JP6992643B2 - Inkjet printer - Google Patents

Description

The present invention relates to an inkjet printer.

Conventionally, in an image forming apparatus such as a printer, a copying machine, a facsimile, or a multifunction device, for example, in an inkjet printer, a carriage is moved along a rail in a main scanning direction, and ink is discharged from a plurality of recording heads mounted on the carriage. By being ejected and attached to a recording medium, an image such as a character or an image composed of a collection of dots is formed and printed.

By the way, in a serial type inkjet printer, the carriage is reciprocated to form an image, but the position where the ink ejected from the recording head adheres to the recording medium to form dots ( If the "dot position") is different between the outward path and the return path of the carriage, the image will be misaligned and the image quality will be deteriorated.

Therefore, a pattern image for position adjustment is formed on a recording medium, the image density of the pattern image for position adjustment is detected by an optical sensor, and a correction value for correcting the dot position is calculated based on the image density. (See, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2016-182679

However, in the conventional inkjet printer, there is no target value of the image density for calculating the correction value, and the correction value is calculated based only on the detected image density. The number of times the pattern image for adjustment is formed on the recording medium and the image density of the pattern image is detected increases, the work for correcting the dot position is troublesome, and the time required to correct the dot position is long. It will be long.

The present invention can solve the problems of the conventional inkjet printer, simplify the work for correcting the dot position, and shorten the time required to correct the dot position. The purpose is to provide a printer.

Therefore, in the inkjet printer of the present invention, the carriage is movably arranged in the main scanning direction, a plurality of recording heads mounted on the carriage, and a drive unit for moving the carriage are driven to reciprocate the carriage. A carriage drive processing unit for moving, a transport processing unit for driving a transport drive unit to transport the recording medium in the sub-scanning direction, and a transport processing unit for driving each recording head to the recording medium on the outward path of the reciprocating movement of the carriage. A head drive processing unit that forms a test pattern image consisting of a reference pattern image formed only by the image and a plurality of adjustment pattern images formed on the outward and return paths, and a dot and image density of the test pattern image by an image density detection unit. An image detection processing unit that detects and calculates a correction value for correcting the dot position based on the dots and image densities of the reference pattern image and the dots and image densities of the plurality of adjustment pattern images, and the image detection. It has a head drive condition setting unit that sets a correction value calculated by the processing unit as a drive condition of the recording head.

According to the present invention, in an inkjet printer, a carriage movably arranged in the main scanning direction, a plurality of recording heads mounted on the carriage, and a drive unit for moving the carriage are driven to reciprocate the carriage. A carriage drive processing unit for moving, a transport processing unit for driving a transport drive unit to transport the recording medium in the sub-scanning direction, and a transport processing unit for driving each recording head to the recording medium on the outward path of the reciprocating movement of the carriage. A head drive processing unit that forms a test pattern image consisting of a reference pattern image formed only by the image and a plurality of adjustment pattern images formed on the outward and return paths, and a dot and image density of the test pattern image by an image density detection unit. An image detection processing unit that detects and calculates a correction value for correcting the dot position based on the dots and image densities of the reference pattern image and the dots and image densities of the plurality of adjustment pattern images, and the image detection. It has a head drive condition setting unit that sets a correction value calculated by the processing unit as a drive condition of the recording head.

In this case, the image density of the reference pattern image is set as the target value based on the adjustment pattern image, and the dot position is corrected for the amount of dot shift of the pattern image in which the image density equal to the image density of the reference pattern image is obtained. It can be a correction value.

Therefore, since the number of times the test pattern image is formed on the recording medium and the image density is detected can be reduced, the work for correcting the dot position can be simplified and the dot position can be corrected. The time required for this can be shortened.

It is a control block diagram of the inkjet printer in embodiment of this invention. It is a perspective view of the inkjet printer in embodiment of this invention. It is a conceptual diagram which shows the main part of the inkjet printer in embodiment of this invention. It is a figure which shows the example of the basic pattern image in embodiment of this invention. It is a figure which shows the example of the test pattern image in embodiment of this invention. It is an enlarged view of the pattern image in embodiment of this invention. It is a flowchart which shows the operation of the inkjet printer at the time of correcting the dot position in embodiment of this invention. It is a figure which shows the distribution of the image density | concentration of the pattern image in embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this case, an inkjet printer as an image forming apparatus will be described.

FIG. 2 is a perspective view of the inkjet printer according to the embodiment of the present invention, and FIG. 3 is a conceptual diagram showing a main part of the inkjet printer according to the embodiment of the present invention.

In the figure, 10 is a serial inkjet printer, Fr is a frame supporting the main body of the inkjet printer 10, that is, the main body of the device, and the frame Fr is the frame Fr when the inkjet printer 10 is viewed from the front side (front side in FIG. 2). A receiving plate BP extending from the left end to the right end of the case, and as a first support portion formed by rising from the receiving plate BP to the right by a predetermined distance from the left end of the receiving plate BP. The frame body PL and the frame body PR as a second support portion formed by rising from the receiving plate BP on the left side by a predetermined distance from the right end of the receiving plate BP are provided.

A rail 15 extends linearly between both ends of the receiving plate BP, and the carriage 17 is arranged (erected) along the rail 15 in the left-right direction, that is, in the main scanning direction (arrows a and b). It is arranged so as to be movable. On the carriage 17, a plurality of recording heads Hdi (i = 1, 2, ..., 4) in the present embodiment have a surface on which a plurality of nozzles (not shown) open, that is, a nozzle surface downward. It will be installed toward. In the present embodiment, black, yellow, magenta, and cyan inks are ejected from the nozzles of each recording head Hdi, and each ink forms a color image on the recording medium P.

Further, the drive-side pulley 18 is rotatably arranged near the left end of the rail 15, and the driven-side pulley 19 is rotatably arranged near the right end of the rail 15, and the endless belt 21 is freely travelable between the pulleys 18 and 19. The carriage 17 is stretched and attached to a predetermined position on the endless belt 21. Then, a carriage motor 22 as a drive unit for moving the carriage is connected to the pulley 18.

Therefore, by driving the carriage motor 22 and traveling the endless belt 21, the carriage 17 can be moved in the main scanning direction, and each recording head Hdi can be moved in the main scanning direction. At this time, ink of each color is ejected from each nozzle of the recording head Hdi and attached to the recording medium P conveyed in a direction orthogonal to the moving direction of the carriage 17, that is, in the sub-scanning direction (arrow c direction). As a result, images such as characters and images are formed on the recording medium P, and printing is performed. As the recording medium P, a resin film such as vinyl chloride or PET can be used in addition to the paper.

Further, a sensor unit 23 is attached to the right side (home position side) of the carriage 17, and a reflection type optical sensor 24 as a pixel detection unit and an image density detection unit is arranged in the sensor unit 23. .. The optical sensor 24 has an R detection unit 45 (FIG. 1) as a first color detection unit, a G detection unit 46 as a second color detection unit, and a B detection unit as a third color detection unit, which will be described later. The R detection unit 45 provides an image density of a cyan color image, a G detection unit 46 provides an image density of a magenta color image, and a B detection unit 47 provides an image density of a yellow color image and a black color image. Detect image density.

A linear scale (not shown) extending along the rail 15 and extending parallel to the rail 15 is linearly arranged, and the scale of the linear scale is provided by an encoder 35 described later provided on the carriage 17. It is optically read and the position of the carriage 17 is detected based on the sensor output of the encoder 35. Then, the moving speed of the carriage 17 can be calculated based on the change in the position of the carriage 17 and the time.

Further, a metal platen 25 having a plate-like shape is arranged along the rail 15 and extending in parallel with the rail 15. The platen 25 is arranged between the frame bodies PL and PR on the receiving plate BP, and supports the recording medium P conveyed on the platen 25.

A plurality of suction holes (not shown) are formed in the platen 25, and an air suction device (not shown) for attracting the recording medium P to the platen 25 by negative pressure is arranged below the platen 25. The air suction device includes a fan for suction, and air is sucked through the suction holes by the fan, and the recording medium P is flatly supported by the platen 25.

Further, behind the platen 25, a pre-guide (not shown) as a first medium guide portion is arranged. The pre-guide guides the recording medium P unwound from a feeding roll (not shown) to the platen 25. Therefore, a transport roller pair 30 as a transport member is rotatably arranged between the pre-guide and the platen 25 in the transport direction of the recording medium P.

The transport roller pair 30 is adjacent to the platen 25 and is rotatably arranged at a plurality of locations in the main scanning direction of the carriage 17, as a transport roller (not shown) as a first roller, and rotates above the transport roller. It comprises a pinch roller (not shown) as a second roller that is freely disposed and presses the recording medium P against the transport roller. When the transport motor 34 as a drive unit for transport, which will be described later, is driven and the transport roller is rotated, the pinch roller is rotated along with it.

As a result, the recording medium P is fed out from the feeding roll in a state of being sandwiched between the transport roller and the pinch roller, transported along the pre-guide, and fed onto the platen 25. Then, the recording medium P and the nozzle surface of the recording head Hdi are opposed to each other, ink is ejected from each nozzle, and the ink is adhered to the recording medium P.

Then, in front of the platen 25, an after-guide 33 as a second medium guide portion for guiding the recording medium P after printing is performed and discharging the printing medium P is arranged. The after-guide 33 has a curved shape in order to guide the recording medium P horizontally discharged from the platen 25 downward.

Therefore, the recording medium P unwound from the feeding roll is guided by the pre-guide and sent to the platen 25, and the ink ejected from each nozzle of the recording head Hdi is attached to the platen 25 for printing. After printing is performed, it is guided by the after-guide 33 and sent to a winding device (not shown) for winding.

Ink adheres to the recording medium P immediately after printing is performed, but when the recording medium P is ejected from the platen 25 and wound by the winding device before the ink dries, the ink spreads and the recording medium. P gets dirty with ink.

Therefore, in the present embodiment, in order to dry the ink on the recording medium P and fix it on the recording medium P, a heater (not shown) as a first heating body is embedded in the platen 25, and a pre-guide is also provided. A heater (not shown) as a second and third heating element is attached to the back of the after guide 33, and each heater is covered with an aluminum sheet. Therefore, each heater heats the recording medium P conveyed on the pre-guide, the platen 25, and the after-guide 33.

In the present embodiment, the rail 15 is arranged between both ends of the receiving plate BP, and the platen 25 is arranged between the frame PL and PR, so that the carriage 17 is moved on the platen 25. When the ink is ejected by each recording head Hdi, that is, recording is performed and the carriage 17 is placed on the left side of the frame body PL, and when the carriage 17 is placed on the right side of the frame body PR, recording by each recording head Hdi is performed. Is not done.

Therefore, in the present embodiment, the right side of the frame PR is the home position for aligning the origin of the position of the carriage 17, and the left side of the frame PL retracts the carriage 17 from the platen 25 and folds it back. It is put in the evacuation position.

Then, a cap unit 43 as a maintenance device is arranged at the home position. The cap unit 43 covers the nozzle surface of the recording head Hdi with a cap when the inkjet printer 10 is not used for a long time, thereby preventing the ink from increasing in viscosity or solidifying in the nozzle. Ink is sucked from the recording head Hdi on a regular basis.

By the way, in the present embodiment, the carriage 17 is reciprocated to form an image. Therefore, if the dot positions are different between the outward path and the return path of the carriage 17, the image is displaced and the image is formed. The dignity will deteriorate.

Therefore, in the present embodiment, the test pattern image PA (FIG. 5) described later is formed (printed) on the recording medium P, and the image density of the test pattern image PA is detected and detected by the optical sensor 24. A correction value for correcting the dot position is calculated based on the image density.

Next, the control device of the inkjet printer 10 will be described.

FIG. 1 is a control block diagram of an inkjet printer according to an embodiment of the present invention.

In the figure, 10 is an inkjet printer, 80 is a control unit that controls the entire sequence of the inkjet printer 10 and performs printing control, 81 is a ROM as a first storage device including a non-volatile memory, and 82 is volatile. RAM as a second storage device including memory, 83 is an interface (I / F) control unit that receives print data and control commands from a host computer (not shown) as a host computer, 51 is an operation panel, 53 is a sensor group, 24. Is an optical sensor, 45 is an R detection unit, 46 is a G detection unit, and 47 is a B detection unit.

The control unit 80 includes a CPU (not shown) as an arithmetic unit, an input / output port, a timer, and the like, and performs various processes based on the program recorded in the ROM 81. In addition to the program, various initial setting values, data of the basic pattern image Pt (FIG. 4) described later, and the like are recorded in the ROM 81, and various data are temporarily recorded in the RAM 82. The RAM 82 also functions as a work area when the CPU performs an operation.

The control unit 80 includes a head drive processing unit Pr1, a transfer processing unit Pr2, a carriage drive processing unit Pr3, an image detection processing unit Pr4, a head drive condition setting unit Pr5, and the like.

The head drive processing unit Pr1 generates image data based on print data and control commands sent from the host computer, and drives the recording head Hdi to form an image on the recording medium P. Further, the head drive processing unit Pr1 reads out the data of the basic pattern image Pt recorded in the ROM 81, drives the recording head Hdi based on the data of the basic pattern image Pt, and outputs the test pattern image PA to the recording medium P. Form.

The recording head Hdi is provided with a piezo element 26 as a driving element for each nozzle, and when a predetermined voltage is applied between the electrodes arranged at both ends of the piezo element 26, the voltage becomes a voltage. Accordingly, the piezo element 26 is driven, expanded and contracted, and the side wall of the flow path that sends ink to the nozzle is deformed. As a result, the cross-sectional area of the ink flow path changes according to the expansion and contraction of the piezo element 26, and the amount of ink corresponding to the change in the cross-sectional area of the ink flow path becomes ink droplets and is ejected from the nozzle.

The transport processing unit Pr2 drives the transport motor 34 to rotate the transport roller pair 30 (FIG. 2), and transports the recording medium P in the arrow c direction (sub-scanning direction).

Further, the carriage drive processing unit Pr3 drives the carriage motor 22 by PWM control, runs the endless belt 21, and reciprocates the carriage 17 in the directions a and b (main scanning direction). Therefore, the carriage drive processing unit Pr3 reads the target position and target speed of the carriage 17 from the ROM 81, receives the sensor output of the encoder 35, performs A / D conversion, detects the position of the carriage 17, and uses it as a control value. A PWM control signal is generated and sent to the carriage motor 22. The carriage motor 22 receives the PWM control signal, changes the rotation speed in proportion to the duty of the PWM control signal, accelerates or decelerates the carriage 17, and moves it to the target position at the target speed. Further, the carriage drive processing unit Pr3 sends the position of the carriage 17 to the head drive processing unit Pr1, and the head drive processing unit Pr1 is calculated from the nozzle of the recording head Hdi based on the image data in accordance with the position of the carriage 17. Ink is ejected at the same timing.

Then, the image detection processing unit Pr4 detects the dots and the image density of the test pattern image PA formed on the recording medium P by the optical sensor 24, and corrects the dot positions based on the dots and the image density. The correction value Xk described later is calculated.

Further, the head drive condition setting unit Pr5 sets the correction value Xk as the drive condition of the recording head Hdi in the drive condition dialog formed at the time of printing on the display unit described later.

In the optical sensor 24, the R detection unit 45, the G detection unit 46, and the B detection unit 47 include a light emitting unit composed of an LED or the like and a light receiving unit composed of a phototransistor or the like, and the R detection unit 45 is a light emitting unit. The red light is generated by the light receiving unit, and the reflected light is received by the light receiving unit to detect the image density of the cyan color test pattern image PA. The G detection unit 46 generates green light by the light emitting unit. By receiving the reflected light by the light receiving unit, the image density of the magenta color test pattern image PA is detected, the B detection unit 47 generates blue light by the light emitting unit, and the reflected light is received by the light receiving unit. By doing so, the image density of the yellow color test pattern image PA and the image density of the black color test pattern image PA are detected.

Therefore, the head drive condition setting unit Pr5 sets the correction value calculated for each color as the drive condition of the recording head Hdi.

The operation panel 51 includes an LED screen as a display unit for displaying the state of the inkjet printer 10, a switch, a key, and the like as an operation unit for the operator to give an instruction to the inkjet printer 10. When the operation panel 51 is formed by a touch panel, the operation panel 51 functions as a display unit and an operation unit.

Then, the sensor group 53 detects various sensors for monitoring the operating state of the inkjet printer 10, for example, a medium position detection sensor that detects the position of the recording medium P, and the printing environment in which the inkjet printer 10 is placed. It consists of a temperature sensor, a humidity sensor, etc.

Next, the operation of the control unit 80 when printing is performed in the inkjet printer 10 will be described.

In the inkjet printer 10 of the present embodiment, when print data and control commands are sent from the host computer to the inkjet printer 10 via the interface control unit 83, the transfer processing unit Pr2 drives the transfer motor 34 and the transfer roller. The pair 30 is rotated to convey the recording medium P in the direction of the arrow c.

Subsequently, the carriage drive processing unit Pr3 drives the carriage motor 22 to drive the endless belt 21 and move the carriage 17 in the directions of arrows a and b. At this time, the carriage drive processing unit Pr3 receives the sensor output of the encoder 35, performs A / D conversion, detects the position of the carriage 17, and sends it to the head drive processing unit Pr1, and the head drive processing unit Pr1 is the carriage. In accordance with the position of 17, the ink is ejected from the nozzle of the recording head Hdi at the timing calculated based on the image data.

At this time, the transport processing unit Pr3 drives the transport motor 34 to transport the recording medium P in the direction of arrow c. Therefore, the ink ejected from the nozzle of the recording head Hdi is attached to the recording medium P, and printing is performed.

By the way, the test pattern image PA is formed on the recording medium P by forming the basic pattern image Pt on the outward path and the return path of the carriage 17 by a predetermined method.

FIG. 4 is a diagram showing an example of a basic pattern image according to an embodiment of the present invention, FIG. 5 is a diagram showing an example of a test pattern image according to an embodiment of the present invention, and FIG. 6 is a diagram showing an example of a test pattern image according to an embodiment of the present invention. It is an enlarged view of.

In the figure, Pt is a basic pattern image composed of a striped pattern, PA is formed based on the basic pattern image Pt, and a plurality of, in the present embodiment, nine pattern images Paj (j = 1, 2). , ..., 9) is a test pattern image.

The basic pattern image Pt has a strip-shaped shape, and has a plurality of strip-shaped shapes, and in the present embodiment, four image regions Ar1 formed by ejecting ink, and the ink is formed. In the present embodiment, there are a plurality of non-image regions Ar2 formed by not discharging, and each image region Ar1 and the non-image region Ar2 are alternately arranged adjacent to each other. The basic pattern image Pt is created in various ways according to the situation of the inkjet printer 10 (FIG. 2), for example, the type of the recording medium P used, and is recorded in the ROM 81 (FIG. 1).

In order to form the test pattern image PA based on the basic pattern image Pt, first, the carriage drive processing unit Pr3 moves the carriage 17 in the direction of the arrow a, and the head drive processing unit Pr1 moves the carriage 17 from the ROM 81 to the basic pattern image Pt. The data is read out, and nine basic pattern images Pt are formed on the recording medium P as the first basic pattern image Pt1 on the outward path of the carriage 17.

Subsequently, the carriage drive processing unit Pr3 moves the carriage 17 in the direction of the arrow b, and the head drive processing unit Pr1 makes the timing of ejecting ink different from each other on the return path of the carriage 17, and the first basic pattern image. Eight basic pattern images Pt are newly formed on the recording medium P as the second basic pattern image Pt2 so as to be superimposed on Pt1.

As a result, a test pattern image composed of the pattern image Paj is formed on the recording medium P. The pattern image Pa1 of each pattern image Paj is formed as a reference pattern by forming only the first basic pattern image Pt1 in the outward path of the carriage 17, and the pattern images Pa1 to Pa9 are the outward path of the carriage 17. The first basic pattern image Pt1 is formed in the above, and the second basic pattern image Pt2 is superimposed on the first basic pattern image Pt1 on the return path of the carriage 17, so that the adjustment pattern image is formed.

That is, when the reference timing for ejecting ink is t0, the pattern image Pa6 is formed by superimposing the second basic pattern image Pt2 at the timing t0, and the second basic at the timing t + 1 which is later than the timing t0 by the time τ. The pattern image Pa7 is formed by superimposing the pattern images Pt2, and the pattern image Pa8 is formed by superimposing the second basic pattern image Pt2 at the timing t + 2 later than the timing t0 by the time 2τ, and the timing is delayed by the time 3τ from the timing t0. The pattern image Pa9 is formed by superimposing the second basic pattern image Pt2 at t + 3, and the pattern image Pa5 is formed by superimposing the second basic pattern image Pt2 at the timing t-1 which is time τ earlier than the timing t0. The pattern image Pa4 is formed by superimposing the second basic pattern image Pt2 at the timing t-2, which is time 2τ earlier than the timing t0, and the second basic pattern image Pt2 is formed at the timing t-3, which is time 3τ earlier than the timing t0. The pattern image Pa3 is formed by superimposing the pattern image Pa3, and the pattern image Pa2 is formed by superimposing the second basic pattern image Pt2 at the timing t-4 which is 4τ earlier than the timing t0.

Here, since the pattern images Pa2 to Pa9 are formed by superimposing the second basic pattern image Pt2 on the first basic pattern image Pt1 at timings t + 3 to t-4 on the return path of the carriage 17, FIG. As shown in, the dot px1 formed in the image region Ar1 in the first basic pattern image Pt1 and the dot px2 formed in the image region Ar1 in the second basic pattern image Pt2 are formed at the same dot position. It is not formed at different dot positions.

Therefore, in each of the pattern images Pa2 to Pa9, the number of dots formed in each image region Ar1 is different, so that the image densities of the pattern images Pa2 to Pa9 are different from each other.

Therefore, in the present embodiment, the image density of each pattern image Pa2 to Pa9 is detected, a virtual pattern image having the lowest image density is assumed, and the amount of dot shift in the virtual pattern image is set to the dot position. It is set as a correction value for correction.

Next, the operation of the inkjet printer 10 when correcting the dot position will be described.

FIG. 7 is a flowchart showing the operation of the inkjet printer when correcting the dot position in the embodiment of the present invention, and FIG. 8 is a diagram showing the distribution of the image density of the pattern image in the embodiment of the present invention. In FIG. 8, the horizontal axis represents the dot shift amount X [dots], and the vertical axis represents the image density value V [V].

First, the carriage drive processing unit Pr3 (FIG. 1) drives the carriage motor 22 to reciprocate the carriage 17, and the head drive processing unit Pr1 detects the type of the recording medium P, refers to the ROM 81, and refers to the recording medium. The data of the basic pattern image Pt corresponding to P is read out, the recording head Hdi is driven, and a test pattern image PA composed of each pattern image Paj is formed on the recording medium P (FIG. 2).

Next, the image detection processing unit Pr4 detects the dots and image densities of the test pattern image PA, that is, the dots and image densities of each pattern image Paj by the optical sensor 24. Then, the image detection processing unit Pr4 calculates the dot deviation amount Xj (j = 1, 2, ..., 9) in each pattern image Paj based on the dots of each pattern image Paj.

The dot deviation amount Xj is the position of a predetermined dot formed in the image region Ar1 in the first basic pattern image Pt1 and the predetermined dot formed in the image region Ar1 in the second basic pattern image Pt2. The distance from the position of the dot corresponding to is expressed by the number of dots. Further, since the image density of each pattern image Paj is detected by the optical sensor 24, the image density value Vj (j = 1, 2, ..., 9), which is the sensor output (voltage value) of the optical sensor 24, is the image density. Is large when is low, and is small when the image density is high.

In the present embodiment, the test pattern image PA is formed a plurality of times by the head drive processing unit Pr1, the image density of each pattern image Paj is detected a plurality of times, and the average value of the values of each image density is the image density. The value becomes Vj.

By the way, since the pattern image Pa1 is formed only by the first basic pattern image Pt1 on the outward path of the carriage 17, the dot deviation amount X1 is 0 and the image density value V1 is the largest. Therefore, if the pattern image Pa1 is formed by forming the first and second basic pattern images Pt1 and Pt2 in the same manner as the other pattern images Pa2 to Pa9, the outward path of the carriage 17 And on the return trip, each dot will be formed at the same dot position.

Therefore, when there is a pattern image whose image density value is equal to the image density value V1 of the pattern image Pa1 among the pattern images Pa2 to Pa9, the amount of dot shift of the pattern image is 0, so that the dot position is set. The correction value for correction is 0.

However, as shown in FIG. 8, since the image density values V2 to V9 of the pattern images Pa2 to Pa9 are smaller than the image density value V1 of the pattern image Pa1, the second basic pattern image is at the timing t + 3 to t-4. When Pt2 is formed, each dot is not formed at the same dot position on the outward path and the return path of the carriage 17. Therefore, it is necessary to correct the dot position.

Therefore, in the present embodiment, the image detection processing unit Pr4 sets the image density value V1 of the pattern image Pa1 as a target value, the image density is the lowest, and the image density value V becomes equal to the image density value V1. Assuming the image Pk, the dot deviation amount Xk of the virtual pattern image Pk is calculated as a correction value for correcting the dot position.

Therefore, the image detection processing unit Pr4 is a pattern image having an image density having a small difference from the image density of the reference pattern image Pa1 among the pattern images Pa2 to Pa9, and in the present embodiment, two pattern images. Pa5 and Pa6 are selected, and the virtual image density values V5 and V6 of the pattern images Pa5 and Pa6, the image density values V5 and V6 of the pattern images Pa5 and Pa6, and the image density values V1 of the pattern image Pa1 are used. The deviation amount Xk of the dots of the pattern image Pk is calculated.

In this case, since the virtual pattern image Pk is located between the pattern images Pa5 and Pa6, the weight of the pattern image Pa5 with respect to the virtual pattern image Pk is W1, and the weight of the pattern image Pa6 with respect to the virtual pattern image Pk is W2. Then, the weight W1 can be represented by the difference between the image density values V1 and V5, and the weight W2 can be represented by the difference between the image density values V1 and V6.
W1 = V1-V5
W2 = V1-V6
become. Therefore, the dot shift amount Xk of the virtual pattern image Pk is
Xk = W1 / (W1 + W2) x (X2-X1) + X1
It becomes a correction value for correcting the dot position.

In the present embodiment, two pattern images Pa5 and Pa6 are selected in order to calculate the dot shift amount Xk of the virtual pattern image Pk, but three or more pattern images. You can select Paj.

When the correction value is calculated in this way, the head drive condition setting unit Pt5 sets the head drive condition based on the correction value and adjusts the timing for driving the recording head Hdi. In this way, the dot position can be corrected.

After the dot position is corrected, the test pattern image PA can be formed again on the recording medium P, and the dot position can be further corrected based on the image density of the test pattern image PA.

Further, in the present embodiment, the optical sensor 24 includes an R detection unit 45, a G detection unit 46, and a B detection unit 47, and the R detection unit 45, the G detection unit 46, and the B detection unit 47 provide the pattern images. The dots and image density of Paj are detected. Therefore, the image detection processing unit Pr4 has a deviation amount of dots of the virtual pattern image Pk based on the dots and the image density of each pattern image Paj detected by the R detection unit 45, the G detection unit 46, and the B detection unit 47. Calculate Xk. As a result, the timing for driving the recording head Hdi corresponding to each color is adjusted.

As described above, in the present embodiment, the image density value V1 of the pattern image Pa1 is set as the target value, and the image density value Vk equal to the image density value V1 of the pattern image Pa1 is obtained based on the pattern images Pa5 and Pa6. Since the virtual pattern image Pk to be created is assumed and the dot shift amount Xk of the virtual pattern image Pk is used as a correction value for correcting the dot position, a test pattern image PA is formed on the recording medium P and the image density is increased. Can be detected less frequently. Therefore, the work of correcting the dot position can be simplified, and the time required to correct the dot position can be shortened.

Next, the flowchart will be described.
Step S1 The head drive processing unit Pr1 forms a test pattern image PA on the recording medium P.
Step S2 The image detection processing unit Pr4 detects the image density of the test pattern image PA.
Step S3 The image detection processing unit Pr4 calculates a correction value for correcting the dot position. Step S4 The head drive condition setting unit Pr5 sets the head drive condition based on the correction value and ends the process.

In the present embodiment, one test pattern image PA is created based on the basic pattern image Pt, but the ink used for forming the second basic pattern image Pt2 on the return path of the carriage 17 is used. By changing the ejection timing, it is possible to create a plurality of test pattern images and improve the accuracy of the calculated correction value.

Further, in the present embodiment, the dot position when the carriage 17 is reciprocated is corrected, but a predetermined test pattern image is formed when the recording medium P is conveyed, and the test pattern image is formed. The dot position can be corrected based on the image density of.

And although the inkjet printer 10 is described in the above-described embodiment, the present invention can be applied to an image forming apparatus such as a copying machine, a facsimile, and a multifunction device.

The present invention is not limited to the above-described embodiment, and various modifications can be made based on the gist of the present invention, and these are not excluded from the scope of the present invention.

10 Inkjet printer 17 Carriage 22 Carriage motor 34 Carriage motor Hdi Recording head P Recording medium Pa1 to Pa9 Pattern image PA Test pattern image Pr1 Head drive processing unit Pr2 Carriage processing unit Pr3 Carriage drive processing unit Pr4 Image detection processing unit Pr5 Head drive condition setting Department

Claims (4)

(A) A carriage arranged so as to be movable in the main scanning direction, and
(B) A plurality of recording heads mounted on the carriage and
(C) A carriage drive processing unit that drives a drive unit for moving the carriage to reciprocate the carriage, and
(D) A transport processing unit that drives a transport drive unit to transport the recording medium in the sub-scanning direction.
(E) A reference pattern image formed only in the outward path of the reciprocating movement of the carriage and a test pattern image composed of a plurality of adjustment pattern images formed in the outward path and the return path are formed on the recording medium by driving each recording head. Head drive processing unit and
(F) The dot and image density of the test pattern image are detected by the image density detection unit, and the dot position is determined based on the dot and image density of the reference pattern image and the dot and image density of the plurality of adjustment pattern images. An image detection processing unit that calculates the correction value for correction,
(G) An inkjet printer comprising a head drive condition setting unit that sets a correction value calculated by the image detection processing unit as a drive condition of a recording head. The correction value is calculated based on the image density value of the reference pattern image and the image density value of two adjustment pattern images having an image density having a small difference from the image density of the reference pattern image and the amount of dot deviation. The inkjet printer according to claim 1. The test pattern image forms a plurality of first basic pattern images on the outward path of the carriage, and is superimposed on each of the first basic pattern images on the return path of the carriage, and the timings of the test pattern images are different from each other. The inkjet printer according to claim 1 or 2, which is formed by forming a basic pattern image. (A) The head drive processing unit forms a plurality of test pattern images corresponding to the colors of ink, and forms a plurality of test pattern images.
(B) The image density detection unit detects dots and image density of each test pattern image by a plurality of color detection units arranged corresponding to the ink color, and calculates a correction value for each ink color. The inkjet printer according to any one of claims 1 to 3.

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