JP2006199031A - Positional detection in image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positioning mechanism for an image forming device having a tilt detection mechanism which prevents degradation in printing guality on a recording medium. <P>SOLUTION: This image forming device comprises a recording head having a plurality of nozzle trains which respectively jet out a plurality of ink liquids of different colors to the recording surface of a recording medium which is transported. The image forming device has a transporting mechanism which transports the recording medium for forming images, a carriage and a belt platen which are arranged at positions facing the transporting mechanism. A sensor which detects the relative tilting between the transporting direction and the recording head is arranged. The tilting of the transporting direction to the recording head is detected and calculated, and the positioning mechanism controls the relative tilting from the operation result. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that detects and corrects skew without degrading the print quality of an image recording medium, and more particularly to a technique for positioning by detecting skew.

  2. Description of the Related Art Conventionally, an inkjet image forming apparatus forms an image by ejecting droplets from a large number of nozzles of a recording head onto a recording medium. In particular, in the case where a color image is obtained by sequentially ejecting a plurality of colors of ink onto a recording medium, the print quality deteriorates if the color shift is large.

  For example, in the case of an image forming apparatus using a fixed line head, if skew occurs in which the recording medium conveyance direction and the nozzle array arranged in the line head are inclined, a plurality of colors are displayed at the same location on the recording medium. Color shift occurs without landing on

  According to Patent Document 1, a method for correcting the color misregistration due to the skew is proposed. As shown in FIG. 30, the image forming apparatus includes two recording heads 231 and 232 arranged on the upstream side and one recording head 234 arranged on the downstream side. The upstream recording head groups 231 and 232 are fixed to the support member 233. Further, the downstream recording head group 234 is fixed to the support member 235. The support member 235 is provided so as to be movable with respect to the support member 233.

  The support member 233 is provided so as to be movable with respect to the swing member 239 provided so as to be swingable around the shaft 2310. A detection unit 237 that detects registration marks 236 printed on both sides of the recording member 2311 is provided upstream of the recording heads 231 and 232. A registration mark is printed together with an image by each color head.

The calculation unit 238 detects the skew of the recording member 2311 based on the information from the detection unit 237 that detected the registration mark, and based on the result, the position of the support member 233, the position of the support member 235, and the swing member 239 By controlling the orientation, each color is prevented from shifting.
JP-A-10-35021

  However, in the skew detection by the method shown in Patent Document 1, registration marks are printed on both ends of the wiring medium. For this reason, it is necessary to print a registration mark that is originally unnecessary. If the both ends are not cut after the entire printing is performed, unnecessary printing remains, and the print quality is deteriorated. SUMMARY An advantage of some aspects of the invention is that it provides a correction unit of an image forming apparatus having a skew detection mechanism that does not deteriorate print quality.

  One embodiment of the present invention is an image forming apparatus comprising a recording head having a plurality of nozzle rows that eject ink liquids of a plurality of colors in a first direction onto a recording surface of a recording medium to be conveyed. The image forming apparatus has a transport mechanism for transporting the recording medium in a second direction to form an image on the recording medium, the nozzle rows are disposed at predetermined intervals, and are disposed at positions facing the transport mechanism. And an inclination detector having a sensor that outputs inclination information for generating relative inclination information about an axis perpendicular to the recording surface of the second direction or the transport mechanism and the recording head, and the inclination information. And a correction unit that corrects the relative inclination between the second direction and the recording head based on the result of the calculation.

Preferably, the sensor may be configured to output tilt information for detecting a relative tilt around the axis between the belt that transports the recording medium and the recording head.
Preferably, the sensor may be configured to output inclination information for detecting a relative inclination around the axis between a belt platen on which a belt for conveying the recording medium is disposed and the recording head.

Preferably, the sensor may include at least a light source and a light receiving element that receives light projected from the light source.
Preferably, the light projected from the light source is incident on the light receiving element via a target, the light source and the light receiving element are disposed on one of the recording head or the transport mechanism, and the target is the recording element. It is good also as a structure arrange | positioned at the head or the other of the said conveyance mechanism.

Preferably, the target may be arranged throughout the week of the belt.
Preferably, the sensor may include at least a magnetic member and a magnetic sensor that detects magnetism of the magnetic member.

Preferably, the sensor may be a speed sensor that detects a speed of the recording medium and / or a belt that conveys the recording medium.
Preferably, the speed sensor may be an optical speed sensor.

  Preferably, the optical speed sensor may include means for switching and controlling the optical path of the projection light of the optical speed sensor so that the speed from two directions is detected in a time-sharing manner.

Preferably, the inclination detection unit may include two sets of sensors arranged to be separated from each other in a direction perpendicular to the first direction.
Suitably, the said conveyance mechanism is good also as a structure which has a belt platen.

Preferably, the correction unit may include a tilt mechanism that tilts the transport mechanism around the axis with respect to the recording head.
Preferably, the correction unit may include a tilt mechanism that tilts the recording head around the axis with respect to the transport mechanism.

  Preferably, the transport mechanism may include a positioning portion perpendicular to the axis with respect to the recording head, and the tilt mechanism may be inclined relatively with the positioning portion as a center.

Preferably, the tilt may be controlled by controlling the motor through an engaging portion that is interlocked with the gear of the motor.
Preferably, the recording head integrally includes a pin that is a positioning portion perpendicular to the axis with respect to the transport mechanism, and the pin is elastically deformed so that the transport mechanism is relative to the recording head. It is good also as a structure which inclines.

Preferably, the recording head may have a tilting mechanism that is disposed on a carriage and tilts relatively around the axis between the carriage and the transport mechanism.
Preferably, the correction unit includes a control unit that generates ejection information to be input to the recording head from image information, and the control unit is configured to eject ejection information shifted by a predetermined amount in the nozzle row direction based on the tilt information. It is good also as a structure which produces | generates.

  Preferably, the predetermined amount may be calculated from a distance between a reference position and the nozzle row and the tilt information.

  The present invention makes it unnecessary to print marks other than a desired image in detecting skew feeding due to a deviation from the conveyance direction of the recording medium during image formation on the recording medium, and does not lower the print quality.

Example 1
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 to 9 and below, a first embodiment of the present invention will be described with reference to the drawings.

1 and 2 are configuration diagrams of a positioning structure of the image forming apparatus. FIG. 1 is a side view of an image forming apparatus used in this embodiment. FIG. 2 is a plan view showing the carriage and the periphery of the frame.
This image forming apparatus employs an inkjet method. In such an ink jet image forming apparatus, the conveyance direction of the recording medium 7 is the X-axis direction (sub-scanning direction), and the width direction of the recording medium 7 orthogonal to the X-axis direction is the Y-axis direction (main scanning direction). ), The direction perpendicular to the X-axis direction and the Y-axis direction, and the direction perpendicular to the recording surface of the recording medium 7 and the direction of ink ejection from the recording head is defined as the Z direction (vertical direction).

  The first frames 1 and 2 are provided on both side surfaces of the image forming apparatus, respectively. The connecting frames 5 and 6 are connected between the first frames 1 and 2 by screwing. The second frames 3 and 4 are provided on the inner sides of the first frames 1 and 2, respectively.

  Each of the first frames 1 and 2 includes a medium discharge unit (discharge unit for recording paper) N that discharges the recording medium 7, black (K), cyan (C), magenta (M), and yellow (not shown). The ink supply mechanism for supplying the ink liquid of each color (Y) and an electrical system that requires a control circuit and the like are supported.

  Each of the second frames 3 and 4 includes a medium supply unit (a paper supply unit in the case of recording paper) M that supplies the recording medium 7 into the image forming apparatus, and a rotation shaft (registration roller shaft) in the registration roller unit 10. Both ends of 17 are supported via bearings 23a and 23b. Further, a carriage arm 16 that fits one inside the bearings 23 a and 23 b is fastened to both sides of the carriage 8 by screws.

  Further, the carriage guide mechanisms 24 and 25 shown in FIG. 2B bring the other side of the carriage 8 into contact with the contact portions 5a and 6a of the connection frames 5 and 6 so that the height of the carriage 8 is increased. (Z direction) movement is regulated and placed.

  The carriage 8 includes ink head groups 11k, 11k ′, 11c, which constitute a recording head 11 that ejects ink liquids of black (K), cyan (C), magenta (M), and yellow (Y). 11c ′, 11m, 11m ′, 11y, 11y ′ (hereinafter referred to as ink head groups 11k, 11k ′,..., 11y ′) are held. These ink head groups 11k, 11k ′,..., 11y ′ each have a plurality of ink heads in two rows in a direction perpendicular to the conveyance direction A of the recording medium 7 (Y direction), and there are gaps during image formation. The head nozzle rows are arranged so as to overlap each other so that they cannot be performed.

The ink head groups 11k, 11k ′,..., 11y ′ can print the entire print width in the Y direction of the recording medium 7 and constitute a fixed line head fixed to the recording medium 7 being conveyed.
The belt platen 9 is disposed to face the lower surface of the recording head 11 of the carriage 8 so as to be vertically movable. The belt platen 9 supports, for example, an endless belt-like belt 12 with tension applied by, for example, three platen rollers 13a, 13b, and 13c, and rotates the downstream roller 13b to move the belt 12. The belt 12 is provided with a plurality of holes (not shown), and the recording medium 7 is sucked and held on the belt 12 by sucking air from these holes by a suction mechanism (not shown). As described above, the recording medium 7 is transported in the transport direction A at a constant transport speed by the movement of the belt 12. The belt 12, the three platen rollers 13 a, 13 b and 13 c and the belt platen 9 having a suction mechanism constitute a transport mechanism that transports the recording medium 7 in the transport direction A.

  This belt platen 9 has a roller portion 14b at each end of two platen vertical mechanism arms 14 and 15 which are vertical mechanisms of the belt platen at lower end edges 9a and 9b formed on both sides of the belt platen 9, respectively. 15b.

  These platen up-and-down mechanism arms 14 and 15 are rotatably supported by shafts 14a and 15a in synchronization with the arrow H direction and the arrow I direction, respectively. When these platen up-and-down mechanism arms 14 and 15 rotate synchronously, as shown in FIG. 4, roller portions 14 b and 15 b provided at each end of each platen up-and-down mechanism arms 14 and 15 respectively correspond to the lower ends of the belt platen 9. Roll 99, 9b. Thereby, the belt platen 9 moves up and down in the arrow J direction (Z direction). The roller portions 14b and 15b are rotatably supported by roller shafts 14c and 15c provided on the platen vertical mechanism arms 14 and 15, respectively. The lower end edges 9 a and 9 b of the belt platen 9 are formed on the upstream side and the downstream side in the conveyance direction A (X direction) of the recording medium 7.

  When the belt platen 9 forms an image on the recording surface of the recording medium 7, as shown in FIG. 1, the belt platen 9 and the ink ejection groups of the ink head groups 11k, 11k ′,. The interval is arranged at a height position narrowed to a preset interval for image formation. Further, when the recording medium 7 is clogged or each ink head group 11k, 11k ′,..., 11y ′ is maintained (for example, jam processing), the belt platen 9 is in the belt platen 9 and the carriage 8 as shown in FIG. The ink head groups 11k, 11k ′,..., 11y ′ are arranged at a height position in which the intervals between the ink jetting rollers are set to a predetermined maintenance interval.

  As shown in FIG. 4, each carriage arm 16 is formed to extend downward from both side surfaces of the carriage 8. These carriage arms 16 are formed immediately after the supply portion M of the recording medium 7 in the carriage 8.

  The lower ends of the carriage arms 16 are fitted to bearings 23 a and 23 b that rotatably support the registration roller unit 10 at both ends of the registration roller shaft 17 inside the second frames 3 and 4. The height position for pivotally supporting the registration roller unit 10 makes the upper end surface of each roller 18 of the registration roller unit 10 substantially coincide with the height position of the belt 12 in the belt platen 9 and the roller 18 of the registration roller unit 10. A pair of rollers is provided. The registration roller unit 10 is provided in the Y direction that is substantially orthogonal to the conveyance direction A of the recording medium 7. That is, the registration roller unit 10 is provided in parallel to the ink head groups 11k, 11k ', ..., 11y'.

  The registration roller unit 10 includes a shaft 17 and rollers 18 provided on the shaft 17 at predetermined intervals. As shown in FIG. 2, both ends of the shaft (registration roller shaft) 17 of the registration roller unit 10 are rotatably supported by the second frames 3 and 4 via bearings 23a and 23b, respectively. 23a and 23b are fitted to the carriage arm 16 so as to be integrated with the carriage 8.

  The carriage pins 19 and 20 are fixed to the carriage 8 so as to hang down in the Z direction. That is, the carriage pins 19 and 20 are integrally formed with the recording head 11 held by the carriage 8. The carriage pins 19 and 20 are positioned at both ends in the Y direction, which is the width direction of the recording medium, on the upstream side of the carriage 8 in the conveying direction A of the recording medium 7.

  Each of the carriage pins 19 and 20 is formed in a cylindrical shape from a highly rigid material, and a conical portion is formed at each lower end portion. The carriage pins 19 and 20 are fitted to the belt platen 9 to regulate the positional relationship between the carriage 8 and the belt platen 9, and the conveying posture of the recording medium 7 introduced by the registration roller unit 10 and the recording by the belt platen 9. The conveyance posture of the medium 7 is made substantially coincident.

  On the other hand, at positions on the belt platen 9 facing the carriage pins 19 and 20, positioning holes 21 and 22 for position restriction are provided in the positioning portion as shown in FIG. These positioning holes 21 and 22 are respectively formed at both edges in the Y direction on the upstream side of the belt platen 9.

  One positioning hole 21 fits the carriage pin 19 and is formed in a long hole shape that is long in the substantially Y direction. The dimension of the positioning hole 21 in the X direction is formed so as to be fitted to a diameter substantially the same as the diameter of the carriage pin 19.

  The other positioning hole 22 is fitted with the carriage pin 20 and is formed in a circular shape. The diameter of the positioning hole 21 is formed so as to be fitted to the diameter of the carriage pin 20 so as to be approximately the same.

  In the image forming operation having the above-described configuration, when the recording medium 7 is carried in, the recording medium 7 is regulated in its conveying posture by the rest of the registration roller unit 10, and then the belt platen 9 by the conveying force. It is carried in. The belt platen 9 conveys the recording medium 7 below the ink head groups 11k, 11k ′,.

  On the recording medium 7 being conveyed, the ink liquids of black (K), cyan (C), magenta (M), and yellow (Y) are sequentially supplied from the ink head groups 11k, 11k ′,..., 11y ′. An image is formed by being ejected in the Z (−) direction.

  At this time, the axial direction of the registration roller unit 10 and the conveying direction A by the belt platen 9 are maintained in a perpendicular relationship by the above-described action, and as a result, the positional deviation of each color on the recording medium 7 described above. Is unlikely to occur.

  Further, during maintenance, the platen up-and-down mechanism arms 14 and 15 rotate in synchronization with the axes 14a and 15a, respectively, and the belt platen 9 is lowered as shown in FIG. The intervals between the head groups 11k, 11k ′,..., 11y ′ and the ink ejection ports are expanded to preset maintenance intervals. In this state, the clogging of the recording medium 7 is removed, jam processing, and maintenance of the ink head groups 11k, 11k ',. After completion of the maintenance, the belt platen 9 is lifted again, and the interval between the belt platen 9 and the ink ejection ports of the ink head groups 11k, 11k ′,. It is arrange | positioned in the height position narrowed to the space | interval of.

  Also at this time, since the carriage pins 19 and 20 of the carriage 8 are respectively fitted in the positioning holes 21 and 22 in the belt platen 9 as described above, the positional relationship among the registration roller unit 10, the carriage 8, and the belt platen 9. Is maintained, and the axial direction of the registration roller unit 10 and the conveying direction A by the belt platen 9 are kept perpendicular to each other.

  Therefore, the positional relationship among the registration roller unit 10, the carriage 8, and the belt platen 9 is maintained no matter how many times the vertical movement of the carriage 8 and the belt platen 9 is repeated due to maintenance or the like.

  Next, the main part will be described. As shown in FIG. 5, positioning holes 21 and 22 for position restriction are provided at positions on the belt platen 9 facing the carriage pins 19 and 20, respectively. These positioning holes 21 and 22 are respectively formed at both edges in the Y direction on the upstream side of the belt platen 9. One positioning hole 22 is fitted with the carriage pin 20 and is formed in a circular shape. The diameter of the positioning hole 22 is formed so that it can be fitted to the diameter of the carriage pin 20 so as to be approximately the same.

The other positioning hole 21 is fitted with the carriage pin 19 and is formed in a long hole shape that is long in the substantially Y direction.
The positioning hole 21 is configured in the moving mechanism 50 as shown in FIG. The center of the positioning hole 21 is offset from the center G of the rotating member 51 by d in the Y direction. A worm wheel 51 a is formed on one end face of the rotating member 51 in the Y direction.

  The shaft portion 51 b of the rotating member 51 is fixed to the fixing member 53 via a bearing 52 so as to be rotatable. The fixing member 53 is fixed to the belt platen 9. A motor 54 that is a stepping motor having a worm gear 55 that engages with the worm wheel 51 a is also fixed to the fixing member 53.

The operation will be described with reference to FIG. The distance between the center of the carriage pin 19 and the center of the carriage pin 20 is L, the distance d between the center G of the rotating member 51 and the center of the carriage pin 19, the rotation angle with respect to the center G of the rotating member 51 is θ, and the belt platen 9 The rotation angle with respect to the carriage pin 20 is φ. When the motor 54 is rotated and the worm gear 55 is rotated, the rotating member 51 rotates around the rotation center G in the direction B by an angle θ. Then, the positioning hole 21 and the positioning pin 19 fitted in the positioning hole 21 move m = d × sin θ in the X (+) direction with respect to the belt platen 9. Then, the belt platen 9 rotates in the C direction by φ around the center of the positioning pin 20 with respect to the carriage 8, that is, each of the ink head groups 11k, 11k ′,. Here, φ is sin ⁻¹ (m / L).

  On the other hand, the belt platen 9 has flat lower end edges 9a and 9b of the belt platen 9 placed on roller portions 14b and 15b whose platen vertical mechanism arms have cylindrical outer shapes. Therefore, the belt platen 9 is supported so as to be movable and tiltable in a direction parallel to the XY plane by sliding on the roller portions 14b and 15b. Further, the carriage 8 on which the respective ink head groups 11k, 11k ', ..., 11y' are fixed is fixed to the first frames 1, 2 and the second frames 3, 4.

  Since it is configured as described above, the positioning hole 21 is fixed to the carriage 8 that is fixed to the first frames 1 and 2 and the second frames 3 and 4 by rotating the positioning hole 21 by an angle θ. The belt platen 9 can be tilted around the Z axis by an angle φ with respect to the center of the carriage pin 20. When the belt platen 9 is tilted in the direction opposite to the direction C shown in FIG. 7, the worm gear 55 may be rotated in the direction opposite to the above.

  For example, if the distance of the ink heads 11k and 11y in the conveyance direction of the recording medium is 300 mm, the position of the ink heads 11k and 11y in the Y direction is a half pitch of 300 dpi, that is, 0.042 mm (= 25.4 / 300/2). ), The belt platen 9 is tilted with respect to the carriage 8 for correction as follows.

The belt platen 9 may be inclined with respect to the carriage 8 by φ = 0.0081 degrees (= sin −1 (0.042 / 300)).
For example, if L = 400 mm and d = 10 mm, θ can be set to 0.32 degrees from the previous equation. The motor 54 is rotated until the rotating member 51 rotates 0.32 degrees. In this way, the belt platen 9 can be tilted around the Z axis with respect to the carriage 8, that is, the ink head groups 11k, 11k ′,..., 11y ′ and the registration roller portion 10 integrally formed therewith. Thereby, when the conveying direction of the belt 12 or the conveying direction of the recording medium 7 is skewed with respect to the ink head groups 11k, 11k ′,..., 11y ′, the belt platen 9 is inclined with respect to the carriage 8. Thus, the skew can be corrected.

The sensor will be described.
In this embodiment, the inclination around the Z axis with respect to the carriage 8 of the belt platen 9, that is, the ink head groups 11k, 11k ′,. The Z axis is perpendicular to the conveyance direction X of the recording medium 7, perpendicular to the recording surface of the recording medium 7 on the belt platen 9, and in the flight direction of ink droplets ejected from the ink head 11 k or the like. Parallel direction.

As shown in FIG. 8, a reflection target 63 is disposed as a target adjacent to the positioning holes 21 and 22 disposed at both ends on the upstream side of the belt platen 9.
The reflection target 63 is composed of a square glass flat plate, and its surface is divided into three by a boundary line parallel to the Y direction. The central reflecting surface 63a has a high reflectance of, for example, 95% or more for light with a wavelength of 900 nm, and the reflecting surfaces 63b on both sides thereof have a low reflectance of, for example, 5% or less for light with a wavelength of 900 nm. It is coated like this.

  An LED 61 and a light receiving element 62 are arranged on the carriage 8 so as to face the reflection target 63. The LED 61, the light receiving element 62, and the reflection target 63 constitute sensors 60A and 60B.

  The light receiving surfaces of the light receiving elements 61 of the sensors 60A and 60B are divided into two parts a1, a2, and b1, b2 from the upstream side by a boundary line parallel to the Y direction. The LED 61 emits near infrared light having a wavelength of 900 nm. The divergent light or parallel light emitted from the LED 61 is projected onto the reflection target 63. The outer shape of the light at that time is slightly larger than the width of the central reflecting surface 63a in the X direction, as shown in FIG. The LED 61, the reflection target 63, and the light receiving element 62 are arranged so that the oval light reflected by the central reflecting surface 63 a having a high internal reflectance of the light enters the center of the light receiving element 62. The two LEDs 61, the light receiving elements 62, and the reflection target 63 are arranged so that their centers are on a straight line parallel to the Y direction as viewed from the Z direction.

  The light receiving element 62 that receives the light emitted from the LED 61 via the reflection target 63 outputs an electrical signal from the divided light receiving surfaces a1, a2, and b1, b2, and as shown in FIG. 9, (a1 + b2) − ( Inclination information is obtained by arithmetic processing as in a2 + b1). This inclination information is obtained by taking the sum signal of the diagonals of the light receiving surfaces a1 and a2 and b1 and b2 divided when viewed as shown in FIG. In addition, if the inclination information is normalized by the sum signal of all four light receiving surfaces and is set to ((a1 + b2) − (a2 + b1)) / (a1 + a2 + b1 + b1), the error of the inclination information due to the change in the amount of light is further reduced.

As shown in FIG. 10, the belt platen 9 is rotated in the direction indicated by the arrow in FIG. Assuming that

  At this time, since the center of the reflection target 63 is shifted from the center of the light from the LED 61, the reflected light from the center also moves to the divided light receiving surfaces a2 and b1 as shown in FIG. As a result, the signals from the light receiving surfaces a2 and b1 increase, the signals from the light receiving surfaces a1 and b2 decrease, and the tilt information changes from 0 to the (−) side. Therefore, the inclination state of the belt platen 9 and the carriage 8 around the Z axis can be detected.

  Note that when the belt platen 9 is translated in the Y direction, the direction of the movement is parallel to the boundary line of the reflection target 63, and the tilt information does not change. Further, when the belt platen 9 is translated in the X direction, the light incident on the light receiving element 62 also moves in the X direction. For example, signals from the light receiving surfaces a1 and b1 increase, and light from the light receiving surfaces a2 and b2 increases. Although the signal decreases, the inclination information is calculated as (a1 + b2) − (a2 + b1), so the change in inclination information due to movement in the X direction is canceled and does not change.

  Further, when the belt platen 9 is moved in the Z direction with respect to the carriage 8 in order to correspond to recording media having different thicknesses, the optical axis of light from the LED 61 to the light receiving element 62 via the reflection target 63 is On the YZ plane, the reflection target 63 also has a boundary parallel to the YZ plane, and the surface of the light receiving element 62 is also divided by a dividing line parallel to the YZ plane. Therefore, even if the belt platen 9 moves up and down and the reflection target 63 moves up and down, the light on the reflection target 63 and the light receiving element 62 only moves in a direction parallel to the YZ plane. It does not change.

Therefore, only the inclination state around the Z axis between the belt platen 9 and the carriage 8 can be detected.
The detected inclination information is input to the control unit 49 of the image forming apparatus, the rotation of the motor 54 is controlled from the control unit 49, and the inclination information is controlled to be 0, whereby the belt platen 9 with respect to the carriage 8 is controlled. .., 11y ′ can correct the direction of transport of the belt 12 with respect to each of the ink head groups 11k, 11k ′,..., 11y ′, and the skew of the transport of the recording medium 7 can be corrected.

If the image is known to be optimal when the inclination information is a predetermined value other than 0 by an initial color misregistration inspection or the like, control is performed so that the predetermined value is obtained.
Further, the belt platen 9 is tilted by a predetermined angle, for example, 0.005 degrees to form an image on the recording medium 7, and the optimum inclination of the belt platen 9 that minimizes the color shift is determined from the relationship between the angle and the color shift of the image. It can also be set.

  As a case where the carriage 8 and the belt platen 9 are inclined around the Z-axis, for example, the second frames 3 and 4 may be deformed with respect to the first frames 1 and 2 due to external impact or vibration. is there. Further, the carriage pins 19 and 20 that restrict the relative positions of the carriage 8 and the belt platen 9 may be bent and deformed due to external impact or vibration.

Even in these cases, as described above, the relative inclination of the carriage 8 and the belt platen 9 around the Z axis can be detected and corrected.
In this example, the registration roller 10 is integrally formed on the carriage 8 side, and the belt platen 9 is tilt-corrected with respect to the registration roller 10 and the carriage 8, so that even if the belt platen 9 is tilted with respect to the carriage 8, The relative position of the carriage 8 does not deviate.

  In addition, since the belt platen 9 is tilt-corrected around an axis perpendicular to the recording medium 7 on the belt platen 9 that opposes the carriage 8 on which the ink head is disposed, the recording medium 7 and the ink head even if the belt platen 9 is tilted. The interval between and does not change. For this reason, the recording medium 7 and the ink head are close to each other, so that the jam does not easily occur.

  Further, the carriage 8 on which all the ink heads for each color are arranged is integrated, and the tilt position with respect to the belt platen 9 is corrected. Therefore, even if the belt platen 9 is tilt-corrected, the Y direction of each color is corrected. The relative position does not shift. Further, one set of the inclination correction unit is sufficient.

  On the other hand, for example, when the ink head for each color is corrected with respect to the belt platen 9, the position of each color in the Y direction is shifted, resulting in a color shift. In addition, a plurality of inclination correction units are required for each color, which increases the size of the apparatus.

Further, since infrared light is used as a light source instead of visible light, it is hardly affected by ink stains such as a reflection target.
Although a part of the sensor is fixed to the carriage 8, any member may be used as long as it is a member integrated with the ink head. For example, the sensor may be fixed to the ink head. In addition, when the positional deviation between the carriage 8 and the frame of the image forming apparatus that fixes the carriage 8 is small, a part of the sensor may be arranged on the frame or the like instead of the carriage 8.

The same effect can be obtained by disposing the reflection target 63 on the carriage 8 and disposing the LED 61 and the light receiving element 62 on the belt platen 9.
Further, although the two sensors 60A and 60B are arranged on the upstream side of the belt platen 9 and on both sides in the Y direction, they may be arranged on the downstream side.

Further, the two sensors 60 </ b> A and 60 </ b> B can be disposed at one end in the Y direction so as to be separated from each other in the X direction, or can be disposed on the diagonal of the belt platen 9.
Moreover, although LED was used for the light source, LD and other light sources may be used. In addition, a light receiving element such as a PD having a light receiving surface divided into two is used as the light receiving element, but the surface is not divided, and a position for outputting a signal related to the barycentric position of the intensity of light projected on the light receiving surface. A detection element (for example, S4583-04 from Hamamatsu Photonics) or a CCD sensor may be used.

  In the above configuration, not the moving belt 12 that constitutes a part of the belt platen 9 that is a conveyance mechanism or the recording medium 7 that is conveyed by the belt 12, but the fixed portion of the carriage that does not move in the conveyance direction A of the belt platen 9. An inclination with respect to 8 was detected. However, when the belt platen 9 is tilted, the belt 12 driven by the platen rollers 13a, 13b, and 13c constituting a part of the belt platen 9 is also tilted at the same angle.

  Further, when the belt platen 9 is tilted, the conveyance direction of the recording medium 7 conveyed by the belt 12 is also inclined by the same angle. Therefore, in the present embodiment, there is an error with respect to the inclination of the conveyance direction of the recording medium 7 with respect to the carriage 8, that is, the ink head 11 k fixedly arranged on the carriage 8, but the inclination of the fixing portion of the belt platen 9 related thereto. It is substituted by detecting. In the belt 12 and the recording medium 7 moving in the transport direction A, the reflectance is likely to fluctuate due to the movement. The recording medium 7 has various surface reflectances, sizes, surface deflections, etc., but is fixed to the fixing part of the belt platen 9 and moves in the conveying direction A with respect to the LED 61 and the light receiving element 62. Since the reflective target 63 that is not detected is detected, there is an advantage that the detection is stabilized. Further, since it is not necessary to print a specific reflective target on the recording medium 7, the print quality is not deteriorated.

With the above-described configuration, the carriage 8, that is, the ink head 11 k that is integrally formed with the carriage 8, the belt platen 9 that is a conveyance mechanism, that is, the moving direction of the belt 12 disposed thereon, that is, the recording medium 7 that is conveyed by the belt 12. It is possible to detect a relative inclination about the Z axis that is perpendicular to the recording surface of the recording medium with respect to the transport direction. Further, by correcting the inclination around the Z axis which is perpendicular to the recording surface of the recording medium of the belt platen 9, the relative inclination around the Z axis is corrected, and the ink head which lands on the recording medium 7. It is possible to correct the landing deviation of the ink from the group and reduce the color deviation, and the quality of the image formed on the recording medium 7 can be improved.
(Example 2)
A second embodiment of the present invention will be described below. A description of the same configuration as in the first embodiment will be omitted, and only different portions will be described below.

  In this embodiment, sensors 70A and 70B are used as shown in FIG. An LED 71 is arranged on the belt platen 9 without using a reflection target, and a light receiving element 72 whose light receiving surface is divided into four parallel to the X and Y axes is arranged on the carriage 8 side as shown in FIG. . On each light receiving surface, c1, c2, c3, and c4 are divided and arranged as light receiving elements 72 of the sensor 70A, and d1, d2, d3, and d4 are divided and arranged as light receiving elements 72 of the sensor 70B.

  By receiving light from the LED 71, electric signals c1e, c2e, c3e, c4e, d1e, d2e, d3e, d4e are output from the light receiving surfaces c1 to c4 and d1 to d4. Based on this electric signal, the inclination around the Z axis, the position in the X direction, and the position in the Y direction are calculated according to the following calculation formula (the calculation method is not limited, for example, an operational amplifier or a CPU may be used). Thus, the relative position and angle of the belt platen 9 with respect to the carriage 8 in the three directions can be detected. The following three inclinations or position information may be normalized by dividing by the total output (c1e + c2e + c3e + c4e + d1e + d2e + d3e + d4e) of the light receiving surface as in the first embodiment.

Inclination around the Z axis = (c1e + c2e + d3e + d4e) − (c3e + c4e + d1e + d2e)
Position in X direction = (c1e + c2e + d1e + d2e) − (c3e + c4e + d3e + d4e)
Y-direction position = (c1e + c3e + d1e + d3e) − (c2e + c4e + d2e + d4e)
By detecting the inclination around the Z axis, the color shift can be corrected as in the first embodiment.

  For example, when the belt platen 9 moves in the X direction due to external vibration or the like, the color in the transport direction of each color shifts in the X direction. This is detected by detecting the positional deviation of the belt platen 9 in the X direction and based on this positional deviation amount. Further, color misregistration can be reduced by controlling the ink ejection timing of each ink head.

  Further, when the belt platen 9 moves in the Y direction due to external vibration or the like, the color in the transport direction of each color shifts in the Y direction. In this case as well, this positional shift is detected by detecting the positional displacement of the belt platen 9 in the Y direction. Based on the amount, the ejection position in the nozzle row direction with respect to a predetermined image of each ink head can be input and controlled as ejection information obtained by shifting the ejection position by a predetermined nozzle, and color misregistration can be reduced.

  According to the said structure, a reflective target is unnecessary and a structure can be simplified. Further, not only the rotational deviation of the carriage 8 and the belt platen 9 around the Z axis but also the positional deviation in the X axis and Y axis directions can be detected and used for color misregistration correction and the like.

The light receiving element 72 may be disposed on the belt platen 9 and the LED 71 may be disposed on the carriage 8 side.
(Example 3)
A third embodiment of the present invention will be described with reference to FIGS. A description of the same configuration as in the first embodiment will be omitted, and only different portions will be described below.

  The positional relationship between the magnet 81, which is a magnetic member, and each Hall element (magnetic sensor) is shown in FIGS. Each of the sensors 80A and 80B includes a magnet 81 disposed on the belt platen 9 and two hall elements 82a and 82b or 83a and 83b disposed in the X direction disposed on the carriage 8. Then, the inclination is detected by using the difference in magnetic field strength depending on the magnetic field distribution of the magnet 81 and the position of each Hall element.

  Specifically, each Hall element is located at the position of x1, x2 of the magnetic field distribution in the X direction at the Z direction position of the Hall elements 82a, 82b, 83a, 83b separated by the same distance in the Z direction by the magnet 81 shown in FIG. 82a (position of x1), 82b (position of x2) and 83a (position of x1), 83b (position of x2) are arranged.

  Therefore, the tilt information can be calculated by calculating (82ae + 83be) − (82be + 83ae) based on the outputs (electric signals corresponding to the magnetic field strength) 82ae, 83be, 82be, 83ae of each Hall element. it can.

Each Hall element may be arranged on the belt platen 9 and a magnet 81 may be arranged on the carriage 8 side.
Although the Hall element is used as the magnetic field detection sensor, other magnetic field detection sensors can be used.

In the case of the present embodiment, since light is not used, there is an effect that the tilt information is not affected even if ink stains or paper dust is present.
Example 4
A fourth embodiment of the present invention will be described below with reference to FIGS. A description of the same configuration as in the first embodiment will be omitted, and only different portions will be described below. In this embodiment, the skew of the belt 12 with respect to the carriage 8 is detected.

The sensors 90A and 90B are disposed at one end in the Y direction of the belt 12 and separated in the X direction.
A reflection target 93 is formed as a target at one end in the Y direction throughout the week of the belt 12. A reflection part 93a having a high reflectance is formed in the center, and a low reflection part 93b having a low reflectance is formed on both sides thereof.

  An LED 91 and a light receiving element 92 having a light receiving surface divided into two in the X direction are arranged on the carriage 8 so as to be arranged in the X direction. The light receiving element 92 is divided as e1 and e2 on the 90A side, and is divided as f1 and f2 on the 90B side. Each light receiving element outputs electrical signals e1e, e2e, f1e, f2e according to the amount of light received.

  As shown in FIG. 17, the light emitted from the LED 91 is projected onto the reflection target 93, and the strong reflected light from the reflecting portion 93 a enters the light receiving element 92. By calculating the output of the divided light receiving surface of the light receiving element 92 as (e1e + f2e) − (e2e + f1e), the inclination of the belt platen 9 around the Z axis with respect to the carriage 8 can be obtained. As a result, color misregistration can be corrected in the same manner as in the first embodiment.

  In the case of this embodiment, since the inclination of the belt 12 that directly conveys the recording medium 7 is detected instead of the fixing part of the belt platen 9, even if the inclination deviation between the fixing part of the belt platen 9 and the belt 12 occurs. As a result, the detection accuracy of the skew of the recording medium 7 with respect to the carriage 8 is higher and the correction accuracy is higher.

In place of the LED 91 and the light receiving element 92, two line CCDs whose sensors extend in the Y direction,
The skew of the belt can also be detected by arranging the sensor 90A, 90B at the position of the LED 91, detecting the Y-direction edge of the reflection target 93 of the belt 12, and comparing the images of the two line CCDs. .

  If the magnetic member is printed in stripes on the belt 12 instead of the optical sensor, the skew can be detected by the magnetic sensor. In this case, since light is not used, there is an effect that the tilt information is not affected even if there is dirt or paper dust on the ink.

  As shown in FIG. 18, the LED 91 is arranged on the fixing portion of the belt platen 9, and a plurality of holes 94 arranged linearly continuously in the X direction are opened in the entire week of the belt 12 to receive light through the holes 94. Even if the light is projected onto the element 92, the light transmitted through the hole 94 according to the position of the belt 12 in the Y direction moves in the Y direction on the light receiving element 92, and thus can be detected in the same manner.

If the belt 12 is made of a material having a high transmittance with respect to the light from the light source used in place of the hole 94, a plurality of circular light transmitting portions arranged in a straight line having different transmittances, not openings, or continuous The striped light transmission part has the same function.
(Example 5)
FIG. 19 A fifth embodiment of the present invention will be described below.

A description of the same configuration as in the first embodiment will be omitted, and only different portions will be described below. In the present embodiment, the conveyance direction of the recording medium is directly detected by a sensor.
In the carriage 8, two laser Doppler measuring devices (optical speed sensors) 100 A and 100 B convey the recording medium 7 with the respective outgoing optical axes at an angle of 45 degrees at the center in the Y direction of the belt 12 as shown in FIG. It arrange | positions so that speed may be measured substantially linearly.

  With this configuration, when the conveyance direction of the recording medium 7 is parallel to the Y-axis, the arrow D shown in FIG. 21 is obtained, and the laser Doppler measuring devices 100A and 100B perform the conveyance speed of the recording medium 7. Are detected, and the same velocity information of g1 and h1 is output.

However, when the conveyance direction of the recording medium 7 is as indicated by the θ inclination D ′ arrow from the Y axis, the outputs of the laser Doppler measuring devices 100A and 100B increase and decrease as g2 and h2.
Therefore, the conveyance direction of the recording medium can be directly detected by calculating the differential of the outputs of the laser Doppler measuring devices 100A and 100B.

  In the case of this embodiment, since the recording medium conveyance direction can be detected directly, even if there is a tilt deviation between the belt platen 9 and the belt 12 or a slippage between the belt 12 and the recording medium 7, the detection error is detected. Detection accuracy is high.

  In this embodiment, two laser Doppler measuring instruments are used, but one may be switched and used as shown in FIG. The light emitted from the laser Doppler measuring device 100 enters the liquid crystal shutter 101. When the liquid crystal shutter 101 reflects light, the light is projected onto the recording medium 7 via the mirror 102. When the liquid crystal shutter 101 transmits light, the light is projected onto the recording medium 7 via the mirrors 103 and 104.

By switching the liquid crystal shutter 101 in a short time, even one laser Doppler measuring device can detect the speed from two directions in a time-sharing manner, and can be configured at low cost.
In this embodiment, the speed of the recording medium is detected. However, the speed of the belt may be detected. In this case, stable tilt information can be obtained even if the reflectance or the like changes depending on the type of the recording medium. As a matter of course, light is projected to a belt at the end in the Y direction rather than the gap between the recording media being conveyed or the width of the recording medium.
(Example 6)
A sixth embodiment of the present invention will be described below with reference to FIGS. Except for the explanation part, it is the same as the first embodiment. The same number is assigned to the same function.

  In the present embodiment, two carriage pins 19 and 20 and two electric cylinders 110 and 111 are used as an inclination driving mechanism for the belt platen 9. Positioning holes 21 and 22 are provided on the belt platen 9 at positions facing the stainless steel carriage pins 19 and 20. The positioning hole 21 is formed on the belt platen 9 so as to be a long hole substantially in the Y direction, and the moving mechanism 50 as in the first embodiment is not configured. The positioning hole 22 is fitted with the carriage pin 20 as in the first embodiment, and is formed in a circular shape.

  Electric cylinders 110 and 111 are arranged on both sides of the belt platen 9 in the Y direction on the X (+) side. The electric cylinders 110 and 111 have the same configuration. The electric cylinders 110 and 111 have cylinders 110a and 111a, respectively, and the cylinders 110a and 111a move straight in the extending direction.

Protrusions 8 a and 8 a protruding in the Z (−) direction are formed on both sides in the Y direction on the X (+) side of the carriage 9.
When the belt platen 9 is at the image forming position, the tips of the cylinders 110a and 111a are in contact with the protrusions 8a and 8a, respectively.

As in the first embodiment, sensors 60A and 60B (not shown) for detecting the inclination of the belt platen 9 around the Z axis with respect to the carriage 8 are arranged.
FIG. 24A shows a case where there is no inclination around the Z axis of the belt platen 9 with respect to the carriage 8. In this state, the tips of the cylinders 110a and 111a protrude from the electric cylinders 110 and 111 by the same length, and are in contact with the protrusions 8a.

  When the belt platen 9 is tilted about the Z axis with respect to the carriage 8, for example, as shown in FIG. 5B, the protruding length of the cylinder 110a of the electric cylinder 110 is shortened, and the cylinder 111a from the electric cylinder 111 is Increase the protruding length. The belt platen 9 receives rotational torque about the Z axis with respect to the protrusions 8a and 8a, and the tips of the carriage pins 19 and 20 are bent in the opposite direction of the X direction as shown by 19a and 20a in FIG. The belt platen 9 is tilted around the Z axis with respect to the carriage 8.

The material, diameter, and length are appropriately selected so that the carriage pins 19 and 20 can be easily bent in the X direction by the torque around the Z axis generated by the electric cylinders 110 and 111.
By using signals from sensors 60A and 60B (not shown) that detect the inclination of the belt platen 9 about the Z axis relative to the carriage 8, the inclination of the belt platen 9 about the Z axis relative to the carriage 8 can be corrected to reduce color misregistration.

In the present embodiment, the electric cylinders 110 and 111 are pressed against the carriage 8, but the first frames 1 and 2 may be fixed to the carriage 8.
Further, a gear such as a rack and pinion may be combined instead of the electric cylinder in which the cylinder moves directly.

  According to the present embodiment, the support mechanism for tilting the belt platen 9 utilizes the elastic deformation of the carriage pins 19 and 20 which are relative positioning members of the carriage 8 and the belt platen 9. Therefore, the moving mechanism 50 as in the first embodiment is unnecessary and the configuration is simplified.

In the present embodiment, two elastically deformed pins having a circular cross section are used. However, the material is not limited to this, and the material may be steel other than stainless steel, other metals such as phosphor bronze, resin, hard rubber, or the like. The pin shape may be any shape as long as it is elastically deformed, such as a square cross section or a conical shape.
(Example 7)
A seventh embodiment of the present invention will be described below with reference to FIGS. Except for the explanation part, it is the same as the first embodiment. The same number is assigned to the same function.

  In the present embodiment, the belt platen 9 does not move up and down (Z direction), is fixed, and the up and down moving mechanism 112 is arranged on the carriage 8, so that the carriage 8 is the first frame in a maintenance operation or the like. Moves up and down with respect to 1 and 2. The moving mechanism can be configured by known means such as a slide rail, a drive motor, and a gear.

  A base plate 113 is fixed to the first frames 1 and 2. A pin 114 is fixed at the center of the X (−) side. A motor 117 having a rotating lead screw 117a is fixed at the center of the X (+) side.

  The belt platen 9 has a bottom plate 116 and a rib 115 fixed to the Z (−) side. The belt platen 9 is slidably mounted on the upper surface of the base plate 113 with the lower surface of the bottom plate 116. A positioning hole 116a is formed at a position corresponding to the pin 114 at the center of the bottom plate 116 in the X (−) direction, and the pin 114 is rotatably inserted into the positioning hole 116a. A female screw 118 cut in half so as to be screwed into the lead screw 117a is fixed to the center of the rib 115 arranged on the X (+) side of the belt platen 9.

With this configuration, the belt platen 9 is configured to be rotatable about the Z axis about the pin 114 with respect to the base plate 113.
Further, by rotating the lead screw 117a of the motor 117 and moving the female screw 118 in the Y direction with respect to the motor 117, the belt platen 9 is rotated around the Z axis about the pin 114 with respect to the base plate 113. To drive.

By configuring as described above, the color misregistration can be reduced by correcting the inclination of the belt platen 9 around the Z axis with respect to the carriage 8 without directly positioning the belt platen 9 and the carriage 8.
(Example 8)
27 and 28 are diagrams showing the eighth embodiment. The eighth embodiment of the present invention will be described below. Except for the explanation, it is the same as the first embodiment and the seventh embodiment. The same number is assigned to the same function.

  In the present embodiment, the belt platen 9 is configured to be movable up and down (Z direction) as in the first embodiment. Further, the belt platen 9 is not configured to be tiltable about the Z axis with respect to the first frames 1 and 2, and the carriage 8 is configured to be tiltable about the Z axis.

The connection frames 120 and 121 are fixed so as to connect the connection frames 5 and 6 in the Y direction.
A pin 114 is fixed to the center of the connecting frame 120 in the Y direction. A motor 117 having a rotating lead screw 117a is fixed to the center of the connecting frame 121 in the Y direction.

  A contact surface 8 b is formed on the lower surface of the carriage 8 on the X (−) side, and a positioning hole 8 a is formed at a position corresponding to the pin 114 in the center in the Y direction. A fixing surface 8c is formed on the lower surface of the carriage 8 on the X (+) side, and a female screw 118 cut in half so as to be screwed into the lead screw 117a is fixed. The positioning hole 8a is inserted into the pin 114, and the contact surface 8b is slidably placed on the upper surface of the connection frame 120.

Both ends of the registration roller unit 10 are held by the connecting frames 5 and 6.
With this configuration, the carriage 8 is configured to be rotatable about the Z axis around the pin 114 with respect to the connecting frames 120 and 121, that is, the first frames 1 and 2 and the belt platen 9.

  By rotating the lead screw 117a of the motor 117 and moving the female screw 118 in the Y direction with respect to the motor 117, the carriage 8 is rotationally driven around the Z axis about the pin 114 with respect to the belt platen 9. . Since the registration roller unit 10 is held by the connecting frames 5 and 6 and does not rotate around the Z axis integrally with the carriage 8, the registration roller unit 10 and the belt platen 9 are not rotated even if the carriage 8 is rotated around the Z axis. The inclination does not change and the recording medium 7 is conveyed correctly.

By configuring as described above, it is possible to correct the inclination around the Z axis of the recording head 11 fixed to the carriage 8 with respect to the belt platen 9 and to reduce color misregistration.
In this embodiment, since the transport mechanism is not tilted, it is difficult to tilt the transport mechanism facing the recording head. For example, an image forming apparatus having a large transport mechanism with respect to the recording head, or continuous paper transported by a roll is used. It is also suitable for an image forming apparatus.

In the present embodiment, the carriage to which the recording head is fixed is tilted. However, for example, when the four color ink head groups are integrated recording heads, the recording head may be tilted.
In this embodiment, the drive mechanism for the tilt mechanism around the Z-axis is disposed between the carriage and the connecting frame. However, the drive mechanism for the tilt mechanism around the Z-axis is provided between the carriage and the belt platen similar to the sixth embodiment. It can also be arranged.

In this embodiment, the carriage is slid around one pin and tilted. However, as in the sixth embodiment, the carriage may be configured by an elastically deformed pin disposed between the carriage and the belt platen. .
Example 9
FIG. 29 is a diagram illustrating the ninth embodiment. The ninth embodiment of the present invention will be described below. Except for the explanation part, it is the same as the first embodiment. The same number is assigned to the same function.

  In this embodiment, the moving mechanism 50 is not provided in the first embodiment, and the belt platen 9 is not configured to be tiltable around the Z axis with respect to the recording head 11. In the present embodiment, the color misregistration due to the inclination is corrected by correcting the ejection information instead of correcting the inclination mechanically.

  As shown in FIG. 29A, the inclination information obtained from the output signals of the sensors 60A and 60B for detecting the inclination of the belt platen 9 around the Z-axis with respect to the carriage 8 similar to that of the first embodiment is used as the control unit 49. To input. Also, image information from the host computer 123 is sent to the control unit 49 to generate ejection information, and the ejection information is input to each ink head group 11k, 11c, 11m, 11y, and each ink head group 11k, 11c, 11m. , 11y nozzles 124k, 124c, 124m, and 124y, ink is ejected onto the recording medium 7. In FIG. 29, the ink head groups 11k, 11k ′, 11c, 11c ′, 11m, 11m ′, 11y, and 11y ′ are simplified to be ink head groups 11k, 11c, 11m, and 11y each having one nozzle row. . In FIG. 29, as an example of ejection from each of the nozzles 124k, 124c, 124m, and 124y, nozzles that eject are represented by black circles, and nozzles that do not eject are represented by white circles.

  FIG. 29B shows a case where the belt platen 9 is tilted by φ with respect to the Z-axis tilt. In this case, since the recording medium 7 is conveyed by the inclined belt platen 9, the most downstream ink with respect to the position where the black ink ejected from the most upstream ink head row 11 k lands on the recording medium 7. The position where the yellow ink ejected from the head row 11 y lands on the recording medium 7 is the maximum color shift amount S in the width direction of the recording medium 7 on the recording medium 7.

  The distance in the X direction between the nozzle 124k and the nozzle 124c is qc, the distance in the X direction between the nozzle 124k and the nozzle 124m is qm, the distance in the X direction between the nozzle 124k and the nozzle 124y is qy, and the arrangement pitch in the Y direction of each nozzle is p. And The control unit 49 calculates the following shift amounts rc, rm, and ry. Each value of the shift amounts rc, rm, and ry is an integer obtained by rounding off after the decimal point.

rc = (qc · tanφ) / p
rm = (qm · tanφ) / p
ry = (qy · tanφ) / p
The control unit 49 generates discharge information in which the discharge nozzle position is shifted in the nozzle row direction by the value of the shift amount rc, and inputs the discharge information to the ink head group 11c. Similarly, discharge information is generated by shifting the discharge nozzle position in the nozzle row direction by the value of the shift amount rm, the discharge information is input to the ink head group 11m, and the discharge nozzle position in the nozzle row direction by the value of the shift amount ry. Is generated, and the discharge information is input to the ink head group 11y. The state after correction in FIG. 29C is a state in which ejection information corrected by shifting to each of the ink head groups 11c, 11m, and 11y is input when the shift amounts rc = 1, rm = 1, and ry = 2. Show.

  Since it is configured as described above, even if the belt platen 9 is tilted around the Z axis with respect to the carriage 8, that is, the recording head 11, the ejection information input to the recording head 11 is shifted by a predetermined amount in the nozzle row direction according to the inclination. As a result, the color misregistration amount S in the Y direction of each color of ink landed on the recording medium 7 can be reduced to half or less of the nozzle pitch.

  The maximum width in the Y direction of each of the nozzles 124k, 124c, 124m, and 124y of each ink head group 11k, 11c, 11m, and 11y is greater than the maximum print width in accordance with the predicted maximum displacement amount of the ejection nozzles. It is preferable to widen the width.

  In this embodiment, since the color misregistration in the Y direction can be corrected without a mechanical mechanism for correcting the relative inclination of the carriage 8 and the belt platen 9 about the Z axis, an inexpensive and small image forming apparatus can be obtained. Can do.

  In the present embodiment, the amount of displacement of the discharge nozzles of the nozzles 124c, 124m, and 124y is determined with the black nozzle 124k as a reference position. However, for example, the center of the nozzles 124c and 124m, another nozzle position such as 124y, or a position shifted from the position may be used as a reference.

For example, the following configuration may be used. The inclination correction unit is not particularly limited.
The tilt mechanism of the carriage or belt platen is not particularly limited, and may be a tilt mechanism having various drive mechanisms such as a piezoelectric actuator, an air cylinder, a voice coil motor, a gear, a cam, and a belt. Also, the support mechanism of the tilt mechanism is not particularly limited, and support mechanisms using various rolling bearings, slide bearings, link mechanisms, elastic members, and the like can be used.

Further, the recording medium conveyance mechanism is not limited to a special one, and may be a roller conveyance, a moving table or the like in addition to the belt platen.
Further, instead of a configuration in which a plurality of recording heads are fixed to the carriage, an integrated recording head having a plurality of nozzle rows may be used. Further, although a plurality of ink heads for one color are combined in the width direction of the recording medium, one long ink head may be used.

Further, although four color recording heads are arranged, the present invention can be suitably applied to any image forming apparatus in which two or more rows of recording heads are arranged.
Although the tilt correction mechanism of the tilt correction unit is arranged in the carriage to which the recording head is fixed, it may be configured in another member integrated with the recording head or the recording head itself. Further, although the tilt correction mechanism of the tilt correction unit is arranged in the recording medium transport mechanism, other members integrated with the transport mechanism may be used.

  Further, the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment.

For example, some constituent elements may be deleted from all the constituent elements shown in the embodiment, and further, constituent elements over different examples may be appropriately combined.
The present invention is not limited to the above-described embodiment, and various improvements and modifications can be made without departing from the gist of the present invention.

1 is a side view of an image forming apparatus used in the present invention. It is a figure which shows a present Example. (A) is a top view which shows a carriage and frame periphery. (B) is a figure which shows a carriage guide mechanism. 1 is a side view of an image forming apparatus used in the present embodiment. 3 is a side view showing the relationship between each carriage arm 16 and carriage 8. FIG. It is a top view which shows each positioning hole for position control. The center of the positioning hole 21 formed in the moving mechanism 50 is arranged offset by d in the Y direction with respect to the center G of the rotating member 51, and a worm wheel 51 a is formed on one end surface of the rotating member 51 in the Y direction. It is a figure which shows being done. FIG. 6 is a diagram showing that the distance between the center of the carriage pin 20 and the center of the carriage pin 19 is L, the rotation angle with respect to the center G of the rotating member 51 is θ, and the rotation angle of the belt platen 9 with respect to the carriage pin 20 is φ. It is a figure which shows arrangement | positioning of the reflective evening get 63 adjacent to the positioning holes 21 and 22 arrange | positioned at the both ends of the upstream of the belt platen 9. FIG. It is a figure which shows the calculation process and the calculation of inclination information. (The sum signal of the diagonals of the light receiving surfaces a1 and a2 and b1 and b2 divided in the case of FIG. 8 is taken to obtain the difference signal). The figure assumes that the belt platen 9 is rotated around the Z axis in the direction of the arrow in FIG. is there. FIG. 6 is a diagram showing Example 2. It is the figure which showed arrangement | positioning of the light receiving element by which the light-receiving surface was divided into 4 in parallel with the X-axis and the Y-axis. It is the figure which showed the positional relationship of a Hall element. It is the figure which showed the positional relationship of a Hall element. It is the figure which showed the position of x1 and x2 of the magnetic field distribution by a magnet. FIG. 6 is a diagram showing Example 4. It is the figure which showed that the light radiate | emitted from the light source is projected on a reflective target, and the strong reflected light from a reflection part injects into a light receiving element. It is a figure which shows the position where the light irradiated from the light source passes a hole, and is received with a light receiving element. FIG. 10 is a diagram showing Example 5. It is a figure which shows the example of the sensor position of Example 5. It is a figure which shows the graph when calculating inclination by Example 5. FIG. It is a figure which shows the optical system in the case of switching and measuring an optical path. FIG. 10 is a diagram showing Example 6. FIG. 10 is a diagram showing Example 6. (A) is a case where there is no inclination of the belt platen around the Z-axis with respect to the carriage. (B) is the figure which shortened the protrusion length of one electric cylinder, and lengthened the protrusion of the cylinder from the other cylinder. FIG. 10 is a diagram showing Example 7. FIG. 10 is a diagram showing Example 7. FIG. 10 is a diagram showing Example 8. FIG. 10 is a diagram showing Example 8. FIG. 10 is a diagram showing Example 9. (A) is a case where there is no inclination of the belt platen around the Z-axis with respect to the carriage. (B) shows a case where the belt platen has an inclination around the Z-axis with respect to the carriage, and a case where the color misregistration which does not correct the ejection information inputted to the recording head is uncorrected. (C) shows a case where the belt platen has an inclination around the Z-axis with respect to the carriage, and the color misregistration is corrected by correcting the ejection information inputted to the recording head. It is a figure which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... 1st frame 2 ... 1st frame 3 ... 2nd frame 4 ... 2nd frame 5 ... Connection frame 6 ... Connection frame 7 ... Recording medium 8... Carriage 8a... Projection 8b... Contact surface 8c... Fixed surface 9... Belt platen 9a... Lower end edge 9b ... Lower end edge 10. .... Ink head 11k '... Ink head 11c ... Ink head 11c' ... Ink head 11m ... Ink head 11m '... Ink head 11y ... Ink head 11y' ... Ink head 12 ... belt 13a ... platen roller 13b ... platen roller 13c ... platen roller 14 ... vertical mechanism arm 14a ... Shaft 14b ... Roller 14c ... Roller shaft 15 ... Vertical mechanism arm 15a ... Shaft 15b ... Roller 15c ... Roller shaft 16 ... Carriage arm 17 ... Registration roller shaft 18 ... Roller 19 ... Carriage pin 19a ... Conical part 20 ... Carriage pin 20a ... Conical part 21 ... Positioning hole 22 ... Positioning hole 23a ... Bearing 23b .... Bearing 24 ... Carriage guide mechanism 25 ... Carriage guide mechanism

49... Control unit

51 ... Rotating member 51a ... Worm wheel 51b ... Shaft 52 of rotating member 51 ... Bearing 53 ... Fixed member 54 ... Motor 55 ... Worm gear

60A ... Sensor 60B ... Sensor 61 ... LED
62... Light receiving element 63... Reflection evening get 63 a... Central reflection surface 63 b.

70A ... Sensor 70B ... Sensor 71 ... LED
72... Light receiving element

81: Magnet 82a: Hall element 82b: Hall element 83a: Hall element 83b: Hall element

90A ... Sensor 90B ... Sensor 91 ... LED
92 ... Light receiving element 93a ... Reflective part with high reflectivity 93b ... Low reflective part with low reflectivity 94 ... Hole

100a ... Laser Doppler measuring device 100b ... Laser Doppler measuring device 101 ... Liquid crystal shutter 102 ... Mirror 103 ... Mirror 104 ... Mirror

110 ... Electric cylinder 110a ... Cylinder 111 ... Electric cylinder 111a ... Cylinder 112 ... Moving mechanism 113 ... Base plate 114 ... Pin 115 ... Rib 116 ... Bottom plate 116a .... Positioning hole 117 ... Motor 117a ... Lead screw 118 ... Female screw 120 ... Connection frame 121 ... Connection frame

123 ... Host computer 124k ... Nozzle 124c ... Nozzle 124m ... Nozzle 124y ... Nozzle

231 ... Recording head 232 ... Recording head 233 ... Support member 234 ... Downstream recording head group 235 ... Support member 236 ... Registration mark 237 ... Detection unit 238 ... Calculation 239... Swing member 2310... Shaft 2311... Recording member

Claims (20)

In an image forming apparatus including a recording head having a plurality of nozzle arrays that discharge a plurality of color-specific ink liquids in a first direction with respect to a recording surface of a recording medium to be conveyed,
A transport mechanism for transporting the recording medium in a second direction to create an image on the recording medium;
The nozzle rows are arranged at a predetermined interval and arranged at a position facing the transport mechanism, and information about the relative tilt around the axis perpendicular to the recording surface of the second direction or the transport mechanism and the recording head. An inclination detection unit having a sensor that outputs a signal for generating
An image forming apparatus comprising: a correction unit that performs a calculation based on the signal and corrects a relative inclination between the second direction and the recording head based on a result of the calculation.   The image forming apparatus according to claim 1, wherein the sensor outputs a signal for detecting a relative inclination between the recording head and a belt that conveys the recording medium around the axis.   The image forming apparatus according to claim 1, wherein the sensor outputs a signal for detecting a relative inclination between a belt platen on which a belt for conveying the recording medium is disposed and the recording head around the axis. .   The image forming apparatus according to claim 1, wherein the sensor includes at least a light source and a light receiving element that receives light projected from the light source.   The light projected from the light source is incident on the light receiving element via a target, and the light source and the light receiving element are disposed on one of the recording head or the transport mechanism, and the target is the recording head or the The image forming apparatus according to claim 4, wherein the image forming apparatus is disposed on the other side of the transport mechanism.   The image forming apparatus according to claim 5, wherein the target is disposed throughout the week of the belt.   The image forming apparatus according to claim 1, wherein the sensor includes at least a magnetic member and a magnetic sensor that detects magnetism of the magnetic member.   The image forming apparatus according to claim 1, wherein the sensor is a speed sensor that detects a speed of the recording medium and / or a belt that conveys the recording medium.   The image forming apparatus according to claim 8, wherein the speed sensor is an optical speed sensor.   The speed from two directions is detected in a time division manner by having means for switching and controlling the optical path of the projection light of the optical speed sensor in the optical speed sensor. Image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the inclination detection unit includes two sets of sensors arranged to be spaced apart from each other in a direction perpendicular to the first direction.   The image forming apparatus according to claim 1, wherein the transport mechanism includes a belt platen.   The image forming apparatus according to claim 1, wherein the correction unit includes a tilt mechanism that tilts the transport mechanism around the axis with respect to the recording head.   The image forming apparatus according to claim 1, wherein the correction unit includes a tilt mechanism that tilts the recording head around the axis with respect to the transport mechanism.   The image forming apparatus according to claim 13, wherein the transport mechanism has a positioning portion in a direction perpendicular to the axis with respect to the recording head, and the tilt mechanism tilts relatively with the positioning portion as a center. apparatus.   15. The image forming apparatus according to claim 13, wherein the inclination is controlled by controlling a motor through an engaging portion interlocked with a gear of the motor.   The recording head integrally includes a pin that is a positioning portion perpendicular to the axis with respect to the transport mechanism, and the transport mechanism is inclined relative to the recording head by elastic deformation of the pin. The image forming apparatus according to claim 13, wherein the image forming apparatus is an image forming apparatus.   15. The image forming apparatus according to claim 13, wherein the recording head is provided on a carriage and has an inclination mechanism that is relatively inclined about the axis between the carriage and the transport mechanism.   The correction unit includes a control unit that generates ejection information to be input to the recording head from image information, and the control unit generates ejection information that is shifted by a predetermined amount in the nozzle row direction based on the signal. The image forming apparatus according to claim 1, wherein:   The image forming apparatus according to claim 19, wherein the predetermined amount is calculated from a distance between a reference position and the nozzle row and the signal.

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