WO2015190146A1 - Inkjet recording device - Google Patents

Abstract

An inkjet recording device (100) for forming an image using a full-line head module (121) for discharging ink from a plurality of nozzles (N) and equipped with a plurality of line sensors (141A, 141B) for reading a first test pattern formed by the head module and arranged in a direction (W) which intersects the transport direction (M) of the recording medium (P), wherein the plurality of line sensors are equipped with: a position relationship information acquisition unit (250) for acquiring, for each line sensor, the position relationship in the intersecting direction (W) between the plurality of line sensors and the plurality of nozzles, and positioned in a manner such that the end sections in the intersecting direction (W) in the line sensor detection range overlap; and an analysis unit (144) for referring to the position relationship acquired by the position relationship information acquisition unit, and analyzing the first test pattern reading results for each line sensor.

Description

Inkjet recording device

The present invention relates to an ink jet recording apparatus.

Conventionally, an ink jet recording apparatus that forms an image on a recording medium by applying ink to a recording medium such as paper is known. In such an ink jet recording apparatus, a recording head that has a nozzle array that extends in a direction perpendicular to the conveyance direction of the recording medium (hereinafter referred to as a width direction) and is arranged over a range wider than the width of the recording medium. There is a so-called single-pass type that forms an image by ejecting ink while conveying a recording medium. A single-pass inkjet recording apparatus is highly productive because it can print at high speed.

In such a single-pass inkjet recording apparatus, a predetermined test pattern is formed by ejecting ink from individual nozzles in order to improve nozzle ejection failure and other formation image quality, and downstream of the transport direction. A test pattern is read by a provided line sensor to detect defective nozzles and other image quality.

However, when the reading range is expanded to the full width of the image formation range without changing the size of the line sensor, an optical system for that purpose is required, the size of the reading component is increased and the cost is increased, and the reading resolution is also increased. descend.
For this reason, in the inkjet recording apparatus of Patent Document 1, the surface of the recording medium is read by a single CCD (Charge Coupled Devices) using an optical system, but the back surface of the recording medium is contact type CIS ( Three contact image sensors) were read out side by side along the width direction of the recording medium so as to partially overlap.

JP 2010-114648 A

However, when a plurality of line sensors are arranged side by side in the width direction so as to partially overlap as described above, each photoelectric sensor between the two sensors in the photoelectric conversion element array direction (width direction) and the vertical direction (recording medium conveyance direction). There is a possibility that the test pattern of the overlapped portion may not be properly read due to the influence of the shift between the conversion elements.
In the ink jet recording apparatus of Patent Document 1, a test pattern is not formed on the overlapping portion of the CIS, and the test pattern on the overlapping portion is read by a single CCD on the front side. In other words, the test pattern reading at the overlapping portion of the CIS is practically avoided.

An object of the present invention is to appropriately read a test pattern at an overlapping portion when a plurality of line sensors are arranged side by side so as to cause overlapping.

In order to solve the above problems, the invention described in claim 1
An inkjet recording apparatus that forms an image with a full-line type head module that discharges ink from a plurality of nozzles to a recording medium conveyed in a predetermined conveyance direction,
A plurality of line sensors for reading a first test pattern formed by the head module, arranged along a direction intersecting the conveyance direction of the recording medium,
The plurality of line sensors are arranged such that end portions in a direction intersecting a conveyance direction of the recording medium in the detection range overlap each other,
A positional relationship information acquisition unit that acquires, for each line sensor, a positional relationship in a direction intersecting a conveyance direction of the recording medium between the plurality of line sensors and the plurality of nozzles;
With reference to the positional relationship acquired by the positional relationship information acquisition unit, an analysis unit that analyzes the reading result of the first test pattern for each line sensor,
It is characterized by providing.

According to a second aspect of the present invention, in the ink jet recording apparatus according to the first aspect,
The head module includes a plurality of inkjet heads having a plurality of nozzles arranged along a direction intersecting a conveyance direction of the recording medium,
The plurality of inkjet heads are arranged such that the plurality of nozzles are arranged along a direction intersecting the recording medium conveyance direction, and the nozzles at the ends in the direction intersecting the recording medium conveyance direction are overlapped with each other. It is characterized by being.

The invention according to claim 3 is the ink jet recording apparatus according to claim 2,
The plurality of line sensors and the plurality of inkjet heads are arranged so that the overlapping range of the inkjet heads does not straddle one end or both ends of the overlapping range of the line sensors.

According to a fourth aspect of the present invention, in the ink jet recording apparatus according to any one of the first to third aspects,
In the overlapping range of the line sensors, the analysis unit analyzes a reading result of the first test pattern of only one of the line sensors.

The invention according to claim 5 is the inkjet recording apparatus according to any one of claims 1 to 4,
The positional relationship information acquisition unit is based on the reading result of each line sensor of the second test pattern for detecting the positional relationship and the position of the nozzle used for recording the second test pattern among the plurality of nozzles. The positional relationship is obtained for each line sensor.

The invention according to claim 6 is the ink jet recording apparatus according to any one of claims 1 to 5,
The first test pattern includes a non-discharge detection pattern for detecting non-discharge of each of the plurality of nozzles,
The analysis unit refers to the positional relationship acquired by the positional relationship information acquisition unit, analyzes the reading result of the non-ejection detection pattern for each line sensor, and identifies the position of the non-ejection nozzle. It is characterized by.

According to the present invention, it is possible to appropriately read a test pattern when a plurality of line sensors are arranged side by side so as to cause duplication.

1 is a diagram illustrating a main configuration of an image forming system according to an embodiment of the present invention. It is a bottom view of a head module. It is a bottom view of a reading unit. It is explanatory drawing which shows the positional relationship of an inkjet head and a line sensor. It is a block diagram which shows the control system which concerns on an image forming system. It is explanatory drawing which shows the test pattern which detects a discharge failure nozzle. It is explanatory drawing which shows the positional relationship of each photoelectric conversion element of each line sensor, and the line of a test pattern. It is a figure which shows the detection output of the line of the test pattern by each photoelectric conversion element of each line sensor. It is explanatory drawing which shows the relationship between the detection output of the line of the test pattern by each photoelectric conversion element of each line sensor, and the passage position calculated | required there. It is a block diagram which shows the control system of a reading part.

[Schematic Configuration of Embodiment]
Embodiments of the present invention will be described below with reference to the drawings. However, although various technically preferable limitations for implementing the present invention are given to the embodiments described below, the scope of the invention is not limited to the following embodiments and illustrated examples.

FIG. 1 is a diagram illustrating a main configuration of an image forming system 1 according to an embodiment of the present invention.
The image forming system 1 includes a supply unit 10, a main body unit 100, and a discharge unit 20. The supply unit 10, the main body unit 100, and the discharge unit 20 are provided and connected along a predetermined direction (the X direction shown in FIG. 1).

[Supply section]
The supply unit 10 stores a recording medium P (for example, paper) on which an image is formed by the image forming unit 120 provided in the main body unit 100 and supplies the recording medium P to the main body unit 100 one by one.

[Main part: Overall]
The main body 100 forms an image on the recording medium P supplied from the supply unit 10 and discharges the recording medium P on which the image is formed to the discharge unit 20.

The main body 100 includes a transport unit 110 that transports the recording medium P, an image forming unit 120 that forms an image on the recording medium P, and an irradiation unit 130 that irradiates the recording medium P on which the image is formed by the image forming unit 120 with energy rays. The image forming system 1 includes a reading unit 140 that reads a formed image on a medium conveyed to the conveying unit 110, and functions as an ink jet recording apparatus in the image forming system 1.

[Main unit: Transport unit]
The transport unit 110 transports the medium to the image forming unit 120, the irradiation unit 130, and the reading unit 140.
Specifically, the transport unit 110 includes, for example, a cylindrical drum 110a. The drum 110a is provided so as to be rotatable about an axis passing through the circular center of the cylinder, and carries the recording medium P on the cylindrical outer peripheral surface of the drum 110a. The conveyance unit 110 conveys one surface of the recording medium P carried on the outer peripheral surface while facing the image forming unit 120, the irradiation unit 130, and the reading unit 140 by rotating the drum 110a.
The image forming unit 120, the irradiation unit 130, and the reading unit 140 are provided along the outer peripheral surface in the vicinity of the position where the outer peripheral surface of the rotating drum 110a passes. Specifically, as illustrated in FIG. 1, the image forming unit 120, the irradiation unit 130, and the reading unit 140 are supplied from the supply unit 10 in a conveyance path along which the recording medium P is conveyed by passing through the outer peripheral surface of the drum 110 a. The image forming unit 120, the irradiation unit 130, and the reading unit 140 are provided in this order from the upstream side to the downstream side along the conveyance path for conveying the supplied recording medium P to the discharge unit 20 side.

Further, the transport unit 110 has a detection unit 110b that detects the rotation angle of the drum 110a (see FIG. 5), and is carried on the outer peripheral surface of the drum 110a by the rotation angle of the drum 110a detected by the detection unit 110b. The position of the transported recording medium P is provided so that it can be detected. The detection unit 110b is, for example, an encoder provided on the rotation shaft of the drum 110a. However, the detection unit 110b is an example and is not limited to this, and may be any configuration that can detect the rotation angle of the drum 110a.

Further, the transport unit 110 has a mechanism for inverting the front and back of the recording medium P.
Specifically, the transport unit 110 includes, for example, a switchback unit 115. The switchback unit 115 reverses and conveys the recording medium P by switchback.

More specifically, the switchback unit 115 includes, for example, two cylinders (first cylinder 115a and second cylinder 115b) and a pair of belt loops (belt loop 115c) shown in FIG.
The recording medium P is transferred from the drum 110a to the first cylinder 115a that rotates counterclockwise in FIG. 1 through the cylinder 111 that rotates clockwise in FIG. 1, and then rotates in the clockwise direction in FIG. It is delivered to the two cylinders 115b. When the rear end of the recording medium P reaches the nip portion of the belt loop 115c that rotates counterclockwise in FIG. 1 with the second cylinder 115b, the belt loop 115c reverses in the clockwise direction in FIG. To the drum 110a. Here, the recording medium P returned to the drum 110a by the belt loop 115c is again carried on the drum 110a in a state where the surface on which the image is formed abuts on the outer peripheral surface of the drum 110a. That is, the recording medium P is turned over by the switchback unit 115. Further, the leading end along the conveyance direction of the recording medium P returned to the drum 110a is the end on the trailing side when the recording medium P is conveyed by the drum 110a before being returned. That is, the recording medium P is turned over by being conveyed by the switchback unit 115 so as to be reversed.
As described above, the transport unit 110 can transport the recording medium P such that the both surfaces of the recording medium P are sequentially opposed to the image forming unit 120 by reversing and transporting the recording medium P by the switchback unit 115. It is provided as possible.

The position where the first cylinder 115a of the switchback unit 115 takes over the conveyance of the recording medium P from the drum 110a is downstream of the irradiation unit 130 in the conveyance direction of the recording medium P. Further, when the belt loop 115c returns the recording medium P to the drum 110a, the returned recording medium P is conveyed again to the image forming unit 120 from the upstream side of the image forming unit 120.
Thus, when the image forming unit 120 forms images on both sides of the recording medium P, the switchback unit 115 reverses the front and back of the recording medium P on which the image is formed on one side, It functions as a reversing unit that transports the recording medium P to the upstream side of the image forming unit 120 in the transport direction 110.
The reading unit 140 is provided on the downstream side of the image forming unit 120 in the transport direction and on the upstream side of the switchback unit 115. Therefore, the switchback unit 115 conveys the recording medium P conveyed by the conveyance unit 110 through the image forming unit 120 and the reading unit 140 to the upstream side of the reading unit 140 in the conveyance direction of the conveyance unit 110. Then, it functions as a re-conveying unit that conveys the conveying unit 110 again.

[Main unit: Image forming unit]
The image forming unit 120 forms an image on the recording medium P.
Specifically, the image forming unit 120 includes, for example, a head module 121 provided with a plurality of inkjet heads 122 each having a nozzle for ejecting ink onto a recording medium P carried on the drum 110a. The head module 121 is individually provided for each color of ink ejected onto the recording medium P (for example, four colors of cyan (C), magenta (M), yellow (Y), and black (K)). The image forming unit 120 having the head module 121 forms an image on the recording medium P by ejecting ink.

FIG. 2 is a bottom view showing a surface (bottom surface) facing the recording medium P in the K (black) head module 121. The Y (yellow), M (magenta), and C (cyan) head modules 121 have the same configuration.
Each head module 121 includes a plurality of nozzles N in which openings are arranged facing the conveyance surface of the recording medium P, a drive circuit (not shown), and an ink ejection unit. In the head module 121, the ink ejection unit is operated by the drive voltage output from the drive circuit based on the control signal from the control unit 250, and the ink is ejected by timing control from the openings of the plurality of nozzles N. . An image is formed by landing on the recording medium P on which the ejected ink is conveyed. The head module 121 is a full-line type line head, and nozzles N are arranged so that ink can be ejected over the entire width of the recording medium P where an image can be formed in the width direction perpendicular to the transport direction. . Further, as described above, the head module 121 is provided for each of the four colors Y (yellow), M (magenta), C (cyan), and K (black), but these are all the same structure. FIG. 2 shows only one head module 121.

In the head module 121, a plurality of inkjet heads 122 are arranged in a staggered arrangement in a direction (width direction W) orthogonal to the conveyance direction M of the recording medium P. In each of these inkjet heads 122, a plurality of nozzles N are arranged along the width direction, and some of the nozzles N provided at the end in the width direction W of each inkjet head 122 are other inkjet heads. It arrange | positions so that the overlapping range J which overlaps with the one part nozzle N provided in the edge part in the width direction 122 of 122 may be formed.

[Main unit: Irradiation unit]
The irradiation unit 130 irradiates an energy ray for fixing the image on the recording medium P on which the image is formed by the image forming unit 120.
The energy rays irradiated by the irradiation unit 130 depend on the ink characteristics. For example, when ultraviolet curable ink that is cured by irradiation of ultraviolet rays is used in the head module 121 of the image forming unit 120, the energy rays irradiated from the irradiation unit 130 are ultraviolet rays. In this case, for example, the irradiation unit 130 shields a light source such as a light emitting diode (LED) that emits ultraviolet (UV) light, and a range irradiated with the ultraviolet light emitted from the light source as a predetermined irradiation region. Part. Here, the predetermined irradiation region is a region in a path through which the outer peripheral surface of the drum 110a of the transport unit 110 carries the recording medium P and passes. The irradiation unit 130 irradiates the recording medium P that is transported by the transport unit 110 and passes through a predetermined irradiation region with ultraviolet rays.
When the energy beam is irradiated by the irradiation unit 130, the ink ejected on the recording surface of the recording medium P is cured and fixed on the recording surface. As described above, the irradiation unit 130 functions as a fixing unit that fixes an image on the recording medium P on which the image is formed by the image forming unit 120.

[Main unit: Reading unit]
The reading unit 140 reads a formed image on the medium conveyed to the conveyance unit 110.
Specifically, as shown in FIG. 3, the reading unit 140 is not illustrated with two line sensors 141 </ b> A and 141 </ b> B composed of, for example, CCDs (charge-coupled devices) in which photoelectric conversion elements are arranged along the longitudinal direction. The reflected light from the recording medium P illuminated by the illumination is detected by the two line sensors 141A and 141B, and an electrical signal corresponding to the detection result is output. Based on the electrical signal output from the photoelectric conversion element of the reading unit 140, data corresponding to the reading result is generated and processed as the reading result.
The two line sensors 141A and 141B are arranged in the vicinity of the outer peripheral surface of the drum 110a so that the alignment direction of the photoelectric conversion elements is parallel to the width direction W. The reading unit 140 reads the entire image forming range in the width direction W of each head module 121 described above by the two line sensors 141A and 141B.
These adjacent line sensors 141A and 141B are arranged such that an overlapping range K in which some photoelectric conversion elements provided at the end in the width direction W overlap is formed. Further, in order to arrange in this way, the two adjacent line sensors 141A and 141B are arranged so as to be shifted by a length L in the transport direction M.

Further, in the width direction W, the plurality of line sensors 141A and 141B and the plurality of inkjet heads are arranged so that the overlapping range J of the plurality of inkjet heads 122 does not straddle one end or both ends of the overlapping range K of the line sensors 141A and 141B. 122 are arranged.
That is, the width of the overlapping range J of the inkjet head 122 is smaller than the width of the overlapping range K of the line sensors 141A and 141B, and only one of the overlapping ranges J of the plurality of inkjet heads 122 has a width as shown in FIG. The direction W is inside the overlapping range K of the line sensors 141A and 141B, and all the overlapping ranges J of the other inkjet heads 122 are outside the overlapping range K of the line sensors 141A and 141B.

In the above description, the CCD is exemplified as the line sensors 141A and 141B, but a CIS (Contact Image Sensor) in which photoelectric conversion elements are arranged in the width direction W may be used as the line sensors 141A and 141B.

[Discharge part]
The discharge unit 20 causes the recording medium P to stand by until the recording medium P discharged from the drum 110a of the main body unit 100 via the cylinder 111, the belt loop 112, and the discharge switching guide 113 is collected by the user. The control unit 250 controls whether the recording medium P is discharged to the discharge unit 20 via the cylinder 111 or conveyed to the switchback unit 115.

[Control system]
FIG. 5 is a block diagram illustrating a control system of the image forming system 1.
The image forming system 1 includes, for example, a setting unit 210, an acquisition unit 220, a storage unit 230, a change unit 240, a control unit 250, a display unit 260, and the like in the main body unit 100.

The setting unit 210 includes input devices such as buttons, keys, and a touch panel used for input for various settings related to the operation of the image forming system 1, and corresponds to setting contents corresponding to user operations on the input devices. To the control unit 250.
Specifically, for example, the setting unit 210 outputs a signal for executing image formation by the image forming unit 120 to the control unit 250 in accordance with a user operation.

The acquisition unit 220 acquires data that is the basis of an image formed by the image forming unit 120.
Specifically, the acquisition unit 220 includes a configuration related to communication such as a network interface card (NIC), for example, and a print job transmitted from an external device such as a PC connected via the communication. To get. The print job includes image data corresponding to the image formed by the image forming unit 120.

The storage unit 230 stores the image data of the first and second test patterns and the positional relationship between the plurality of line sensors 141A and 141B and the plurality of nozzles N in the direction (width direction W) intersecting the recording medium conveyance direction. Data memory.
As the first test pattern, for example, there is a non-ejection detection pattern for detecting ejection failure nozzles in each head module 121.
Further, as the second test pattern, there is a test pattern for obtaining a positional deviation in the width direction in the two line sensors 141A and 141B described above.

The changing unit 240 changes a condition relating to image formation by the image forming unit 120 based on the reading result by the reading unit 140.
Specifically, the changing unit 240 includes, for example, an integrated circuit such as a PLD or an ASIC, or a combination thereof, and the conditions related to image formation are determined by the cooperation of the processing unit and the storage device mounted on the circuit. Processing is performed. Alternatively, a CPU that executes predetermined software may be configured to realize the function as the changing unit 240.
For example, when a discharge failure of any nozzle of the inkjet head 122 provided in the head module 121 is detected based on the reading result of the first test pattern for detecting a discharge failure nozzle by the reading unit 140, Of the conditions relating to image formation, the condition relating to ink ejection from the nozzles is changed to a condition that considers that ink ejection from defective ejection nozzles is not performed.
In other words, the changing unit 240 makes a change such as increasing the printing rate (dot appearance rate) of the nozzle N adjacent to the defective nozzle N to compensate for the defective portion due to the defective discharge. Thereby, it is possible to reduce the influence of the defective nozzle N on the image quality.

The control unit 250 controls the operation of each unit of the image forming system 1.
Specifically, the control unit 250 includes, for example, a CPU, a RAM, a ROM, and the like.
The CPU reads and executes various programs, data, and the like corresponding to the processing contents from a storage device such as a ROM, and controls the operation of each unit of the image forming system 1 according to the executed processing contents. The RAM temporarily stores various programs and data processed by the CPU. The ROM stores various programs and data read by the CPU or the like.

The display unit 260 performs various displays related to the operation of the image forming system 1 under the control of the control unit 250.
Specifically, the display unit 260 includes, for example, a display device such as a liquid crystal display provided integrally with an input device for performing input in a touch panel format, and performs various displays using the display device. The liquid crystal display is merely an example of a display device, and may be another display device (for example, an organic EL (Electroluminescence) display).

[Calculation of misalignment of line sensor in width direction]
Here, the control system of the reading unit 140 will be described in detail.
First, as a premise, a first test pattern for detecting an ejection failure nozzle in each head module 121 that is read by the line sensors 141A and 141B of the reading unit 140 will be exemplified.
As shown in FIG. 6, the first test pattern for detecting defective ejection nozzles is composed of lines having a predetermined length in the transport direction M individually ejected from all nozzles N of all inkjet heads 122. Yes.

It is assumed that the dot pitch in the width direction W of the head module 121 is narrower than the pitch of the photoelectric conversion elements of the line sensors 141A and 141B, and the head module 121 has a higher resolution.
For this reason, each nozzle N forms a line by shifting the position in the transport direction M in units of four (which may be two or more depending on the sensor resolution, but is not limited to four). Thereby, each line of the first test pattern can be formed at a pitch four times the dot pitch in the width direction W, and good reading can be performed by the line sensors 141A and 141B with low resolution.
For example, when the No. 10 nozzle N is defective in ejection, the corresponding line is not formed or becomes unclear as shown in FIG. As a result, the line sensors 141A and 141B do not read the line at the position where it should be, and the nozzle N with defective ejection is specified by the undetected line.

Since the first test pattern is read in this manner, the line sensor 141A and the line sensor 141B are displaced in the width direction W, and the photoelectric conversion element of the line sensor 141A and the photoelectric conversion element of the line sensor 141B When the relative positional relationship in the width direction W with the nozzle N of the inkjet head 122, which will be described later, is not grasped, each line sensor 141A, 141B has a photoelectric conversion element that should originally detect the line. There is a possibility that a photoelectric conversion element next to the line detects a line, which may cause a false detection.

Therefore, a second test pattern for detecting the relative positional relationship in the width direction W between some of the nozzles of the inkjet head 122 and the photoelectric conversion elements of the line sensors 141A and 141B at an initial stage such as before shipment. Is detected, and the amount of displacement (positional displacement) in the width direction W of the line sensors 141A and 141B is detected. The “partial nozzles N of the inkjet head 122” indicate a plurality of nozzles N that form the second test pattern.
In order to detect misalignment of the line sensors 141A and 141B, the second test pattern is arranged in the transport direction M in an arrangement passing through the overlapping range K of the line sensors 141A and 141B in the width direction W as shown in FIG. It is comprised from the 1 or several line formed along. When the second test pattern is composed of a plurality of lines, it is desirable that each line be formed at a uniform interval in the width direction W. Further, although the number of lines is sufficient, the more accurate displacement can be obtained as the number of lines increases. Here, the case where there are three lines L1 to L3 is illustrated for ease of explanation, but in reality, the width of the overlapping range K of the line sensors 141A and 141B is wide and the number of lines is more than three. There are many. Further, the number of photoelectric conversion elements included in the overlapping range K is larger than that in the illustrated example of FIG. Further, the ratio of the width of each line L1 to L3 and the width of each photoelectric conversion element is not limited to the example of FIG. 7, and can be changed according to the resolution of the line sensor.

As shown in FIG. 7, it is assumed that the line sensor 141 </ b> A and the line sensor 141 </ b> B are displaced by a displacement amount S in the width direction W.
The outputs of the photoelectric conversion elements A to H of the line sensor 141A and the photoelectric conversion elements a to h of the line sensor 141B in the overlapping range K are shown in FIG.
In FIG. 7, the outer rectangles lined up in the width direction W are the cell lines of the line sensor, and the slightly smaller rectangles inside are the photoelectric conversion elements. Then, the detection outputs read by the photoelectric conversion elements A to H and a to h are converted into% display and shown in FIG. In FIG. 8, the output when one line is detected by one photoelectric conversion element is normalized as 100%, and the output when no line is detected is normalized as 0%.
It is ideal that the photoelectric conversion elements A to H of the line sensor 141A and the photoelectric conversion elements a to h of the line sensor 141B have the same arrangement in the width direction W. However, as described above, they are actually shifted by the shift amount S. Yes. In this case, as shown in FIG. 8, the line L1 is detected at 80% and 20% output by the photoelectric conversion elements B and C of the line sensor 141A, and 40% by the photoelectric conversion elements a and b of the line sensor 141B. Detected at 60% output.
The line L2 is detected with 40% and 60% output by the photoelectric conversion elements D and E of the line sensor 141A, and is detected with 100% output by the photoelectric conversion element d of the line sensor 141B.
The line L3 is detected with 90% and 10% output by the photoelectric conversion elements G and H of the line sensor 141A, and detected with 40% and 60% output by the photoelectric conversion elements f and g of the line sensor 141B. Yes.

As described above, when all the lines L1 to L3 are detected by one photoelectric conversion element, that is, when the line passes through the center of the photoelectric conversion element, the output of the photoelectric conversion element is 100%. Thus, the output decreases as the line moves away from the center of the photoelectric conversion element. Thereby, the relative positional relationship between the line and the photoelectric conversion element is determined. For example, the line L1 detected by the photoelectric conversion elements a and b of the line sensor 141B has an output of 40% and 60%, so the line L1 is between the center of the photoelectric conversion element a and the center of the photoelectric conversion element b. It can be specified that the vehicle passes through a position with a ratio of 6: 4.

Based on the above principle, FIG. 9 shows the relationship between the detection outputs of the lines L1 to L3 by the photoelectric conversion elements A to H of the line sensor 141A and the photoelectric conversion elements a to h of the line sensor 141B and the passing positions obtained therefrom. .
The horizontal axes 1 to 8 in FIG. 9 indicate the center positions of the photoelectric conversion elements A to H of the line sensor 141A or the photoelectric conversion elements a to h of the line sensor 141B in the width direction W, and the vertical axis represents the photoelectric conversion elements. The detection output is shown.
LA1 to LA3 indicate detection positions of the lines L1 to L3 obtained from the detection of the line sensor 141A, and la1 to la3 indicate detection positions of the lines L1 to L3 obtained from the detection of the line sensor 141B.

For example, since the line L1 is detected at 80% and 20% by the photoelectric conversion elements B and C of the line sensor 141A, a ratio of 2: 8 is provided between the center of the photoelectric conversion element B and the center of the photoelectric conversion element C. Passing through position [2.2]. Moreover, since the line L1 is detected at 40% and 60% by the photoelectric conversion elements a and b of the line sensor 141B, a ratio of 6: 4 is provided between the center of the photoelectric conversion element a and the center of the photoelectric conversion element b. It passes the position [1.6]. Since these difference values are 0.6, the amount of deviation in the width direction W between the line sensor 141A and the line sensor 141B is required to be 0.6 times the photoelectric conversion element pitch.
Further, since the line L2 is detected at 40% and 60% by the photoelectric conversion elements D and E of the line sensor 141A, a ratio of 6: 4 between the center of the photoelectric conversion element D and the center of the photoelectric conversion element E is obtained. It passes the position [4.6]. Further, since the line L2 is detected at 100% by the photoelectric conversion element d of the line sensor 141B, the line L2 passes through the position [4.0] which is the center of the photoelectric conversion element d. Since these difference values are 0.6, the amount of deviation in the width direction W between the line sensor 141A and the line sensor 141B is required to be 0.6 times the photoelectric conversion element pitch.
Further, since the line L3 is detected by 90% and 10% by the photoelectric conversion elements G and H of the line sensor 141A, a ratio of 1: 9 is provided between the center of the photoelectric conversion element G and the center of the photoelectric conversion element H. It passes through position [7.1]. Further, since the line L3 is detected at 40% and 60% by the photoelectric conversion elements f and g of the line sensor 141B, a ratio of 6: 4 is provided between the center of the photoelectric conversion element f and the center of the photoelectric conversion element g. It passes through the position [6.6]. Since these difference values are 0.5, it is required that the amount of deviation in the width direction W between the line sensor 141A and the line sensor 141B is 0.5 times the photoelectric conversion element pitch.
Note that the deviation in the width direction W between the line sensor 141A and the line sensor 141B obtained for each of the lines L1 to L3 in accordance with the resolution of the line sensors 141A and 141B varies, and thus the deviation in the width direction W. It is desirable to average. As described above, since the actual number of lines is more than three, more shift amounts in the width direction W can be acquired, and the line sensor 141A and the line can be obtained by obtaining an average value of the larger shift amounts. The shift amount in the width direction W of the sensor 141B can be obtained with higher accuracy.

By obtaining the amount of shift in the width direction W of the line sensor 141A and the line sensor 141B, the relative positional relationship in the width direction W of the photoelectric conversion element included in the line sensor 141A and the photoelectric conversion element included in the line sensor 141B is acquired. The
Furthermore, since the second test pattern is read by the two line sensors 141A and 141B, the three nozzles N of the inkjet head 122 and the line sensor 141A that have formed the second test pattern, the photoelectric conversion elements and the line sensor 141B. The relative positional relationship in the width direction W of the photoelectric conversion element included in is acquired.
That is, the control unit 250 reads “the position of the nozzle N used for recording the second test pattern among the plurality of nozzles N and the reading results of the line sensors 141A and 141B of the second test pattern for detecting the positional relationship”. Based on the above, it functions as a “positional relationship information acquisition unit that obtains a positional relationship for each line sensor”.

In principle, all the nozzles of all the ink jet heads 122 are arranged at a prescribed nozzle pitch, so that the relative positional relationship in the width direction W of all the nozzles N can be acquired from some of the nozzles N.
Therefore, from these, the relative positional relationship in the width direction W of all the nozzles N of all the inkjet heads 122, the photoelectric conversion elements included in the line sensor 141A, and the photoelectric conversion elements included in the line sensor 141B (“total positional relationship”). ”).

By acquiring the comprehensive positional relationship, the correspondence relationship in the width direction W between the photoelectric conversion element of the line sensor 141A and the plurality of nozzles N corresponding to the line sensor 141A can be obtained. That is, it is grasped by which photoelectric conversion element of the line sensor 141A the dot or line formed by each nozzle N is read, and at which position in the width direction W of which photoelectric conversion element is read. be able to.
The same applies to the line sensor 141B, and the correspondence relationship in the width direction W between the photoelectric conversion element of the line sensor 141B and the plurality of nozzles N corresponding to the line sensor 141B can be obtained. That is, it is grasped by which photoelectric conversion element of the line sensor 141B the dot or line formed by each nozzle N is read, and at which position in the width direction W of which photoelectric conversion element is read. be able to.

The control unit 250 obtains the comprehensive positional relationship by executing the positional relationship information acquisition program and stores it in the storage unit 230.
That is, the control unit 250 obtains “a positional relationship in which each of the line sensors 141A and 141B and the plurality of nozzles N acquires the positional relationship in the direction (width direction W) intersecting the recording medium conveyance direction for each line sensor. It will function as an “information acquisition unit”.

[Scanner control system]
FIG. 10 shows a control system of the reading unit 140.
That is, the reading unit 140 includes two line sensors 141A and 141B, data storage units 142A and 142B that store detection data for one line of each of the line sensors 141A and 141B as digital data by A / D conversion, and line Refer to the inter-sensor gap correction unit 143 that adjusts the deviation of the detection timing according to the length L (see FIG. 3) of the positional deviation of the sensors 141A and 141B in the transport direction M, and the comprehensive positional relationship stored in the storage unit 230. An analysis unit 144 that analyzes the read result of the first test pattern is provided for each line sensor.
From detection by the two line sensors 141A and 141B to storage of data is executed in parallel processing.

The above-described first test pattern (see FIG. 6) is read to each of the line sensors 141A and 141B, and a detection signal corresponding to the output of the photoelectric conversion element that detects each line is output.
The data storage units 142A and 142B convert the detection signals from the line sensors 141A and 141B into digital data by A / D conversion and store them.

The inter-sensor gap correction unit 143 divides the length L by the conveyance speed of the recording medium P because the line sensor 141B is positioned upstream of the line sensor 141A by the length L in the conveyance direction. In 141A and 141B, a timing difference for reading the same pattern is calculated. Then, the detection data of the line sensor 141 </ b> B is input to the analysis unit 144 after being delayed by the calculated timing difference. Alternatively, the detection unit 110b provided in the drum 110a detects that the drum 110a has been fed by the length L, and then inputs the detection data of the line sensor 141B to the analysis unit 144.

For each line sensor 141A, 141B, the analysis unit 144 detects, based on the detection data based on the reading result of the first test pattern, each line of the first test pattern at any position in the width direction W of any photoelectric conversion element. It is determined whether or not a line has been detected, a line that has not been detected due to nozzle non-ejection is detected by referring to the data on the overall positional relationship stored in the storage unit 230, and which nozzle is the line. Identify.

That is,
(1) From the detection data of the detection range (including the overlapping range K) by the line sensor 141A, referring to the comprehensive positional relationship data, it is not detected in a plurality of lines scheduled to pass the detection range. A line is specified, and the nozzle N corresponding to the line is specified.
(2) From the detection data of the range obtained by removing the overlapping range K from the detection range by the line sensor 141B, with reference to the comprehensive positional relationship data, detection is made among a plurality of lines scheduled to pass the detection range. A line that is not to be processed is specified, and a nozzle N corresponding to the line is specified.

The changing unit 240 described above has a printing rate of the surrounding nozzles for correcting the nozzle missing due to the ejection failure of the nozzles from the ejection failure nozzles identified by the analysis unit 144 based on the above (1) and (2). The increase / decrease value of the dot appearance rate is determined.

[Technical effects of the embodiment]
In the main body 100 of the image forming system 1, the reading unit 140 includes two line sensors 141 </ b> A and 141 </ b> B in an overlapping arrangement in the width direction W, and the width direction of the plurality of line sensors 141 </ b> A and 141 </ b> B and the plurality of nozzles N is provided. The positional relationship of W is acquired for each line sensor 141A, 141B and held in the storage unit 230, and the reading result of the first test pattern is analyzed for each line sensor 141A, 141B with reference to this positional relationship. 144 is analyzing.
That is, the relative positional relationship in the width direction W between one line sensor 141A and the nozzle N corresponding to the sensor is acquired, and the width direction between the other line sensor 141B and the nozzle N corresponding to the sensor is acquired. Since the relative positional relationship of W is also acquired, the detection of the non-ejection nozzle by reading the first test pattern in the overlapping portion of the line sensors 141A and 141B is the positional relationship of either the line sensor 141A or 141B. Therefore, it is possible to appropriately read the first test pattern in the overlapping portion.
Further, since it is not necessary to synthesize the sensor outputs of the two line sensors 141A and 141B for the overlapping parts of the line sensors 141A and 141B, it is possible to reduce the processing load and speed up the processing.

Each head module 121 of the main body 100 of the image forming system 1 includes a plurality of ink jet heads 122 having a plurality of nozzles N arranged along the width direction W of the recording medium P. The nozzles at the ends in the direction W are arranged so as to overlap each other.
This eliminates the need for an inkjet head having a large and enormous number of nozzles equal to the entire width of the image forming range, and allows the use of a narrow inkjet head that is easy to manufacture and easy to maintain and replace, and that can improve productivity and maintainability. Can be realized.

Furthermore, each line sensor 141A, 141B and each inkjet head 122 are arrange | positioned so that the overlapping range J of each inkjet head 122 may not straddle the one end or both ends of the overlapping range K of line sensor 141A, 141B ( (See FIG. 4).
For this reason, it can avoid that a sensor joint is arrange | positioned in the overlapping range J of the inkjet head 122, the influence with respect to the image quality which arises in the joint part of the line sensor in the overlapping range J of the inkjet head 122 is reduced, and acquisition nozzle position It is possible to reduce the influence of errors.

Further, the analysis unit 144 analyzes the reading result of the first test pattern of one line sensor 141A in the overlapping range K of the line sensors 141A and 141B. Therefore, it is possible to reduce the overlapping processing in the overlapping range K, further reduce the processing load, and speed up the processing.
Note that the processing of the overlapping range K is performed based on the detection data of the line sensor 141A, but may be performed based on the detection data of the line sensor 141B.

The control unit 250 functioning as a positional relationship information acquisition unit was used to record the reading results of the line sensors 141A and 141B of the second test pattern for detecting the positional relationship and the second test pattern among the plurality of nozzles N. Based on the position of the nozzle N, the positional relationship between the line sensor 141A and the nozzle N corresponding to the line sensor 141A and the positional relationship between the line sensor 141B and the nozzle N corresponding to the line sensor 141B are shown in the line sensors 141A and 141B. Asking for every one.
Thereby, without reading the first test pattern (for example, see FIG. 6) formed by all the nozzles N, the positional relationship between the line sensor 141A and the nozzle N corresponding to the line sensor 141A, and the line sensor 141B The positional relationship with the nozzle N corresponding to the line sensor 141B can be acquired, the reading of the first test pattern formed by all the nozzles N and the processing associated therewith are not required, and the processing load is further reduced and the processing is reduced. It is possible to speed up.

The first test pattern includes a non-discharge detection pattern for detecting non-discharge of each of the plurality of nozzles N, and the analysis unit 144 is a position acquired by the control unit 250 as a positional relationship information acquisition unit. With reference to the relationship, the reading result of the non-ejection detection pattern is analyzed for each of the line sensors 141A and 141B, and the position of the non-ejection nozzle is specified.
For this reason, it is possible to properly detect the non-ejection nozzles while reducing the processing load.

[Others]
In the image forming system 1, the case where the main body unit 100 includes the two line sensors 141 </ b> A and 141 </ b> B is illustrated, but the number of individuals may be larger.
For example, when there are three line sensors, the line that passes through the overlap area of the first line sensor and the second line sensor from one end in the width direction, the overlap of the second line sensor and the third line sensor The first line sensor and the second line according to a second test pattern having a line passing through the region and known by accurately measuring or detecting the position in the width direction W of these lines. A first positional deviation in the width direction of the sensor is obtained, and further, a second positional deviation in the width direction of the second line sensor and the third line sensor is obtained.
For example, when the first line sensor is used as a reference, the positional relationship in the width direction W is obtained based on the first positional deviation for the second line sensor, and the first line sensor is used for the first line sensor. The positional relationship in the width direction between the first line sensor and the third line sensor is obtained based on the added value of the positional deviation and the second positional deviation.
By these, it is possible to acquire the positional relationships in the width direction of all of the first to third line sensors.

In addition, although the case where the plurality of inkjet heads 122 of the head module 121 are arranged in a staggered arrangement in the direction orthogonal to the transport direction (width direction W) is illustrated, the present invention is not limited to this, and obliquely intersects the transport direction. They may be arranged in a staggered arrangement in the direction. Similarly, the plurality of nozzles N of each inkjet head 122 are not limited to the direction (width direction W) orthogonal to the transport direction, but may be provided along a direction obliquely intersecting the transport direction.
In these cases, there is a difference in the arrangement in the transport direction for each inkjet head or each nozzle, but when each inkjet head is arranged along the width direction W by appropriately controlling the ejection timing of each nozzle, An image can be formed in the same manner as when the nozzles are arranged along the width direction W.

Moreover, although the case where the arrangement direction of the line sensors 141A and 141B and the arrangement direction of the plurality of photoelectric conversion elements of the line sensors 141A and 141B are parallel to the direction orthogonal to the transport direction (width direction W) is illustrated, Not limited to this, it may be parallel to a direction that obliquely intersects the transport direction. In that case, since a difference occurs in the detection timing of each photoelectric conversion element, detection is performed in the same manner as when each photoelectric conversion element is arranged along the width direction W by appropriately controlling the detection timing for each element. It is possible.

In the second test pattern, the positional deviation between the sensors in the width direction W is obtained by a common line passing through the overlapping range of the line sensors 141A and 141B, but passes through the detection range other than the overlapping range of the line sensor 141A. It is also possible to obtain the positional deviation between the sensors in the width direction W by using a second test pattern including a line to be detected and a line that passes through a detection range other than the overlapping range of the line sensor 141B.
In this case, it is assumed that the distance in the width direction W between the line on the line sensor 141A side and the line on the line sensor 141B side is known by being accurately measured or detected.

In addition, the first test pattern may be a test pattern for detecting the displacement of the landing position in the width direction W of the formed dots of all the nozzles of the head module 121.
As the first test pattern, the same test pattern as that for detecting a non-ejection nozzle shown in FIG. 6 can be used.
That is, the first test pattern is read by each line sensor 141A, 141B, and the first test pattern is read from the above-described comprehensive positional relationship data stored in the storage unit 230 for each line sensor 141A, 141B. The position in the width direction W of the dot (line) formed by each nozzle obtained from the result is compared with the position of the corresponding nozzle determined in the overall positional relationship, and the difference is obtained as the positional deviation of the landing position.
Also in this case, regarding the overlapping range of the line sensors 141A and 141B, the positional deviation of the landing position may be obtained from the reading result of either one of the line sensors 141A or 141B.

When the first test pattern is a test pattern for detecting the displacement of the landing positions in the width direction W of the formation dots of all the nozzles of the head module 121, the changing unit 240 detects the displacement of the formation dots. Based on the result of reading the test pattern, adjustment of the printing rate (dot appearance rate) of the nozzle N in which the positional deviation has occurred and the surrounding nozzles N is executed.
That is, the change unit 240, when the density of the dots of the nozzle N that has caused the positional deviation has occurred, changes the printing rate (dot appearance rate) of the nozzle N that is adjacent to the nozzle N that has caused the positional deviation due to the balance with the surrounding dots. ) Can be adjusted so that the contrast becomes inconspicuous.

In the above-described embodiment, the positional relationship (total positional relationship) in the width direction W between the photoelectric conversion element of the line sensor 141A, the photoelectric conversion element of the line sensor 141B, and all the nozzles of all the inkjet heads 122 is acquired. The case where the above-mentioned comprehensive positional relationship is referred to when analyzing the reading results of the first test patterns of the sensor 141A and the line sensor 141B is illustrated.
However, by reading the test pattern formed by all the nozzles as in the first test pattern of FIG. 6 by the line sensor 141A, each photoelectric conversion element of the line sensor 141A and a plurality of nozzles within the reading range of the line sensor 141A. 6 in the width direction W. Similarly, the photoelectric conversion elements of the line sensor 141B are read by reading the test patterns formed by all the nozzles as in the first test pattern of FIG. 6 by the line sensor 141B. And the positional relationship in the width direction W with a plurality of nozzles within the reading range of the line sensor 141A may be acquired. That is, the positional relationship with each nozzle is acquired by each of the line sensors 141A and 141B, and in the analysis by the analysis unit 144, the positional relationship corresponding to each of the line sensors 141A and 141B is referred to, and no ejection is performed. The nozzle may be specified.

There is a possibility of being used in the field of an ink jet recording apparatus in which a plurality of line sensors that read a test pattern are arranged in an overlapping manner.

1 Image Forming System 100 Main Body (Inkjet Recording Device)
DESCRIPTION OF SYMBOLS 120 Image formation part 121 Head module 122 Inkjet head 140 Reading part 141A, 141B Line sensor 142A, 142B Data storage part 143 Intersensor gap correction part 144 Analysis part 230 Storage part 240 Change part 250 Control part (Position relation information acquisition part)
J Overlapping range K Overlapping range L1 to L3 Line M Conveying direction N Nozzle P Recording medium S Deviation amount W Width direction (direction orthogonal to the conveying direction)

Claims (6)

1. An inkjet recording apparatus that forms an image with a full-line type head module that discharges ink from a plurality of nozzles to a recording medium conveyed in a predetermined conveyance direction,
   A plurality of line sensors for reading a first test pattern formed by the head module, arranged along a direction intersecting the conveyance direction of the recording medium,
   The plurality of line sensors are arranged such that end portions in a direction intersecting a conveyance direction of the recording medium in the detection range overlap each other,
   A positional relationship information acquisition unit that acquires, for each line sensor, a positional relationship in a direction intersecting a conveyance direction of the recording medium between the plurality of line sensors and the plurality of nozzles;
   With reference to the positional relationship acquired by the positional relationship information acquisition unit, an analysis unit that analyzes the reading result of the first test pattern for each line sensor,
   An ink jet recording apparatus comprising:
2. The head module includes a plurality of inkjet heads having a plurality of nozzles arranged along a direction intersecting a conveyance direction of the recording medium,
   The plurality of inkjet heads are arranged such that the plurality of nozzles are arranged along a direction intersecting the recording medium conveyance direction, and the nozzles at the ends in the direction intersecting the recording medium conveyance direction are overlapped with each other. The ink jet recording apparatus according to claim 1, wherein the ink jet recording apparatus is provided.
3. The plurality of line sensors and the plurality of inkjet heads are arranged so that an overlapping range of the inkjet heads does not straddle one end or both ends of the overlapping range of the line sensors. The ink jet recording apparatus described.
4. 4. The analysis unit according to claim 1, wherein the analysis unit analyzes a reading result of the first test pattern of only one of the line sensors in an overlapping range of the line sensors. 5. The ink jet recording apparatus described.
5. The positional relationship information acquisition unit is based on the reading result of each line sensor of the second test pattern for detecting the positional relationship and the position of the nozzle used for recording the second test pattern among the plurality of nozzles. The ink jet recording apparatus according to claim 1, wherein the positional relationship is obtained for each line sensor.
6. The first test pattern includes a non-discharge detection pattern for detecting non-discharge of each of the plurality of nozzles,
   The analysis unit refers to the positional relationship acquired by the positional relationship information acquisition unit, analyzes the reading result of the non-ejection detection pattern for each line sensor, and identifies the position of the non-ejection nozzle. The ink jet recording apparatus according to claim 1, wherein:

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