JP2021074938A - Liquid discharge device, liquid discharge method, liquid discharge program - Google Patents

Abstract

To provide a technology which suppresses density unevenness of an image by correcting deviation of a landing position of a liquid with high precision even when a gap distance is fluctuated by thermal deformation of a platen.SOLUTION: A liquid discharge device includes: a platen which supports a recording medium; a platen holding member which holds the platen; heating means which heats until a temperature of the platen reaches a set temperature; a head which forms an image by discharging the liquid to the recording medium supported by the platen; moving means which makes the head scan in a direction intersecting a conveying direction of the recording medium; temperature detection means which detects at least the temperature of the platen and a temperature of the platen holding member; and control means which controls discharge of the liquid. The control means controls the discharge of the liquid on the basis of the set temperature of the platen, an ambient temperature before heating, and a time from when the temperature of the platen reaches the set temperature until the temperature of the platen holding member reaches the set temperature.SELECTED DRAWING: Figure 3

Description

The present invention relates to a liquid discharge device, a liquid discharge method, and a liquid discharge program.

Generally, a liquid ejection device for ejecting a liquid such as ink to a medium such as paper is known. An inkjet type image forming apparatus provided with a liquid ejection device and forming an image on a medium by the ejected liquid is also widely known.

This inkjet image forming apparatus includes a platen for supporting a long recording medium (media such as paper) and a recording head for ejecting ink to the recording medium supported on the platen. There is also a model. The image forming apparatus having the platen conveys the recording medium onto the platen from the upstream side in the conveying direction, and ejects ink from the recording head to the recording medium in a paused state to form an image.

Further, in an image forming apparatus having such a platen, in order to control the permeability and fixability of the ink that has landed on the recording medium at the time of image formation, the recording medium supported on the platen is heated via the platen. It is heated by (heating device).

A related technique is to adjust the distance (gap) between the nozzle surface and the outer peripheral surface by moving the discharge head back and forth to a predetermined position in the normal direction of the outer peripheral surface of the drum according to the temperature of the transport drum. It is disclosed (for example, Patent Document 1).

When the recording medium is heated through the platen, the surface of the platen supporting the recording medium may be deformed due to thermal expansion. Deformation of the surface of the platen that supports the recording medium affects the accuracy of the position (landing position) at which the ink ejected from the ejection head adheres to the recording medium.

An object of the present invention is to correct the deviation of the landing position of the liquid with high accuracy and suppress the uneven density of the image even when the distance (gap) fluctuates due to the thermal deformation of the platen.

In order to solve the above problems, the present invention relates to a liquid discharge device, which comprises a platen that supports a recording medium, a platen holding member that holds the platen, a heating means that heats the platen until the temperature reaches a set temperature, and a platen. A head that ejects liquid toward a recording medium supported by the device to form an image, a moving means that scans the head in a direction intersecting the transport direction of the recording medium, and at least the temperature of the platen and the temperature of the platen holding member. The control means includes a temperature detecting means for detecting and a control means for controlling the discharge of the liquid, and the control means sets the set temperature of the platen, the ambient temperature before heating, and the temperature of the platen to the set temperature. It is characterized in that the discharge of the liquid is controlled based on the time from when the temperature of the platen holding member reaches the set temperature.

According to the present invention, even when the gap distance fluctuates due to thermal deformation of the platen, it is possible to correct the deviation of the landing position of the liquid with high accuracy and suppress the density unevenness of the image.

It is a figure which shows the image forming apparatus which is the embodiment of the liquid discharge apparatus which concerns on this invention. It is a schematic diagram which illustrates the cross-sectional structure of the image forming apparatus of an embodiment. It is the schematic explaining the occurrence of thermal deformation of a platen. It is a figure which shows the thermal deformation amount of a platen, and the temperature change of a platen and a platen holding member. It is a figure explaining the ink ejection speed. It is a figure explaining the ink landing position. It is a figure explaining the 1st mode of finding the distance between a printhead and a platen by calculation. It is a figure which shows an example of the correction table used in the 1st aspect of finding the distance between a printhead and a platen. It is a figure which shows the configuration example about the 2nd aspect which obtains the distance between a printhead and a platen by using a sensor. It is a figure which shows the structural example of the control system of the image forming apparatus of an embodiment, and is the figure which shows the 1st structure. It is a figure explaining adjustment of discharge timing. It is a figure which illustrates the 2nd structure which concerns on the correction of a discharge rate. It is a figure explaining the correction of a discharge rate. It is a flowchart which shows the operation example of embodiment.

Hereinafter, the liquid discharge device, the liquid discharge method, and the liquid discharge program according to the embodiment will be described with reference to the drawings. In the following description, the "recording medium" means a sheet-like medium such as paper (paper), OHP sheet, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, etc., and here, the paper medium is used. It will be described as being used. Further, "image formation" means not only giving an image having a meaning such as characters and figures to the sheet, but also giving an image having no meaning such as a pattern to the sheet.

The dimensions, materials, shapes, relative arrangements, and the like of each component described in the following embodiments are examples, and the scope of the present invention is not intended to be limited thereto unless otherwise specified.

FIG. 1 is a diagram showing an overall configuration of an image forming apparatus according to the present embodiment. The image forming apparatus 1000 is a serial type liquid ejection type image forming apparatus, and is provided with a main guide rod 1 and a sub guide rod 2 inside. The carriage 20 (moving means) is supported by the main guide rod 1 and the sub guide rod 2.

Further, in the image forming apparatus 1000, an endless belt-shaped timing belt 6 is arranged along the main guide rod 1. The timing belt 6 is hung around the drive pulley 7 and the driven pulley 8. The drive pulley 7 is driven by the rotation of the main scanning motor 12 connected to the drive pulley 7, and the timing belt 6 is rotated by the drive of the drive pulley 7.

The carriage 20 is connected to the timing belt 6. By connecting the carriage 20 and the timing belt 6, the timing belt 6 is rotated in the forward and reverse directions, so that the carriage 20 is reciprocated in the main scanning direction (A direction in the drawing).

The carriage 20 has a recording head (print head 10 shown in FIG. 2) that ejects at least one ink (liquid) of yellow (Y), magenta (M), cyan (C), and black (K). ing.

Further, the image forming apparatus 1000 intermittently conveys the recording medium P fed from the paper feeding unit in the sub-scanning direction (direction B in the drawing) by using the sub-scanning motor, and is in the sub-scanning direction of the recording medium P. The carriage 20 is moved in the main scanning direction while the transport is stopped. Then, the image forming apparatus 1000 can form an image on the recording medium P by ejecting the liquid from the recording head as the carriage 20 moves.

Further, the image forming apparatus 1000 has a maintenance mechanism 3 for maintaining the quality of the image. The maintenance mechanism 3 maintains the image quality by, for example, cleaning the discharge surface of the recording head or discharging unnecessary liquid from the recording head.

FIG. 2 is a schematic view illustrating the cross-sectional configuration of the image forming apparatus 1000. The carriage 20 supports the print head 10 and causes the print head 10 to travel in the main scanning direction (depth direction in FIG. 2) above the platen 30 which is a flat metal plate.

The transport means 50 transports the recording medium P in the direction of the arrow, and transports the recording medium P on the platen 30. The transport means 50 is located upstream of the platen 30 in the transport direction of the recording medium P, and is composed of a feed roller 51 and a presser roller 52. The transporting means 50 transports the recording medium P onto the platen 30 by sandwiching the recording medium P between the feed roller 51 and the presser roller 52 and rotating the feed roller 51.

A heater 70 (heating means) is provided on the platen 30 and the transport paths 60 provided on the upstream side and the downstream side of the platen 30. The heater 70 heats the platen 30 to heat the recording medium P from the side facing the ink landing surface. The heater 70 heats the recording medium P on the transport path 60 from the back surface of the landing surface of the ink droplets in order to control the permeability and fixability of the ink. The heater 70 may have a structure for heating the recording medium P on the transport path 60, and an electric heater using ceramic or nichrome wire can be used.

A fan 80 and an air chamber 90 for holding an intake force (negative pressure) generated by the rotation of the fan 80 are provided in the lower portion of the platen 30, and the platen 30 has a hole for sucking the recording medium P by air. Is provided. With this configuration, the rotation of the fan 80 suppresses the floating of the recording medium P from the platen 30.

The image forming apparatus 1000 includes a feeding means 100 and a winding means 110. The feeding means 100 is provided on the upstream side of the platen 30 in the transport direction of the recording medium P, and feeds the recording medium P wound in a roll shape toward the platen 30. The winding means 110 is provided on the downstream side of the platen 30 in the transport direction of the recording medium P, and winds the printed recording medium P sent out from the platen 30 in a roll shape.

FIG. 3 is a schematic view illustrating the occurrence of thermal deformation of the platen 30. As described above, the platen 30 is heated by the heater 70, and the fan 80 for forming the negative pressure and the air for holding the negative pressure are held in order to suppress the floating of the recording medium P in the image forming region. The chamber 90 is usually configured. The platen holding member 200 has a structure in which the air chamber 90 and the duct for guiding the exhaust gas by the fan 80 are integrated.

The platen holding member 200 is a member that holds the platen 30. The platen 30 and the platen holding member 200 are fixed by surrounding the entire circumference with a sealing material 210. Further, the platen holding member 200 has a structure in which the platen 30 is sandwiched between sheet metals urged by a spring force, and the platen 30 slides due to thermal expansion.

Normally, since the platen 30 is heated to a higher temperature than the outside air temperature by the heater 70, the heat is transferred to the platen holding member 200 and the temperature of the platen holding member 200 also rises.

On the other hand, since there is no heating element on the side of the platen holding member 200 that does not face the platen 30 and heat is dissipated, a temperature difference occurs in the height direction of the platen 30 and the platen holding member 200. Therefore, in the conventional configuration, there is a difference in thermal expansion in the height direction of the platen 30 and the platen holding member 200, resulting in deformation in which the center is convex. This deformation occurs largely in the main scanning direction, which is the longitudinal direction, and the peak of the amount of deformation is at the center position.

FIG. 4A shows the maximum amount of thermal deformation of the platen 30 when heated by the heater 70, starting from the time when the temperature of the platen 30 and the platen holding member 200 are sufficiently stable at the environmental temperature F1 (ambient temperature before heating). It shows a large amount (um) of temporal change (min). Further, FIG. 4B shows the temporal changes in the temperatures of the platen 30 and the platen holding member 200.

The magnitude of thermal deformation of the platen 30 is proportional to the temperature difference between the platen 30 and the platen holding member 200. In the example of FIG. 4A, when the temperature of the platen 30 (referred to as the platen temperature) is the time t1 when the platen 30 is heated to the set temperature F2, the temperature difference between the platen 30 and the platen holding member 200 becomes maximum. Thermal deformation a1 occurs.

After that, while the platen 30 is kept warm at the set temperature F2 between t1 and t2, the platen holding member 200 approaches the temperature F2 with a delay, so that the amount of thermal deformation decreases and becomes thermal deformation a2 at time t2. , Almost stable.

In the present embodiment, the platen 30 is made of aluminum and the platen holding member 200 is made of SECC (steel plate plated with electrogalvanized steel). Since the amount of heat deformation (elongation amount) of each material is different, the amount of heat deformation at the temperature F2 does not become zero and a2 remains. Further, the image forming apparatus 1000 starts the image forming operation from the time t1 when the platen temperature reaches the set temperature F2.

The values of a1 and a2 differ depending on the environmental temperature, the set temperature, and the structure of the entire platen. Here, a correction table (see FIG. 8 described later) based on two parameters of each set temperature and each environmental temperature is prepared in advance, and correction control is performed according to the table.

FIG. 5 is a diagram showing an ink ejection speed. The ink is ejected while moving the carriage 20 in the main scanning direction. Therefore, the ink dot ejection speed is indicated by the combined velocity Vr of the moving speed Vm of the print head 10 in the main scanning direction and the ink ejection speed Vg. That is, since the ink ejected from the print head 10 moves in the main scanning direction until it lands on the recording medium P, the ejection position and the impact position do not match in the height direction (the impact position does not fall directly below the ejection position). ).

FIG. 6A is a diagram showing an ink landing position when the carriage 20 is moved at a constant speed in the main scanning direction using a flat platen 30 and ink dots are ejected at equal intervals. In this case, the deviation between the ejection position and the landing position changes depending on the moving speed of the carriage 20 and the distance from the head nozzle surface to the recording medium P on the platen 30, but the ink landing positions are evenly spaced like the ejection position. Become.

FIG. 6B is a diagram showing an ink landing position when the carriage 20 is moved at a constant speed in the main scanning direction using a platen 30 curved in a convex direction and ink dots are ejected at equal intervals. In this case, in the section in the downward direction along the drive direction of the carriage 20 (the section “A” shown in FIG. 6 (B)), the ink landing position gradually widens and the section in the upward direction (“B”). In the section), the ink landing position gradually narrows. In this way, if there is a difference in the interval between the ink landing positions, a color change or a color shift occurs. This phenomenon becomes more prominent as the moving speed of the carriage 20 increases, and becomes more prominent as the curvature of the platen 30 increases.

Hereinafter, an example of an embodiment for alleviating the gap between the ink landing positions caused by the curvature of the platen 30 will be described. In order to alleviate the difference in the distance between the ink landing positions, it is necessary to determine how much the platen 30 is distorted. In the following, the distance between the print head 10 and the platen 30 (gap distance in the height direction) is obtained for each predetermined sampling interval, and the ejection timing, ejection speed, and scanning speed of the carriage 20 of the print head 10 are determined based on this distance. A mode of control will be described.

Further, in the following description, first, two aspects of obtaining the distance between the print head 10 and the platen 30 will be described, and then correction values (values before correction) of the discharge timing of the print head 10, the discharge speed, and the scanning speed of the carriage 20 will be described. The calculation method of (difference from) will be described.

First, a first aspect of obtaining the distance between the print head 10 and the platen 30 by calculation will be described. FIG. 7A is a diagram showing the amount of thermal deformation at the center position of the platen, and here, it is assumed that the amount of deformation from t1 to t2 shown in FIG. 4A is linearly approximated.

Assuming that the amount of thermal deformation at the center position at a certain time T is Z, Z can be expressed by the following equation.
(When t1 ≦ T ≦ t2): Z = a1 + (a2-a1) / (t2-t1) × (T−t1)
(Equation 1)
(When t2 <T): Z = a2 ... (Equation 2)
When T is from 0 to t1, the platen 30 is not sufficiently warmed, that is, a state of preparation for image formation. Therefore, since no image formation is performed, it is not necessary to calculate the amount of deformation.

FIG. 7B is a top view and a front view of the platen 30 and the recording medium P. Assuming that the total length of the platen 30 in the main scanning direction is 2 × L1, the peak position of the amount of thermal deformation of the platen 30 is the position (center position) at the distance L1 from the end, and the length in the height direction is Z. is there. Here, it is assumed that the thermal deformation occurs in the convex direction, and the amount of deformation decreases as the distance from the center position increases.

FIG. 7C is a diagram in which the amount of thermal deformation (= front view of FIG. 7B) at the main scanning position of the platen 30 is shown by a broken line, and a straight line that approximates the amount of thermal deformation is shown by a solid line. Assuming that the amount of thermal deformation at the main scanning position L of the platen 30 is Z', Z'can be indicated by the following equation.
(When 0 <L ≤ L1): Z'= Z / L1 × L ... (Equation 3)
(When L1 <L ≦ 2L1): Z'= ZZ / L1 × (L-L1) ... (Equation 4)

Although the calculation formula for calculating the amount of thermal deformation is shown in this way, it is possible by creating a correction table of the parameters required for the calculation in advance and storing it in the memory.

FIG. 8 shows the time (t2-t1) from when the environmental temperature (F1), the set temperature (F2), and the platen 30 reach the set temperature (F2) until the platen holding member 200 reaches the set temperature (F2). It is a correction table associating (time until the platen holding member 200 stabilizes), the maximum displacement amount (a1) of the platen 30, and the displacement amount (a2) when the platen 30 stabilizes. By using this correction table, the environmental temperature (F1) is measured by a temperature sensor or the like, and this and the preset temperature (F2) are used as input parameters in each of the above mathematical formulas (t2-). t1), a1 and a2 can be derived.

Next, a second aspect of determining the distance between the print head 10 and the platen 30 by distance measurement will be described. FIG. 9 is a diagram showing a configuration in which the distance detection sensor 120 is mounted in addition to the configuration shown in FIG.

The distance detection sensor 120 is an optical (laser) sensor and faces the direction of the platen 30 and the recording medium P directly below. By scanning the carriage 20 in a direction intersecting the transport direction of the recording medium P on the platen 30 and detecting the distance at a predetermined sampling interval, between the nozzle surface of the print head 10 in the main scanning direction and the recording medium P. Can get the gap.

In addition, by detecting the distance at the same time as the scanning operation at the time of image formation, the distance data acquired at the Nth scan can be applied to the result of the (N + 1) th scan, and it is possible to correct in real time. Become.

The type of the distance detection sensor 120 is not limited to the optical type, but may be an ultrasonic type or a contact type.

Next, based on the distance obtained in the first and second aspects described above (this distance is defined as the measured value Lz), the correction values of the discharge timing, discharge speed, and scanning speed of the carriage 20 (before correction). The calculation method of (difference from the value of) will be described. When Lz is large, the gap between the ink landing positions can be alleviated by advancing the ejection timing, increasing the ejection speed, or decreasing the scanning speed. When Lz is small, on the contrary, by delaying the ejection timing, slowing down the ejection speed, or increasing the scanning speed, it is possible to alleviate the difference in the interval between the ink landing positions.

Hereinafter, a specific calculation method will be described. here,
Lz: Measured value from print head 10 to platen 30 L0: Set value from print head 10 to platen 30 Vg: Ink ejection speed (before correction)
Vm: Head scanning speed (before correction)
Then, the discharge speed change amount (ΔVg), which is a correction value, can be obtained as follows in order to make the time Ta from discharge to landing equal.
Ta = Lz / (Vg + ΔVg) = L0 / Vg
Lz * Vg = L0 * (Vg + ΔVg)
ΔVg = (Lz-L0) / L0 * Vg

Next, a method of obtaining the scanning speed change amount (ΔVm), which is a correction value related to the scanning speed, will be described. For each of L0 and Lz, the times Ta and Tb from discharge to landing are as follows.
Ta = L0 / Vg
Tb = Lz / Vg
Further, in order to make the deviation amount Xa of the landing position in the main scanning direction at that time equal.
Xa = Vm * Ta = (Vm + ΔVm) * Tb
Vm * L0 / Vg = (Vm + ΔVm) * Lz / Vg
ΔVm = (L0-Lz) / Lz * Vm
In this way, the amount of change in scanning speed (ΔVm) can be obtained.

A method of obtaining the discharge timing change amount (ΔTz), which is a correction value related to the discharge timing, will be described. Here, the case of discharging earlier than the standard is defined as a positive value, and the case of discharging later is defined as a negative value. For each of L0 and Lz, the times Ta and Tb from discharge to landing are as follows.
Ta = L0 / Vg
Tb = Lz / Vg
Since the scanning speed is assumed to be constant, the difference between Ta and Tb may be used as the discharge timing change amount.
ΔTz = Tb-Ta = (Lz-L0) / Vg
In this way, the discharge timing change amount (ΔTz) can be obtained.

Subsequently, the configuration of the control system of the image forming apparatus 1000 will be described. FIG. 10 is a block diagram illustrating a first configuration relating to a control system, and is a diagram showing a liquid discharge device of the present embodiment. The configuration shown in FIG. 10 is merely an example, and other configurations, for example, the second configuration described with reference to FIG. 12 may be included.

FIG. 10 shows a PC 1001 which is a personal computer for a user to select an image input and a print mode, a RIP unit 1002 which is installed in the PC 1001 and performs image processing according to a color profile and a user's setting, and an image. A rendering unit 1003 that decomposes the data into image data for each scan is shown.

Further, the image forming apparatus 1000 shown in FIG. 10 receives the image data and commands transmitted from the PC 1001 and controls the printer system with the system control unit 1038, and the image data for temporarily storing the image data transmitted from the PC 1. It has a storage unit 1032 and a memory control unit 1033 that controls the image data storage unit 1032.

The image forming apparatus 1000 includes the above heater 70 for heating the platen 30, a temperature sensor 1036 (temperature detecting means) which is a group of sensors for detecting the temperature of the platen 30 and the temperature of the platen holding member 200, and an output of the temperature sensor 1036. It has a heater control unit 1034 that controls turning on and off of the heater 70 so as to keep the temperature of the platen 30 constant from the signal. The temperature sensor 1036 may include a sensor that detects the ambient temperature of the image forming apparatus 1000 in the configuration.

The image forming apparatus 1000 includes an encoder sensor 1041 that optically detects each slit of a linear encoder provided extending in the main scanning direction, a resolution of image data received from the PC 1001, and an output signal of the encoder sensor 1041. It also has a discharge cycle signal generation unit 1037 that generates a discharge cycle signal from the output signal of the temperature sensor 1036. In the present embodiment, the discharge cycle signal generation unit 1037 (which may be the system control unit 1038) calculates the discharge timing change amount (ΔTz), and outputs the signal in the corrected discharge cycle. The discharge cycle adjustment method will be described later (see FIG. 11).

Further, the image forming apparatus 1000 includes a carriage control unit 1007 that calculates the position information of the carriage 20 from the output signal of the encoder sensor 1041 and controls the speed of the main scanning motor 12. In the present embodiment, the system control unit 1038 (which may be the system control unit 1038) calculates the scanning speed change amount (ΔVm). Then, the system control unit 1038 controls the speed of the carriage 20 based on the scanning speed change amount (ΔVm).

The controller board 1013 (control means) includes the system control unit 1038, the image data storage unit 1032, the memory control unit 1033, the discharge cycle signal generation unit 1037, and the carriage control unit 1007. The controller board 1013 has an arithmetic processing unit and a storage device, and the arithmetic processing unit executes a program recorded in advance in the storage device to realize each of these functional units.

The image forming apparatus 1000 has a head drive control unit 1014 that drives the print head 10. The head drive control unit 1014 uses the drive waveform data storage unit 1065 for storing the drive waveform for driving the print head 10 and the drive waveform data read from the drive waveform data storage unit 1065 as a trigger for the discharge cycle signal. It has a drive waveform generation unit 1066 that outputs to the A converter 1062. Further, the head drive control unit 1014 includes a D / A converter 1062 that converts drive waveform data into analog data, a voltage amplification unit 1063 that amplifies the voltage of the analog data, and a current amplification unit 1064 that amplifies the current. The print head 10 is driven and controlled by a drive waveform output from the current amplification unit 1064.

The RIP unit 1002 and the rendering unit 1003 may be combined with each other in a configuration included in the system control unit 1038 instead of in the PC 1001.

FIG. 11 is a diagram showing the discharge timing of the drive waveform generated by the discharge cycle signal generation unit 1037, and is a diagram for explaining the adjustment of the output timing. The discharge cycle signal generation unit 1037 inputs a base cycle signal and delays the cycle of this signal to determine the discharge cycle of the print head 10. Then, the discharge cycle signal generation unit 1037 can specify this delay between 1 and 13 with 7 as the default value.

The waveform when the default value 7 is delayed is shown in FIG. 11 (A). In FIG. 11, the timing shown in FIG. 11A is used as a reference. For example, assuming that the default timing value is 7 as shown in FIG. 11 (A), the discharge cycle signal generation unit 1037 delays the discharge timing by setting it to, for example, 8 to 13 as shown in FIG. 11 (B). Can be done. On the contrary, as shown in FIG. 11C, the discharge cycle signal generation unit 1037 can accelerate the discharge timing by setting the value to less than 7, for example, 1 to 6. This makes it possible to finely adjust the ejection timing of 1 dot or less.

Subsequently, the second configuration related to the correction of the discharge speed will be described with reference to FIG. The second configuration shown in FIG. 12 is a configuration included in the image forming apparatus 1000, and is a diagram for realizing one function that the liquid discharging apparatus can perform.

The waveform correction unit 1201 is mounted on the controller board 1013 shown in FIG. 10, and includes an image data output unit 1211, a pixel count unit 1212, a drive waveform correction value calculation unit 1213, a drive waveform table 1214, and a drive waveform correction unit 1215. Have. Between the waveform correction unit 1201 and the print head 10, there is a head control unit corresponding to the head drive control unit 1014 shown in FIG.

The image data output unit 1211 specifies the image data to be ejected in the next cycle from the image data input from the outside. Then, the image data output unit 1211 outputs the specified image data to the print head 10 via the pixel count unit 1212 and the head control unit. The image data output unit 1211 outputs image data at a predetermined cycle, for example, every scan.

The pixel counting unit 1212 counts the number of nozzles to be driven at the same time based on the image data input from the image data output unit 1211. The pixel counting unit 1212 counts the number of nozzles to be driven at the same time, and then outputs the number of the nozzles to the driving waveform correction value calculation unit 1213.

A table showing the relationship between the drive waveform correction value and the number of drive nozzles is stored in advance in the storage device of the waveform correction unit 1201, and the drive waveform correction value calculation unit 1213 is a drive nozzle input from the pixel count unit 1212. The drive waveform correction value is acquired based on the number and the table. The drive waveform correction value calculation unit 1213 calculates the discharge rate change amount (ΔVg) by the method described above, and further corrects the acquired drive waveform correction value.

The correction value calculated by the drive waveform correction value calculation unit 1213 and the drive waveform stored in the drive waveform table 1214 are input to the drive waveform correction unit 1215. The drive waveform correction unit 1215 performs correction processing, and the corrected drive waveform is output to the print head 10 via the head drive control unit.

FIG. 13 is a diagram for explaining the correction of the drive waveform performed by the waveform correction unit 1201. FIG. 13A is a drive waveform stored in the drive waveform table 1214, and is a drive waveform before correction is performed by the waveform correction unit 1201. Further, FIG. 13B is a drive waveform after correction by the waveform correction unit 1201.

The correction of the drive waveform is performed on a voltage value other than the specified voltage value called an intermediate potential. FIG. 13B shows a case where the drive waveform magnification is corrected from the reference value 1 to 1.2, and the amplitude value other than the intermediate potential is multiplied by 1.2. By correcting the amplitude of the drive waveform centered on the intermediate potential, that is, the portion other than the intermediate potential, the ejection speed of the print head 10 and the ejection amount of ink can be changed.

Finally, the control operation in the first aspect described above will be described with reference to the flowchart of FIG. In the flowchart of FIG. 14, arithmetic processing is performed using the above-described (Equation 1) to (Equation 4). Here, (Equation 1) to (Equation 4) will be described again.
(When t1 ≦ T ≦ t2): Z = a1 + (a2-a1) / (t2-t1) × (T−t1)
(Equation 1)
(When t2 <T): Z = a2 ... (Equation 2)
(When 0 <L ≤ L1): Z'= Z / L1 × L ... (Equation 3)
(When L1 <L ≦ 2L1): Z'= ZZ / L1 × (L-L1) ... (Equation 4)

The controller board 1013 operates the temperature sensor 1036 to start measuring the temperature of the platen 30 and the temperature of the platen holding member 200 (S1401). In the present embodiment, the temperature of the platen 30 and the platen holding member 200 at this stage (before the operation of the heater 70) is regarded as the same temperature as the ambient temperature, and the temperature obtained at the start of this measurement is set as the environmental temperature F1. It shall be handled. On the other hand, a temperature sensor for measuring the ambient temperature may be provided.

The controller board 1013 uses the acquired environmental temperature F1 and the set temperature F2 provided in advance with reference to the correction table shown in FIG. 8, and is associated with (t2-t1), displacement amount (a1), and displacement amount. (A2) is acquired.

The controller board 1013 turns on the heater 70 (S1402). Then, the controller board 1013 waits for processing until the temperature of the platen 30 reaches the set temperature F2 (S1403: No loop). When the temperature of the platen 30 reaches the set temperature F2 (S1403: Yes), the controller board 1013 is in the period from the time (= t1) at this time to the elapse of the time (t2-t1) acquired from the correction table. , Time is elapsed (S1404).

The controller board 1013 is obtained from the correction table of FIG. 8 (t2-t1), the displacement amount (a1), the displacement amount (a2), and the elapsed time (T-t1) from (t1) to the current time (T). Is substituted into the above (Equation 1), and in addition to this, the amount of thermal deformation (Z') is calculated by using (Equation 3) or (Equation 4) according to the current position L. The controller board 1013 acquires the current position L (= current position of the print head 10) in the scanning direction of the carriage 20 from a separately provided position detecting means, and obtains a thermal deformation amount (Z') according to the position. Calculate using (Equation 3) or (Equation 4). Then, the controller substrate 1013 controls the ejection of ink based on the amount of thermal deformation (Z') (S1405). The ink ejection control is a process of calculating correction values for the ejection timing of the print head 10, the ejection speed, and the scanning speed of the carriage 20, and ejecting the ink including the correction values. In the present embodiment, any one of the control of the discharge timing, the discharge speed, and the scanning speed is performed, but these may be combined.

Image formation while performing ejection control by this correction table is performed until the time of (t2-t1) elapses (S1406: No loop).

When the time of (t2-t1) elapses (S1406: Yes), the controller board 1013 has elapsed up to t2 at this point. Therefore, according to the above (Equation 2) and the current position L (Equation 3). ) Or (Equation 4) is used to calculate the amount of thermal deformation (Z'), and the control is changed so that the ink ejection control is based on the amount of thermal deformation (Z') (S1407).

S1407 is performed until the image formation is completed (S1408: No loop), and when the image formation is completed (S1408: Yes), the processing of the flowchart of FIG. 14 is completed.

Next, the outline of the operation of the second mode described above will be described. In the second mode, since the distance detection sensor 120 is used to measure the gap in real time for each scan, a correction table is not required and time measurement is not required.

The controller board 1013 waits until the temperature of the platen 30 reaches the set temperature F2 (t1 elapsed) (corresponding to S1401 to S1403 in FIG. 14).

The controller board 1013 controls the carriage 20 so as to perform an empty scan in the main scanning direction only for the first time, and samples a plurality of gaps. The gap obtained by this empty scan is used in the first scan (first line).

The controller board 1013 performs ejection control based on the previously acquired gap to form an image, and simultaneously performs distance measurement. That is, the gap acquired during the N-1 scan is used for the discharge control during the N scan. By repeating this operation, the controller substrate 1013 forms an image for each line to derive a thermal deformation amount (Z'), and performs ink ejection control based on the thermal deformation amount (Z'). Then, the controller board 1013 ends the process when the formation of all the lines is completed.

In the present embodiment, as an example of the amount of thermal deformation of the platen 30, the distance from the print head 10 to the platen 30 (the gap distance directly under the print head 10) is determined. As a method for obtaining the amount of thermal deformation, the set temperature (F2) of the platen 30, the ambient temperature (F1) before heating, and the platen holding member 200 set the temperature (F2) after the platen 30 reaches the set temperature (F2). The first aspect of deriving the amount of thermal deformation based on the time until reaching F2) (t2-t1) has been described. A second aspect of having a distance detection sensor 120 (detection means) for detecting the amount of thermal deformation of the platen 30 in the scanning direction of the printhead 10 and detecting the amount of thermal deformation in the scanning direction by the sensor will also be described. did. The first aspect and the second aspect may be combined.

As described above, according to the present embodiment, even when the gap distance fluctuates due to thermal deformation of the platen, the deviation of the ink landing position can be corrected with high accuracy and the density unevenness of the image can be suppressed.

10: Printhead 20: Carriage 30: Platen 50: Conveying means 70: Heater 80: Fan 90: Air chamber 120: Distance detection sensor 200: Platen holding member 1000: Image forming apparatus 1007: Carriage control unit 1013: Controller board 1014: Head drive control unit 1032: Image data storage unit 1033: Memory control unit 1034: Heater control unit 1036: Temperature sensor 1037: Discharge cycle signal generation unit 1038: System control unit 1041: Encoder sensor 1062: D / A converter 1063: Voltage amplification Unit 1064: Current amplification unit 1065: Drive waveform data storage unit 1066: Drive waveform generation unit 1201: Waveform correction unit 1211: Image data output unit 1212: Pixel count unit 1213: Drive waveform correction value calculation unit 1214: Drive waveform table 1215: Drive waveform correction unit

Japanese Unexamined Patent Publication No. 2017-39323

Claims (7)

Platens that support recording media and
A platen holding member for holding the platen and
A heating means that heats the platen until the temperature reaches the set temperature, and
A head that ejects a liquid toward a recording medium supported by the platen to form an image, and
A moving means for scanning the head in a direction intersecting the transport direction of the recording medium, and
A temperature detecting means for detecting at least the temperature of the platen and the temperature of the platen holding member, and
A control means for controlling the discharge of the liquid and
Have,
The control means includes the set temperature of the platen, the ambient temperature before heating, and the time from when the temperature of the platen reaches the set temperature until the temperature of the platen holding member reaches the set temperature. A liquid discharge device characterized by controlling the discharge of the liquid based on the above. Further comprising a detecting means for detecting the amount of thermal deformation of the platen in the scanning direction of the head.
The liquid discharge device according to claim 1, wherein the control means controls the discharge of the liquid based on the amount of thermal deformation in the scanning direction detected by the detection means. The liquid discharge device according to claim 1 or 2, wherein the control means corrects the landing position of the liquid by changing the discharge timing of the liquid as control of the discharge. The liquid discharge device according to claim 1 or 2, wherein the control means corrects the landing position of the liquid by changing the discharge speed of the liquid as control of the discharge. The liquid discharge device according to claim 1 or 2, wherein the control means corrects the landing position of the liquid by changing the scanning speed of the head as control of the discharge. Platens that support recording media and
A platen holding member for holding the platen and
A heating means that heats the platen until the temperature reaches the set temperature, and
A head that ejects a liquid toward a recording medium supported by the platen to form an image, and
A moving means for scanning the head in a direction intersecting the transport direction of the recording medium, and
A temperature detecting means for detecting at least the temperature of the platen and the temperature of the platen holding member, and
It is a liquid discharge method of the device having
The device
The platen is based on the set temperature of the platen, the ambient temperature before heating, and the time from when the temperature of the platen reaches the set temperature to when the temperature of the platen holding member reaches the set temperature. Derived the amount of thermal deformation of
Controlling the discharge of the liquid based on the amount of thermal deformation,
A liquid discharge method characterized by this. Platens that support recording media and
A platen holding member for holding the platen and
A heating means that heats the platen until the temperature reaches the set temperature, and
A head that ejects a liquid toward a recording medium supported by the platen to form an image, and
A moving means for scanning the head in a direction intersecting the transport direction of the recording medium, and
A temperature detecting means for detecting at least the temperature of the platen and the temperature of the platen holding member, and
A liquid discharge program executed by a device having
The platen is based on the set temperature of the platen, the ambient temperature before heating, and the time from when the temperature of the platen reaches the set temperature to when the temperature of the platen holding member reaches the set temperature. Derived the amount of thermal deformation of
Controlling the discharge of the liquid based on the amount of thermal deformation,
A liquid discharge program for the device to perform the process.

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