the recording member 30 is provided. Detector 9
Is constituted by a line sensor such as a CCD.
The image forming apparatus includes a calculation unit 10 that detects skew of the recording member 30 based on information from the detection unit 9, a drive control unit 19 that controls the drive source 17 in accordance with a command from the calculation unit 10, A control unit 33 that controls the printing position of the upstream recording head groups 31 and 32 by shifting the data according to a command, and a control unit 34 that controls the printing position of the downstream recording head group 38 by shifting the data according to a command from the arithmetic unit 10. have.

[Operation] A color image is formed by printing a plurality of color images sequentially on the recording member 30.

At the time of forming the first color image, the first color image is printed on the recording member 30, and the registration marks 8 serving as an index of the printing position at the time of forming the nth color image are printed on both sides of the recording member 30. You.

At the time of forming the n-th color image, prior to printing,
The registration mark 8 is detected by the detection member 9, and the skew state at the time of forming the first color image and the skew state at the time of forming the nth color image are checked by the arithmetic unit 10 based on the information.

When the skew of the first color image is detected, the data in the print range of the downstream recording head group 38 is shifted in the main scanning direction, and the partial image of the partial image printed by the adjacent recording head is shifted. A first correction operation for eliminating the gap and overlap between them is performed.

When the skew of the n-th color image is detected, the swing member 20 is swung to make the main scanning direction of the recording head group coincide with the main scanning direction of the first color image. The operation is performed.

Thereafter, the data in the printing range of the recording head groups 31, 32, and 38 is appropriately shifted in the main scanning direction with reference to the registration mark 8, and the n-th color image is printed on the recording member 30.

The determination of skew in the arithmetic unit 10 is performed in the same manner as in the first embodiment. Since this has already been described, its description is omitted.

At the time of forming the n-th color image, before the upstream recording head groups 31 and 32 start printing, the skew angle θ ₁ at the time of forming the _first color image and the skew angle at the time of forming the n-th color image are determined. Row angle θ _n
Is determined, the first correction operation according to the value of theta ₁ is performed, followed by a second correction operation according to the value of theta _n is performed. The order of the first correction operation and the second correction operation is not limited to this, and the first correction operation may be performed after the second correction operation.

The first correction operation is performed in the same manner as in the second embodiment. That is, in the first correction operation, in order to eliminate the gap and the overlap between the partial images recorded by the adjacent recording heads caused by the skew of the recording member 30, the gap corresponding to the gap and the overlap width δ is eliminated. The range of the operating image forming section in the downstream recording head group 38 is shifted in the main scanning direction. The control unit 34 shifts the range of the pixel forming unit that operates as described above.

After the first correction operation, a second correction operation is performed. The second correction operation is performed in the same manner as in the first embodiment. That is, in the second correction operation, to match the main scanning direction in the main scanning direction and the recording head group of the first color image, an angle equal to the skew angle theta _n, and the recording head group 31 32 and 38 are rotated You. Recording head groups 31 and 3
The rotation of 2 and 38 is performed by rotating the swing member 20 using the drive source 4.

After the first correction operation and the second correction operation are completed, the printing position of the n-th color image is adjusted based on the registration mark 8 printed at the time of forming the first color image, and the n-th color image is adjusted. The printing of the image is started. During the formation of the nth color image, the registration mark 8 is tracked by the detection unit 9, and the printing position of the nth color image is adjusted one by one according to the position of the registration mark 8. The adjustment of the printing position is performed by shifting the range of the pixel forming section in which the recording head groups 31, 32 and 38 operate as a whole in the main scanning direction while maintaining the mutual positional relationship. The overall shift of the range of the pixel forming section operating in this manner is controlled by the control section 33.
And the control unit 34 cooperate.

[Effects] A mechanism for mechanically moving the upstream recording head group and a mechanism for mechanically moving the downstream recording head are not required, so that the number of components is reduced accordingly. Therefore, the image forming apparatus according to the present embodiment is realized at a lower cost than the apparatus according to the second embodiment.

[Fourth Embodiment] A fourth embodiment of a color image forming apparatus using a plurality of recording heads according to the present invention will be described with reference to FIGS.

[Configuration] As shown in FIG. 16, the upstream recording head groups 1 and 2 are fixed to a support member 3,
The downstream recording head group 41 is fixed to a support member 48. The support member 3 and the support member 48 are provided movably independently of each other with respect to the swing member 20. That is, the support member 3 has one end in contact with the elastic member 13 fixed to the swing member 20 and the other end in contact with the drive shaft of the drive source 4 fixed to the swing member 20. The swinging member 20 is moved in the longitudinal direction by the reciprocating operation of the drive shaft 4. Similarly, the support member 48 has one end in contact with the elastic member 14 fixed to the swing member 20 and the other end in contact with the drive shaft of the drive source 46 fixed to the swing member 20. Source 46
The swinging member 20 is moved in the longitudinal direction by the advancing and retreating operation of the drive shaft. Both the driving source 4 and the driving source 46 are configured by, for example, stepping motors whose motor shafts advance and retreat according to the number of input steps.

Each of the recording heads 1, 2, and 41 has a number of pixel forming portions arranged in the main scanning direction. Each of the pixel forming portions prints one pixel. The nozzle corresponds. The pixel forming portions of the upstream recording heads 1 and 2 and the pixel forming portion of the downstream recording head 41 are adjacent to each other without overlapping in the main scanning direction. Is activated to print.

As in the first embodiment (see FIGS. 2 and 3), the oscillating member 20 faces the platen member 28 at a predetermined interval, and the recording member 30 is provided between the two members. Passed. The swinging member 20 and the platen member 28 have one end connected to the shaft 25 and the other end fixed to each other via a connecting portion 29, so that the relative posture between the two remains unchanged. I'm dripping.

As shown in FIG. 16, one end of the end of the swinging member 20 located on the opposite side of the shaft 25 abuts against the elastic member 18 fixed to the apparatus main body, and the opposite side has The drive member 17 is in contact with the drive shaft of the drive source 17 fixed to the main body of the apparatus.
The platen member 28 and the platen member 28 are integrally swung about the shaft 25. The drive source 17 is composed of, for example, a stepping motor whose motor shaft advances and retreats according to the number of input steps.

Upstream of each of the recording heads 1 and 2, a detection unit 9 for detecting the registration marks 8 printed on both sides of the recording member 30 is provided. The detection unit 9 is configured by, for example, a line sensor such as a CCD. The image forming apparatus determines the recording member 30 based on the information from the detection unit 9.
, A drive control unit 43 for controlling the drive source 4 in accordance with a command from the arithmetic unit 10, and an arithmetic unit 10.
Control unit 4 for controlling drive source 46 in accordance with an instruction from
2. It has a drive control unit 19 that controls the drive source 17 according to a command from the arithmetic unit 10.

[Operation] A color image is formed by printing a plurality of color images sequentially on the recording member 30.

At the time of forming the first color image, the first color image is printed on the recording member 30, and the registration marks 8 serving as indicators of the printing position when forming the nth color image are printed on both sides of the recording member 30. Is done.

At the time of forming the nth color image, prior to printing,
The registration mark 8 is detected by the detection member 9, and the skew state at the time of forming the first color image and the skew state at the time of forming the nth color image are checked by the arithmetic unit 10 based on the information.

When skew is detected during the formation of the first color image, the support member 48 is moved in the main scanning direction to eliminate the gap and overlap between the partial images printed by the adjacent recording heads. One correction operation is performed.

When the skew of the n-th color image is detected, the swinging member 20 is swung to make the main scanning direction of the recording head group coincide with the main scanning direction of the first color image. The operation is performed.

Thereafter, the n-th color image is printed on the recording member 30.

While the n-th color image is being printed, the registration mark 8 is constantly monitored by the detection unit 9. As long as the detection unit 9 does not detect the meandering of the registration mark 8, the recording head groups 1, 2, and 41 are maintained in the positional relationship after the first correction operation and the second correction operation are completed.

The meandering of the registration mark 8 means that the image of the first color has a distortion. Therefore, the registration mark 8
When the meandering is detected, the recording head groups 1, 2 and 41 are moved in the main scanning direction according to the meandering of the registration mark 8 in order to print the nth color image in accordance with the distorted first color image. And the print position is adjusted. At this time, the upstream recording head groups 1 and 2 and the downstream recording head group 4
It is moved at a time interval from 1.

Hereinafter, details of the adjustment of the print positions of the recording head groups 1, 2, and 41 will be described with reference to FIGS.

The tip of the displacement portion X ₁ of the registration mark 8 and the displacement δ thereof are detected by the detection portion 9. When the leading end of the displacement portion X ₁ has reached the upstream recording head group 1 and 2 as shown in FIG. 17, the driving source 4 is driven, the movement of the main scanning direction of the upstream recording head group 1 and 2 Be started. Also, the ends of the displacement portion X ₁ as shown in FIG. 18 when reaching the upstream recording head group 1 and 2, the driving source 4 is stopped, the upstream recording head group 1 and 2 in the main scanning direction The movement is terminated. The upstream recording head groups 1 and 2 have a displacement portion X ₁
Is moved by the displacement amount δ in the main scanning direction while passing through the upstream recording head groups 1 and 2.

Therefore, the partial image printed by the upstream recording head groups 1 and 2 is
Before moving is started, reference 17 numerals A ₁ and C ₁
As shown in FIG. 18, while the upstream recording head groups 1 and 2 are moved, reference numerals A ₂ and C ₂
In a parallelogram shape as shown, after the movement of the upstream recording head group 1 and 2 is completed, a rectangular shape as indicated by reference 19 numerals A ₃ and C _3.

[0110] On the other hand, after the state illustrated in FIG. 18, when the tip of the displacement portion X ₁ reaches the downstream recording head group 41, the drive source 46 is driven, the downstream recording head group 41
Is started in the main scanning direction. Also, the ends of the displacement unit X ₁ is downstream recording head group 41, as shown in FIG. 19
, The drive source 46 is stopped, and the movement of the downstream recording head group 41 in the main scanning direction is completed. Downstream recording head group 41, the displacement unit X ₁ is while passing through the downstream recording head group 41, the displacement amount in the main scanning direction [delta], is moved.

[0111] Thus, partial images to be printed by the downstream-side printing head group 41, before the movement of the downstream recording head group 41 is initiated, as indicated by reference numeral B ₁ in FIGS. 17 to 19 And the downstream recording head group 4
While 1 is moved, a parallelogram shape as indicated by reference numeral B ₂ in FIG. 19, after the movement of the downstream recording head group 41 is completed, although not shown in FIG rectangular It is.

By the above-described control operation, the rectangular partial image B ₁ printed by the downstream recording head group 41 before the movement of the downstream recording head group 41 is started is obtained by the upstream recording head groups 1 and 2. The rectangular partial images A ₁ and C ₁ printed by the upstream recording head groups 1 and 2 before the movement starts.
Are printed adjacent to each other without any gap or overlap. The parallelogram-shaped partial image B ₂ printed by the downstream recording head group 41 during the movement of the downstream recording head group 41 is shifted to the upstream side during the movement of the upstream recording head groups 1 and 2. The partial images A ₂ and C _{2 of} the parallelogram shape printed by the recording head groups 1 and 2 are printed adjacently without any gap or overlap. Furthermore, the rectangular partial image printed by the downstream recording head group 41 before the movement of the downstream recording head group 41 starts is changed before the movement of the upstream recording head groups 1 and 2 starts. Rectangular partial image A printed by 1 and 2
Against ₃ and C _3, it is printed adjacent without gaps or overlap occur.

FIG. 20 shows a time chart of this sequence. The time Δt ₁ from when the tip of the displacement portion X ₁ is detected by the detection unit 9 to when it reaches the upstream recording head groups 1 and 2 is the sub-scan between the detection unit 9 and the upstream recording head groups 1 and 2. Assuming that the interval in the direction is L ₁ and the speed of the recording member 30 is V _p , Δt ₁ = L ₁ / V _p . The time Δt ₂ from when the leading end of the displacement portion X1 is detected by the detection section 9 to when it reaches the downstream recording head group 41 is determined by the sub-scanning of the upstream recording head groups 1 and 2 and the downstream recording head group 41. Assuming that the interval in the direction is L ₂ , Δt ₂ = (L ₁ + L ₂ ) / V _p
Given by Therefore, based on the time when the leading end of the displacement portion X ₁ is detected by the detection unit 9, upstream recording head group 1 and 2 are started moving in the main scanning direction times Delta] t ₁ delay, the downstream recording head group At 41, the movement in the main scanning direction is started with a delay of time Δt ₂ .

As described above, the movement of the downstream recording head group is started after the movement of the upstream recording head group, so that a gap or overlap occurs between partial images printed by adjacent recording heads. The nth color image is printed without occurrence.

[Effect] Since the movement of the downstream recording head group is started after the movement of the upstream recording head group, the partial image to be printed while the recording head group is moved in the main scanning direction is obtained. The nth color image is printed without any gap or overlap between them.

[Fifth Embodiment] A fifth embodiment of a color image forming apparatus using a plurality of recording heads according to the present invention will be described with reference to FIG. In the fifth embodiment, the printing position of the downstream recording head group in the fourth embodiment is adjusted by shifting data.

[Configuration] As shown in FIG. 21, the downstream recording head group 51 is fixed to the swinging member 20.
The upstream recording head groups 1 and 2 are fixed to a support member 3, and the support member 3 is movably provided on a swing member 20. The support member 3 has one end in contact with the elastic member 13 fixed to the swing member 20 and the other end in contact with the drive shaft of the drive source 4 fixed to the swing member 20. The pivoting member 20 is moved in the longitudinal direction by the reciprocating operation of the shaft. The drive source 4 is formed of, for example, a stepping motor whose drive shaft advances and retreats according to the number of input steps.

Each of the recording heads 1, 2, and 51 has a large number of pixel forming portions arranged in the main scanning direction, and each of the pixel forming portions prints one pixel. The nozzle corresponds. The pixel forming portions of the upstream recording heads 1 and 2 and the pixel forming portion of the downstream recording head 51 partially overlap with each other in the main scanning direction. The printhead 51 is operated to perform printing, and the printhead 51 on the downstream side performs printing by selectively operating a part of a predetermined range of the pixel forming portion.

As in the first embodiment (see FIGS. 2 and 3), the oscillating member 20 faces the platen member 28 at a predetermined interval, and the recording member 30 is positioned between the two members. Passed. The swinging member 20 and the platen member 28 have one end connected to the shaft 25 and the other end fixed to each other via a connecting portion 29, so that the relative posture between the two remains unchanged. I'm dripping.

As shown in FIG. 21, one end of the end of the oscillating member 20 located on the opposite side of the shaft 25 abuts against the elastic member 18 fixed to the apparatus main body, and the opposite side has an end. The drive member 17 is in contact with the drive shaft of the drive source 17 fixed to the main body of the apparatus.
The platen member 28 and the platen member 28 are integrally swung about the shaft 25. The drive source 17 is composed of, for example, a stepping motor whose drive shaft advances and retreats according to the number of input steps.

At the upstream of each of the recording heads 1 and 2, one detecting unit 9 for detecting the registration marks 8 printed on both sides of the recording member 30 is provided. The detection unit 9 is configured by, for example, a line sensor such as a CCD. The image forming apparatus determines the recording member 30 based on the information from the detection unit 9.
, A drive control unit 53 that controls the drive source 4 in accordance with a command from the calculation unit 10, and a calculation unit 10.
Control unit 1 that controls drive source 17 in accordance with an instruction from
9, a control unit 52 for controlling the printing range of the downstream recording head group 51 by shifting data in accordance with a command from the arithmetic unit 10.

[Operation] The color image is formed by printing a plurality of color images on the recording member 30 in order.

At the time of forming the first color image, the first color image is printed on the recording member 30, and the registration marks 8 serving as an index of the printing position when forming the nth color image are printed on both sides of the recording member 30. Is done.

At the time of forming the n-th color image, prior to printing,
The registration mark 8 is detected by the detection member 9, and the skew state at the time of forming the first color image and the skew state at the time of forming the nth color image are checked by the arithmetic unit 10 based on the information.

When the skew of the first color image is detected, the printing range of the downstream recording head group 51 (the range of the operating pixel forming section) is shifted in the main scanning direction, and the printing is performed by the adjacent recording head. A first correction operation for eliminating the overlap and the gap between the partial images to be performed is performed.

When the skew of the n-th color image is detected, the swinging member 20 is swung to make the main scanning direction of the recording head group coincide with the main scanning direction of the first color image. The operation is performed.

Thereafter, an n-th color image is printed on the recording member 30.

While the image of the nth color is being printed, the registration mark 8 is constantly monitored by the detection unit 9. As long as the detection unit 9 does not detect the meandering of the registration mark 8, the recording head groups 1, 2, and 51 are maintained in the positional relationship after the first correction operation and the second correction operation are completed.

The meandering of the registration mark 8 means that the first color image has distortion. Therefore, the registration mark 8
When the meandering is detected, the upstream recording head groups 1 and 2 are moved in the main scanning direction in accordance with the meandering of the registration mark 8 to print the nth color image in accordance with the distorted first color image. And the downstream recording head group 5
1 is shifted in the main scanning direction. At this time, the shift of the print range of the downstream recording head group 51 is performed after the movement of the upstream recording head groups 1 and 2.

The adjustment of the print positions of the recording head groups 1, 2 and 51 will be described below.

The tip of the displacement portion X ₁ of the registration mark 8 and the displacement δ thereof are detected by the detection portion 9. The tip of the displacement portion X ₁ is when it reaches the upstream recording head group 1 and 2, the driving source 4 is driven, the movement of the main scanning direction of the upstream recording head group 1 and 2 is initiated. Also, the ends of the displacement unit X ₁ is when it reaches the upstream recording head group 1 and 2, the driving source 4 is stopped, the movement of the main scanning direction of the upstream recording head group 1 and 2 is completed. Upstream recording head group 1 and 2, the displacement unit X ₁ is while passing through the upstream recording head group 1 and 2, the displacement amount in the main scanning direction [delta], it is moved.

Accordingly, the partial image printed by the upstream recording head groups 1 and 2 is
Before the movement of the upstream recording heads 1 and 2 is rectangular, the movement of the upstream recording heads 1 and 2 is parallelogram. When the movement of the upstream recording heads 1 and 2 is completed, the shape is rectangular. It is.

[0133] On the other hand, the tip of the displacement portion X ₁ is when it reaches the downstream recording head group 51, the main scanning direction of the shift of the print range of the downstream-side recording head group 51 is initiated. Also, the ends of the displacement unit X ₁ is when it reaches the downstream recording head group 51, the main scanning direction of the shift of the print range of the downstream-side recording head group 51 is completed. Print range of the downstream-side printing head group 51, the displacement unit X ₁ is while passing through the downstream recording head group 51, an amount corresponding to the displacement amount δ in the main scanning direction are shifted.

Therefore, the partial image printed by the downstream recording head group 51 is rectangular before the shift of the printing range of the downstream recording head group 51 is started, and The shape is a parallelogram while the printing range is shifted, and the shape is a rectangle after the shifting of the printing range of the downstream recording head group 51 is completed.

The partial image printed by the downstream recording head group 51 is always adjacent to the partial image printed by the upstream recording head groups 1 and 2 without any gap or overlap. Is printed.

Time Δ from when the tip of the displacement portion X ₁ is detected by the detection portion 9 to when it reaches the upstream recording head groups 1 and 2
t ₁ is, L ₁ in the sub-scanning direction spacing between the detector 9 and the upstream recording head group 1 and 2, when the speed of the recording member 30 and V _p, is given by Δt ₁ = L ₁ / V _p . The time Δt ₂ from when the leading end of the displacement portion X1 is detected by the detection portion 9 to when it reaches the downstream recording head group 51 is determined by the sub-scanning of the upstream recording head groups 1 and 2 and the downstream recording head group 51. When the direction of the spacing between L _2, is given by _{Δt 2 = (L 1 + L} 2) / V p. Therefore, the time when the leading end of the displacement portion X ₁ is detected by the detection unit 9 as a reference, the upstream recording head group 1 and 2
Starts moving in the main scanning direction with a delay of time Δt ₁ , and the downstream recording head group 51 starts shifting the printing range in the main scanning direction with a delay of time Δt ₂ .

As described above, since the movement of the downstream recording head group is started after the movement of the upstream recording head group, a gap or overlap occurs between partial images printed by adjacent recording heads. The nth color image is printed without occurrence.

[Effect] Since a mechanism for mechanically moving the downstream recording head group is not required, the number of components can be reduced accordingly. Therefore, the image forming apparatus according to the present embodiment is realized at a lower cost than the apparatus according to the fourth embodiment.

[Sixth Embodiment] A sixth embodiment of a color image forming apparatus using a plurality of recording heads according to the present invention will be described with reference to FIG. In the sixth embodiment, the print positions of the upstream print head group and the downstream print head group in the fourth embodiment are both adjusted by shifting data. In other words, the printing position of the upstream recording head group in the fifth embodiment is adjusted by shifting data.

[Configuration] The configuration of the device is the same as that of the device of the third embodiment.

[Operation] A color image is formed by printing images of a plurality of colors on the recording member 30 in order.

At the time of forming the first color image, the first color image is printed on the recording member 30, and the registration marks 8 serving as indicators of the printing position when forming the nth color image are printed on both sides of the recording member 30. Is done.

At the time of forming the n-th color image, prior to printing,
The registration mark 8 is detected by the detection member 9, and the skew state at the time of forming the first color image and the skew state at the time of forming the nth color image are checked by the arithmetic unit 10 based on the information.

If skew is detected during the formation of the first color image, the printing range of the downstream recording head group 38 is shifted in the main scanning direction, and the interval between partial images printed by adjacent recording heads is shifted. A first correction operation for eliminating the gap and the overlap is performed.

When the skew of the n-th color image is detected, the swinging member 20 is swung to make the main scanning direction of the recording head group coincide with the main scanning direction of the first color image. The operation is performed.

After that, the n-th color image is printed on the recording member 30.

While the n-th color image is being printed, the registration mark 8 is constantly monitored by the detection unit 9. As long as the detection unit 9 does not detect the meandering of the registration mark 8, the recording head groups 31, 32, and 38 are maintained in the positional relationship after the first correction operation and the second correction operation are completed.

The meandering of the registration mark 8 means that the image of the first color has a distortion. Therefore, the registration mark 8
When the meandering of the registration marks 8 is detected, the n-th color image is printed in accordance with the distorted first color image.
Is shifted in the main scanning direction, and the printing range of the downstream recording head group 38 is shifted in the main scanning direction. At this time, the shift of the printing range of the downstream recording head group 38 is performed after the shift of the printing range of the upstream recording head groups 31 and 32.

The adjustment of the print positions of the recording head groups 31, 32 and 38 will be described below.

The tip of the displacement portion X ₁ of the registration mark 8 and the displacement δ thereof are detected by the detection portion 9. When the leading end of the displacement portion X ₁ has reached the upstream recording head group 1 and 2, the main scanning direction of the shift of the print range of the upstream recording head group 31 and 32 is started. Also, the ends of the displacement unit X ₁ is when it reaches the upstream recording head group 1 and 2, the main scanning direction of the shift of the print range of the upstream recording head group 31 and 32 is terminated. The printing range of the upstream recording head groups 31 and 32 is
Displacement unit X ₁ is while passing through the upstream recording head group 31 and 32, an amount corresponding to a δ displacement in the main scanning direction, it is moved.

Therefore, the partial image printed by the upstream recording head groups 31 and 32 is
Before the shift of the print range of 1 and 32 is started, the print area is rectangular, and while the print range of the upstream print head groups 31 and 32 is shifted, the shape is a parallelogram. After the shift of the print range of 32 is completed, the print area is rectangular.

[0152] On the other hand, the tip of the displacement portion X ₁ is when it reaches the downstream recording head group 38, the main scanning direction of the shift of the print range of the downstream-side recording head group 38 is initiated. Also, the ends of the displacement unit X ₁ is when it reaches the downstream recording head group 38, the main scanning direction of the shift of the print range of the downstream-side recording head group 38 is completed. Print range of the downstream-side recording head group 38, the displacement unit X ₁ is while passing through the downstream recording head group 38, an amount corresponding to the displacement amount δ in the main scanning direction are shifted.

Therefore, the partial image printed by the downstream recording head group 38 has a rectangular shape before the shift of the printing range of the downstream recording head group 38 is started. The shape is a parallelogram while the printing range is shifted, and the shape is a rectangle after the shifting of the printing range of the downstream recording head group 38 is completed.

The partial image printed by the downstream recording head group 38 is always the upstream recording head groups 31 and 32.
Is printed adjacent to the partial image printed by the printer without any gap or overlap.

The time Δt ₁ from when the tip of the displacement portion X ₁ is detected by the detection section 9 to when it reaches the upstream recording head groups 31 and 32 is determined by the detection section 9 and the upstream recording head groups 31 and 32.
If the interval in the sub-scanning direction is L ₁ and the speed of the recording member 30 is V _p , then Δt ₁ = L ₁ / V _p . The time Δt2 from when the tip of the displacement portion X1 is detected by the detection unit 9 to when it reaches the downstream recording head group 38 is equal to the upstream recording head groups 31 and 32 and the downstream recording head group 38.
When the distance in the sub-scanning direction and _{L 2, Δt 2 = (L} 1 +
L ₂ ) / V _p . Therefore, the tip end of the displacement portion X ₁ is based on the time detected by the detection unit 9, upstream recording head unit 31 and 32 is started in the main scanning direction of the shift time Delta] t ₁ delayed print range, downstream The recording head group 38 starts shifting the printing range in the main scanning direction with a delay of time Δt ₂ .

As described above, since the movement of the downstream recording head group is started after the movement of the upstream recording head group, gaps and overlaps occur between partial images printed by adjacent recording heads. The nth color image is printed without occurrence.

[Effect] Since a mechanism for mechanically moving the downstream recording head group is not required, the number of components can be reduced accordingly. Therefore, the image forming apparatus according to the present embodiment is realized at a lower cost than the apparatus according to the fifth embodiment.

[Seventh Embodiment] In the embodiments described above, it is assumed that the partial images printed by the adjacent recording heads are adjacent to each other without overlapping portions.

However, the partial images may be printed with their ends overlapping. However, in this case, if the edges of the partial image are simply overlapped and printed, the overlapped portion becomes darker and more conspicuous. Needs to be taken.

The following embodiment relates to the image processing of the overlap portion when the edges of the partial image are printed with overlap. For this reason, in the following embodiments, description will be made focusing on one upstream recording head and one downstream recording head. Therefore, although only two recording heads are illustrated in the drawing to be referred to,
This does not mean that the number of recording heads is two.

FIGS. 22 and 23 show a seventh embodiment of a color image forming apparatus using a plurality of recording heads according to the present invention.
This will be described with reference to FIG. In the seventh embodiment, every other pixel forming section in the overlapping portion of the recording head is operated, and the pixel forming section that operates for each line and the pixel forming section that does not operate are switched.

[Arrangement] As shown in FIG. 22, the upstream print head 207 and the downstream print head 208 are arranged so as to overlap in the main scanning direction. The image memory 201 stores image data to be recorded. The memory selection unit 202 selects image data corresponding to an overlap portion between the upstream recording head 207 and the downstream recording head 208 for each line of image data sent from the image memory 201 and performs signal control. 203 and output to the signal control means 204, and the other image data to the upstream printhead 207 and the downstream printhead 208.

The signal control means 203 outputs every other image data in the overlap portion in the main scanning direction as recording active dots. Here, outputting as recording active dots means outputting image data as it is. Therefore, the image data not selected as the recording active dot is not output. In response to this, in the recording head, in the overlap portion, the pixel forming portion corresponding to the recording active dot operates, and the other pixel forming portions do not operate.

The signal control means 204 outputs, as the recording active dots, the image data not selected as the recording active dots by the signal control means 203 with respect to the image data of the overlap portion. Therefore, the signal control means 20
The image data output as the recording active dots from No. 3 and the image data output as the recording active dots from the signal control means 204 are alternately arranged in the main scanning direction.

The signal control means 205A is composed of the signal control means 2
The image data output from the output unit 03 and the image data output from the signal control unit 204 are alternately supplied to the upstream recording head 207 line by line. The signal control means 205B
The image data output from the signal control unit 203 and the image data output from the signal control unit 204 are alternately supplied to the downstream recording head 208 line by line. One of the signal control means 205A and the signal control means 205B outputs the image data output from the signal control means 203 and the other outputs the image data output from the signal control means 204 for the same line. For example, the signal control means 20
When 5A supplies the image data output from the signal control unit 203 to the upstream recording head 207, the signal control unit 205B supplies the image data output from the signal control unit 204 to the downstream recording head 208.

The signal control means 206 arranges the dots printed by the upstream recording head and the dots printed by the downstream recording head in the overlap portion alternately in the main scanning direction. The signal control means 203, the signal control means 204, and the signal control
05A and the signal control means 205B are comprehensively controlled.

The signal control means 206 has a function of calculating and correcting the value of the width of the overlap portion based on the value of the moving distance of the recording head. Because the width of the part fluctuates,
The value is converted into a dot number and a control signal is output to the memory selection unit 202. Further, it has a function of determining whether to shift the position of the recording active dot in the overlap portion of the downstream recording head based on the value of the moving distance of the recording head. When the dots printed by the downstream recording head are shifted in the main scanning direction, the control is performed so as to appropriately overlap.

[Operation] The image processing of the overlap portion will be described with reference to FIG. In FIG. 23, the width of the overlap portion is set to four recording dots, dots printed by the upstream recording head are indicated by white circles, and dots printed by the downstream recording head are indicated by black circles. Have been.

FIG. 23A shows dots printed by the upstream recording head 207 and dots printed by the downstream recording head 208 for a certain line of image data. In FIG. 23A, for the sake of explanation, dots (white circles) by the upstream recording head 207 and dots (black circles) by the downstream recording head 208 are shown in two rows, but in actuality, FIG. ) Are printed on the same straight line.

As shown in FIG. 23A, in the overlap portion, the dots (white circles) by the upstream recording head 207 and the downstream recording head 208 are arranged along the main scanning direction.
(Black circles) are alternately formed. That is, in the upstream recording head 207, the first and third counting from the right side
The second pixel forming unit operates to print dots, and the second and fourth pixel forming units do not operate and do not print dots. On the other hand, in the downstream recording head 208, the first and third pixel forming sections counted from the left side operate to print dots,
The fourth and fourth pixel forming units do not operate and do not print dots. As a result, one line of image data is printed as shown in FIG. 23C, and dots (white circles) by the upstream recording head 207 and dots (black circles) by the downstream recording head 208 alternate in the overlap portion. Lined up.

The pixel forming section operating in the overlap section is switched for each line. That is, for example, when attention is paid to the overlap portion of the upstream recording head 207, for printing of image data of a certain line, the first and third pixel forming portions operate to print dots, and the second and fourth pixel forming portions operate. The first pixel forming unit does not operate and does not print dots, but for the printing of image data of the next line, the first and third pixel forming units do not operate and do not print dots.
The fourth and fourth pixel forming units operate to print dots. This switching of the operating pixel forming section is repeated for each line printing. The same applies to the downstream recording head 208. As a result, a printing result as shown in FIG. 23B is obtained, and in the overlap portion, the dots (white circles) by the upstream recording head 207 and the dots (black circles) by the downstream recording head 208 are staggered. Has become.

FIG. 23D shows that the position of the dot printed by the downstream recording head 208 is relatively left relative to the position of the dot printed by the upstream recording head 207 due to skew of the recording member. Is shown.
If the same printing is performed in this state as in the normal state by the above-described control, as can be easily understood from FIG.
The dots (white circles) by the upstream recording head 207 and the dots (black circles) by the downstream recording head 208 overlap each other, resulting in a part of the resulting image that is white.
In order to avoid the occurrence of the blank portion, the following control is performed for this situation.

In the situation shown in FIG.
First, as shown in FIG. 23E, the pixel formation portion corresponding to the overlap portion is enlarged. That is, in the upstream recording head 207, the pixel forming portion corresponding to the overlap portion is enlarged to five from the first to the fifth counting from the right, and in the downstream recording head 208, the pixel forming portion corresponding to the overlap portion is formed. The parts are expanded to five from the first to the fifth, counting from the left. Then, the second and fourth pixel forming units of the downstream recording head 208 are operated with respect to the operations of the first, third and fifth pixel forming units of the upstream recording head 207. As a result, one line of image data shown in FIG. 23E is printed. Also, the first, third, and fifth pixel forming units of the downstream recording head 208 are operated with respect to the operation of the second and fourth pixel forming units of the upstream recording head 207.

FIG. 23F is different from FIG. 23D in that the position of the dot printed by the downstream recording head 208 is relative to the position of the dot printed by the upstream recording head 207. Shows a state shifted to the right.
If the same printing is performed in this state as in the normal state by the above-described control, as can be easily understood from FIG.
In addition to the reduction of the overlap portion, dots (white circles) generated by the upstream recording head 207 in the overlap portion
And the dots (black circles) by the downstream recording head 208 overlap with each other, so that an obtained image has a portion that is white. In order to avoid the occurrence of the blank portion, the following control is performed for this situation.

With respect to the situation shown in FIG.
First, as shown in FIG. 23G, the pixel formation portion corresponding to the overlap portion is reduced. That is, in the upstream recording head 207, the pixel formation portion corresponding to the overlap portion is reduced to three from the first to the third counting from the right, and in the downstream recording head 208, the pixel formation portion corresponding to the overlap portion is formed. The part is reduced to three from the first to the third counting from the left. Then, the second pixel forming unit of the downstream recording head 208 is operated with respect to the operation of the first and third pixel forming units of the upstream recording head 207. As a result, one line of image data shown in FIG. 23E is printed. Also, the upstream recording head 20
The first and third pixel forming units of the downstream recording head 208 are operated in response to the operation of the second pixel forming unit of No. 7.

In the control described here, operating the pixel forming unit corresponds to sending image data to the pixel forming unit as it is, and not operating the pixel forming unit corresponds to sending the image data to the pixel forming unit. Is not sent, in other words, the image data sent to the pixel forming unit is replaced with “0”.

The relative displacement between the position of the dot printed by the downstream recording head 208 and the position of the dot printed by the upstream recording head 207 can be detected.
This is performed at the timing of detecting the position of the notch mark at a predetermined length in the sub-scanning direction in the registration mark of the recording paper.
At the time of detecting the mark position, the presence or absence of a dot shift is detected, and if there is a dot shift, how much the dot shifts to the left or right is detected. Depending on that information,
It is determined whether the change of the overlap portion and the inversion of the pixel forming portion where the downstream recording head 208 operates are performed.

The determination is made, for example, according to the following criteria. If the dot shift is within 1/2 dot, the position is unchanged, and if it is not less than 1/2 and within 3/2 dot, the change of the overlap portion and the inversion of the pixel forming portion are performed. More specifically, with respect to the integer n, the displacement X of the dot is expressed as (-1 / 2 + 2n) dot≤X≤ (+ 1/2 +
2n) dot as it is, and (-1 / 2 + 2)
If (n + 1) dots <X <(+ 1/2 + 2n + 1) dots, the change of the overlap portion and the inversion of the pixel forming portion are performed.

[Effect] Since the dot control of the overlap portion is simple dot control, it can be easily realized only by changing a part of the control program.

[Eighth Embodiment] An eighth embodiment of a color image forming apparatus using a plurality of recording heads according to the present invention will be described with reference to FIGS. In the eighth embodiment, the value of the image data sent to the pixel forming portion of the overlapping portion of each recording head is halved, and the dots of the overlapping portion are printed by each recording head in an overlapping manner. is there.

[Arrangement] As shown in FIG. 24, the print head 306 on the upstream side and the print head 307 on the downstream side are arranged so as to overlap in the main scanning direction. The image memory 301 stores image data to be recorded. The memory selection unit 302 selects image data to be printed by the upstream recording head 306 for each line of image data sent from the image memory and outputs the image data to the signal processing unit 303. In step 307, image data to be printed is selected and output to the signal processing unit 304. Image data sent to signal processing means 303 and signal processing means 304
Are commonly included in the overlapped image data. The signal processing unit 303 and the signal processing unit 304 send the image data to the upstream print head 306 and the downstream print head 307 by changing the weighting coefficient of the dots in the overlap portion. For example, the signal processing unit 303
And the signal processing unit 304 converts the value of the image data of the overlap portion into a value of 出力 and outputs it, and outputs the other image data as it is.

If the position of the dot printed by the downstream recording head 307 deviates from the position of the dot printed by the upstream recording head 306, the control unit (not shown) causes the over-range changed by the dot deviation. The value of the width of the wrap portion is converted into the number of dots and transmitted to the memory selection portion 302.

The interpolation data processing means 305 interpolates the image data of the downstream recording head 307 based on the image data of the upstream recording head 306 when a dot shift occurs. Here, the image data interpolated based on the image data of the upstream recording head 306 is stored in the image memory 3.
The original image data from 01 may be used.

[Operation] The image processing of the overlap portion will be described with reference to FIG. In FIG. 25, the width of the overlap portion is set to four recording dots, and the dots printed by the upstream recording head 306 are indicated by circles with oblique lines rising to the left in the overlap portion. Others are indicated by white circles, and the dots printed by the downstream recording head 307 are indicated by circles with oblique lines rising to the right in the overlap portion, and otherwise indicated by black circles.

FIG. 25A shows the dots printed by the upstream recording head 306 and the dots printed by the downstream recording head 307 for a certain line of image data. In FIG. 25A, the upstream recording head 3
The dots by 06 and the dots by the downstream recording head 307 are drawn in two lines for the purpose of explanation, but they are actually printed on the same straight line.

When there is no deviation between the position of the dot printed by the upstream recording head 306 and the position of the dot printed by the downstream recording head 307, FIG.
As shown in (1), the dots in the overlap portion are printed in an overlapping manner. The value of the image data of the dots in the overlap portion printed by the upstream recording head 306 and the value of the image data of the dots in the overlap portion printed by the downstream recording head 307 are both normal dot image data, that is, non-overlapping image data. Since the value is set to の of the value of the image data of the dots in the overlap portion, the density of the dots in the overlap portion printed by the two recording heads is almost equal to the density of the dots in the non-overlap portion.

When the position of the dot printed by the downstream recording head 307 is shifted to the left with respect to the position of the dot printed by the upstream recording head 306, if the deviation is about half of the dot, FIG. As shown in (C), the dots printed by the downstream recording head 307 are located between the dots printed by the upstream recording head 306.

If the deviation of the dots is even larger and is about one dot, the dots printed by the downstream recording head 307 overlap the dots printed by the upstream recording head 306. In this case, since the overlapped portion expands, the image forming portion corresponding to the overlapped portion is enlarged to five. Further, the image data of the downstream recording head 307 is replaced with interpolation data. For example, the image data F2 of the second pixel formation unit from the left of the downstream recording head 307 is F2 = (f, where f (n) is the image data of the nth pixel formation unit from the right of the upstream recording head 306.
(4) × Z + f (3) × (1-Z)) / 2. Here, Z has a relationship of Z = X / (resolution) with the deviation amount X.

In the example described here, the overlap portion is widened. However, when the overlap portion is narrowed, the pixel forming portion corresponding to the overlap portion is reduced by three, and the same interpolation processing is performed. It is.

Here, the weighting of the image data in the overlap portion is performed by halving the entire range, but a weighting characteristic that monotonically decreases toward the head end may be used. Not limited.

Although the interpolation process for the deviation is performed only on the overlapped portion, the interpolation process may be performed on the entire range of the head or may be performed on the boundary with the overlapped portion, the degree of which gradually decreases. Good.

The relative displacement of the position of the dot printed by the downstream recording head 307 with respect to the position of the dot printed by the upstream recording head 306 is detected.
This is performed at the timing of detecting the position of the notch mark at a predetermined length in the sub-scanning direction in the registration mark of the recording paper.
At the time of detecting the mark position, the presence or absence of a dot shift is detected, and if there is a dot shift, how much the dot shifts to the left or right is detected. Depending on that information,
The change of the overlap portion and the calculation of the interpolation data are performed.

[Effect] Since the image data is generated by the interpolation data for the delicate displacement of the overlapped dots as the dot control of the overlap portion, the difference between the overlap portion and the other image recording portions is small, and the difference between the overlap portion and the other image recording portions is small. The effect of making the border less noticeable is great.

[Ninth Embodiment] A ninth embodiment of a color image forming apparatus using a plurality of recording heads according to the present invention will be described with reference to FIGS. 26, 27 and 28. In the ninth embodiment, when the dots are shifted, the diameter of the recording dots in the overlap portion is enlarged.

[Structure] Although not shown, the upstream print head and the downstream print head are arranged so as to overlap in the main scanning direction.

FIG. 26 is an explanatory diagram of head control. Negative corona is generated by a corona generating section 401 inside the head, and emission control of ion charges is performed by a dot control electrode 403 disposed below the corona generating section, whereby a latent image is formed on the recording paper 30. The counter electrode 402 is located below the recording paper 30. The dot control electrode 403 has an insulating substrate and electrodes provided on both sides thereof, and the potential of the dot control electrode 403 is controlled by the head signal control unit 404. Further, a high-voltage control unit 405 for applying a high bias potential to the dot control electrode 403 is provided. The variable control of the potential V1 by the high voltage control unit 405 is performed according to the head position control value of the arithmetic unit 10. Although not shown in FIG. 26, a high-voltage power supply having a normal potential V2 for 405 is connected to the dot control electrode outside the overlap portion of the head.

Further, an overall control unit 406 for controlling the entire system is provided. The overall control unit 406 performs head signal control and the above-described various controls at once, and does not perform only the control described in this description.

[Operation] The image processing of the overlap portion will be described with reference to FIG. In FIG. 27, the width of the overlap portion is set to four recording dots, dots printed by the upstream recording head are indicated by white circles, and dots printed by the downstream recording head are indicated by black circles. Have been. This embodiment is similar to the seventh embodiment, and in an ideal state, in the overlap portion, the dots printed by the upstream recording head and the dots printed by the downstream recording head are in the main scanning direction. The pixel forming portion in which the overlap portion of the recording head operates so as to be in contact with the recording head is selected.

FIG. 27A shows a state where the position of the dot printed by the downstream recording head is shifted to the left from the position of the dot printed by the upstream recording head. In this state, in the overlap portion, a gap is generated between the dot formed by the upstream print head and the dot formed by the downstream print head. To avoid this white spot,
In the overlap portion, dots having a diameter larger than the standard are printed.

FIG. 27B shows a case where both the diameter of the dot by the upstream recording head and the diameter of the dot by the downstream recording head in the overlap portion are enlarged.
FIG. 7C shows a case where only the diameter of the dot by the recording head downstream of the overlap portion is enlarged.

The enlargement of the diameter of the dot is achieved by the dot control electrode 403.
This is performed by changing the potential of. That is, the high-voltage controller 405 changes the potential of the dot control electrode 403 in the overlap portion to V1. Here, the potential of the dot control electrode 403 other than the overlap portion is V2, which satisfies the relationship | V1 | <| V2 |. Potential V
The dot formed by one dot control electrode 403 is:
The diameter is larger than the dot formed by the dot control electrode 403 at the potential V2.

FIG. 2 schematically shows the difference in the trajectory of the ion charge with respect to the level of the potential of the dot control electrode.
8 can be easily understood. FIG.
FIG. 28A shows a case where the potential of the dot control electrode 403 is high, and FIG. 28B shows a case where the potential of the dot control electrode 403 is low. As shown in FIG. 28 (A), when the potential of the dot control electrode 403 is high, the equipotential surface of the electric field formed between the dot control electrode 403 and the recording paper 30 is close to a flat surface, so that the dot Control electrode 403
The ionic charges passing through the holes of the recording paper 3 progress linearly and
Reaches 0. On the other hand, as shown in FIG. 28B, when the potential of the dot control electrode 403 is low, the equipotential surface of the electric field formed between the dot control electrode 403 and the recording paper 30 is curved. Because it is large, the dot control electrode 403
The ionic charges that have passed through the holes (1) and (2) advance while spreading, and reach the recording paper 30. Therefore, when the potential of the dot control electrode 403 is low, a larger dot is formed on the recording paper 30 than when the potential of the dot control electrode 403 is high.

The change of the potential of the dot control electrode is shown in FIG.
As shown in FIG. 27B, the operation is performed only for both the upstream print head and the downstream print head, or FIG.
As shown in (C), the occurrence of a blank portion of an image can be prevented only by performing the process on one of the two.

The detection of the deviation of the position of the dot printed by the downstream recording head from the position of the dot printed by the upstream recording head is performed by checking the registration marks on the recording paper at intervals of a certain length in the sub-scanning direction. This is performed at the timing of detecting the position. At the time of detecting the mark position, the presence or absence of a dot shift is detected, and if there is a dot shift, how much the dot shifts to the left or right is detected. In accordance with the information, the change of the diameter of the dot in the overlap portion, that is, the change of the potential of the dot control electrode 403 is performed. As described above, the potential of the dot control electrode 403 is controlled by the high voltage control unit 405, and is controlled so that the potential V1 becomes the predetermined minimum potential Vmin when the dot shift amount X is an integral multiple of the resolution.

Here, an example is shown in which dots in the overlap portion are alternately printed by the upstream print head and the downstream print head. However, similar to the eighth embodiment, image data of dots in the overlap portion is printed. May be applied to driving for weighting the value of. In addition, this processing may be performed on the overlapping portion of a plurality of heads regardless of the dot shift.

[Effect] Since the dot diameter enlargement process is performed as the dot control of the overlapped portion, even if it is slightly shifted, the portion looks blurred, so that the symptom of the image noise due to the shift is hardly noticeable. In addition, there is little change in image quality due to the ease of adjustment at the time of initial setting and long-term use.

[Tenth Embodiment] In the eighth embodiment, the latent image is formed twice by simply halving the image data value of the dot in the overlap portion. The result is slightly different from the case where the latent image is formed once and developed with the image data value kept. FIG. 29 shows an optical density value (OD value) of a dot obtained by forming a latent image twice and developing the latent image with the image data value being halved with respect to the image data, and the image data value. A latent image is formed once while the image is developed and developed by developing the latent image. D. It is a graph of a value, and this graph has shown the above-mentioned state. For example, at an image data value of 20%, the image density obtained by forming a latent image twice is higher than the image density. D. Value is 0.03 lighter, and at an image data value of 60%, the image density obtained by forming the latent image twice is higher than the O.D. value.
D. The value is about 0.01 lighter. However, the image data value 100
%, The image density obtained by forming the latent image twice is higher than the image density. D.
The value is around 0.02 deeper, and the situation is reversed.

Although the electrostatic recording method is considered here, the latent image is formed by the upstream recording head and then the latent image is formed by the downstream recording head in the recording process of the overlap portion. Is divided into two parts and combined on the latent image, the low-density part is affected by the small repulsive force of the dot charges on the latent image, and the latent image potential is slightly lower even if the latent image is formed afterwards. It is thought that it has become. However, the effect is small in the high-density portion, and as a result, the latent image potential is considered to be slightly higher.

Therefore, the overlap portion in the image has a slightly lighter band when the density is low to medium, and a slightly darker band when the density is high. So they all look very good.

FIGS. 29 to 31 show a tenth embodiment of a color image forming apparatus using a plurality of recording heads according to the present invention.
This will be described with reference to FIG. The tenth embodiment divides an image data value sent to a pixel forming portion of an overlap portion of each recording head, and forms a latent image of a dot twice by each recording head in accordance with the divided image data value. At this time, the image data value is corrected so that the density of dots formed by two latent images is equal to the density of dots formed by one latent image. In the following description, this correction will be referred to as γ correction.

[Structure] The tenth embodiment is a structure obtained by partially changing the structure of FIG. 24, and the changed part is shown in FIG. Therefore, the following description will be made with reference to FIG.

As shown in FIG. 24, the print head 306 on the upstream side and the print head 307 on the downstream side are arranged so as to overlap in the main scanning direction. Image memory 301
Stores image data to be recorded. Memory selector 3
02, the image data to be printed by the upstream recording head 306 is selected and output to the signal processing means 303 for each line of image data sent from the image memory, and the image data is printed by the downstream recording head 307. The selected image data is output to the signal processing unit 304. Signal processing means 303
And the image data sent to the signal processing means 304 commonly include the image data of the overlap portion.

As shown in FIG. 30, an overlap γ correction processing unit 308 is added. The overlap γ correction processing unit 308 reads the data value in the memory selection unit 302, and inputs the γ conversion LU input in advance.
T conversion processing is performed by T, and the conversion processing result is returned to the memory selection unit 302. Here, the LUT for γ conversion considers a general lookup table conversion from 8-bit input to 8-bit output. Further, it is assumed that the characteristics shown in FIG. 29 are measured in advance, and the characteristics shown in FIG. 31 are obtained from the data to generate LUT conversion data.

Here, a synthesizing method different from the synthesizing method in which the sum of the divided image data values of the overlap portions of the respective recording heads is equal to the original image data value described in the eighth embodiment will be described.

A method of dividing the image data value of the dot by the upstream recording head and the image data value of the dot by the downstream recording head so that the sum is equal to the original recording data value. A method is used in combination with a method in which the weighting coefficient becomes smaller for one side. That is, for example, assuming that the number of dots in the overlap portion is 4, the weighting coefficients for the pixel formation portion in the overlap portion of the upstream recording head are 4/5, 3/5, 2/5, 1 from the left.
/ 5, and the weighting coefficient for the pixel forming portion of the overlap portion of the downstream recording head is 1/5, 2
/ 5, 3/5 and 4/5. Here, the number of dots in the overlap portion is set to 4 for simplicity, but in an actual apparatus, the number of dots in the overlap portion is set to 24 or more.

The signal control section 303 multiplies the image data of the overlap section by such a weighting coefficient and outputs the result to the upstream recording head 306.
Reference numeral 4 denotes an upstream print head 307 which multiplies the image data of the overlap portion by such a weighting coefficient.
Output to Since the interpolation data processing means 305 has been described in the eighth embodiment, the description thereof is omitted here.

[Operation] FIG. 29 shows the characteristics of the recording data value and the optical density (OD) of the one-time development of the two latent images.
O.D. of one latent image and one development D. FIG. 3 shows the relationship between the recording data correction values of the two-time latent image and one-time development in which the characteristic values are obtained.
It is one. Looking at the data, for example, the recorded data value 20
%, The output becomes 23% when the print data value is 60%, and the output becomes 61% when the print data value is 60%.
When the output is 97%, the output is set to 97% so that the O.D. D. Value and O.D. D. The values can be equal. It can be seen that if this gamma correction process is performed, the shading of the overlap portion will not be noticeable.
The γ correction for the recording data value of the overlap portion is performed by the overlap γ correction processing unit 308, and the processed data is transferred to the memory selection unit 302 again to perform the overlap processing.

As described above, the range of the overlap portion is assumed to be 4 dots. The image data values of the recording dots in the overlap portion are, for example, 20%, 60
%, 20%, and 100%, first, the image data values are 23%, 61%, 23%, and 97% by gamma correction.
Is corrected to Further, by the signal processing means 303, 23% × 4/5 = 28% for the upstream print head 306, 61
% × 3/5 = 37%, 97% × １ ／ = 19%, and the signal processing means 304 calculates the downstream recording head 307.
23% × 1/5 = 5%, 61% × 2/5 = 24%,
It is calculated as 23% × 3/5 = 14% and 97% × 4/5 = 78%. Thereafter, the data is transferred to the upstream recording head 30.
6 and the downstream recording head 307, respectively, and are subjected to latent image processing. As a result, the image data values of the recording dots in the overlap portion are combined to obtain 18% + 5% = 23%, 37%
% + 24% = 61%, 9% + 14% = 23%, 19% +
78% = 97%, and the O.D. D. The value is 20% by one development of one latent image,
O.D. of 60%, 20% and 100% dots. D. Will be the same as the value.

Here, an example has been shown in which the image data of the overlap portion is monotonically decreased in weight toward the head end portion. However, the present invention is applied to a method of halving all the image data of the overlap portion. The weighting characteristic curve is not limited to the above example.

[Eleventh Embodiment] An eleventh embodiment of a color image forming apparatus using a plurality of recording heads according to the present invention will be described with reference to FIG. In the eleventh embodiment, the gamma correction described in the tenth embodiment is performed on image data of recording dots in an overlap portion for each recording color.

[Configuration] This configuration is a configuration obtained by partially modifying the configuration of FIG. 24. As shown in FIG. 32, an overlap γ correction processing unit 30 that performs γ correction for each recording color
9 has been added. There are four recording colors, KYMC,
The overlap γ correction processing unit 309 has a γ correction processing unit dedicated to each color. The other configuration is the same as that of the above-described embodiment, and the description is omitted here.

[Operation] Assuming that recording is performed in the order of, for example, KYMC colors, first, corresponding to the recording of K colors,
The overlapping K-γ correction processing unit in the γ correction processing unit 309 is selected, and a series of processing is performed. The series of processing is performed in the same manner as in the above-described embodiment. next,
The overlap Y-γ in the γ correction processing unit 309 corresponds to each of the Y color recording, the M color recording, and the C color recording.
The correction processing unit, the M-γ correction processing unit for overlap, and the C-γ correction processing unit for overlap are sequentially selected, and a series of processing is performed. Here is an example of a four-color record,
The number of colors is not limited to four colors.

[Twelfth Embodiment] A twelfth embodiment of a color image forming apparatus using a plurality of recording heads according to the present invention will be described with reference to FIGS. In the twelfth embodiment, image data values of recording dots in an overlapping portion are subjected to overlap γ correction processing for each dot of an upstream recording head and a downstream recording head and are synthesized on recording paper. is there.

[Structure] Only parts different from those in FIG. 24 will be described. In FIG. 33, a memory selection unit 302
Selects the image data corresponding to the overlap,
The selected image data is converted to the upstream dot overlap γ
It is sent to the correction unit 501 and the downstream dot overlap γ correction unit 502. Gamma correction units 501 and 50 for overlap
Each of 2 performs γ correction of image data for each dot.
Here, the multiplication processing of the weighting coefficients is not performed. Subsequent processing is a normal recording operation.

[Operation] The image data corresponding to the overlap portion is subjected to γ correction for each dot. The γ correction is converted based on, for example, the table characteristics shown in FIG. This data is measured in advance as shown in FIG. 29. For example, the weighting coefficient characteristic of monotonically decreasing toward the head end and FIG.
And the combined data. Again, for simplicity, the overlap width is assumed to be four dots. In FIG. 34, the solid line is the correction data, but the broken line is the characteristic excluding FIG. This data is input in advance as LUT data to each of the overlap gamma correction units 501 and 502. Further, since the dots by the upstream recording head and the dots by the downstream recording head overlap in the main scanning direction with a monotonically decreasing characteristic that is left-right reversed, the state of the dot positional relationship is indicated by numbers in FIG. . In accordance with this characteristic, the image data of the overlap portion is γ-corrected for each dot, and the data is stored in the recording heads 306 and 307.
And the normal print operation is performed by the upstream print head 306 and the downstream print head 307. On the recording paper, dots by the upstream recording head and dots by the downstream recording head are recorded in an overlapping manner.

The present invention is not limited to the above embodiment. All implementations performed without departing from the spirit of the invention are included in the present invention.

The present specification includes the inventions described in the following sections.

[0228] 1. [Configuration] In a color image recording apparatus that divides a plurality of recording heads into two or more groups in the sub-scanning direction, performs recording in the main scanning direction, and superimposes each color image, mutual recording positions of the upstream recording head group. Means for shifting the recording position of the entire upstream recording head in the main scanning direction while maintaining the recording position of the entire downstream recording head group. Means for shifting the head group in the main scanning direction, registration marks provided on the recording medium, detection means for detecting the registration marks, and arithmetic means for calculating the transport state of the recording medium from the positions of the registration marks. The shift amount in the main scanning direction of the print position of the entire upstream print head group relative to the transport state of the print medium and the upstream print head group of the print position of the entire downstream print head group Calculating means for calculating the shift amount in the main scanning direction, printing a registration mark at the time of recording the first color, and based on the conveyance state of the recording paper calculated from the registration marks detected at the time of recording the second color and thereafter, The recording position of the entire upstream recording head group is shifted in the main scanning direction so that the recording of the second color and the subsequent colors overlap the printing position of the first color, and the end of the downstream recording head group is substantially aligned with the end of the upstream recording head group. A color image forming apparatus using a plurality of recording heads, wherein the recording position of the entire downstream recording head group is shifted in the main scanning direction so as to match.

[Corresponding Embodiment] The first, second, and third embodiments correspond to this embodiment.

[Effect] The downstream recording head group is adjusted so that the end of the downstream recording head group substantially coincides with the end of the upstream recording head group by the arithmetic means for calculating the transport state and the arithmetic means for calculating the shift amount. Since the entire recording position is shifted in the main scanning direction, the gap or overlap at the boundary between adjacent recording heads caused by the skew of the recording paper of the first color can be made inconspicuous by the correction operation for the second and subsequent colors. .

[0231] 2. [Arrangement] In a color image forming apparatus in which a plurality of recording heads are arranged in the main scanning direction while being divided into several groups in the sub-scanning direction, and each color image is superimposed on a recording medium, the recording heads (1, 2, ), And a support member (30) that movably supports the main scanning direction so that the position can be changed in the main scanning direction while maintaining the mutual positional relationship, and the recording heads (1, 2) of the upstream group are moved in the main scanning direction. The drive source (4) and the printheads (1, 2) of the upstream group are moved so that the printhead (5) can change its position in the main scanning direction while maintaining the mutual positional relationship of the downstream group. A support member (6) that freely supports and is movable in the main scanning direction in conjunction with the support member (3), and a drive source (7) that moves the group of recording heads (5) on the downstream side in the main scanning direction. ), The print heads (1, 2) in the upstream group and the print group in the downstream group A swing member (20) which can be rotated in the main scanning direction with the recording head (5) mounted thereon, and a drive source (17) which swings the swing member.
And a detection unit (9) for reading a registration mark (8) indicating a printing position, and a calculation unit (10) for calculating a recording position.
And an electrical drive control unit (11) for electrically driving the drive sources (4, 7, 17) based on the calculation result. When recording the first color, the image of the first color and the second and subsequent colors are recorded. At the same time, the registration mark (8) serving as an index of the printing position is printed, and at the time of recording of the second and subsequent colors, the registration mark (8) is detected by the detection member (9) prior to recording, and the skew state of the first color and the registration mark The skew state of the first color is calculated, and when the skew of the first color is detected, the support member (6) is moved in the main scanning direction, and the skew generated in the first color causes a gap or overlap between adjacent recording heads. Is performed, and when the skew of the second color is detected, the oscillating member (20) is oscillated to match the main scanning direction recorded in the first color. After performing the correction operation and starting the recording operation by the recording heads of the upstream group, Are based on the detection result of the registration mark (8), while maintaining the positional relationship between the first correction operation and the second correction operation, the recording heads (1, 2) of the upstream group and the recording group of the downstream group. A color image forming apparatus using a plurality of recording heads for recording a second color while moving a support (3) on which the recording head (5) is mounted in the main scanning direction.

[Corresponding Embodiment] The first embodiment corresponds to the first embodiment.

[Effect] A support member 3 for movably supporting the printheads of the upstream group so as to be able to change their positions in the main scanning direction, and a support for changing the positions of the printheads of the downstream group in the main scanning direction. The member 6 makes it possible to make the gap or overlap at the boundary between adjacent recording heads caused by skew of the recording paper of the first color inconspicuous by the correction operation for the second and subsequent colors. Further, since the movement amount can be mechanically adjusted, the image boundary portion between the adjacent recording heads can be accurately positioned.

[0234] 3. [Arrangement] In a color image forming apparatus in which a plurality of recording heads are arranged in the main scanning direction while being divided into several groups in the sub-scanning direction, and each color image is superimposed on a recording medium, the recording heads (1, 2, And a driving source (4) for moving the recording heads (1, 2) of the upstream group in the main scanning direction so as to be movable in the main scanning direction. The printing positions of the upstream group of printheads (1, 2) are arranged so as to overlap in the main scanning direction in the main scanning direction, and are maintained in the main scanning direction together with the printing heads of the upstream group while maintaining the positional relationship therebetween. The print head (21) of the downstream group that can move, the print head (1, 2) of the upstream group, and the print head (2) of the downstream group.
1) a swinging member (20) that can be mounted and rotated in the main scanning direction, and a driving source (17) that swings the swinging member.
And a detection unit (9) for reading a registration mark (8) indicating a printing position, and a calculation unit (10) for calculating a recording position.
And an electric drive control unit 11 for electrically driving the drive sources (4, 17) based on the calculation results, and a printhead control unit for shifting the signal of the print position of the printheads (21) in the downstream group. (22), the image of the first color and the registration mark (8) serving as an index of the printing position of the second and subsequent colors are printed simultaneously at the time of recording the first color, and at the time of the recording of the second color, The registration mark (8) is detected by the detection member (9), the skew state of the first color and the skew state of the second color are calculated, and when the skew of the first color is detected, recording of the group on the downstream side is performed. The first correction operation for shifting the signal of the print position of the head (21) to eliminate the gap or overlap between adjacent recording heads due to the skew generated in the first color, and the shaking when the second color skew is detected. The moving member (20) is swung to record the first color. After performing the second correction operation to match the main scanning direction and starting the recording operation by the recording heads of the upstream group, the registration mark is maintained while maintaining the positional relationship between the first correction operation and the second correction operation. On the basis of the detection result of (8), the support table (3) on which the print heads (1, 2) of the upstream group and the print head (21) of the downstream group are mounted.
A color image forming apparatus using a plurality of recording heads for recording the second and subsequent colors while moving in the main scanning direction.

[Corresponding Embodiment] The second embodiment corresponds to the second embodiment.

[Effect] The printhead control unit 22 shifts the signal of the print position with the printhead of the downstream group, which is arranged so that the print position overlaps with the printhead of the upstream group in the main scanning direction. In addition, the gap or overlap at the boundary between adjacent recording heads caused by the skew of the recording paper of the first color can be made inconspicuous by the correction operation for the second and subsequent colors. Further, since there is no need to have a mechanism for moving the recording heads in the downstream group, a high-performance device can be provided at low cost.

[0237] 4. [Arrangement] In a color image forming apparatus in which a plurality of recording heads are arranged in the main scanning direction while being divided into some groups in the sub-scanning direction, and each color image is superimposed on a recording medium, the recording heads (31, 32) in the upstream group are arranged. ) And a group of recording heads (38) on the downstream side are arranged so as to overlap in the main scanning direction, and a swing member (34) that can rotate in the main scanning direction, and a driving source (34) that swings the swing member 1
7), a detection unit (9) for reading a registration mark (8) indicating the printing position, and a calculation unit (1) for calculating the recording position
0) and a print head controller (22, 23) that shifts a print signal based on the calculation result. When printing the first color, the registration as an index of the print position of the first color image and the second and subsequent colors At the time of printing the second and subsequent colors, the registration mark (8) is detected by the detecting member (9) prior to printing, and the skew state of the first color and the skew state of the second color are calculated. When the skew of the color is detected, the first correction is performed to shift the signal of the printing position of the recording heads 38 in the downstream group to eliminate the gap or overlap between the adjacent recording heads due to the skew generated in the first color. When the skew of the second color is detected, a second correction operation of swinging the swing member (34) to match the main scanning direction recorded in the first color is performed. After starting the recording operation with the recording head of While maintaining the positional relationship between the first correction operation and the second correction operation, recording of the recording heads (31, 32) of the upstream group and recording of the downstream group is performed based on the detection result of the registration mark (8). A color image forming apparatus using a plurality of recording heads for recording the second and subsequent colors while electrically shifting the recording position of the head (38) in the main scanning direction.

[Corresponding Embodiment] The third embodiment corresponds to the third embodiment.

[Effect] The recording heads of the first group are arranged so that the recording heads of the upstream group and the recording group of the downstream group overlap each other in the main scanning direction, and the recording head control unit shifts the recording signal. The gap or overlap at the boundary between adjacent recording heads caused by skew of the recording paper can be made inconspicuous by the correction operation for the second and subsequent colors. Further, since there is no need to have a mechanism for moving the recording heads in the upstream and downstream groups, a high-performance apparatus can be provided at low cost.

[0240] 5. [Configuration] In a color image recording apparatus that divides a plurality of recording heads into two or more groups in the sub-scanning direction, performs recording in the main scanning direction, and superimposes each color image, mutual recording positions of the upstream recording head group. Means for shifting the recording position of the entire upstream recording head group in the main scanning direction while maintaining the recording position of the entire downstream recording head group on the upstream side while maintaining the mutual recording position of the downstream recording head group. Means for shifting in the main scanning direction with respect to the recording head group, registration marks provided on the recording medium, detection means for detecting the registration marks, and calculation means for calculating the transport state of the recording medium from the position of the registration marks The shift amount in the main scanning direction of the print position of the entire upstream print head group and the upstream print head group of the print position of the entire downstream print head group relative to the conveyance state of the print medium. Computing means for calculating the amount of shift in the main scanning direction, printing a registration mark at the time of recording of the first color, based on the conveyance state of the recording paper calculated from the registration mark detected at the time of recording the second color, The recording position of the entire upstream recording head group is shifted in the main scanning direction so that the recording of the second color or later overlaps the printing position of the first color, and the recording medium moves from the upstream head group to the downstream head group with a time delay. A color image forming apparatus using a plurality of recording heads, wherein the recording position of the entire downstream recording head group is shifted in the main scanning direction.

[Corresponding Embodiment] The fourth, fifth, and sixth embodiments correspond to this embodiment.

[Effect] The recording medium is shifted by the means for shifting the recording position of the entire upstream recording head group in the main scanning direction and the means for shifting the recording position of the entire downstream recording head group in the main scanning direction. It is possible to prevent gaps and overlaps at boundaries between adjacent recording heads, which are caused by a time delay of moving from the group to the downstream head group.

6. [Arrangement] In a color image forming apparatus in which a plurality of recording heads are arranged in the main scanning direction while being divided into several groups in the sub-scanning direction, and each color image is superimposed on a recording medium, the recording heads (1, 2, ), And a support member (3) for movably supporting the position of the recording heads in the main scanning direction while maintaining the positional relationship therebetween, and the recording heads (1, 2) of the upstream group are moved in the main scanning direction. A drive source (4), a support member (48) for movably supporting the recording head (41) so as to be able to change its position in the main scanning direction while maintaining the positional relationship between the downstream group and a downstream member, A driving source (46) for moving the group of recording heads (41) in the main scanning direction, an upstream group of recording heads (1, 2) and a downstream group of recording heads (41) are mounted. A swing member (44) rotatable in the main scanning direction; Moving member (4
4) a drive source (17) for swinging, a detection unit (9) for reading a registration mark (8) for informing a printing position, a calculation unit (10) for calculating a recording position, and a drive source based on the calculation result. (4, 46, 17) for electrically driving (43, 42, 19), and when recording the first color, the image of the first color and the index of the printing position of the second and subsequent colors are provided. Is printed at the same time, and at the time of recording the second and subsequent colors, the registration mark (8) is detected by the detecting member (9) prior to recording, and the skew state of the first color and the skew state of the second color are detected. When the skew of the first color is detected, the support member (7) is moved in the main scanning direction to eliminate the gap or overlap between adjacent recording heads due to the skew generated in the first color. Is performed and the second color skew is detected Performs a second correction operation for rocking the rocking member (20) so as to match the main scanning direction recorded in the first color, and starts the recording operation by the recording heads of the upstream group. While maintaining the positional relationship between the first correction operation and the second correction operation, a support table on which the recording heads (1, 2) of the upstream group are mounted based on the detection result of the registration mark (8). (3) and the recording heads (4
The support table (7) on which 1) is mounted is moved in the main scanning direction with a time difference in which the recording medium passes in accordance with the distance between the upstream side and the downstream side in the sub-scanning direction, and the second and subsequent colors are moved. A color image forming apparatus using a plurality of recording heads for recording images.

[Corresponding Embodiment] The fourth embodiment corresponds to the fourth embodiment.

[Effects] A supporting member for movably supporting the printhead of the upstream group so as to be able to change its position in the main scanning direction, and the printhead of the downstream group so as to be changeable in the main scanning direction. The support member that is movably supported can prevent gaps and overlaps at the boundary between adjacent print heads, which are caused by a time delay when the print medium moves from the upstream head group to the downstream head group.

Further, since the movement amount can be adjusted mechanically, the image boundary portion between adjacent recording heads can be accurately positioned.

[0247] 7. [Arrangement] In a color image forming apparatus in which a plurality of recording heads are arranged in the main scanning direction while being divided into several groups in the sub-scanning direction, and each color image is superimposed on a recording medium, the recording heads (1, 2, ), And a support member (3) for movably supporting the position of the recording heads in the main scanning direction while maintaining the positional relationship therebetween, and the recording heads (1, 2) of the upstream group are moved in the main scanning direction. The drive source (4), and the printheads (51) of the downstream group are mounted so as to overlap the printheads (1, 2) of the upstream group and the printheads (1, 2) of the upstream group. A swinging member (54) that can be placed and rotated in the main scanning direction, a drive source (17) that swings the swinging member (54), and a detection unit that reads a registration mark (8) indicating a printing position. (9)
An operation unit (10) for calculating the recording position; an electric drive control unit (53, 19) for electrically driving the drive source (4, 17) based on the operation result; A control unit (52) for changing the printing position of the head (51) by shifting the signal; and a registration mark (8) serving as an index of the printing position of the first color image and the printing positions of the second and subsequent colors when recording the first color. And at the same time, when recording the second and subsequent colors,
Prior to recording, the registration mark (8) is detected by the detection member (9), and the skew state of the first color and the skew state of the second color are calculated. A first correction operation is performed to electrically shift the printing position of the group of recording heads (51) to eliminate the gap or overlap between adjacent recording heads due to the skew generated in the first color, and detect the skew of the second color. In this case, the swinging member (54) is swung to perform a second correction operation for matching the main scanning direction recorded in the first color, and after the recording operation by the upstream group of recording heads is started. Is to place the recording heads (1, 2) of the upstream group based on the detection result of the registration mark (8) while maintaining the positional relationship between the first correction operation and the second correction operation. (3) and the recording head (51) of the downstream group
The printing position of the second color and the subsequent colors is recorded by moving the printing position in the main scanning direction by a signal by providing a time difference in which the recording medium passes in accordance with the interval between the upstream side and the downstream side in the sub-scanning direction. A color image forming apparatus using a recording head.

[Corresponding Embodiment] The fifth embodiment corresponds to the fifth embodiment.

[Effect] The recording heads 51 of the downstream group are placed so as to overlap the recording heads of the upstream group, and the printing positions of the recording heads of the downstream group are made variable by shifting the signal. With the control unit 52, it is possible to prevent a gap or an overlap at a boundary between adjacent recording heads, which is caused by a time delay when the recording medium moves from the upstream head group to the downstream head group. Further, since there is no need to have a mechanism for moving the recording heads in the downstream group, a high-performance device can be provided at low cost.

[0250] 8. [Arrangement] In a color image forming apparatus in which a plurality of recording heads are arranged in the main scanning direction while being divided into several groups in the sub-scanning direction, and a recording medium is reciprocated to superimpose each color image, the recording heads of the upstream group ( 31,3
2) a swinging member (34) that is mounted so that the recording heads (38) on the downstream side overlap with each other in the main scanning direction and can rotate with respect to the main scanning direction, and a drive that swings the swinging member. A source (17), a detection unit (9) for reading a registration mark (8) indicating a printing position, a calculation unit (10) for calculating a recording position, and a recording head for shifting data of the recording position based on the calculation result. And a control unit (22, 23) for simultaneously printing the first color image and a registration mark as an index of the printing position of the second and subsequent colors at the time of recording of the first color. First, the registration mark (8) is detected by the detection member (9), the skew state of the first color and the skew state of the second color are calculated, and when the skew of the first color is detected, the group of the downstream group is detected. The print position signal of the recording head (38) is shifted. The first correction operation for eliminating the clearance or overlap between adjacent recording heads due to the skew generated in the first color, and the oscillating member (34) is oscillated when the skew of the second color is detected. After the second correction operation to match the main scanning direction recorded in the first color and the recording operation by the recording heads (31, 32) of the upstream group are started,
While maintaining the positional relationship between the first correction operation and the second correction operation, recording of the recording heads (31, 32) of the upstream group and recording of the downstream group is performed based on the detection result of the registration mark (8). The recording position of the head (38) is electrically shifted in the main scanning direction, and the recording heads (1, 2) of the upstream group and the recording head (38) of the downstream group are moved to the upstream side. A color difference using a plurality of recording heads that shifts the printing position by data in the main scanning direction and moves to print the second and subsequent colors by providing a time difference in which the recording medium passes according to the interval where the downstream side is separated in the sub-scanning direction Image forming device.

[Corresponding Embodiment] The sixth embodiment corresponds to the sixth embodiment.

[Effects] The printheads of the upstream group and the printheads of the downstream group are mounted so as to overlap in the main scanning direction, and the printhead control unit that shifts the data at the print position causes the print medium to be shifted. Can be prevented from occurring at the boundary between adjacent recording heads, which is caused by a time delay when the print head moves from the upstream head group to the downstream head group. Further, since there is no need to have a mechanism for moving the recording heads of the upstream and downstream groups, a high-performance apparatus can be provided at low cost.

[0253] 9. [Structure] The oscillating member (20, 34, 44, 54) of the color image forming apparatus using the plurality of recording heads according to the first to eighth aspects is arranged so that the interval between the recording head and the recording paper in the main scanning direction. A color image forming apparatus using a plurality of printheads having a platen member (38) that rotates by the same angle in conjunction with swinging of a printhead group in order to make the printhead group constant.

[Corresponding Embodiment] The first to sixth embodiments correspond to this embodiment.

[Effect] By rotating the swinging member and the platen member by the same angle, the gap between the recording head and the recording paper can be made constant in the main scanning direction, and the density at the boundary between adjacent recording heads can be improved. The occurrence of unevenness can be prevented.

[0256] 10. [Configuration] In a color image forming apparatus using a plurality of recording heads according to any one of Items 1 to 9, both ends of an image are recorded at both ends of a group on the most upstream side, and a registration mark is formed on the most upstream side. A color image forming apparatus using a plurality of recording heads for recording.

[Corresponding Embodiment] The first to sixth embodiments correspond to this embodiment.

[Effect] Since the registration mark is printed by the recording heads on the same line in the main scanning direction, there is no shift in the main scanning direction on the left and right, and accurate printing timing can be provided.

(11) [Configuration] In a color image forming apparatus having a configuration of a plurality of heads in which an upstream printhead and a downstream printhead perform printing while overlapping in the main scanning direction, print data inside an overlap width is printed by an upstream printhead. Means common to the downstream recording head;
Each recording head has first signal control means for outputting the recording data of the overlapping portion as recording active dots every other line in one-line recording, and further, each recording head has a recording data of the overlapping portion which is the first recording data. Second signal control means for outputting the recording active dot position shifted by one in the main scanning direction to the signal control means, and further, each of the recording heads sets the recording active dot position in the overlapping portion in the line recording order. Third signal control means for outputting one by one in the main scanning direction, and recording active dots such that recording active dots are alternately recorded by a recording head on the upstream side and a recording head on the downstream side on one recorded line. Fourth signal control means for controlling the first signal control means, the second signal control means and the third signal control means by changing the position,
A color image forming apparatus using a plurality of recording heads.

[Corresponding Embodiment] The seventh embodiment corresponds to the seventh embodiment.

[Effects] The overlapped portions overlap each other in a staggered pattern configuration so that they are not connected to a single recording screen.

[0262] 12. [Configuration] In a color image forming apparatus using a plurality of printheads, an overlap width value is calculated and corrected based on a printhead moving distance value, and print data is shared between an upstream printhead and a downstream printhead. Means for determining whether or not to shift the recording active position of the overlap portion of the downstream recording head by one based on the recording head moving distance value. 12. A control means for causing the recording dots of the upstream recording head and the recording dots of the downstream recording head to overlap in the main scanning direction. Image forming device.

[Corresponding Embodiment] The seventh embodiment corresponds to the seventh embodiment.

[Effect] The slight displacement of the overlapped portion due to the movement of the head can be achieved by shifting one of the patterns of the two heads and varying the overlap width when the recording of the staggered pattern configuration is displaced. It can be hard to see.

13. [Configuration] In a color image forming apparatus having a configuration of a plurality of heads in which an upstream printhead and a downstream printhead perform printing while overlapping in the main scanning direction, print data A in an overlap portion is output from the upstream printhead and the upstream printhead. Means common to the downstream print heads, and the print data B in the overlap portion of each print head becomes equal to the print data B by a value of 1/2 the value of the print data A or by adding the data of the two print heads. A color image forming apparatus using a plurality of recording heads.

[Corresponding Embodiment] The eighth embodiment corresponds to the eighth embodiment.

[Effect] Since the recording dots in the overlapping portion are made common to each head and only the recording value is changed by each head and overlapped, there is an effect that the density unevenness of the head characteristic difference is hardly seen and the connection is seen well. .

14. [Configuration] In a color image forming apparatus using a plurality of printheads, an overlap width value is calculated and corrected based on a printhead moving distance value, and print data is shared between an upstream printhead and a downstream printhead. And interpolating data processing means for interpolating print data based on print dot displacement of the overlap portion of the downstream print head based on print dots of the upstream print head based on the print head moving distance value. 14. A color image forming apparatus using a plurality of recording heads according to claim 13.

[Corresponding Embodiment] The eighth embodiment corresponds to the eighth embodiment.

[Operation and Effect] Since the overlapped portion is slightly displaced by the movement of the head, the data at the recording dot position of one of the recording heads is finely interpolated to generate and record the data by the deviated amount. Together with the effect of the formation, it can be hardly noticeable.

[0271] 15. [Configuration] In the color image forming apparatus using the plurality of recording heads, a means for performing the overlap γ correction process on the data value of the overlapped print data A, and a means for replacing the processed print data C with the print data A And a thirteenth aspect comprising:
A color image forming apparatus using a plurality of recording heads.

[Corresponding Embodiment] The tenth embodiment corresponds to the tenth embodiment.

[Function / Effect] A gamma correction process of the added density value is added to the recording dots of the overlap portion formed by the dot formation of the upstream recording head and the dot formation of the downstream recording head. Therefore, the addition error is corrected, and the difference in image density between the overlapped portion and its peripheral portion is reduced, so that there is an effect that the image can be seen to be well connected.

[0274] 16. [Configuration] In the color image forming apparatus using the plurality of heads, the overlap γ correction processing is configured as a means for processing γ correction for each recording color, wherein the multiple recording head according to claim 13 is used. Color image forming apparatus.

[Corresponding Embodiment] The eleventh embodiment corresponds to this embodiment.

[Function / Effect] Since the γ-correction processing of the density addition value is added to the recording dots of the overlapping portion for each recording color, the addition error of each recording color is corrected, and the overlapping portion and its peripheral portion are corrected. In this case, there is an effect that the image density difference in all colors is reduced and the joint is hardly noticeable.

[0277] 17. [Configuration] In a color image forming apparatus having a plurality of heads in which an upstream printhead and a downstream printhead perform printing while overlapping in the main scanning direction, print data in an overlap portion is stored in the upstream printhead and the downstream printhead. As a means for making common with the recording heads on the side and a control means for enlarging the formation diameter of recording dots in the overlapping portion of each recording head, the potential of the dot control electrode of the ion flow electrostatic recording system is set to the overlapping portion. High voltage control means for variably controlling only the dot potential of
A color image forming apparatus using a plurality of recording heads.

[Corresponding Embodiment] The ninth embodiment corresponds to the ninth embodiment.

[Function / Effect] Since dot diameter enlargement processing is performed as dot control for the overlapped portion, even if the position is slightly shifted, the portion appears blurred. The problem of omission is also solved.

[0280] 18. [Configuration] In a color image forming apparatus using a plurality of printheads, an overlap width value is calculated and corrected based on a printhead moving distance value, and print data is shared between an upstream printhead and a downstream printhead. And a control means for enlarging and changing the formation diameter of the recording dots in the overlap portion of the downstream recording head, the potential of the dot control electrode of the ion flow electrostatic recording method is recorded, and only the dot potential of the overlap portion is recorded. 18. A color image forming apparatus using a plurality of recording heads according to claim 17, further comprising high voltage control means for performing variable control based on a head moving distance value.

[Corresponding Embodiment] The ninth embodiment corresponds to the ninth embodiment.

[Operation and Effect] Since the overlapped portion is slightly displaced due to the movement of the head, the data at the recording dot position of one of the recording heads is subjected to the dot diameter enlargement processing by the amount corresponding to the displacement, and is recorded. If the head does not move, the enlargement process is not performed and the image can be recorded as standard without blurring.

[0283] 19. [Configuration] In a color image forming apparatus having a configuration of a plurality of recording heads in which an upstream recording head and a downstream recording head perform recording while overlapping in the main scanning direction, recording data A in an overlap portion is recorded on the upstream recording head. Based on the data value of the overlapped print data A,
Means for processing the overlap γ correction for each dot of the upstream recording head, means for processing the overlap γ correction for each dot of the downstream recording head for the same recording data A, and their signal control means A color image forming apparatus using a plurality of recording heads.

[Corresponding Embodiment] The twelfth embodiment corresponds to the twelfth embodiment.

[Operation and Effect] The dot recording at the overlap portion is performed at the dot level of the overlap portion by performing separate and dot-specific overlap gamma correction processing by the upstream recording head and the downstream recording head. Since the fine synthesizing process can be performed, there is an effect that the overlapping portion can be made more invisible.

[0286]

According to the present invention, an image and a registration mark are printed together at the time of printing the first color, and at the time of printing of the nth color (n is an integer of 2 or more), the first color and n By detecting the skew amount of the color grain based on the distance between the registration marks, and by changing the print positions of the upstream print head and the downstream print head group in accordance with the skew amount, the partial printing performed by the adjacent print heads is performed. There is provided a color image forming apparatus using a plurality of recording heads for preventing occurrence of a gap or overlap near an image boundary.

[Brief description of the drawings]

FIG. 1 is a top view schematically showing a configuration of a color image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a perspective view of the color image forming apparatus of FIG.

FIG. 3 is a side sectional view of the color image forming apparatus of FIG. 2;

FIG. 4 is a diagram illustrating a state of running of a recording sheet when there is no skew in the first color and no skew in the nth color.

FIG. 5 is a diagram illustrating a running state of a recording sheet in a case where there is no skew in the first color and there is a skew in the nth color.

FIG. 6 is a diagram illustrating a running state of a recording sheet in a case where skew is present in the first color and skew is not present in the nth color.

FIG. 7 is a diagram illustrating a state of running of a recording sheet in a case where skew is present in the first color and skew is present in the nth color.

FIG. 8 is a diagram illustrating a state of a first color image when skew occurs during the formation of the first color image.

FIG. 9 is a diagram illustrating a first correction operation when skew occurs during image formation of a first color.

FIG. 10 is a diagram illustrating a second correction operation when skew occurs during image formation of an n-th color image.

FIG. 11 is a flowchart illustrating a flow of a series of operations of image formation.

FIG. 12 is a top view schematically showing a configuration of a color image forming apparatus according to a second embodiment of the present invention.

13 is a diagram illustrating an operation of a pixel forming unit of a recording head when forming a first color image in the apparatus of FIG. 12;

14 is a diagram illustrating an operation state of a pixel forming unit of a recording head when forming an n-th color image in the apparatus of FIG. 12;

FIG. 15 is a top view schematically illustrating a configuration of a color image forming apparatus according to a third embodiment of the present invention.

FIG. 16 is a top view schematically illustrating a configuration of a color image forming apparatus according to a fourth embodiment of the present invention.

FIG. 17 is a diagram for explaining an operation of adjusting the printing position of the recording head group in response to the occurrence of skew of the recording paper in the apparatus of FIG. 16, showing a state before the start of the adjustment.

FIG. 18 is a diagram illustrating an operation of adjusting the print position of the recording head group in response to the occurrence of skew of the recording paper in the apparatus of FIG. 16, and illustrates a state at the time of starting the adjustment of the upstream recording head group.

19 is a diagram illustrating an operation of adjusting the print position of the recording head group in response to the occurrence of skew of the recording paper in the apparatus of FIG. 16, and illustrates a state at the start of adjustment of the downstream recording head group.

20 is a timing chart showing a state of operation of a detection unit and two motors in an operation of adjusting a print position of a recording head group in response to occurrence of skew of recording paper in the apparatus of FIG.

FIG. 21 is a top view schematically showing a configuration of a color image forming apparatus according to a fifth embodiment of the present invention.

FIG. 22 is a block diagram schematically showing a configuration of a color image forming apparatus according to a seventh embodiment of the present invention.

FIG. 23 is a diagram illustrating a state of dots printed by the apparatus of FIG. 22;

FIG. 24 is a block diagram schematically showing a configuration of a color image forming apparatus according to an eighth embodiment of the present invention.

FIG. 25 is a diagram showing a state of dots printed by the apparatus of FIG. 24;

FIG. 26 is a diagram schematically showing a configuration of a part of a color image forming apparatus according to a ninth embodiment of the present invention.

FIG. 27 is a diagram illustrating a state of dots printed by the apparatus of FIG. 26;

FIG. 28 is a diagram illustrating how dots having different diameters are printed by the apparatus of FIG. 26;

FIG. 29 is a graph showing characteristics of optical density with respect to image data values of dots obtained by forming a latent image twice and dots obtained by forming a latent image once.

FIG. 30 is a block diagram schematically showing a configuration of a part of a color image forming apparatus according to a tenth embodiment of the present invention.

FIG. 31 is a graph showing a correction curve of an output image data value with respect to an input image data value for dot formation by two latent image formations in the apparatus of FIG. 30;

FIG. 32 is a block diagram schematically showing a configuration of a part of a color image forming apparatus according to an eleventh embodiment of the present invention.

FIG. 33 is a block diagram schematically showing a configuration of a color image forming apparatus according to a twelfth embodiment of the present invention.

34 is a graph showing a correction curve of an output image data value with respect to an input image data value for dot formation by two latent image formations in the apparatus of FIG. 33.

[Explanation of symbols]

 1, 2, 5 Recording head 3, 6 Support member 4, 7, 17 Driving source 8 Registration mark 9 Detecting unit 10 Computing unit 11, 12, 19 Driving control unit 13, 14, 18 Elastic member 20 Oscillating member 25 Shaft 30 Recording material

Claims (3)

[Claims] 1. A color image recording apparatus which divides a plurality of recording heads into two or more groups in a sub-scanning direction, performs recording in a main scanning direction, and superimposes respective color images. While holding the recording position,
Means for shifting the recording position of the entire upstream recording head in the main scanning direction; and maintaining the recording position of the downstream recording head group relative to the upstream recording head group with respect to the upstream recording head group. Means for shifting in the main scanning direction, and an upstream printhead group and a downstream printhead group
Oscillating means rotatable in the main scanning direction, registration marks provided on the recording medium, detection means for detecting the registration marks, and arithmetic means for calculating the conveyance state of the recording medium from the positions of the registration marks, Calculating means for calculating the shift amount of the entire print position of the upstream print head group in the main scanning direction and the shift amount of the entire print position of the downstream print head group relative to the upstream print head group in the main scanning direction from the state of conveyance of the print medium A resist mark is printed when recording the first color, and the nth color (n
Is an integer of 2 or more) based on the recording paper transport state calculated from the registration marks detected during the recording, and mainly determines the recording position of the entire upstream recording head group so that the recording of the nth color overlaps the printing position of the first color. The printing position of the entire downstream print head group is shifted in the main scanning direction such that the end of the downstream print head group substantially coincides with the end of the upstream print head group while shifting in the scanning direction. A color image forming apparatus using a recording head. 2. A color image recording apparatus which divides a plurality of recording heads into two or more groups in a sub-scanning direction, performs recording in a main scanning direction, and superimposes each color image. While holding the recording position,
Means for shifting the recording position of the entire upstream recording head group in the main scanning direction; and maintaining the recording position of the downstream recording head group relative to the upstream recording head group with respect to the upstream recording head group. Means for shifting in the main scanning direction, and mounting the upstream printhead group and the downstream printhead group,
Swing means rotatable in the main scanning direction, a registration mark provided on the recording medium, detection means for detecting the registration mark, and arithmetic means for calculating the transport state of the recording medium from the position of the registration mark; Calculation means for calculating the shift amount in the main scanning direction of the print position of the entire upstream print head group and the shift amount of the print position of the entire downstream print head group with respect to the upstream print head group from the conveyance state of the print medium. A resist mark is printed when recording the first color, and the nth color (n
Is an integer of 2 or more) based on the recording paper transport state calculated from the registration marks detected during the recording, and mainly determines the recording position of the entire upstream recording head group so that the recording of the nth color overlaps the printing position of the first color. A plurality of recording heads, which shifts in the scanning direction and shifts the recording position of the entire downstream recording head group in the main scanning direction with a delay of the time when the recording medium moves from the upstream head group to the downstream head group. Color image forming apparatus using the same. 3. A color image forming apparatus using a plurality of recording heads according to claim 1, wherein both ends of the image are recorded by the recording heads at both ends of a group on the most upstream side, and a registration mark is formed. A color image forming apparatus using a plurality of recording heads for performing recording with a most upstream recording head provided outside an image.